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Unsteady Front Wheels

Discussion in 'Technical and Troubleshooting Torque' started by tonee, Nov 20, 2012.

  1. Hello,

    I've got a habit of letting go of the handle bars on down slopes. I've noticed with my Striple the handle bar isn't stable when I let it go freely as the bike cruise down a slope. My previous bikes had a steady front wheel and handle bars however this one shakes as it rolls.

    I thought it was my rear wheel alignment from adjusting the chain but it seems straight to me.
  2. Shakes up and down or side to side?
  3. Have you lost a wheel balance weight perhaps?
    Wat are the tyre conditions? e.g scolloping (Spelling?)
  4. Side to side

    I just went out to check, it has one on the right hand side of the rim. I'm not too sure about the scalloping
  5. I have been told this can sometimes be caused by push from the rear tyre. Have you put the bike in neutral and coasted at approx the same speed down a hill?

    The same thing happens with my bike with my new Pirelli's. It was fine on the old Dunlop's but even with only 5k's on them (and yes I had them rebalanced to check) the new Pirelli's get the front shake when the rear is loaded in gear, but it is fine when in neutral.
  6. Does this also happen with your 5 other bikes ?
  7. How many kays on the front tyre? Tyre wear is the first suspect.

    Scalloping - variations in the tread depth, usually visible where it occurs, off centre.

    Bikes with short "trail" include sport bikes have "faster" steering; they might seem twitchy to some tend to develop this earlier in the tyre wear cycle than those with longer trail and slower steering.

    Scalloping is caused by, as I understand it, a combination of the normal twitchiness of faster steering bikes tyres responding to variations in the road in a similar repetitive way. Tyre balance can be a factor, as can steering head bearings, Front shockers or even disks, though you can discount disks as a causeif they operate smoothly and don't "throb" on application.

    Once scalloping is established, and it may not be visible at first, it tends to aggravate the shakiness and develop further, a little like corrugations in a road. It sets up a little bounce, or wobble in your line when cornering you might not even notice, which wears the same places systematically and it goes on from there.

    People with sport bikes often fit steering dampers which help arrest the shakiness. Very finely balanced wheels, with a rebalance at half the tyre service life helps. Most tyre fitters don't do this very well I think.

    Steering head bearings, when worn, or out of spec. can contribute to this. they need to be done up to a spec. If they are too loose or worn, it often shows up as unusual "head shake"

    There are some ideas. As I said at the start, begin with tyre wear.
    • Like Like x 1
  8. #8 Ljiljan, Nov 21, 2012
    Last edited: Nov 21, 2012
    See OP:
    Yeh, this was going to be my first guess too. Instead of just "it seems straight" get out your measure and check it from the swing arm pivot.

    Is your front tyre installed in the right direction?

    Other than that, I might be looking at suspension. Wouldn't be the first time a triumph has come out of the box with the forks done wrong.
  9. Tyre pressures, mismatched tyres, faulty headstem bearings, scallop tyres, rear out of alignment...

    Why don't you bring it around & I'll take it for a test ride? :)
    • Like Like x 1
  10. From experience, usually if my isn't straight the bike would minutely serve either side when I let go of the bars. The front wheel is fitted in the correct direction.

    The bike has only done 6000km so I assume the tires are from the factory.
  11. They're both the original tyres Tony.
    • Like Like x 1
  12. I just had the same problem with my Breva, so I got a new tyre and had it balanced. The problem is still there. I haven't tried putting it in neutral though.
  13. I just had a closer look, there seems to be an uneven flat spot on the front tyre so I guess when the steering is free to its own motion the uneven flat spot would cause the steering to wobble. In fact I've never seen a flat strip(chicken strips) on the front wheel before....its scalloped like how jstava described it?
  14. They'd be good for fishtailing it :)
    Wouldn't leave it parked in the sun though :-(
  15. Burnouts would smell nice :)
    • Like Like x 1
  16. I guess that also explains the whining tyre noise at speed
  17. Some tread patterns produce this bar wobble as they wear out. Pilot powers were notorious for it. While you have your hand on the bars you're dampening the small input from the wear of the criss crossing tread pattern. If your headstem bearing is tight and axel too, tyre wear input is suspect!
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