[LARGE IMAGES] Did my brakes do this?

ED E

Hey guys,

Noticed this slightly before, but didnt really pay much attention, then last week I looked again and was kinda shocked. Its hard to show it in a photo but the whole rim, on both sides(more so on the right) of my rear wheel is "buckled" concavely. When I bought it they were most definitely straight.

Did my brakes do this? Or the tube/tyre? I'm cycling a good while and myself nor the old man(ancient) have seen it happen before. Anyone know what did it?

And before some smart-arse says it, yeah, will have to be replaced.

Cheers,
Lethal

CheGuedara

I'd say 50:50 rim wear and tyre pressure - my guess is that the thinned sidewalls have become slight enough that the stress on the rim is starting to bend it outwards (looks more evident on the first pic, though I don't know if that's due to b&w+shadow or not)

ED E

Yeah, the first pic is the worst part of the right rim, and that analysis makes sense.

Thing is, I think only have it a year, or less even, and havent done that much on it(Less than 1000Km). Should a Shimano wheel not last a bit longer than that?

Keep_Her_Lit

Brake wear would be the most likelly explanation, I'd say. I have an old rim sitting in my shed which looks pretty similar to that and without doubt it was brake wear that produced that distinctive concave appearance.

Many rims come with small indents or grooves in the braking surfaces which are meant to act as brake wear indicators - when you can no longer see them, it's time to replace the rim. Aluminium alloys are fairly soft, so it's quite normal that significant amounts of rim material are removed by braking.

This kind of wear should not happpen overnight, however, so if it has taken you by surprise, there may be some other factors to consider. Are you using very abrasive pads? Have you ridden the bike all through the winter without cleaning the rims or pads? Road grit and crud will accelerate the wear significantly. Do you use the brakes very heavily? Maybe you are a big lad who likes descending. Are you negelcting the front brake and dumping all the braking onto the rear wheel?

For sure, this rim is now in a dangerous state and if you really have to continue using it while waiting for a replacement, you should defintely keep your rear tyre pressure on the low side. If used for much longer, the rim will fracture along the braking surface, where it is thinnest. But I'm sure you will sensibly retire it before that happens.

petethedrummer

Its the brakes what dunnit. If they wear down sufficiently the air in the tyre will fold the rim at the weakest point. Happened a mate of mine recently.

Check your brake pads regularly for little shards of aluminium. They will shorten the life of a rim quick smart.

On most rims there is a wear indicator groove in the centre, when that is smoothed out your rim should be replaced.

f1000

I would agree with Keep Her Lit.

My commuter bike has a similar problem, but I can just about see the wear indicator line. Went to my LBS just to be sure and was told I would need a wheel rebuild in the near future for a minimal cost compared to a new wheel.

After my consult I removed the pads to check their condition and noticed some glass, metal and stone shards embedded in the pads. When doing my regular bike clean I neglected the pads and thus the result of worn rims.

ED E

Keep_Her_Lit wrote: »

Brake wear would be the most likelly explanation, I'd say. I have an old rim sitting in my shed which looks pretty similar to that and without doubt it was brake wear that produced that distinctive concave appearance.

An answer, yus:D

Many rims come with small indents or grooves in the braking surfaces which are meant to act as brake wear indicators - when you can no longer see them, it's time to replace the rim. Aluminium alloys are fairly soft, so it's quite normal that significant amounts of rim material are removed by braking.

Something I'd noticed before but completely forgotten about.

This kind of wear should not happpen overnight, however, so if it has taken you by surprise, there may be some other factors to consider. Are you using very abrasive pads? Have you ridden the bike all through the winter without cleaning the rims or pads? Road grit and crud will accelerate the wear significantly. Do you use the brakes very heavily? Maybe you are a big lad who likes descending. Are you negelcting the front brake and dumping all the braking onto the rear wheel?

I got lazy with maintenance TBQH, college had me distracted. One pair of pads did get way low, but I replaced them as soon as I realised. Pads got a rub of P40 ever say two months. Pads are brandx sh1t.

I do tend to rely on the rears a lot. I'm slight enough but 6'2(haven't weighed myself in ages) but the bike is 13.5KG itself and I tend to carry loads(30x500ml cans for example[what, its college:p ]) in my satchel. Not much descending but commute into college is breaking heavy due to traffic.

For sure, this rim is now in a dangerous state and if you really have to continue using it while waiting for a replacement, you should defintely keep your rear tyre pressure on the low side. If used for much longer, the rim will fracture along the braking surface, where it is thinnest. But I'm sure you will sensibly retire it before that happens.

Will be on it a week till I have time to change it out at the weekend. Exams start thursday:(

f1000 wrote: »

I would agree with Keep Her Lit.

My commuter bike has a similar problem, but I can just about see the wear indicator line. Went to my LBS just to be sure and was told I would need a wheel rebuild in the near future for a minimal cost compared to a new wheel.

After my consult I removed the pads to check their condition and noticed some glass, metal and stone shards embedded in the pads. When doing my regular bike clean I neglected the pads and thus the result of worn rims.

How much did a rebuild cost? The wheel in point cost €45 in JDC and I know I could't build myself, would it be economical with a new rim+labour.

Is it worth investing more and getting a better quality wheel/rim?

Thanks for the help lads,
Lethal.

blorg

For a €45 wheel it may be as economical to replace the whole wheel; I doubt a new rim + rebuild would come in much cheaper.

f1000

Lethal_Bullet wrote: »

How much did a rebuild cost? The wheel in point cost €45 in JDC and I know I could't build myself, would it be economical with a new rim+labour.

€30 for a rebuild with a mavic rim. holding off for a few weeks as the rim has some life left in it. Current is alex rims, but the bike has been doing a min of 15k on workdays for nearly a year.

kona

If you ride the bike in that condition you deserve a Darwin award, its dangerous.
The next step will be the rim folding out, Ive only ever seen a wheel get that Bad once, and when air was put into it, it split. Its caused by the brakes and is normal wear and tear.

Beasty

Fortunately this happened on a slight incline at around 25kph:



2 minutes later and I would have been descending at around 55kph. Quite an explosion when it went, and the rim had only done around 4,000km or so - I suspect there must have been some other damage from hitting a rock or pothole, but once the tyre burst through the rim it took nearly a quarter of the edge of the rim off, presumably because of thinning caused by braking.

kona

Beasty wrote: »

Fortunately this happened on a slight incline at around 25kph:



2 minutes later and I would have been descending at around 55kph. Quite an explosion when it went, and the rim had only done around 4,000km or so - I suspect there must have been some other damage from hitting a rock or pothole, but once the tyre burst through the rim it took nearly a quarter of the edge of the rim off, presumably because of thinning caused by braking.

Thats almost a carbon copy of what happend with my experience of it, happend putting air into a tyre for somebody (no I didnt charge ), he had the cheek to blame it on me too. Id say it was brown trousers there, I jumped when it went and I was left quite confused for a few seconds haha

cantalach

This must be International Post a Photo of a Busted Rim Day.

Civilian_Target

Wow.

My bike started making a thuck-thuck-thuck noise on the way home this evening. It had been braking unevenly at the front for maybe 10 days now. When I got home I noticed there were shinier and less shiny bits on the rim. I'd vaguely remember seeing this thread, but not really getting it. Now I get it!

When I first looked at the rim, it seemed fine, good and thick at the top, but buckled outwards in at least 3 places. Then I measured it up with a piece of metal plating and it's immediately clear that there's a substantial concave bend. On closer examination, at the biggest buckle point the rim is just in the process of splitting - it wouldn't have survived another descent.

I was going to hammer the bumps back into place, but now that I realise how thin the rim's become, no chance. The really ****ty thing is that I took the bike for a service the weekend before last, and they obviously didn't check - poor effort!

Thanks for posting this thread - I have a pretty heavy descent on my ride home, and I wouldn't have wanted to bust a rim!

[EDIT] Just for the record, they're Alex Rims G2000, on a wheel that I got 2nd hand. A quick google indicates the distinctive wear pattern is long gone. I've run them for at least 20,000km, and I'd say the original owner must have run them for at least another 10,000, so no complaints![/EDIT]

Civilian_Target

A bent piece of rim, where the brakes have worn it shiny


Here the rim has started to split


Here's the concave wear

cdaly_

Jeez, you don't need a straight edge to see the wear on that rim!

Civilian_Target

cdaly_ wrote: »

Jeez, you don't need a straight edge to see the wear on that rim!

hah, my one or his one?

Once you're aware of the wear pattern, it's obvious. If you're not aware, how would you know?

What annoys me is, it went for a service 2 weeks ago, the mechanic fitted new brakes so he must have noticed the wear....

Seaswimmer

cdaly_ wrote: »

Jeez, you don't need a straight edge to see the wear on that rim!

I went through a couple of front rims with this problem through using the front brake a lot. What i do now is to angle the brake shoe so when i brake it touches the whole rim from the part which holds the tyre down to the piece where the spoke sit. It wont stop the rim wearing but should ensure it wears evenly..