[Closed] idiot with technical questions

You should be able to gently prise the pistons apart with a screwdriver.

the chain starts to skip

either disastrously loose or worn parts

and the back wheel comes out of alignment

ie not done up properly or faulty dropouts

I managed to narrow it down to the disc brake, remove the rotor and the problem stop

are you [b]sure[/b] ??? The only thing I can think is if the disc were badly warped, but really this makes no sense

and now I cant get them separated

take out the pads and ideally put in some old, worn ones, then lever them apart with a ****-off big screwdriver. If they still won't move the pistons need cleaning or replacing.

Don't see how a longer chain would help

Bolt up hub will solve most of your issues. Shouldn't need a smaller rotor then. To sort the caliper, get a flat headed screwdriver and slowly prise the pads apart. Chain should have ideally about 10mm of vertical slack

are you sure ??? The only thing I can think is if the disc were badly warped, but really this makes no sense

With the disc in I made it no more than 10 feet up the road outside my house, which is a gentle gradient. It skipped over and over again. Without the disc in place I made it much further with no issues, up steeper gradients. I tried it a few times with the same results. It doesnt make much sense to me either 😕

With the rotor removed I set the chain quite tight and it was fine, yet previously when set tight it had still skipped (although not as much as when slacker).

ie not done up properly or faulty dropouts

I tightened them up to the point where they wouldnt go any tighter, if its faulty dropouts then Im guessing its simply ****ed?

If its faulty parts Im assuming it can be narrowed down to chainring, sprocket and lockring?

Ill try getting the pistons apart with a screwdriver.

Thanks for the info, lot to go at

I wonder if the caliper/adapter is mis-aligned somehow? That might result in the wheel being out of alignment when the axle is tightened. Mind you, it'd be a bugger to pedal.

Did it come with a 185mm rotor? Seems a bit overkill for that bike.

That was another thought druidh as I had difficulty in getting the caliper to fix on to the frame properly, the lower bolt was very difficult to fix. Is it possible to get brake calipers helicoiled?

When I got it it didnt come with a brake fitted, although the guy did chuck in a 165mm rotor. The brake came with the 185mm rotor and the adaptor.

Are you sure the caliper/disc are the right size for each other?

If you try to put a 185mm disc into, say, a 165mm caliper the wheel may sit 10mm further forward in the dropouts, maybe just on the left and that could cause all sorts of issues. You should notice the disc rubbing on the caliper if this is the issue. With the disc on does the axel sit at exactly the same place in the dropout as it does with no disc and does it it sit at the same point on both sides?

[EDIT]

When I got it it didnt come with a brake fitted, although the guy did chuck in a 165mm rotor. The brake came with the 185mm rotor and the adaptor.

I assume you mean a 160mm rotor...

Is the caliper IS or Post mount?
Is the frame IS or post mount?
What type of adapter is it?

chaintugs?

Sorry, should have made it clear. I bought the brake separate from the bike. The guy who sold me the bike chucked in a rotor and a few other bits that he had kicking around.

[idiot mode] I hadnt thought of that andrewh, I thought that all calipers would have been universal. Come to think of it I thought I spotted a difference in the wheel alignment of just a couple of mm but put it down to my eyes playing tricks. [/idiot mode]

Ill see if LBS has a smaller 165mm adaptor for the brake. I have fitted the smaller disc but it only bit on the uppermost part of the disc and I assumed full contact would be better.

EDIT - oops, yes a 160mm disc...god knows where I got 165 from 😳

EDIT 2 - adaptor is one of these:

[img] [/img]

rear mount is similar to one of these:

[img] [/img]

I tightened them up to the point where they wouldnt go any tighter, if its faulty dropouts then Im guessing its simply ****ed?

so either faulty, bad design or, as I suspect, not being done up correctly?

If its faulty parts Im assuming it can be narrowed down to chainring, sprocket and lockring?

I meant [i]worn[/i] chain or sprocket!

165mm do exist, I have one on the back of my HT. Hope did them mnay years ago.

I meant worn chain or sprocket!

Ah sorry, misread your initial post. Apologies for that

Managed to get it sorted, just need to get a smaller adaptor so it will work with the smaller disc properly.

Thanks for the information folks, really appreciate it.

so, was the disk stopping the axle seating properly ?

Yeah thats what it seemed to be. I honestly had no idea that the rotor might not fit the caliper properly, I thought "185mm adaptor...should fit then".

Its got the smaller rotor fitted now, but has virtually no stopping power at all. Getting the pads back in again was a right bastard of a job thanks to that little clip inside the caliper not wanting to play ball.

Still at least its working for now, although no doubt a simpleton like me will be back in a couple of days with more issues.

Getting the pads back in again was a right bastard of a job thanks to that little clip inside the caliper not wanting to play ball.

perhaps you just need a bit more practice with mechanical things ?

Completely agree with you

Or a bigger hammer.

oooh. Don;t think I've got something right for a very long time 😛