This being said after I finished gluing an extremely light 19 mm Vittoria Pista EVO CL tire to a Zipp 1080. The wheel (sans tubular) was almost perfectly balanced but the 110 mm extender threw it out of balance.
I have balanced some discs and spoked wheels putting the magnet in the right place, but I am not sure if it is worth it.
Then I just feel better thinking that the wheel is balanced ;-).
Sergio
Speed of revolution.
Consider the speed a car tire revolves at 90 mph vs how fast a bike tire revolves at 20 mph. Essentially, the car wheels are gonna be a little smaller, and move much, much faster.
It is fairly common for a wheel to be balanced in my area. My LBS counterbalanced a 404 with a small weight added to the rim a while ago, but it’s simple enough to do yourself. At high speed the vibration every wheel revolution can be quite noticeable. Whether or not it’s worth balancing is another story, but as an engineer it’s hard to ignore!
My brother in law asked me the same thing. I said that it makes no difference in a bike wheel because there are only two. As long as they are true I dont really think it matters. Unless you are going to put a slide weight on that felps rotate the wheel forword. Never know could save you a watt or two 
English is my first language and I still screw it up !
Make sure you rotate your wheels every day when not riding, too, so the air doesn’t settle and throw the wheel back out of balance.
It is fairly common for a wheel to be balanced in my area. My LBS counterbalanced a 404 with a small weight added to the rim a while ago, but it’s simple enough to do yourself. At high speed the vibration every wheel revolution can be quite noticeable. Whether or not it’s worth balancing is another story, but as an engineer it’s hard to ignore!
How much do they charge you for that ?
How much do they charge you for that ?
At my LBS, it’s only $34.95 (with nitrogen air fill, of course).
How much do they charge you for that ?
At my LBS, it’s only $34.95 (with nitrogen air fill, of course).
Did you spring the $5.95 for siping?
As much as I’d love to pile on w/ the jokes, I kinda/sorta do this - on any wheel that has a magnet on it, I always put it directly opposite the stem.
And it really does make a difference, at least on the workstand. Out on the road? I dunno, but there’s no harm in it, so why not?
AND you should definitely go for the hydrogen or helium fill-up at the LBS. Go big - have them put it inside the frame tubes too. 
oddly enough Murphy I do this too, but never thought about it as balancing the wheel out in a physical sense, rather as an asthetic sense.
On some of my wheels, directly opposite of the stem is the heavy spot, where the weld is.
I don’t need to balance my awesome hand built Real Design wheels because they are perfect just the way they are.
Mostly, we don’t balance them because, unlike cars, we only have one wheel per axle.
It was included in the charge when getting a wheel trued + spoke replaced. I certainly noticed the vibration on an early model 404 with an 80mm stem tube so I don’t think it’s as silly as some of you guys make it out to be.
Sorry if I implied it was silly. Okay I am not sorry. But I do remember reading about a slide weight to put on the spokes to get wheel momentum going faster. Anyone else remember the product I cannot recall it. I will do a google see if I can find it.
I try to balance my wheels with the computer magnet, and Zipp has a bit on their website about balancing wheels. I swear that i can feel the out of balance on my 303’s because I had to resort to bontrager extenders which are made of steel and weigh about 7grams more than the tufo ones I was using. That wheel and tire are so light it is enough to feel the weight over about 25mph.
I think that the real answer though is that the difference is not significant enough to effect anything.
If you’ve ever gone fast down hill with a wheel thats badly out of balance it can be annoying. On a nearby hill its common to see 70-80km/hr if you really push it, and with this particular wheel it was very noticeable… so I don’t see how it’s such a silly idea.
For the same physics reason that a lighter wheel is not faster on a bike. It has little to do with rotational speed.