[Northwind]

Specifically, a 99-02 SV650S and Y-K2 GSXR 4-pots, standard pads, EBC Prolite discs, HEL braided lines. I did the swap a while back and brake performance is better than stock but still pretty weak considering the hardware involved. I'm 99% convinced that it's the MC that's giving me problems, just wondered if anyone else had managed to get a satisfactory result using these parts, before I buy a new MC...

I'm pretty satisfied that the brakes are properly bled, and they don';t have the feel of badly bled brakes. I can't swear that the pads and disc aren't contaminated but I'm fairly convinced that they're not. Seals seem fine, no leakage anywhere.

 

[andyauger]

Two factors

There are two factors in a master cylinder that determine how it feels. The first is the cylinder bore, the second is the linkage geometry.

I don't know if the bores of the two are the same. If they are then that's one issue out of the way. If they aren't there are two scenarios. If the GSXR has a larger bore then the SV cylinder will have to travel further to engage the brakes but will require less pressure than the GSXR cylinder. If the reverse is true then the SV cylinder will require less travel but more force compared to the GSXR.

The linkage is the next consideration. You can figure this out with a compass and ruler. Measure the distance from the lever pivot to the piston pivot point both axially (in line with the cylinder bore) and perpendicular to the cylinder bore on both setups. With the compass you can draw the "path" the linkage takes. With a bit of trig you can figure out if there is a big difference between the way they travel. On most masters it doesn't make much difference where the lever is in its travel.

I always wonder about posts like this. You can stand the bike on its nose or lock up the front wheel with the stock brakes. You may have some other problem contributing to the lack of braking force (too-high expectations or weak hands, maybe, no put-down intended).

 

[Northwind]

Re: Two factors

I always wonder about posts like this. You can stand the bike on its nose or lock up the front wheel with the stock brakes. You may have some other problem contributing to the lack of braking force (too-high expectations or weak hands, maybe, no put-down intended).

And of course, whether or not you can lock the wheel is all there is to brakes, isn't it :roll:

To return to the topic, can anyone with relevant experience rather than a willingness to talk about something they've never tried tell me if they've found similiarly underwhelming braking performance with a similiar parts combination?

 

[TWF]

it should work fine.we have it on couple bikes without problems or weak brakes.

 

[Northwind]

Ah, a little clarification- they're not weak, I said weak performance- should've been clearer there. They stop me very effectively, but there's a lot of lever action needed, and they're not very progressive. I could be perfectly happy with them as they are, if I'd not ridden a thou with the same calipers and felt how much better it was- again, no more powerful but much more responsive, and they had a much more linear, progressive response.

So, you'd say that's untypical of the setup?

 

[andyauger]

Just trying to help

You misread my post. You didn't explain your issues.

If your issue is long travel then I would guess that the GSXR bore is larger than the SV bore. Hence longer travel and probably some slight mushiness or elasticity.

I must say that if you are not absolutely sure that a particular brake setup will work, don't install it. Brakes are too important to experiment with.

 

[andy4us]

I ran Ferodo CP-911 race pads, stock rotors, braided lines and SV master. Felt great, lots of power and very progressive, and at least 20% shorter stopping distance from 80 This was with 2000 GSXR 4 pad calipers on 750 forks. I switched to the Brembo 19*18 radial .... awesome feel, you can do it all with one and sometimes two fingers. IIRC both the SV and older GSXR MC's are both 5/8" bore. Not sure about the newer GSXR radial MC.

If the stock pads came with the calipers, I would consider a set of new pads first. The pads which were in mine were decidedly dodgyas far as condition. I don't think the breakers pay much attention and get brake fluid on the pads etc.

Andy

 

[jimsv650s]

Ah, a little clarification- they're not weak, I said weak performance- should've been clearer there. They stop me very effectively, but there's a lot of lever action needed, and they're not very progressive. I could be perfectly happy with them as they are, if I'd not ridden a thou with the same calipers and felt how much better it was- again, no more powerful but much more responsive, and they had a much more linear, progressive response.

So, you'd say that's untypical of the setup?

I don't know if it's typical but, I understand what you are saying and mine feel the same way. I really don't think it's anything to be concered about. The stock master just isn't designed to give the best response for this system (Like Andy is said).

Like Andy said, to get increased response, we'll have to swap the master. I'm sure TWF and others can point us in the right direction when the time comes.

 

[TWF]

Ah, a little clarification- they're not weak, I said weak performance- should've been clearer there. They stop me very effectively, but there's a lot of lever action needed, and they're not very progressive. I could be perfectly happy with them as they are, if I'd not ridden a thou with the same calipers and felt how much better it was- again, no more powerful but much more responsive, and they had a much more linear, progressive response.

So, you'd say that's untypical of the setup?

answer is simple but comlicated .it can be any part of braking system including master that is not performing right.like I said,master should work fine as is been working fine for me on more than one bike and different set up.
I can't give you answer which exact part may not be performing,you have to check all and figure.
once you try brembo nothing stock is good any more :lol:

 

[Northwind]

Re: Just trying to help

You misread my post. You didn't explain your issues.

You're right actually, I owe you an apology for that... I didn't explain the problems I was having well and I only saw where the misunderstanding came from after Zoran's post. Still, one thing I think I was clear about is that the brakes still stop me more effectively than the stock ones- just not as effectively as they ought to. Long travel's not the only issue but it's one of the easier to quantify ones.

Thanks for all the input folks. The logical suspect would be the pads or MC at this point, I think... Or some combination of the two. I suppose I shouldn't rule out contaminated brake fluid either- it was from a sealed container on a hot dry day but stranger things have happened.

I've cleaned and deglazed the pads that came with the calipers but that's no guarantee of condition at the end of the day. I think a new MC of some form is definately on the cards, since to settle for adequate performance after going to this length would seem to me to be a bit of a waste.

The main point of this post was to establish whether I have a spec problem or a setup problem, to which the answer seems to be "maybe"

 

[mstingray]

IIRC, aren't they both nissin 5/8 M/C for both the stock SV and the older gix'? i'll do a quick check but i'm pretty sure they're the same ones.

 

[Northwind]

May well be. I rebled the system and got a better result, but still found it to be really non-linear- Bit of brake, bit of brake, lots of brake... Which I hated to be honest. So I picked up a cheap Brembo radial Fitted it yesterday, and what a difference. I've got some clearance issues- at full left lock the span adjustor fouls the fairing, and forces a bit of a ropey angle on the lever- but I'm hoping when I fit the higher bars that should stop being a problem.

Delighted