True but unbalanced

[Luke]

A month ago I laced up a set of MTB wheels using 36h Mavic X-618 rims.
The build went smoothly (I'd laced up about a dozen wheels before
this), and the wheels were tensioned and trued with no complications.
But when holding the spinning front wheel (sans tire, tube and rim
tape) by the axle, it's surprising how unbalanced it is. Forget about
steadying as it oscillates with each rotation. I've met with this
phenomenon before, but previously it was negligible, certainly never so
severe as this.

Back on the trueing stand the wheel always settles with the rim joint
at 6 O'clock. The X-618 rim has a welded (SUP) joint; I suspect the
culprit is the extra (excessive!?) matter added during the welding
process. Shoddy QC?

Luke

 

[Calvin Jones]

It is possible your wheel is not better or worse then many wheels out
there, including wheels that win races every day. If you mount the
tire and tube you may find the balance again changes. With some effort
and time, you may be able to move the tire around the rim, and swap the
tube so that it counters the unbalanced nature of the rim.

It has been discussed here and other forums that you can add weight to
spokes to also balance the rim. This is true, but adding weight,
especially to the rotational mass of the wheel, is not appealing to
many riders.

You might simply want try the wheel, descending the fastest hill you
can find. It is possible, even likely, that you will find that the
wheel works without issue.

 

[Mark Hickey]

Luke <[email protected]> wrote:

>A month ago I laced up a set of MTB wheels using 36h Mavic X-618 rims.
>The build went smoothly (I'd laced up about a dozen wheels before
>this), and the wheels were tensioned and trued with no complications.
>But when holding the spinning front wheel (sans tire, tube and rim
>tape) by the axle, it's surprising how unbalanced it is. Forget about
>steadying as it oscillates with each rotation. I've met with this
>phenomenon before, but previously it was negligible, certainly never so
>severe as this.
>
>Back on the trueing stand the wheel always settles with the rim joint
>at 6 O'clock. The X-618 rim has a welded (SUP) joint; I suspect the
>culprit is the extra (excessive!?) matter added during the welding
>process. Shoddy QC?

It's hard to say without seeing it, but keep in mind that when you put
a tube in that rim that the "heavy part" (the valve and reinforced
area around it) will be mounted precisely opposite that "heavy part"
of the rim. I can always feel the imbalance in a built wheel, but I
rarely can when a tire and tube are mounted.

Mark Hickey
Habanero Cycles
http://www.habcycles.com
Home of the $795 ti frame

 

[Phil, Squid-in-Training]

Luke wrote:
> A month ago I laced up a set of MTB wheels using 36h Mavic X-618 rims.
> The build went smoothly (I'd laced up about a dozen wheels before
> this), and the wheels were tensioned and trued with no complications.
> But when holding the spinning front wheel (sans tire, tube and rim
> tape) by the axle, it's surprising how unbalanced it is. Forget about
> steadying as it oscillates with each rotation. I've met with this
> phenomenon before, but previously it was negligible, certainly never
> so severe as this.
>
> Back on the trueing stand the wheel always settles with the rim joint
> at 6 O'clock. The X-618 rim has a welded (SUP) joint; I suspect the
> culprit is the extra (excessive!?) matter added during the welding
> process. Shoddy QC?

Nah, all wheels do this.

To tune out the vibration, you can mount your computer and magnet such that
they put the magnet towards the lightest part of the wheel. Slide the
magnet outwards to get more balancing effect. Use more weight if necessary.

Remember, the vibration is a function of the form x(t)=X*cos(wt+phi) and
changing the wn=sqrt(k/m) by changing mass unbalance e will determine the
magnitude of your vibration. Up your damping ratio, and your X1/X2 will be
golden.
--
Phil, Squid-in-Training

 

[Werehatrack]

On Wed, 07 Dec 2005 05:11:14 -0500, Luke <[email protected]>
wrote:

>
>A month ago I laced up a set of MTB wheels using 36h Mavic X-618 rims.
>The build went smoothly (I'd laced up about a dozen wheels before
>this), and the wheels were tensioned and trued with no complications.
>But when holding the spinning front wheel (sans tire, tube and rim
>tape) by the axle, it's surprising how unbalanced it is. Forget about
>steadying as it oscillates with each rotation. I've met with this
>phenomenon before, but previously it was negligible, certainly never so
>severe as this.
>
>Back on the trueing stand the wheel always settles with the rim joint
>at 6 O'clock. The X-618 rim has a welded (SUP) joint; I suspect the
>culprit is the extra (excessive!?) matter added during the welding
>process. Shoddy QC?

Many older rims had a steel insert at the joint which took it well out
of balance as a single item. I don't know if mavic does that with the
618. The fusion process itself shouldn't add enough to be all that
remarkable...and remember that a little extra weight at the joint will
be offset by the valve opposite it. In other words, this is a
non-issue.
--
Typoes are a feature, not a bug.
Some gardening required to reply via email.
Words processed in a facility that contains nuts.

 

[Alex Rodriguez]

In article <071220050511149910%[email protected]>,
[email protected] says...
>A month ago I laced up a set of MTB wheels using 36h Mavic X-618 rims.
>The build went smoothly (I'd laced up about a dozen wheels before
>this), and the wheels were tensioned and trued with no complications.
>But when holding the spinning front wheel (sans tire, tube and rim
>tape) by the axle, it's surprising how unbalanced it is. Forget about
>steadying as it oscillates with each rotation. I've met with this
>phenomenon before, but previously it was negligible, certainly never so
>severe as this.

That is because of the extra weight that pinning/welding the seam of the
rim adds.


>Back on the trueing stand the wheel always settles with the rim joint
>at 6 O'clock. The X-618 rim has a welded (SUP) joint; I suspect the
>culprit is the extra (excessive!?) matter added during the welding
>process. Shoddy QC?

Correct. When you consider that Mavic charges a premium for their wheels,
it is unacceptable.
-----------------
Alex

 

[[email protected]]

BALANCE WEIGHT? cut a blown tube with scissors. cut on the mold line.
take say a 6" section of outer tube when placed under the tire's inside
will extend above the tire's contact area -both sides-and see if that
reduces the problem
while there cut one tube complete as above and add it to the front tire
as a slime liner.
take the front slimer and double it on the back.

 

[Luke]

In article <[email protected]>,
Calvin Jones <[email protected]> wrote:

> It is possible your wheel is not better or worse then many wheels out
> there, including wheels that win races every day. If you mount the
> tire and tube you may find the balance again changes. With some effort
> and time, you may be able to move the tire around the rim, and swap the
> tube so that it counters the unbalanced nature of the rim.
>
> It has been discussed here and other forums that you can add weight to
> spokes to also balance the rim. This is true, but adding weight,
> especially to the rotational mass of the wheel, is not appealing to
> many riders.
>
> You might simply want try the wheel, descending the fastest hill you
> can find. It is possible, even likely, that you will find that the
> wheel works without issue.
>

Yes, you're right. While riding the vibration is trifling: after
mounting the rubber, whatever remains of the unevenness is almost
completely dampened by the lower pressure and treads of the MTB tire.

Luke

 

[Luke]

In article <[email protected]>, Alex Rodriguez
<[email protected]> wrote:

> >Back on the trueing stand the wheel always settles with the rim joint
> >at 6 O'clock. The X-618 rim has a welded (SUP) joint; I suspect the
> >culprit is the extra (excessive!?) matter added during the welding
> >process. Shoddy QC?
>
> Correct. When you consider that Mavic charges a premium for their wheels,
> it is unacceptable.

What I find irksome is not that the front wheel is unbalanced per se,
but rather that there is such a discrepancy between the front and rear
rims in the degree of imbalance. If they both behaved similarly a
standard could be inferred; but then, perhaps both the rims fall within
the 'acceptable' limit.

Luke

 

[Luke]

In article <IoDlf.16672$Mi5.504@dukeread07>, Phil, Squid-in-Training
<[email protected]> wrote:

> Nah, all wheels do this.
>
> To tune out the vibration, you can mount your computer and magnet such that
> they put the magnet towards the lightest part of the wheel. Slide the
> magnet outwards to get more balancing effect. Use more weight if necessary.
>
Great trick with the computer magnet. Never even thought of that (among
other things).

> Remember, the vibration is a function of the form x(t)=X*cos(wt+phi) and
> changing the wn=sqrt(k/m) by changing mass unbalance e will determine the
> magnitude of your vibration. Up your damping ratio, and your X1/X2 will be
> golden.

Too bad balancing my cholesterol levels wasn't that easy.


Luke

 

[Phil, Squid-in-Training]

Luke wrote:
> In article <IoDlf.16672$Mi5.504@dukeread07>, Phil, Squid-in-Training
> <[email protected]> wrote:
>
>> Nah, all wheels do this.
>>
>> To tune out the vibration, you can mount your computer and magnet
>> such that they put the magnet towards the lightest part of the
>> wheel. Slide the magnet outwards to get more balancing effect. Use
>> more weight if necessary.
>>
> Great trick with the computer magnet. Never even thought of that
> (among other things).

For perfect balance, take the wheel and hook paper clips onto the spokes
opposite the heavy side. Keep adding paper clips until there is no
imbalance. Take off the paper clips, weigh them, and place another object
of the same weight where the paper clips were. Preferably something dense.
Tada, you've balanced your bicycle wheels.

--
Phil, Squid-in-Training

 

[Phil, Squid-in-Training]

Luke wrote:
> In article <[email protected]>,
> Calvin Jones <[email protected]> wrote:
>
>> It is possible your wheel is not better or worse then many wheels out
>> there, including wheels that win races every day. If you mount the
>> tire and tube you may find the balance again changes. With some
>> effort and time, you may be able to move the tire around the rim,
>> and swap the tube so that it counters the unbalanced nature of the
>> rim.
>>
>> It has been discussed here and other forums that you can add weight
>> to spokes to also balance the rim. This is true, but adding weight,
>> especially to the rotational mass of the wheel, is not appealing to
>> many riders.
>>
>> You might simply want try the wheel, descending the fastest hill you
>> can find. It is possible, even likely, that you will find that the
>> wheel works without issue.
>>
>
> Yes, you're right. While riding the vibration is trifling: after
> mounting the rubber, whatever remains of the unevenness is almost
> completely dampened by the lower pressure and treads of the MTB tire.

Only if the trail is wet will it be dampened. Otherwise, it'll be damped.

--
Phil, Squid-in-Training

 

[Alex Rodriguez]

In article <SQNlf.16733$Mi5.6502@dukeread07>,
[email protected] says...

>For perfect balance, take the wheel and hook paper clips onto the spokes
>opposite the heavy side. Keep adding paper clips until there is no
>imbalance. Take off the paper clips, weigh them, and place another object
>of the same weight where the paper clips were. Preferably something dense.
>Tada, you've balanced your bicycle wheels.

A while back there was a company that was selling weights to help balance
your wheels. It was diamond shaped with a hole in the center and was designed
to fit over the valve stem. That placed the weight exactly opposite the heavy
seam side. Seemed like a good idea, but apparently unecessary since I never
saw mention of these again.
--------------
Alex

 

[Luke]

In article <FSWlf.16742$Mi5.11309@dukeread07>, Phil, Squid-in-Training
<[email protected]> wrote:

> > Yes, you're right. While riding the vibration is trifling: after
> > mounting the rubber, whatever remains of the unevenness is almost
> > completely dampened by the lower pressure and treads of the MTB tire.
>
> Only if the trail is wet will it be dampened. Otherwise, it'll be damped.

I'm all wet.

 

[Mark Hickey]

"Phil, Squid-in-Training" <[email protected]>
wrote:

>Luke wrote:

>> Yes, you're right. While riding the vibration is trifling: after
>> mounting the rubber, whatever remains of the unevenness is almost
>> completely dampened by the lower pressure and treads of the MTB tire.
>
>Only if the trail is wet will it be dampened. Otherwise, it'll be damped.

While "damped" is the most common usage, "dampened" can mean the same
thing (and you can stay dry doing it). ;-)

Mark Hickey
Habanero Cycles
http://www.habcycles.com
Home of the $795 ti frame

 

[Werehatrack]

On Wed, 07 Dec 2005 17:58:08 -0500, Luke <[email protected]>
wrote:

>In article <[email protected]>, Alex Rodriguez
><[email protected]> wrote:
>
>> >Back on the trueing stand the wheel always settles with the rim joint
>> >at 6 O'clock. The X-618 rim has a welded (SUP) joint; I suspect the
>> >culprit is the extra (excessive!?) matter added during the welding
>> >process. Shoddy QC?
>>
>> Correct. When you consider that Mavic charges a premium for their wheels,
>> it is unacceptable.
>
>What I find irksome is not that the front wheel is unbalanced per se,
>but rather that there is such a discrepancy between the front and rear
>rims in the degree of imbalance. If they both behaved similarly a
>standard could be inferred; but then, perhaps both the rims fall within
>the 'acceptable' limit.

Rear hub bearings typically have slightly higher drag than front, even
with the chain off; might this be coloring the perception?
--
Typoes are a feature, not a bug.
Some gardening required to reply via email.
Words processed in a facility that contains nuts.

 

[Luke]

In article <[email protected]>, Werehatrack
<[email protected]> wrote:

> >What I find irksome is not that the front wheel is unbalanced per se,
> >but rather that there is such a discrepancy between the front and rear
> >rims in the degree of imbalance. If they both behaved similarly a
> >standard could be inferred; but then, perhaps both the rims fall within
> >the 'acceptable' limit.
>
> Rear hub bearings typically have slightly higher drag than front, even
> with the chain off; might this be coloring the perception?

It very well may. Your specifically focussing on the rear hub has left
me wondering about another aspect of rear wheel I hadn't considered:
its overall mass. The rear wheel's hub, a Phil Wood FSC, is a
substantial piece of hardware, much heavier than the front. When I held
the spinning rear wheel, I wonder to what extent the extra weight
contributed to my perception of it being built from a better balanced
rim. Would it have much of an effect?


Luke

 

[Mark Hickey]

Luke <[email protected]> wrote:

>In article <[email protected]>, Werehatrack
><[email protected]> wrote:
>
>> >What I find irksome is not that the front wheel is unbalanced per se,
>> >but rather that there is such a discrepancy between the front and rear
>> >rims in the degree of imbalance. If they both behaved similarly a
>> >standard could be inferred; but then, perhaps both the rims fall within
>> >the 'acceptable' limit.
>>
>> Rear hub bearings typically have slightly higher drag than front, even
>> with the chain off; might this be coloring the perception?
>
>It very well may. Your specifically focussing on the rear hub has left
>me wondering about another aspect of rear wheel I hadn't considered:
>its overall mass. The rear wheel's hub, a Phil Wood FSC, is a
>substantial piece of hardware, much heavier than the front. When I held
>the spinning rear wheel, I wonder to what extent the extra weight
>contributed to my perception of it being built from a better balanced
>rim. Would it have much of an effect?

It would make the effect of the imbalance relatively less. Think about
spinning a 200 pound steel disc with an imbalance of a well under an
ounce - you'd never be able to feel it. OTOH, if you had a bicycle
wheel-sized disc that weighed half an ounce, that same imbalance would
seem enormous.

Mark Hickey
Habanero Cycles
http://www.habcycles.com
Home of the $795 ti frame

 

[Phil, Squid-in-Training]

"Mark Hickey" <[email protected]> wrote in message
news:[email protected]...
> "Phil, Squid-in-Training" <[email protected]>
> wrote:
>
>>Luke wrote:
>
>>> Yes, you're right. While riding the vibration is trifling: after
>>> mounting the rubber, whatever remains of the unevenness is almost
>>> completely dampened by the lower pressure and treads of the MTB tire.
>>
>>Only if the trail is wet will it be dampened. Otherwise, it'll be damped.
>
> While "damped" is the most common usage, "dampened" can mean the same
> thing (and you can stay dry doing it). ;-)

Yes. Although you're right, I still have a holy crusade against wet
suspensions.

--
Phil, Squid-in-Training