40mm or 50mm Rear Axle


New member
What rear axle is everyone running in the LO206 class? We ran a 50 soft last season and it just seemed too tight. I've heard most of the Europeans and Canadians are running 40mm shortened axles to help the low horsepower karts turn better. Instead of the normal 1040 length they're running 960-1000mm

Any thoughts?

Ted Hamilton

Design Drafter / Racer
On a 40mm axle you can slide the hubs in as far as you want....try that (and long hubs to stiffen axle) and see where the sweet spot is.


Depends upon the chassis and other set up parameters 40mm is very popular but have seen 50 on one chassis work very well.


A trial w/o witnesses is like racin w/o tech
I think you answered your own question.
Get out the credit card :)


I always ran short hubs tucked in at least 1 inch from the ends on both sides with a standard length 40mm axle. If you want to run hubs with a lip on the end you'll have to cut the axle ends.

I tried a 50mm set kart and I didn't like it. I'd stick with 40mm or 1-1/4 axles.


Very few people have ever tested multiple stiffnesses of 40 and 50mm to give this answer. Not only is it expensive to buy all the equipment, it's a lot of work at the track to complete all the testing. I wouldn't put in all that time and money and just give it away.


Really depends on what your kart needs. If you have never changed stiffnesses, I would start there. See which direction helps and then start making calculated decisions. Like Gary said, it takes a lot of time, work, and money to do this testing. It helps if you have a couple of buddies. Between myself and a few buddies, we had a few different hardnesses that made it worth testing by borrowing each others axles. If I had to buy everything to test, I could have never done it. In fact, I still have axles I want to try, but just cant pony up the $180 to make it happen.


Comet has a decent assortment of used axles FYI. All guaranteed straight and about half the price of new.
Question -- Why does it cost so much more to make a European measurement (ie MM) axle over an English (ie inches) axle?
I never quite understood that.
A lathe and centerless grinder don't know the difference. :)

I understand the "name brand kart specific" stuff being hiked up in price, Mercedes, BMW, etc do this as well...but it looks to me like there would be a decent market for cheap(er) generic sprint axles, is there not?

Thanks and God bless,
Brian Carlson
Carlson Racing Engines
Vector Cutz
Carlson Motorsports on Facebook
30 years of service to the karting industry
Linden, IN


PKT axles make American made European sized axles that are slightly cheaper than imported axles and are used by many sprint racers. I believe the main cost is in the tubing that both Europe and probably PKT uses to get the flex they want in the axles. Shockwave (USA company) also used to make axles in European sizes but they closed their business in the early 2000s.


New member
Thanks to everyone for your opinions...You're right though , it takes quite an investment to test new ideas so budget racers like myself rely heavily on the input of more experienced guys.
The karting community is one of the best for helping each other out, we're all great friends in the pits but when the engines start....well....


A trial w/o witnesses is like racin w/o tech
Follow the money.
Most of the sprint kart mfg's use the larger axles as well as different wheel hubs to adjust the handling of the kart.
There are a few (fewer all the time) that use a 1 1/4" axle.
The suspicious person that i am makes me think that the the kart mfg's love the idea of using the various stiffness axles for tuning.
The kart comes new with XXX axle and hubs which may not be the best one for your situation or tires you are required to use.
Buy another axle, Still not right? buy another axle.
The trailer for a dirt oval kart is full of various tires for different conditions, the trailer of a sprint kart may have multiple axles hanging on the wall.


Premium User
Axle swaps ARE a common tuning tool in sprint....at the national level, anyhow.

Yes, Ted, but top level teams won't test on used axles, believe me. If you want reliable info you should test on new stuff or axles that have exactly same track time, otherwise results are not reliable. If you attend a FIA/CIK World Championships you'll see axles been the main tuning resource at top level but the main expense too: there are way too many options than won't allow low budget teams testing all of them: a 40 mm or 50 mm axle can be very different dpending on material, thickness and length too. Even same material and thickness axle can act way different even set at same width if axle is axle is longer or shorter, even if you set hubs at same distance.

Ted Hamilton

Design Drafter / Racer
The length of a beam determines its' stiffness....shorter axle = stiffer response. But a hub set in will act like a shorter axle, so I'm with you....I'd test it with hubs in to see if that gave me desired results....and then cut later if the length caused some other issue. But I'd rather leave it stock and get diffferent wall thicknesses or heat treat to get the properties I wanted.