Thump, thump, thumping Velocities.

[khjr]

I’m building up a new set of wheels using a Velocity A23 front and Velocity Synergy OC rear. I was pretty excited to find the A23s that I wanted with machined sidewalls in the finish and hole count I was looking for but, in the process, neglected to ask if the Synergy OC sidewalls would come machined as well. Alas, the vendor stocks and ships only un-machined Synergies, so that’s what’s on its way to me.

It’s been almost two decades since I had an un-machined rim. Are they any better now, or are they still prone to thumping across the joint when braking? I’ve been wondering if the problem won’t be as noticeable since the thumping would be on my back, vs. front wheel… Also, I've read a few postings to the effect that it's possible to fix a thumper by iteratively tweaking with a crescent wrench, but I've never tried it.

Thoughts? Send the Synergy back and get a machined one from somewhere else, or take the risk?

[vqdriver]

just curious why you didn't go with a23 front and rear.

[khjr]

just curious why you didn't go with a23 front and rear.

I'm converting an MTB hub to a narrower (fewer speeds) cassette and between some spacing tricks and the offset rim, am expecting to achieve ~97% equal tension between left and right. Not absolutely necessary to get that close to have a reasonably strong rear wheel, but I thought it would be fun to say that it was dishless. The Synergy OC is still pretty light relative to some other wide touring rims and, using 36 Wheelsmith 2.0/1.7/2.0 spokes 3X, I think that is should be pretty robust for this fat man to do credit card touring.

[false_Aest]

Thump thump thump on a velocipede is your feet yo.

[the ill postino]

I've built up a rear synergy o/c and am pretty sure the r/l tension was indeed pretty even. It was black rim, hence machined, though, so I can't comment on the thumping question. Some (Rivendell) would say (http://www.rivbike.com/article/components/rims) that non machined is a good thing, so maybe you lucked out!

On another note, take a look at the Rene Herse blog which has a new entry on the proper tension for the O/C rim here. (http://reneherse.blogspot.com/)

[khjr]

On another note, take a look at the Rene Herse blog which has a new entry on the proper tension for the O/C rim here. (http://reneherse.blogspot.com/)
Thanks for the link! No surprise to you that I actually bought the rims from Riv- they’re the only people that have silver A23s in stock right now. I thought about going with the black rims from someplace local but I’ve never owned black because it seems like it would show dirt more, and I take heed to Brandt’s remarks about embrittlement from the anodization

I have read a LOT of posts about cracking in OC rims, both here and on Bikelist.org. That said, Peter (Old Potato) from Vecchios says that he’s never seen it on the zillions of wheels he’s done, and Peter White claims it to be a non-issue.

Nonetheless, I am concerned about wasting my time on a crack prone rim so I’m trying to hedge my bets:
-36 holes
-Wheelsmith double butted spokes with narrower (1.7) cross section than DT for more flexibility
-Silver vs. brittle black anodization
-And lastly, totally even tension between left and right spokes, which can’t hurt…

[Peter P.]

I've built several wheels with Velocity Aerohead O/C rears and have not experienced cracking.

Regarding the thump at the rim joint: I've been able to successfully eliminate any problems by sanding the rim sidewall at the joint. Start with 150, then graduate to a 200 then 300 grit. When you're done, give it a few rides to smooth completely. You should have no problems then. Don't do the crescent wrench routine; I think it's fine for repairing an old rim but it breaks my heart to tweak a new rim.

[oldpotatoe]

Thanks for the link! No surprise to you that I actually bought the rims from Riv- they’re the only people that have silver A23s in stock right now. I thought about going with the black rims from someplace local but I’ve never owned black because it seems like it would show dirt more, and I take heed to Brandt’s remarks about embrittlement from the anodization

I have read a LOT of posts about cracking in OC rims, both here and on Bikelist.org. That said, Peter (Old Potato) from Vecchios says that he’s never seen it on the zillions of wheels he’s done, and Peter White claims it to be a non-issue.

Nonetheless, I am concerned about wasting my time on a crack prone rim so I’m trying to hedge my bets:
-36 holes
-Wheelsmith double butted spokes with narrower (1.7) cross section than DT for more flexibility
-Silver vs. brittle black anodization
-And lastly, totally even tension between left and right spokes, which can’t hurt…

Good choices, make sure the tension is proper on the RH side and the left will take care of itself. LH won't be the same as the RH tension, close but not the same.

Hard anodization is the ones that 'may' cause cracking, not the black, which is just a color.

I haven't seen the seam problems nor the cracking on Velocity rims and I have built many OC Velocity rims. Make sure the RH tension is proper. I shoot for 100 KGF, no more.

[keevon]

I have experience with a non-machined, silver anodized Aerohead rim. When it was new, I could feel the joint a little bit when braking. After a few months - and several rainy rides - the rim and joint wore down enough to be smooth.

[khjr]

I haven't seen the seam problems

Thanks again Peter.

Peter White is adamantly against non-machined sidewalls these days, but I don't know if he took that position before the Velocities came out or not.

Do you build you Synergy OCs with mostly machined sidewalls, or unmachined?