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max748

Joined:

May 12

Posts: 41

max748 says:

front end

changed my front tyre a while back on my ducati 748. derestricted it at the same time.

when i reach 160+km/h (hadn't been able to do before derestriction) the front end shakes like crazy. i read a few articles that describe that the bike vibrates and some people find it uncomfortable at speed but i feel as though this is more than a vibration, rather violent shaking.

i first found the problem on a high speed bend. needless to say i had a little moment. but i rode on.

could it be something as simple as an impropperly balanced wheel or does anyone know of other possible causes?

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  • Posted 2 years ago (25 November 2012 23:43)

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jaffa90

Joined:

Mar 09

Posts: 9034

jaffa90 says:

front end

Are both tyres fitted properly and balanced?

When was the last m.o.t. done?

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AdieR

Joined:

Apr 08

Posts: 3042

AdieR says:

160km/h

roughly 100mph by my calculations.

Some bikes are prone to shake at speed, with different tyres accentuating or reducing it.

What tyres have you got on, pressures, and what condition are they in?

Balancing may be a factor, but often that highlights itself at a far lower speed than in your case.

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smidget

Joined:

Nov 07

Posts: 2432

smidget says:

There

are multitudes of reasons why your bike has a vibration / shake at speed.

As has been mentioned, tyre pressures, are they in good condition and mounted on the rims properly, do they match?

Are the suspension units front and rearin good condition and setup correctly for the bike and your weight?

Are the rear shock bushes in good condition?

Are the steering head bearings in good condition and set correctly?

Are wheel bearings in good condition ans set correctly and lubricated property?

Are the swinging arm bearings in good condition and set correctly?

Are all mechanical fastenings torqued to the manufacturers specifications.

And so the check list continues until all possible reasons have been eliminated one by one and in logical order.

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eatcs01

Joined:

Aug 02

Posts: 3287

eatcs01 says:

748 wibbles

Sounds like the front wheel is out of balance.

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max748

Joined:

May 12

Posts: 41

max748 says:

my tyres

mischeline pilot power, only around 400kms on the front, back just reached wear indicator bars (havn't ridden since).

i checked, the pressure was 5.5psi short of recomendation. then again, it's gotten bloodey cold in the black forrest since i last rode. havn't the wether to test it (especially not with almost bald reer).

all torqued to manufacturer's spec, bearings are good.

last TUV was done in June. (about 3000km ridden since)

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AdieR

Joined:

Apr 08

Posts: 3042

AdieR says:

Does your

bike have a steering damper fitted?

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eatcs01

Joined:

Aug 02

Posts: 3287

eatcs01 says:

wobbles

The wheel is out of balance. It's easy enough to check the front wheel. Get the wheel in the air, with the calipers REMOVED.
Spin the wheel. Let it stop of it's own accord. Mark the bottom of the tyre when it's stopped (chalk would be ideal). Then spin the wheel again. If it stops with the chalk mark at or near the bottom, then that bit is heavier than the rest. You may need to spin and mark it 3 or 4 times.


Not forgetting, that the REAR wheel can also make things shake like mad if it's out of balance.

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Dabbsy

Joined:

Aug 02

Posts: 500

Dabbsy says:

tyres

At only 400kms old the front tyre will still have a good, curved profile, but if the rear has now worn down to the wear indicators its profile will be squared off and this mismatch is enough to set up this instability on a fast bend that then feeds through to the front end. A badly balanced wheel will be more of a vibration than shaking.

Change that rear tyre, check your pressures and the bike will be stable again.

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max748

Joined:

May 12

Posts: 41

max748 says:

rear pretty evenly worn

the rear is worn evenly to the edge, i live where the twisties are, so i'm rarely going straight.

but it would shake on straights too.

i do have the stock steering damper equiped.

as mentioned before, the front was underpressure and i have redone pressures. yet to test, have to wat til next year.

i'll have a look at balancing when i have modified my new constands centre stand/lift to fit my 748 (they dont come for my bike)

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max748

Joined:

May 12

Posts: 41

max748 says:

oh, and...

i'm replacing my rear tyre over the winter too (kind of have to, already got booked for the bald frond before i changed it)

so i'm hoping the problem is gone by the end of all my services.

 

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