Ok, with a 50mm axle is it best to run 6" rears or 7.10"?

Hey guys, I’ve had people tell us that for a 50mm axle you should only run 6" rears. But have others say, No 7.10 rears are better cause you get more rubber to the road. Other have said, it doesn’t matter which tire width you use.
Can anyone give me the truth ( or an education on what is best and why)

Completely depends on the tire and class/engine.

On a low horsepower kart, a 6" tire might help free the kart up, but anything faster than a Yamaha is probably going to want a 7.10. Almost no one here in the States runs 6" on anything anymore, though it used to be a common rear tire for Junior sprint classes.

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Have you been asking specifically about your chassis and the weight you run at? For something like this I would almost disregard all information from other setups and get quality info that pertains to your situation.

Failing that, you’ll have to test. There’s really no other way to know.

I know people that run 6.00 and people that run 7.10. it’s what works for you, not what works for someone else. I’m fast on 7.10s and trash on 6.00s. Other drivers are the opposite.

Is this just for fun? Not for a legit race? I can’t see any series leaving tire size as an option.

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With it being in the 4 Stroke section, I would imagine this is in regards to running an LO206 with a 50mm rear axle. I’ll have to check what they’re running out here at OGP though. Very popular class!

Thanks. Yea for the LO206 class. We can run either 6 or 7.10.

What chassis and tire? With those specifics others will be able to help you out a little more.

Without knowing, I would have similar comments as TJ. If you have a kart that needs to be more free, the 6" would be a better tire.

I can categorically state that an LO206 kart is faster with a 6" rear - but to win a race, do you want to be fastest?

You’d be wrong.

Like others have said, you’ll need to test for yourself.

I’m more comfortable, and therefore faster, on the 7.10. Given the choice, I’m choosing 7.10 every time. (edited to add this is on heavy weights 375lbs +. Class weight will dictate this also.)

As TJ said, it kinda depends. In a Yamaha or 206, the 6.00 inch tires can be faster as they stick less on exit and don’t bog the motor as much. In higher HP classes (KA100+) the extra grip from 7.10s is beneficial. I don’t know how much axle diameter really plays into it, I’ve run 40mm axles on 7.10 inch tires and 50mm axles on 6.00 inch tires. Someone with more experience would need to chime in on that part.

It may just be that some series’ spec their tire to 6.00 or 7.10, at which point it really doesn’t matter which tire you have cause everyone has that tire.

well way I see the tire thing is every 206 should run same tires preferably 6 in Iam sure this will get a lot of disagrees

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I have tried 6” in Yamaha and 206 with 50mm axle and the 6” could be made to be slightly faster at most, but not all tracks we tried it, but took quite a bit of tuning work when switching. We were in a time where 6” were run and then changed to only 7.10 the following year so got some time on both. It seemed to be most beneficial when it was blazing hot on a long track…

The problem was getting the setup right because the rear was so narrow with the 6”. (We run 30mm Italian 2 cycle CIK chassis with 1040mm 50mm axles and YLC tires) Since most tracks and series (and our home track) now require 7.10’s anyway, it, for us, isn’t worth messing with it when going somewhere that allows it because of the time to re-find the setup.

With 7.10’s we unload a lot closer to good than if we were to unload and put on 6.00. There was a track in Ohio we went to a couple years ago and won three times with 7.10’s with the entire field on 6.00 so it obviously isn’t a huge deal. All the advice you got is spot on… try it.

No doubt the differences will be more or less depending on the chassis, tire, track, weather, and setup… the axle is only one part of the equation. If your home track allows 6.00 and the tire is say a YLC or softer, you should for sure test the 6” if you can… for a one off club race, too much headache imo trying to find the handle. For us now, 6” is for rain only.

On the other side of the coin, I see a bunch of old school 4 cycle guys stretching 7.10s across an 8” wheel to minimize side bite (or 6.00 across a wheel for a 7.10) because the sidewall is rolled over. If that’s allowed you could also try that. I’ve heard it works if you can find the setup to go with it.