Broken: New KH 20" rim



J

joe

Guest
Could this be the first?

Aaron (pluto) succesfully broke the rim of his new KH Trials
yesterday.

He jumped off a foot high wall, and rimed it. The side wall has came
apart, where the join is, which runs all the way round.

The pics didnt come out very well, but here is one:
[image: http://gallery.unicyclist.com/albums/mates2/rim1.sized.jpg]

You have been warned...


Joe,


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J

joe

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C

Catboy

Guest
Im amazed he was able to clip his rim on the ledge, wone ould think that
the tyre would dtop you but I guess not...


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C

Cumbria_Muni&Trials_Club

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Catboy, Aaron apparently did not catch the rim on the corner of the
ledge and markf, the angle was not extreme.

The drop was witnessed by Joe Baxter, Rick Else and Kyle Metcalfe. I
examined the rim immediately afterwards and there were no impact marks
on it, the tyre was still inflated and the rim was immaculate apart from
the split.

It was as if the sidewall had been pushed out and split from the rim by
the sideways tyre pressure upon landing - however, improbable that
sounds!!

Regards
Simon


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X

xtremeskier_

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Ouch... I was just gonna order one, but thats made me hesitate... Think
i'll hold back until we hear from Kris about this.


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J

joe

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Catboy wrote:
> *Im amazed he was able to clip his rim on the ledge, *


it wasnt caught on the ledge. It happened as he landed


Joe,


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K

Ken Cline

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"Cumbria_Muni&Trials_Club" <[email protected]com> writes:

> It was as if the sidewall had been pushed out and split from the rim by
> the sideways tyre pressure upon landing - however, improbable that
> sounds!!

Looks to me like the tire bottomed out so the force of the landing was
transferred to the rim through layers of tire and tube (but not air).
Still, rims don't usually bend easily. I wonder if there is a problem
with improper heat treatment.

There isn't much increase in pressure from compressing a tire,
percentage-wise. It is doubtful that air pressure would cause this.

Ken
 
B

brockfisher05

Guest
the one thing I have learned about new products is there wil always be a
someone who buys it before everyone else so find out who bought and then
find out the details about it so you know if its good or not


p.s like i said before its all new product it still has time to be
perfected just show the rim to kris and tell him the truth on what
happend and see what he can do because kris would not make ****
products:D also put some damn air in your tire and it would not
happen:p


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P

pluto

Guest
It was my usual tyre presure, a little on the low side but not very low,
about 25 PSI, that should never cause what happened and I dont even
weigh much! Seems dodgy to me, I've done at least 6ft on my old ALEX rim
with the same pressure and similar landings i.e not smooth landings, and
it's been fine. This was a faulty rim, no doubt about it.
Aaron


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P

pluto

Guest
Lets hope so. . .
Aaron


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V

vanished

Guest
ya that does sound weird...the only 3 ways i can think of are

1) He landed on a rock, and bottomed out
2) His tired pushed the rim out because of the angle
3) His tire twisted as he landed (due to angle )and exposed the rim


For the first one, I was looking at the rim, and its not a flat bend, is
more a located spot, may an inch or two, and and coupel inches on each
side followed, so maybe he landed on a rock that was two inches or so
wide, or a peice of wood/metal/****.

Number two is probably impossible becasue his tire pressure was only
what, 25.

Number three is very possible. 25psi is just enough to let the tire
twist, if he land at an agle, the rim would hit the ground with force,
and bend out.

SSSssssssssssssounds Suspioussss.


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G

gerblefranklin

Guest
I seriously doubt it's bent up like that on the other side. That'd imply
it broke from straight up and down forces, which is an axis a rim is
typically very strong on.

Vanished, I will enlighten you, since noone else has. 25 PSI on a trials
tire is to most (low mass) riders a rock solid tire. I ride mine about
19-22. Basically, for a mod trials tire, 25 psi is by no means a soft
tire.


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J

john_childs

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vanished wrote:
> *ya that does sound weird...the only 3 ways i can think of are
>
> 1) He landed on a rock, and bottomed out
> 2) His tired pushed the rim out because of the angle
> 3) His tire twisted as he landed (due to angle )and exposed the rim
> *


or
4) A faulty rim

It is possible that the failure could be due to a faulty rim where the
sidewall was too thin. MTB rims can have the sidewall fail like that if
the sidewall gets worn down due to the rim brakes rubbing away too much
metal. Eventually the sidewall gets too thin and the rim fails. The
sidewall of the rim splits just like that KH rim did.

Rims are made by 'extruding' (http://tinyurl.com/4ro5l) aluminum through
an extrusion die. The 'KH rim'
(http://www.krisholm.com/products/index.htm) has a box section where
there are hollow shapes in the extrusion. That is tricky and makes for
a more complicated extrusion process. It could be that the little
hollow box next to the sidewall got too thin during manufacture and
allowed the rim to fail. An engineer or other technical person may be
able to look at the rim and figure out if it failed due to a bad
extrusion. I'm sure Rodger would want to take a look at the rim to
figure out why it failed. If it failed due to a manufacturing problem
then Kris and Rodger are going to want to know about it.

This has gotten me interested in finding out how they extrude hollow
shapes like a boxed rim. I've seen the dies and the process before, but
it was a while ago and I've forgotten the details.


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