Front brake size

[ShawnD]

Does anybody know the master cylinder bore & ratio? I know the bore is 16mm but radial masters are designated 16xXX, second figure being the pivot to plunger distance. The best I can come up with is 20mm but I really would like to know what unit Yamaha decided to use & I cannot find that info anywhere. Giving some thought to putting a Brembo 15RCS master on.

 

[one2dmax]

It should be cast into the master body. I don't remember the gen 2's but the gen 1's were 5/8"

 

[ShawnD]

It only shows the bore size.

 

[Fire-medic]

It should be cast into the master body. I don't remember the gen 2's but the gen 1's were 5/8"

Yep, and 5/8" =15.875 mm so you're only 0.125mm away, call it a nominal 16mm, not sufficient a difference to make a critical difference in braking feel/performance. Call it a 'blonde-hair's' difference.

 

[ShawnD]

Yeah, 5/8 and 16mm is no real difference but the pivot to plunger distance is what's going to make the bigger difference. Most axial masters I've measured were 25mm but I've seen some old bikes with it stretched to 30mm. A 20mm pivot will give a 25% increase in ratio over a 25mm pivot, 18mm pivot gives 39% increase.

 

[ShawnD]

Just a quick update, I did put a Brembo master on this past weekend. Went with a 15mm bore with adjustable pivots, 20 & 18mm. Stock ratio is 13.5:1. With the Brembo set on 20mm pivot it's 15.4:1 & on the 18mm pivot it's 21.4:1. There's no room left on the lever adjustment, it's at it's max reach but I haven't ran out of travel so far. Much better braking.

 

[one2dmax]

What's it do for the lever effort?

 

[ShawnD]

What's it do for the lever effort?

It's less effort. I should probably mention this is with a shorter lever also.