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Discussion Starter #1
I planning on replacing my master cylinder and have a couple options right now. A Brembo radial is not currently an option. It will be used a SRAD GSXR-600 4 pot calipers.

1. 2003 RC-51 - $65 shipped

2. Ducati 900 SS - coffin style - $75 plus shipping

3. SRAD GSXR-600 - free
 

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Can't advise you on the specific cylinder, but the technical things to watch out for are the cylinder bore diameter and the lever geometry. If the replacement cylinder bore is larger than the original, braking effort is higher but the lever feels stiffer and has less travel in use. If the new bore is smaller braking effort is less but the lever feels less stiff and travels further.

Geometry, of course, works the same way. How far from the pivot point is the contact with the plunger? Moving the plunger further from the pivot has the same effect as increasing the bore. Moving it closer has the same effect as decreasing the bore.

This can all be calculated. If they're all pretty close, go with free.
 

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RC51, I reckon... The SRAD one is, I think, the same as the one you have now. I know DucOwner's recommended the RC51 MC before, I was looking for one before I found my $80 Brembo radial ;) Over here though, the 2 versions of RC51- the SP1 and SP2- have difference MCs, the SP1 (original) is a way cheaper item.

On that subject, don't fixate on the big bore and stroke Brembos- I picked up one that they spec for a supermoto with a single caliper as a purely speculative thing, since it was cheap, and it works very nicely. The build quality etc is the same as the big boys and while you get a lot more lever travel I've not found that to be a problem, I quite like having the large range in fact. I mention this because these ones are always far cheaper- the sportsbike boys want the latest, biggest one they can find.
 

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Forgot to mention above:
The longer the stroke to engage the finer control you have over braking.
The shorter the stroke to engage the coarser control you have over braking.
 

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Discussion Starter #5
Northwind said:
Over here though, the 2 versions of RC51- the SP1 and SP2- have difference MCs, the SP1 (original) is a way cheaper item.
Cheaper as in quality or cheaper as in price?
 

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Both :) I rode an SP1 a while back and the brakes weren't amazing- good, but not fantastic. The calipers are the same, I think, so I'd presume the rep for good brakes would come from the m/c. Bear in mind thre's no guarantee you got the exact same models though.
 

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I've gone from the original SV one, to a late-model Gixxer, to an RC-51, to a Brembo radial 19x20. There's no comparison, the Brembo is hands-down much better, and the RC-51 is a distant second. The bore diameter is a personal preference issue, not a situation where one is inherently "better" than the other. I find that I have better feel and control on trail-braking with the larger diameter bore that requires more lever pressure to stop (this is all relative, "more" pressure than the 19x18 Brembo, it's still 1-finger braking). With the larger bore, it's not that you can't modulate as well, you're just doing it with pressure instead of lever travel. I find that better for me, some other people prefer the longer travel to modulate with. Neither is right or wrong, it's all what you like.
 

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Discussion Starter #8
I should mention that the Brembo that's available is conventional, not radial. I'm not sure how much of a difference that makes...
 

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There is no difference in function between a radial and conventional master cylinder. What makes a difference is bore, pivot-to-plunger centerline distance, and effective lever length (measured from the pivot point again). The rest is marketing, like premium gas.
 

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Discussion Starter #11
andyauger said:
There is no difference in function between a radial and conventional master cylinder.  What makes a difference is bore, pivot-to-plunger centerline distance, and effective lever length (measured from the pivot point again).  The rest is marketing, like premium gas.
The materials used and the actual construction of the unit also come into play. The less flex there is in the unit the more of the power you putting into it will reach the brakes. I can see how a radial design would be stiffer than a conventional design, plus, new designs tend to be of the radial orientation and I'm sure incorporate other new technologies as well, material or otherwise.

Beyond that, we don't know those exact measurements for these master cylinders, and even if we did, we wouldn't know which numbers give the best feel and power. However, someone can say "Yeah, I tried that mc and it felt better than that one", which is all I'm really looking for. That will allow me to make a better decision than just blinding buying something.
 

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Go with the SP2 RC51 type 2002~current. It works well and is usually not hard to find. If you can find an 04~ GSXR600/750 master those work well also. In the end it's hard to beat the Brembo radial type, they are awesome. :D
 

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Much of what Zoltan said is correct. A quality "normal" master will be better than a cheap radial. Stiffness matters, but again radial arrangement offers no inherent stiffness. This is one of those questionable marketing deals. Even "radial" calipers are mostly hype. If you look at the way you have to mount calipers on the forks you cannot have radial calipers. There is always an offset between the rotor and the caliper and mounts relative to the axis of rotation. Stiffness is more important, and again, "radial" mounts are not inherently stiffer. The original goal was to reduce weight on racing bikes. Many street radials are heavier than "normal" setups.
 

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I think there are a couple of things getting mixed here.  Radial m/c are better because you get a better stroke on a larger diameter piston.  Stock SV/Old SRAD/TLR master cylinders are all conventional 5/8 bores, TLS/Newer 4 pot Gixxers before the radial brakes had 14 mm bores.  The Brembo 19 X 18 is a long stroke on a big piston and it gives better feel and you move a given volume of fluid with less travel than the stocker, since the piston displaces more fluid per unit of travel.

If radial m/c's were not any better, the GP guys wouldn't use them.  I also like that I can vary the stroke of my PVM m/c on my TLR to 15, 20 or 24 X 20mm and it is awesome compared with the stocker. You get what you pay for. 

Click picture for a big 'un

 

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DucOwner said:
If you can find an 04~ GSXR600/750 master those work well also.
a lot of people complain about those(Kris for one)... I have it on my bike(02 750 forks) and lever pull feels weird sometimes, like sometimes its too soft and sometimes its perfect... regardless of how much I use the brakes. It just seems totally random.

After reading about others experiences with them it's making me think I should go with a different mc like previous gen gsxr or the rc51 mc :-\
 

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Josh, Ive heard that from a couple of people now. It could be a design issue? Previously I used a RC51 SP2 type before switching to the forged Brembo GP MC. It worked well and was very consistant. That was with GSXR 4 pots and 320 mm rotors, both stock and wave type. No issues at all. Easy to modulate, good firm feel at the lever.

On my race GSVR700 right now I have a forged Brembo GP x20 with small diameter steel hoses ATe Superblue fluid with 4 pad radial calipers & Vesrah race pads on 300mm wave rotors. This combination allows me to brake hard enough using 16.5 Michelin C2M type slicks to carry the rear wheel in the air from top speeds with only one or two finger pull. Easy to modulate and more power than it really needs. Awesome for trailing into a turn a little hotter than normal. ;)

I believe brakes are sorta like shoes. You gotta get them so they fit you correctly and you are comfortable with them or they are no fun or even painful.
 

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This is the last post I'm making on this topic. You can take a standard design and give it the same bore-to-stroke ratio as a radial. If you can find a standard cylinder with similar bore and geometry it will feel the same as a radial. GP riders are using the radial masters because they are lighter. The layout of the radial is such that they can be made with less metal.

I'm not saying you should not buy a radial master, I'm saying that just because it says "radial" doesn't make it inherently better. Anything you buy from Brembo, for example, is going to be top class, radial or not. I'd take a Brembo "standard" over a cheapie radial any day.
 

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Why go with a radial master cylinder? The GSX-R 600/750 from 2001-2003 also have a 5/8 master cylinder for their 4 pot calipers. Or am I missing something here? ;D
 
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