Rear wheel balancing

[Martyn B]

Tried a local bike mechanic for the first time yesterday to supply/fit a rear tyre on my GSA.

He took off all the weights that were on it and said that balancing single sided swing arm shaft drive machines was like pissing in the wind - and said he never balances them.

I'd never heard that before but didn't argue coz I don't know - but I bet there's someone out there that does.

Anyway, I took it for run which included a bit of m-way and threw in some twisties afterwards and it seems fine.

Does this guy know what he's talking about or was I just lucky? If he's wrong, perhaps someone should be having a word. The bike before he did mine was a K1200GT so he obviously gets the local Beemer folk going in.

 

[Mr K]

You get your car wheels balanced and it has shaft drive...?

 

[Martyn B]

Yes, but...

You get your car wheels balanced and it has shaft drive...?

It's the combination of shaft and single swing arm that makes the difference - allegedly

 

[Mr K]

It's the combination of shaft and single swing arm that makes the difference - allegedly

I don't see why.
If it's only a few grammes you'll probably be alright, but anything greater and it'll cause uneven tyre wear and vibes.

I'm not a mechanic, but I'd always get them balanced.

 

[RickG]

The problem with many single sided swing-arms, whether shaft drive or not, is that the rear wheel has a bl**dy great hole in it rather than a pair of bearings (like the front wheel) through which the rear axle passes. A 'mechanic' therefore needs an adaptor in order to fit the wheel onto a wheel balancing device so it can be spun to see where the wieghts should be fitted.

I suspect the real candidate for pissing in the wind is getting your guy to invest in the correct kit in order to do the balancing properly since a BMW rear wheel with a new tyre can be just as out of balance as any other. As it's usually harder to notice an out-of-balance rear than the front while riding the bike it's easier to willfully ignore.

Ok, that's the theory as I understand it. Having said this, I've fitted all my tyres to my Gs's in the last 12 years or so and never bothered balancing the rears simply because of the need for an adapter. I do check the fronts by spinning them on the bike with the brake calipers unbolted and held out the way so they dont drag on the disks. I reckon I've only once had to rebalance a front due to noticable shuddering at speed (>90mph). I'm not saying this is clever, or that balancing is unnecessary, simply that for the tyres I've fitted any amount of imbalance that exists is small enough not to notice when I'm riding.

 

[Martyn B]

Aha...!

I suspect the real candidate for pissing in the wind is getting your guy to invest in the correct kit in order to do the balancing properly since a BMW rear wheel with a new tyre can be just as out of balance as any other.

Now that I can really believe!

 

[nedflanders]

The problem with many single sided swing-arms, whether shaft drive or not, is that the rear wheel has a bl**dy great hole in it rather than a pair of bearings (like the front wheel) through which the rear axle passes. A 'mechanic' therefore needs an adaptor in order to fit the wheel onto a wheel balancing device so it can be spun to see where the wieghts should be fitted.

I suspect the real candidate for pissing in the wind is getting your guy to invest in the correct kit in order to do the balancing properly since a BMW rear wheel with a new tyre can be just as out of balance as any other. As it's usually harder to notice an out-of-balance rear than the front while riding the bike it's easier to willfully ignore.

Ok, that's the theory as I understand it. Having said this, I've fitted all my tyres to my Gs's in the last 12 years or so and never bothered balancing the rears simply because of the need for an adapter. I do check the fronts by spinning them on the bike with the brake calipers unbolted and held out the way so they dont drag on the disks. I reckon I've only once had to rebalance a front due to noticable shuddering at speed (>90mph). I'm not saying this is clever, or that balancing is unnecessary, simply that for the tyres I've fitted any amount of imbalance that exists is small enough not to notice when I'm riding.

Doesn't a car wheel get balanced through the bloody great hole in the middle of the wheel , so not sure a bike specific adaptor would even be required as car ones just sit on a cone. I do agree there is no need to balance a rear wheel unless there is something drastically wrong with the wheel itself. Most tyres are balanced at the factory to a degree hence the small arrow that sits opposite the valve. I never bothered with my chain driven bikes because as well as a bloody great chain rattling around the cush drive can also be fitted in any position, at the end of the day if it feels ok (and if there was something wrong you'd feel it) then don't worry about it.

 

[(RIP) Mark H]

Maybe think of it another way, I you stuck a lump of lead on the rim anywhere, (thus throwing the wheel totally out of balance) and rode the bike, do you think you would notice anything? I think you would, and on a smaller scale if your wheel is not balanced, just because you cant notice any effects is it good for the F/Drive, shaft etc to be spinning an unbalanced mass.
Find someone who will balance your rear wheel, I believe they are originally balanced from new by the factory, hence the fitter "removing the Weights"

 

[JJH]

rear wheel goes on a car balancer and works for me. JJH

 

[iftikartaxis]

wheel balance

load of tosh
if the wheel didn't require balancing why did it have weights there in the first place
if you have spoked wheels they sometimes requires attention

 

[WindyChuffer]

I fit TKC80's to my GS myself and never balance them, and they are good for 100mph like that (max rated speed for those tyres). But on the same note, I havent tried road tyres unbalanced.

If you can't feel any more vibration than with the previous balanced tyre, then don't worry about it.


Edit - Actually come to think of it I did once have rear tourance fitted unbalanced on my '54 GS as they tyre shop didn't have the set up for motorbike tyres. No problems.

 

[Mr K]

Any boffins help?

If your wheel/tyre is say 10g unbalanced, how much effect/force does it have/do/cause as you whizz along at 70mph?






PS: As I once told a prospective Mrs K, just because you can't feel it, doesn't mean it's not there....

 

[Yonkyo]

Many years ago, a bike tyre specialist fitter told me it was a waste of time balancing the rear wheel of any bike. He did explain exactly why then, but it was too techy for me to take in.
But it was something like - the only occasion when a bike wheel would require balancing, is if there is a problem with actual wheel itself, e.g. a slight buckle or kink.

Anyhow. Since then I have never had my rear wheels balanced, regardless of whether it’s a ZX-10R , HP2 Sport or my GSA, and all my bike have handled fine and with no problems.

I also have a few mates who are racers in the 600cc Production series, they also never balance there wheels (front and rear) as they say they could never tell the difference due to modern tyre technology.

 

[D6]

the mass of the bike irons out imbalance better when its at the rear, the front goes directly to the handlebars , so u feel it more as it hasnt got as much mass to get through,
hence you can get away without the wieghts on the rear more,
dont mean to say its ok though, but if you can feel owt, it prob is,

iv had a few fronts thats needed doing, trust me, you know when they need doing, but never a rear exept on the drz and that was the tyre lock thingy causin it

 

[Malcvtr]

Here's a couple of interesting and relevant reads...

http://www.marcparnes.com/Buyers_Guide.htm

http://www.marcparnes.com/BMW_Motorcycle_Wheel_Balancer.htm

 

[(RIP) Mark H]

Anyhow. Since then I have never had my rear wheels balanced, regardless of whether it’s a ZX-10R , HP2 Sport or my GSA, and all my bike have handled fine and with no problems.


I would go along with the above statement if someone can explain why BMW bother to balance the rear wheel on a new bike if it’s not necessary

 

[Mr K]

...and why do they balance car wheels/tyres??

 

[smartbear]

cynic

Anyhow. Since then I have never had my rear wheels balanced, regardless of whether it’s a ZX-10R , HP2 Sport or my GSA, and all my bike have handled fine and with no problems.


I would go along with the above statement if someone can explain why BMW bother to balance the rear wheel on a new bike if it’s not necessary

bmw probably bother to balance rear wheels because they can pass the cost onto us

 

[Malcvtr]

Isn't the reason for balancing the possibility that an out-of-balance wheel will put extra strain on wheel bearings, suspension and, possibly, transmission

We need an engineer to tell us

 

[D6]

Isn't the reason for balancing the possibility that an out-of-balance wheel will put extra strain on wheel bearings, suspension and, possibly, transmission

We need an engineer to tell us

its mainly to stop your arse/teeth vibrating off, but yes , it can put a surprising amount of load on something, but i would say if it vibed hard or long enough to break something, your either very numb or the part was weak