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General Car Setup Discussion

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Would like to ask the 2 following questions in regards of tyres.

When changing tyre size for example a 185/55/15 to a 195/50/15 or a 205/50/15 (could be also 16/17" etc) how would choose a tyre base pressure to start from . Would you again go from factory specification ?

2nd question in fwd car would having wider tyres at the front get more grip than having same size tyres all around ? Similar to what some powerful rwd vehicles have .

Both my questions are referring to gain max grip either uphill/downhill racing or circuit

Thank you

Hi Andreas

Yeh, great question. So for these situations where you have a lot of tread, my suggestion would be to still take 3 readings, inside, middle, outside and to take these measurements from the tread blocks. Make sure that you have the tire probe (if you're using one) inserted all the way in, at a 45 degree angle. The next thing I would suggest is once you have your 3 measurements, spin the tire and take the same 3 measurements at a different part of the wheel. It would probably be best to take these at 3 or 4 different spots around the tire and then take an average.

I know this might be a bit more time consuming, but it should help get rid of any anomalies you might be finding.


RaceCraft Team

In answer to your 2nd question... For your pressures, I would say go for the manufacturers advice, if possible run a couple laps/run a stage, then come into the pits and check your pressures straight away, you want to look for pressures that are equal on all 4 tires (assuming each tire is the same size). Usually the manufacturer will be the most knowledgeable on this subject, all tires are different, all tires run at different optimal temps.

For fwd cars, yes you're correct in thinking that wider tires on the front will give you better grip, but why wouldn't you also want to run the same size tires on the back? The idea here is simply, the wider the tire, the better the grip. This will however not be the same case for something like Snow driving or very wet conditions where a wider tire will have a tendency to glide across the surface of the road, instead of cutting into it. You've probably noticed in WRC, during the snow rounds, their tires are very thin.


Thank you Matt for the reply . I was asking in running a different size front to rear due to Facebook post from a company for a dimension less number which is the result of dividing the corner weight with the section width . They state that having the same size front and rear increases that number compared to having different sizes front and rear .

Also should the right approx be finding the correct camber/caster height extend then tire pressure ? Cause with a different alignment we might find another pressure more suitable for us to my understanding . I understand it's time consuming but I am ok with that

No worries

Yes, whenever you make a change to the alignment (camber, caster, etc) you are affecting how the tire scrubs the road. Your pressures will go up and down at different rates. Like I mentioned before, when you come into the pits, try to balance your tire pressures across all the tires.


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