Tomm Willians

Attached is a pic of the braking surface on a set of Mavic GEL 280 36 spokes mounted on my vintage Wilier. Both front and back wheels show this characteristic where they seem slightly dished and it seems to take place consistently between the spokes. Can they be trued? Time to replace ?

cxwrench

'Truing' won't fix that. It's totally normal on those light rims.

Kimmo 

If you can't decide to like the look of it (I've always thought it looks pretty cool}, you could hit the brake tracks with an orbital sander or something and remove the anodising altogether.

Bare aluminium is significantly grippier than that old school hardox surface, particularly in the wet, but it'll wear significantly faster too. The hardox is great protection against the awful galling you get when a little bit of grit stuck in the brake pad snowballs into a chunk of aluminium.

Tomm Willians

Actually I do find it kind of attractive, I was just hoping it didn’t mean my wheels were at their expiration date.

aggiegrads

It looks like the rim has a wear indicator in the center of the track. If that is still visible, you should still have some life left.

Pop N Wood

So how does one measure the thickness of an old rim like that to know for sure?

I can't see the wear indicator in that picture.

Atlas Shrugged

This is a perfect way to destroy a set of wheels and brake pads! Your rim will have traces of abrasive embedded in it post sanding which will embed itself into the brake pads destroying any future rims they will be used on as well.

sweeks

It's the black line running circumferentially at the middle of the brake track. When the rim around the line has worn away, there's usually less than a millimeter of metal remaining.
Another way to evaluate rim wear is to place a straight edge across the brake track in a "radial" orientation. A pronounced depression in the center of the track is suggestive of wear approaching the need for replacement.
If your rim produces a "thumping" sound or feeling when the brake is applied, it's time to get a new rim.

EDIT: See THIS.

cxwrench

There was absolutely NOT a rim wear groove on these rims. It was still years away when these were current. These rims don't have that much wear yet...they're not bad at all.

Shimagnolo

The best way I've found to clean up a brake track is a Scotch-Brite pad (or generic equivalent).
Much easer to do with the tire off, so you can wrap the pad around the rim and clean both brake tracks simultaneously.

sweeks

The rim wear indicator is a feature of the rim. It is not the result of wear. See THIS.

cxwrench

There. Was. No. Rim. Wear. Indicator. On the 280/330 rims. Trust me on this, I've built dozens of sets. This is not my first rodeo as they say.

sweeks

I defer to your greater expertise.

cxwrench

Thanks. If you don't know for sure, do a little research...there are hundreds of photos online of those rims. The 280/330/SSC rims were made looooooong before indicator grooves or dots were a thing. Like decades before.

ThermionicScott 

I'd be hesitant to remove any material on these rims if I didn't absolutely need to. They started out only 0.8mm thick.

Pop N Wood

I would never take a power sander to a set of rims, but I have cleaned them with scotchbrite pad like someone mentioned.

I do use a sander on brake rotors when they get badly glazed, both bike and auto. But I always use a garnet sand paper meant for wood. No metal oxides to work into the metal that way.

Pop N Wood

Thank you. Good info

As for the "thumping" sound, I've had that happen on both bikes and automobiles when an uneven layer of pad material is deposited on the rotor/rim. This is why lots of people advocate "bedding" new brake pads, to get an even layer giving a braking surface with uniform grab.

I've fixed this on bike rims by cleaning the rim with a scotchbrite and some solvent. With car rotors the deposits are usually very visible. I've cleaned them with some success with a sander and garnet sand paper, but anymore now I have better luck replacing the rotor.

cyccommute 

There is clearly a wear indicator on that rim.

The black line, indicated by the red arrows

cxwrench

No. That is not a wear indicator. As I've posted a few times wear indicators were not a thing when these rims were made. That groove, like all the others on this rim, is from wear, not manufactured. Stop posting incorrect information and do some research. Find a photo of a 280 or 330 rim with proof of a wear indicator. It's black because it has pad material in it. If it was a manufactured groove it would be thinner where the eyelets are and deeper between the spokes, following the rim wear. But...wait for it...it's the opposite. These rims are thin enough that they 'oil can' as they wear. That's to say they wear more where the eyelets are and slower between them. It's easily seen on many photos. Take a look at some photos and get back to me.

cyccommute 

No, that line in not from “wear”. It is too uniform to be made by any wear mechanism. Something imbedded in the pad would make a groove that is varies more. Look at the wear mark on the rim right above the second arrow. It is small and of variable depth and width. The black groove is even and follows the rim arc exactly. Perhaps Tomm Williams is mistaken about the rim model. The one in the picture has a definite wear indicator groove in it.

The line is black because it was anodized. And why would it be thinner or deeper? The groove is machined into the rim and they don’t vary the depth or thickness. A uniform groove is much easier to machine than one that varies. The groove looks like the ones in this chart. And, if the groove were a wear groove it should vary in depth and width as you’ve described. A uniform groove won’t form from braking.

To quote someone “this is not my first rodeo”,

cxwrench

Have you looked at any photos of these rims? I'm telling you that these rims NEVER had a wear indicator groove. I've built many wheels with them. Find a groove in these rims...you'll find the exact same rim surface on the 330.
ETA: You can't have a groove machined in these rims because Mavic hadn't even started machining the brake track yet. The rims were extruded, pin and glued and that was it. No welding, no machined brake track, no wear indicator.

cyccommute 

Yes, I have looked at the rims in question and I agree that they don’t have wear indicators. But I have also looked at Tomm Williams‘ picture and there is clearly a wear indicator groove on them.There are gouges from braking as I’ve pointed out but no wear pattern would result in a groove that is uniform in size and shape across a large arc of the wheel. It covers at least 5 spokes in the picture with an even size and evenly spaced from the outside and inside of the rim. That’s about a 30cm arc of the wheel to cover.

Additionally, the rims that Tomm Williams shows have clearly been milled. The transition from the spoke bed to the sidewall in the pictures you show are gentle curves while Tomm Williams’ rims have a very sharp transition that is typical of milled sidewalls.

The rims are obviously not the model of rim that Tomm Williams thinks they are.

mrrabbit 

Mavic GEL series from the 80s and 90s do not have wear indicators.

What's really shocking about the OP photos is that it doesn't appear super light double butted spokes were used.

They appear to be straight 14g or straight 15g.

Normally these would be built with something like 2.0/1.5/2.0 on the front and 2.0 / 1.65 / 2.0 on the rear.

Ugh!

=8-(

easyupbug 

OP, to your questions I had a set and early in their life at each spoke the anodizing wore off first, kind of leaving aluminum bare spots around the rim which could lead you to believe the rims were dished between spokes; I suspect due to deformation from the spoke tension it was the opposite, the rims flared out at the spokes. I also think that is an ugly grove but not a wear indicator and you likely have good good miles ahead.

Oh, and you can measure rim thickness in various spots if it bothers you.

cyccommute 

While I disagree with cxwrench...and with you...about the model of the rim, I do agree with him that what you are seeing is “oil canning”. The eyelets area is resists bending while between the eyelets is somewhat softer. The rim bends slightly as the brake slides over the spaces between the eyelets then flares out again. The result is a slight pulsation of the brakes that you likely won’t feel but it results in an odd wear pattern. There’s nothing really wrong with it. Check the rims occasionally for straight walls by putting a straight edge on them. If they cup, replace them. Otherwise just ride.