Vibration

Technical advice Q&A
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AshM
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Location: Edinburgh, Scotland
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#1 Vibration

Post by AshM » Fri Jun 08, 2018 5:19 pm

On the long drive down to Worcester from Edinburgh for XK70 tomorrow the car has a new dynamic - vibration.

A noticeable vibration from the rear of the car. Can feel it through the seat up to about 55mph and the rear of the car feels ‘lumpy’. Sorry, not very descriptive.

This is the first long drive since winter projects. One of which was the IRS off and rebuilt.

So one idea, I may have bolted the prop shaft onto a different position on the IRS flange which may have moved it out of balance. Would this cause said vibration?

Also, I had a very badly unbalanced wheel on the front last year (which no one seems able to balance). So have moved it to the rear. Would a bad wheel cause that much noticeable vibration?

Any other thoughts or ideas?

Cheers
Ash
Series 2 FHC 1970
1R 20607

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politeperson
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#2 Re: Vibration

Post by politeperson » Fri Jun 08, 2018 6:02 pm

Well, its probably a bit late in the day and a bit obvious, but it might be something really simple.

Why not swap your wheels around front to back. You can do that this evening.

Also, reproduction spinners have caused all sorts of issues with my car, check the spinners are tight.

You never know, the solution might be £0 pounds.
James

L.J.K. Setright was right.
"You just cant beat a good E-type"

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Mark Gordon
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#3 Re: Vibration

Post by Mark Gordon » Fri Jun 08, 2018 7:29 pm

Another possibility is that the tires have developed a flat spot if the car sat without moving over the winter months. If that's the case, they may self-correct after a few long runs at speed to heat them up.
Mark

67 OTS 1E14988, 2002 VDP

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christopher storey
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#4 Re: Vibration

Post by christopher storey » Fri Jun 08, 2018 9:35 pm

If you have a wheel which it has been impossible to balance, this is the most likely source of the vibration, particularly if it is not constant but comes and goes at various speeds. The other less palatable possibilities are prop shaft imbalance ( not very likely as this is almost always throttle sensitive ) or drive shaft imbalance

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AshM
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#5 Re: Vibration

Post by AshM » Fri Jun 08, 2018 10:40 pm

Going to try a wheel swap in the morning.

Cheers
Ash
Series 2 FHC 1970
1R 20607

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Gfhug
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#6 Re: Vibration

Post by Gfhug » Mon Jun 11, 2018 7:42 am

Ash, did you swap for the spare and if so how did you get on?
Sorry we didn't get to properly meet on Saturday, but at least we did manage to briefly say hello. Hope you had a good drive home, maybe you're still en route.

Cheers

Geoff
S2 FHC Light Blue

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AshM
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#7 Re: Vibration

Post by AshM » Mon Jun 11, 2018 8:54 pm

Hi Geoff,

Great to meet, albeit briefly. Next time a longer chance to chat hopefully.

Wheel swap definitely helped but not completely. Going to try a couple of alternative propshaft to IRS flange positions.

But, importantly, 674 miles on the 5 day adventure and the car did not miss a beat.

cheers
Ash
Series 2 FHC 1970
1R 20607

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Gfhug
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#8 Re: Vibration

Post by Gfhug » Tue Jun 12, 2018 7:33 am

Ash, you said no-one had been able to balance the one wheel, but were they using a modern wheel balancing machine without cones to attach wire wheels. http://www.fossewayperformance.co.uk/wi ... ncing-kit/
It's a recurrent problem as wires don't get properly fitted to these machine and can give serious misbalancing. I've had success with simple bubble level balancing when having new tyres fitted others prefer to use adapter cones onto modern balancing machines.
It'll all help to make your car as smooth to drive as it looks

Geoff
S2 FHC Light Blue

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