How do you know if your rims are worn?

[Glover Fan]

Hi all,

I don't have rim wear indicators on my current do-it-all bike wheels. They are Shimano RS10's, which have done 6,500 miles. The other day whilst cleaning, I noticed that there was an inner curve all the way round the rim where the brake blocks have worn them away. I could rest my fingertip in nicely, which is slightly concerning.

Is this the sign? Or are there actual ways of measuring rim wear?

[Biggsy]

That is a sign, but you could measure to learn exactly how much metal is left, perhaps with this gauge*, then find out from other users or Shimano what the safe limit is for that particular rim.  Measure at several points around the rim in case the thickness is uneven.

* Description says it starts from 1 mm, but actually it starts from 0, as I told the seller some years ago.

[vorsprung]

If you think they are old and if they have a concave feel to them them replace them!

Rims are cheaper than a wheel failure in the middle of nowhere.  The one time I had a rim wear through, it was a on a descent.  The braking action ripped the last bit of metal out of the front wheel and the inner exploded.  I wasn't going too fast at the time thankfully

[Glover Fan]

It has a fairly concave feel to it.

I suspect knowing my luck it will go mid-way through the Dartmoor Ghost at 2am next week.

Looks like I will need to hasten my purchase of some open-pros.

[Kim]

Stands to reason that rim failures are most likely to happen when you're braking, which is bound to maximise the inconvenience.

If it's concave enough to feel, I wouldn't trust it - especially on the front.  Replace with something that has a wear indicator, and save yourself the worry.

[Rhys W]

If they're so concave your finger fits snugly in, you're living on borrowed time.

We had a rim explode on last week's clubrun - the hook broke away from the sidewall on a section about 6-7 spokes long. His rims were exactly like that - my fingertip fitted into the groove nicely. I've never seen a rim that worn, they should have been replaced many months earlier!

[Manotea]

One clue is if you can see through the holes...

[edscoble]

Is this the sign? Or are there actual ways of measuring rim wear?

Yes, replace as soon as possible, even if the wear is miminal, people often forget to replace the rims thinking there's "one more ride left in it".

We get a lots of customer with split rims, much more common than you'd think.

[Crumbling Nick]

Is this the sign? Or are there actual ways of measuring rim wear?

It's not The Sign, but is an indication of quite a bit of wear.

There are ways of measuring remaining rim thickness, which is what matters. Biggsy's suggestion is a good one. Alternatively, if you have a pair of vernier calipers (or even a micrometer, which I don't own) , you can bend up an old 2mm spoke to fill up the hollows on the inside & the outside of the rim (due to the hooked tyre bead retainer inside & brake wear on the outside). It's something I've picked up from an article by Chris Juden in CTC's Cycle magazine, but I  can't find an an online reference, & couldn't in in 2010. If you need an explanation, I'll do my best to explain how to bend the spoke.

Chris concluded that failure occurred typically with a rim thickness of 0.7mm & advised that it would be unwise to ride with a thickness less than 1.0 mm.

I have no idea how thick Shimano RS10s are. I tend not to believe what others say on this subject without doing my own measurements. I found Open Pros had always been a lot thinner than others believed (consistently 1.3mm vs a claimed 1.6mm). I still use them, but only with a (mainly) leg-braked fixed wheel.

You don't seem to have a lot of time to sort out this one before the Dartmoor Ghost and, without resorting to the hype of some previous contributers, getting it wrong has a risk. If you have space to store a spare rim/wheel or 2 (and are not strapped for cash), I'd suggest installing replacement(s) for the ride & working out whether it was really necessary afterwards.

HTH

[Tim Hall]

Alternatively, if you have a pair of vernier calipers (or even a micrometer, which I don't own) , you can bend up an old 2mm spoke to fill up the hollows on the inside & the outside of the rim (due to the hooked tyre bead retainer inside & brake wear on the outside). It's something I've picked up from an article by Chris Juden in CTC's Cycle magazine, but I  can't find an an online reference, & couldn't in in 2010. If you need an explanation, I'll do my best to explain how to bend the spoke.

Here's a link to the Chris Juden bent spoke method:

http://forum.ctc.org.uk/viewtopic.php?f=5&t=18238

Scroll down a wee bit.

[Greenbank]

Search eBay for:

BICYCLE RIM GAUGE DEUXIEME GAUGE

They're £4 or so and make it easy to measure rim width without needing to do the spoke trick.

[Rhys W]

The problem with trying to measure rim thickness is that you're not necessarily measuring in the right place! I've had a rim fail where the wear indicator was still intact - the brake block on one side was set a little high so most of the wear was slightly above where it should be. Measuring that rim would have said "fine, carry on" whereas a close visual inspection would have aroused my suspicions.

[edscoble]

To be honest, if the rims is worn, surely it's best to replaced them, even if it's very slight.

Especially, most especially on a bicycle you ride audax on.

[Biggsy]

You'd replace your rims after every ride if you tolerated only a very slight amount of wear!  But Glover Fan's has a lot of wear.

[edscoble]

Hardly, it would take a year, or two to get them concaved slightly, less if neglected (cheap brake pads, not cleaning rims, etc.)

[Pickled Onion]

I guess the point is how do you know when to change them before they fail, but not too much before. There's no point replacing things unnecessarily.

I've just last week worn out a rim on an all-year all-weather commuter and it's done almost 40,000 km. If I'd changed it when it felt a bit concave, I'd have been through five or six rims over the same period. That's quite a lot of money, compared to the price of a rim gauge.

[Biggsy]

Yes, I was being pedantic, to make the point that wear is a gradual process and you have to judge how much to take.  It doesn't go suddenly from no wear to concaved enough to notice.  It's not an easy decision, unless you've already left it late, like perhaps GF has.

I wonder if some thin-walled rims should even be replaced before they're obviously concaved?

[matthew]

The other test is to pump up your tyres to ~150% of normal pressure.

However DON'T do this the day before a big ride as this is a destructive test if they fail and DO wear ear defenders if you think they might fail.

[Glover Fan]

Thanks for the replies.

I must say I am disappointed. I don't use the brakes all that often and I clean the rims. I use Koolstop Salmons which are a soft compound, so would have expected further than 6,500 miles on these wheels.

Like all things, financially it couldn't have come across at a worse time. I was going to go down the open pro route in about October time, but I might have to just buy a set of RS10's again as they are only £90 on Ribble at the moment.

I can no longer do the Dartmoor Ghost, so I will be doing a 200 on my best bike instead.

[edscoble]

I would hardly call a rims that last 6,500 miles a disappointment, far from it considering some of the touring bicycles I've seen in my shop have rims worn out half that distance.

Obviously it's a different kettle of fish when the bike is fully laden with everything but the mortar required to build a house.

[LittleWheelsandBig]

Given that some tyres exceed that mileage, I'd consider that pretty poor.

Rim sidewalls used to be significantly thicker but the manufacturers 'moved' that material to make deeper section rims designed to hold up under fewer spokes.

[mattc]

I _think_ i've got a pair of these wheels still in their box! Apologies if I've got the model wrong ...

If it will help I can stick a vernier caliper over the things. I don't own a specific rim guage currently.

[edscoble]

Aren't there's too much variation when it come to tyres? some last forever, some last 12 second of staring at it.

[Biggsy]

I must say I am disappointed. I don't use the brakes all that often and I clean the rims. I use Koolstop Salmons which are a soft compound, so would have expected further than 6,500 miles on these wheels.

Have you done a lot of wet rides?  Rim wear is many times worse when wet than dry, and you can't be expected to keep on cleaning and drying your rims and pads during rides.

Also regularly check for bits of metal and grit stuck in the pads (though Kool Stops are better than most at not picking up stuff in the first place).

I never like talking about rim wear in terms of miles cycled.  There's far too much variation in how much and how hard brakes are used per mile, let alone variations in conditions, for mean averages to mean anything.

[andygates]

A fingertip depth is *my* sign.

The one time I ignored it, I had a rim failure in the wildy wilds, after a couple of days of... weird handling.

+1 to clean the pads.  I pop the brakes open and dig out the worst swarf with a knife.  It's amazing what they pick up.