Rear tire size 81 GS750E Question

[Guest]

Every spec I can find on my 81 GS750E shows rear tire at 4.00x18 . Every tire chart I see for rear tire conversion shows a 110/90 as equal to a 4.50 and nothing for a 4.00 rear tire. Anyone running a 110/90-18 on theirs? I'm worried about side clearance not performance. I want to make sure it will physically fit without rubbing the swing arm or chain.

[Steve]

I don't have that bike, I don't have that size tire, but the way most of these bikes were made, there was a bit of room beside the tire.

If you do the math, a 4.00 tire would be 101.6mm wide. You KNOW that it would not be dangerously close at that size. Most of us have found that you can round UP to the next "10", so a 110 tire should fit just fine.

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[Nessism]

A 120/90-18 should fit fine. It's a little wide for the wheel but fine. I don't think there are any clearance issues either.

[jdvorchak]

Thanks guys. Other than the brakes I need tires and this guy is about ready to test ride. I haven't posted pics of it lately because it's pretty much apart and doesn't look like much. But it is cleaning up nicely.
My project thread is here:

http://www.thegsresources.com/_forum/showthread.php?241311-81-GS750E-Yard-find-going-to-need-lots-of-TLC

[hannibal]

For what it's worth, I just mounted a Shinko 230 in 120/90-18 on my early GS750. Stock was 4.0x18.
No clearance issues.

[rudeman]

I ran a 5.10 x 18 on my '77 GS750B. That's equivalent to a 130/90 and I had no issues other than it slowed the steering a bit.