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Are There Concave Rim Walls or is this Wear?

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Are There Concave Rim Walls or is this Wear?

Old 07-29-21, 10:46 AM
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Harold74
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Are There Concave Rim Walls or is this Wear?

This question concerns the original, Araya rims on a 1992 Miyata 1000. I can't manage a picture to really show it but, if you run your finger over the rim walls on the outside, those walls are discernably concave (innie). I'm wondering whether:

a) This indicates rim wear. To be honest, until joining this forum recently, I didn't even know that this was a thing that could actually reduce a rim to a consumable. I'm a dry climate rider.

b) Alternately, would some rims actually have been made this way originally? It's difficult for me to measure the remaining wall thickness with any accuracy.

Additional information that may or may not be useful:

1) The brake pads have been replaced at least once.

2) The tires have been replaced at least once.

3) I believe the cassette to be original and, as best I can tell, showing no discernable signs of wear. I've got one of those Rohloff things for what that's worth.

4) The original owner told me that the bike went for one, massive tour in South America and sat in a garage after that. I've come to question the truthiness of that claim though.

5) The concave nature of the rim walls is apparent, in equal measure, on both the front and back wheels.

Lastly, anybody want to hazard a guess at what a rim like this weighs? I have an opportunity to buy some 10 speed, Bontrager SSR wheels at a good price that would fit the bike and allow me to complete the transition to 9-speed which is already well under way. The SSR's are heavy too and probably don't have enough spokes for serious touring (not a problem as I don't tour). This wear question will factor into my decision though. I do love the Deore hubs on the original rims and would be sad to see them go.





Last edited by Harold74; 07-29-21 at 11:03 AM.
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Old 07-29-21, 10:54 AM
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Yes concave rims were a thing, I have a 1992 Kona which has one original rim, and Araya RM-17 which is concave, and that is how they came.

It's a bit disconcerting if you don't know, and I don't think anyone else has done this since (for good reason, as it looks worn out when new) Would be interested if anyone else did, does any one know?
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Old 07-29-21, 11:01 AM
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I've never had a concave rim AFAIK (pretty much have been confined to 26" and they may not have been made in that size). I have "worn out" many rims in this dry socal climate. The way it manifests itself in my experience is the wheel goes out of true and can't be straightened. Then it's time for a rebuild. I'd guess your rim at 500 grams and the spokes at 250.
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Old 07-29-21, 11:06 AM
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Thanks guys. It looks like the front wheel I'm considering (rim + spokes + hub) is about 990g.

It's great to know both that concave rims existed and that truing capacity is a good measure of wear. The rims that have true easily and hold it well.
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Old 07-29-21, 11:14 AM
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Originally Posted by Harold74 View Post
Thanks guys. It looks like the front wheel I'm considering (rim + spokes + hub) is about 990g.

It's great to know both that concave rims existed and that truing capacity is a good measure of wear. The rims that have true easily and hold it well.
If you can find the model number on the rims, that would clear up whether they are supposed to be concave or not. The idea was that the rims could work with multiple types of brakes and resist the pads' tendency to move toward the tire (centerpulls/calipers) or off the rim (cantis) as they wore.
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Old 07-29-21, 01:44 PM
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Originally Posted by ThermionicScott View Post
If you can find the model number on the rims, that would clear up whether they are supposed to be concave or not. The idea was that the rims could work with multiple types of brakes and resist the pads' tendency to move toward the tire (centerpulls/calipers) or off the rim (cantis) as they wore.
I'm seeing Araya 700c WO VX-300. Hopefully your GoogleFu is better than mine.
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Old 07-29-21, 01:52 PM
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Originally Posted by Harold74 View Post
I'm seeing Araya 700c WO VX-300. Hopefully your GoogleFu is better than mine.
Aha!

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Old 07-29-21, 02:04 PM
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Originally Posted by jimc101 View Post
Yes concave rims were a thing,
+1
I have a Campagnolo-branded rim from their brief flirt with MTB, and that one also has concave brake tracks.
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Old 07-29-21, 02:35 PM
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Originally Posted by ThermionicScott View Post
Aha!
Wow, this community is greeeat! Thanks so much.
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