Wobble be gone!

[jezhiggins]

Been pedalling around on my (still feels like) shiny new Lemond Etape for just over a year now. It's ace, and I love it, and you should all go and get one for yourself.

Recently, as I've started to do more miles more quickly, I've had one tiny doubt. At higher speeds, say over 20mph, there seemed to be a bit of a funny feeling in the back wheel. It was certainly something a bit odd going on at 30mph. But I didn't know what. At that kind of speed you can't been looking back under your leg at your wheel. I checked thespokes, the tyre, that it was true.  Everything was fine.

Last night I did a bit work on it, and as I finished I picked up the bike and turned the pedals by hand. I let go of the pedals to change the gear, and the bike suddenly started bucking in my hand. I cranked the pedals again, faster, and let them go. The whole thing was kicking like a mule, forwards and back. There was a wobble. A massive great wobble.

The only asymmetric thing about the wheel was in the reflector attached to one of the spokes. I took it off. I cranked the pedal, and could immediately feel the difference. When I let go of the pedals and let the wheel just spin, the bike was still and steady in my hand. It seemed amazing that a piece of plastic weighing only a few grams could make such a difference, but it clearly was. I whipped the reflector off the front wheel too.

Riding out this morning, the bike felt so much better at speed, smooth and stable. Hurrah! 

Is this well known?  Am I a twit for not realising sooner?

[Phil]

I think I read about this phenomenon from Sheldon or Richard Balantine, I forget which.  A swift google brings up andygates of this parish, posting on bikeforums.net with the following advice:

Damn, I thought I invented the reflective tape idea. My rims are absolutely festive with the stuff (and reflective sidewall tyres on one bike too). Wheel reflectors unbalance the wheel and look dorky. 'flec tape is so much cooler and you can custom it however you like.

I've never personally noticed a reflector unbalancing my wheels, but I always remove them just in case.  I've also seen them cause broken spokes, and they obviously will affect performance slightly.  I don't think they do much for your visibility either. 

[Cudzoziemiec]

Reflective tape on the rims? Presumably that's on the "inside" of the rims, between the spoke eyes, as on the "side" of the rim it would provide a somewhat slippy braking surface. Or is there some amazing high-friction shiny tape?

[andygates]

Yes, wheel reflectors unbalance a wheel and that can cause a wobble at speed.  Setting up two reflectors opposite each other can cancel that out.  If you have one, put it opposite the valve...

Jez, you're not a twit - call it parallel learning.  Reflectors are supplied with new bikes so people assume they're fine.  Spinning the wheel fast a workstand is the most obvious way to reveal the unbalancing, and not everyone does that.  Top deducting. 

Wheel reflectors *are* fine at low speed, they're not fine at high speed.

My reflective tape is on the inside face of the rim, as I am not a grade-A fool

[Cudzoziemiec]

But then they don't face sideways, which I always thought was the point of wheel reflectors, and which is nicely achieved by reflective sidewalls too. I know they should still be visible at an angle, but if you have rims where the inside face is perpendicular to the sidewalls, then they're optimised for visibility from front or rear. Not that this is to justify either speed wobbles or grade-A foolery  just nitpicking cos work's boring this afternoon.

[clarion]

Schwalbe Marathon = reflective sidewall.  There may be lighter tyres that have this.

[Cudzoziemiec]

I think all Schwalbe's have this, don't they? And isn't it required by law in the Netherlands?

[andygates]

But then they don't face sideways, which I always thought was the point of wheel reflectors

True.  But they're ever so blingin' face-on. 

[orienteer]

I think all Schwalbe's have this, don't they? And isn't it required by law in the Netherlands?

The Stelvios don't, so my newly acquired Brompton has the wretched wheel reflectors - at present....

[mattc]

But then they don't face sideways, which I always thought was the point of wheel reflectors

True.  But they're ever so blingin' face-on. 

Stretch some tape between the spokes (i.e. where a reflector goes) ?

[andygates]

You're confusing "blingin" with "fugly" again.

[mattc]

Sorry ...

I was thinking that anyone who has accepted Schwalbes with reflective sidewalls into their lives (e.g. me) has realised that bling is out of their reach, but safe-at-night may be just achievable (on the average audax I assure you I am not alone in this).

(I'm also hoping someone will prototype my idea before I ruin my own bike).

[TimO]

I remember trying tyres with reflective sidewalls something like 15-20 years ago, before they were as common as they are now, and whilst they are fine in principle, unless you are of the habit of regularly washing your commuter (which I'm not !) they soon get dirty enough that they don't work anywhere near as well as when new.

They can be impressively visible when new/clean though.

Plastic reflectors are the work of the devil, I've always binned them when I had them on a new bike.  Luckily the Pomp didn't come with any, so it saved me the effort!

[ABlipInContinuity]

confession time: I always took rear reflectors off. And the front one too.

Lights work so much better.

I do think the reflective strip on the marathon's works incredibly well.

[hatler]

Out of balance forces increase as the square of the rotational speed.

So if you had ever hit 40 with the reflectors on life could have got interesting.

Is it law that bikes are sold with these things ?

I was always of the view that if a vehicle approaching you from the side can't see you, then no amount of reflective stuff is going to help.

I have however lathered my rims with reflectives (between each pair of spokes) and have had reports from car driving colleagues that it is at least eye catching.

[border-rider]

Back before I knew stuff, I had a bike with a front spoke reflector - which came adrift and jammed in the forks.

Luckily it was low-speed, but it required a new pair of forks.  I'd never use them, ever, as a result.

[TimO]

Is it law that bikes are sold with these things ?

I think it is, either that or a strongly advised industry standard.  Things like which way around the brake levers are, and the fitting of reflectors and a bell.  I think a bike needs front and rear reflectors, wheel reflectors, and pedal reflectors to be fitted at the point of sale.

This only applies to complete bikes, which is why racing bikes and their ilk are often sold without pedals (aside from the fact that many people change pedals over to their favourite fixing anyway).  Without the pedals they are not complete bikes, so don't have to have all these reflectors which most racers would remove and bin almost immediately.

[Cudzoziemiec]

Blinging, fugly, I think sidewall reflectors on tyres actually look good. 

I have seen bikes with a kind of all-the-way-round in-and-out the spokes wraparound reflctive job. Which is rumoured to be effective, but looks awful.