I_like_cereal

Whenever your LBS tells you that you have a dip and dice in your braking surface. DO NOT, I repeat DO NOT inflate your tires to 120 psi.

I did and it BENT the sidewall and peeled the brake surface off like tin can.

The best part was I had a slime tube in there and the rim shredded the tube.

It sounded like a gun shot went off and my ears are still ringing. I had slime everywhere. It was gross.

JohnDThompson 

Eww... nasty!

gitarzan

Sounds like a scene from a movie.

hardyt

OP, the dip goes under your lip and the dice hang off the review mirror, not on your braking surface!

Jeff Wills

I hate to say "I told you so", but... I told you so! At least you didn't have it go bang on a ride, in the rain, 20 miles from home:

Camilo

Why would you inflate your tires to 120?

blamp28

Some tires are inflated to 120 or more. My road tires (700x23) max out at 120. I've always thought of slime for larger mtb type tires though and those usually max out around 60 or 65 psi

clydeosaur

I run my 23's @ 110 - 120 all the time & have never had a problem.

jimc101

Simplest thing to do if any bike part looks worn is to replace, unless you understand that it could fail on you.

If you had replaced the rim, you would have saved the tube and tire; spend a little now, to prevent unnecessary costs later

mconlonx

Your new rim will come with a wear indicator. Pay attention to it...

HillRider

Just looking at what remains of your rim, it's apparent it was badly worn at the brake track. Overinflating that tire just made the inevitable happen sooner.

I inflate 700x23 tires to 120 psi routinely but I also try to replace badly worn rims before they fail.

MichaelW

That is called proof testing, best done whilst wearing eye protection and tough gloves. Its quite a useful procedure if you think your braking surfaces are a bit thin.

JPMacG

Please explain what a "did and dice" is. I have never heard that term before.

davidad

Why inflate a 32mm tire to 120PSI? https://www.adventurecycling.org/res...SIRX_Heine.pdf

FBinNY 

Unlike tubulars where the tire is a self-contained closed pressure vessel, wired-on tires are open on the bottom and require the rim to hold the sides in against the pressure. The stress on the side is proportional to the inflation pressure and the width of the tire.

Here's an easy to understand explanation of how to calculate the stress as related to pressure and cross-section.

Rims are built sufficiently strong to restrain the outward force of the tires they're designed for, but with brake wear progressively lose strength at the critical base of the flange. The point at which they blow apart depends on the tire pressure, and the tire width, and the amount of remaining strength, which eventually becomes inadequate to the task.

If you ever see any hint of cracks running lengthwise along the brake track it's time to scrap the wheel. For those who pick up stones in the brake shoes, a single deep score can be enough to kill the rim.

If your rims are deep enough you can push out the point of failure by mounting the brake shoes so that the brake track in within the box section of the rim and they don't remove material from the critical base of the tire flange.

HillRider

That's got some limitations too. The last rim failure I had cracked circumferentially right below the bead hook. Fortunately the only symptom was a noticable "tick" when I applied the brakes and the rim and tube held together long enough for me to get home.

Lesson learned: No rim last forever.

FBinNY 

That's the key, you can only buy time, but eventually rims die and need rebuilding.

I must either not stop enough, or have worse roads than most (probably true) because in over 100,000 miles of riding I've yet to ever wear out a rim's sides. My rims tend to die from impact damage, usually caused by rain filled potholes. It's kind of like getting hit by a bus before the coronary artery disease gets you.

coldfeet

Or at speed on a downhill, I cringe just thinking about it!

bkaapcke

Get Schwalbe marathon racers and forget the slime. bk

FBinNY 

Definitely will reduce the mess, but won't prevent rim failure.

xizangstan

I think I know why they invented disc brakes for bikes...

jeepr

Sounds exciting!

Jeff Wills

32mm tire on the back of a tandem or (in my case) a rear-wheel-biased recumbent. I chatted with Jan Heine a couple months back here in Portland about this article. Very interesting and very opinionated person. But he backs up his opinions with testing.

BCRider

Mountain bikers that used to ride a lot of downhilly areas in the days before disc brakes and lived in areas with LOTS of rain tended to go through at least one set of rims a season. Some went through two. The grinding action fo the mud in the pads combined with lots of energetic braking pretty much added up to "sanding" through the rim braking tracks in those heady days before discs became the solution for such riders.

I live up close to "The Shore" and talk with a fair number of riders that consider this crazily extreme riding site to be "just another EXTREME day in the park". Those with a few years under their belt if asked "what is the best ever tech introduction for mountain bikes would likely rank suspension forks as number one but then waffle back and forth over disc brakes or full suspension as number two and three from the stories I've heard.

1saxman

I've come back into cycling after a long hiatus, and I've read here before about the 'wear indicator' in a rim. What is it and how can you tell if a rim has it? If I had to guess, I'd say it is a dark-colored layer under the surface of the rim that becomes visible with wear. Am I close?