Rim Flex

Hey there,
I had heard that rims have a certain amount of flex (wow!):smiley:
I was wondering is more flex a good (for Muni, ie drops, hops)?
I heard the Ales DX32 had quite a bit of flex due to that the rim is origonally built for bike trials (well the 19" and 26’’)
But i heard the Sun ringle Double wide is the stiffest oot there

Just wondering

Re: Rim Flex

I feel absolutely no flex in the rim, only in the tire… anyone else?


What does a flexy rim on a muni feel like? I’ve never experienced any noticeable flex. The rims that are used for the 24x3 muni wheels are not flexy at all. The DH rims used for the 24x3 wheels are stout.

A lightweight 26" MTB XC rim might be flexy. I had problems with breaking spokes at the shoulders right at the hub on my 26" Pashley with Sun Rhyno Lite rim. I blame the broken spokes on the rim flexing. But the flex is not something you can feel while riding. It just stresses the spokes.

You can’t forget the quality of the wheel build. A good solid wheel build will do more to stiffen the wheel than changing rims.

things that make me go hmmmm

Generally talk of flex is related to a rim used for it’s original application, a bicycle. with two wheels lateral forces are being put on each wheel through every turn and upon every landing and takeoff.
big wheels are much more prone to flex since the spokes are alot longer. flex originates from the spokes squeezing against each other (not stretching and compressing as is commonly thought), the more crosses you have in a wheel the more the spokes interfere with each others displacement causing the wheel to maintain it’s shape. if you’ve ever ridden a radial laced wheel (no crosses in the lacing) you’ve noticed that the wheel has a large amount of visible fles when put under any lateral load.

the only flex in a muni wheel would come from landing while moving in a direction perpendicular to the direction your rim would generally rotate, or parallel to it’s axis of rotation… sideways.
it would take way more force than your scrawny little legs could produce to cause a rim to flex from a pedaling force.
when preloading to jump sideways, a small amount of flex could be felt if your tires were rock solid, but if you are sidehopping i would hope your tires would be far to soft to feel anything but your rim hitting whatever you’re jumping onto. the lovely hiss of a pinch flat perhaps.

yeah… i was just trying oot a friends uni who had a DX32 and and different uni that had a double wide and after landing a 2.5 foot drop the double seemed stiffer…

Alex makes a rim with machiened side walls and one without,any chance one of these is more flexy…

Re: Rim Flex

You may not feel the rim flex, especially by comparison with visible change
of shape of the tyre as it is loaded, but flex is there all the same, in
its various forms. Flexing of the tyre will tend to mask out your ability
to detect rim flexing.
Whether it is a good or bad thing is debatable.

“Dylan Wallinger” <extremeunicycler@aol.com> wrote in message
> I feel absolutely no flex in the rim, only in the tire… anyone else?
> Dylan

They probably had the tyre pumped up harder.


I recall from a mountainbiking forum that stiffer rims make adjusting and true-ing the wheel more difficult; because the rim is stiffer any maladjustments will be harder to spot until you land on it…

They didn’t like the Halo Combat rim much for this reason; I stopped reading at that point because I like mine… :slight_smile:

Phil, just me