I hate ******* disc brakes.(Problem found & sorted)

38Super

:evil: :evil: :evil: :evil: :evil: :evil:

Whoever thought they were a good idea should have been strangled at birth.

V-brakes - refitting front wheel < 1 minute

Disc brakes - refitting front wheel - 1 hour plus and still counting :evil: ( I gave up when I couldn't feel my fingers any more)

The Rookie

So which wally pulled the lever when the wheel was out?

Do it right and discs are quicker as you don't have to delatch the noodle to open the brakes out.

Changed a front Puncture the other night and while the rider was sorting his tools back into his back it took 20seconds to put his wheel back in, in the pitch black.

Simon

Simon

Chunkers1980

My disc front wheel is quicker than Vs as Idon't have to reconnect. You're obviously doing something wrong or somethig is up.

38Super

1) Take out cardboard spacer between pads
2) slip wheel carefully into dropouts.
3) check wheel is properly in dropouts
4) tighten QR tightly
5) Spin wheel.

and....

TING-TING-TING-TING-TING-TING-TING-TING-TING-TING-TING-TING-TING-TING-TING-TING

AAAARGHHHHH

If I slacken the caliper all is fine. As soon as I fully tighten the bolts then as above.

RevellRider

So this means that the front wheel was in wrong when you took it out or it's in wrong now.

My wheel drops in perfectly every time without any fuss

dusk

bent disc?

38Super

Brand new bike - only got it yesterday. Rode it round town for a while today and just got a few 'tings' when pressing hard on the left pedal.

My guess is that the wheel had been carefully aligned with the caliper rather than the other way round.

Should the caliper be self aligning i.e. loosen caliper bolts, pull the lever to the bars, tighten bolts. ? or is it more complicated than that?

Chunkers1980

well don't worry then, just ride. It'll bed in most probably.

woodytitan

38Super wrote:

Brand new bike - only got it yesterday. Rode it round town for a while today and just got a few 'tings' when pressing hard on the left pedal.

My guess is that the wheel had been carefully aligned with the caliper rather than the other way round.

Should the caliper be self aligning i.e. loosen caliper bolts, pull the lever to the bars, tighten bolts. ? or is it more complicated than that?

Sounds somewhere near. Check evans "How to" videos, that is what I used to show me how to realing and it worked a treat. Good luck with Jules.....!

38Super

woodytitan wrote:

Good luck with Jules.....!

????

I've checked the installation manual which says essentially "loosen bolts, pull lever, tighten bolts" as expected.

I'll have a look in daylight tomorrow and see if I can see what's catching.

I usually drop the forks on to the wheel (wheel on the ground). Would it make any difference if I did it the other way and lifted the wheel up into the drop-outs?

I'll have to check the hub as well and make sure there's no play in that.

It's a shame about all this really 'cos the rest of the bike is lovely. So far I'm liking the 29er feel. The handlebars do feel excessively wide though (680mm).

cooldad

100000000000000000000000000000000000000000000000 times better when it comes to stopping though, especially in lousy conditions.








I may be exaggerating slightly.

JohnnyAllez

Check it`s not the caliper mounting points (the lugs where the bolts fasten it to the fork) just brushing the disc slightly, mates bike doing this last week after new pads and "re-centering" the caliper :? Bottom mounting lug very lightly touching the disc, worse under heavy pedalling.

38Super

I've found the problem but not the solution

JohnnyAllez wrote:

Check it`s not the caliper mounting points (the lugs where the bolts fasten it to the fork) just brushing the disc slightly, mates bike doing this last week after new pads and "re-centering" the caliper :? Bottom mounting lug very lightly touching the disc, worse under heavy pedalling.

That's pretty much spot on. I've just been out looking at it. The lug isn't quite touching (I don't think) but it is so close that the 'captive' washer on the lower caliper bolt is touching the disc. As you say the problem was definitely worse under heavy pedalling. I assume you just moved the caliper over a bit but I can't move the bolt.

It's possible that the bolt is slightly bent. It's a bit hard to tell with that kind of bolt. I'm also wondering if the disc isn't quite seated properly on the face of the hub. There appears to be a small gap and I don't know if it should fit flush to the hub face. I'm slightly tempted to put a washer between the two nuts on the end of the QR spindle just to increase the clearance from the disc to the fork leg. I'm not sure if that might not do more harm than good though.

'Re-centering' shouldn't have caused the caliper to move though unless one of the pistons isn't moving properly?

The Northern Monkey

got any pics?

And what brakeset?

38Super

Brakes are Shimano M575.

You can see a neat line round the disc where the washer is rubbing.

This is the clearest pic.


This isn't very clear but you might be able to see how close the lower caliper bolt is to the disc.


This shows the gap I can see between the disc and the hub face.


Apologies for the quality of the pics but it's dark out there.

38Super

Remove spindle, put washer on the disc end of the axle and refit.

Result - totally silent brake for the first time.
No noise under heavy pedalling, steering or leaning as previously.
Not very impressed - there is clearly some incompatability with fork/disc/hub/caliper. Possibly the build of the hub but I don't know enough about hubs to know if that's possible.

I think I'll take the wheel to an LBS and get them to permanently install the washer in the axle and send the bill to the retailer.

Dirtydog11

Caliper isn't aligning properly because your assuming the pistons are centralised and they're probably not.

Pulling the lever is not a great way to set them up as it relies upon the pistons being central, if the pistons are lob sided then so will the caliper!

Push pistons back and align by sight, align the caliper to the disks not the pads!

The Rookie

Indeed disc is very close to 'this' (nearest camera) side of the calliper..

38Super

Dirtydog11 wrote:

Caliper isn't aligning properly because your assuming the pistons are centralised and they're probably not.

Pulling the lever is not a great way to set them up as it relies upon the pistons being central, if the pistons are lob sided then so will the caliper!

Push pistons back and align by sight, align the caliper to the disks not the pads!

The problem isn't the caliper though. The problem is that the disc is too close to the fork leg and is touching the caliper mounting bolt (fixed in relation to each other). That's why I was so frustrated as the problem persisted no matter what I did with the caliper.

Dirtydog11

Apologies, I've not fully understood the problem.

You shouldn't have to space the axle out, that's more of a workaround than a fix.

From what I have been able to gleen that wheel has some sort of carrier to allow the use of center lock rotors, I'd give Merlin a call.

I'd send them a link to this thread, saves having to try and explain it all to them and if you can try another wheel.

The Northern Monkey

38Super wrote:

Dirtydog11 wrote:

Caliper isn't aligning properly because your assuming the pistons are centralised and they're probably not.

Pulling the lever is not a great way to set them up as it relies upon the pistons being central, if the pistons are lob sided then so will the caliper!

Push pistons back and align by sight, align the caliper to the disks not the pads!

The problem isn't the caliper though. The problem is that the disc is too close to the fork leg and is touching the caliper mounting bolt (fixed in relation to each other). That's why I was so frustrated as the problem persisted no matter what I did with the caliper.

Have you tried refitting all of the brake mounts? I had EXACTLY the same issue 2 days ago when I fitted a new wheelset.
The brake mount was very very very slightly off centre (very hard to see with eye) and the disk didn't fit without rubbing terribly.

38Super

The Northern Monkey wrote:

Have you tried refitting all of the brake mounts? I had EXACTLY the same issue 2 days ago when I fitted a new wheelset.
The brake mount was very very very slightly off centre (very hard to see with eye) and the disk didn't fit without rubbing terribly.

I'm not entirley sure what you mean here. The caliper bolts go through the oval holes in the caliper, then through the shimano spacer(180mm disc) and into the fork leg mount. There isn't any play in the way it's put it together apart from moving the caliper.

It is possible that the thread in the fork leg is slightly misaligned which is skewing the bolt head in towards the disc causing the captive washer to touch the disc.

The washer I've put in is a workaround but, since there is no way to change the position of the caliper bolt, somehow the disc needs to move further away from the fork leg. I wonder if the disc isn't fitted to the hub properly. Maybe changing the disc to the shimano centre-lock set up might help.