Continuos rear wheel grief
 

Hello all, im currently on tour from Alaska to Argentina and am now leaving Baja, the tour is going great and ive had so much good vibes all long the way.
Only problem is my rear wheel, snapped the first one after 200kms in alska and had it replaced with a sun ryhno which i was told is the best option for a fully loaded tour, It is spoked with 14gauge dt spokes on a solid Lx hub. I kept breaking spokes no matter how much stuff i got rid of it got so bad that i had it rebuilt in Bakerfeild and since then it was fine never coming out of true, i was well pleased however that counts for nothing now that it has split at the eyelts in several plAces one so bad that you could see where it has pulled it completely out.
Sunn has said they will warranty it but why has this happebned twice, im carrying about 40-50lbs on the back and am maybe 70 kilos myself, all the breakages are on the drive side.
Basically im getting into more remote territory and want a wheel to last the distance ill be having it buiklt soon as get to hermosillo and want any advice that can stop the same happening again
Cheers for your help in advanace

Call a good wheel builder like Peter White. Tell him the situation, and have him build you a wheel.

is this a 26 or 700c wheel? 36 spokes or more?

Rhyno is a good rim and normaly should give you good service. If the cracking is on the drive side the spokes may be over tensioned. because of the dish of the wheel the drive side has to carry more tension The spokes these days are so well machined and are strong enough that it isn't difficult to over tension them to the point where the rim fails before the spoke.

If you are getting a new rim from Sun at Hermosillo and assuming this is a 26" wheel you might consider a Sun Mammoth it weighs about 150 grams more and is about 2 mm wider. more importantly it is thicker around the spoke hole and should handle stress a little better. It also has the advantage of a smaller ERD which makes getting the tire off the rim much easier than the Rhyno. If you end up with a new hub also go for 40 holes if you can, You certainly should not be using IMO a 32 hole or less wheel.

some might reccomend using a 4 cross spoke lacing pattern, I would avoid that . Small flange rear hubs with 4 cross spokes tend to have problems because the first cross of the spoke is too close to the hub

Rick

I think some wheels jsut don't measure up for one reason or other that we can't identify. There is another thread where I talked about a wheel giving me grief from new.

I'd suggest a whole new wheel including hub. Maybe the hub flanges are out of whack. Who knows. I hae just gone to Velocity rims (with the Off Centre rim and Velocity hub and spokes on the rear) and have zero problems in around 6000km. They are 700C rims. I would not expect their 26" rims to be any different in quality.

Aleviate some of the problem by shifting 20 to 35 lbs of the load to the front wheel. This does help. Your rear wheel is the weakest of the set but takes the most punishment. By adding weight to the front you help remove some of that stress.

As for breaking rims, I do it all the time especially early on during my wheel building career or when I use factory wheels. It has more to do with uneven tension than with the rim or hub. Poor tension will let the spoke flex up and down slightly during each revolution. That flex is transmitted all along the spoke from hub to rim. Thousands of revolutions will result in the aluminum failing. As a spoke breaks at the head, it also relieves tension a the rim which further stresses the rim. The more broken spokes, the more localized stress on the rim.

Another problem may using straight gauge spokes. We all think that these are the best but there are arguments for using double butted spokes (http://www.sheldonbrown.com/wheelbuild.html#spokes). To summerized what Sheldon Brown says: The double butted spokes releive tension by being elastic. They can smoosh a little along their length and allow other spokes to take up the slack of the broken ones.

Another trick is to use more spokes. If you have 32 now (which you shouldn't) go to 36. If you have 36 go to 40 and, in extreme cases, go to 48. You could carry cars with a 48 spoker.