Bontrager Select Wheels - cracked Rims

[jim beam]

RonSonic wrote:
> On Sat, 15 Jul 2006 22:21:08 -0700, jim beam <[email protected]> wrote:
>
>
>> bottom line, the benefits of extrusion outweigh the problems by such a
>> huge margin, don't even waste another breath arguing about it. the only
>> "disadvantage" of extrusion, anisotropy, is in fact a huge advantage as
>> far as hoop strength is concerned, and any cracking issues can be
>> mitigated by quality control in manufacture, eyelets, and building with
>> correct spoke tension. the latter of course is hard for a manufacturer
>> to enforce, especially in the light of the immortal words "tension as
>> high as the rim can bear", but that's why we now have "boutique" wheels
>> these days.
>
> "Tension as high as the rim can bear" seems to not be the problem. The problem
> would seem to be tensioning higher than the rim can bear.

excellent, go to the top of the class! that is exactly right ron, spoke
tension just below buckling threshold /is/ well in excess of the tension
the rim can bear for cracking. phew!

>
> The former is, by definition, not excessive.
>
> But it does open the door to the "some's good, more's better" mindset.

only if the fundamentals are not understood and experience ignored.

>
> Ron

 

[David]

On Fri, 14 Jul 2006 04:02:25 GMT, "Beanzy"
<[email protected]> wrote:

>G'day All,
>
>I purcahsed a new Trek 1400 in october last year.
>
>I got a broken spoke on the weekend and dropped off the wheel at the LBS and
>got a phone call later stating that the rim is cracked and that it is
>unsafe to ride. The LBS was in contact with Trek to ascertain warranty
>issues etc. The Trek rep wasnt in but they will keep me posted.
>
>I looked at the cracks yesterday and my god they were everywhere although i
>didn.t notice them when fixing a puincture the day before! My question to
>the group is about their experiences whit this wheelset. I did a google
>search and it seems that some Bontrager wheelsets have a symptom of cracks
>as well as overtensioned spokes. My whee/bike has been reguraly serviced by
>LBS in the time i have had it.
>
>Assuming that trek replace the wheel all is good, but how do i prevent it
>happening again or is it a suck and see?
>
>If they do not replace the wheel any recommendations on a new wheel set?.
>For the record i am a "larger" rider approx 120kg but they weight is coming
>off. I can also do a mean sprint!
>
>Cheers
>
>Beanzy
>

Beanzy,

It's not that all uncommon for these low spoke count wheels to break.
Sometimes they'll last for years trouble free only to fail when ridden
in roads that are going to be tough on your wheels.

Last year, I was on a bike tour with several hundred others and the
most common failure the mechanic had to deal with is broken spokes.
Guest which wheels broke the most? Bontrager Race, Race Lites and
X-Lites as well as Rolf V-Pros and the Shimanos (paired spokes
version). In fact, one lady spent more money fixing her Bontrager
Race because she kept breaking them that she had to abandon the ride.
She's not overweight either -- I'm guessing that she's about 165lbs.
While talking to the mechanic, he's seeing a lot of wheel failure now
in the many recent tours he had supported. He's even got the spokes
in stock to repair these wheels!! It's his bread and butter so to
speak. It's amazing how much money people are willing to pay to fix a
weak wheel. That wasn't the case though several years back.

Btw. I do ride a pair of Bontrager X Lite wheels, but I only use
these for racing only. For regular rides, I use a pair of Velocity
Deep-Vs hand-built..

David.
>

 

[AndyMorris]

jim beam wrote:
> RonSonic wrote:
>> "Tension as high as the rim can bear" seems to not be the problem.
>> The problem would seem to be tensioning higher than the rim can bear.
>
> excellent, go to the top of the class! that is exactly right ron,
> spoke tension just below buckling threshold /is/ well in excess of
> the tension the rim can bear for cracking. phew!
>
>>

We used to have rims that could cope with tension to just below buckling
with 36 spokes. Many modern rims cannot take that much tension.

How is that progress?



--
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AndyAtJinkasDotFreeserve.Co.UK

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[jim beam]

AndyMorris wrote:
> jim beam wrote:
>> RonSonic wrote:
>>> "Tension as high as the rim can bear" seems to not be the problem.
>>> The problem would seem to be tensioning higher than the rim can bear.
>> excellent, go to the top of the class! that is exactly right ron,
>> spoke tension just below buckling threshold /is/ well in excess of
>> the tension the rim can bear for cracking. phew!
>>
>
> We used to have rims that could cope with tension to just below buckling
> with 36 spokes. Many modern rims cannot take that much tension.
>
> How is that progress?

you call this:
http://web.onetel.net.uk/~davidwgreen/rimpics/4.JPG
coping with tension?

or these:
http://web.onetel.net.uk/~davidwgreen/rimpics/1.JPG
http://web.onetel.net.uk/~davidwgreen/rimpics/2.JPG
http://web.onetel.net.uk/~davidwgreen/rimpics/3.JPG

that's a much-vaunted mavic ma2, often held up as the paragon of perfect
old fashioned rims. /i/ don't call that coping with tension.

bottom line, anyone that understood fatigue and/or pre-stressed
structures would ever advocate "tension as high as the rim can bear" because

1. fatigue loading at a stress approaching yield is asking for trouble.

2. it makes no account of the dynamic load on rim buckling!!!

 

[C8user]

Last month when having a Shimano Di2 system installed the mechanic found cracks radiating from the spoke holes. Contacted my local Trek dealer and he found that my warranty coverage ended six months prior. He basically said "Too Bad." He did give me the name of his warranty agent. I didn't have to say too much and a new set of wheels were one their way. I did get twenty-five percent off the matching front wheel. The new wheels are now able to take tubeless tires, but I still have clinchers on them.