Brake pad causing flat?

straas

After getting three punctures on my front tyre in as many days, I thought I'd have a better look at what might be causing it.

The punctures are all toward the inner part of the tube, so don't appear to be caused by something penetrating the tyre. Two have happened under heavy braking.

I had a look at my pads, and they've worn unevenly with a lip at the top - this seems to be resulting from the pad not being fully in contact with the rim, I'm assuming it's managing to pinch the tube through the tyre somehow when braking?

My pads are set as low as I can so I'm not really sure how to remedy the situation?

shiznit76

your pads shouldn't be touching your tyres, should only come in to contact with the rim

homers_double

Can you get deeper calipers?

straas

I've got these forks: https://www.tredz.co.uk/.Dedacciai-EDG- ... A8QAvD_BwE

and shimano 105 5800 calipers, surely these two should be compatible and not cause this issue?

I've done approx 10,000 km on this bike and this is the first time I've had this issue?

cooldad

Pinch flats or spoke poking through from the inside?

shiznit76

surely if you have done so many miles on it without any issue it is unlikely that the brakes rubbing would be causing it now? Agree with possible spoke causing it from inside of rim

Matthewfalle

errr - please get someone who knows what they are doing to put in new pads and set them up properly.

from the sounds of things you may be likely to get death disease soon if only part of the pad is touching the rim.

6wheels

To prove/disprove your theory, take the pads off and file/sand a 45 deg angle on the top edge to remove the lip.

cougie

Take off the front wheel and reinstall. It can't be all the way in.

Surely you'd have noticed your blocks missing the whole rim before now ? You'll be wearing away your tyre and that's not good.

straas

Definitely not a spoke, checked the rim over the tape is in place with no holes etc.

There's no visible wear to the tyre sidewalls, but the fact two punctures occurred under heavy braking suggests an issue between the pads and tube.

The wheel is in the dropout as far as it can go, and the pads are as far down as the adjustment allows.

Is there any adjustment for the whole caliper itself to let it sit slightly lower?

cougie

You could file a bit out of your caliper holes if it's only a mm or two. Who put the bike together ?

joe_totale-2

Perhaps the quick releases are allowing the wheel to move a bit?

webboo

I know it’s cold and wet out there but is your rim over heating when heavy braking and causing the tube to blow.

Matthewfalle

straas wrote:

Definitely not a spoke, checked the rim over the tape is in place with no holes etc.

There's no visible wear to the tyre sidewalls, but the fact two punctures occurred under heavy braking suggests an issue between the pads and tube.

The wheel is in the dropout as far as it can go, and the pads are as far down as the adjustment allows.

Is there any adjustment for the whole caliper itself to let it sit slightly lower?

you've got the wrong calipers then.

arlowood

I had a similar issue with a set of wheels on a brand new bike. On one of the first outings I braked hard at the bottom of a steep descent and the rear tyre went pop

Close inspection showed that the rim tape was made of cheese and had ballooned into the spoke recesses and at one point had split exposing the sharp edge of the spoke recess. Inner tube had contacted this edge and blown. My conclusion was that the heavy braking had heated up the rim causing the poor rim tape to soften and be deformed by the inner tube.

I complained and they sent me some new rim rape

I would check the rim and tape again just in case there might be a minor split that is exposing a sharp edge.

straas

Webboo wrote:

I know it’s cold and wet out there but is your rim over heating when heavy braking and causing the tube to blow.

It's more short sharp braking on the flat, than extended downhill type braking so think this one's out.

I'll have a check for any play in the QR but didn't notice any.

No idea why it's only surfaced as an issue just now.

Both fork and caliper are pretty standard components, so seems odd that they'd be incompatible?

SJH76

Before we go down the "wrong caliper" path, are these the original brakes that were fitted to the bike on purchase or did you build/replace them some time in the past?

On the fact after so many faultless miles the pads may simply just be at the point that they come in too close and hit the tyre. The way calipers close the less pad there is to hit the rim the higher up they come in contact with the rim to the point they will eventually catch the tyre wall. New pads and no adjustment should solve it - if this is the issue or course.

Vino'sGhost

Good for ten thousand miles and then a problem?

Sounds like everything works as it should and has just worn. Unless somethings changed. Is the Caliper Centered properly? If not one side will be higher than the other. Adjust with the grub screw and see. And change your pads.

And also gently as I can and without meaning to be disrespectful, if you can’t work this out it might be better paying a few quid to someone that can.

Matthewfalle

any pictures?

otherwise we are just going round in circles.

capt_slog

I'd have thought that if the brakes were touching the tyre, then it would be shredding it and it would be obvious.

You say that the holes are where the tube touches the wheel ("inner part of the tube")? Have you noticed that they are always in the same place by any chance?

I'm wondering if there is something on the tape or the wheel itself that isn't obvious, perhaps lying flat or parallel to the tape/wheel/tyre . Under heavy braking, the assembly moves/deforms very slightly on the rim, and this then gives you the puncture.

trivial_poursuivant

I wonder, what brand of inner tube are you using? I had what I think was a dodgy batch of Continental long valve variety which had 3 split at the seam. There was no signs of dirt on the rim and were fitted to Zondas which don't require tape or even spoke holes to worry about. The holes were all tiny but right on the inner seam about an inch from the valve. I have since moved on to Vittoria as a consequence.

sam_anon

This thread could become a parody for all things wrong with online forums!

I would recommend some expert advice, as others have!

SJH76

Trivial poursuivant wrote:

I wonder, what brand of inner tube are you using? I had what I think was a dodgy batch of Continental long valve variety which had 3 split at the seam. There was no signs of dirt on the rim and were fitted to Zondas which don't require tape or even spoke holes to worry about. The holes were all tiny but right on the inner seam about an inch from the valve. I have since moved on to Vittoria as a consequence.

I must admit I have also had dodgy batches of tubes. Schwalbe ones I once bought in bulk were coming apart at the valve so I binned the lot. Although it would have to be a hell of a coincidence for each tube to break at exactly the same place each time.

straas

Hopefully have uploaded some photos here, it is looking like the wrong caliper for the job.

Pretty annoying if so as the lbs should have picked it up when they replaced the brifters surely?

https://ibb.co/wZk423
https://ibb.co/YfY5g9S
https://ibb.co/KLXTPqv
https://ibb.co/k3gj9pN
https://ibb.co/MhsqgFn

shiznit76

your calipers are way too short, surprised it has taken 10k miles for any damage to have happened

Matthewfalle

calipers way too short and rims look knackered.

i ain't riding that. its lethal.

please buy some ne long drop calipers and find a new bikeshop - your current one has no idea what it is doing.

photonic69

So you've done 10k with this set up with no prior issues? So what changed before you began to have problems?

Where do new brifters come into this equation? If they worked once then they should work again provided nothing has changed however they do look on the limit. You 'might' get away with them if you angle brand new pads downward but when they wear away the problem returns

Matthewfalle

PhotoNic69 wrote:

So you've done 10k with this set up with no prior issues? So what changed before you began to have problems?

Where do new brifters come into this equation? If they worked once then they should work again provided nothing has changed however they do look on the limit. You 'might' get away with them if you angle brand new pads downward but when they wear away the problem returns

angling them down won't help.

the calipers are the wrong ones. you are lucky you haven't died yet.

shiznit76

if you angle the pads down then the side nearer the forks will just rub even more against the tyres

Matthewfalle

and find a new shop. the lot you are using at the moment are useless and dangerous.

photonic69

shiznit76 wrote:

if you angle the pads down then the side nearer the forks will just rub even more against the tyres

No. Angle them down inwards towards the hub. Laterally not longitudinally.