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Old 12-09-02, 11:39 AM   #1
roadbuzz
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When do you replace rims?

I was looking at my rims (Mavic Open Pros) after yesterdays ride and was wondering... I don't want to get caught 30 miles south of East BF with a hosed rim.

What should I look for when checking for impending failure... there's nothing obvious, but that doesn't always mean much. Are there any rules of thumb re/life expectancy?
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Old 12-09-02, 08:28 PM   #2
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Very relevlant question! I wish I had a thorough answer.

Pay close attention to the seam/weld and to brake-induced wear on the sidewalls. It also probably makes sense to replace a rim after 20K mi/30K km or so, unless you are a very lightweight, cautious rider.
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Old 12-09-02, 09:48 PM   #3
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An unatural warp (the feeling of vertical warp not the usual look down and see)

No matter how often you rebuild they warp quickly (sign of cheap rims or worn rims)

Check the eyelettes for cracks or stress marks

Check the welds (if there are any) on the rim and make sure there is nothing visually wrong.

Take the tube out and inspect the inside while shining a light at it. This will show off any possible hairline cuts.
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Old 12-10-02, 01:38 AM   #4
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You will notice now that current 517's, bontragers & other brands are putting wear detents on the braking surfaces so you know when the sidewalls are too thin.
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Old 12-10-02, 05:56 AM   #5
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How can weld failure lead to rim failure? The rim is under compression, and is conventionally held by just a simple metal peg ?
The worst kind of failure is probably due to worn braking surface.
You can proof test by overinflating the tube using a track pump. Wear safety goggles and gloves in case of an explosive failure, and dont forget to release the pressure after the test. Chris Juden of the CTC recomended 50% above the max pressure for proof testing.
Modern rim-wear indicators, introduced by the Belgium company, Alesa, are a very good idea.
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Old 12-10-02, 11:07 AM   #6
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Based on what I have read on this thread, I am curious how the following would be interpreted by you guys as far as wear goes.

Something I noticed on my rims after I rode in the rain was a pattern of wear. I am assuming the paint was rubbed off a bit (lots of hairline scractches (not cracks)) from the gunk that got between the pads and rims.

Now the odd part is, the wear of the paint gives a dashed appearance. By this I mean the space inbetween the spokes has less wear than the part of the rim in line with the spokes. I can't feel any warping by hand, but you can definately see that the warp exists based on the paint wear.

Is this something normal, or should I be concerned about it? Otherwise the wheels stay very true and give me absolutely no problems.
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Old 12-10-02, 11:22 AM   #7
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Thanks, guys. I'm neither lightweight or cautious. And foolish doesn't count. Sounds like I'm getting into the grey area, mileage wise.

But then, as Pokey says, 'everyone wants new wheels.'
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Old 12-10-02, 03:20 PM   #8
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Quote:
Originally posted by roadbuzz
What should I look for when checking for impending failure... there's nothing obvious, but that doesn't always mean much. Are there any rules of thumb re/life expectancy?
My opinion is that if they are properly designed and made, rims should wear from the brake track wearing out. Since riding conditions and pad/rim combinations vary, the only way to be sure is to see how much material is actually there. Without calipers, I don't know how you'd measure this accurately with clincher rims. I wouldn't worry about it unless you can feel a lot of concavity )_( with your fingers.

From what I have seen, with modern rims, it's more likely that they will fail at the eyelets long before the brake track.
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Old 12-10-02, 03:24 PM   #9
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Quote:
Originally posted by Sailguy
Now the odd part is, the wear of the paint gives a dashed appearance. By this I mean the space inbetween the spokes has less wear than the part of the rim in line with the spokes. I can't feel any warping by hand, but you can definately see that the warp exists based on the paint wear.

Is this something normal, or should I be concerned about it? Otherwise the wheels stay very true and give me absolutely no problems.
If the rims are quite worn I would be somewhat concerned. The thickness of machined rims varies and you could be down to the wire.

How many spokes do these wheels have?
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Old 12-10-02, 04:09 PM   #10
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Originally posted by bikerider


If the rims are quite worn I would be somewhat concerned. The thickness of machined rims varies and you could be down to the wire.

How many spokes do these wheels have?
The wheels have 38 spokes. Before the rain, there were no marks on the rims at all. It wasn't until some of the road grime got in between the pads and the rim did it mar the finish a bit.

I will try to get a photo up this eve.
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Old 12-10-02, 05:26 PM   #11
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Quote:
Originally posted by roadbuzz
What should I look for when checking for impending failure... there's nothing obvious, but that doesn't always mean much. Are there any rules of thumb re/life expectancy?
I'm no expert but if you can dent the rim with a fingernail, see light through it, or it resembles a pretty girl's waistline )__( you've got problems. One other thing to look at is if the spot where the spoke meets the rim is raised like an infected hair that's most likely not a good thing. I like new rims you should too.
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Old 12-10-02, 05:42 PM   #12
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I had a Mavic Open Pro rim with a hairline crack radiating out from a spoke hole. It was almost invisible with the bike on a stand, but when riding I kept getting a "creak, creak" sound like a rocking chair and periodic broken spokes. Eventually it became pronounced enough that even I was finally able to spot it.
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Old 12-10-02, 07:44 PM   #13
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Quote:
Originally posted by Sailguy
Before the rain, there were no marks on the rims at all.
That's not uncommon. I had a pair of anodized rims once that looked great for months, 'til I got caught in the rain. I guess the water makes the difference, kind of like water on a whetstone. Roadgrime without the water doesn't wear nearly as much. BTW, they also had a similar wear pattern... the rims bulged a little near the spoke holes, causing more wear. (36 spokes.)

Last edited by roadbuzz; 12-10-02 at 07:50 PM.
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Old 12-10-02, 07:49 PM   #14
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Quote:
Originally posted by Raiyn
where the spoke meets the rim is raised like an infected hair that's most likely not a good thing.
Now, there's an image that I won't soon forget. [insert puking smiley]
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Old 12-10-02, 08:41 PM   #15
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The wheels have 38 spokes.
Please send us a picture. A 38 spoke rim sounds very odd, indeed. Just how is a 38-spoke wheel laced, anyway?
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Old 12-10-02, 11:25 PM   #16
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Quote:
Originally posted by roadbuzz

Now, there's an image that I won't soon forget. [insert puking smiley]
You mean like these guys?
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Old 12-11-02, 01:20 AM   #17
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Thirty eight? Not thirty six? I don't think I have ever seen one of those gomers. Yes - please post a picture. And the brand name?

Cheers...Gary
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Old 12-11-02, 01:37 AM   #18
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Sorry guys, 36.. you can flame me now. I am never good w/ that kind of data in my head. Here's some pics of the wear.

Notice the increased wear at the spokes. Sorry for the glare, the flash did a number on the picture.. I toned it down in photoshop the best I could.
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Old 12-11-02, 01:47 AM   #19
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2nd Pic
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Old 12-11-02, 02:20 AM   #20
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Like this38
Or this?
Maybe this?


Heh!!
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Old 12-11-02, 02:24 AM   #21
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I feel better now
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Old 12-11-02, 04:08 AM   #22
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From what I have seen, with modern rims, it's more likely that they will fail at the eyelets long before the brake track.
not always. i bought a new bike in April 2001, so obvioulsy i had new rims. well, by the end of the summer my front rim brake surface was REALLY concave!

i thought i had a little more life on it, but a friend of mine kept telling me it was about to go and VERY dangerous, as he had seen 2 rims bust through while the rider was going fast downhill. anyway, it was very worn, but on examination it was very concave, but still had some thickness left (no number, but at least say 1/3 the original width). i do like the idea of wear bars though.

of course, my riding is probably not average. i ride almost all mountains (with this bike) and logged about 4000km and 61,000 meters of vertical which means also 61,000 meters of descent! on mostly single-track so lots of hard braking involved.

i think in normal riding without extreme braking it is generally more common to wear out at the spokes - crack radiating out from the spoke holes. that's why i was so surprised that my rim was toast after only 6 months! b/c rims usually last a lot longer.
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Old 12-11-02, 04:21 AM   #23
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Perhaps discs would be a good move?
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Old 12-11-02, 06:16 AM   #24
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It looks to me as though you are talking about wear of the braking surface at the spoke positions being different than between the spokes.

If that is the point, wouldn't that mean that the rims were bulged out at the spoke positions (or the other way around, dependent upon which area shows more wear)? Do the wear patterns repeat on both sides in the same places?

In either case, possibly dangerous eventually, I would suspect.

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P.S. Why flame? I need another person around to count past twenty. 8')
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Old 12-11-02, 08:16 AM   #25
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Quote:
oeiginally posted by Raiyn
Perhaps discs would be a good move
yeah, i've not been a fan of discs - more weight, more to break, cost more, more complicated - and my Avid Single Digit Tis work great and a beautifully simple and never break

but, i gave disc another thought after the rim thing - b/c with discs you don't brake on the rim so it would last longer. but here's my thinking: so i were out maybe an extra rim a year (i.e. use up 1 front rim per year instead of every other year). cost is about $40 every 2 years or $20 a year. i think the cost of discs plus the extra maintenance would be more than $20/yr considering how much i ride. i mean disc pads costs more than v-brake pads and riding so much with so much downhill has got to use up disc pads too. then there are the maintenance/breakage b/c discs are just inherently more complicated than super-simple v-brakes: one of my friend's hydraulic line broke, another got air bubbles and had to replace the unit, another warped a disc in a crash, and another had a weird thing where the disc pad rubbed while coasting... i've had absolutely ZERO problems with my v-brakes in like 4 years and maybe 40,000km! and tons of crashes - broken nose, 2 chipped teeth, torn lip, broken bar-end, bent shifters, and my v-brakes never got damaged or worn!

maybe in a few years when discs are more refined i might think about it.

actually, i did find another advantage to discs the other day but it doesn't happen much: when riding in snow the v-brake stopping power was affected and snow clogged up in the v-brake unit (of course, it clogged up in the drive-train too which discs wouldn't solve... i'm am more likely to try the Rolph hub unit instead of discs) the Rolph looks really neat although it's pricey and a little more weight.
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