Another rim failure - MA3

dkahn400 said:

Following my exploding front rim last month I've now had a failure on
the rear rim, although a much less dramatic one. I noticed yesterday
that the rear brakes appeared to be binding slightly when wheeling the
bike. Checking the wheel it was substantially out of true although no
spokes were broken or obviously loose. I rode it home gently and on
arriving had a closer look. There is a large crack around one of the
spoke eyelets and a bulge where the spoke is starting to pull through
the rim.

The rim is a Mavic MA3, and I know there have been a number of similar
cases of failure in them. It's just under a year old as I changed it
immediately after last year's York rally when it's predecessor, an
Ambrosio Evolution like the one that exploded, developed a sidewall
bulge on the ride up there. The spokes are the original straight gauge
ones from the machine built wheel that came with the bike. According to
Sheldon this type of failure is more common with straight gauge spokes.

I've ordered a Rigida Chrina rim from Spa Cycles and will replace the
MA3 when this arrives. I will then have matching rims again. This will
be the 4th rim that particular combination of hub and spokes have had.
Rather irritatingly the spoke hole is not in the correct place (typical
of machine built wheels) and it is impossible to relocate it properly
in the wide gap between pairs of leading and trailing spokes without
relacing the hub, which would probably be a bad idea.

--
Dave...

Do you think maybe its time for a new wheel builder ?

dkahn400 said:

Following my exploding front rim last month I've now had a failure on
the rear rim, although a much less dramatic one. I noticed yesterday
that the rear brakes appeared to be binding slightly when wheeling the
bike. Checking the wheel it was substantially out of true although no
spokes were broken or obviously loose. I rode it home gently and on
arriving had a closer look. There is a large crack around one of the
spoke eyelets and a bulge where the spoke is starting to pull through
the rim.

The rim is a Mavic MA3, and I know there have been a number of similar
cases of failure in them. It's just under a year old as I changed it
immediately after last year's York rally when it's predecessor, an
Ambrosio Evolution like the one that exploded, developed a sidewall
bulge on the ride up there. The spokes are the original straight gauge
ones from the machine built wheel that came with the bike. According
to Sheldon this type of failure is more common with straight gauge
spokes.

I didn't realise that, but the problem will happen with any type of spoke
if the tension is simply too high for the rim. That's the *rim*, not for
what for what's necessary for a strong wheel! MA3 doesn't have double
eyelets so can't take high tension; perhaps there are additional reasons
too.

Personally I'm just about happy enough to use an MA3 for a 36h front
wheel, but wouldn't use one for anything else. I've had no problems at
all with mine so far. I deliberately went easy on the tension because I
knew of the problem. Lazily chose an MA3 because they're cheap and easily
available.

~PB

Pete Biggs said:

I didn't realise that, but the problem will happen with any type of spoke
if the tension is simply too high for the rim. That's the *rim*, not for
what for what's necessary for a strong wheel! MA3 doesn't have double
eyelets so can't take high tension; perhaps there are additional reasons
too.

Personally I'm just about happy enough to use an MA3 for a 36h front
wheel, but wouldn't use one for anything else. I've had no problems at
all with mine so far. I deliberately went easy on the tension because I
knew of the problem. Lazily chose an MA3 because they're cheap and easily
available.

I was aware of that too, so didn't use the full Jobstian tension but
possibly still overdid it a bit. The only reason I used an MA3 in the
first place was because I needed a new room quickly, and it was the
only 36 hole 700C rim Evans had in stock. I'd already been to Richmond
Cycles who had no suitable rim and where the mechanic solemly assured
me that spokes could never be reused as they would always break.

--
Dave...

MSeries said:

Do you think maybe its time for a new wheel builder ?

No, but I think it might be time for the builder to acquire a
tensiometer, particularly when working with inferior rims such as the
Mavic MA3.

--
Dave...

dkahn400 said:

According
to Sheldon this type of failure is more common with straight gauge
spokes.

Got a link to where he says that? I'd be interested to read more detail.

Thanks.

~PB

dkahn400 said:

Following my exploding front rim last month I've now had a failure on
the rear rim, although a much less dramatic one. I noticed yesterday
that the rear brakes appeared to be binding slightly when wheeling the
bike. Checking the wheel it was substantially out of true although no
spokes were broken or obviously loose. I rode it home gently and on
arriving had a closer look. There is a large crack around one of the
spoke eyelets and a bulge where the spoke is starting to pull through
the rim.

The rim is a Mavic MA3, and I know there have been a number of similar
cases of failure in them. It's just under a year old as I changed it
immediately after last year's York rally when it's predecessor, an
Ambrosio Evolution like the one that exploded, developed a sidewall
bulge on the ride up there. The spokes are the original straight gauge
ones from the machine built wheel that came with the bike. According to
Sheldon this type of failure is more common with straight gauge spokes.

I've ordered a Rigida Chrina rim from Spa Cycles and will replace the
MA3 when this arrives. I will then have matching rims again. This will
be the 4th rim that particular combination of hub and spokes have had.
Rather irritatingly the spoke hole is not in the correct place (typical
of machine built wheels) and it is impossible to relocate it properly
in the wide gap between pairs of leading and trailing spokes without
relacing the hub, which would probably be a bad idea.

This is weird - is it the same wheel builder, are you particularly heavy
or carry a lot of luggage?

Whilst I only do a limited mileage these days, I have never had a rim go
on me in 28 years (plenty of axles did though pre cassette days). I'm
82Kg (13 stone ish) so whilst not over heavy I'm no lightweight either.

I'm out of touch with rim technology but I did use MA40 and Open 4CD and
have pretty much always used Mavic Rims with DT DB spokes. I have also
used MA2 rims (don't know if the MA3 is its successor or not)

My current bike has a 32 hole front hub and I have absolutely no trouble.

I can't see it being solely the rim it must be either a weight or spoke
tension issue.

I would be interested to hear what is the cause.

Cheers

Alan

Alan said:

Whilst I only do a limited mileage these days, I have never had a rim
go on me in 28 years (plenty of axles did though pre cassette days).
I'm 82Kg (13 stone ish) so whilst not over heavy I'm no lightweight
either.

I'm out of touch with rim technology but I did use MA40 and Open 4CD
and have pretty much always used Mavic Rims with DT DB spokes. I have
also used MA2 rims (don't know if the MA3 is its successor or not)

MA3 is MA2's successor but it's inferior in that it doesn't have double
eyelets (to evenly distribute load between inner and outer walls). MA40
was the hard anodised version of MA2. Open4 I think was the predecessor
of Open Pro, both with double eyelets.

Quoted message said:

My current bike has a 32 hole front hub and I have absolutely no
trouble.

What rim?

Quoted message said:

I can't see it being solely the rim it must be either a weight or
spoke tension issue.

MA3 can't take high tension. I think it's as simple as that, and weight
isn't relevant.

I've had exactly the same problem with similar types of rims after I
increased spoke tension. They were fine before that, but I thought higher
tension would make the wheels stronger. That would be the case if only
the rims could take it.

~PB

Pete Biggs said:

Quoted message said:

My current bike has a 32 hole front hub and I have absolutely no
trouble.

What rim?

I believe Open 4CD (you may gather that my mileage is low and i don't
replace my rims very often):-)

Quoted message said:

MA3 can't take high tension. I think it's as simple as that, and weight
isn't relevant.

Excuse my ignorance but why is weight not a factor?

Alan

Alan <[email hidden]>typed

Quoted message said:

dkahn400 wrote:

Quoted message said:

This is weird - is it the same wheel builder, are you particularly heavy
or carry a lot of luggage?

I think David builds his own wheels and my recollection of him is that
he is by no means a Big Bloke™ (probably small to medium).

--
Helen D. Vecht: [email hidden]
Edgware.

Pete Biggs said:

MA3 is MA2's successor but it's inferior in that it doesn't have double
eyelets (to evenly distribute load between inner and outer walls). MA40
was the hard anodised version of MA2. Open4 I think was the predecessor
of Open Pro, both with double eyelets.

Not quite, The Open Pro was preceded by the Reflex. I had them on my
bike until crash damage forced their replacement. Actually this is a
little pedantic, I think Open Pro is nothing more than a renaming of
the Reflex to avoid confusion with the tubular rim of the same name.

Alan said:

Excuse my ignorance but why is weight not a factor?

Well, I don't /think/ it is, but it'd be interesting to be corrected if
I'm wrong.

The higher the tension, the more likely the problem is to occur, and it's
not going to happen at all when there is no spoke tension, eg. in an
unbuilt rim, no matter what weight you could somehow load onto it (rolling
on top of it or whatever).

Weight doesn't significantly increase spoke tension. In fact it
significantly /decreases/ the tension of the spokes at the bottom of the
wheel -- demonstrated by listening to tone as spokes are plucked.

Weight must put some general stresses on the rim, but the deformation is
concentrated particularly around the spoke holes, and in the opposite
direction to the load from weight. The spokes are being "pulled through".

On the other hand, I have noticed that it takes a bike ride or three
before the deformation happens (after over-tightening spokes). Maybe
that's just coincidence with the time delay, or maybe I'm wrong and weight
is a factor after all? (I doubt it's ever the main one though).

~PB

I wrote (before thinking enough):

Quoted message said:

On the other hand, I have noticed that it takes a bike ride or three
before the deformation happens (after over-tightening spokes). Maybe
that's just coincidence with the time delay, or maybe I'm wrong and
weight is a factor after all? (I doubt it's ever the main one
though).

To correct myself (maybe, a bit)......

The constant change of spoke tension as wheel turns must have a fatiguing
effect on the rim material around the spoke holes. The heavier the rider,
the more difference in spoke tension there will be. But these forces are
nothing to a good rim, hence the problem doesn't happen on a good rim with
a sensible amount of tension.

~PB

Helen Deborah Vecht said:

Alan <[email hidden]>typed

Quoted message said:

Quoted message said:

This is weird - is it the same wheel builder, are you particularly heavy
or carry a lot of luggage?

I think David builds his own wheels ...

I do, hence MSeries taking the opportunity to put the boot in above.
:-)

Quoted message said:

... and my recollection of him is that
he is by no means a Big Bloke™ (probably small to medium).

There's quite a lot of me in a smallish package. I'm around 12 stone at
the moment. The bike's quite heavy too - around 40 lbs with the
panniers on. Goes well downhill though.

--
Dave...

Alan said:

dkahn400 wrote:

Quoted message said:

This is weird - is it the same wheel builder, are you particularly heavy
or carry a lot of luggage?

The exploding rim was nothing to do with the build. I simply failed to
notice the amount of wear on the braking surface and allowed the walls
to become too thin. Tyre pressure did the rest.

The MA3 is a notoriously weak rim and I probably used too much tension.
In fact I originally built it quite slack for this reason, but spokes
would loosen from time to time. I retensioned it a couple of months ago
to stop this happening and probably overdid the tension then. If you
search the newsgroups you will find this is a very common occurrence
with MA3s. The older MA2 was a much stronger rim and did not suffer
from this problem.

The other Ambrosio Evolution rim that developed a bulge in the sidewall
was probably just badly made. I can't see how that could be down to the
build. That has also happened to a number of other people with that
model.

--
Dave...

Pete Biggs said:

dkahn400 said:

According
to Sheldon this type of failure is more common with straight gauge
spokes.

Got a link to where he says that? I'd be interested to read more detail.

Sure. He said it here though he didn't go into detail:
<http://groups.google.co.uk/group/rec.bicycles.tech/msg/ddab0013973303e8>.
You were actually involved in that thread, I believe.

--
Dave...

Pete Biggs said:

Weight doesn't significantly increase spoke tension. In fact it
significantly /decreases/ the tension of the spokes at the bottom of the
wheel -- demonstrated by listening to tone as spokes are plucked.

This is getting into dangerous territory. The weight of the rider
doesn't pull the spokes out of the rim because the weight does not
HFTTS, it SOTBS. :-) I think you're right though. The damage
occurs as the spokes come back under full tension as they roll away
from the bottom. The heavier the load, the greater the snap as the
tension goes back on.

Sheldon [1] says that in the days before he began using a tensiometer
he would generally tune the spokes of a wheel he was building to F#. I
think I might have to get my daughter to give me that note on her flute
when I rebuild the wheel.

[1] Have we mentioned him three times yet? He should turn up in a
minute.

--
Dave...

MSeries said:

Do you think maybe its time for a new wheel builder ?

No, MA3s are known to be crapola. I used one last year (fine so far)
because I wanted a replacement for a bent Open 4CD, and the ERD of them
is the same. Otherwise it was new spokes too.

dkahn400 said:

[1] Have we mentioned him three times yet? He should turn up in a
minute.

I just mentioned Sh*ld*ns website here *once* last year and up he
popped. There again I wouldn't want to spend any more time in r.b.t than
I had to :-)

Julesh