Balancing a V12 and Tyre Width

So, I've buily up my V12 circuit car - standard kit spec (rather then 'SuperDave' spec) and 1s LiPo.

On my kitchen scales it comes up at 890g, give or take a bit. Last time I checked up on details the minimum weight for this calss is 1000g. So I need to add 110g, no rocket science needed there.

However, having set the car up for ride height and rear pod droop I tried a balance test. I have drilled a dent in the middle of the underside of my chassis between the wishbones so, resting the front of the car over the edge of the workbench I lifted the front on the point of a knife to balance the chassis on the rear springs. The front right wheel (looking at the front of the chassis) lifted first, about 3mm before the left wheel came off the bench. The chassis was definitely tweaked!

Since I'm going to be racing this car on a circuit rather than oval, and therefore turning both left and right I am the thinking that an equally balanced chassis would be best. I tried altering the rear spring tension by tighting the opposite nut but I needed 6 full turns on it before the two wheels would lift together. Surely this cannot be good?

Next step was to move the motor to a more central position by adding wachers between the can and the rear pod. In total I could move it about 2mm closer to the centre before the sensor wire began to get crushed up against the other side of the pod. However, this movement now meant I 'only' had to add 4 turns to one rear spring to balance the chassis for the tweak test. Still not all that good in my eyes...

Since I need to add a load of weight I am guessing that adding this to one side of the chassis would be best? I tried with kitchen scale weights and some blu-tak (I have yet to buy proper sticky weights...) and 50g on the side of my LiPo got the chassis balanced side to side on the tweak test.

I've still got 60g to add though - should this go front or rear...?

When I raced 1/12 pan cars and WGT cars we tried desperately to balance the CoG of the cars in relation to the relative widths of the front and rear tyres - wider rear tyres meant having the CoG closer to the rear for 'perfect' balance. If the CoG was too far forward we got understeer into the corners and oversteer out, and if it was too close to the rear we got oversteer into the corners and understeer out of them. On the V12 chassis we have equal width front and rear tyres so I am guessing that the car's CoG should be equal distance bewteen the axels. However, mine is not - it is about 125mm back from the front axels. Mid point would be 102mm. Even adding all my remaining 60g in the front bumper would not move the CoG to the middle. Therefore should I cut the front tyres narrower to compensate for the reduced front weight?

So, my questions - for circuit racing is equal side to side weight balance important? If so, how important? How do you go about balancing your chassis and who balances front to rear or cuts front tyres narrower?

James

890g

Thats ready to race with the body and clips on and a transponder ?

its a long winded job to say whats what but if you like I can do a Video of mine with the weights etc but just to get you started look at this

Scroll down to Video's

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Hi Gazza,

Thanks for that link, very interesting reading and similar to the way we used to set up out WGT cars.

It seems though that my kitchen scales might be a little out. On the more accurate Science Lab scales at work the car comes in at 935g (with shell, clips but no transponder). I'm estimating another 15g for the transponder? So I'm guessing about 50g to add.

Should I still add that to one side of the chassis to try and offset the tweak as much as possible (and adjust the rest through rear spring tension), or should I add the weight centrally and balance the tweak through rear spring tension alone?

Is it worth cutting the front tyres narrower to compensate for the lighter front end?

James

Hi James

Right leave the tyres as they are . . .

What most have found out and even more so if running a Diff the weight is all on one side so like my self and a few others with some lead cut into strips and roll up so it fits into the opposite wheel block what I did was to cut a piece the same shape as the Block and then solder the rolled up lead to the flat one and then offer it up and bolt into place

Mine was around 40grams and ballanced the car up a treat

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The other way is to use a hole cutter and cut a piece of lead and bolt this to say a 50 spur gear and fit to the opposite wheel

Then as you say adjust the rest through rear spring tension and you will see that its a lot better ask Neil as I did his a few weeks ago and his car is now dialled as well

Adding weight to the pod actually has a detrimental effect on handing, as there is more weight to transfer.

I have tried this before on my brushed car. Using the principle of moments I calculated that I needed 41g on the outside of the pod. This made the car perfectly balanced with even spring tension.

But I then found that I had to run much stiffer springs to account for the extra weight the pod now had to transfer. If I ran soft rear springs (which I always run) and approximately 2mm of pod droop the car would just spin out as the chassis would scrub. By running stiffer springs, this accounted for the extra weight transfer side to side but changed how the car reacted when both springs were compressed at the same time (vertical chassis movement).

Long and short of it is... I wouldn't bother.

Karl

Well three of us run with this set up and we find it OK

yep improvved my car no end when i added the lead to the pod as gazza has pictured

each to there own i guess either way weight has to go on the car to make it run legal