A23 OCR rim and unsealed roads

[njh...@gmail.com]

The A23 offset rear rim on one of my bikes is pretty much shot after a ride on Friday that included about 20km of unsealed road. Most of the gravel was in pretty good condition - just a few washaways here and there, but the rim, which was perfectly true when I cleaned the bike before the ride, was substantially out of true when I got back onto the bitumen. I had to use my Spoke key to tweak a few of the nipples to get the wobble down to the point where the rim was clearing the brake blocks as it rotated.

I didn't hit anything hard enough to pinch flat the tyre and wouldn't have expected this amount of damage, given that I've been riding this wheel for about 18 months, over a mixture of roads, without problem. I only weigh 65kg and was just carrying the normal spare tubes, tyre, levers, multitool plus spoke key, and a couple of sandwiches for lunch. If you look at the enlarged version of the attached photo, there's quite a substantial bulge at the nipple in the centre of the photo, and this bulge was duplicated at several other points around the rim.

I have a spare A23 offset rim. I'll use that to replace this rim, but I'll also use Sapim elliptical washers under the nipples in the hope that the washers will spread the load a bit.

Nick

[Andrew]

Any idea what your spoke tension was/is?

[kurt...@yahoo.ca]

Nick,

That's disappointing. I was just about to pull the trigger on a set of the non-offset rims. Now I'm wondering if other people have had similar issues. Just out of curiosity, were you using butted spokes?

Cheers,

Kurt G. in the Kootenays

[Scott Stulken]

Is that a crack below the lowest spoke, or just something in the reflection?

- Scott

[satanas]

Re the "elliptical washers" mentioned: are these just flat washers, as used for relatively ancient rims (<1980s) sans eyelets? Thanks.

[njh...@gmail.com]

Spoke tension: ~120Kgf drive side.

Spokes were Sapim Race - 2/1.8/2 swaged.

It's not a crack below the lowest nipple, just a mark on the surface of the rim. I went over the rim quite carefully, and couldn't find any cracks at all, just these bulges.

The nipple washers aren't flat, they're oval and curved across the minor axis. DT make very similar washers - quite a lot of their MTB rims are provided with these washers and they specify that they should be used when building the rims:

Nick

[Jeffrey Arita]

Two (2) additional data points from our experience regarding OFF-SET rims:

Two different bicycles built up with Velocity Synergy OFF-SET rims (both 32 hole).  Both for rear wheels, both built by a well-known wheelbuilder.  Went on the TransAmerica Route, starting in Astoria, OR.  Somewhere in Idaho we noticed that cracks developed at the spoke holes for both rear wheels.  Contrary to popular opinion, the TransAm does have some dirt road options which we rode loaded, so it might have been the primary cause.  I will be the first to state that riding 32 hole wheels on the back is probably not a good idea touring across the US loaded.  I took responsibility for the issue and simply paid for 2 new rear wheels.  We made it as far as Missoula, MT (ACA's HQ) before replacing both rear wheels (Velocity 36 spoke wheels) and proceeding on (with zero incidents BTW from Montana to Virginia).

I have zero intention to knock the wheelbuilder - simply to state that both wheels were assuredly assembled and tensioned appropriately - not by an inexperienced person.  My gut tells me (although I don't have any direct evidence) that a contributing factor could be the off-set nature and design of the rims.  I have personally assembled 10 wheels now, 8 of which with Velocity NON-OFFSET rims and all are fine (so far).  The other two wheels were built with non-Velocity (NON-OFFSET) branded rims.

Good luck,

Jeff 

On Sunday, March 11, 2018 at 11:07:01 PM UTC-7, njh...@gmail.com wrote:

[Steve Palincsar]

Velocity Synergy 650B offset rims had a known cracking problem.  They all did it, nothing to do with the wheel builder, and nothing to do with the holes being offset either: I have an offset Velocity Aeroheat rim that's in fine shape and over 15 years old, while several of my 650B Synergy rims cracked in a couple of years.

-- 
Steve Palincsar
Alexandria, Virginia 
USA

[Stephen Poole]

One should be a bit careful if extrapolating. Both Campagnolo and Shimano have used offset rims on various wheels, as has Ritchey.

FWIW, I have a pair of Velomax wheels with a rebranded v1 24° Velicity Aerohead on the rear (basically a narrower A23). When I bought the wheels used there was a small dent in the rear rim, which I repaired. The wheels have stayed straight, zero issues.

Later,

Stephen

[Steve Chan]

   Is this a problem with the rim being offset, or a problem with a lightweight rim (A23) and a relatively skinny (for 650B) tire (32mm) on gravel for that distance? For the width and depth, the A23 is a very light rim isn't it? Maybe it needs a fatter tire to be taken on longer gravel sections?

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[Jeff Bertolet]

The bulging is very common on Velocity rims. It does not necessarily presage failure.

It is a sign of plastic deformation of the rim under tension. It can last a long time in this state, but I don’t like it.

I have seen lightweight velocity rims last a long time. OTOH, I don’t think they are very stiff for their weight. With similar spokes and hubs, I think HED Belgium and DT Swiss rims build stiffer wheels, and are faster the build as well. Some Velocity rims build like a wet noodle, not fun.

Maybe a pro wheelbuilder will chime in, but I avoid Velocity if there is a viable alternative. I am currently using Pacenti SL23s and Brevet rims. The Brevet rims are not particularly stiff, but they are ok so far (very low mileage).

[Stephen Poole]

Stiffness is emphatically NOT the same as strength. Most strength comes from the spokes, and the build. Yes, there are some weak rims about, but not stiff doesn't necessarily mean weak.

For instance, a guy I know used to keep an unlaced Open Pro there as a tool to sell other rims. You could visibly deflect the Open Pro radially much more than say a Deep V, however I have a front 28° Open 4 CD from 1989 which is still going strong. Stiffer radially => harder ride; stiffer laterally can help if there are minimal spokes or for serious offroad abuse (I suppose). In practice I find well-made rims of shallow depth hold up fine if the spokes, build and use are appropriate.

DT rims have tended to be very round and straight, but I found their 700c offerings difficult to fit and remove tyres from (unlike Mavic & Velocity), though perhaps not quite as bad as Campag.

Many of Velocity's rims build up and hold up very well, though some people do seem to have had problems with their 650b rims. Some Pacenti rims have cracked too, but not mine - yet.

Later,

Stephen

[Eric Nichols]

I've run the A23OC rims for years, in 650b and 700c variants.  Thousands of miles on mixed-terrain rides, including a large proportion of "underbiking" over rough terrain.  I weigh 90+ kg.  These rims have been very reliable and I have not experienced any of the bulging that is evident in the OP's photo.  

To my eye, it looks like the spoke tension is too high. 120 kgf is pushing it. I'd aim for 100-110 kgf and check your tension gauge. I recently discovered my Park gauge was reading almost 20% high -- see discussion over on the iBOB list (https://groups.google.com/d/msg/internet-bob/8wjPDhBMS9E/u9VVjsNgAQAJ) 

BTW I've used those Sapim nipple washers on other rims, but they aren't really needed on the A23. 

Eric