Handlebar M/C Conversion Kit for R75/6

[vanzen]

Do find better ratios than were ekwipt from the factory ...

"For 2 piston opposed calipers, I like ratios in the 27:1 range, feeling some line and caliper flex. For a firmer lever, use 23:1. I think ratios lower than 23:1 produce a lever feel so "wooden" as to have little, if any feel. Combine "low" leverage ratios with sticky pads, and unpredictable lockup is the result. The high effort required at the lever also results in undesired input to the bars. Single piston calipers are much happier in the 14:1 to 12:1 range. Disc and wheel diameters, as well as hand lever ratios, must be considered."

from: Vintage Brake

Sourcing later (used) parts may be a less expensive option.

[Ken in Oklahoma]

Yep, 1st year RS, converted to an S. Here's what "Sasquatch" looked like when I dragged it home. 'Cept it didn't have no handlebars nor wheels, that's why I dragged it...ain't she purty?

Yikes! So that was the S bike I saw at the rally?

[Deleted User 72]

Yep, 1st year RS, converted to an S. Here's what "Sasquatch" looked like when I dragged it home. 'Cept it didn't have no handlebars nor wheels, that's why I dragged it...ain't she purty?

Yikes! So that was the S bike I saw at the rally?

Yep.

[Ken in Oklahoma]

Yep.

Wow!



Ken

[Chuey]

I'll be listening in. My R90S feels pretty good but I wouldn't turn down better feeling brakes.

I think it's similar to mountain bike brakes. Cantilever brakes have their levers with the correct amount of pull. Then, we came up with "V" brakes and they need more cable pulled by the lever. If you put canti ratio levers on a V brake, you get a powerful but extremely mushy feeling brake. If you put V levers on cantis, it gives a very hard lever with no real power.

Chuey

[Major Softie]

I'll be listening in. My R90S feels pretty good but I wouldn't turn down better feeling brakes.

I think it's similar to mountain bike brakes. Cantilever brakes have their levers with the correct amount of pull. Then, we came up with "V" brakes and they need more cable pulled by the lever. If you put canti ratio levers on a V brake, you get a powerful but extremely mushy feeling brake. If you put V levers on cantis, it gives a very hard lever with no real power.

Chuey

Yep, same basic principle. It's all about varying the ratio of mechanical advantage. You figure out the advantage differently with hydraulics, and they are easier to transfer pressure without frictional losses, but the basic principles are the same.

Downhill bikes, and the much larger disc brakes they are running, are now experimenting with exactly these same ratio issues. The cylinder sizes are much smaller, but the ratio issues are the same.

[DanielMc]

I think there's a small matter of whether you use the early 38mm piston ATE caliper, or the later 40mm one. I believe the 13mm M/C performs better with the former and the 14mm with the latter.

[Ken in Oklahoma]

I think there's a small matter of whether you use the early 38mm piston ATE caliper, or the later 40mm one. I believe the 13mm M/C performs better with the former and the 14mm with the latter.

Both calipers will be 40mm.

At the moment 14mm would be my M/C bore of choice. I really don't want the brake lever to strike against the grip during a panic stop; nor do I want to have to keep an eagle eye on the brake lever's free play.



Ken

[Deleted User 72]

I think with the handlebar m/c there is no issue of free play. There's nothing to adjust.

[old R90 guy]

I did the motobins conversion last year. Since I have a Hannigan fairing with fairing-mounted mirrors, I asked if they could delete the included mirror (and credit me the difference) They replied that they'd send the RS/RT kit instead. I suspect that the difference in the kits is a mirror. They supply a machined fitting that essentially replaces the front of the undertank MC. On my kit the fitting had two tapped holes to connect to the two brake lines that a twin disc bike would have. They told me to plug the right-side outlet with a bleeder screw. I'm VERY happy with the conversion, but I was using a very old rubber brake line, and I replaced the brake line at the same time, so I really can't make a valid comparison. They have answered questions that I have e-mailed in the past.