Getting technical - a guide to drift car setup

The following was text originally written by myself for the benefit of helping getting Drift RC magazine (a US mag) off the ground a couple of years ago but nothing significant has changed since then. Some of the photos intentionally show older tub chassis as these are still popular at club level and can work well in drifting. It looks at the the RC Drift Car chassis in all its glory and tries to explain, hopefully in words we can all understand, what's going on when we take it for a run and, with that understanding, how to set it up so that we can better control it - the secret to winning! Enjoy.....

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GETTING TECHNICAL

We all know how much fun drifting is. We all know how terribly dull technical stuff is. Yet here I am, attempting to throw lots of technical stuff at you! Well, with a bit of technical know how I can promise you your drifting ability will improve and, as it does, I also promise you that you’ll have even more fun. Yep, it’s a promise, more fun!

Through this 'How To' style manual, we will take a look at a different technical aspects of RC Drifting, initially setting up your drift car. Some things you may already be familiar with, some maybe not, but armed with a comprehensive knowledge of all the things you need to know to make your car handles better, your car will do what you want it to, allowing you to focus on drifting more skilfully. Remember that when setting up your chassis, all components should be fitted so that the full weight and balance will be just as it is when on the track. Don't forget the battery pack, although the body shell will have to sit and watch!

Ride Height
Firstly we are going to look at Ride Height, which may at first seem a bit basic, but beware. There are right and wrong ways to achieve a different ride height so please read on. I should at first explain that when an adjustment is made to a car, any adjustment, all other adjustments are impacted so will need revisiting. This is because the suspension and steering geometry is changed slightly when you change just one element. Because of this, when you are setting up a car, there is an order you need to follow so that subsequent settings do not impact those you have just done. The order you should use is:-

- Ride Height
- Tweak
- Caster
- Camber (Front/Rear)
- Centre Steering
- Toe (Front/Rear)

We do the ride height first because when the ride height is changed, even to just one corner of your chassis, the geometry of all the corners is changed. If you doubt this, put your chassis on a flat surface and depress it – any place will do – while looking at the front wheels from the front of the car. As the suspension depresses or rises the normally unequal length top and bottom suspension links rise in different arcs and the camber of you wheels can be seen to tip in or out. Now look from above the front wheels and do this again. The front wheels may turn in or out slightly. Remember what you’ve just seen as this is what is happening to your chassis as it runs around a corner or over a bump! As you develop your understanding of chassis dynamics you’ll better understand how to tune your car. Anyway, for now, we’ll start with the least exciting but most important initial setting – ride height.

I’ll assume that your car has a flat bottom, whether it be of tub or twin deck design, as all reasonably modern designs fit into one or the other category. The ride height of your car is the distance between the flat surface it is sitting on and the bottom of the chassis. This may vary from front to back, side to side, corner to corner, but in general we want to get it to the same measurement all around. To make an accurate measurement we will need two pieces of equipment, a flat surface and a measuring device.

Because we want to do checks whilst at the track, we need a portable flat surface, such as a purpose made set-up board or a suitable sheet of toughened glass. Personally, I find a glass cutting board best as it’s very cheap to purchase and available from any general store or cook shop. A glass board is very flat and, providing you take care not to drop it, will last forever. It will also be needed to carry out all the other setting up procedures so it’s a good investment. The measuring device is best purchased from your local hobby, a purpose made tapered ‘wedge’ with height graduations that can be slid under the chassis until it touches the bottom and the height measurement can be read off. These are also sometimes supplied with car kits.

Setting ride height with a twin deck chassis
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Firstly, just check that all the wheels are pointing more or less straight forward. Place the chassis on the setup board with the battery fitted but without the shell. Now remove any spring pre-load clips or wind out any pre-load on the shock absorber spring adjusters. You need to get the springs adjusted so there’s no slack but no compression either when the car is off the ground. Now, placing one finger in the centre of the front and rear shock towers, fully push down the chassis and then release it so that it rises to it’s natural running height. Now place the height measuring wedge on the flat surface and gently slide it under the chassis until it touches. Do this at all four corners and note the height readings.

Setting ride height with a tub chassis
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We want to set the chassis so that it is not too high because the lower it is, the more stable it will be, say 5-8mm, 5mm for indoor use rising to 8mm if being used outdoors on a slightly rougher surface. We also want the chassis to be able to rise at each corner, say 2-3mm so that the wheels remain in contact with the track when another corner is lifted, for example, as you run over a low kerb, and we want the chassis to be able to compress to about 1-2mm above the surface to absorb the bumps without bottoming out.

With the chassis sat on the set up board, can you use alternate shock absorber mounting points to get the height wanted? If so, try this method first – though we may want to revisit mounting points at a later date as shock angle impacts handling too! If you can’t find a suitable mounting point, you can use alternate springs that are of a better length or increase the ride height by adding pre-load using the adjuster collar / pre-load clips (depending on what’s supplied with your shocks) to lift the corner. By adding spring pre-load the spring compression rate will be changed slightly, something to be considered, so try to use the method that has the least pre-load effect. Once the individual heights have been achieved, recheck the corners you did first – remember, change any one setting and others change too!

Droop
Okay, we’ve now set the ride height but we’ve yet to set the amount the corner can lift (droop setting) and the bump stop. If your chassis has droop screw adjustment then just adjust the screw until you can lift the corner around 3mm before the tyre leaves the surface. If you don’t have this facility, you need to add small rubber o-rings inside the shocks, positioned below the piston, to adjust the downwards travel of the shock and, therefore, the travel of the wheel as the chassis is lifted.

Measuring droop using a droop gauge and associated blocks
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Measuring droop using a ride height gauge, top with chassis at normal settled height and bottom, with chassis lifted to point at which the tyres begin to leave the surface
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If your chassis doesn’t have droop adjusters, do this! Typical shock absorber components, here with droop adjustment o-ring(s) fitted. This acts to reduce extension.
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Next we want to adjust the downwards travel of the chassis. We don’t want the chassis to hit the track because, not only will it damage that expensive carbon fibre, but it will also cause a sudden change in the chassis dynamics when it hits the ground, unloading the suspension in the process, which unsettles the handling. The easiest way to limit the downwards travel is to fit rubber o-rings to the lower (outside) length of the shock absorber shaft, between the shock body and the lower spring retainer. If you need more than 2 o-rings, consider cutting a short length of silicon fuel tubing and sliding that over the shaft. You want to limit the travel so that the chassis stops just 1-2mm above the setup board surface. The soft o-rings or tubing will give a progressive stop and will cause the load to remain on the suspension instead of transferring to the unsprung (at the point of impact) chassis.

Shock absorber with bump stop o-ring(s) in place before fitting spring and spring retainer. This acts to reduce compression
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Okay, we’ve set the ride height, the minimum height and the droop. Already you might feel a positive change in the handling and with the suspension travel limited to that which is actually needed and no more, you’ll also be able to more precisely adjust your body shell ride height. Now here's a very useful tip on body shells.

Nothing looks more uncool than a body shell that’s mounted too high but, at the same time, one that looks cool but rubs on the track can cause all sorts of handling problems so set the bottom of your shell the same height as the chassis – fit and trim it before painting – and then fit the body clips at least two holes higher than the body shell surface. Yes, I know this means that the unsightly posts will have to be two holes longer but by doing so the shell will be able to simply float upwards on the posts if you should clip an apex kerb with the front splitter. Far better this than your car be dragged into a spin and a zero score!

Tweak
Tweak is a word used in RC that sort of covers a multitude, well couple, of sins! Drivers will often refer to chassis twist as tweak. This can happen when a car is not checked on a flat surface when built or when it takes a knock in competition and is twisted out of alignment. Resolve this by slackening the main top/bottom deck screws, place on a flat setup board and retighten. Top race drivers often race with screws removed or slackened that club drivers wouldn't dream of touching! And win by the way!

Tweak stations however normally deal with tweak a little differently. They assume that the driver has checked the chassis for twist before the station is used. The tweak station consists of a rear platform to sit one axle's tyres on, usually the rear but it could be either. This is leveled by use of a built in spirit level and adjustable feet. The platform is calibrated to ensure that the axle/chassis is centred. The front platform, for the other axle, is balance rather like an old style set of scales, again with a built in spirit level. When the second axle's tyres are lowered onto it, it will dip either right or left, indicating that more pressure is being applied by the tyre on that side. This could be caused by either weight and/or chassis twist and/or unequally set suspension.

A chassis positioned on a dedicated tweak station. The board and rear support has been leveled. The spirit level is mounted in the front support
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The beauty of the tweak station is that is takes account of all three possibilities. The downside is that it doesn't tell you which is at fault - that's for you to check! However, on the track what is important is that the pressure applied by each left and right tyre on the same axle should be the same so by making adjustments using ballast, spring preload etc you can see when you've got it right as the front platform becomes level with the rear, as checked by the spirit levels.

Sounds a bit long winded, and it sometimes is, but it's worth the effort and can often remove the problem of a car favouring left or right corners!

Well known products include the Hudy product which has a front balance platform at one end of a calibrated setup board. It is necessary to ensure that the whole board is first perfectly horizontal. Other dedicated devices exist, as below.

So having digested our comprehensive look at the not so simple topic of ride height, droop and tweak, we now need to take a look at the topical question of caster (aka castor) and camber. We all like that squat, splayed out look that lots of negative camber gives, but does it help us to drift well? Let’s see!

Camber
Although when setting up your chassis you should check the caster before the camber, I’ll deal with camber first as once that’s understood, caster becomes easier to understand. Camber is the way the top of the wheel and tyre leans in or out of the wheel arch when the wheels are pointing forwards. It is measured in degrees from the vertical, and is measured as negative if the top of the wheel is leaning into the wheel arch and positive if leaning outward. In racing and drifting we always use negative camber, typically from 0-2 degrees. But why?

It’s not just for aggressive looks! I’ll start by illustrating what is going on as you corner on soft rubber race tyres or, to a degree, hard radials or foam and then move on to drift tyres. You’ll need your car to hand as you read on.

We want to give the car as much mechanical grip as possible and this is done by maximising the tyre contact patch – ie, we want the flat part of the tyre tread area to be flat against the track surface. At first you’d assume the easiest way to do that would be to set the camber to zero degrees and have the wheels vertical but as the car corners the tyre is forced by the cornering forces to roll sideways across the wheel rim and, as it does, the inside tread area lifts slightly. To overcome this, if you set the camber to, say, 1 degree and then watch as the car leans into the corner you can see how the outside tyre rolls on the rim so that the tyre squishes down flat onto the track. Not easy to see as the car passes you at over 15mph so just lay the car on a flat surface and push it sideways as you watch the tyres flex. How much negative camber you’ll need depends on the circuit, how fast the corners are, how tight the corners are and how much grip the surface is providing. You may have noticed that this setting up procedure only deals with the tyre that’s on the outside of the bend but that’s okay as the inside tyres are doing very little work whilst cornering.

Cornering forces mess with your setup!
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To compound matters, if you look at the front or rear suspension on most chassis you’ll be able to see that the top suspension link is shorter than the lower ‘wishbone’ suspension arm, which is intentional. Both pivot up and down as the car runs over humps, bumps and as the car leans in corners. Because the top arm is shorter, it describes a shorter arc than the lower arm – just push your car fully down and you’ll see that the top of the wheels move inwards as the car drops. As the wheels move inwards, however slightly, the negative camber angle increases.

Differing length arms give more camber as the chassis is depressed
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As you corner the outside of the chassis depresses as it leans, increasing the camber so compensating for the reduction in camber caused by the lean angle itself. Try this on your chassis as it sits on that flat surface – push it sideways and lean the chassis over slightly, as it would in a corner and you’ll see what I mean. I said above that the differing length suspension arms were intentional and this is why.

Setting camber by adjusting the length of the top links
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Caster
I’ll now broach the subject of caster and then review the whole as it all applies to drift tyres. Caster is the angle from the vertical of the imaginary line drawn between the top and bottom kin pins of the steering – that’s the two bolts that hold the steering knuckle in the C-hub. The caster normally varies from 0-6 degrees but may be more on off-road vehicles. For drifting, try 2-4 degrees. This will either be set by the selection of the appropriate C-hub or by adjusting the position of the top link where it is a movable wishbone type. Be warned that where your chassis has vertically adjustable bottom wishbone pivot shaft mounts, you can further adjust the caster angle when setting, for example, anti-dive settings. So that’s how it’s adjusted and set, but why do we use it?

Measuring castor angle. More caster gives more camber when turning
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Back to your chassis on it’s flat surface, and it would help if you put your basic geometry hat on! As you turn the steering, normally limited to around 25 degrees of turn, the camber on the outside wheel is partly lost. If you could turn your steering through 90 degrees (right angles) the camber effect would be geometrically lost completely. At the same time, at the same 90 degrees of steering, the 4 degrees caster angle (if you has selected 4) would now cause the wheel to lean over at 4 degrees of negative camber. In normal operation, with just about 25 degrees of steering, the one degree of desired camber would be maintained throughout the steering arc.

What this all means is that, whatever the chassis is doing as you drive through a corner, the camber angle you’ve set remains more or less constant. Getting it just right is a matter of trial and error so do experiment with different angles but don’t go too wild!

Applying Camber/Caster to different drift tyre types
Now, drift tyres. As we all know, most popular drift tyres for electric powered chassis are of a hard, non-pliable nature being of either a ABS or Poly type plastic. This means that the tyres do not tend to roll on the rim like a rubber race tyre, making our setting up process a little easier. What we need to do, then, is adjust the camber and caster so that we maintain a maximum contact patch so, for a parallel tyre such as ABS pipe, zero camber is our aim.

Tyre and camber variations – horses for courses!
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Yokomos popular Zero One tyres use an ABS type plastic ring or ‘collar’ but these are held in place by hard rubber side walls. As soon as the rings wear down a little, these rubber side walls start to play an important roll as they give useful grip when inducing a transition. By using around 1 degree of camber but 4-6 degrees of caster, you will be able to use the inside sidewall of the outside tyre as you briefly turn in to a corner and then return to the plastic ring as you drift around the corner on neutral steering. These tyres can be very finely tuned to individual circuits or driver tastes.

The moulded ‘poly’ based tyres all seem to be slightly domed across the tyre tread surface and need to be ‘run in’ until the tread surface is fairly flat. Because of this, you can set the camber more or less as you prefer visually as the tyre will wear a flat surface regardless. However, its important to measure and then retain the camber the tyre was run in at if it is to remain at the optimum angle.

In order to accurately measure camber you will need to buy a camber setup tool from your R/C store. These come in various forms but the more elaborate, and more expensive Hudy style setup gauges are best as they also measure caster, toe, steering angles etc., which conveniently brings us to the last elements of chassis setup, Front and Rear Toe and Steering setting.

Steering and Toe setting
It is essential to correctly centre your steering and balance your steering throw so that your car drives in the direction you expect it to. To centre the steering you need first to centre your servo. Set your transmitter steering sub-trim to zero. Now fit the servo horn so that the steering rod that attaches to it is as near to a right angle to the horn as possible (not necessarily horizontal). Now use the sub-trim adjustment to get that right angle to exactly 90 degrees and save the setting. You can now adjust any remaining steering linkages so that they sit central to the chassis centre line. This now just leaves the left and right steering turnbuckles which we'll adjust as we set the front toe.

Toe is the measure, in degrees, that the front and rear wheels point in or outwards when view from above and behind the chassis. A rear wheel that points slightly inwards, for example, would be described as having toe in. Toe affects the car's handling significantly so needs to be right but what the 'right' setting are must be found from track testing, although a rough guide will serve as a good start point. In general, rear toe in will make the drift chassis more stable in a straight line and will make the rear end less fidgety in the drift. This calming affect will make the car easier to drive. Try 2-3 degrees rear toe in as a start point. Front toe adjustment is slightly less significant in a drift car so, using a suitable measuring tool, start with a setting of zero toe.

Setting toe using a Hudy style setup station
Front toe is adjusted by shortening or lengthening the steering turnbuckles after the steering is first centered. Rear toe is adjusted by changing the rear hub or lower, inner pivot plates/mountings, depending on the chassis design used. Your chassis build manual will advise on which method(s) to use for your model.

Once the steering has been centred and toe has been set, we just need to check that the steering swing is the same, left and right. This is most easily done using the same Hudy style setup tool that was used to set the toe. Use the transmitter's steering End Point Adjustment (EPA) to equalise the left and right throw, ensuring that the steering doesn't throw so far as to foul the C-Hub and cause damage to the servo motor. Most chassis will provide a maximum throw of around 20 - 25 degrees.

Shock absorber angles and mounting points
Earlier in this article I promised to take a look at the impact of using different shock mounting points to adjust your ride height but, more importantly, the mounting points used and the angle of the shock also impacts the way it performs. It's time to go back to school and those dreaded physics lessons! Consider the situation yourself - the shock spring and the resistance offered by the oil are the constant resistance that has to be overcome, whatever the angle. That means that there are two variables remaining, 1/ the distance the piston travels when you ride a bump and 2/ the leverage applied to that movement, the inner hinge pin of the lower wishbone being the pivot, the tyre contact patch being the end of the lever and the lower shock pickup point being the distance from the pivot. If you get a physics book out of the library and look up 'moments' it will all be explained!

You don't need absolute figures to calculate the difference that the positions of the shock mounting points make, just percentages of X. Three fundamentals apply. 1/ An upright shock will compress more than a laid down one given the same lower wishbone travel. 2/ An inboard mounted shock will compress less than an outboard mounted shock given the same lower wishbone travel. 3/ An inboard mounted shock will experience greater leverage than an outboard mounted shock given the same lower wishbone travel.

So, if you apply this information to either increase or reduce the resistance to movement you can stiffen or soften the suspension without changing the springs or oil, or just use it as another variable to combine with changing the springs and oil. Given that in drifting we are always looking to increase grip so that we can control the car despite the very low grip offered by our drift tyres, a softer set-up will help us.

This completes the the chassis set-up check procedure that should be completed after a chassis new build or maintenance re-build, before each outing and, in competition, before each run - or as much as you can complete - if short of time, at least check the camber hasn't changed. It's a point worth mentioning. Most chassis will self adjust when in use, some more than others, so regular checks do need to be made. If the diff is changed, then the shock tower will be removed and that can change the position of the top suspension arm when it's refitted, and thus, the camber! Changing differentials - now there's an interesting topic.....

Differentials - types and choosing the right one!
The selection of the correct differentials for a given car, circuit and conditions is as important as any other chassis variable, maybe more so. We have several types of differential to choose from, the planetary gear diff, the ball diff, the one-way diff and the spool or locked diff. Additionally, some chassis give you the option of a locked or one-way centre drive pulley.

I’ll start with the rear differential first as this is by far the easiest end to deal with! We want both the rear wheels to continue to spin faster than the surface we’re drifting on so that the drift is maintained. We also want the wheels spinning at the same speed as each other to avoid any rear steering effect so a spool is the perfect and, in my opinion, only solution. If you don’t own a spool then try locking a ball or planetary diff (there are plenty of tutorials on this) until you can afford to buy one. The good news is that, being the simplest to manufacture, they are also the cheapest type to buy. Some drivers use an over tightened ball diff in the rear but this often leads to early failure of the diff and still doesn’t give the same stable drift that the spool does.

Choosing the front diff is somewhat more complex and you really do need to consider your personal driving style and skills as well as the track you are competing on. I’ll begin by explaining how each type of diff operates.

The simplest is the spool, a fixed axle with no differential affect at all. Since we are seeking to get good steering from our front end, despite the drift tyres trying to understeer, the spool doesn’t help us in the all important area of turn in and, because of this, we can discount it’s use for front end.
Moving on, the planetary (gear) diff that is supplied with some budget kits is far too free moving for drift use but this can be improved with the use of very heavy diff grease provided it is packed very tightly. This grease is a specialist one that can be purchased from good RC shops that support 1/8th or larger scale off road racing where this sort of diff is used extensively. With very heavy grease, the geared diff can offer similar limited slip performance to the ball diff.

The ball diff is made up of two halves that are separated by two plates between which small ball bearings are located allowing the plates to move in the same or different directions and at differing speeds, providing a differential effect. A central tensioning bolt allows adjustment so that the two plates can revolve either freely or be almost locked together (but never fully). The mechanism must be kept spotlessly clean and greased. Some are sealed. Use in a medium to tight adjustment, the ball diff can be used very effectively in the front of the car, not least because it provides front wheel, and thus four wheel, braking.

The one-way diff consists of a central driven part with outdrives on either side that are coupled by one-way bearings, both operating in the same direction. A one way bearing grips the drive shaft when rotated in one direction and releases the shaft when it is turned in the other direction. When fitted to a car, the bearings both grip the drive cup shafts when the centre of the diff is driven by the motor and release the shafts when the power is backed off and the wheels turn quicker than the centre part of the diff (be it belt pulley or shaft crown wheel).

A heavily greased geared diff and a ball diff both allow some differential effect and so aid turn in and since the drive train is always connected to both wheels at all times, these diffs also provide both motor braking and electronic braking to operate. A one-way diff under power locks up just like a spool so provides 100% drive to both front wheels under power but when the power is reduced or brakes applied, the one way bearings allow the front wheels to rotate freely, normally at the speed of travel over the surface, providing maximum front grip and turn in. As the power is re-applied the drive to both wheels is locked again. Front one-ways give very fast turn in and take some getting used to but do offer some advantages over ball diffs in certain circumstances, for example on big flowing circuits where little braking is required or where long connecting straights need to be driven using long, straight drifts, achieved under power or off power by counter steering so that the front wheels simply rotate in the direction of travel, offering no brake effect.

A double one-way, a front one-way diff and a centre one-way doesn't really perform any differently from a front one-way and fixed centre pulley. However, a ball diff or spool front with a centre one way does as it removes the front axle brake but retains some of the the ball or spool characteristics, both resisting turn in to some degree. On power, a single or double one-way will perform exactly the same as a spool front, providing lots of forward traction but incurring some understeer so it is best to wait until you complete the corner drift before hitting the throttle unless you have plenty of angle on. A centre one-way and front ball diff provides a little less drive but slightly more steering. The torque is distributed evenly between the two sides even with the turn circumference differential that exists. Given that the wheels will most likely be spinning at the time you would expect most of the torque to escape from the inside wheel as that one will have less weight and will spin up first but due to the ball diff giving a slight LSD effect the outside wheel will still see some of that torque.

A front one-way diff is slightly different as it only deals with the differential effect by allowing one or both sides to free wheel faster than the main pulley when off power. i.e. if the car was gripping, the inside wheel would spin at the same speed as the diff itself and the outside wheel would free wheel faster. Does that mean that all the torque is put down through the inside wheel only when the power is applied? If so what happens when you start spinning the wheels? Since both sides will spin at the same speed, do you get more wheel spin from the inside wheel?

To answer these questions, it is easier to consider first the car to be on grip tyres and pull on racing experience, then adapt this experience to drifting. Whenever the power is on, all your driven wheels will be spinning. In other words, a one-way front becomes a spool under power where both front wheels will be spinning at the same speed as the diff, and somewhat faster than the forward speed you are travelling! It's actually the same with grip tyres because on full power both front tyres, even soft, grippy CS22's, will be scrabbling for grip and the difference in the turn circumference will be overridden by the slippage.

Now, a centre one-way with a ball front. Under power, the one-way locks and you have the same characteristics as a ball diff front and locked centre. Here you will have some spinning up on the inside wheel but because the loaded tyre, the outside one, has such low traction (due to the tyres we use) again the diff doesn't really favour any one side as much as it would with grip tyres, racing. What's more, because of the low grip, the cornering forces are relatively low so the difference in load on each front wheel is very small anyway. Just keep the diff fairly tight and the low differential forces from the tyres will give you almost spool characteristics.

Now, under braking, it gets far more interesting! I'll just throw in that if your one way bearings are working efficiently, having a centre and front one-way will make no difference to just a front one way. Power it drives, off power it free wheels!

It's always been a known thing that running a spool or one way in racing is best under high grip situations, which is exactly what we don't have, but that's because of the tendency of the back to snap out as the power comes off due to the engine breaking from the brushed can or programmed drag breaking with a brushless, and even more so when the brakes are applied. Racers don't want any drift angle as it slows their progress (you might not think this if you watch Top Gear but none of that lot can drive!) but we do want drift angle so our needs are different from the racers.

Under braking or off power, on a front one way diff, the diff itself is either not turning or turning at a lower speed than the wheels. As the car turns in both wheels are free to turn as fast as they want to. This means there is no resistance to the outside wheel turning as fast as they want to and therefore the car should be able to turn in faster. With a center one-way, the front diff again has no braking force applied to it but the two front wheels are trying to turn at the same speed. A totally open or greaseless gear diff would give a similar effect to the front one way diff but, with a ball diff, there is resistance to the wheels turning at different speeds. This reduces the turning input of the driver of the car as the wheels want to turn at similar speed and thus reduces turn in. The tighter the ball diff, the less turn in you get.

In Conclusion, The front one way diff should give a more snappy turn in effect whilst a centre one-way and ball front will still have a snappy turn in effect due to the braking only being at the rear, but not as much, hence why people tend to find that the front one way diff is more "twichy" than the center one-way. Because the front wheels can spin at the speed of the road, unhindered, the front one-way offers no resistance to the back as it tries to come around. This is why most drifters give up trying to drive with a one-way (a mistake, but more later?). A tight ball diff tries to keep both front wheels turning together so, when the rear starts to break away under power off or braking, the front wheels try to resist it. In reality, the difference is really small because whilst the wheels try to resist the turning motion, the low grip tyres struggle to assist! Also, because the car is moving forward that speed differential between the left and right wheel, when expressed as percentage of the rolling speed, is very small so has very little impact.

The big factor here is where the loadings are occurring. Without a front / centre one way, when you come off power or brakes all four wheels try to stop the car and this throws the weight forward, taking load off the rear tyres and onto the front. With grip tyres this is good, but with low grip this causes the front to understeer (push) as you turn in so that the speed of the turn in is reduced and the rear, no longer trying to do all the breaking, maintains a modicum of grip and doesn't snap out like it does with the one-way setup.

This makes quite a big difference to how you initiate a drift. With a tight ball front, the normal method is to turn in and punch the throttle. Both actions are only momentary to break rear grip in the direction you want to turn. You them immediately return the steering to the centre and, with the drift initiated, balance it on the throttle.

With a one-way the drift can be initiated differently. Firstly, you can use exactly the same technique as above and it works because you don't come off the power, so it's the same dynamics playing their parts. However, with a one-way, you can also initiate off power, twitching the steering in the direction you want to turn then just feathering the throttle to balance the drift until the car virtually stops! Try this with a ball diff and you just get massive understeer - straight off the circuit! This second option that the one-way gives allows you to slide over very long distances in a straight line, countersteering as you go, as no forward drive is being used that would otherwise pull the car in a curve. This is great when you have a very long, straight section or long, shallow curve that needs lots of speed but brakes into a tight hairpin - you can hold that straight drift while the speed bleeds off without actually curving much. Think Snetterton sweeper into the hairpin or that dreaded Colchester configuration where you drift towards the rostrum (long straight section into the hairpin?).


TO BE CONTINUED......

Any questions relating to the above topics, ask away. Other topics will follow.

Well what can i say JT that write up was stuning i have took so much info in my brain is going to go bang the guys will love that thank you so much mate it will help guys like me get setting up dead right
I notice you are from the deep shouth Essex area a place i spend a lot of time in Pitsea to be honest as im married to a essex girl what more could i wish for

Not a million miles away, South Woodham Ferrers so nearer Chelmsford. There's now't wrong with Essex girls. You just have to take care when dating the feral ones.

Glad the tedious stuff helped. It's already a little dated but the technical considerations haven't much changed, just the equipment we use. We're still trying to find the ideal weight though, we know it should be 50/50% left/right and front/rear but is lighter better than heavier? Since we don't have a min/max limit, drivers are free to ballast as they please. There is however general consensus that there is an ideal happy medium. There is no consensus as to what it is

Wow what a write up John just read the whole thing and my head is swimming.

I have an old M1-Xpress TC that im trying to convert to a drifter and know now i have quite a bit of work to do to make it do what i want it to do, i think the first thing ill be doing is try and get hold of some supper soft springs because that's one thing i defiantly don't have in the spares box as i don't think ive ever had a need for super soft springs, rear spool will be next and then see how i go before i start looking at front one ways and things like that.

Meeting up with Tom this weekend to have a bit of a demo and get him to look over the car see what he thinks needs to be done.

Cracking informative write up.......

Marti