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can i run a bias (not radial) tire on my 13" rim?

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can i run a bias (not radial) tire on my 13" rim?

Old 11-14-12, 10:25 AM
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can i run a bias (not radial) tire on my 13" rim?

Im trying to find good used racing tires to use for competition licenses and track days. Usually i can go to events at road atlanta and bum them off people and they are perfect for my corvett. I run a 275/40/17. However with the rx7 im currently running 225/45/13. Not many big players are using this tire so no a lot of used ones to pick up on the cheap.

However, a lot of open wheel racers use bias tires. Im very unfamiliar with their measurements, can i use a bias tire on the rx7? What size would i be looking for? What do the measurements mean? Are they in inches instead of mm?
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Old 11-14-12, 11:23 AM
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the measurement is in inches
so a 26x10.5x 16
26 is the tire height, i.e from ground to the top of the tire
second # the 10.5 is the ire with, so 10.5 inches wide
third# is rim size
225= 8.8 inches, so a 9" wide or 8.5 will work fine

OnlineConversion.com - Tire Size Conversion

its a 21" tall tire
so your looking for a 21 x8.5 or 9 x 13
go fish if that exists

but i see hoosier makes a 20x9x13 and a 20x8x13

hope all that helps
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Old 11-14-12, 02:15 PM
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the star mazda's run some kind of 13" they don't really look they would fit an Rx7 chassis though
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Old 11-14-12, 04:29 PM
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You can not put a slick designed for an open wheel car on your RX-7. It would fit but it won't perform, they are not designed for the added stress from the extra weight.

If you are looking for used 13" racing tires I would look for the bias ply cantilever slick designed for SCCA GT and Production car racing. Often times there is money spent in these classes and tires that are only used for 3-4 sessions. Your best bet to find the tires would be on the GT or Prod forums.

Some of the Spec 7 classes uses 13" but they tend to run the tire to the cords.

Get yourself some 15x7 rims and get a boatload of race slicks dirt cheap [shameless plug] https://www.rx7club.com/race-parts-o...tment-1007560/
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Old 11-14-12, 06:18 PM
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Sounds like if i move to a 15" then i would have gearing problems. My current car is perfectly geared to where i reach 7k on the straights at cmp and 8k at roebling road (where i spend most of my time). wouldnt it also raise the car farther off the ground and i would loose the low center of gravity and my front ground effects would not be as effective. Any other outlets you might suggest for inexpensive race tires used?
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Old 11-14-12, 08:45 PM
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my formula mazda uses 7in fronts and 9 in rears they are 13

i always look through hoosiers discontinued tires off their website.

i run a 205/50/15 hoosier SM6 in my miata. they are like 160ea from Appalachian tire (racetire.com)
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Old 11-14-12, 09:16 PM
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Originally Posted by rithsleeper View Post
Any other outlets you might suggest for inexpensive race tires used?
Lee is a very reputable and legit used race tire reseller. You can find his inventory on eBay
leegrx7 | eBay
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Old 11-14-12, 11:16 PM
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Your 225's are a hair under 21" tall. You can find 20 and 21" tall slicks used on the small bore Production and GT class cars that use 13x7 rims. 23" is the smallest I've seen in the 15"
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Old 11-15-12, 12:14 AM
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I ran 20x8x13 bias slicks on my 7" Panasports and they fit fine once I spaced them out. These tires are designed for 6" wide wheels but fit fine on my 7" wheels and they cleared the fenders.

The issue you run into with 13"/15" production car bias slicks is that they are canttilevered. The tire manufactures do this to get around the SCCA 7" wheel width spec. Cantilever tires allow you to put 9+ inches of rubber on the ground using a narrow wheel

So while this means that a 20x9.5x13 is a 9.5" wide tire is designed to be mounted on a 7 inch wide rim there is allot of tire hanging out over the edge of the rim. This creates clearance issues with the struts and the fenders.

By the way, you'll have the same issue with 15" production car tires because they are cantilievered too. These are the tires you will see on an EP RX7 and they all have wide body flares to cover the tires.
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Old 12-03-12, 11:41 PM
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yes you can
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Old 12-04-12, 08:13 AM
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NH

15 inch wheels.

used Spec Miata tires. Hell any 205-50-15 will work really. New is not that expensive anyways. We run Nittos NT-01 on our IT7 cars and they only get faster when they wear. Think about the rolling resistence and a lower powered car.

I have 15 inch wheels for a first gen for sale if interested.

Konigs, ROH, Team Dynamics, Kosei

Just ask
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Old 12-04-12, 08:54 PM
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Search eBay for “USDRRT" He sells used Hoosier slicks in 13" and up for pretty cheap.
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