Hi everybody.
I need help or explanation about an issue I had on weekend.
Since two month I got a new Chassis. When i was first out it was really warm around 30 degrees and the chasssis worked pretty well. I had a standard setup with a medium axle and 1395 mm width in the back. after that i huert my ribs and couldnt drive for a long time. Went out on Saturday to test but still had the issues so could do only one turn. But on this run I had a strange behavior. the back was sliding alot. It was around 22 degrees and sunny and days before it was raining. But the track was dry. So i was now around 1.3 seconds slower than the last time, but all other drivers also. I thought ok no grip. but when i came in the tyres looked very good and the tyrepressure was aslo ok. and when i wanted to lift it up it was like glued to the track like they were on perfect temperature. but how can it be? i mean if i was sliding like this, the tyres would never have this amount of grip to be glued on the track. I was also driving befor on low grip condition and the tyres than looked also like they didnt warm up. But this was opposite. So what do you think about it.
So everyone on track had same experience?
Track could be green?
Did not speak to the others but I stopped the time and they were also alot slower as usual. I think it could be green but that wouldnt explain why the tyres were so grippy at the end. But in this case normally I would go for longer hubs or narrow them but I read in many guides that if the kart oversteer into the corner you should go softer on the back, would mean shorter hubs and max width at the back.
The reason the tires were grippy at the end was that as the tires were sliding on the track surface and built up too much heat. If you had the ability to increase you castor, I would have done that first before changing hubs.
The track lost all it’s grip from the rain, so very green track. I’m not quite understanding correctly; is the kart sliding or is it stuck to the track?
If everyone else is experiencing slower times too, it’s definitely the track’s grip level.
I was driving many times before on a green track and was also oversteering going into corner but they never got temperature like last time and they were never grippy. This is what made me curiuos.
So through the sliding and heating up the should gain than more grip, but this wasnt the case.
So wald would be the best? Going softer or stiffer in the back?
What chassis and tire?
Loose has 2 potential causes; the front is too narrow, or the rear is too wide. Push has 2 potential causes; the front is too wide, or the rear is to narrow. Read my sig and decide for yourself.
Sig:If the data does not support the theory, get a new theory. (Al Nunley)
Rear is almost at max. I managed to try the front on the one run. but as soon as i widen it, i feels worse. Couldnt try to narrow it.
Its a gillard dd2 with mojo d5
Widening the front track will make the kart oversteer more.
On a low grip track, try narrowing the rear track width. That would be the first change I would make.
“Oversteer”? Doesn’t that mean loose? That’s not my experience. But I agree with you about narrowing the rear tread width. In my experience, it’s 6 of one and a half a dozen of the other. That doesn’t mean you’re wrong, I’m just saying it’s my experience.
Yes, oversteer = loose, as in the rear is coming around on you.
Wider front track = more weight transfer
If the kart is oversteering on entry/apex, you want to narrow the front track to decrease the initial weight jacking. If it’s oversteering at apex/exit, you’re probably looking at oversteer stemming from initial understeer. In that instance, increasing the weight jacking can help plant the outside tire better and reduce oversteer.
@ TJ
you say 2 posts above that narrowing the rear would be the first change, but wouldnt it be the same effect as widening the front?
Not necessarily. In certain conditions, widening the front and narrowing the rear can have similar results. Front width also affects turn-in rate, front scrub, and geometry, so it can have knock-on effects down the line if you make an adjustment. Narrowing the rear has a lot less variables to consider. Looking at it in your context, you said your rear width was 1395mm, which is near max, so my thought is that the rear isn’t getting enough side bite due to the width/softness of the rear.
If you were to widen the front right now, it would make the issue worse, as you said you tried. This is because the kart is fundamentally too wide in the rear for the conditions, so it isn’t driving the outside tire into the track, it’s driving it across the track. I think you want to get it narrower so the center of gravity is higher, and you can get the kart to tip and bite into the track better. I’m only talking about narrowing the rear 5mm or so, so a small change.
I could be wrong of course, but any time I feel the kart is sliding due to lack of track grip, I narrow the rear 5mm at a time.
makes sense, the frame before was very stiff and i needed it to soften alot in the back to make it work with the mojo. the new one is more flexible so i think his could work. because as i tested it first in good conditions it was superb, and after that i went out on saturday without changing anything.
What about raising the pressure in the rear?
Not too familiar with how the Mojos work, but if you think you’re overheating the rear tires already by sliding, that will probably make it worse. I might try lowering the pressure to get the tire to flex a bit more and bite into the track.
Ok. I was slready at 0.57 bar cold
This is quite low I think, maybe you’re right, you might need more pressure.