Rim question.

[Manx Cat]

My winter commute gal has on the outside of her rim the words:

When rims wear down, replace as riding with worn rims is dangerous' or something very similar.

Thing is..... How do I know if my wheel rims are worn out or not? They are quite smooth. Is there a gauge for this?

MC

[tooley92]

Not sure if this is the case with your rims Mary, but most rims have some sort of indicator built in to the side wall (often a groove that disappears or cavity that appears as the rim wears).

What make are your rims? I'm sure someone will know if they have a wear indicator or not.

[hubgearfreak]

here you go....

viewtopic.php?f=5&t=18238&p=147656&hilit=rim+wear+rim+failure+pump

[Brucey]

newish rims have a groove or small dimples in the rim braking face. When these disappear the rim should be due for replacement.

You can measure the thickness of the rim with vernier calipers, but sometimes you need to use a spacer because otherwise you just measure the thickness of the rim lip. Rims typically fail at a thickness of 0.9 to 0.6mm but this varies with type, tyre, and running pressure.

Another method is to measure the outside width of the rim and make a note of it. Very often a worn rim will bow outwards under tyre pressure when it is worn thin. You need to measure in several places, because they are rarely the same thickenss right the way round.

cheers

[Valbrona]

Thing is..... How do I know if my wheel rims are worn out or not? They are quite smooth. Is there a gauge for this?

No gauge. With the lack of any type of wear indicator marking, like a groove, you factor in amount of usage and you make a guess ... erring on the side of caution.

[531colin]

Of course theres a gauge.....

[eileithyia]

When you can see the end of 4 spoke nipples thru the side wall of the rim... it has worn out.

Worn side walls were beyond my early experience, my bike had been making a bit of a funny noise when ridden the previous day(!) when I noticed the problem! When I did the calculation the rim had been used fairly heavily for 6 years, don't think there was a rim indicator at the time.

[patricktaylor]

As a rough guide on rims with no indicator groove you can lay the edge of a credit card (any plastic card) across the side of the rim to see how much of a hollow the brake pads have worn. If there isn't a noticeable hollow I would imagine the rims are still ok.

[phil parker]

I have a specific rim gauge for measuring wear, but unfortunately it doesn't cater for all situations.

Last year I had an Open Pro rim split (I will attach a photo later) but the line of failure was at the same point on the rim as the joint for the strengthening 'top hat' section and therefore no amount of pre-measuring could predict the imminent failure.

[Brucey]

As a rough guide on rims with no indicator groove you can lay the edge of a credit card (any plastic card) across the side of the rim to see how much of a hollow the brake pads have worn. If there isn't a noticeable hollow I would imagine the rims are still ok.

this is indeed a good guide, but very often the 'hollow' is not just wear, but also because the rim has deformed outwards at the edge because it is thin and no longer strong enough to resist tyre pressure forces.

Won't always help if the worst wear is in the box wall though, as others have pointed out.

cheers

[531colin]

I can't help thinking that Rigida had this nailed.
The rims are joined by 2 steel pins......as the rim is an alloy extrusion, the holes for the 2 pins run all round the rim.
Its set up so the brake blocks wear through into little "ears" on these holes before the rim is dangerously thin.

[531colin]

My winter commute gal has on the outside of her rim the words:

When rims wear down, replace as riding with worn rims is dangerous' or something very similar.

Thing is..... How do I know if my wheel rims are worn out or not? They are quite smooth. Is there a gauge for this?

MC

What make/type are the rims?
Somebody on here will know if they have a wear indicator.
If there is an arrow on the label warning of wear, it will point to the bit of rim where it is machined from the inside....when this bit wears through, bin it!

[Valbrona]

Of course theres a gauge.....

I would expect that not to be accurate enough.

If a gauge like this could do the job I think you would be able to buy them in the shops with 'Part Tool USA' on them or 'VAR'.

[531colin]

Thing is..... How do I know if my wheel rims are worn out or not? They are quite smooth. Is there a gauge for this?

No gauge. With the lack of any type of wear indicator marking, like a groove, you factor in amount of usage and you make a guess ... erring on the side of caution.

OK, you guess it if you like....I'm sticking with a vernier gauge

[Brucey]

I'm with colin.

Those verniers have been modified by grinding away parts of the original calipers; the faces that do the measuring are as they were before, i.e. should be accurate to 0.05mm or so. If they were not, it would be incredibly easy to tell when the calipers were set to zero.

Thus far I've made do with spacers of fixed width to overcome the geometry issue, but since I have a spare set of calipers, I may modify them similarly.

Guessing.....

cheers