Micro cracks on mavic sprint rim. Advice please

[half cog]

Hi
Got a front mavic 24 hole sprint rim built on to a campy hub and there are some very very fine micro cracks at the spoke holes. Think thickness of a human hair if not less.About five holes are effected and they run along the length of the rim for up to 7mm. Nothing at all on the inside tyre bed.The rim has double eylets that go from the tyre bed right through. Anyone had this problem?If so did the wheel die quickly or run on for years. I appreciate that they will all react differently but am trying to get a feel for the problem. If it was a 32 or 36 I would sling it without question but there are not too many 24 hole about. So if no one has had a catastrophy with a similar one I will probably run it and see what happens whilst I look out for another rim.Any comments appreciated.
Regards
Peter

 

[Midlife]

Are they something like Service des Courses ?

Shaun

 

[half cog]

Re:

Hi Shaun.
Pretty much like the mavic service de course specials on velo base except a lot lighter.These are around 320 gms a rim.They have the same grey anodizing as those on velo base.I dont even think the guy who sold me these knew the cracks were there they are so thin. I could even convince myself that they are just in the anodising to be honest but in reality thats doubtful.Probably going to be a case of stick them on an old bike, tighten the helmet and bomb up and down the road for a bit. If nothing happens then put them on the bike they were bought for. As said before any comments from other peoples experiences would be most welcome. Thanks for getting back to me
Regards
Peter

 

[Midlife]

Not so light as the Medale do'r at 260 gms a rim which were a bit frightening with 28 holes.....

If it was failure due to fatigue / stress corrosion then it would be only one spoke hole. Have a google on why the Comet airliner fell from the sky or why the Liberty Ships fell apart.

Shaun

 

[bm0p700f]

Re:

don't trust aluminium with even small cracks in it, it is simply retire the rims and rebuild with something else. you may wonder why no one make 320g tubular rims anymore and this problem is one of the answers.

 

[mattr]

Biggest problem is the cracks you can't see yet.
With only 24 spokes, once the first one goes, the risk is that the whole rim will unzip itself.

Or at least you'll lose a few more spokes also immediately! Not a pleasant outcome on a front wheel.

 

[half cog]

Re:

Hi.
Thanks for all your comments.It seems that this is more to do with the effects of hard anodizing than rim weight.When I was a young lad some 53 years ago I could only afford one set of wheels for both tt and club runs.I built a pair of fiamme 28 hole sprints tied and soldered on Milremo large flange hubs and rode them week in and week out around the back roads of Yorkshire. They were lighter than the cx18s and there were no cracks despite some very rough country roads. However they were silver and not anodized.I shall probably lay this rim up and keep an eye out for an alternative to go with the hub. There is no mad hurry on this as the bike I bought them for is rarely ridden.One thing I am sure of is that these cracks are so fine and hard to see that I am willing to bet that there are a lot of retro bikers out there riding rims in a similar condition. I only saw mine as I was using a photo flood for something else and they caught my eye in the extra light .Thanks again one and all
Regards
Peter

 

[Midlife]

Hi

Strangely enough I ran Fiamme rims as race / general purpose / training in the 70's and boy were they tough ! below is a pic of my Campag / Fiamme rear wheel leaning against the Falcon which carried it for a shed load of miles some 40 years ago

Shaun

 

[half cog]

Re:

Yes those are the ones. As said mine were 28 hole.having said that I have a 40/32 pair on an old viking I rebuilt. The thing that draws me back to the anodized ones is that you can see the amount of brake wear.Its easy to measure with the verniers on a clincher but you cant do that on a sprint.This rim with the cracks has not done a hundred miles yet.The anodizing is 95% solid on the brake surface. Its not the straightest of builds and I tend to think its spoke over tension and bad building that has contributed to the major part of the problem.The rear wheel is a 24 hole same rim/hub.Its as straight as you can get and has done more milage and there is not a crack in site and thats on a back wheel.At this spoke count tensions need to be very carefully watched.By what I read the anodizing migrates into the alloy during manufacture and it is this that weakens the rims.So I will carry on and risk the back one on the old bike and see what happens to it. A few steady rides should start it going if it is going to. If all is well then I will find another 24 hole rim for the front but a slightly heavier model.If the back one starts to go then its ditch the whole idea and start again.Thanks to all.
Regards
Peter

 

[hamster]

Older Mavics have a reputation for cracking around the holes. I wouldn't consider the rim safe.