# How can I tell if my rims are work out?



## steve_e_f (Sep 8, 2003)

Howdy. I've been riding a pair of Mavic K-SSLs since 2004, and I've started to wonder if I should be concerned about the breaking surface or sidewalls wearing out on them.
I don't have any reason to think anything is wrong with them, and the wheels still perform like day 1, but I've heard of catastrophic failures and I want to be informed.

I don't really log my miles, but I train and race all year on the same wheels.

Has anyone got any advice, or is this just something you have a shop look at?

thanks!

-SF


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## Kerry Irons (Feb 25, 2002)

*Curvature*



steve_e_f said:


> Howdy. I've been riding a pair of Mavic K-SSLs since 2004, and I've started to wonder if I should be concerned about the breaking surface or sidewalls wearing out on them.
> I don't have any reason to think anything is wrong with them, and the wheels still perform like day 1, but I've heard of catastrophic failures and I want to be informed.
> 
> I don't really log my miles, but I train and race all year on the same wheels.
> ...


Look at the sidewalls and see if there is significant inward curvature (concave surface). If you want to get anal about it, you can lay a straight edge in the radial direction and see how much of a gap there is between the sidewall and the ruler.


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## GH-Mike (Jan 20, 2007)

*lennard zinn says*

I read this on velo news recently. made me think of my own wheels.

Text and link

http://velonews.com/article/86509/technical-qa-with-lennard-zinn---readers-ask-lennard-answers

Dear Lennard,
A cyclist who assisted me with a double flat situation last year told me that side walls of alloy rims wear over time and that a wheel or rim should be replaced on regular intervals to avoid catastrophic failure of the braking surface. I have a set of 4-year-old bullet straight Eurus wheels approaching the 20k mile mark and wonder if this is a valid concern.
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I had never heard of this in over 35 years experience on various clincher and sew-up wheel setups. Please clarify that this is or is not the case as I wonder if sidewall thicknesses have been reduced over time to save weight or was this a salesperson’s story to empty his wallet unnecessarily. How would one measure the rim thickness?
Bob

Dear Bob,
Absolutely this is an issue. The EU recognizes it as such and requires rim manufacturers selling within the EU to have wear indicators on their rims. This rule is at least a few years old, so I wouldn’t doubt it if your rims even have them. Inspect them carefully.

The indicators vary, but some are small, blackened-in holes or grooves cut in a prescribed depth into the braking surface. When they disappear, the rim is too worn to continue using. Others are small voids inside the rim wall at a prescribed depth inside. When the rim is worn enough that they are visible, ‘tis time to replace the rim. Mouse over the second to last red and black icon on the row of icons above the wheel photo on this page, where you can find the DT Swiss rim wear indicator.

These rim wear indicators are analogous to car-tire wear bars (a.k.a. wear indicators). These are raised features at the base of the tread grooves that indicate the tire has reached its wear limit. When the tread lugs are worn to the point that the wear bars connect across the lugs, the tires are fully worn and should be taken out of service.

I have certainly seen rims fail from the braking surface becoming worn too thin, and it is not particularly pretty. It usually happens under hard braking, when the pad wears through the final amount necessary – the straw that breaks the camel’s back, combined with the elevated air pressure due to the rim heating up from braking. Then the tire blows right off of the rim as the rim wall folds outward.

A good rule of thumb is to examine (or ask your bicycle dealer to do so) the remaining thickness of the braking surface of your rims (with a micrometer) before your second set of brake pads is worn out. Don’t wait until the rim wall is worn so thin that it fails.
Lennard


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## pdainsworth (Jun 6, 2004)

Not sure about your Ksyriums, but some Elites I used to have had two little dots, or indentations, on the sidewall. The idea was that if the dots disappeared, the rim was worn out. Don't know if it was on all of the models, though.


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## Puchnuts (Oct 9, 2008)

My Mavic A719 rims have those as well. Some do, and some don't with Mavics. No sign of the 'dot' on my Open Pro Ceramic set.


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## steve_e_f (Sep 8, 2003)

Thanks guys. I'll look for the dots on mine. I've never noticed them, but I'll check. I'm pretty sure they have some concavity.


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## charlieboy (Sep 10, 2003)

*don't let them get this bad!*

I read your o p last week and went and checked my rims on my 7 year old (!) winter training wheels - they looked OKish, but a weekend of wet and gritty weather finally put paid to the rear rim! Under braking noticed an intermittent noise and sure enough a better check showed the damage.

Front rim is fine but I'm rebuilding as a pair.

Seven years winter riding in poor road conditions on wet and muddy winter roads in UK - pretty good service I guess.


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## California L33 (Jan 20, 2006)

charlieboy said:


> I read your o p last week and went and checked my rims on my 7 year old (!) winter training wheels - they looked OKish, but a weekend of wet and gritty weather finally put paid to the rear rim! Under braking noticed an intermittent noise and sure enough a better check showed the damage.
> 
> Front rim is fine but I'm rebuilding as a pair.
> 
> Seven years winter riding in poor road conditions on wet and muddy winter roads in UK - pretty good service I guess.


Watch for the concave wear marks the brakes leave. You left that rear one a bit too long and could have had something nasty happen. On the other hand, if you hadn't taken a hack saw to it, you probably could have used the front one a while longer  

Speaking of that, do you not use your front brake often? That's where most of your stopping power is.


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## charlieboy (Sep 10, 2003)

*braking style etc*

yes, I took that rear rim to its limit  The front rim was sacrificed in the interests of science or curiosity, take your pick 

When I were a lad we were taught to apply rear brake first then front brake, to avoid a trip over the handle bars (you do it once and learn your lesson, mine at a major intersection in the rush hour when I was 18!). Brakes were grabby back then.

Old habits die hard and that's how I brake 32 years later!


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## foz (Sep 30, 2004)

charlieboy said:


> When I were a lad we were taught to apply rear brake first then front brake, to avoid a trip over the handle bars (you do it once and learn your lesson, mine at a major intersection in the rush hour when I was 18!). Brakes were grabby back then.
> 
> Old habits die hard and that's how I brake 32 years later!


We were taught lots of daft stuff when we were kids... there's no way you'll go over the handlebars if you brake on the front first, or only with the front. If you brake mostly with the rear brake then it's probably more likely that you won't stop in time and will crash into whatever you're trying to avoid, if it's an emergency braking situation.

As for brake wear indicators, AFAIK there are three types - the first is a groove that runs all the way around the rim in the braking area. when it disappears, the rim is worn out. The second type is similar to the groove, but is just a small hole. When it disappears, the rim is worn out. The third type is a hole on the inside of the braking area, which is normally not visible. When it becomes visible, the rim is worn out. This type of rim usually has a sticker somewhere pointing to the place where the hole will appear, to make it easier to check for and find.

foz


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## charlieboy (Sep 10, 2003)

*oh yeah, face plant baby*



foz said:


> We were taught lots of daft stuff when we were kids... there's no way you'll go over the handlebars if you brake on the front first, or only with the front. If you brake mostly with the rear brake then it's probably more likely that you won't stop in time and will crash into whatever you're trying to avoid, if it's an emergency braking situation.
> 
> 
> 
> foz


Foz you've obviously not lived  Like I said, I learnt my lesson, emergency stop with front brake only and straight over the bars, laid in road wondering 'how did that happen?' Believe me it did.

Annyway we're getting off topic here so enough.


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