Thorn RST and Magura HS33: rear brake squeal

[Man of Kent]

Morning All, I'll introduce myself and post some pictures of my ride in a few days time once I've given it a wash (!) but in the meantime wanted to start a thread with the above problem.

I've had a search for similar threads, lot's of info on Maggie's and thorn's in general but I can't find this particular one.

I'm running a pair of HS33's on my RST frame, front brake; fine no problem.  Back Brake: constant squealing!  I believe this has to do with the flexibility of the Rest's seat stays: they flex like crazy!  I've got the Maggie brake booster fitted and have tried both toeing in and running the brakes parallel to rim (as suggested by the manufacturer).

Has anyone else found this to be a problem and managed to solve it?  Different Mag Pads perhaps?  Different Booster?

All help greatly appreciated!  I look forward to taking part in the forums :-)

Yrs,
Ryan

[E-wan]

I've been had magura's on 5 different bikes over the past 15 years or so and curently run them on 3 of my bikes.

only had some slight squeeking with CSS rims and koolstop css pads. Other combinations of black/green/grey pads on aloy and ceramic rims have been fine.

with normal aluminum rim surface I've found the red pads very good, never had any squeele even on a aluminum bike with very bendy stays.

if using the booster you could try making sure it's not loose. The side with a slot rather than a hole allows some adjustment so you could set it so that there is almost some preloade on it to stop the stays flexing.

Also, have you tried cleaning the rim and break blocks, perhaps with some light sandpaper on the blocks

[Andre Jute]

I'm new to Magura rim hydraulics in the last four years and really like them for being progressive. They've squealed occasionally. In each case cleaning the blocks and the rims thoroughly has solved the problem. In one instance I was reduced to wiping the braking band on the front rim with blue spirit because I wasn't winning against a tar-like substance the diesel trucks leave on the roads here. This experience had led me to leave off adjustment until after the annual bike cleaning.

Admittedly, your problem sounds more serious but I can't comment as I ride a crossframe with, for practical purposes, zero flex.

Andre Jute

[Man of Kent]

Booster is solid and rims are clean!

I'll give the red pads a go and return my findings thanks chaps :-)
R>

[Man of Kent]

I've switched over to Shimano XTR V-Brakes and the problem is gone.  I tried pre-loading the booster and then clamping it tight; no difference, rims and pads were also cleaned thoroughly; still no difference! Red pads: no difference!

Given that no one else seems to have ridden maggies on an RST I'm going to put it down to the RST forks being nice and light and therefore maggies being OTT for this application: remembering that the HS33's are commonly used by trials riders who want to stop immediately (if i ever pulled an emergency stop or locked my rear wheel up; no squeal!) I came to the conlcusion that this particular combination of frame and components is just plain old noisy!

Additionally the HS33's compleltely ate 2 Sun Rim CR18's down to the wear line in a bit less than a year! I put this down to the fact that I use my brakes to slow progressively as oppoesed to stop suddenly.

Would love to hear from anyone who succesfuly rides an RST with HS33's; it's a problem that's bugging me now!