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philehidiot

Joined:

Feb 09

Posts: 4781

philehidiot says:

Front wheel wobble

Eh up.

When I start to hit around 80mph, the front wheel becomes rather unstable and starts wobbling... Happened today during an overtake going from 65 to 80 on a dual carriageway whilst I was crossing the white line. The word "clenched" describes it well.

Is this likely to be a wheel balance issue, suspension issue or a result of having a slightly bigger rear tyre than is specified for the bike? It's not necessarily associated with acceleration, more just hitting that speed.

Cheers.

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  • Posted 6 years ago (09 September 2009 18:54)

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philehidiot

Joined:

Feb 09

Posts: 4781

philehidiot says:

a

DR-Z400SM. 4 years old. Got it with just over 1K miles on a couple of months ago - done about 2K miles in that time.

Only mod is the rear tyre.

Recent work - New tyres (the old ones were so dangerously bad I never dared go fast enough to say whether the wobble was there before). Tyres are well bedded in now and certainly not worn.

Other work - scottoiler, alarm, seat altered.

I ask about suspension as I'm 9 stone - could it be I'm so light I'm not pushing the front down so it's lifting at speed?

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philehidiot

Joined:

Feb 09

Posts: 4781

philehidiot says:

Lol

Loving the PS.

The tyres weren't worn, but they wouldn't grip - they looked like they'd had 1k miles put on them but they were just absolutely shoddy. Not sure if it was a combo of really poor OE tyres and that they were old as well as probably having been stood for a while and probs not lifted off the floor or moved around.

I'd say the mileage is correct. The general appearance is one of low mileage summer bike. It won't be getting such an easy life with me.

Thinking it might be best to drop it into the dealer to have them look over it as frankly, I don't trust myself to not cock it up royally.

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m1ks

Joined:

Apr 09

Posts: 908

m1ks says:

.

DRZ? Crosser?

If so these are naturally light at the front and get skittish at high speeds, especially if you're on knobblies, they're notoriously shite on tarmac.
However, get someone to lift the front and grip the wheel at 1 o'clock and 7 o'clock firmly, give it a wiggle, it shouldn't have any free movement, (don't confuse bearing slop with the movement of the forks / yokes whilst being held airborne), while there grab the forks and give em a heave, again tey shouldn't move, if so your head bearings need adjusting or replacing.
Oversizing the rear tyre can affect the handling but generally cornering rather than straight line, again if knobblies doesn't matter what you fit, it'll affect corners and straight line, better fitting road or dual purpose.
 

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smoto5

Joined:

Mar 09

Posts: 4548

smoto5 says:

Apart from

the things mentioned above, some other things to check ( I presume its still running on the 17 inch supermoto wheels by the way) Wheel alignment, although there are usually marks on the swinging arm and adjusters to keep rear wheel aligned correctly these are not always 100% accurate, a straight edge (long piece of wood/spirit level/ length of angle iron)  can be used to confirm alignment, when it is touching one side of rear tyre at front and rear, then when bars are straight front wheel should be in line with this, allowing for thinner front tyre. Are tyre pressures correct, you may able to lower it slightly due to lighter weight? Are you sitting at front of seat, this is quite important due to bolt upright seating position, easy to slip back due to acceleration and flat seat! It possible the forks may need the pressure released, long travel forks like those can pump up after a while, may be bleed screws to loosen on top of forks (may also be damping adjuster there too) If there are damping adjusters, you may be able to back those off a little, especially the compresssion adjusters. As m1ks says they are a little more skittish than a heavier bike, and less stable at speed, although it shouldn't get out of hand! 

[This Reply has been modified by the Author]

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Yellowninja600

Joined:

Nov 07

Posts: 540

Call me stupid...

But one little other thing to check would be the 'spokes'...

Make sure that they are all tight. There's about a million things (as already mentioned) that could be the source of your issues but start with the basics and work towards the confusing complex things as you go otherwise you'll fry your brain and give up.

Spokes, tyres and play in the front forks etc. Check rear wheel alignment as mentioned as strangely the back effects the front and vice versa (had this on the ZX6R which has less than accurate adjusters on the back). Could also be loosness in the rear swingarm or suspension setup. Can be a multitude of things.

Best to do is get the bike of the ground and supported in the middle (like a crosser on a stand) and then pull and prod front and back until something moves and then look deeper into it.

It could also have been 'strange winds'??? Had that one myself but you'll know better with regards your situation. Thing is now that you have witnessed it you will be looking out for it all the time.... :lol:

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Vortex52

Joined:

Oct 09

Posts: 40

Vortex52 says:

Front wheel wobble

My Yamaha X-Max 250 has the same problem as it wobbles when desacelerating from 60 to 35 mph.
Took to the dealer and they changed the steering bearings and the problem still occurs.
Now i have seem a possible cause to be the rear tyre which is approching the time to change it and maybe it will resolve the problem! is that possible?

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GIDRIDER

Joined:

Nov 09

Posts: 29

GIDRIDER says:

front wheel wobble

:dopeyhmmmm:sounds to me to be bike moving along at it's upper speed and moving about as you go over white lines,any bike i've ridden hard at top end speeds and crossing white lines(especially in wet ) causes the exact same clenching as you are talking about.What's the top speed of your bike 95?ish:ph43r:

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