Mountain Biking - my rim exploded!

so at the end of last summer my rims were concave from wear from my v-brakes. the front was a little more worn and i thought it could be really dangerous if the front blew out durnig a descent, so i replaced it.

i neglected the back and got the bike out last week (rode the hardtail during the winter) and noticed that i needed to replace the rim soon.

so about 15km into our ride on a rooty downhill section: BOOM! the rear rim completely exploded. anyway, it was no big deal and luckily a friend lived nearby and rode back and picked up another wheel, spin off the cassette and put on mine and i was ready to ride again.

anyway, i had heard that the rim could explode if the braking surface gets too thin from braking, and yes, it's true. the whole bike was new end of March 2002 and i rode 3800km and 65,000meters vertical and BOTH rims were trashed... makes me think next time i might actually consider disc brakes...

i've attached 2 photos of the blown out rim:

image 2:

dang. me thinks I should buy some new rims soon.

Good work...I have never seen that before :)

That happened to me once, too. I was coming downhill at about 25-30 mph and BAM!!! It sounded like a shotgun going off. Luckily, I wasnt hurt. I still have the rim...kinda like a trophy...

nathank braking is a weakness :)

Man, I've never seen that before. I had my other bike for like 5 years and never experienced a problem.. still had plenty of surface left on them. I guess it's time for discs, eh? :D

My rims don't last long enough to wear thru their braking surfaces. I've usually tacoed them long before any noticible wear!

btw, good one Ton!

L8R

Originally posted by a2psyklnut
My rims don't last long enough to wear thru their braking surfaces. I've usually tacoed them long before any noticible wear!

btw, good one Ton!

L8R




Atta boy :thumbup:

I was talking to one of the bike shop owners in my area the other day this came up in conversation... He said that on serious downhills when using Vbrakes for long periods of time it heats the rim up so much that it will explode.... well at least whatever it did to you in the above pic.

I'm curious, were these tubeless, or did it coincide with a tube blowout, or did you hit something wrong? Where did the force come from to cause this "explosion?"
Very interesting

Originally posted by iamlucky13
I'm curious, were these tubeless, or did it coincide with a tube blowout, or did you hit something wrong? Where did the force come from to cause this "explosion?"
Very interesting Usually what happens is the rim surface wears down from braking to the point that the center if very thin. Then a half way decent impact (fast downhill, ride over a big rock for example) causes the sidewall to start to fold. Once that happens it's all over. Tire pressure is pushing out on the rim sidewall, the thing will start to split and next thing you know an explosion happens and aluminum ribbons are flying!


As you can probably tell, this has happened to me - on several occasions over the years.