Strange disc brake phenomenon

[danielrlee]

I've experienced a strange behaviour from a set of Tektro Auriga Comp hydros since I acquired the bike they came with about 18 months ago. The bike in question also features regenerative braking via a DD hub motor, which means I hardly ever use the physical brakes, hence why I ignored the issue for so long.

I can't remember how the brakes performed when I bought the bike (couldn't have been too bad since it passed an unpowered test ride), but the rotors were warped to buggery so I replaced them immediately. I also performed a brake bleed as part of the initial bike prep. I didn't replace the pads since they looked pretty fresh and as if had plenty of life left in them.

Here's the problem – Under normal circumstances, braking is pretty pants. It takes quite a bit of effort to stop, more than hydros should anyway. However, if I carry out a few high speed stops (30mph to 0) and get some heat into the rotors, the braking performance is amazing.

Why would this be? Could the pads be contaminated and are causing lacklustre low-temp performance? Yes, I could have replaced them by now, but didn't in case the whole brake system needs replacing.

Anyone got any ideas?

 

[soundwave]

you could try cleaning the pads or just replace them for new ones.

 

[danielrlee]

you could try cleaning the pads or just replace them for new ones.

I have tried cleaning them with an abrasive, but it made no difference.

As mentioned, I hardly ever use them, so never got round to purchasing and replacing the pads.

 

[JuicyBike]

Spray on Isopropyl Alcohol onto the rotor surface and wipe it off. Best to keep away from the brake pads, lungs, little children etc.
Quite expensive, especially in specialist bike shop form, but is available on Fleabay.

 

[Deleted member 4366]

I would say that your pads are probably getting glazed through lack of use if you have regen braking. I think you need the constant hard braking to wear off the glazed surface. Also, winter salt seems to have a big effect on them. Giving then a good clean after it's all gone improves them a lot.

Different pads work better under different circumstances. As you go quite fast, try sintered ones.

 

[soundwave]

and the rotors?

 

[danielrlee]

I haven't tried cleaning the rotors yet.

Is acetone a suitable alternative to rubbing alcohol? I don't have any rubbing alcohol, but I can see my GF's nail varnish remover from where I am sitting

EDIT: Scrap that, it's got a moisturising oil additive to make your brake rotors nice and soft. I've just found a bottle of surgical spirit, that I'll use instead.

 

[flecc]

Your local chemist will have isopropyl alcohol and can supply a small bottle of it. They'll ask what it's for but will be happy with your answer.

My opinion is also that it's the brake pads that need replacing, but clean the rotors before using the new pads.
.

 

[stumpy150]

I use brake / clutch cleaner spray from Halfords - the same that you use on the car...give the rotors a quick spray and remove the pads and give them a rough up with some emery cloth on a flat surface ... should do the trick.

I had issues with my Tektro brakes last September while on holiday. On return I replaced the tektro pads with organic shimano pads and replaced the rotors with shimano Zee .. I am now going to replace the calipers and pipes with shimano in the next couple of weeks

 

[danielrlee]

I've cleaned the rotors with surgical spirit and removed the glazed surface of the pads with some abrasive. I only did the pads previously, so hopefully doing the two together will solve the issue.

I'll report back on Monday after my afternoon run to the Post Office.

Thanks guys.

 

[danielrlee]

Out of interest, can anyone speculate as to why hot rotors/pads would improve braking performance in this instance?

 

[flecc]

If there was a film of any substance glazed onto the rotors, the pads wouldn't grip, but sustained contact could make the substance heat up and soften, causing binding between pads and rotor.
.

 

[soundwave]

you also dont want hot rotors as will warp them the hotter they get

 

[stumpy150]

Chain Reaction have Shimano Zee rotors on offer at the moment...

 

[danielrlee]

Disappointing. Cleaning my pads & rotors made no difference to the braking performance. Admittedly, it was only a short journey of a couple of miles and may not have had bedded in again yet. I'll give them a little longer before I replace the pads, but I dont think they'll improve.

 

[stumpy150]

Don't be so negative !

You could either give up , take the bike to the local charity shop and make it a donation OR.....

You could have another go at sorting it out OR....

You could take it to your local bike shop and let them take a look at it ???

 

[danielrlee]

Don't be so negative !

You could either give up , take the bike to the local charity shop and make it a donation OR.....

You could have another go at sorting it out OR....

You could take it to your local bike shop and let them take a look at it ???

Strange reply? Not sure if my post was a little unclear, but I meant that I don't think the existing pads will improve. New ones are what I'll try next.

I certainly won't be selling my bike or giving it to the charity shop and I've never had a bike shop fix any of my own bikes in my whole life!

 

[stumpy150]

It was a tongue in cheek reply meant in good humour


If you have tried several methods to try and sort your brakes and you haven't had much luck then I would either get a mate to have a look at them - sometimes a second head helps and also try out your local shop ..... For the amount of time you have have spent on the bike plus the potential cost of another set of pads it may be worthwhile for the cost of an hours labour at the bike shop for them to take a look at it ??

Last suggestion - have you checked the calipers pistons for movement ?

I recently sorted a mates motorcycle who had been having issues with poor brakes - new pads had been fitted and allegedly serviced by a main dealer - turned out the Pistons were corroded and partially siezed ..,,, New pistons and seals sorted them out.

Best of luck

 

[Alan Quay]

Disappointing. Cleaning my pads & rotors made no difference to the braking performance. Admittedly, it was only a short journey of a couple of miles and may not have had bedded in again yet. I'll give them a little longer before I replace the pads, but I dont think they'll improve.

Did you rough them up with sandpaper?

Sent from my HTC One_M8 using Tapatalk

 

[danielrlee]

Just thought I would update this thread for completeness sake.

I ended up purchasing two sets of replacement pads, but didn't do anything with them for weeks. Having now replaced the old pads and carried out a bedding in procedure, the brakes are back to how they should be and now give great performance. I imagine they'll probably last for the life of the bike now considering how infrequently they are used.

Thanks all for your help and suggestions.