# AFX Magnatraction or AutoWorld X-Traction



## E-Force-1 (May 31, 2007)

What is the best size (o.d.) for slip-on silicone rear tires?


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## SwamperGene (Dec 1, 2003)

Ed a lot of us run PVT tuffie tires on 'em...though I guess alot depends on the track and of course rail height. In fact a lot of guys around here used the tuffie tires in so many different slip-on classes I spec'd them out a while back:



> Just did a little checking with the measuring dee-vice to see how the Tuff-Ones tires sized up across different rims. The "chosen" tire was picked based on the average of a handful and used for all tests, temp was around 60-62 degrees F.
> 
> Unmounted: .400
> Tuff-Ones: .408 (this was a JL Tuffie wheel)
> ...


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## Rolls (Jan 1, 2010)

Great data, Gene. Thanks! I picked up some used G-Plus chassis and I've been thinking about what tires to get to replace the dried out originals. I think I'll just try some of the Tuff Ones silicones out of the bag I got last month from Bud's and see if that takes care of the rears. Thanks, man!


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## tabcomary (Jun 2, 2010)

*A/FX Rear Tires*

I've been using 7/16" (.4375) unmounted O.D. with 1/4" I.D. on stock A/FX rims. Rail cleareance is just about right on old Aurora-A/FX track. I have not checked the mounted O.D. I suspect the numbers will fall in with SwamperGene's list.

T.A.


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## TK Solver (Mar 18, 2004)

Buds site says his TuffOnes silicone tires have ID=.159 and OD=.385, so the cross-sectional area is 0.09656. [ A = pi/4*(OD^2 - ID^2) ] Assuming that area stays constant when it's stretched to fit the standard X-Traction wheel OD of .275, that puts the tire OD at .446. [ ODnew = sqrt(4*A/pi + .275^2) ] 

I run a lot of X-Tractions that way. Some of the XT-UltraGs will actually bog down a bit at that height but the regular X-Tractions love it.


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## tabcomary (Jun 2, 2010)

I would expect lots of non-linear things to happen when you put the 0.159 I.D. tire on the 0.275 rim. Generally, the softer tire compounds (durometer A 20-30) will end up closer to your calculation, but the tougher silicones (durometer A 40+) should have more irregular deformation.
FYI, I measured the sponge tires on a NOS A/FX car last night. The mounted O.D. was 0.442. I am currently running a .445 O.D., but I am going to go a little bit lower to see where I start having clearance problems.


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## Boosted-Z71 (Nov 26, 2007)

I glue all my tires & true them afterwards on a diamond coated grinding wheel, works great on foam, and good on silicone, just take your time. Unbelievable difference in just making them round, & then you can size to slam that chassis to the track.

Boosted


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