Grrrr! Pulsing brakes!

Simonbt · Nitrous Nuisance Joined: 10 Mar 2005 Karma :

My bike's brakes pulse in a worrying way! If you brake hard the whole bike shakes up and down Shocked

Anyway, i know what your thinking.... "Warped disk".... Its not though. The disk is brand new from EBC and ive had it tested for runout and its fine. It has brand new pads and a braided line (so its all been bled too). I has the wheels shot blasted and powder coated and i'm a little worried that the guy has erroded my wheels so the disk doesnt sit right.

I taped a spike to my fork and put it against the disk and spun the wheel. There is very little movement side to side, although you can hear the spike rubbing the disk, then not rubbing the disk (although you can hardly see the change). I took the disk off and sanded off any remenants of paint from between the disk and wheel and it was slightly better when i put it all back together.

I have stripped down the caliper, and the poles that allow it to float side to side had rusted to the caliper wouldnt move. Ive cleaned them off and have ordered new rubbers. Could the cause of the pulsing and shaking be the fact that the caliper wasnt floating?

Just to top it all my mate pushed one of the pistons all the way into the caliper (flush with the top) and it now wont come out. Also the view window on the brake master cylinder degraded and broke off coming back from the test centre pouring brake out (luckly missed all the paint work and i caught most of it). Believe it or not you cannot buy a veiw window (even though they screw in), you have to get a whole new cylinder. I managed to get the rest of the thread out so i'm just going to see if i can find a bolt to block the hole up Confused

Anyone had a similar thing with the brakes and how did you fix yours. The amount of time i have spent on this bike, just to have it fail on one thing! Grrrrr!

(sorry for the long post but i'm bored Smile

)[/b]

Kickstart · The Oracle Joined: 04 Feb 2002 Karma :

Hi

What bike is this on? Is this your NS125?

Normally the first thing to look at is a warped disk. However even the tiniest amount of warping will cause problems if the caliper cannot slide. Given the other problems with the pistons sticking I would suggest you need to strip the caliper down and rebuild it. Sounds like it is a fair mess so probably needs new seals as well.

The piston should come out. Hold the other piston in place with a G clamp then pump the lever and it should move.

I was going to try and order one of those windows. Bit of bugger that they are not available.

Cleaning the disk mounting surface is well worth doing. Also is this a cast iron disk? These rust like mad and the pads can stick to the disk. When they come loose they tend to leave a mark which causes juddering.

All the best

Keith
____________________
Traxpics, track day and racing photographs - Bimota Forum - Bike performance / thrust graphs for choosing gearing

Simonbt · Nitrous Nuisance Joined: 10 Mar 2005 Karma :

yeh, on the NS125r. I thought about doing that with the Gclamp and you've just made my mind up on that one Smile

I've ordered all the seals and the rubbers new and they should arrive on monday. The annoying thing is i've stripped down the master cylinder and caliper already, then the piston was pushed all the way in. So i'm going to need to rebuild it all, bleed it all through again, then strip down, change the seals, rebuild and re-bleed. I'm probably going to buy my mate a pint for this one Confused

Just as a point to anyone with a 2t 125 - You dont need braided brake lines. Mine are very very strong at the moment. Way too strong actually. I am sure i could lock the wheel without much effort at all. There is about 2-3 cm of travel in the lever so its very sensitive (scary sensitive sometimes). The bike just doesnt have the weight to warrant that sort of stopping power.

Kickstart · The Oracle Joined: 04 Feb 2002 Karma :

Hi

Is the caliper off the bike? If still in place you should be able to just pump it out fairly easily.

All the best

Keith
____________________
Traxpics, track day and racing photographs - Bimota Forum - Bike performance / thrust graphs for choosing gearing

Simonbt · Nitrous Nuisance Joined: 10 Mar 2005 Karma :

Its in peices on my kitchen worksurface (it's little wonder my girlfriend loves me so much Laughing

) The only parts that are togther is the caliper and one piston. Everything else is stripped down.

I'm going to build it up off the bike to get the piston out. hopefully that will work Smile

Kickstart · The Oracle Joined: 04 Feb 2002 Karma :

Hi

If you have access to a compressor you should be able to get the piston out without reassembling the caliper.

All the best

Keith
____________________
Traxpics, track day and racing photographs - Bimota Forum - Bike performance / thrust graphs for choosing gearing

Simonbt · Nitrous Nuisance Joined: 10 Mar 2005 Karma :

tried that. My mates a mechanic in a sheffield and he said he could get it out with that. not sure how he did it though because he didnt take the other piston to block up the other hole.....

Its going to take an extra half hour but i've resigned my self to the fact im going to have to rebuild them to get it out.

moral of the story..... dont let people mess with your stuff Smile