Yet another 6-pot caliper upgrade thread

[noobcorpse]

Ok so I suck at searching, but after trying different variations of "hayabusa", "brake caliper", and "brake upgrade" in the sprint forum, I'm not finding the good threads that I know are out there. Basically, can somebody help me by either linking me to the FAQ/How-to/Parts List threads, or answer these questions:

1) Besides the Tokico (busa) 6-pot calipers, brake pads, and brake fluid/bleeding equipment, what other parts are needed for the upgrade? (presuming my 07 sprint ST ABS has the 5/16 MC)

2) How do I verify if my bike has the 5/16 MC? It's an 07 w/ ABS, and I am pretty sure it does, but I want to make sure.


I've had my sprint for over a year, and have almost 12k miles on it.. It performs great, but the front pads are getting old, and I'm really tired of the weak braking, especially after riding other bikes with phenomenal brakes. I'm looking at doing this conversion in the next couple weeks - I've had enough of the stock calipers.


Thanks in advance.

P.S. - please don't kill me OnD, I swear I really used the search before posting this.

[TornadoST]

The only other thing you might need is a seal kit for the calipers, depending on condition of the ones you find. Just remember not to let the master cylinder run out of fluid while you are bleeding or you will probably have to take it to a shop to bleed out the ABS system. It is a painless install and you are going to love the difference that the brake upgrade makes.

[oldndumb]

noobcorpse, where ya been? Haven't heard from you in a while.

TornadoST mentioned a seal kit. In my mind that is extremely important advice!

Your master cylinder size is on the back side of the casting.

I understand some people changing over to get rid of the 'spongy' brake syndrome, but I've never known the stock calipers to be described as low on stopping power. Mine will make the rear come off the pavement with no problem. I suspect your 'weak braking' is a function of your pads, not the caliper efficiency.

Considering that you have 12k on the bike, have you checked your rear pads lately?

[CLB]

I found that HH pads help. I tried organic first and was disappointed.

I swapped in 675 pistons 8000 miles ago and have been happy with the lever feel since.
I would like a little better hydraulic leverage.

To that end I picked up a low cost (and cheap) pair of 6 pots on eBay, thinking that these would have more piston area.
On arrival I was greeted with crash damaged castings, rusted pistons, torn seals, and corroded hardware. I pulled them apart, priced rebuild parts and sent them to recycling.
Be careful what you buy on eBay.

Next purchase was a 675 M/C. It was in good shape. I don't know how the leverage compares. I like the looks of the part. The linkage from lever to piston eliminates the rubbing and side loading inherent in our M/C's. It should be a bit more efficient with better feel. The problem is that the brake line wants to exit to the left (theough the handlebar casting). You could machine off the positioning nubs for the hard line but they are there to prevent the plumbing from getting bumped loose.
So...

I would be willing to try a 14mm Sprint M/C if one could be had for what it's worth (pretty close to nothing). It should work fine with the coated pistons in the calipers.

Or... put more effort into the 675 M/C.

[noobcorpse]

Sorry I haven't posted in a while. I usually read a few threads but then I see all the goodies I want to get for my bike (Trident, Pazzos!) and I have to leave before I spend money.

I'm going to try a set of Galfers before switching out anything, but the main reason the caliper upgrade interests me is the reports people post here of overall improved braking feel and strength. The stockers have decent initial bite, but they seem to grab and that's it - there's nothing more beyond that - there's no feeling of progressive braking strength as you squeeze the lever harder. But, I want to try a set of new pads before I make the full switch.

As for seals - I'm looking to order a new set of the calipers from a parts place, so everything should be in new condition, unless i can find a like-new or decent set locally that I trust will be in great condition.

Edit: If I'm looking at the correct area for the MC (under the fluid reservoir, and to the left of the front brake cable? it says "Nissin" on it?), I see a "5/.." on it, so I think that's my MC size..

Rear pads: Just had them changed last month - the rears were starting to grind a bit, since I use the rear often, and I put in a set of galfers and they grab well.

Thanks all for the responses, I appreciate the help.

Originally Posted by oldndumb

noobcorpse, where ya been? Haven't heard from you in a while.

TornadoST mentioned a seal kit. In my mind that is extremely important advice!

Your master cylinder size is on the back side of the casting.

I understand some people changing over to get rid of the 'spongy' brake syndrome, but I've never known the stock calipers to be described as low on stopping power. Mine will make the rear come off the pavement with no problem. I suspect your 'weak braking' is a function of your pads, not the caliper efficiency.

Considering that you have 12k on the bike, have you checked your rear pads lately?

[KevyKev]

That's probably the 5/16 MC then. I know that the 14mm one had a 14 within a circle embossed on the casing. For what its worth, I agree with your comments completely on the brakes. I have got the goodwill switch to the 5/16 MC, but still agree with you. Since OND and everyone seems to agree that rebuild of salvaged Busa calipers is necessary/advisable, I think I will eventually just rebuild the stockers with the 675 piston kit/seals as that seem to work really well.
Kevin

[NotSoFast]

noobcorpse-You might want to check my thread on changing to a Brembo m/c. It has much more progressive feel than the stock 5/8 m/c. The thread is here http://www.blogto.com/tno/2008/04/di..._the_real_man/ if you are interested. Good luck with the project.

[MuzTheInfidel]

Okey Dokey.... I'll chime in here because I've done the mod and understand the reasons why I and many others have done it.. some points follow:

1. STOPPING POWER
There may or may not be an increase in stopping power to be had. I noticed a light improvement but this will (more likely) have been a result of the PADS that came with the 'Busa calipers. No, I don't know what they were - I'm a cheapskate.

2. THE REASONS WHY
I keep on hearing the word 'spongy'. The 'Busa calipers will do nothing for 'spongy' brakes. If they are spongy, you have air in them or there's a leak which you will see direct evidence of. The lines are braided, so they cannot be blamed for any form of poor performance.
The real reason is Triumph's el-crappola cheap non-low-friction-coated caliper pistons. They 'stick' a bit, and the result is the brakes taking up at a different point each time you pull the lever in. It feels like you're 'pumping' them up as they will take up sooner after you've applied them once already. Seems this wasn't a problem on the earlier Trumpets.

3. BLEEDING
Unless you're a Bank Johnny (bank teller type), do it yourself. The ABS is fine if you keep the MC wet (the opposite of dry).
My method which was passed on by the best mechanic I know, requires two people. One does the brake lever and the other does the bleed bolt(s). Get some 6mm clear tube & run it into an empty jar. Pop a ring spanner onto the bleed bolt and then slide the tube over the end. Crack the bolt, squeeze the lever, tighten the bolt, release the lever. Repeat until NO AIR comes out for maybe a dozen applications of the lever. Move to the other side & repeat the procedure. Some people will apply lever pressure before cracking the bleed bolt, but some say that doiing it that way can push air into nooks & crannies - I have NO idea about that, but this way works for me and is painless.

4. THE JOB ITSELF
An hour and a half maximum (including some rum [Bundaberg Rum of course] & Cokes). Delete the alcohol if you want to test your new brakes straight away. The std. hoses & routing remain, I re-used the Triumph banjo bolts and everything fitted up perfectly. Make sure you give the new calipers a birthday and use an approved grease (lightly) on the bits & pieces when they go back together.

Oh, you're welcome,
Muz

[oldndumb]

Muz hits the target again!

As he says, the culprit is the stock pistons. The fix is another caliper, or a piston swap.

Radial master cylinders are pretty, and I would probably opt for one if I had to replace mine, but I would not expect any noticeable functional improvements, other than the increased range of adjustments.

As for braking efficiencies, that is more a function of the pad and rotor material and condition, and more so the tires than the master cylinder.

But, for those that are contemplating a radial MC, you need to consider a few fundamentals.

The bigger the bore, the less pressure there will be for a given lever force. Conversely, a smaller bore will produce a higher pressure from the same amount of force. A bigger bore needs less stroke to move a given volume of fluid, while a smaller bore needs more stroke to move the same amount of fluid.

So, the bigger the bore, less stroke but more force will be needed to reach operational pressure. While, the smaller bore will need more stroke but less force to reach the same pressure.

The average riders' perception of 'brake feel' is a compromise between those characteristics, and is what a brake design engineer tries to quantify.

Before anyone gets outraged and thinks I am denigrating radial master cylinders let me say that I like the high tech look of them and the fact that the good ones can be produced with larger bores, have more adjustments, and provide for pivot length selections.

But they ain't gonna make your bike stop any faster.

[NotSoFast]

I agree with what OnD and Muz have said. Braking systems are just that, everything has to work properly to be effective. I think that part of my problem was the EBC organic pads I had used as replacements for the stock pads. The DP pads seem much better.

The Brembo m/c is 16 mm, the equivalent of the 5/8". The end result is not more braking power, as OnD says the stock brakes are very powerful, but the new combo is much easier to modulate, much smoother initial "bite" and is just as powerful as the stock brakes.