karting...september race report

That snot good!

This race report will be brief, but for those who actually like my reports, I will write something.

On Friday I came down with a stinking cold, so I was a little concerned that I might be too ill to race. Come Saturday morning though, I felt like I could cope with racing and decided to go despite the constant dripping and drying.

Saturday testing.

We got there a bit late, so we missed the first session, but only by a matter of minutes though. The second session was not much fun though as my kart decided to chuck a chain just as I tapped a kerb on lap 2. What happened was that last week I changed the rear axle bearings, but I didn’t quite tighten the axle mounts up enough. So the axle was moving around while I was driving, and when I clipped the kerb, it sent just the right shock through to rip the chain off. Fun.
Third session we tried some different tyre pressures. Normally we run 16psi all round, this time we tried a bit higher so that the tyres should heat up quicker. Unfortunately all I had was oversteer, a bit of oversteer and a truck load of more oversteer. There were no major driving mistakes on my part, just the usual constant corrections and occasional missed apex or two that you would expect from a car with a poor balance.
Fourth session we reverted back to about 17 all round. The kart seemed much more controllable, but the times were only a couple of tenths quicker and as usual, the tyres took forever to heat up. While sitting on the grid I was chatting to a novice friend who has a very experienced mentor (his mentor is challenging for the championship) and he told me that his mentor was running about 22-24 psi. This is quite different to my usual set up, but most of the day had been a bit of a farce so we decided that we had nothing to lose by giving it a go.
Fifth and final session it was then that we tried out the new tyre pressures. Apart from chronic understeer at the first bend on the first lap (probably more caused by over exuberance) the kart felt very good. The higher pressures effectively made the kart stiffer so that it was no longer bottoming out. It felt far more pliable on the limit aswell and the tyres got up to working temperature very quickly indeed. The only problem with the session was with the driver. I had no idea whether the kart was about to throw me into the nearest tyre barrier at the next corner, so I was fairly cautious. I started to push a little on the last few laps, but I pushed too hard and lost a bit of time. Non-the less, the fastest lap of the day, despite a lock up and a completely missed corner was in the last two laps of the session. My slowing down lap would have been quick too because I had finally worked out the balance of the new pressures. The max revs were the lowest all day, but that is probably because the tyre diameter would be larger with the higher pressures. There was one little scary moment as I managed to get completely side ways while turning into Inkermans. I held it, but only probably because of the better set up. A device that we fitted a couple of months ago called, ironically, an ‘easistart’ wheel packed up, just as we were trying to get the kart started. It will now be removed and we will have to resort to the old tug-n-push method of starting

Sunday. Race day.

It looked as if it would be interesting weather for Sunday. The forecast pointed to showers and sunny spells. In other words, I would be flipping a coin before every heat to decide whether to put wets or slicks on. As it happened, there was no chance for me to experience my first wet race. My dad also came down with this cold, but it affected him more than me so he was unable to take me down to the track. Meeting over. At least I now know a better tyre pressure for next months meeting…if it’s dry.

Sorry, this report still ended up been long, but anyway, thanks for listening


if you did actually read this report, could you reply or something so i can get a rough idea how many people are interested in my reports. any comments would be nice too

Well, Simon, it's a real shame that you didn't get a chance to actually race! :( I'd absolutely hate it if it happened, I'm sure you did too. The World needs a quick cure for cold! :)

Do you change tyres after every event or do you run several meetings on the same tyres? And BTW, at a couple of races this season Ralf Schumacher and Montoya started races with different tyre pressures with Ralf pumping, or rather having them pumped up, more. The result was that he was really pulling into the distance on the first several laps, and then JPM's tyres would get up to temperature and he'd start making ground on Ralf. Also Ralf's tyres wuld wear out quicker. So it's a fine ballance between all the variables, hope you are able to find it.

And here are two threads on the effect of tyre pressures on car behaviour. Link 1 (http://www.automotiveforums.com/vbulletin/showthread.php?t=88908) and link 2 (http://www.automotiveforums.com/vbulletin/showthread.php?t=88922)

the top boys in my championship change tyres after every event, but i simply cannot afford to do that. so i run tyres for probably 4 or 5 meetings :eek7: .

thankyou for the links, but i already know most of what i should about what presures do to the karts handling. unfortunately i have not devoted much testing time to tyre pressure analysis because i have been more concerned about learning to drive well before i start messing with set up.

so far my basic understanding from experience is that:

lower pressures mean that the tyre heats up less quickly, and will ''go off'' later than with higher pressures. it also softens the spring rate of the kart, which can be used to adjust the ballance
however, if you go too low the kart will be very, err ''sqishy'' on the limit and will allow the rubber to move around a lot which creates heat...so the tyres will heat up quicker.

higher pressures mean that the tyre will heat up quicker, but may ''go off'' sooner. the spring rate is hardened, but if you go too high, the contact area will become way too small and grip will tail off and probably cause premature wear and over heating of the tyre.


all this knowledge is great, but i still need to do some more testing before i know exactly what the best set up is for my kart/driving style/track and conditions.

So how often to you go karting? And is it indoor or outdoor karting? I so wish my parents had sent me into motorsports when I was young(er)... sigh.

So how often to you go karting? And is it indoor or outdoor karting? I so wish my parents had sent me into motorsports when I was young(er)... sigh.

oh no, its deffinately outdoor. the kart i race is at least twice as fast as the ''crappy hire karts''. i try to race every month, but becuase of exams i havent raced much since i got my licence. iv only done 6 races since i got my licence back in jan 2002.

Hi Simon,
fascinating article, how often do you practice?

Also running up to 32 or 34psi in the wet creates a rounded shape to the contact patch which helps disperse water. Try that next time it rains. As for chronic understeer, just widen the rear track by 10-20mm 0.6-0.8in. Something for better turn in that I havent tried but am told works is to loosen all the floorpan bolts! this allows the chassis to flex more and thus unload the inside rear wheel on entry. I havent done it cos im worried about the floorpan falling off but I think this can be avoided with loc-tite.
Something else to give the tires better initial grip is to drag a flat piece of metal over your tires to remove the marbles and other bits and pieces before you go out.

Hi Simon,
fascinating article, how often do you practice?

normally its the day before the race. i rarely have the oportunity to practice at any other time

Also running up to 32 or 34psi in the wet creates a rounded shape to the contact patch which helps disperse water. Try that next time it rains. As for chronic understeer, just widen the rear track by 10-20mm 0.6-0.8in. Something for better turn in that I havent tried but am told works is to loosen all the floorpan bolts! this allows the chassis to flex more and thus unload the inside rear wheel on entry. I havent done it cos im worried about the floorpan falling off but I think this can be avoided with loc-tite.
Something else to give the tires better initial grip is to drag a flat piece of metal over your tires to remove the marbles and other bits and pieces before you go out.

in the wet i can run up to 55psi and as low as 20psi. the understeer was only caused by me pushing too hard too early. narrowing the front track would have a similar effect too.

loosening the bolts is a technique that i would normally only use in the wet. in the wet it is generally better to have a more flexible chassis. because a kart needs to flex so that it can lift its inside rear wheel (it has no diff, so if the inside rear wheel remains on the ground, the kart will not want to turn in). however in the dry there is enough lateral force to lift the wheel without lossening anything.

i do not have any trouble with marbles. im very carefull for the first few hundred metres so i can clean the crap off. so the tyres tend to be clean after the warm up lap.