Is it just a classic bike thing to struggle this much with a tire change? If it were a 17-inch bike, this wouldn’t happen….
When I mounted the Q5A 150/70-18 on a 4.00-18 wheel… the actual measurement came out to 162mm. It was making solid contact with the chain, so I offset it.
Today’s Suspension & Fitting Maintenance Log
Target Vehicle:Suzuki GS1000S
Tire Used:Dunlop SPORTMAX Q5A (150/70ZR18)
The Shocking Reality: Despite the nominal size marking of “150mm”, when mounted on the rim and inflated, the actual measured total width came out to **”162mm”** (width increased by +12mm).
The Key Point: I measured the clearances between the drive chain line, torque rod, and chain case from all angles using digital calipers. I performed precision base work to eliminate interference and safely extract the high-grip performance of the 18-inch radial tire!
Since everyone keeps saying “contact, contact”, I took a close look. Sure enough, the pin is making solid contact. This is rough.
The chain adjustment is measured by the distance from the pivot/axle shaft on both sides, so there’s no mistake there. Suzuki bikes have surprisingly good clearance, so I’ll work around it somehow.
It’s a handy item when you just need to make a small adjustment.
The clearance was so tight it wouldn’t fit in the hub, so I lightly ground it down. Incredible.
Successfully cleared the contact issue ( ﾟДﾟ)
We managed to resolve the clearance from wide areas to tight areas to barely acceptable. Any more than this would require manufacturing a new sprocket carrier (hub). This time I just fudged it with shims.
One problem solved, another appears. Now the chain is contacting the sprocket cover. I ground it down good.
Finally, installation is complete (*´ω｀*)
It’s a common classic custom bike thing, but… it took more time than expected. I thought I could deliver it the week after I received it, but… am I being too optimistic? That’s the maintenance reality.
I occasionally polish the back of the tank (*´ω｀*) Motorcycle maintenance ultimately comes down to hope? and prayer? … Spiritual power is activated.
Finally, a test ride and if all goes well, it’s complete~
Suzuki GS1000S (Classic air-cooled superbike).
Topic: Fitting the Dunlop SPORTMAX Q5A (150/70ZR18) and measuring its actual physical width. Details: Today’s footwork log features a Dunlop Q5A rear tire installation on a Suzuki GS1000S. Although the nominal size indicates a 150mm section width, mounting it on the rim and inflating to operational pressure revealed an actual measured width of 162mm (+12mm wider than nominal). On classic chassis, an extra 12mm can easily cause dangerous tire contact with the drive chain, torque rod, or chain guard. We carefully checked all clearances using digital calipers, verifying zero friction and optimal drive-line alignment. Verdict: Never rely solely on nominal tire numbers. Verifying real-world measurements on the rim is essential for safe, high-performance radial tire conversions!
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