ColonelSanders

There is a long and boring story about why I ended up with rim brakes on my Surly Troll that I won't go into and at first I thought I would only have rim brakes for a year or two at most.

My previous experience with Rim Brakes were with Alivio level rim brakes I believe and from around 1997 and they didn't overly impress me, but this time I was going with XT level rim brakes and I was keen to see how well these did.

I was actually shocked by how well they worked and thought they were definitely better than low end Shimano disc brakes and seemed to be at the level of mid level Shimano disc brakes I had on my Merida Big Nine XT Edition hardtail.

One of my concerns about rim brakes was that eventually you wear out your wheels, where with disc brakes, you only wear out rotors.

Some folk on these forums seemed to think your rim brake wheels would last for many years and tens of thousands of miles/kilometres, maybe even as long as 100,000kms.

I can't be sure how many kilometres I have racked up on my bike, as I am not a high mileage rider and I have had my Surly Troll on the road since approx early 2019, and am still on my original rim brake pads.

Then a bit over a week ago, the braking surface of my rear tyre, broke away from my rim and flatted my tube instantly.

Anyway, I thought I would share some pics of my wheel and seek feedback on how many people here have had something similar happen to them.

I had a half decent Mavic rim on my bike as well.

tomato coupe

Are they carbon rims with an aluminum brake track?

delbiker1 

I think I have never seen that.

Rolla

Many of ours have. Yours looks to be an anomaly.

ColonelSanders

No, they are all aluminium rims, Mavic EX 721.

wolfchild

If this happened on the front wheel you could of had a serious crash.

wolfchild

Some folks just like to inflate their numbers....Anybody who rides a lot especially in winter an in dirty conditions is going to wear out their rims a lot sooner than few thousand miles.

drlogik 

I've been working on and been around bikes for over 50 years and I've seen some strange and weird things but that's something I have never seen before. I'm wondering if it was a latent defect in the rim.

79pmooney

You don't want to be riding when that happens. The colonel's brake track stayed attached at both ends. I've never seen that before. Every one I've seen has broken free at one end and flailed like a reaper if the bike was being ridden when it happened. I've seen CF chainstays cut deeply. A bike where I am certain the rider went for stitches.

If you ride in the PNW with rim brakes, you will wear brake tracks to nothing unless you stop using that wheel before you get there. The dust here is volcanic and basically grinding compound. I used to get 2 winters from my commuter rims riding 150 miles per week in the city. At that point I'd have a deep concave track. Went too long once and was lucky to be in the house when the rim exploded. That one would have been stitches, and ruined paint. (Steel frame.) My Mooney went 17,000 miles of mainly summer dry in Seattle when I caught a pavement irregularity and collapse the sewup rear rim. No brake track left. Several long abscesses you could see through. (Sewup rims don't support the tire air pressure so they brake track fail far more safely.)

biker128pedal

Looks more like rim failure at the corner where the brake track meets the spoke surface and not brake track wear. Well unless you pads were adjusted to far in. I've worn down two mountain bike rear rim brake rims such that they failed. They broke in the track. The aluminum wears in a concave shape if pads are positioned correctly. At least I had tubes. Anyway I don't know if I have pictures but they failed where the aluminum got too thin. Not like yours and crack and separate at that edge. My guess is the wheel was overloaded or took quite a few big hits to fatigue the aluminum.

Still that sucks and give an advantage to disc brakes. Now is the itme for me to look at a front wheel upgrade to disc. My old Tora fork will is set up for rim now but will take disc. Oh but then the silver Ringle hub has to come off. It's been though two rims. ;-)

Reynolds 

It happened to me, on my commuter, after some 30,000kms of all-weather riding. The rim didn't break suddenly, but bulged outwards hitting the brake pad. I was about 2km from home, but unhooked the V-brake and made it.

63rickert

It happens. Not at all likely to happen to someone who is not racking up big miles.

When it happens relatively early the culprit is usually a stone or shard of metal embedded in the brake pad. Now that this has happened you will keep an eye on that forevermore.

Excess tire pressure contributes. It takes a lot and it takes a lot over a long period of time. Many riders do seriously overinflate.

Erratic spoke tension contributes. Even when it purely looks like the sidewall.

Only time I ever did this on my own bike part of the problem was a bad rim. Mavic has been coasting on ancient reputation for a long time. I don’t read BRAIN closely enough to know who owned them when your rim was made. It has just been a brand name in play quite a while. Don’t replace wth Mavic.

With good rims and good practice the rim is hollowed out noticeably a long time before failure. Any ordinary inspection shows the problem before it happens.

JohnDThompson 

Rim wear from braking is greatly affected by the conditions in which you ride. If you ride on clean, dry pavement, you can certainly expect your rims to "last for many years and tens of thousands of miles/kilometres." If you ride a lot in wet and/or gritty conditions, your rims will wear out much faster.

indyfabz

The danger is real. After a mere 8.5 years of commuting, errands, day rides and thousands of miles of full loaded touring in all sorts of weather on many different surfaces the rims of my LHT needed replacing.

katsup

This happened on the only rim I wore out as well. The brake started rubbing and saw the rim budge when I investigated.

No idea how many miles on those wheels, I had bought them used.

cyccommute 

I agree that some folks inflate their numbers…but in the other direction. In 40+ years of commuting, winter riding, mountain biking, loaded touring, loaded mountain bike touring, and over all abuse, I’ve worn out 2 or maybe 3 brake surfaces on rims. I’ve had far more rims fail due to cracking of the eyelets…and not many of them…than due to failed brake tracks.

But I also use brakes sparingly. I can go years without replacing pads…and I live in a hilly city with mountains just a few miles away.

Koyote

If you're getting less than a "few thousand miles" from your rims, you are doing something very, very wrong. No matter the conditions.

CrimsonEclipse

You know what i like about rim brakes?

Absolutely nothing!

Kedosto

I had the exact same experience many years ago. The rim failed in the same way and the tube blew out exactly like yours. I’ve also blown a tube from overheating a rim on a long, fully loaded touring descent. Such is the nature of the technology.

I realize that rim brakes meet the needs for many, and back in the day we didn’t have a choice, but once disc brakes became a reality I couldn’t wait to get on board. In the years since, the worst that’s happened is a blued rotor. I can live with that.

cyclezen

I've seen a few rim failures over the many years, but almost all could be ascribed to rim damage done prior and just a few likely due to rim material failure.
Never seen one where the rim was worn enough to part, except in one case where the rider had their pads improperly angled, and the very hard pads had cut the braking surface closer , at the lower/inner part of the brake surface.
Pics don;t really tell us too much - but a hard thing to do without hands on.
A possible is that there was a flaw in the rim, and possibly an undetect 'hit' to that one side, and a highly inflated tire, might cause the rim to bulge and peel outward.
Alu has a tendency to fracture, then continue that fracture along the stress lines - in this case being any light grooves worn into the braking surface, by the pads.
What pressures do you run your tires?.
There seems to be plenty of sidewall material in the visible section, if it's 1.5 to 2 mm, that's plenty material.
I'd mic sections in that failure area and determine if there are any 'thin' spots. Not that that will mean anything... You're still gonna need a new rim...
Ride On
Yuri

downtube42

I had a similar failure on my commuter years ago. It blew while sitting in the garage. The braking surface was clearly worn down, compromising the strength of the rim.

ColonelSanders

Since I have been using the bike with that wheel on it, I have at times been riding with high pressure for a 2" tyre, where I will pump it up to 75 to 80 psi and wait till the pressure drops to 45 to 50 psi(takes about 3 weeks) and pump it back up to the 75 to 80 psi and repeat.

Additionally I am a heavy clyde and in recent months have been using my bike to haul back groceries and I will have 8 x 2 litre bottles of Pepsi Max(approx 16kgs) on a rack basket over the rear wheel and I have a very large backpack that when filled up with the sort of stuff I buy, gets to be anywhere from 22kg to 30kg in weight, so I have been putting a big load on my rear wheel in particular.

chaadster

I’ve both seen this failure mode and had it happen, though that was back around ‘89 or so. My brake track didn’t rip that far around the rim, but bulged along an inch or so and separated from the rim just a bit, directly below the bulge.

Anyway, it’s a rare failure, so I wouldn’t put too much into it, like fretting about how to prevent it. Replace the rim with a higher quality hoop and ride on. Like, I don’t know what a Mavic EX 721 is, so maybe compare that to a Mavic CXL or Open Pro, for example, to see which quality elements may distinguish them.

Be aware it may be less expensive and make more sense to buy a new, pre-built wheelset than have a shop get and lace in a new rim.

Ghazmh

Did you over inflate the tube?

GhostRider62

Thread closed. Do you realize the risk of over inflating? This isn't a rim brake issue.

A tire/wheel issue landed me in the trauma center with 10 broken bones and two surgeries.