Are MXC wheels worth the money?

@tjkoyen Yes, I run KA, we run Hoosier R60B, relatively low grip track, finals are either 10 or 12 laps on a 30-40 second track AND we don’t do a warmup lap and don’t allow tire scrubbing to build heat in a tire. Straight out of the pits, around a short oval and start the race.

…of course I justify my unique case where the MXJ’s actually work better and then we have a 20 lap final this week …runs to garage to mount forged wheels instead


crazy, I didn’t know races were ran with no warm up or tire scrubbing just go out cold, must be a wild first few laps! Thanks guys, worth a shot to test the MXCs and see how they go, some of our hotter races are easily 100*+ air temp, with pavement even hotter, and its easy to end up sliding more than you should on the harder tires, so anything to maybe help the tires is worth it. will give it a shot and report back

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I thought this was normal. One lap to line up for the start and go…

Anyone know how the MXC or other OTK wheels align with the birel/compkart DF wheels? Not finding to much detail on them other than they are mag.

Hi Clayton,

The Compkart DF is a wheel that offers considerable amount of grip. It is closest to the OTK MXJ and the AMV Tiger in terms of performance characteristics. I race a Compkart so I am fairly familiar with this wheel. It is a nice wheel and has a pretty wide operating range, when grip builds there is a chance you will need to work to free up the kart with DFs on.

In the interest of full disclosure, I am the AMV wheel importer for the east coast but I try to be as objective and unbiased as possible with my information and feedback. Here is some information that I have put together on wheels that you might find useful.

  1. Magnesium Kart Wheel Specifications – spec data on AMV, OTK, DWT, and Techno wheels. I did not put the Freeline in but I will add it.

  2. Kart Wheels Explained - a look into the design variations, coatings, backspacing, etc… that different wheel manufacturers have chosen to employ. This information is a summary of the information I have received from the team at AMV SpA in Italy.

  3. Track Test AMV 3F and Tiger at the recent 2020 USPKS in New Castle

  4. Track Test Results - Freeline DF v. AMV Tiger v AMV 3F. This was a test done by Compkart team owner and driver John Bonanno.

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All this talk of differences in Wheels has me thinking. So far the discussion has been about design and materials. Has anyone come across a wheel with a different offset from the hub? In automotive applications, it is common for the outside face of the wheel to have very little offset from the hub face. Usually just enough to clear the brake calipers. Why is it in Karting, the offset is shifted to the inside face of the wheel? On Front Wheels, this tends to be a smaller % of offset compared to the Rear Wheels. Would there be a circumstance where it would be advantageous to move the mounting surface of the wheel toward the outside face of the wheel?

Example: Widening the rear track width accomplishes two things. It reduces the loading on the outside rear tire by moving the contact patch further away from the center of gravity. It also lengthens the axle increasing its ability to flex under load. Of course there are multiple factors involved like height/weight of the driver, flexibility of the axle, grip of the tires and many other setup characteristics of the chassis. Now apply this to a Rain Set up. Typically you would narrow the rear and widen the front. This is done for two reasons. One, to increase the rate of Mechanical Jacking in the rear of the kart and move the Center of Gravity over the outside rear tire to maximize Grip. Two, with the front and rear tires now lined up with each other, the front tires will disperse water ahead of the rear tires improving the contact with the road surface and thereby improving rear Grip. Assuming you are using the same Axle, the increased Mechanical Jacking would decrease the contact patch of the outside rear tire at peak unload of the inside rear, because the outside rear is now tipped to the side slightly. A “softer” axle flexes more allowing the outside rear to stay more parallel with the road surface. Now if you had a wheel with a mounting offset toward the outside face, you could effectively run a narrower rear track width while still having a longer piece of the axle exposed to provide more flex and still maintain a similar parallel contact patch with the road using the regular axle.

Any thoughts or has this already been explored and I am just unaware of the outcome?

Hi Greg,

There is a lot here to unpack and I spent a lot of time trying to understand the trade off of offset and moving the wheel out on the axle by talking to the guys at AMV. Basically, AMV and a few others make different offset / backspaced wheels. Typical is a 58 mm backspacing. In the AMV case, we make a 63mm backspaced wheel, the Tiger. The main advantage of an inward offset is enhanced grip during the acceleration phase of the corner. The design key, however, is to find a balance that does not create too much grip, heating the tires too quickly and causing the kart to slide.

Then there are all the implications on sliding the hubs out to account for the different backspacing. For me personally, I have simplified it to:

  • need more grip, use the spoked wheel with the greater backspacing
  • need to free the kart, use the solid wheel with standard backspacing
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would love to see some empirical test of the MXC vs these AMV rims (and hubs?) in regard to how quickly they get heat out of the tires. would think some fairly simple tire temperature sensors or pyrometer testing could definitively show if one rim/hub setup was pulling heat out of the tire more effectively than another? interesting stuff!

I was planning to do a test like this using a mychron to measure tire temps on track and overlaying the performance of different wheels.

To suffice til then there is the data on back to back hot tire pressures. We controlled for as much as possible and the difference was noticeable between the different wheels.

Thanks Paul, I might have to try a set. Not sure I’m back to point of tuning by wheel choice, but it’s been so hot here in the Carolinas I might take a stab at the 3F or 9Fs.
Is there a certain point when you know you need to jump to a different wheel? Blistering, temps, or signs of overworking the tire? Lastly, any chance you’ll be at GoPro Moto anytime soon?

Usually the first sign is when the kart starts to bind up. With Freeline wheel, this will happen if it is hot and there is a lot of rubber on the track as the wheel has a lot of grip in it. You can make other changes than the wheel first to free the kart.

Blistering will be another sign but you will notice the binding up first. Blistering is pretty extreme. The other condition is overheating the tire where the tire will look more moist and even a little blue-ish. With that, lower the tire pressure and adjust the chassis set-up to take grip out of the area exhibiting the problem.

I plan on being at GoPro for the USPKS race in October.

Think of it this way, and I am sure that some people will not agree with me, but if you always race at a track that has a ton of grip, consider using a freer wheel as your standard, baseline wheel and leave the Freeline wheel for days or tracks without grip. This way you will have your set-up 90% honed in on with the wheel that works best for you in most of your race conditions. Take the Kart Republic guys as an example. They use the 3F wheel for nearly all situations – low grip, rain, etc… and only change to the Tiger as a last tuning option if they are dealing with a special situation. Wheels are pretty big change but with 100cc and TAG karts you are often trying to free the kart.

Thanks for the input! I’ll see you at GoPro soon then. I’ll try to reach out to you before that to get a set of wheels.

So this one still mystifies me. I had MXL’s which were the low volume of the forged OTK wheel. They were a little too “free” for the hard tires we run in KA and the low grip track I generally run. I’ve purchased 2 sets of MXC’s for this season and intend to use them as my primary wheel this year. But looking at the profile next to the standard MXJ wheel I still struggle with how a higher volume, but forged construction wheel, is going to add value.

First test of the season this weekend, I suppose we will find out soon how much I do or don’t like them.

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Grip level with the MXC should fall pretty neatly between the MXL and the MXJ. I wouldn’t get too worked up about the how and the why, just test them and use your findings to inform future tuning decisions.

I think the difference in volume is negligible when thinking about the entire volume inside the tire.

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If read this thread.

Is it possible to say use this rim with his temperaturen en this rim with this temperature.

I have a set of MXJ’s and a set of MXL wheels.
Now I am also looking for a set of MXC to complete rims, do you guys think this is necessary?

Mxj and mxc are the rims to have
Mxl useless and we run mxc’s 80% of the time

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Can you expand on this? Maybe talk more about the conditions you found them unsuitable for.

No benefit in any conditions
Track Green mxj/track in normal condition mxc end of the story

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What do you mean with track green?

My experience tends to be the same as Paul’s. I still prefer the MXC over the L. Last time I drove the L it felt like the kart was on top of the track rather than actually working.