I have a Jr 102 top kart chassis that my son is now racing. I’m in need of a good starting point on the front and rear tire track widths. Currently it’s 44″ in the front and 51 in the rear. That’s outside measurement on the wheels. The kart has been scaled properly. The rear of the Kart is sliding out mid corner and the rear tires just don’t seem to be getting hot. Too much front grip? Rear is too wide/narrow? Not enough weight transfer? Any ideas would help.
It’s been a very long since I’ve had a JR and it’s going to be awhile until there will be another in the family, but here goes.
First off, don’t be hesitant on trying different setups. If nothing else, you’ll what not to do the next time. A couple of things to try besides tire widths: Moving the seat up will result in a higher center of gravity which will result more weight on the outside rear wheel. Is your driver leaning into the turns?
Try adding more castor. That will increase the jacking effect and again get more weight on the outside rear tire. Changing your tire could help as well.
If you are struggling and desperate, ask the people you race with. If there is a local kart shop that supports younger drivers, ask them for help.
Rear seems too narrow. Should be closer to 53″ probably.
Could be that you are too narrow right now and the kart is lifting too hard initially and overloading the outside tire, causing it to lose traction and slide mid-corner.
I never keep track of tire temps, but how are you measuring your tire temps to determine that they aren’t hot enough? If the kart is sliding the rear, the rear tires should be overheating, which would be the opposite of what you’re describing. They would show a corn-row type graining pattern with slight cupping/tear on the inner shoulder if they were indeed sliding and overheating.
How big is your driver, what class is this, and what tire are you on? Can the driver feel the inside rear wheel lift on turn-in? Does the kart turn-in appropriately? Any understeer?
Thanx for the info, right now the seat sits mid rail and the rear axle is all the way down. Ran new tires this weekend and that helped but he says it still feels like it wants to slide out. I’m looking for a good baseline measurement and I know manufactures have guides for this but top karts website doesn’t have a set up for the mid size chassis. Any suggestions are helpful.
It’s our junior sportsman class with a kt100 3 hole can. After looking at it closer it looks like he was not slowing down enough and floating the kart into a big fast turn at the track. So maybe he’s just not setting the kart properly at the beginning? He’s not very big only weighing 75lbs for a 300 lb class. Had to add a lot of weight to the kart that’s why we made sure to scale it.
It’s a 102 chassis which is in between a cadet and full. Seems like I have been confusing too much rear grip for the front. Would you say that if he is still trying to turn the steering wheel after the apex that the kart is pushing and not enough front grip?
Thanks for all the help guys….. Went out for some seat time over the weekend and he got to follow behind a really experienced driver. The kart looked really good and he ran his fastest times yet. The front is what’s pushing a little so I’ll be widening the rear little bits until it balances out.