europa

Bit of a story, with the usual stupid complications, followed by a simple question at the end.
While sitting quietly in my sitting room this morning, the front tyre of one of my bikes blew with an almighty BANG. Cats went everywhere.
Whipping out the offending wheel, a front wheel, the tube had indeed exploded and in doing so, wiped the rubber off a length of the wire bead as it pushed the tyre off the rim. Exit one tyre.
Why did it blow? Looks like I pinched the tyre when I fitted a new tube... over 200 kms ago so it must have been a very small pinch, and I'm glad it happened at home considering all the downhills I've done in that time.

Anyways, one tyre knackered, one tube blown.
My lbs doesn't stock the tyres I like so a quick order online and I'll have it in a few days... with a weekend in the middle... I was planning to do some long riding.

My other bike uses the same sized tyres. Simple, take a tyre from that bike and fit it to the bike in question. But that's a lot of messing about, especially as the tyre would have to go back when the replacement arrives (the tyres on the other bike are worn).
So, I thought, I'll just swap the front wheels over. So my bike will have mis-matched wheels for a few days, so what?
Hmm, the magnet for the bike computer is on the wrong side of the wheel.
Okay, I'll just turn the wheel around.

Now the question.

I'm taking a radially spoked front wheel, that's got over 6,000 kms on it, and running it in the reverse direction. This means the braking forces will be in the opposite direction to what it's been stressed to. Is this going to cause a problem?

The question is academic now as, in a crisis of confidence, I'm going to mount the wheel in the same direction it's used to and refit the computer magnet. I'd still like to know the answer though, from a learning POV.

Marcus_Ti

Flipping a wheel around may result in: frustration, disgust, system abends, disk head-crashes, general malfeasance, floods, fires, shark attack, locust infestation, cyclones, hurricanes, tsunamis, local electromagnetic disruptions, hydraulic brake system failure, invasion, hashing collisions, normal wear and tear of friction surfaces, cosmic radiation, inadvertent destruction of sensitive electronic components, windstorms, the riders of nazgul, infuriated chickens, premature activation of a distant early warning system, peasant uprisings, halitosis, artillery bombardment, explosions, cave-ins, borg-assimilation and/or frogs falling from the sky....












J/K just do it.

sweeks

You forgot "erections lasting more than four hours"!
Steve

europa

I KNEW I was right to turn it back, my cats are scared of Nazgul

CliffordK

I assume you have rim brakes on your radially spoked wheel.

Very little torsional force gets transmitted to the hub, and thus allowing radially spoked wheels on the front.

Technically some tires with tread are directional, but generally only because in theory the tread is better at clearing water in one direction than the other. Around here, that wouldn't make any difference in the summer.

Of course, one option is to just install a wheel magnet at the place where your sensor requires it (is it at exactly the same level on both bikes?) Mounting two wheel magnets won't cause a polar field shift on Earth.

Can you say what brand/model of tire blew? I had a Conti Gator Hardshell that blew recently, "just riding along", about 75 miles from home, and a little less than halfway into my ride. In my case, the tire was a tight fit onto my RS-10 wheels, but the blow occurred nearly opposite from where I "finished" mounting the tire. I checked for a pinched tube. I blame the blow on a weakness in the tire plus diurnal temperature shifts from mounting to riding.

FBinNY 

Since you can flip it, it's safe to assume it's a rim brake hub. As such, there is zero torsional stress possible between the rim and hub. All the torsional stresses are between the brake track and ground, namely within the tire.

So, no reason to even think about it.

BITD - riding tubulars in the mountains in the summer, I found that the heat woulld soften the glue and cause the tires to creep. The rear would move in response to it's job pushing the bike forward, and the front in response to braking forces, and over time both valves would be tilted (best evidence of creep). I had to reseat the rear tire, but for the front, I'd simply flip the wheel and let it creep back home by itself.

xenologer

setting aside the fact that
flipping the wheel is inconsequential for the spokes

just how hard is it to move a magnet?
or better yet, simply live without knowing your exact speed for a few days?

europa

Thanks all. I'd completely overlooked the fact that the caliper will grab the rim while the hub is just there enjoying the scenery.

I was digging through my tool box for a screw driver to move the magnet, when I found another one, so now my poor bike has mismatched wheels and two magnets on the front one - no polar shift in the earth but I did notice cars moving towards me as they went past.

Normally I wouldn't have worried about this but the wheelset is off my good bike and the wheels are still as built by Miche - I just didn't want to mess them around by doing something daft. Had they not been radially spoked, I wouldn't have given it a second thought but even after all this time, I'm wary of that spoke pattern (give me a good three cross pattern any day but that's as they came).

The blow out is in no way the tyre's fault. You can clearly see where I'd lightly pinched the tube and that's what caused the failure. The tyre was damaged as the blast blew the bead over the edge of the rim, scraping the rubber off the wire bead.

Thanks for your help. My legs are complaining about two hours riding into a head wind and I learned something. Good day.

Retro Grouch 

All of the above assumes that both wheels were properly dished. How lucky are you normally, keeping in mind that you just had a tire blow off the rim in your apartment?

rydabent

The wheel will never know it is turning the other way.

HillRider

If there were any significant torsion on the spokes, radial lacing would not be feasible. Note disc brake wheels are not laced radially.

Put both magnets on the same side and you can ride twice the distance at twice the speed!

europa

Wot? Cheat? I could never look my cat in the face again

70sSanO

I guess what got me was how does one know the true correct direction on a radial laced wheel to even ask the question?

John

europa

In my case, it was reversing a wheel that'd been working in the same direction for six years. With a new wheel, you'd have to look at the stickers on the hub (nuffin worse than looking down at your hub at traffic lights and realising the brand name is upside down, all the cats would point and laugh)

FBinNY 

Front wheels (without hub brakes) have no true or correct direction of rotation regardless of how they're built. The sole function of the spokes is to support the hub in the center of the rim, and rotation direction has no effect either way.

CliffordK

If one always puts the QR mechanism on the same side, and never changes it, then one would always install the wheel back the same way... plus the wheel magnet location (in case one ever services the hub and removes the skewer).

In theory radial car tires are supposed to always be driven the same direction, after the first mounting. So, mount it once either direction, then after that, always the same. Shops frequently mark right vs left when removing the wheels.

FBinNY 

The comparison to radial auto tires is inapt.

Bicycle tires are bias ply construction so a fairer comparison (if one were to make one) would be to bias ply auto tires, which were normally rotated in an X-pattern, ie. right front to left rear, so direction of rotation obviously wasn't an issue.

CliffordK

I wasn't comparing tires. But, there is a lot of discussion about re-lacing a wheel and trying to use the same spoke pattern it was originally laced with. Personally I don't think it makes any difference, although changing the lacing pattern will put new divots in the hub. So, I think the OP's thoughts with reversing wheel direction were the same.

There are few drive wheels that are laced radially. I think it wasn't uncommon to lace penny farthings radially. And, I have a single speed wheel that I bought that has something like 72 spokes, radially laced.

europa

But mine is a track wheel, it has nuts

You're point's a good one though, once a bike is set up, there should never be any confusion about which way a wheel goes in (though the greasy, bitey things on the back are a bit of a give away)

CliffordK

I thought you said you had a track wheel...
Doesn't the one in the back go in either direction?

FBinNY 

More clutter. The OP didn't ask about rebuilding the wheel.

It was a simple question about flipping a front wheel whether reversing the direction of roll made a difference.

Simple questions deserve simple, on point answers, which in this case was NO. Bringing in other totally unrelated sort of parallel issues just adds clutter, and tends to create confusion instead of clarity.

europa

On the Hillbrick it will... but it wouldn't do any good because I've only got a cog on one side.

CliffordK

If one had some sort of disc brake, or in the case of the beach cruiser wheel I have down in the basement, a rear wheel laced radially, then one would have asymmetrical stress on the hub through use. So, it would be a valid question whether reversing that stress would be important.

However, as has been pointed out, his rim brakes don't put a torsional stress on spokes/hub interface so the point is mute.