Triumphrat

09-27-2006

I've got a new America that has got a problem with shimmy in the front. Decelerating from 80-60km is the worst. Just crusing at 70km is kinda OK but feels odd as there is a slight twitch all the time. Sometimes it even feals like the wheel is oval as it bounces a bit.

I've had it back to the dealer serveral times and it keeps coming back - in spec all OK- Well it ain't. In desparation I had a new tyre fitted today, the shimmy is now worse but the twitch is gone.

When looking at the rim while riding I can see the left side is perfectly true but the right side has a very pronounced wobble in the rim. My dial gauge indicates about 5mm wobble but the tyre is 1mm

The steering head has been checked and I'm told they even tried another wheel off an other bike but can't confirm this.

I'm sure the dealer thinks I'm imagining it so I'm considering giving the bike to the salesman to ride for a week so he can experience it and then maybe it'll get sorted.

If anyone has had similar problems or knows what I should try would be great.

RoundSlide · 09-27-2006

If your run-out measurement on the rim was accurate, 5mm seems like an awful lot of slop. Maybe your dealer will pull his head out of his azz after a week's worth of riding.

RedBird · 09-27-2006

I'm not sure just what your terms "shimmy" and "twitch" are describing. I suspect you have a balance problem since the problem is worse with the new tire than before. You may also have other problems such as an out of round wheel, etc.

There are two types of balance: 1) static balance--keeps the wheel from bouncing up and down; and 2) dynamic balance--keeps the wheel making a straight-line foot print (if the dynamic balance is off, the tire will make a foot print similar to the weave of a snake--much less weave though).

Spin balancers, especially the newer ones, should all be capable of doing both a dynamic and static balance; however, the operator probably knows nothing about balance and is just doing a monkey see--monkey do operation. What most often is received from a "spin balance" is just a "fair" job of static balance. A calibrated "bubble balancer" is just as good as any spin balancer for static balance. For dynamic balance, you must spin the tire--a "bubble balancer" cannot do a dynamic balance.

I used to balance my ol' BSA tires myself. I put an "axle shaft" in a vice and set it level with a good level. Then, I removed the wheel assy and put it on the axle and spun it. When it stopped, I marked the heavy spot and added weights and moved them until the tire would no longer move any when placed in any position around the circle. Your goal is the least amount of weight needed, and if you put the same amount on each side (opposite each other but at the same point around the circle), you should affect the dynamic balance the least amount possible.

Good luck,
Larry

Motorboy · 09-28-2006

Steering head bearings will do this every time if they arn't set correctly (preload) and it is rare to find a true mechanic in dealerships at times.....Today most guys in the shop can't find the floor with their feet much less a real problem.........

Find a "real" mechanic and have him check things out....

This kind of problem can put you in the hospital,,,or worst!

kliff · 09-28-2006

If one side looks normal, and the other looks wobbly, at the same time....it sounds as though the tire never "beaded out" on the rim at installation...OR too much air, and not enough soap was applied to get it to "bead out," and the sidewall cords of the tire have been damaged.

There is also the posiblity of rim damage on that one side as well....

I'd take that sucker to someone with some experience, cause if the dealer mechanic can't see a wobble, and you can, he must be blind in one eye, and can't see out the other.

And I'd take it ASAP, and slowly!

09-28-2006

Well it seems clear I should try and find a better mechanic to look into this for me. So the hunt is on.

Thanks for all your suggestions. Hopefully I'll get it fixed before I it bucks me off.

DrPat · 10-02-2006

Hey mate, a shimmy in the front sometimes indicates something amiss in the BACK end, e.g. tyre pressure, swing arm loose, misaligned back wheel (or the 2 wheels not running in alignment with each other); also worth checking fork oil is in there (and fork staunchions are true!). You can work through the whole thing - oh, sometimes a duff wheel bearing will make the difference.

A steering damper would stop the twitch of course, but may mask the problem rather than solve it...
good luck, cheers Pat

10-02-2006

Persistance pays off. I asked the dealer to speak to Triumph again and I now have an entire new front wheel coming. So hopefully in a few weeks when it gets here all will be well and I'll actually enjoy riding my new bike.

RoundSlide · 10-03-2006

Good deal, hope it fixes your problem.

meatwagon · 10-03-2006

A friend had new Scrambler with similar symptoms ;he trued the wheel and still it shook .Finally they diagnosed a tube which was deformed and once changed ,it was fine.Drove him crazy for a while.