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Re: Wheel balancing?

Posted: Thu Mar 21, 2019 4:40 pm
by Lelandjt
MikeD wrote:
Wed Mar 20, 2019 3:38 am
Jobst Brandt once wrote that balancing bicycle wheels with high pressure tires is unnecessary because the tire is so stiff that an imbalance won't cause a bounce. However, for wide, low pressure tires I would think it could. Then, what if you run tubeless tires or tubes with sealant?
Interesting, I know a world cup DH racer who insists on balanced wheels. Sealant spreads out thinly and evenly due to centrifugal force. Also, racers tend to use the bare minimum amount of sealant.

Re: Wheel balancing?

Posted: Thu Mar 21, 2019 9:21 pm
by joshatsilca
youngs_modulus wrote:
Wed Mar 20, 2019 2:25 am
I follow that you’re using the term to distinguish between conventional rolling resistance losses and vibrational losses, but why not just call them vibrational losses or chatter losses?

I mean, lots of situations exhibit step changes (or quasi-step-changes) in drag due to speed: a planing boat can have less drag just after planing than it did just before planing; hydrofoils are an even more extreme example of this. Drag can increase sharply as an aircraft transitions from subsonic to supersonic speeds. I guess you could describe these as changes to impedance, but I haven’t heard the term used that way very often.

A term like “hysteretic/vibrational transition” would be accurate and descriptive, although I concede it doesn’t roll off the tongue. I’m partial to “chatter losses,” I think.

One final note: I used the phrase “snake oil” to describe wheel weights upthread. I didn’t mean to imply that Silca is being intentionally deceptive or promising impossible benefits. I still find the claim of “better handling” to be a little vague, but it’s well within the norms of the bike industry. But if out-of-balance wheels really do produce a perceptible vibration, why not pitch consumers on aluminum-valved tubes for wheels that are heavy at the valve stem? That’s not a “gotcha” question...I’m really curious.
I hear what you're saying about mechanical impedance in a rotating object... though in motor racing 'chatter' already has a solid definition which includes the tire losing contact with the surface and implies momentary loss of traction, which is even further from this case than the two impedances ;-) Hysteretic/vibrational transition is an awesome descriptor, though definitely poses some issues on the branding side!!

Yes, I have a 'Secret Squirrel Society' which I've been fortunate to connect with over a 20+ year career and I definitely have moments where I cannot believe these people will even talk to me!! Something like a dozen text books and even more motorsports and cycling world championships between them!

Lastly, we do also sell what I believe to be the only latex tubes with Aluminum valve stems for this same purpose and our valve extenders are CNC machined from bar stock rather than made from extrusion which allows them to be thinner walled and lighter.. so we actively pursue this from the supply and demand side!

Re: Wheel balancing?

Posted: Thu Mar 21, 2019 9:21 pm
by Weenie

Re: Wheel balancing?

Posted: Fri Mar 22, 2019 6:39 am
by kervelo
snaxez wrote:
Mon Mar 18, 2019 7:28 am
...Campagnolo Bora has already added more weight on the other side if the valve hole.
Campagnolo/Fulcrum has had balanced wheels for years already. I remember that already around 2000-2005 even the aluminium wheels were balanced by using a heavier spoke opposite to the valve hole. Campagnolo is not the only brand balancing wheels: the Easton R90SL rims have decals attached so that the built wheel is in balance.

Re: Wheel balancing?

Posted: Fri Mar 22, 2019 8:40 am
by pdlpsher1
My Campy wheels are balanced at the factory but it’s not perfect because there are variations in tubes used. I fine tuned the balance with the tires and tubes installed. This gives a perfect balance. Two out of four wheels were perfect from the factory. Two needed fine tuning.

Sent from my iPhone using Tapatalk

Wheel balancing?

Posted: Sun Mar 24, 2019 6:46 pm
by Calnago
A balanced wheel will always be better than one that isn't, it's just a matter of how much of an imbalance can be tolerated. On good roads at speed with an otherwise nicely balanced road bike, that imbalance can become very noticeable. In January I took a bike I had been working on out of for test ride. Very nice bike, and noticed right away that something was terribly wrong. But it was so disconcerting on the downhill that I came back to figure things out. Put the bike on the stand to check , and the first thing I noticed was just how unbalanced the rear wheel was. Even made a little video, which I know I've already posted in a couple other threads, but this thread is definitely the most appropriate place for it...

I figured that maybe there was a glob of dried sealant in the tubular, and while hardly worn, the tubulars were crap anyway... so I ripped them off in order to put a nice new set of Arrenbergs on. But before that I threw the wheel in the truing stand to check things out. The tire was so poorly mounted that it was about 4mm out of round, huge when I consider anything more than about 0.5mm to be out of round, and that's at the tire, not the rim, where I would expect even less than that on a good wheel. I kind of thought that was the problem and with a new tire all would be good. In the meantime I sliced open the tire to check for dried sealant but found nothing, so that wasn't an issue. With a new tire nicely mounted I threw the wheel back in the bike and in the stand and wound it up... Damnit!... same thing. It was simply out of balance, a lot, and as far as I was concerned it was unrideable.

So, how much out of balance was it to cause this... well, in the truing stand I played around with it, placing various weights (using old wheel magnets instead of putty) to dial the balance in, then took it out for a test ride, and voila... nice and smooth.
Various magnets etc, (blue tape held on earth magnets temporarily for a test ride so they wouldn't fly off). There was 18 grams in total added weight...

Taped up and ready to roll for testing...

Once verified that the imbalance was the issue, I ventured into a Golf Store (shoot me), and got some packages of little lead weights they use for weighting golf clubs. I used five 3gram strips, 3 on one side of the rim, 2 on the other... a total add of 15grams.


At first I was worried about the unsightliness of the weights, but then actually thought it was pretty cool that you could see the wheel is balanced etc., and didn't worry about it. In fact, I'm going to do this to my wheels as a test, even though I haven't done it prior... the difference with this wheel was so noticeable that I want to see if I can notice a difference with a good wheel where I've never even thought about balancing it before. Campagnolo Bora wheels for example, years ago used to have a "heavy spoke" that they used for balancing. They've since moved to balancing the wheel via the actual carbon layup. I've thrown a few in the wheel truing stand, and it looks like they could be perfectly balance with about 5-10grams of added weight in the exact right spot.

Here's a shot of a 35mm Bora Ultra with a 25mm Arrenberg on it that is perfectly balance (I used earth magnets with stick perfectly to the flat steel spokes, then you can just slide them up and down the spoke as well to fine tune things during the process instead of playing with silly putty). The magnets are just to pinpoint the amount of weight I'll need, and the location on the rim where I'll need to place the strips. Amazingly, this wheel will stay still at any position, and since nothing spins like a Bora with Cult bearings (no grease or seals touching the bearings), this wheel will actually turn with breezes in the house... it's quite satisfying...

And a bit closer... the earth magnets make it really easy to slide and place the weights as long as you're using a wheel with steel spokes. It's kind of like pretending you're one of those huge crane operaters sliding weights back and forth till you get it just right. Then you can just use your judgment as to how much and where on the actual rim that will translate to when you apply the strips. I will use two 3g strips, one on each side of the rim to replace these temporarily placed magnets... even though there are 7.5 grams of magets on the spokes, at the rim I should be able to use a little bit less for the same effect.

I have a bunch of these magnets shown (2.5g each), and smaller ones (1gram each), that in the past I've used as the magnets for my speed sensors and just use AquaSeal to seal them to the spoke at the exact spot where they will fit all my bikes. All sensors are placed so that that wheels are interchangeable between bikes and the magnets line up. From here on I will try to incorporate the placement and size of the speed magnets as part of the balancing act, and use the lead strips as needed at the rim. I've always placed my speed magnet directly opposite the valve for this reason, but now I may do that a little more precisely.

Re: Wheel balancing?

Posted: Mon Mar 25, 2019 3:35 am
by pdlpsher1
I used the lead tape as well but since I have clinchers I put the weight on the inside of the rim. Then I put a piece tubeless tape over the lead tape. So my weights are invisible from the outside. Not sure if you can do the same on tubular rims. Yeah I really like my perfectly balanced wheels. On fast descents the wheels are so smooth. So little effort to make it perfect.

Wheel balancing?

Posted: Wed Mar 27, 2019 9:07 pm
by Calnago
Yeah, I got some of the lead tape as well from the same place but so far have only used the 3g stickons. I haven’t actually put them on my wheels yet but I’m going to even though it’s not been a problem with only being a few grams (5-7) out of balance. Still, after seeeing and feeling the difference between what I considered an unrideable wheel to one that was smooth again, I figure as close to perfectly balanced as possible is never a bad thing.
Re tubulars, no... don’t see how you would get the weights properly balanced on the inside of the rim since you want the tire on and glued when you do the balancing. No big deal... the visibility of a nicely applied weight actually kind of says “These wheels are perfectly balanced. Are yours?” Ha. I’m not sure I’ll notice the difference with wheels that I’ve never felt the need to balance before, but I’m looking forward to trying them out.

Re: Wheel balancing?

Posted: Thu Mar 28, 2019 12:00 am
by robertbb

Re: Wheel balancing?

Posted: Thu Mar 28, 2019 1:16 am
by Calnago
^Yup, gotta love it. Attention to the details.

Re: Wheel balancing?

Posted: Thu Apr 04, 2019 6:52 pm
by TonyM
I had some time yesterday and I decided to check some of my wheels.
Here the results (based on my tires (Vittoria Corsa, Vittoria Open Pavé or Veloflex Corsa) and tubes (all with Vittoria latex tubes 51mm)).
Tha's the weight that I had to add on the opposite side of the valve on the rim:

Campagnolo Bora Ultra
VR: 0.59g
HR: 3.53g

Campagnolo Bora One:
VR: 8.0g
HR: 4.3g

Fulcrum Racing Zero Nite
VR: 3.56g
HR: 0g

Fulcrum Racing Zero
VR: 5.71g
HR: 1.8g

VR: 2.84g
HR: 4.24g

DT Swiss ARC Dogma:
VR: 0g
HR: 1.3g

I did some tests on my bike stand and I could really see the difference before vs. after :thumbup:

Re: Wheel balancing?

Posted: Thu Jun 13, 2019 2:42 pm
by Lelandjt
The WC DH last weekend in Fort William was won with a pretty large weight on the front wheel. I'm thinking this is most advantageous in DH because of the high speeds and big tires that can have larger weight variation.

Re: Wheel balancing?

Posted: Tue Jun 25, 2019 8:33 pm
by Alexbn921
I have been balancing wheels for 10+ years. Makes a difference in high speed decents. The stability improvement is worth the time