The Yamaha Road Star Warrior Forum

Some of you may know this mod...., but on both my warriors, I changed the front brake master cylinder to a 2003 Road Star model. The 2003 Road Star has a 5/8" diameter piston which is about 17mm. The warrior or 2004 and later roadstars have a 14mm. The larger diameter allows single finger braking easier and may eliminate the need for steel braded lines for som epeople. I like it a lot..... It looks and fits exactly like the Warrior one. If you look on the face of your front brake fluis reservios it will say 14, indicating the size. On these it will say 5/8.

After I switched to a single front brake, my lever is very stiff but does not brake very good. I wonder if this would help or hurt.

might help... ehack. bis what did the part cost you new or used?

so you can do stoppies now *LOL*
cheers

that would be useful. thanks bismarck! []

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Originally posted by ehacker01


After I switched to a single front brake, my lever is very stiff but does not brake very good. I wonder if this would help or hurt.

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To get some of your braking back you will need a master cylinder with a bore size smaller than stock.

Larger bore cylinder = less pedal/lever movement & more input force needed to achieve a like stopping distance.

Smaller bore master = more pedal/lever movement & less input force needed to achieve a like stopping distance.

IMHO the Warrior has some of the best brakes in the industry. With SS lines & synthetic fluid my Warrior brakes are superior to my Hayabusa which come stock with six piston calipers.

YOu know church maybe right.... The lever does not travel as much thats of sure. But I do feel more braking power, maybe because the lever does not travel as much.... ?!?!

It certaily made a bigger difference on the bike without the steel braded lines. To be honest whatever the scientific reason behind it, the larger piston moves more oil with less lever movement and it helped.

I will get you the part number and price... Retail it was $176 but I paid much less, and i can get it for you folks at that same price.

I already am using the steal braided canbles...would I need to change the cables to work with the bigger master Cylinder?

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Originally posted by Bismarck

YOu know church maybe right.... The lever does not travel as much thats of sure. But I do feel more braking power, maybe because the lever does not travel as much.... ?!?!

It certaily made a bigger difference on the bike without the steel braded lines. To be honest whatever the scientific reason behind it, the larger piston moves more oil with less lever movement and it helped.

I will get you the part number and price... Retail it was $176 but I paid much less, and i can get it for you folks at that same price.

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HI guys, what brand of braided brake lines will give me th best bang for the buck?

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Originally posted by Churchkey

quote:

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Originally posted by ehacker01

After I switched to a single front brake, my lever is very stiff but does not brake very good. I wonder if this would help or hurt.

---

To get some of your braking back you will need a master cylinder with a bore size smaller than stock.

Larger bore cylinder = less pedal/lever movement & more input force needed to achieve a like stopping distance.

Smaller bore master = more pedal/lever movement & less input force needed to achieve a like stopping distance.

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yeah, that's what I thought but I have no idea where to get one smaller than what's on it now. all the HDs are 5/8, 3/4, and occasionally 11/16. Ours is a 9/16. I need to find a 1/2" bore...any ideas?

Reza,
As stated:
Larger bore larger AREA = more fluid displacement less pressure to the caliper pistons & less stopping power.
Smaller bore smaller AREA = less fluid displacement and higher effective pressure to the caliper piston & more stopping power.
Longer brake lines/hoses will cause longer stroke from the master cylinder lever to displace fluid to the calipers. Rotor runout, bad bearings or anything that repels the brake pad away from the rotors will result in more effective lever travel to pick up the additional displacement to the front calipers.
How do i know. I spent 18 years in the Undercar parts business in Hollywood, Ca specializing in just brakes on La Brea Ave

Well Gents, thanks for the insight...

Then where am I missing... Larger piston, means for the same lever movement, you are displacing more fluid, thus exerting more fluid in the brake line exiting the master cylinder. The line on both of these are the same diameter. So for ever millimeter of lever pull, the larger piston, puts more pressure on the brake pads, because the volume of the fluid it moves into the line is larger.

So more brake pressure for every millimeter of lever movement. This could compensate for the rubber brake line expansion and makes the brakes feel better. You put on steel lines to eliminate the line expansion and as a result you get more pressure for the same lever movement.

Reza,
not to be argumentative...The larger MASTER CYL bore equals more volume to the CALIPERS....hence less lever movement because of the increased displacement normally expressed in cubic inches or cubic centimeters.
The down side is that the displaced fluid will not be at as high a pressure.....thus less psi to the Calipers and a diminishing of stopping power! If you increase your brake lever length you can recoupe the losses through the mechanical advantage of the lever against the master cyl piston!
Under normal stopping conditions the brake lever will be much firmer with the larger bore master as you discribed.

Alan, No argument as I Am no brake expert.... Actually thanks for all this info... Now one question, why is it recommended on the 6 piston calipers that you go with aminimum of 17mm or preferable 20mm? Is it that with 4 more pistons total, you do not displace enough oil with the 14mm?

Reza,
yup....6 piston calipers have more cubic inches and also more force....need more fluid for displacement of pistons or brake lever will bottom out on handle bar i suspect. Probably 20mm bore is ideal balance for design of system. Remember more fluid is not more force! More fluid is only faster displacement. You need FORCE to stop effectively. With six pistons x 2 you have more area hence more force!