Braking question?

gentlemanjim

gentlemanjim

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In a previous post I metioned the poor braking on my bike. I have a resurfaced and cross drilled single rotor. It takes a healthy squeeze to stop. I'm running a GSXR rear master cylinder with stock rotor/caliper and it seems to take a lot of force as well. In previously owned XS650's I don't recall it being an issue, but that was a long long time ago. I wonder if it is the MikesXS brake pads that are the problem. Anyone have experience with these pads good, bad or indifferent?
 
They're average. Stainless steel is just not optimal as a braking surface. I'm pretty sure you can get a more aggressive pad, but i'm not sure where from.

I have an 80 with rear disc in my garage, and it's way less effective than my 78 with rear drum.
 
I have the stock rear m/c on mine. I have a slotted rotor. This works good.
On the front I have two slotted disc, two stock single piston calipers and the 14 mm m/c came from an 82 special. I have Mike's braided lines hooking them all together. These work good too.
I bought two sets of Mike's pads. I put these on the front. Picked the two best looking pads of the bunch of used ones I had for the rear.
All my brakes work very well.
You are using a GSXR rear m/c. What is the bore size?
The stock one is 1/2 inch.
If the GSXR is larger it will feel wooden as some call it. The pedal will push hard and when you finally push hard enough the brake locks.
If it's smaller, the pedal will push easier but you may not be able to push the pedal far enough to get the brake to work.
 
Took about 100 miles or so for my Mike's pads to feel even acceptable. Single disc front and rear. Never rode the bike before, but my 80 GS450 seems to stop better.
 
I am part way through the overhaul of the front brake. Everything worked fine I just couldn't bear thinking of that 30 year old fluid and inevitable build up in there. Slides, piston and caliper were perfect just the usual old brake fluid crud. No rust. original pads with 70% plus remaining with no fork oil contamination.
 
I was hoping the pads will brake in after enough stop and go cycles and get a better bite. I've always used EBC- HH pads in the past. If these don't improve I try a set of them. If they don't improve braking I'll learn to live with it.
 
Check with Michael "Mercury" Morse over at Vintage Brake -- vintagebrake.com. He's an XS650 wrench and racer from way back (also owns 650 Central).

Anyway, Mike knows his stuff when it comes to getting our XSes to stop right. The biggest problem with the front brake on the XS is the master cylinder bore is too large. Going with one with a bore one size smaller helps a lot. He has a chart at his site that gives you info on the optimum MC bore sizes depending on caliper piston sizes. This info can be used for the rear disks also, although I don't happen to know about availability of different sized rear MCs.

Mike also sells pads with good material. I've been using his Ferodo Platinums on my bikes, and am satisfied with the performance. I've also had good luck with SBS pads, which I don't think are quite as aggressive as the Ferodos.
 
With new "braided" lines you should be able to go smaller and still have enough volume to fully apply the brakes before the lever hits the bar. Just finished a "full" overhaul of the all stock 81 Special, good lever feel now, it was fine but 30 years allowed a lot of gunk to collect. Ride report after lunch break (brake).
 
Lunch over (burp) Brakes are fine, no major change, a bit stiffer lever very little "sag" still the stock brake lines too. As a comparison the brakes take about the same effort and have similar feel to my 1100 Shadow.
 
So if read the below chart correctly, my single 38mm piston with 13mm Magura master equals a ratio of 8.54:1 which puts me in crap ratio correct? An option will be to add a second caliper (which I have) but still puts me in a 17.9:1 or just get a 11 or 12mm master cylinder and should put me closer to the sweet spot right? I have almost no lever travel when I brake right now.

mastercylinder.gif
 
Maybe a difference between years? In 77, wasn't it, Yamaha went to a newer style caliper. But even 35mm with a 13mm MC bore is awful. Worse than a 38mm with 13mm bore.
 
Your measuring where the dust cover hooks on, the piston is bigger inside the caliper.
I think that chart applies to front brakes. I don't know if it would work for rear brakes.
If your front brake has a 14 mm m/c and one single piston caliper it should work ok, that's how the factory did it.
If you read what MMM says above the chart. A 12-1 to 14-1 ratio works with single calipers. A 10 or 11 mm m/c with you single piston caliper. I think the sam 12-1to 14-1 works with the dual single piston clipers.
Dual piston dual calipers In the 27-1 range.
With your 13 mm m/c a dual front set using two single piston calipers will work. This is real close to what I have. My m/c is 14 mm. Should work great.
At this point you can add a second caliper which adds weight and gives good brakes and some say loose a bit of handling.
Or get a smaller m/c. This will handle the same as what you have and still have good brakes.
On your rear brakes, have you figured out the GSXR m/c bore size?
 
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The master cylinder on my 1975 was rusted and shot, so I ordered one like this with a 14mm bore for half the cost of a rebuild kit:
http://cgi.ebay.com/ebaymotors/FRON...rcycles_Parts_Accessories&hash=item19bd21b62c

I don't know what the original M/C bore was, but the calipers are 48mm. It has the two caliper, non-floating style. What's the correct term for this type of obsolete caliper?

Can anyone give me an idea of what ratio I'm dealing with. 14mm M/C with two opposing 48mm calipers pistons.

The bike will still lock the brakes eventually, but it has a huge amount of lever travel. It makes me wonder sometimes. :yikes:

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Also, I couldn't find anyone local that could turn my rotor, so I attacked it with the random orbital sander. Started with 50 grit to get rid of those old grooves and worked my way up to 220, rotating constantly. Some things I've read say to stop at 120 grit but that seems pretty rough to me. I know that some crosshatching is good to deposit brake pad material on the metal, any ideas?
 
I have never gone that fine, then again I don't try to get all the grooves out either. I hit it with 80 grit in the DA or by hand and call it done.
Maxim disks XS650 alloy spoked wheel, I am welding a 650 stem into XS750 triples to put the 750 legs on a 650 frame.
XS650 disk 6.5 pounds XS750 disk, 5.4 pounds, Maxim disk 3.75 pounds.
brakes 014.jpg
 
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