Cycling UK Forum

Hi

Looking for some advice re above. I'm fairly new to the disk brakes worlhence the query.

I bought a bike 3rd hand last year to use as a winter hack bike. It has the above brakes fitted and I was looking to replace them.

Searching has revealed that they are no longer available with a few used ones on ebay which is hard to tell if they would be in much better condition than the ones I already have (so would they be worth the spend?)

Just trying to figure out the most cost effective way of replacing them without having to replace other parts to get it to work.

Any thoughts or suggestions on this?

Cheers
Robert

(might be worth saying what is currently not working/what issues you are having. e.g. why replacement ? Is it something that might be fixable ? )

Have you tried a brake bleed and/or new pads/rotors before thinking about replacing the brakes? Those brakes when setup properly work fine.

RobertMcC wrote: ↑13 Aug 2024, 11:48am Just trying to figure out the most cost effective way of replacing them without having to replace other parts to get it to work.

What is it about the brakes that are currently not working or that you've decided require new calipers?

Generally - unless the pistons are absolutely seized solid - calipers last indefinitely. Might require new seals around the pistons and a re-bleed, both of which are jobs for a shop unless you know exactly what you're doing and have the required servicing kit.

Appreciate though that it's a third-hand bike and you may not know what servicing has been done on it to date or how it's been treated (eg, left outside in bad weather, not looked after etc).

Thanks for the replies so far, as suggested I'm not sure of the bike history re care and maintenance, I usually take good care of those that I have.

I've had a few niggling issues with the brakes. First up was the retaining bolts for the pads were ceased and after some advice from this site drilled them out and put split pins in place.
The pads tend to rub on the disc and after various fettling (adjusting caliper position,cleaning around pistons and changing pads) things have not improved that much. My feeling is that the return travel on the piston is not optimal.The lever travel on braking seems fine and I've had no issues with how it brakes.

If I put it into a shop then I would have to pay for mechanics time etc to investigate what is wrong and given the age,cost and use of the bike I didn't think it was worth it hence why I thought about just replacing. I then realised that the part is no longer made and have now discovered so many different types of disc setup and parts compatible to consider hence the call for some advice.

Cheers
Robert

Bet you a quid that many a Shimano mountain bike caliper would fit. You are much likely to get the correct mount, which I am assuming is post.

Sounds like you know about the fettling side more than me, but to check, do the pads appear to sit parallel to the discs and do you get any specific uneven wear pattern on the pads? I raise as a rubbing/ impossible setting issue I had( different brake set) where there was uneven wear from top to bottom of the pad....required refacing of the mounting posts to sort. So just checking you can rule this out before buying new calipers...as the problem would persist.

( sorry can't advise on replacement calipers that will work well with the levers)

hoogerbooger wrote: ↑14 Aug 2024, 9:19am I raise as a rubbing/ impossible setting issue I had( different brake set) where there was uneven wear from top to bottom of the pad....required refacing of the mounting posts to sort. So just checking you can rule this out before buying new calipers...as the problem would persist.

I think this ^^ as well.

On a new bike, you'd probably have been able to identify this from the outset (knowing of course that all parts were new and in working order). On a used bike though, tracking down issues like that can be far from straightforward, you can end up changing one part and chasing a problem around the bike. Worth noting as well that very few people know or care about this sort of thing so it's quite possible it's been ridden like that since new and the previous owners have either not noticed at all or they just assumed that's how it should be.

Depending on what the bike is and how much it's worth to you to have it in perfect working order, I'd be tempted to do a full strip and rebuild. Disc brake facing tools are staggeringly expensive and very much "pro use only" but if it's a good quality bike it's probably worth starting from the beginning and going through the issues right from the basics. As mentioned, if the frame or the mounts are out of alignment, no caliper on earth will work properly.

mattsccm wrote: ↑14 Aug 2024, 7:58am Bet you a quid that many a Shimano mountain bike caliper would fit. You are much likely to get the correct mount, which I am assuming is post.

I pretty much agree. IIRC shimano have only ever used a few different piston sizes, so there is much untapped compatibility betwixt 'road' and MTB brakes. IME calipers do not last forever unless you really look after them. Shimano hydraulic calipers commonly fail to a corrosion-induced leak (usually in the rear caliper), and it is quite possible for the pistons to go sticky instead. Obviously any free play in the hub bearings or disc runout can cause the pads to rub even if the pistons are retracting correctly.

Unless they're leaking then they just need a bit of work. The corroded pad axle screws are now fixed, so it's just another job to tackle

The alignment problems are either with the frame or the mounts have settled over the years in the wrong position and default there. Check for witness marks on the mount

If the calipers are safe and working then I'd leave them alone and just give them a clean, pads last for a long while in road use

Shimano doesn't sell many spares
https://si.shimano.com/en/ev/BR-RS505-3901
https://si.shimano.com/en/pdfs/dm/BR000 ... 10-ENG.pdf

If you really must replace them then you need a compatible brake hose number and mount type. A decent bike shop will sort this if you can't