Rim Wear Measurement

dave r

Dunking Diddy Dave Pedalling Pensioner
How does that gauge work then?
The pincers on the end of the guage go either side of the rim and the pointer at the other end registers the rim thickness on the scale.

dave r

Dunking Diddy Dave Pedalling Pensioner
The front wheel rim thickness on my fixed varies between 1.5 and 1.25 mm. It looks like it will be OK for the rest of this winter but it'll need changing before I use it next winter, I'll be keeping an eye on it for now.
I am quite encouraged by this thread. I have never worn through a rim, being a bit on the heavy side, I am much more used to cracking rims between spoke holes. I do, though, have a pair of "tough as old boots" Campagnolo Sciroccos, which are getting spectacularly concave, on one of my winter Bianchis. I think I will keep riding them till they go in holes!


Flouncing Nobber
Y old fashioned Eyeball Mk1 can see that is borked from dozens of miles away.

I use the straight edge of a steel rule, but have never yet needed to replace a rim.


So, on the excellent advice of @andrew_s I purchased an iwanson gauge to check out my rear rim wear.

It had been grabbing a bit breaking, which I *assumed* was because it's a bit out of true too, so I was intending to take to LBS for a retrue.

So, having taken it off, I have a look and fucj me, it's absolutely bolloxed, completely worn away to the hollow section inside around 2/3 of the rim!

The gauge, however, shows minimum 1mm thickness, so I'm not sure how useful it really is.

How the thing continued to work at all is a bloody miracle.

Anyone ever seen a rim in worse condition still rideable?
View attachment 500166
That deep groove is the rim wear indicator. Once it appears, it's officially time to replace the rim.

It's a pretty good indicator - very difficult to fail to notice, and even harder to ignore for a while on the grounds that the indicator will be set to warn well before actual failure (which it is). This indicator is likely to provoke a reaction of "Aaargh - me rim's borked! Get a new one now!", unlike disappearing grooves or pits that leave you wondering if there was ever anything there, even if you do think to look.

Here's a cross-section of a similar rim (Sputnik), showing that there isn't any immediate danger of failure :-

Back before indicators were common, I did have a rim wear almost into the spoke cavity, then split all the way round one side in one go after I hit the side of a taxi (as on the right of this cross section).

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I do, though, have a pair of "tough as old boots" Campagnolo Sciroccos, which are getting spectacularly concave, on one of my winter Bianchis. I think I will keep riding them till they go in holes!
If the rims are spectacularly concave because the rim flange is starting to bend outwards, they can fail very quickly.

When you brake, the brake blocks push the bent flange back in, then tyre pressure pushes it back out. The resulting wiggling back and forth cracks the flange, and once it's cracked over a long enough distance, the tube forces its way through and goes bang, very loudly.

Bent flange

Cracked, bent flange

Usually you can feel a pulsing in the brakes at the initial crack. If you then check, and find the initial crack, let half the air out the tyre and limp home without using the brake on that wheel.
You can also check for bending flanges by measuring the outside width of the rim by the hook with the tyre flat, and again with the tyre at full pressure. If there's a difference, the flange is bending.


Senior Member
I've never worn a rim like the ones shown:angel:.
But then again I tend not to brake at all, if possible, as this tends to slow me down.:whistle:
The rims on my 11year old trike are pristine,:becool: but that's got something to do with the Drum brakes.:rolleyes::whistle:

I'll get me coat on the way oot!:laugh:
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