Jobst Brandt blames hard anodising (it's too brittle, and cracks can propagate into the rim alloy) for most cases of rim cracking, but your rims don't look hard anodised. Probably just excessive spoke tension and age.
Yes I have just read that bit in The Good Book. The rim was a Mavic T221. I have just had a little surf and cannot find any details so I do not know if it was anodised. I still have the rim leaning against the dustbin, is there any way I can tell if it was anodised?
I still doubt that the spokes where too tight. Anyway I have now built a new wheel on the old hub using new spokes. The new rim is a DRC one and I have the set the spoke tension higher than it was for the Mavic rim - in setting the spoke tension on the new rim I realised how low the tension was on the old rim.
John T.
PS. My Conti 2000 tyres are very tight in the new DRC rim :-(
FWIW, a wheel with very tight spokes is no stronger than a wheel with adequately tight spokes. The limit is where the spokes cannot become loose (and potentially unscrew their nipples) at the bottom of the wheel. When you have got this far there is no point in having the spokes any tighter - it just increases the risk of cracking and "pringles".
Um...so that means that a wheel with tighter spokes can handle a larger load and is therefore stronger, other things being equal. There is no point at which "spokes cannnot become loose" as there is no obvious upper bound on the loading that a wheel can experience (other than the load which will cause a collapse!). Of course pull-through is one of the potential problems that puts an upper bound on the sensible spoke tension.
I have just had a little surf and cannot find any details so I do not know if it was anodised. I still have the rim leaning against the dustbin, is there any way I can tell if it was anodised?
Rub with metal polish. Deep black mark on cloth means it's not anodised (nor coated in any way). However, *soft* anodising isn't really a problem. It's *hard* anodising (CD) that makes rims much more prone to cracking. From the picture, your T221 rim dooesn't look like a CD version.
Quoted message said:
I still doubt that the spokes where too tight.
They may not have been too tight for a good wheel, but I still suspect at one time they were probably too tight for that particulat rim in its particular condition. I don't see how INsufficient tension can be to blame. You can't have spoke pull-though where there's no spoke, and lack of spoke is the ultimate in insufficient tension.
Jobst Brandt blames hard anodising (it's too brittle, and cracks can propagate into the rim alloy) for most cases of rim cracking, but your rims don't look hard anodised. Probably just excessive spoke tension and age.
Yes I have just read that bit in The Good Book. The rim was a Mavic T221. I have just had a little surf and cannot find any details so I do not know if it was anodised. I still have the rim leaning against the dustbin, is there any way I can tell if it was anodised?
The other bit he talks about is whether the spoke holes have steel eyelets in them to distribute the loads and notes that aluminium rims without them often crack around the spoke holes.
On Mon, 27 Dec 2004 11:58:14 +0000 (UTC), John Tomlinson <[email hidden]> wrote in message <[email hidden]>:
Quoted message said:
The rim was a Mavic T221. I have just had a little surf and cannot find any details so I do not know if it was anodised.
Mine were anodised and fitted with stainless eyelets. I don't think they would have changed either of these features without changing model number, but ICBW.
Guy -- "then came ye chavves, theyre cartes girded wyth candels blue, and theyre beastes wyth straynge horn-lyke thyngs onn theyre arses that theyre fartes be herde from myles around." Chaucer, the Sheppey Tales
