Used tyres going out of balance.

[utopia]

In the past I have been surprised, nay staggered really, to find that a rear tyre which only required 5 or 10g to balance it when new, required more like 70 or 80g to rebalance it after about 4000 miles.
I've pondered this on and off , without gaining much insight into why this might happen (to such a large extent) given that all chassis bearings etc are in good nick, wheels accurately in line etc.
Then I bought a front paddock stand, so now I have a pair and could now leave the bike on two stands over the winter, relieving the load on the tyres. I used to leave it standing on both wheels from maybe november through to march.
This got me wondering ... could the developing imbalance be down to tyre deformation rather than wear ?
Surely not, you might think, :twak: but it pays to be thorough and consider all possibilities.
Any thoughts or experiences ?
The tyre in question was a Michelin PR2, by the way.
And yes, I stuck 80g on the rim and ran it for another 3000m. Wasn't entirely happy about it though, but skint at the time.

[Dookbob]

If the tyre was balanced immediately after fitting it, then it could have required rebalancing after only a few miles of use as the tyre settled onto the rim. So it could have needed those extra balance weights long before the 4000 miles.

[Kato]

Tires do move on the rim, and have been known to slip round especially straight after fitting, also any skid however small will remove rubber in a single spot, the state of UK roads can't help with tyre and wheel taking a constant battering, of course might be that none of this is the cause but it certainly won't help

[Mr Gazza]

It may have something to do with new tyres very rarely being perfectly round.

When I was looking into shaving my rear tyre, I came across "Tyre Lathes".
Basically just a rig for spinning the wheel with tyre on, using it's own bearings or spindle.

The "lathe" has a cutter which is moveable (sometimes CNC) and it skims rubber off the tyre as it spins.

It requires little explanation really... The benefits of having a perfectly round tyre, concentric with the axle are much improved smoothness of ride and extended longevity of the tyre and suspension components.

The skimming is done to brand new tyres as well as worn ones and balancing must follow a skim to reap the full benefit.

Four wheelers are usually skimmed flat, but bike "Lathes" are a bit more sophisticated as they need to be cut to a specific profile. In most cases the makers original profile would be desirable, but it can be changed within what the rubber thickness will allow, for special profiles, say for racing.

Sorry I can't post up a link right now, but search "Tyre Lathes"

[Saint aka ML]

Wow fit and ride, fit and ride ladies.

[utopia]

Wow fit and ride, fit and ride ladies.

Wot, and stop thinking ?
Well yeah ok, maybe just a little. :rolleyes:

Alternative answer ... think I've seen that on a packet of condoms. ;)