Post by Just Plain Bill on Oct 27, 2008 20:52:14 GMT -5
Here's an interesting, if unusual, alternative to XS650 and TX650/750 rear spoke wheel conversions for the SR500; a rear wheel from a 1973-74 Yamaha SC500, dirt bike. It has a shouldered (like Akront) 2.15x18 alloy rim, 17mm axle, and 6.75" diameter drum brake (rod actuated). The 17mm axle will save a lot of bother making "hat" shims, tho it still requires fabrication of spacers to fit the SR500 swingarm properly.
There are several other benefits of the wheel: it weighs just 19.25 pounds (compared to 24.25 pounds for a TX750 wheel and 29.5 pounds for a cast SR500 wheel and caliper).
Also, the SC500 wheel uses common, readily available brake shoes, spokes AND a TX750 drive sprocket (530 chain size) and more streetable (40-42) tooth count bolts right up to the hub.
Not really relevant to the above, but the best part (for my purposes) is that it is just 7 inches wide, with the brake plate in place and fits nicely inside a 1979-80 Suzuki RM250/400 aluminum swingarm (which is unnaturally narrow at the axle; something I wasn't aware of when I bought it). Of course, the SC500 wheel will fit even more easily into a SR500 swingarm which is 8.25 inch wide at the axle slots.
The reason for my interest in the RM swingarm is that it weighs about half a pound less than the GigaBike swingarm and 3.5 pounds less than the SR500 swingarm and will further reduce unsprung weight. Downside: it's 2 inches longer than the SR swingarm and will need to have the shock mounts relocated and a brake arm mount welded on. Using it will probably require a different rear fender as well.
Anyway, these SC500 wheels are not common, but if you can find one, it should be cheap (no demand) and is a easy conversion part.
Bill
There are several other benefits of the wheel: it weighs just 19.25 pounds (compared to 24.25 pounds for a TX750 wheel and 29.5 pounds for a cast SR500 wheel and caliper).
Also, the SC500 wheel uses common, readily available brake shoes, spokes AND a TX750 drive sprocket (530 chain size) and more streetable (40-42) tooth count bolts right up to the hub.
Not really relevant to the above, but the best part (for my purposes) is that it is just 7 inches wide, with the brake plate in place and fits nicely inside a 1979-80 Suzuki RM250/400 aluminum swingarm (which is unnaturally narrow at the axle; something I wasn't aware of when I bought it). Of course, the SC500 wheel will fit even more easily into a SR500 swingarm which is 8.25 inch wide at the axle slots.
The reason for my interest in the RM swingarm is that it weighs about half a pound less than the GigaBike swingarm and 3.5 pounds less than the SR500 swingarm and will further reduce unsprung weight. Downside: it's 2 inches longer than the SR swingarm and will need to have the shock mounts relocated and a brake arm mount welded on. Using it will probably require a different rear fender as well.
Anyway, these SC500 wheels are not common, but if you can find one, it should be cheap (no demand) and is a easy conversion part.
Bill
