|Rim aging causing excess flex and broken spokes||mhester|
Dec 3, 2002 5:28 PM
|LBS guy tells my neighbor that the reason his spokes keep coming loose (and breaking) from his Matrix Aurora rims is that though the rims don't have that many miles on them, they are old, and they oxidize and get weak as they age and then flex too much causing the loose spokes. (So buy new rims) He further says that riding rims regularly will make them last longer than rims that just sit around unused. Said that the LBS would be purging some of their unsold rim stock because of this phenomenon. (Fact or Fiction?)
Neighbor didn't use spoke prep when built up the wheels. Would that stop or at least reduce the spoke loosening (and subsequent breaking). Neighbor needs most economical solution.
|Economical solution = new LBS||Kerry|
Dec 3, 2002 5:58 PM
|I suppose that rims that have oxidized so badly that they are thinning seriously could be weakened. But then, the spokes would pull through and the pressure from the tires would cause the side walls to fail. No the problem here is a bike shop that is totally full of it. All this guy needs is to have his wheels retensioned. The reason that the spokes keep coming loose is that they don't have enough tension to keep from going slack with each revolution. Perhaps the wheels are old enough that the spoke nipples have oxidized and are making the wheel hard to true, but this is fixed by either replacing spokes (high cost) or by un-threading each nipple, greasing the threads, and rebuilding the wheel. I'm guessing the LBS wants to just sell a new wheel.|
|Economical solution = new LBS||mhester|
Dec 3, 2002 6:39 PM
|Thanks Kerry. What he originally thought was maybe that the greaseon the spoke threads was causing the spokes to loosen. What do you think about the spoke prep stuff (or Loctite)?|
Dec 4, 2002 1:59 PM
|First the LBS guy is full of sh!te. That stuff about aluminum aging just sitting around is a bunch of crap - if it were true we shouldn't even be thinking about flying on commercial aircraft - they're all aluminum. We should throw away all sorts of stuff. Actually the little bit of surface corrosion on aluminum is a good thing - it prevents further corrosion, within reason. If you're in a marine environment things are a little extreme and electrolosis can really raise hell which is why boats use zincs. In fact anodization is just a controlled form of surface corrosion used to preserve aluminum. |
The reall issue is that first an foremost the Matrix stuff is garbage - it was the company that Trek took over and equiped virtually all of their bikes with. I had some of their wheels and the damn things wouldn't stay true. Pretty low end crap. The next issue is that the wheels were typically machine built and the spoke tension was typically quite high - way too high in fact. So take a cruddy rim, build it with a machine and set the spoke tension too high and one could reasonably predict that you might have a problem with nipples pulling through the rim. Now if the rim were nice and strong you should see failures somewhere else. Perhaps the spoke or the hub flange.
Where does this leave your friend? Well, his rim isn't going to fix itself or get any better. His LBS is suspect, at least the guy that works there. What he really needs is some new wheels - rebuilt or otherwise. Smart money says to spend the time and find a skilled wheel builder to rebuild his wheels or score a deal on a set of quality pre-built wheels. With a little bit of time and patience one can learn to build wheels yourself, but you won't really save any money once you set yourself up with tools and spend the time learning. Still it is a valuable skill to have and it's not rocket science.
Word of advice. Grease belongs between the nipple and the spoke hole/eyelet while the old standard has been to use linseed oil on the threads of the spoke and nipple since it gums up over time and acts sort of like Loctite. Read all about it in one of the several good books out, my favorite is The Bicycle Wheel, by Jobst Brandt - it's a classic and debunks a lot of the crap that gets slung around about wheels. Even if you never build a single wheel you'll be much more informed when you buy your next pair. It's $20 well spent.
|Your LBS emphasizes the BS. nm||Uncle Tim|
Dec 3, 2002 8:44 PM
|re: Rim aging causing excess flex and broken spokes||pa rider|
Dec 4, 2002 3:49 AM
|I would have to agree with Kerry. We have one lbs(Jay from pedal pusher) here who would just relace the wheels again using the existing spokes. If your neighbor had a lot of miles on the spokes than maybe replacing them would hurt.
I break a lot of spokes, but the guy who builds my wheels now says proper tension evenly on the whole wheel is the reason your spokes are coming loose.
I would tight my loose spokes and another spoke in a different place on the wheel would come loose on the next ride. It cost me $20 to have the wheel relaced.
The LBS wants to sell you a new rim because he must not be good at dishing wheels and a new rim being relace would be easier on his part. My lbs jay would try saving the customer money by relacing your old wheel first. His opinion is that some parts don't necessary need replace all the time. A good wheel builder can fix a wheel by relacing the spokes to proper tension evenly.
I had him relace a wheel for me after I crashed. He said the rim was egged, so he then told me to buy a new rim. He did this after he tried to trueing the wheel again. At least he tried to see if the old rim could be saved.
If your neighbors bike just been sitting in a garage and wasn't used much, then get another lbs to relace it for him.
Everytime I buy a new bike and start breaking spokes I have jay relace the wheels for me. Machine build wheel will never get wheels to quality as a hand built wheel.
Just my 2 cents.
|that's a new one on me.||jw25|
Dec 4, 2002 5:59 AM
|Rims are just aluminum alloy extrusions - they don't age significantly, nor do they flex more as they age. Even wear from braking, up to the point of rim failure, won't affect the stiffness noticeably.
If stored properly (and aluminum's pretty tolerant), in something other than a salt-water environment, rims should last indefinitely. Heck, I built up some MA-40's that are at least 10 years old, and they ride just fine.
The solution to those loosening and breaking spokes would be loosening all spokes about 4-5 turns, to detension the wheel, and then retensioning properly. It just sounds like the spoke tension's not high enough.
Loosening spokes before retensioning them helps get tension even. Work slowly, to keep tensions similar, and get them tight - I work by tone, but feel, while subjective, is also good.
Jobst Brand recommends adding tension (to a true, round wheel) in quarter-turn increments, stress-relieving after each round.
When the wheel becomes noteicable out of true after stress-relief, back each nipple off half a turn, retrue if necessary, and that's optimal tension.
Note that newer spokes, hubs, and rims may not give this warning, so I prefer to use tone. Pluck spokes on a built, reliable wheel, and use that as a general guideline.
And, find a new LBS, or at least stop asking that guy for advice.
|Examine your rims.||Spoke Wrench|
Dec 4, 2002 10:32 AM
|I'd recommend carefully examining Matrix rims at the spoke holes. What you are looking for is cracks like a spider webb. Your LBS may have the wrong reason but the right answer.|
|more on old rims and broken spokes||maximum15|
Dec 5, 2002 9:23 AM
|I just bought an '88 Bianchi that had been in the owners garage unused since 1990. Both the front and back wheels had about half the spokes broken. The front wheel wasn't even on the bike but a replacement wheel was. The replacement wheel (a cheapie) had no broken spokes. The gentlemen who sold me the bike said this was well known. I just looked at him stupid and left with the bike -- didn't make and sense to me. For what it's worth, the spokes were all broken very near their midpoint. So I have seen this but don't know of a valid mechanical engineering reason for it to happen.|
|Spokes breaking in the middle||Kerry|
Dec 5, 2002 4:51 PM
|Three possible explanations for spokes that break in the middle: defective manufacture (grain boundaries due to poor metal, heat treatment, etc.), mechanical damage to the spokes creating stress risers, corrosion. The 12 years in the garage scenario suggests corrosion.|
|Spokes breaking in the middle||maximum15|
Dec 6, 2002 3:37 AM
|Probably right on corrosion since storage was in Florida and near the west coast (Gulf). Should have saved the spokes and looked at them with a metallurgical microscope or SEM just for the fun of it.|| |