I've got 16,000 miles on a pair of Alex Adventurer rims, and I'd rather not ride to failure. I have rim brakes and a pretty heavy bike. On the other hand, money is tight. What should I be looking for to know when it's time to change them out? Thanks.

There is this: SAFETY - Check Your Rims for Wear - Bike Test Reviews

You are probably good for 5-10k miles more, unless you ride a lot in wet/dirt etc. I do recall some
cracks appearing in the braking area on a set of rims decades ago. This is usually the first sign,
an area of cracking just below the level of the tire ledge inside the rim.

First of all rim wear isn't related to miles. It's only related to braking. So you could do 50,000 miles or more of open road riding, yet wear through a rim in less than 10,000 miles of urban commuting. Add rain and sandy roads, or both, and wear life goes down still more.

If your riding profile justifies worrying, start by looking for scoring of the kind that can happen if a stone is lodged in a brake shoe. Some people also place a straightedge again the rim and replace if it's concave by more than 1.5mm or so.

OTOH you can simply be attuned to the signs of impending failure. Most times the rim will flex outward long before it starts to crack, or there may be the beginnings of cracks over a short span. Both of these will cause pulsed uneven braking, so IMO you can wait for that, and deal with it then.

Good article. Thanks.

The pavement rushing up to meet your face.

Sorry couldn't help my self.

Keep a close eye on the brake track, put a straight edge on it and check to see how concave it is. It's probably pretty close to retirement. Google 'worn rims', and look at the images.

Is there a shop that sell used bikes near you? They may have some better wheels you could buy

By the straightedge test (less than 1mm cup), I'm good for a few thousand more. Thanks.

Tire size and pressure both play into this. Increasing either will increase the forces prying the rims apart.

This is one of those things where you really want to be pro-active. It is not pretty when a rim blows apart. I have seen cut carbon fiber and a cut needing stitches on a calf.

Ben

Brake track-sidewall of rim thinning... there is often a wear indicator in them these days. when its gone you should get a replacement .

i just checked two different styles of rims... one was 1.7mm thick at the bead seat, the other was 1.87mm thick at the bead seat... both are in new condition, with no wear...
depending on how the brake pads were aligned on your bike, you may be riding on .020" of material or less...!!!!! that's 1/2 mm, btw...

there are no proven, set in stone, rules for rim wear.... when the rim's outer lip separates from the rest of the rim, the tube will most likely blow out suddenly.... ouch! you may get a warning in the form of an odd pulsing in the brakes on that rim.... it will fail while cornering, most likely.... or while under hard braking...

i've caught more than a few worn rims before they failed completely... the owners bring the bikes in for wheel truings usually... the rims get weak before failure.

In my experience with three rims, there comes a time when a faint "thumping" is apparent when braking. This comes once per wheel revolution, at least initially. Inspection at this point reveals a part of the rim that is bulging farther out of the plane of the brake track and there is a crack running circumferentially somewhere on the braking surface. There is at least a millimeter of "dishing" on the braking surface when measured with a straightedge. This is the time to plan a replacement rim very soon because the crack can propagate rapidly. Tire pressure pushes the rim's edges outward and they are pressed inwards with every pass through the brake shoes. Aluminum does not tolerate this back-and-forth movement very well, and the rest of the rim is already thinner than when it was new.

Here's a general question. In *my* case, the rim failures have all been on the rear wheel of my folding bike. The rims are 406 BSD and somewhat narrow (18-20mm). Both front and rear tires are the same size and carry the same pressure. I use both brakes, and especially the front, yet it is the rear rim that wears out. I'd say "wears out first" except I've never worn out a front rim.

I have rim brakes on a mountain bike and a road bike, and after thousands of miles these rims are virtually un-worn. It's only the smaller rims that wear, and only the back ones.

My hypothesis is that the front tire kicks up abrasive dust which lands on the rear braking surface. This seemed especially likely on my "winter" bike, which would wear out rims in a couple thousand miles. I fitted a roller brake module on the Nexus 8 hub on that bike and have had no problems since.

I've gotten quite good at re-building these wheels, but I'd like to skip the experience. Any thoughts?
Steve