Rear Axle Width

4 posts were split to a new topic: Birel with a Briggs 206 Hopping in Turns on MG Red

Maybe for KF category, not for KZ, and even for KF I don’t see anyone using short axles, at least not in the European competitions.
Bottom line is, will a shorter axle give you better laptimes?

Yes, professional drivers use shorter axles as well. Actually, I think they are the ones that use it most as it is a fine tunning (in my opinion) and usually weekend drivers do not feel the difference.
When I created the topic below, I didn’t realize there was a topic already discussing this matter, so I described there my opinion about rear axle length.


I’ve been going through this dilemma on my IPK (Praga) recently. The axle that came with the kart second hand is a cut axle of 1020mm. I recently slightly bent it had had to install a new 1030mm axle. For a quick and dirty comparison I found that the rear grip I’d normally have with the 1020mm axle @ 1390mm rear track is about the same as the 1030mm axle @ 1405mm.

Now I’m wondering if I get another axle and cut it back to 1010mm or even 1000mm to see the results. Either that or comparing with short hubs or a less grippy axle…

I’m going to first assume that your end goal is to free the rear of the kart.

Based on my experience with cut axles, I think your need is going to depend on which phase of the corner you’re trying to prioritize. If you’re mainly trying to optimize the last third of the corner (corner exit), then shorter hubs will give you a similar result to a shorter axle. If you are trying to free the rear on corner entry and mid-corner, then a shorter axle is going to be more impactful than shorter hubs, also with the same impact to corner exit described earlier.

Your mileage will vary based on the category you’re racing, as well as your tire compound. I’ve found that as a rough rule of thumb, shorter axles will favor lower HP classes (KA or even X30).