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Master Cylinder Ratio Chart

  • Thread starter Thread starter 8trackmind
  • Start date Start date
The single disc models had a master cylinder with a smaller bore. I tried to use a rebuild kit from a 750E once on a 750T M/C. It didn't fit. The E models seals were just a little to big to go into the T's M/C.

You could try to snag a M/C from a 750T, 550 or 450 and give it a try. If you can find the 750T's M/C it is a real nice all aluminum unit. Cast resevoir and cylinder is all one piece and the top is cast alu too.
 
I looked at my master cylinder from the bottom while it was installed this past week. Stock '83 1100E's have a 5/8" master cylinder diameter.

I bled the system at the master cylinder, which I had never done before. I did this by putting a rag under / around the banjo then squeezing the lever and loosening the bolt. Of course, I sent brake fluid flying everywhere on the first pull. :roll: I squeezed and loosened it twice to bleed it.

Initial impressions to me was that the 'woody' feeling was better. I switched bikes with my friend who rode it 3 weeks ago and he agreed it had a lot better lever feel than before.

I still want something that bites harder. I'm not sure I'm going to get there by just changing the master cylinder. Steel braided lines aren't going to do it all either, unless I'm way off. I don't feel the brake lines buldging at all now...

~Adam
 
I'll measure my master cylinders this weekend. All of them. ;-) I do love the "brick wall" feeling my GS5/650 has.
 
Nerobro said:
I'll measure my master cylinders this weekend. All of them. ;-) I do love the "brick wall" feeling my GS5/650 has.
Click to expand...

Post a picture of that fork too.:-D
(like you promised to six months ago :( )
Not really, but it seems that long.:-D
 
I have all stock braking components other than the steel braided lines and Vesrah pads. I did however replace all the caliper pistons and seals, and the master cyl piston and seal. The bike stops hard and fast, as hard and fast as I could want. The braided lines didn't seem to increase overall braking power by a whole lot, but the feel is much better. I can feel when the pads start to really grip the rotors. I could definitely do a stoppie, if not for the fear of the act itself...

I ran some kind of fancy, smancy racing brake fluid as well, and bled the master cyl. I even retained the original 5 line setup up front, and still the feel is excellent.
 
I did however replace all the caliper pistons and seals, and the master cyl piston and seal.
Click to expand...

Jethro, did you buy the parts for the master cylinder from Suzuki directly? There is no aftermarket rebuild kit available for our bikes...
 
Here is some more info for the nay sayers. Link
This is from a company that distributes stanless steel lines.
I am actually barking up the right tree here, you guys just need to think outside the box bit. :-D
SS lines may improve feel, but they don't actually increase stopping power. A smaller bore master cylinder will.
 
SS lines will decrease lever travel, a very good thing, it will give a firmer feel. The calipars on the CBX was used by honda on most of there models after '82 so calipars are pretty common. I have a spare set of the double pot honda's and I was wondering if they would fit on the GS, simple to find out.

One way to help the braking power is to increase the size of the pads. That is why I have the Double pistons that will (someday) replace the single pot's on my CB900C. Another option is increasing the diameter of the rotor, this will give better braking. If you don't believe me, it dosen't matter to me, Buell agrees, some of there models have a single disc in the front that bolts to the rim, not the hub.
 
quakeholio said:
If you don't believe me, it dosen't matter to me
Click to expand...
What was that all about? :confused: If I hurt your feelings, I apologize.

I'm trying to get people to consider the whole braking system. Not just the pads and the lines. :-D The master cylinder is always ignored..I know using a smaller bore master works, I'm using one everyday. I know the stock parts can be made to do a better job because I'm doing it.

As far as larger rotors, or some custom fabrication, I'm not there yet. A gsxr fork swap would make better sense if you wanted to go all out , but you give up the look (and the wheels) of a stock GS.

If anyone is looking to improve their stock GS brakes. At least consider using a smaller bore (14mm) master along with the standard ss lines and decent brake pads. (which I never questioned)
 
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Now... there is a problem with smaller bore master cylinders. Scarily enough, it's possable to have to small of a master cylinder. For instance the stock master cylinder on a single disk GS550 won't move the calipers on a GS850 far enough to contact the disks, much less brake. The master cylinder off a seccond gen 550 will but the feel is off due to most of the lever travel being sucked up moving the pads. Though... it's easy to lock up the front tire. :-) My 80 550 is running 650 calipers with the stock MC.

I still need to get those measurements I promised....
 
Nero, you are right in what you said, but it's because you were moving calipers designed for two calipers (two pistons) to a bike with one caliper (one piston)

The ratio goes to hell at that point!
 
Bump to this topic....I've now had some experience with it to add a few comments.

While the brake work I did on the stock master cylinder, calipers, and stainless lines on the 1100E resulted in a nice firm lever, I still really never liked the feel.

This past winter I redid the entire front end on my '71 CB500F (both brakes and suspension) because it was shot. Based on my experience with the GS, I knew I wanted to use the stainless steel lines and Ferodo Platinum pads, but I wanted something different on the master cylinder, because the 'on/off' wooden feel of a large bore master cylinder is no fun.

I found a new aftermarket replacement master cylinder for a Kawi EX250/500/KLR650 on Ebay for a song, $40. I checked and the those Kawi bikes all used a single rotor brake system, so I knew I'd be very close with my CB500F, because it's a single disc too. (What I did not know is the caliper side for the EX500.)

I lost the email with the Kawi EX250/500 master cylinder bore size, but it's near 1/2" or slightly smaller and I imagine it will work fantastic on any single piston / caliper GS.

The result? Fanastic brake feel. I have to pull the lever a bit farther than before, which was almost scary at first (thought I had no brakes!) but once you're on the brakes you can adjust for ever so slight braking to full stopping power. It's awesome.

I encourage this upgrade to everyone, but it is going to require some work on your part to find the appropriate ratio to target and then the right master cylinder. Micheal Moore from Vintagebrake.com is a great source of info - call him up.

aod-71-honda-cb500-winter-bike-work-2008-011.jpg


aod-71-honda-cb500-winter-bike-work-2008-012.jpg


aod-1971-honda-cb500---new-paint-03-16-08-003.jpg


~Adam
 
Good job Adam!
I gave up on this thread a long time ago. Kind of gets old when everyone parrots the same SS line, brake pad song over and over. I guess it's hard to look at something old in a new way.

Heres where I ended up.

DSCN2447.jpg


DSCN2446.jpg

DSCN2445.jpg

DSCN2444.jpg


It's running Galfer SS lines from a Kawasaki ZG1000, sintered metal brake pads and a 14mm bore master cylinder off a single disk bike. It has very little lever free play and stops great.
I have at least 10,000 miles on this mod now, so anything that was going to fail, should have done so by now.
 
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Cool brakes but that lower strap & spacers scare the crap out of me!

As for brakes this is all pretty well-known stuff. Any of the race car design books can walk you through the calculations.

Deceleration speed in gs is brake force at the contact patch times the tire's coefficient of friction at the road times area of the contact patch times tire lateral load (including the effects of weight transfer).

Brake force at the contact patch is pad friction times the diameter of the midpoint of the pad swept area.

Pad friction is pad friction coefficient (mu) times pad pressure.

Pad pressure is hydraulic pressure times area of pistons.

Hydraulic pressure is braking force from your hand times the lever ratio times the master cylinder piston area divided by the caliper piston area MINUS flex in the caliper mount, master cylinder mount and lines.

So assuming the same amount of "squeeze" from your hand:

Larger disc rotor: more brake force
Larger pad (radially): more brake force
Larger pad (circumferentially): less brake wear (no effect on stopping power)
Stickier pad: more brake force
More caliper piston area: less hydraulic pressure
More master cylinder area: more hydraulic pressure
Stiffer calipers: less wasted movement
Stiffer lines: less wasted movement
Stiffer caliper mounts: less wasted movement

Most people don't realize that multiple pistons are used to keep the disk rotor temperature more consistent across the surface as well as keep pad wear even. They allow you to run more piston area within the same pad width envelope.
 
You could have someone mill a nice flat bracket for not a lot of money. Use 6061-T6 or stainless steel if you want to make it really bulletproof. Or you could probably make it yourself out of a flat piece of stock and a drill press.

It's just that the more rigid the caliper mounting the better. Since the upper mount + spacer are not tied to the lower mount strap there is a lot of room for movement. The spacer gives the caliper a lever to bend the strap since the two mounting points are not in the same plane.

Add to the fact that it appears to be a piece of 1/8" CRS which has all the fatigue resistance of a coat hanger wire, you have a recipe for cracking.

I'm pretty anal when it comes to brakes but I understand that everyone has their own risk tolerance/pursuit of perfection level.


8trackmind said:
Come up with something better and I'll use it instead.
Click to expand...
 
robertob said:
You could have someone mill a nice flat bracket for not a lot of money. Use 6061-T6 or stainless steel if you want to make it really bulletproof.
Click to expand...

I haven't had any problems so far but...If it needs to be stronger, then I need a better bracket. Can you make one?
 
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8trackmind said:
I haven't had any problems so far but...If it needs to be stronger, then I need a better bracket. Can you make one?
Click to expand...

I could but only after I make mine :) I appreciate your work finding the calipers. I think Dan (salty monk) is doing the same conversion...
 
robertob said:
I could but only after I make mine :) I appreciate your work finding the calipers. I think Dan (salty monk) is doing the same conversion...
Click to expand...

Next question: Would you make 'em?
I can give you the measurements. I'll even volunteer to test them for you. (since I seem to have no fear whatsoever)
 
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