Pressures!

We heard it many times that we should always pay attention
to our tyres, as it is the only contacts we have with the road
while we're driving.
So, it's a safety aspect.
However, if we are speaking in motorsports terms it is
Performance. It is Handling.

There are many different brands of tyres, with each brand
there are either Hard, Medium and Soft compound.
That's not including the wet tyres on the shelves.
Whatever brand, compound, type of tyre you had chosen
to run with there's a common denominator to it.

Tyre Pressure.

How much to pump? How to make adjustments so that
the handling is sweeter?

I reckon this is true for kart or car or bike, so I hope this
useful to more than to only karters


Lets now take a look at some examples of settings to meet changing conditions.

• Change in atmospheric temperature: The general rule is to raise inflation pressure slightly as the temperature falls and lower it as the temperature rises. If there is a distinct difference between morning and afternoon temperatures, raise the inflation pressure a little in the morning for a better grip by increasing the load to generate heat. Lower it in the afternoon to reduce generation of heat by the tire. This rule applies for summer and winter also.
• Understeering / Oversteering: Raise rear tire pressure about 3 psi to correct understeering and lower inflation pressure in the rear tires by the same amount to counteract oversteering. The opposite is also true for front tire inflation pressure. This should not be changed, however, because tire stiffness caused by the proper inflation pressure is needed on the front wheels.
• Compounds: Tire pressure can be raised when using the hard compound SL tires. With the high grip compound, it can be lowered.
• Variations in road surface: Lots of rubber residue on the road surface causes greater resistance and on such a surface it is good to lower air pressure to reduce heat generation by the tire. This holds especially true in summer.
• Wet tire: Use the same inflation pressure as for dry conditions or raise the pressure 1-6 psi. When the track dries out, however, a heavy load is imposed on the pattern blocks on the corners and the tires are subject to coarse abrasion. The best remedy is to change to the slicks as soon as possible but it’s also possible to use wet tires, with reduced inflation pressure, for driving with a good grip. Coarse abrasion also affects slick tires if m of the road surface is very high, when drifting or putting a heavy load on the tires. Use the same remedies to this as explained above for wet tires.

Determining if the chassis is twisted ( tweaked ).

Run enough laps to get the tyres up to operating temperature before checking the temps. Remember that the temperatures from one side to the other probably won't be the same because race tracks generally have more turns in one direction than the other. For example, if the track has more right-hand turns than left-hand turns, the left side tyres will run hotter.

Put the probe into each of the three reference points on both front tyres and read the temps. If you are running on a typical track with an unequal number of left and right hand turns and the front tyre temperatures read the same , this is an indication of a tweak. Further proof of a tweak will be that the left rear tyre temp will read much hotter than the right rear tyre temp (see diagram below ).

To cure this problem, adjust the left front wheel downward. This will transfer additional load to the right rear tyre. By doing this, you will also take some of the load off the left rear tyre. This adjustment will raise the temp on the left front tyre when the kart is run again.

Make enough laps to get the tyres up to temp and take another reading of all four tyres. Note the difference between the two front tyre temps. Now, note the difference between the two rear tyre temps. If you make enough adjustment on the left front spindle ( king pin ) the two figures should be the same.

Front to rear weight distribution.

Although most drivers have enough feel for how the kart is handling to be able to diagnose understeer ( pushing ) and oversteer ( loose ), it's impossible to feel the small amounts of front-rear imbalance that can slow you down slightly.

If both front tyres run hotter than the rears, there is too much weight on the front of the kart. There are two ways of curing this problem -- 1) move any ballast lead bolted onto the kart to the rear, and/or 2) relocate the seat toward the rear.

Once the problem is resolved, the front tyres should read cooler and the rear tyres should read hotter than before.

And of course, reverse the procedure if both rear tyres read hotter than the fronts.

How hot is too hot ?

According to the tyre manufacturers, most karting tyres are designed to operate in the 74C (165F) to 85C(185F) degrees range. Bear in mind that the tyres cool very quickly upon coming off the track. No matter how quickly you read the tyre temps with the gauge, the numbers will be less than when driving.

Almost any kart tyre will self destruct it it's operating temp exceeds 100C (210F) A kart tyre getting close to the upper edge of it's optimum temperature range will take on a shiny, wet look when on the track.

Intro : ME

text from russellkarting.com/settings.htm

text and illustration from www.kartpedia.com (it uses probe to measure the temperature, we mainly use guages to read pressure locally. )