MA2 rim cracking - what might be causing this?

I'm no expert, but have built several sets of MA-2 wheels, some with many thousands of miles on
them, and haven't seen what you describe.

I did have similar cracking on FiR Nettuno rims on a used bike that I bought several years ago, but
that rim is totally different in design and lacks eyelets.

The Torelli Master rim has the same ERD as the MA-2, I think.

Mike Yankee

(Address is munged to thwart spammers. To reply, delete everything after "com".)

Quoted post said:

Originally posted by David Green
I recently noticed that my rear wheel had developed a lateral wobble which was interferring with my
bottle dynamo. I expected to find a broken spoke but there were none.

When I removed the tyre and rim tape, I spotted cracks in the aluminium beside all of the drive-side
sockets. (MA2s have full-depth steel sockets between the double walls.) None of the non-drive-side
sockets had cracks. Each crack is concentric to the spoke hole and about 1mm away from the edge of
the socket, most pronounced towards the outside edge of the rim. The cracks only appear in the wall
of the rim in contact with the rim tape. No cracks visible when tyre fitted or in braking surfaces.

I assume that the wheel is going out of true because of these cracks.

Is this kind of thing common in MA2s? Do you think that I over tensioned the spokes? I don't think
so, because the wheel never taco'd during stress relieving.

This wheel is 32H, which I built approx 4 years ago, ridden about 40 miles per week on decent roads
(no pothole colisions). Spokes were build according to Jobst's book, stress-relieved etc. Campag sf
hubs, SSDB spokes.

Any suggestions for a replacement rim (same ERD) and for improving my build technique.

David Green. Cambridge, UK.

Very interesting!
I would like to see what Jobst Brandt has to say on this one.
I say that it is fatigue due to the inner wall handling the load and not sharing it with the outer wall. It could be that the inner wall was thinner than it should have been, combined with the socket putting most all the load there. Drive side spokes on the rear wheel, with typical dish, carry a considerable amount of the load.
If you want the same ERD you should look in the Rinard or DT-Swiss charts to make the comparison.
http://www.damonrinard.com/spocalc.xls
http://www.dtswiss.com/index.asp
for this one you will need to click the internal link and agree to their terms.
If you can afford new spokes and want to get some help with evening out the load on the dished rear, you can go with a rim that has offset spoke holes, like Bontrager Fairlane Asym or Ritchey Girder Pro OCR, etc.

[email hidden] (David Green) wrote in message news:<[email hidden]>...

Quoted message said:

I recently noticed that my rear wheel had developed a lateral wobble which was interferring with
my bottle dynamo. I expected to find a broken spoke but there were none.

When I removed the tyre and rim tape, I spotted cracks in the aluminium beside all of the drive-
side sockets. (MA2s have full-depth steel sockets between the double walls.) None of the non-drive-
side sockets had cracks. Each crack is concentric to the spoke hole and about 1mm away from the
edge of the socket, most pronounced towards the outside edge of the rim. The cracks only appear in
the wall of the rim in contact with the rim tape. No cracks visible when tyre fitted or in braking
surfaces.

I assume that the wheel is going out of true because of these cracks.

Is this kind of thing common in MA2s? Do you think that I over tensioned the spokes? I don't think
so, because the wheel never taco'd during stress relieving.

This wheel is 32H, which I built approx 4 years ago, ridden about 40 miles per week on decent
roads (no pothole colisions). Spokes were build according to Jobst's book, stress-relieved etc.
Campag sf hubs, SSDB spokes.

Any suggestions for a replacement rim (same ERD) and for improving my build technique.

David Green. Cambridge, UK.

Dear David,

If you can email me any pictures of your rim, I'd be glad to host them. There are some current
threads about Mavic rim failures in which MA2's are often mentioned in contrast to other Mavic rims,
so I expect that people would be interested in pictures for comparison and better able to give you
helpful advice.

In any case, sorry about your wheel troubles.

Carl Fogel

In article <[email hidden]>, [email hidden] says...

Quoted message said:

I recently noticed that my rear wheel had developed a lateral wobble which was interferring with my
bottle dynamo. I expected to find a broken spoke but there were none.

When I removed the tyre and rim tape, I spotted cracks in the aluminium beside all of the drive-
side sockets. (MA2s have full-depth steel sockets between the double walls.) None of the non-drive-
side sockets had cracks. Each crack is concentric to the spoke hole and about 1mm away from the
edge of the socket, most pronounced towards the outside edge of the rim. The cracks only appear in
the wall of the rim in contact with the rim tape. No cracks visible when tyre fitted or in braking
surfaces.

I assume that the wheel is going out of true because of these cracks.

Is this kind of thing common in MA2s? Do you think that I over tensioned the spokes? I don't think
so, because the wheel never taco'd during stress relieving.

This wheel is 32H, which I built approx 4 years ago, ridden about 40 miles per week on decent roads
(no pothole colisions). Spokes were build according to Jobst's book, stress-relieved etc. Campag sf
hubs, SSDB spokes.

Any suggestions for a replacement rim (same ERD) and for improving my build technique.

Making some pictures available would help in analyzing the failure.
-----------
Alex

Yes, please! Post pics.

This one I gotta be in on!

Mike

(David Green) said:

I recently noticed that my rear wheel had developed a lateral wobble which was interferring with
my bottle dynamo. I expected to find a broken spoke but there were none.

When I removed the tyre and rim tape, I spotted cracks in the aluminium beside all of the drive-
side sockets. (MA2s have full-depth steel sockets between the double walls.) None of the non-drive-
side sockets had cracks. Each crack is concentric to the spoke hole and about 1mm away from the
edge of the socket, most pronounced towards the outside edge of the rim. The cracks only appear in
the wall of the rim in contact with the rim tape. No cracks visible when tyre fitted or in braking
surfaces.

Concentric to and not radiating from the spoke holes? Can you post a photo of this? I'd like
to see it.

Quoted message said:

I assume that the wheel is going out of true because of these cracks.

Makes sense.

Quoted message said:

Is this kind of thing common in MA2s?

No. It was common in MA40s. Question for you- is this an MA2 "argent" silver anodized rim, or a
polished aluminum rim. I've never seen one of the former, but have been assured they existed.

Quoted message said:

Do you think that I over tensioned the spokes? I don't think so, because the wheel never taco'd
during stress relieving.

This wheel is 32H, which I built approx 4 years ago, ridden about 40 miles per week on decent
roads (no pothole colisions). Spokes were build according to Jobst's book, stress-relieved etc.
Campag sf hubs, SSDB spokes.

Any suggestions for a replacement rim (same ERD) and for improving my build technique.

If you can find an MA2, I don;t htink you can do better. But avoid the anodized ones (see the other
threads going on about anodizing and premature rim failures).

[email hidden] (David Green) wrote in message news:<[email hidden]>...

Quoted message said:

I recently noticed that my rear wheel had developed a lateral wobble which was interferring with
my bottle dynamo. I expected to find a broken spoke but there were none.

When I removed the tyre and rim tape, I spotted cracks in the aluminium beside all of the drive-
side sockets. (MA2s have full-depth steel sockets between the double walls.) None of the non-drive-
side sockets had cracks. Each crack is concentric to the spoke hole and about 1mm away from the
edge of the socket, most pronounced towards the outside edge of the rim. The cracks only appear in
the wall of the rim in contact with the rim tape. No cracks visible when tyre fitted or in braking
surfaces.

I assume that the wheel is going out of true because of these cracks.

Is this kind of thing common in MA2s? Do you think that I over tensioned the spokes? I don't think
so, because the wheel never taco'd during stress relieving.

This wheel is 32H, which I built approx 4 years ago, ridden about 40 miles per week on decent
roads (no pothole colisions). Spokes were build according to Jobst's book, stress-relieved etc.
Campag sf hubs, SSDB spokes.

Any suggestions for a replacement rim (same ERD) and for improving my build technique.

David Green. Cambridge, UK.

You don't say how long you have ridden the rim or in what conditions.

I had a non-anodized, tubular rim tear out a socket and the side split away from the rest of the rim
at that point. However, the rim had been on the bike for twenty years and been ridden through all
kinds of muck and abuse and was badly out of true. My theory in that case was that the rim's
sidewall had been worn thin and fatigued at that point to the extent that it could no longer support
the compressive forces on the rim.

The failure mode was fairly benign. I was going down a hill when I noticed that the tire started
rubbing on the frame. Even with this amount of damage, the wheel easily supported my weight and
allowed me to come to a safe controlled stop.

to answer the question, yes, i think over-tension is a likely contributor. wheels need to be well
tensioned so spokes don't go slack in use, but they don't need to be over-tensioned. there is a myth
that the tighter the spoke, the stiffer the wheel - simply not true - so some folks tend to go
overboard on this. over-tension will accelerate aluminum's natural failure process.

David Green said:

I recently noticed that my rear wheel had developed a lateral wobble which was interferring with
my bottle dynamo. I expected to find a broken spoke but there were none.

When I removed the tyre and rim tape, I spotted cracks in the aluminium beside all of the drive-
side sockets. (MA2s have full-depth steel sockets between the double walls.) None of the non-drive-
side sockets had cracks. Each crack is concentric to the spoke hole and about 1mm away from the
edge of the socket, most pronounced towards the outside edge of the rim. The cracks only appear in
the wall of the rim in contact with the rim tape. No cracks visible when tyre fitted or in braking
surfaces.

I assume that the wheel is going out of true because of these cracks.

Is this kind of thing common in MA2s? Do you think that I over tensioned the spokes? I don't think
so, because the wheel never taco'd during stress relieving.

This wheel is 32H, which I built approx 4 years ago, ridden about 40 miles per week on decent
roads (no pothole colisions). Spokes were build according to Jobst's book, stress-relieved etc.
Campag sf hubs, SSDB spokes.

Any suggestions for a replacement rim (same ERD) and for improving my build technique.

David Green. Cambridge, UK.

[email hidden] (Carl Fogel) wrote in message news:<[email hidden]>...

Quoted message said:

Dear David,

If you can email me any pictures of your rim, I'd be glad to host them. There are some current
threads about Mavic rim failures in which MA2's are often mentioned in contrast to other Mavic
rims, so I expect that people would be interested in pictures for comparison and better able to
give you helpful advice.

In any case, sorry about your wheel troubles.

Carl Fogel

Pictures as requested:

Most of the drive side sockets have these cracks:
web.onetel.net.uk2.JPGOpen ↗

Cracks seem to be concentric with the spoke hole:
web.onetel.net.uk3.JPGOpen ↗

When I did look more closely, some of the spoke holes with socket cracks also have small cracks
emerging from the ferrule side of the rim: web.onetel.net.uk4.JPGOpen ↗

Any ideas?

David Green

Great pictures David! Very interesting failure. -tom

"David Green" <[email hidden]> wrote in message
"]news:[email hidden]...

Quoted message said:

[email hidden] (Carl Fogel) wrote in message

news:<[email hidden]>...

Quoted message said:

Quoted message said:

Dear David,

If you can email me any pictures of your rim, I'd be glad to host them. There are some current
threads about Mavic rim failures in which MA2's are often mentioned in contrast to other Mavic
rims, so I expect that people would be interested in pictures for comparison and better able to
give you helpful advice.

In any case, sorry about your wheel troubles.

Carl Fogel

Pictures as requested:

Most of the drive side sockets have these cracks:
web.onetel.net.uk2.JPGOpen ↗

Cracks seem to be concentric with the spoke hole:
web.onetel.net.uk3.JPGOpen ↗

When I did look more closely, some of the spoke holes with socket cracks also have small cracks
emerging from the ferrule side of the rim: web.onetel.net.uk4.JPGOpen ↗

Any ideas?

David Green

"David Green" <[email hidden]> wrote in message
"]news:[email hidden]...

Quoted message said:

[email hidden] (Carl Fogel) wrote in message

news:<[email hidden]>...

Quoted message said:

Quoted message said:

Dear David,

If you can email me any pictures of your rim, I'd be glad to host them. There are some current
threads about Mavic rim failures in which MA2's are often mentioned in contrast to other Mavic
rims, so I expect that people would be interested in pictures for comparison and better able to
give you helpful advice.

In any case, sorry about your wheel troubles.

Carl Fogel

Pictures as requested:

Most of the drive side sockets have these cracks:
web.onetel.net.uk2.JPGOpen ↗

Cracks seem to be concentric with the spoke hole:
web.onetel.net.uk3.JPGOpen ↗

When I did look more closely, some of the spoke holes with socket cracks also have small cracks
emerging from the ferrule side of the rim: web.onetel.net.uk4.JPGOpen ↗

Any ideas?

David Green

HOLY COW! The world's gonna end!

I hate to break it to you Jobst, but your favorite rims crack exactly the same as any others.

Is nothing worth riding if MA2s are going to crack too? Geez! the pressure!

Mike

(David Green) said:

Cracks seem to be concentric with the spoke hole:
web.onetel.net.uk3.JPGOpen ↗

When I did look more closely, some of the spoke holes with socket cracks also have small cracks
emerging from the ferrule side of the rim: web.onetel.net.uk4.JPGOpen ↗

Interesting. No. 4 looks like a typical crack seen on all the rim failures I have had (but those
have literally all been with anodized rims). Nos. 2 + 3 are quite interesting, though. Is the
concentric crack on the non-drive side?

If you posted it, I can't remember: what type of hub, what type of spokes, how many spokes, and how
many miles on this wheel?

Mike S.' mikeshaw2@coxDOTnet said:

HOLY COW! The world's gonna end!

I hate to break it to you Jobst, but your favorite rims crack exactly the same as any others.

You seem to forget that Jobst has also reported a cracked MA2, on his friend Richard Mylarnik's bike
during a tour of the Alps.

Quoted message said:

Is nothing worth riding if MA2s are going to crack too? Geez! the pressure!

Well, we have collected two reports of MA2s cracking, compared to hundreds of various other rims. At
this point, I think the odds are best to stick with the MA2s if you can find them.

definitely interesting! thanks for posting.

briefly, the interesting features to note are:

1. the very good overall condition of the rim - indicative of low mileage and good environment.
2. cracking on the outside surface is off-center of the eyelet hole - center is the point of maximum
stress and the usual orientation for any radial cracking due to any anodizing
3. the outside crack also follows a jagged line indicative of an intergranular fracture mode
4. there is pull-through top & bottom of the socket with cracking on the inside edge.
5. cracking on this inside surface appears to have initiated at the tire bead well shoulder - a
stress riser.

assuming this rim does not have any particular extrusion issue, all these symptoms appear to point
to a tension problem. it's not possible to say which occurred first, the inside or the outside, but
they are both symptoms of the same issue.

were these wheels built using a tensiometer for the spokes? mavic recommended tension for their
later rims is ~1,000N to 1,100N drive side rear. many builders exceed this under the misconception
that the greater the tension, the stiffer the wheel. excess tension does not alter the modulus of
the spokes or the rim so it cannot make wheels stiffer - all it does is push the rim [and all other
components] closer to their stress limit.

David Green said:

[email hidden] (Carl Fogel) wrote in message
news:<[email hidden]>...

Quoted message said:

Dear David,

If you can email me any pictures of your rim, I'd be glad to host them. There are some current
threads about Mavic rim failures in which MA2's are often mentioned in contrast to other Mavic
rims, so I expect that people would be interested in pictures for comparison and better able to
give you helpful advice.

In any case, sorry about your wheel troubles.

Carl Fogel

Pictures as requested:

Most of the drive side sockets have these cracks:
web.onetel.net.uk2.JPGOpen ↗

Cracks seem to be concentric with the spoke hole:
web.onetel.net.uk3.JPGOpen ↗

When I did look more closely, some of the spoke holes with socket cracks also have small cracks
emerging from the ferrule side of the rim: web.onetel.net.uk4.JPGOpen ↗

Any ideas?

David Green

jim beam said:

mavic recommended tension for their later rims is ~1,000N to 1,100N drive side rear. many
builders exceed this under the misconception that the greater the tension, the stiffer the wheel.
excess tension does not alter the modulus of the spokes or the rim so it cannot make wheels
stiffer - all it does is push the rim [and all other components] closer to their stress limit.

You would recommend enough spoke tension that would prevent the spokes from going slack, but no
more? I think Jobst has said about 100 kgf is about the maximum, before the MA2 rim begins to warp
during stress relieving. Sounds pretty close to the 1,000N recommendation.
--
terry morse Palo Alto, CA bike.terrymorse.combike.terrymorse.comOpen ↗

Terry Morse said:

jim beam said:

mavic recommended tension for their later rims is ~1,000N to 1,100N drive side rear. many builders exceed this under the misconception that the greater the tension, the stiffer the wheel. excess tension does not alter the modulus of the spokes or the rim so it cannot make wheels stiffer - all it does is push the rim [and all other components] closer to their stress limit.

You would recommend enough spoke tension that would prevent the spokes from going slack, but no more?

yes, thats right.

Quoted message said:

I think Jobst has said about 100 kgf is about the maximum, before the MA2 rim begins to warp during stress relieving. Sounds pretty close to the 1,000N recommendation.

yes, 1000N ~= 100Kgf

Quoted message said:

--
terry morse Palo Alto, CA bike.terrymorse.combike.terrymorse.comOpen ↗

Tim McNamara <[email hidden]> wrote in message news:<[email hidden]>...

Quoted message said:

(David Green) said:

Cracks seem to be concentric with the spoke hole:
web.onetel.net.uk3.JPGOpen ↗

When I did look more closely, some of the spoke holes with socket cracks also
have small cracks emerging from the ferrule side of the rim:
web.onetel.net.uk4.JPGOpen ↗

Interesting. No. 4 looks like a typical crack seen on all the rim failures I
have had (but those have literally all been with anodized rims). Nos. 2 + 3 are
quite interesting, though. Is the concentric crack on the non-drive side?

If you posted it, I can't remember: what type of hub, what type of spokes, how
many spokes, and how many miles on this wheel?

Dear Tim,

Here's the original post. Looks like campag sf hubs, SSDB spokes, 32h, and 4
years at 40 miles per week ~ 8k miles.

(Personally, I think ugly questions might be raised about bottle dynamos, which
have had a free ride for far too long from the forgiving folks at
rec.bicycles.tech.)

Carl Fogel

David Green wrote:

I recently noticed that my rear wheel had developed a lateral wobble which was
interferring with my bottle dynamo. I expected to find a broken spoke but there
were none.

When I removed the tyre and rim tape, I spotted cracks in the aluminium beside
all of the drive-side sockets. (MA2s have full-depth steel sockets between the
double walls.) None of the non-drive-side sockets had cracks. Each crack is
concentric to the spoke hole and about 1mm away from the edge of the socket, most
pronounced towards the outside edge of the rim. The cracks only appear in the
wall of the rim in contact with the rim tape. No cracks visible when tyre fitted
or in braking surfaces.

I assume that the wheel is going out of true because of these cracks.

Is this kind of thing common in MA2s? Do you think that I over tensioned the
spokes? I don't think so, because the wheel never taco'd during stress relieving.

This wheel is 32H, which I built approx 4 years ago, ridden about 40 miles per
week on decent roads (no pothole colisions). Spokes were build according to
Jobst's book, stress-relieved etc. Campag sf hubs, SSDB spokes.

Any suggestions for a replacement rim (same ERD) and for improving my build
technique.

David Green. Cambridge, UK.

Tim McNamara said:

Interesting. No. 4 looks like a typical crack seen on all the rim failures I
have had (but those have literally all been with anodized rims). Nos. 2 + 3 are
quite interesting, though. Is the concentric crack on the non-drive side?

No. All the cracks are drive side. In fact, most of the drive side spokes
exhibit them.

Quoted message said:

If you posted it, I can't remember: what type of hub, what type of spokes, how
many spokes, and how many miles on this wheel?

It was me. Campag 'Record' 32H small-flange circa 1983. This wheel was built
approx 4 years ago, ridden about 40 miles per week on decent roads (no pothole
colisions). Built according to technique in Jobst's book, stress-relieved etc.
Stainless DB DT spokes.

--
David Green Cambridge, UK.

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with 'onetel.net.uk'.
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jim beam said:

were these wheels built using a tensiometer for the
spokes? mavic recommended tension for their later rims is
~1,000N to 1,100N drive side rear. many builders exceed
this under the misconception that the greater the tension,
the stiffer the wheel. excess tension does not alter the
modulus of the spokes or the rim so it cannot make wheels
stiffer - all it does is push the rim [and all other
components] closer to their stress limit.

I didn't use a tensiometer to build this wheel, so I cannot
state the exact tension. What I did was try to get the
tension nice and high because my understanding is that that
makes the wheel as strong as possible. (By that I mean most
resistant to possible collapse by spokes becoming
detensioned, say by hitting a pothole.)

I frequently stress-relieved the wheel during tensioning,
keeping alert for it 'tacoing' - which Jobst says indicates
the tension is at the limit the rim can stand. However, I
never took the tension that high: I was satisfied with the
nice high 'ping' emitted by the drive side spokes when
plucked, and called it a day.

I find it interesting that you mention wheel 'stiffness'.
That certainly wasn't in my mind as a reason to achieve a
decent tension. I was simply after a durable (strong) build.

--
David Green Cambridge, UK.

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
DON'T MAIL THE REPLY ADDRESS! Before you click 'Send',
replace 'deadspam.com' with 'onetel.net.uk'.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~