Triumphrat

vertwrks · 01-18-2008

I fitted my Bonneville with the 6 pot caliper from Bella C. It was hard to bleed out but I finally got it. Then it wasn't OK, kinda mushy so I bled it again. It was good and after a long ride it got mushy yet again. So I have tried holding the caliper every which way to allow potential air bubbles that may reside in the caliper to come to the surface so to speak and have also moved the master cylinder around a bit in case there was a bubble in the banjo bolt. all to no avail and it does seem to be getting worse in that it is about impossible to bleed it so it feels good again.

I have been bleeding brakes for over 30 years and have been a professional mechanic a good portion of those years. So I finally decided to think it over. Logically if it is good and gets worse air is getting in the system. INstead of rebleeding over and over I have decided to rebuild the master cylinder. The piston kit from Triumph seems to be over $70 which seems steep but if it fixes the problem, worth it. The bike has over 10K hard miles.

Does anyone have any other suggestions I may try? Something I have overlooked or am otherwise brain dead to??

Thanks

oldroadie · 01-18-2008

I had a very mushy front brake after a line relocation and went thru two bottles of fluid trying to bleed the air bubbles out. Finally I wrapped a bungie cord around the brake handle and left it overnight, the next morning it bled out properly with minimal fuss.

MAR · 01-18-2008

I have the same 6 piston brake from Bella C. It does the exact same thing. When I bleed it , it feels good and then after some heavy use the lever seems to start going down lower and lower.
Initally I thought the banjos were leaking, but they are not. I will be really cranky if I need to rebuild a BRAND NEW CALIBUR.
I will try you advice on bungieing the lever over night.

Geoff · 01-18-2008

Just thinking out loud(on my keyboard) are you sure the stock master moves enough fluid for the bigger caliper?
G

sweatmachine · 01-18-2008

my stock m/c won't work the dual 2piston calipers of my new front end very well. It is very mushy but it does grab. Per Carlos' recommendation I ordered a Rocket 3 master cylinder. It's larger than the bonnie's but looks almost identical. I'm going to install it this weekend, I'll post some pics and a full report.

Brooksie · 01-18-2008

Quote:

Originally Posted by sweatmachine

my stock m/c won't work the dual 2piston calipers of my new front end very well. It is very mushy but it does grab. Per Carlos' recommendation I ordered a Rocket 3 master cylinder. It's larger than the bonnie's but looks almost identical. I'm going to install it this weekend, I'll post some pics and a full report.

Great mod! Where do you come up with these great ideas? Looking forward to seeing it. With the extra motor, mine is starting to show the lack of feel in the brakes.

amanger · 01-18-2008

The only way your going to fix your problem is to fit a 14 mm master cylinder the standard 5/8" is never going to pump enough fluid.This is a major problem on the Sprint and Triumph are now replacing the 5/8" with 14mm units under warranty.

MAR · 01-18-2008

I assume the Rocket 3 master does not have a remote container for fluid. I don't think it would fit on a Thruxton. I am wondering if Brembo makes a 14mm master .

sweatmachine · 01-18-2008

here's the Rocket 3 MC, it mounts up to the bonnie controls just like the bonnie's does:

schnabba · 01-18-2008

how much better would that make the brake modulation / force required for a stock brake disc and rotor?

I was thinking this might be a good upgrade to the stock brakes I have now, if it does improve things.... the stainless lines helped quite a bit... and putting on a bracket at the forks which was not cracked was also an improvement

Not looking for VFR ABS type stopping power, just wondering if it would improve the stock setup, and not break the bank!