Oops I broke another rim.

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salty
Participant
#

Well, after I installed my new cassette, I noticed that the wheel was kind of badly out of true. But I thought – what the hell, I can’t be afraid of doing this forever. Since I don’t have a truing stand, I rigged up a zip-tie and I got that thing really close to perfect… I was pretty proud of myself.

I went to touch up one last spot that was a tiny bit out, on the opposite side of the wheel from where I had been working, and I noticed something a bit weird. At first I thought it was just the decal, especially since it was caked in grime… but then I realized the rim was broken. Then I found another spot (approx 90 degrees away) with the same thing.

https://picasaweb.google.com/116133033521423804230/BrokenRim2

Looking at the wheel picture, the broken areas are at approximately 6 and 9 o’clock. The valve stem is at 3 o’clock, and the spokes I was working on were generally from 1 o’clock to 4 o’clock.

So, question 1 is obviously could I have done this when I was truing the wheel?

I swear I did not touch the nipples where it is broken. (ok, I did turn the one for the “final touchup” but it was only 1/8 a turn and I’m pretty sure it was already broken before I did that.) It was all on the opposite side, near the stem. I was using 1/4 or 1/8 turn increments. I did some spokes multiple times but I think the most I turned any one spoke in total was 1/2 of a turn, but let’s say a full turn just in case. Would that be enough to break the rim on the opposite side?

I’m guessing I didn’t break it, and that was instead the reason the wheel was out of true to begin with, but I just don’t know… aside from messing around in the Free Ride class I’ve never done any wheel truing.

If it wasn’t me, then what? Was the wheel built improperly? Is it because of my fat ass (er, I mean the heavy amount of cargo I haul)? Should I get 36 spoker instead of 32? IIRC the cups on that hub are slightly pitted so I guess I might as well start over.


Drewbacca
Participant
#

There’s a good chance that the rim was already damaged and that was causing it to be out of true. Whether any fault lies with you depends on what the spoke tension was at; without knowing that, it’s impossible to say. Were you tightening and loosening simultaneously or just tightening?

FWIW there are some decent wheels at Handspun/QBP which cost less than the sum of hub, rim, and spokes at retail. I saved over $100 taking that route for a 36h xt/dt-swiss combo w/ disc hub and machined side-walls (WE7097). They have a Mavic 719/xt 36h combo that is rim brake only (WE7099).

Is there any reason NOT to get a 36 spoke wheel instead of a 32? It certainly can’t hurt.

ps. photo isn’t loading…


salty
Participant
#

Oops, link should work now.

I was tightening one spoke and loosening the two adjacent spokes each 1/2 as much, then re-testing.

I don’t have a tension gauge but i did notice even when i started by plucking the spokes that the tension (pitch) seemed pretty uneven.

The bike came with 32h, so last time I cracked the rim (which I believe was pothole related) I had a new wheel built with the same hub… but since the hub is messed up anyways I’m just going to get a new 36h wheel.


Chris Mayhew
Participant
#

You didn’t do that truing it. The wheel was out of true at least in part because of that.

Rims wear thru. Part of the gunk on your wheels is metal shaving from the rim wearing down as you brake. Put your fingers on the sidewall, I am sure they feel like this ) ( rather than | | like a new rim.

The main things to do are keep your brake pads clean. They pick up metal shavings over time that accelerate rim wear. In my experience Kool Stop salmon pads excel at not picking up metal shavings. Plus they last forever and increase braking power.

36 spokes is not a bad choice but it’s not going to solve your problem in the future.


dmtroyer
Participant
#

I had a rim crack like that over time on my Trek 520. I attribute it to being a shitty Bontrager Maverick rim, which has a (web) history of doing the same thing.


salty
Participant
#

Hm… the rim was only 1.5 years old, maybe had a couple thousand miles on it, and it’s a Salsa Delgado cross which seems to have a pretty good reputation. So, its definitely disappointing that it would fail so soon.

Good tip on the pads. I have kool stops on the front but not on the back.

Meanwhile my Bridgestone still has the original wheels despite having the crap beat out of it over the years – I can’t tell you how many pinch flats I used to get jumping curbs/steps/etc. Granted they’re heavy as hell but maybe Mr. Marv is on to something there…


rsprake
Participant
#

I have been riding a pair of Mavic A719 36h touring rims and they rule. Pretty sure they are the A719. Thick ordered them for me.


Greasefoot
Participant
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I had a Bontrager race light rim crack on me. It cracked on a crappy welded seam and put the wheel way out of alignment. The wheel was less then a year old and they would not honor the warrantee. Said it was due to normal use. I will never buy anything Bontrager again. I got 2 sets of Easton wheels and they are the fishizzle


Drewbacca
Participant
#

“I had a rim crack like that over time on my Trek 520. I attribute it to being a shitty Bontrager Maverick rim, which has a (web) history of doing the same thing.”

Yeah, I’m just waiting for my 520’s Bonrager Fairlane to go, based on web chatter. I might even rebuild the wheels with Velocity Synergies (same ERD) instead of waiting for the inevitable.

I had a spoke pull through the rim of a Sun MZ14 32h… it was beyond out of true if you noticed on the Cook’s forest ride; Marko did and made a comment about it at the time. I didn’t notice the crack at first because it was covered by the sticker.


dmtroyer
Participant
#

I’m having a very similar situation to Todd’s. Salsa Delgado Cross failing (cracks at the spoke holes) after about 2 years and a few thousand commuting miles.

I had it laced up by a reputable shop whom I trust. I never even had to true it in the 2 years I had it, but looking at it now, it seems the spokes tension could be way too high.

Probably time to call up Peter White, have a local dealer order through Handspun, or finally build a wheel myself.


reddan
Keymaster
#

Huh…interesting. I had multiple cracked spoke holes on a 2-year-old Delgado just a couple months back…I had assumed it was due to my incompetent wheelbuilding (and lack of spoke tensiometer), so just laced on a new rim and actually measured tension that time.


Chris Mayhew
Participant
#

My gut instinct is that it’s an issue with the rim and not spoke tension. You’ll actually just fold a wheel with too much tension.

Jobst Brandt’s book basically says “alternate tightening the spokes and gripping them with both hands till the wheel folds, then back the spokes off half a turn and true”. Worked for every wheel I’ve built.


dmtroyer
Participant
#

speaking of wheel building books… looks like I should have bought Gerd Schraner’s book when I put it on my amazon wishlist 3 years ago and it was available for 10% of what is going for now.


Anonymous #

You did not do that to the rim.

The rim failed <period>.

From the looks of the damage, the problem **appears** as if the spoke was sitting/pulling against a single wall of the rim.

Rims do wear out, I’ve done it – right through the braking surface…

Aluminum, while lighter has one major draw back in high stress service, it fails catastrophically; that is it does not give a warning. Steel will bend, aluminum just fails.

This is exactly what you are seeing here.

Anyway, replace the rim(s), get a good double walled rim, if this is a bike you beat (lots of of-road, trials, etc) get something that is hardened.


eMcK
Participant
#

Even with a double wall rim, the nipples only pull on a single wall of the rim. In fact, single wall rims are often thicker at the spoke bed, because the extrusion needs to thicker since there isn’t a second wall to add strength and stiffness.

If your wheels lose tension over time (which most wheels do), the spokes go through a bigger tight to loose cycle as the wheel rolls, increasing the chances of fatigue cracks around the spoke holes, but even tight wheels can have this problem. I’ve seen (and ridden) wheels that lasted for months after the cracks developed. A few had impacts can turn a small crack into what you have here.

More spokes and stronger/heavier rims will help prevent this, along with regular tension checks, with a tensiometer, doing this stuff by “feel” is guesswork at best. Even experienced fingers and hands aren’t anywhere near as accurate as a well calibrated tool.

Also, I’ve seen plenty of aluminum parts bend and not break, and steel parts break with no warning, there aren’t any hard and fast rules about this stuff. This rim is a perfect example of an aluminum part NOT failing catastrophically, the cracks and bending seen here served as a warning to replace the rim before it really fails.


Anonymous #

Eric,

not to get too technical…

but catastrophic failure is not necessarily catastrophic :)

catastrophic failure means the material fails – cracks or breaks rather then deforming under stress. So, technically each of the rivet pull throughs on that rim are catastrophic failure, the rim material has failed.

IF the rim had been steel, the rim would have bent/deformed rather then breaking.

This is not to say that steel can not fail catastrophically, all materials can fail catastrophically if they are loaded beyond design.


Pierce
Participant
#

Perhaps get something big and heavy from Thick?

I’ve got a Velocity Dyad that seems to be holding up pretty well and I probably carry our weight difference and more in panniers most days

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