Master cylinders... educate me

We'll have to get Fred to decide on this, but the overall consensus seems to be that the plunger needs to be perpendicular for it to be considered a "true" radial.

Then why doesn't everyone run them?

 

General concensus is that from start to finish the master cylinder components MOVE radially from the pivot point...

Calipers on the other hand are MOUNTED radially from the axle...

Luis

 

As long as the plunger moves in the same direction as the lever pull, it is a true radial master cylinder.

 

hope this helps clear this up

http://www.oppracing.com/pages/articles_brembo_master_cylinders/

and doesn't just add fuel to the fire.

 

Ok...my use of the word "true" is a bit poor admittedly.

 

I wouldn't say poor.

I use these R6/R1 masters and have been satisfied with them, but I know there's better out there. I can tell ya first hand they don't come stock on Ducati's either.

 

By the oil channel within the M/C, I was thinking of the channel the piston pushes fluid through (behind the piston at the end of the piston bore), not the piston bore itself. Assuming all Brembo M/C's use a 3mm (for example) pressure channel then the larger piston (19 versus 16) has a much greater pressure potential.

Using your fluid capacity example, M/C's are graded by the amount of fluid they're able to compress (based on the capacity of fluid withing a braking system i.e. the bigger the caliper pistons and galleries, the more fluid the M/C must be capable of moving). So doesn't this also then mean that by fitting a M/C meant for a much larger system (i.e. Brembo 19x16 on OEM GSXR calipers) the M/C only needs to work at a fraction of it's potential, meaning it is much more (over)efficient in that context.

I use a Brembo 19x16 with my stock GSXR calipers and the lever pull is not only shorter than ALL other combinations I have tried, but it also generates an exponential increase in stopping ability.

Thoughts?

 

Shorter lever travel than a 19x18 or 19x20? That's not normal. Shorter than the OEM m/c, sure. But the x16 should have more lever travel than a x18 or x20.

 

Agree!!!

The x16 moves less so it need to travel more to move the same amount of fluid...

On a side note the 19x16 are pricey... About $750.00 Because they are not forged aluminum, they are only available from billet aluminum...

I still want one... ...It's just the budget only allows for a 19RCS.

Luis

 

Perhaps I was that excited with my billet M/C I actually bled it properly, lol.

I understand the the maths behind this and agree on principle. I think the fact that it has a much higher leverage potential means I put less effort into squeezing the lever. Perhaps this has the psychological effect of a shorter lever pull etc.

BTW, I read somewhere that the travel difference between each M/C (16/18/20) is 11%. Assuming you could manage 20mm of lever pull, it'd still only be a difference of just over 2mm.

The leverage potential is that much higher that you'd fall in love by using it... Everything else would be a little lacklustre. It's probably one of the reasons why I have never seen a 19x16 for sale used.

Has anyone ever seen one for sale used?

 

I put a 06 R1 master on my 99 SV650. I have not had a break issue,since. It blow's away a 05gsxr 750 master. A 02 gsxr 600 worked aswell,but not like the production Brembo..

 

A 19x16? Once. I hesitated and it was gone. I now ride a little RS125, so I spent the last 6 months tracking down a used 16x16. I ended up having to beg for some shop to separate it from some SuMo setup they'd been trying to sell, but finally have it. The one thing that sucks with the 16x16 vs the 16x18 (not sure if this is the same for the 19x) is that the push-rod isn't held in place by a "hat" and a clip. It's held in place by a retainer, which screws into the M/C. So, if you ever crash and mess up the push rod, then you've got to send it to Fred or OPP to have them heat it up (to loosen the adhesive Brembo uses to secure it), then pay for the rebuild kit, then pay for the seals because the heating of the M/C damages the seals. So, a crash could end up costing you ~$175. Luckily, I've got a folding lever, so I'm not too worried about it.

 

For that price you better LOVE IT!!!

Luis

 

he sold the bike lol

-M- you should have swapped that MC for my RCS first...

 

At the end of the day, it's costs a less than 2 sets of tyres. If you were after my advice, I'd say hold off and save up for the 19x16. You'll be more than glad you did!

And yes... the bike is now gone but I've still got the roady.

 

When I googled for info about m/c sizes,a bbs link was among the results. I immediately knew there was going to be some great info in there.
So ,correct me if I'm wrong

Piston diameter for the same calipers:
19mm->requires less lever travel but more lever pull(strength ) for,let's say, 80 psi brake fluid pressure

16mm->requires more lever travel but less lever pull (80 psi fluid pressure)

The 19mm m/c has more initial bite (moves a bigger quantity of brake fluid than the 16mm m/c for the same lever travel) and that's the reason people think it requires less lever pull than the 16mm while the opposite is true. It also has a firm lever feel .
The 16mm has a weaker initial bite and gives more feel,it's more progressive making it better for trail braking. Spongy lever feel compared to the 19mm m/c

Pivot to plunger distance:
16mm -> more lever travel, less lever pull required (more leverage)

18mm-> less lever travel, more lever pull required (less leverage)

 

Ok after reading all of this (or at least skimming it) and having a fairly good understanding of general hydraulics and what not I'm curious to are all of these pistons located the same distance from the lever pivot? Because the distance the piston can travel seems irrelevant to me. How far it actually moves in relation to the amount the lever moves is all we should be interested in.

 

They differ. If you're talking about Brembo's then the second number (e.g. 19x18) is the distance between pivot and piston. The greater the distance the harder the feel and vice-versa. If you like little movement then go with a x20. If you like a lot then get a x16 (if you can even find one at a reasonable cost). If you can't decide then get an RCS, which lets you change the distance from x18-x20. Most people prefer a x18 or a x20...

 

Oh I thought it was a bore x stroke measurement, that makes a lot more sense. I've had a 19x20 and much appreciate the firmness over a stock gsxr MC.