Tyre pressure for racing on Toyo semi slicks?

Enzo:

Three matters:

1/ I finally decided to get the original 15" wheels - of you see something going on sale let me know!

2/ I have the fiat logo for you in a file any printer will need to put it on a plotter. give me your email address and I will send it to you.

3/ Re tyre pressure and temperature. Interesting link. My German is rough , but goon enough to understand the tet on the link you provided. Very interesting:

Also look at this : originally posted by Alan Meaker on a VX220 forum. Interesting ( note calculation into kg/cm2 -is s mine )

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

Cold   Hot
17 - 22 psi   22 - 29 psi
1.2 ? 1.55 kg/cm2   1.55 ? 2.04 kg/cm2

Light 800kg - 1000kg
Cold   Hot
20 - 26 psi   24 - 32 psi
1.41 ? 1.83 kg/cm2   1.69 ? 2.25 kg/cm2

Heavy 1000kg - 1400kg
Cold   Hot
23 - 27 psi   28 - 40 psi
1.32 ? 1.90 kg/cm2   1.97 ? 2.81 kg/cm2

Very Heavy > 1400kg
Cold   Hot
27 - 35 psi   37 - 40 psi
1.90 ? 2.46 kg/cm2   2.60 ? 2.81 kg/cm2

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

Achieving the required tread temperatures will depend again on the conditions on the day i.e. ambient and track temperature, wet or dry.

You often here competitors saying ?My tyres started to go of towards the end of the race?, this is usually due to the tread getting to hot.

The tread temperatures are constantly changing through out a race, hotter when cornering and cooler when on the straights and cooling even more when you are slowing to come into the pits. Therefore the temps you record in the pits will be lower than those during the race. So if you record temperatures within the range given above the probability is the temps will be too high during the race.

Increasing your tyre pressures will cause your tread temperatures to increase, more pressure stiffens the tyre?s casing which results in the tread having to do more work resulting in the tread getting hotter. Lowering your pressures will cause them to decrease.

Inevitably changing one thing will affect other things, the whole set up of your car is a compromise between anything that is adjustable.

Some of you are also asking about different compounds. Originally we only had one compound ?GG? (medium hard), but we have now introduced some sizes in a ?SG? (soft/wet) compound. This was done primarily for sprint/hillclimb (around 60 second runs) where the distances covered are relatively short and you need the tyres to work/heat up very quickly. This is not a compound I would recommend for race/trackday dry use as the tyres will go off very quickly.

The sizes that will be available are:

185/60R13, 205/60R13, 195/50R15, 205/50R15, 225/45R16, 225/45R17.

Another subject is the introduction of our Proxes R1R. This tyre was due to be launched at the beginning of 2008, unfortunately this has been delayed to at least mid 2008 but there is a good chance it will be latter than this. Regarding sizes, initially we will have a rear fit (225/45ZR17) but not the front (195/50R16).

I hope this is of some use to you.

If I can be of any further assistance please give me a call.

01933 414537

Best Regards

Also this originally posted on GCRE forum is very interesting :

TIRE PRESSURE RECOMMENDATIONS !

by mtbr on Fri May 29, 2009 1:05 am

Hi Miro,
We call your event "sprinting" I have a friend who is very successful at this type of event. He suggests B list* tires like the Toyo 888R are typically worth 4 sec per minute over good A list tires.

*The UK MSA have two lists of tire brands and types, list A and B, which are broadly "genuine road tires" and "road legal track tires".

With the short runs, you can get quite a lot of variance in your data because individual driving errors have a greater effect on the overall result. Sometimes it is better to work from the tire wear. The tire never reaches a stable hot working temp during the run, so you aim to be slightly under inflated at the start, about perfect in the middle and slightly over inflated at the end of the run. There are all sorts of fancy tread depth gauges, however good results can be obtained using a simple set of vernier calipers (carefully.) Measure tread depths at 3 points across the tread width and at 4 points around the circumference of the tire. MEASURE TO THE WEAR MARKERS, NOT THE BOTTOM OF THE RAIN GROOVES.

Provided the wear is reasonably even across the working area of the tread then you are close to the correct pressures. One important point to note is that there are small triangles on the outer sidewall of 888s and other tires. The tires must be inflated so that the wear does not go beyond the tips of the triangles. i.e. if the tire is under inflated it will deform enough that the car will roll the tire under the wheel and wear the sidewall on the road surface.

By measuring tread depths, before and after an event, you can check how well the tires were inflated and also how much tread was used. Keep a note of the number of heat cycles on each tire as well and then you will be better able to assess when to relegate a set of tires from competition to practice.

Miro

PS: here are some pictures from Tychy !

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