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Mavic rim hairline .. danger?

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Mavic rim hairline .. danger?

Old 06-15-19, 04:51 PM
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moto tom
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Mavic rim hairline .. danger?

Greetings all, I'm new but have been reading the forum for the past two and a half years, since I got my old Motobecane Grand Jubilee out of the basement and began riding again after 30 yrs! The bike was gone over by a LBS, new brake pads, cables, new tires, trued rims, all bearings cleaned and repacked etc.. Rides fine, but today, when adjusting the rear wheel I noticed that 1. it's wobbly 2. there are hair line cracks in the old (c. 1976) Mavic alloy rims. The cracks appear at most spoke holes, often on each side of the hole, and radiate out 1/4 to 1/2" at the worst.
I'm guessing not safe for the long haul (I ride about 100 mi/week) so I'd likely change them out. So two questions:

1. still safe for a week or two until I find appropriate replacements? (I know, tough to answer this, but they may have been this way for months?)
2. what are appropriate replacements for this vintage bike c. 1974? BTW, the Mavics were actually replacements for the originals when I hit a huge pothole one night back in the 70s.

I'm not looking for the cheapest replacements, I don't mind quality. I'm using gator skin 32 - 630 tires.

See pic..
Thanks for your help,
Tom


Ok, can't post an image yet..
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Old 06-15-19, 09:59 PM
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Sun makes 27" rims
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Old 06-15-19, 10:10 PM
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Jon T
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Try RETROGRESSION in San Diego, Calif. They have lots of vintage stuff in stock.
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Old 06-15-19, 10:23 PM
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Old 06-16-19, 12:15 AM
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I personally wouldn't worry too much about riding on them as your working on getting the replacements. Maybe don't hop any curbs. There are a wide variety of replacement wheels that could work for you, just make sure the rim and hub dimensions are all the same. Since its friction you have more leeway with your freewheel options, but some aren't compatible so make sure to figure out what will work with the rest of your drivetrain. You could get new rims and try your hand at re-lacing them onto the existing hubs, but I'd just get a new wheelset that checks all the boxes. +1 for the Sun cr-18
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Old 06-16-19, 06:39 AM
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Originally Posted by Jon T View Post
Try RETROGRESSION in San Diego, Calif. They have lots of vintage stuff in stock.
Jon
Thank you for the referral. Although I have lived in north San Diego County for 38 years, I had never heard of "Retrogression." Definitely worth checking out.
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Old 06-16-19, 06:42 AM
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They may have been that way for years...
In my experience, they will not fail catastrophically all at once. In the past, I have had some spokes pull out, but was able to get home, on a less than true wheel.
I have a couple of vintage wheels now that have cracks like this, including a set of shamals. I check them, before and after the ride, and don't mash on them, not that I can even mash much anymore, and the cracks are visually unchanged after riding 600 miles/3 years , (not a daily rotation riding bike.)
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Old 06-16-19, 06:53 AM
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This might be a good time to switch to 700c. Also is your Jubilee set at 120 mm or 126 mm in the rear? This might also be a good time to spread the rear triangle to 126 so you can run 6 or 7 on the back.

You may, however, prefer to build on the old hubs and keep it at 120. One thing to keep in mind is that cones for those hubs are difficult if not impossible to get. You will want to overhaul the hubs before rebuilding the wheels to make sure that the cups and cones are in good shape. If they are pitted, it's likely time for new hubs.

New hubs designed for 120/126 spacing are available. Velo orange sells a hub that can take a freewheel:

https://velo-orange.com/collections/...heel-hub-126mm

Suntour XCD hubs are pretty slick and come in 120 OLD.

Personally I'd seriously think about building new wheels around the velo orange hubs using TB14 H plus on rims even if that means spreading the frame.

TB14 | H PLUS SON

There are other silver rims out there as well but the TB14s look nicely old school.

If building new wheels, I'd find a good freewheel as well. IRD sells 5, 6, and 7 speed freewheels:

Classica Freewheels 5/6/7-Speed ? Interloc Racing Design / IRD

You'll end up with a heck of a nice set of wheels and the shifting will improve to boot.
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Old 06-16-19, 08:18 AM
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Welcome to the forum
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Old 06-16-19, 08:54 AM
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LBS trued your rims, huh?..... Hmmmmmmmmm
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Old 06-16-19, 08:57 AM
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This isn't going to fail catastrophically. At least I've never seen it happen. If you let it go long enough, the spoke can eventually fracture and pull through the rim. This is effectively like a broken spoke. You'll be able to get home, most likely.

Your instincts are right though, it's time to replace. Rims are like socks, they wear out eventually.

I'd personally go for the Sun M13II polished over the Sun CR18. If you peel the sticker off the M13, it looks just like an old Rigida (OEM for this bike IIRC), but they are much stronger rims. The CR18 looks a bit bulky and to me obviously not vintage. Another possibility in 27" is the Velo Orange PBP. No experience with it myself, but it looks the part. https://velo-orange.com/collections/rims
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Old 06-16-19, 09:11 AM
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Originally Posted by trailangel View Post
LBS trued your rims, huh?..... Hmmmmmmmmm
Maybe some suspicion is due, but i'd hesitate to blame them.

Cracks around the spoke holes are caused by too much spoke tension. An old rim that has been trued many times can develop these cracks. Spoke tension gets progressively less even as the wheel gets progressively more old and bent. Some spokes have to be tightened to keep the wheel true.

It can also happen because hamfisted modern mechanics use too much tension on a vintage wheel. 36h non aero rims did not use or need anything approaching typical tensions used today, and modern high tensions are likely to fracture the rim.

In this case I'd guess the former. For someone that rides 100/wk, I'd expect the rims to last maybe 3-4 years, depending on conditions. They are long past that now.
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Old 06-16-19, 09:16 AM
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Thanks so much for the education
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Old 06-16-19, 09:26 AM
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Originally Posted by moto tom View Post
Greetings all, I'm new but have been reading the forum for the past two and a half years, since I got my old Motobecane Grand Jubilee out of the basement and began riding again after 30 yrs! The bike was gone over by a LBS, new brake pads, cables, new tires, trued rims, all bearings cleaned and repacked etc.. Rides fine, but today, when adjusting the rear wheel I noticed that 1. it's wobbly 2. there are hair line cracks in the old (c. 1976) Mavic alloy rims. The cracks appear at most spoke holes, often on each side of the hole, and radiate out 1/4 to 1/2" at the worst.
I'm guessing not safe for the long haul (I ride about 100 mi/week) so I'd likely change them out. So two questions:

1. still safe for a week or two until I find appropriate replacements? (I know, tough to answer this, but they may have been this way for months?)
2. what are appropriate replacements for this vintage bike c. 1974? BTW, the Mavics were actually replacements for the originals when I hit a huge pothole one night back in the 70s.

I'm not looking for the cheapest replacements, I don't mind quality. I'm using gator skin 32 - 630 tires.

See pic..
Thanks for your help,
Tom


Ok, can't post an image yet..
You said you were adjusting the rear wheel. Do you mean truing the wheel ? Did you loosen some spokes before tightening any?
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Old 06-16-19, 10:32 AM
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On second thought, I noticed the OP says most of the spoke holes have cracks around them. This is the classic symptom of an over-tensioned wheel.* It is possible, even probable, that they needed that much tension to true the wheel. However, it's also pretty common for folks that weren't around in the 36 spoke low profile rim days to feel a properly built old wheel, and immediately (and incorrectly) determine the spokes are too loose.

*EDIT: also it can happen just from age and many miles.

Last edited by Salamandrine; 06-16-19 at 10:45 AM.
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Old 06-16-19, 10:33 AM
  #16  
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Whatís the condition of the wheels? Have spokes been coming loose? Are the spokes evenly tensioned? Have they gone out of true? Are you sure the cracks, which I find hard to see in your pic, are new?

My thought is that if the condition of the wheels is not poor or in the process of degrading, there probably isnít a problem if you are not a Clyde.

What about detensioning the wheel, checking the trueness and roundness of the loosened wheel and evaluating it as if it is a new wheel being built? Then slowly and evenly bring it up to an even and useable tension but not too high. Essentially if it behaves like a new wheel it canít be much worse than a new wheel. At least thatís my thought.
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Old 06-16-19, 05:56 PM
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Yuk, just wrote a long, detailed reply to your questions, suggestions and comments. Somehow things got tangled up and lost the post?

Anyway, short version, i'm looking around at some of the ideas offered here .. thanks..Tom
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