I just use one piece spun aluminum they’re light and I don’t cry when they get crashed up.

That’s a loaded question!
If i remember correctly, Mark Dismore wrote a pretty good article that is on his shop’s website on this topic.

Generally speaking, magnesium are lighter (lower rotational mass) and don’t heat up as quickly, or get as hot as a result. This keeps the tire pressure more consistent throughout a longer run (i.e. a race).

Aluminum will heat up quicker, which can be advantageous in cooler conditions. Aluminum is also less brittle. I cannot recall ever seeing an aluminum rim with a chunk out of it, but have seen many mag rims missing chunks.

Also, if you’re on a crg or crg made kart the front bolt pattern is different (same size as a rear) i don’t think any other manufacturers do this.

Never heard of a track mandating one type over an other, but if your son is racing Jr he’s probably got to run 6’s

Rim type depends on a lot of different things as Oliver touched on above. Bob, definitely go check out the Comet Kart site as I do recall Mark Dismore posting a very informative piece on the differences between magnesium and aluminum.

Just a couple additional points from my point of view: Since magnesium does not conduct heat as quickly or as easily as aluminum, it generally allows the kart to stay freer for a bit longer. All karts tighten up during a run, regardless of what you do. The key is to keep the kart as free as possible for as long as possible. Particularly on really grippy surfaces, magnesium wheels are a little better at holding off the heat transfer/build-up than aluminum wheels. I also think this is more important with the 7.1 tires than the 6.0 tires. But regardless, anything that will help to keep the tires cooler, will help the kart’s handling.

By the same token, we run aluminum wheels with our rain setup. There, we want the heat to build up to help enhance what little grip we can get.

As always, there are way too many variables to just say you want magnesium wheels in X situation and aluminum wheels in Y situation. Track surface plays a part, kart brand, weather, set-up preferences, etc., all come into play. And I would also say in some cases, the differences are so minute that some drivers may not be able to tell the difference or even care.

Good luck!!

Everyone at the front of the field at a national race will be on magnesium wheels for all the reasons listed above.

Aluminum only if it’s freezing cold or raining. But I’ve run the OTK MXC mags in 40˚ weather and didn’t have much of an issue with them.

They just keep the kart more consistent.

Don’t ask about mxc rims.
if you have sticker shock on the normal mags you may have a heart attack when you see the price on those babies!
I’m still a little shocked on them!

You can’t be the best if you’re not the most expensive.

What is the difference between MXP and MXC besides several hundred dollars?

You mean the MXP and MXC? MXC is forged magnesium and the MXP is cast magnesium. Personally I never saw much of a difference at all between the two wheels when the setup is correct. The MXC’s strong point are the long run of a race on a sticky tire, but if you have your tire pressures figured out and chassis close to 95% you can still win a big race on MXP’s in a long run too. Either wheel is proven capable of winning.

Hi Mike,

Yes, I did mean MXC not MCX I guess spell check only works when it’s a real word. Looking forward to the 2015 season  with you and Mark. In the meantime we will just have to bench race a while longer.

If the advantage of magnesium wheels over aluminum wheels is that magnesium (150 W/m*K) conducts heat about 3/4 as well as aluminum (200 W/m*K), then would anyone be interested in cast iron (55 W/m*K) wheels?