Temperature Changes

[Joe Harper]

This message is from a novice karter.

We have a R30y-c, new to us, just a couple races so far. This weekend was our first of the year, we did ok, considering we have moved up to the 12-15 Junior Supercan.

We noted that as the ambient temperature rose (it rose from the low 50's - mid 70's F.) that we were not able to adjust the chassis accordingly. We thought as the tracked warmed you would get quicker, not slower. Luckily as the late afternoon temperatures cooled for the feature, we went back to orginial setup, and were able to run our best lap times of the weekend.

In order to respond, you probably need a lot more information, but here is the basic setup.

Yamaha Junior, 12-15 year, 305 pound class, Bridgestone YHC, 4.00 fr, 6.00 rear, 14 psi front, 16 psi. rear, front bar removed, rear bar tight. About 35 lbs attached to the seat. Zero toe when on the stand, fronts spaced out about 3/4", the rest of the kart is setup as it was delivered. We tried several things, nothing appeared to help.

Thanks, any insights, would be greatly appreciated.

[Wesley Boswell]

Joe,

Did you adjust the tire pressure throughout the day? If you ran the 14-16 all day then that might be your problem. The 14-16 sounds like a good starting point for tire pressure in the morning, but when it the track gets hotter your tires will get hotter as well and eventually over heat. I would of tired to run the YHC's around 12 or maybe even 11 on a day like that.
Also if you had the front bar out that would probably work good when its cold out, but when the track gets hotter it might cause a little bit of a push after about 7laps which would also slow the kart down. So you could of tired putting the front bar in when it warms up.
There could be many reasons why this happens, I'm just pointing out 2 of the things that I see here that may have cause that problem. If you get a chance test those 2 things and see what happens.

~Wesley Boswell

P.S. Set the toe at 2mm toe out on the stand.

[Joe Harper]

Thanks Wes for your quick reply, we will give it a try. We appreciate your support.

[Chris Lobaugh]

Hello Joe,
have you tried loosening the middle bearing on the axle? Most of our R30's are assembled with M axles which might be a bit too stiff on a warm day. By loosening the middle bearing (loosen the bolts that hold the cassette to the frame) you allow the axle to flex more and "free up" the kart. This is a quick change that can be made on the grid and even during a practice session. If this change helps than I would suggest geting yourself an F axle (the next step down on the axle chart). Hope this helps.