Featured Sylva Star

[adithorp]

36psi is way too much. I'm supprised you have any fillings left at that.

[RedStar]

36PSI this is the reason for me asking (I had an idea your pressures might be high - but not that high).

found this on Locostbuilders forum after a quick Googling.

My name is Alan Meaker, I am the Motorsport Manager for Toyo Tyres (UK) Ltd.

I was at Rockingham on the Saturday 1ST March at the LOT trackday and worked with a couple of cars using our R888 tyre regarding pressures and tread temperatures.

What I would like to do is to offer some advice on tyre temperatures and pressures and how to achieve the best from our tyres when taking part in either trackdays or racing.

The R888 has a semi race construction (very stiff) and a race tread compound. The optimum tread temperature range is between 85C and 95C measured using a probe type pyrometer, and ideally a maximum difference across the tread of 9C. The maximum hot pressure we recommend is 40psi. Camber angles up to 5 degrees are permissible but the final setting will depend on tread temperatures. It is advisable to have as much positive castor as practical as castor induces a beneficial camber change during cornering. I recommend that the tyres be put through 2 heat cycles before hard use.


The pressures you use will initially depend on the weight of the car, too little pressure on a heavy car can lead to over deflection of the tyre and subsequent failure.

Below are some basic settings:

VEHICLE WEIGHT COLD PRESSURE HOT PRESSURE
Very Light < 800kg 17 - 22 psi 22 - 29 psi
Light 800kg - 1000kg 20 - 26 psi 24 - 32 psi
Heavy 1000kg - 1400kg 23 - 27 psi 28 - 40 psi
Very Heavy > 1400kg 27 - 35 psi 37 - 40 psi


As a tyre gets hotter the pressure increases, this is due to the moisture in the air. The cold pressure you set to achieve a desired hot pressure will depend on the conditions on the day i.e. ambient and track temperature, wet or dry. If the day/track is cold you will need to start with a higher cold pressure as the tyre will not get as hot therefore the pressure increase will not be so great.
Hot pressures must be balanced side to side. Once the tyres have cooled you will find that you will have a difference in pressure side to side, if you have been racing on a right hand track you will find the offside pressures will usually be higher than the nearside.


Changing hot inflation pressures by small amounts can be used to fine tune handling.

Reduce Oversteer Reduce rear pressures or increase front pressures
Increase Oversteer Increase rear pressures or reduce front pressures
Reduce Understeer Reduce front pressures or increase rear pressures
Increase Understeer Increase front pressures or reduce rear pressures

drop your tyre pressures, give it a go and let us(me) know the results.

[mgh369]

Thanks for the tyre pressure advice wish there was a manual? Will try a lot lower pressure and see what a difference it makes. Must say I have not found the ride too bad but the front does tend to jump over bumps may be the high pressures is why! Will try 20 and work my way up in 2 psi increments. Thanks Mark

[mgh369]

Spent a few hours experimenting. On checking pressures I had 30 psi all round not 36. Dropped this to 20 psi all round (cold) could feel the difference in a softer ride but fronts too soft feeling the tyres roll under hard cornering. Several changes later I'm happy with 24 front 21 rear (hot). Will keep trying different combos and my cheapo tyres wont help but thanks for the guidance.

[RedStar]

sounds like an improvement....

next thing to check (maybe) is the suspension geometry/alignment - maybe something is out?