niliraga 

Picked up some black TB14 rims today, mainly because they were going cheap enough for me to act impulsively.

They seem ok, from what I can determine - turns out it's trickier to tell when you dont have a hub to spin them around! they seem flat and round and show no real signs of abuse. But the brake surfaces have seen some miles - they look like any other well-worn braking surface, but with a "concaveness" that you can definitely feel with a fingertip even if you can't really see it.

Part of the appeal is that TB14s could be an easy swap for MA40s on a wheelset where the rims are tatty but everything else is good - ideally, this could be as simple as the swap RiddleOfSteel showed us a year ago. I'm not looking for miracles, just a decent (wider) set of rims that could handle at least another 2000-3000 miles of easy touring

So my concern/question is - does a concave brake surface mean these are too far gone to invest that kind of effort? should i save my pennies for a new set, 'cos they're awesome, or are TB14s engineered so beefily that I should just press on regardless with these survivors?

repechage

measure, they way you need to do it is with a micrometer, you have to get around the thicker portion.
I do not know the start dimension of the rims, should be reference-able.
I do not think the rims are especially light or heavy. I want to recall 450grams ? for a box section rim, not bad.

Dylansbob 

Theyr'e a new enough of rim there should be a wear indicator on the braking surface. I'd use that as a guidline.

tricky 

Hold a flat edge against the braking surface, shine a light behind it and post a pic here.

Ferrouscious 

TB14s are 490g each. pretty meaty

niliraga 

great idea!

Dylansbob 

Woof, that's alot of wear.

I've got an old Cane Creek WAM front wheel that looks like that. It lives on a brakeless fixed gear.

I wouldn't put in the effort to build to those.

Fahrenheit531 

cyccommute 

You might as well wrap a turkey in that. It’s about the thickness of aluminum foil now.

Non wise ass answer: Time for a new rim. Ya got your money’s worth.

repechage

I would not buy another set so worn.
As said earlier, impressive wear.

I would keep them around to stretch Kevlar bead tires with. Actually I am intending to make a rim into just that, cut a section out and add parts to turn a rim into a bead stretcher.
the Kevlar beads always stretch out a bit and later installs are much easier but the first install is always much effort.

niliraga 

well, that'll learn me!! thank you all for the collective wisdom - sounds like they are good for wheelbuilding practice but should never see another brake pad.

well, seller must have known they were far gone - at least they came at a "fully disposable" price.

more generally for rims, if/when i work out how to get past the hook and measure actual wall thickness, what is the thickness most of you would consider the limit? much as how chain stretch sets yellow flags at 0.5 and red at 0.75%, is there an equivalent here?

niliraga 

so remove a section to allow rim diameter to shrink for installation - then how to stretch back out? some sort of threaded bolt expander across the cut faces?

cyccommute 

I suspect there is a value for wall thickness out there but I don’t know what it is. I doubt few people actually measure their rim’s wall thickness. Most people are going to go by a visual inspection and checking to see if the wall is concave. I would pitch a rim long before your example.

The concavity of the rim may not be just wear related. When you pressurize the tire, the force of the air pushes out on the wall of the rim. As you thin the rim through braking, the pressure can bend the wall outward. Get the wall too thin and it will fracture. I got to witness this is real time at my co-op when an obstinate customer ignored our advice that his rims were very concave...not even as much as yours. We could see the wall flex as he pressurized the tires and told him it was going to fail. We thought that it would fail down the road but about 15 minutes later we had a blowout with a nice ring of aluminum from where the wall had fractured.

Fahrenheit531 

For future reference, modern rims will typically have a little "divot" in them. When the wear reaches a point that the divot is no longer visible, they're toast.



Tires will often have them too.

niliraga 

i have some Mavic Open Sports with a wear indicator "ring" machined into the walls, and have seen plenty of generic rims with similar, but I am curious to know if rims that seem to be aiming for retro looks (TB14s, many from VO etc.) put some other kind of indicator that doesnt detract from the look.

tricky 

I would guess that min thickness is going to be different for different rims. They use different alloys, especially if you are talking vintage vs modern rims. Maybe manufacturers publish something like that. If you are looking for a way to measure thickness, you can get caliper attachments that allow you to get around varying thicknesses. https://www.mcmaster.com/caliper-attachments/ Probably not advised for super accurate measurements, but would be fine here.

Fahrenheit531 

TB-14:



And by no means does it "detract from the look."

niliraga 

nice! i guess no point looking for that on the beaters I have here...

tricky 

Thanks for the pic! I couldn't find anything on the H+Son site mentioning wear indicators.

Fahrenheit531 

They're superb rims. If you're on the fence, just go ahead and click 'buy'.

repechage

think turnbuckle in reverse.
Yes, requires some fabrication

aland2

They're worn out but lots of people ride them like that. Be careful. Move your brake blocks for starters so they bear on the unworn surface.

bark_eater 

Just to for trivia points, there are 90's era Araya rims that start off concave. Before I got comfortable working on my own wheels, I took a set in to replace a spoke and true the set up. The guy wanted to sell me a new set because these where wore out. I insisted, and the work got done, but I think I had a PIA sur charge added.

JohnDThompson 

A dental caliper is an inexpensive tool to measure rim wear. Usually can be had for about US$5. The problem is, you have to know how much wear is too much wear.

steelbikeguy

the issue of rim wear gets discussed every so often.
About a year ago, someone presented a way to make a little tool out of an old spoke to permit measuring the rim thickness with an ordinary caliper. I had a Sun CR18 that was getting pretty worn, so I went through the process....

the tool itself.



the thickness of the tool itself, which is needed for a later step.



The tool placed to permit indirect measurement of rim thickness.


measuring the combined thickness of the rim sidewall and tool



of course, the alternative is to make a direct measurement of the rim wall thickness. Not a great option if you might want to use the rim, though.
I replaced this unmachined CR18 with a new machined CR18. The new CR18 had thinner side walls than this worn out CR18.



Steve in Peoria