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Severe Vibrations From 120Kmph (70Mph) And Up


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#21 jarno

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Posted 11 May 2020 - 11:34 AM

So i just swapped my rear wheels with the wheels from a mate of mine. Theres only at 110kph slight shimmy but after 120 its completely gone. Can drive 150 kph super stable now.... Guess my rear tyres, and my drift wheels/tyres are very badly balanced or tyres are fucked. I will have a tyre specialist shop inspect my tyres. Wheels are 3 months old, tyres about 9 months. Very strange.

 

Will report back when its done. At least ill put the diff swap on hold till the tyres are sorted


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#22 carl s

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Posted 11 May 2020 - 11:57 AM

You could have tyre run-out,  I had this last year when I switched wheels but kept the tyres from my old wheels.  On acceleration it would pull left, decelerate it would pull right. If I switched tyres side to side it did the opposite!  There are different types of run out that affect different things,  Every tyre I think has a bit of this the coloured marks on a tyre when new tell a good tyre fitter where on the wheel & how to fit & balance the tyre I'm told. Mine was Radial runout I think,  sounds like yours might be lateral?

 

(from Google)

Tire run-out
Featured snippet from the web
Radial runout is where the radius of the tire is not consistent from the wheel midpoint to any point on the rim. ... Lateral runout is the amount of sideways motion or the amount of “wobble” in a wheel or tire as it rotates which feels like dynamic imbalance problem.

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mk1 1991 Eunos with RS NB drivetrain: https://www.mx5nutz....howtopic=322586

ex - mk3 2006 2.0 sport

ex - mk2 1999 1.8is JRSC


#23 dadbif

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Posted 11 May 2020 - 04:11 PM

Glad you’ve sorted it 👍
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#24 Quinvy

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Posted 11 May 2020 - 04:14 PM

It had to be something simple. Well done.
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#25 jarno

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Posted 11 May 2020 - 08:38 PM

 

You could have tyre run-out,  I had this last year when I switched wheels but kept the tyres from my old wheels.  On acceleration it would pull left, decelerate it would pull right. If I switched tyres side to side it did the opposite!  There are different types of run out that affect different things,  Every tyre I think has a bit of this the coloured marks on a tyre when new tell a good tyre fitter where on the wheel & how to fit & balance the tyre I'm told. Mine was Radial runout I think,  sounds like yours might be lateral?

 

(from Google)

Tire run-out
Featured snippet from the web
Radial runout is where the radius of the tire is not consistent from the wheel midpoint to any point on the rim. ... Lateral runout is the amount of sideways motion or the amount of “wobble” in a wheel or tire as it rotates which feels like dynamic imbalance problem.

 

Been watching some videos on this tire runout (tire out of round). Found some videos of people measuring the tire with a dial indicator and classifying the wheel as "bad" while it doesnt even show it on the video that much. If id use that as a reference i would classify my left right tire as "bad" aswell and my left rear as "very bad".

 

Been to the garage today, i value their opinion also because the website i bought the tires from want some experts opinion along with the warranty claim (understandably).

They have time coming Saturday.


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#26 carl s

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Posted 11 May 2020 - 08:55 PM

Well done you've definitely made some progress, I remember mine was very frustrating but ultimately it fixed my problem. I think the MX5 is very sensitive to wheel/tyre differences because the powerplant frame joins the front & rear of the car making it harder to track down as noises/vibrations transmit through it.


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mk1 1991 Eunos with RS NB drivetrain: https://www.mx5nutz....howtopic=322586

ex - mk3 2006 2.0 sport

ex - mk2 1999 1.8is JRSC


#27 jarno

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Posted 14 May 2020 - 06:47 PM

Ok so, this story got a little plot twist at the end. Where i thought i was gonna have to buy new tires, the shop told me they took off the tires, rotated them 90degree and put them back on with a shit load of grease and pump them up very hard. The tire runout got alot less they told me. I took it for a drive and the car is steady as a rock all the way up to 150kmph. Holy crap does that feel good after all this troubleshooting haha
Thanks for the help everyone :)


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#28 carl s

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Posted 14 May 2020 - 08:19 PM

That's great to hear, sounds like you had a similar issue to me last year but manifesting itself in a different way

 

Apparently it's to do with these little spots on the tyre, the red one is the high point of the tyre, yellow spot is another balance dots that apparently has to be aligned with the the valve. The lines are the runout how far away from the centre of the tyre is the centre of gravity. It's a whole science that most of us are completely unaware of !

 

red_dot2.JPG

 

Tyre_runout_machine.jpg


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mk1 1991 Eunos with RS NB drivetrain: https://www.mx5nutz....howtopic=322586

ex - mk3 2006 2.0 sport

ex - mk2 1999 1.8is JRSC


#29 jarno

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Posted 14 May 2020 - 08:34 PM

Ye its crazy how much variables there are if you think about it. Its not as easy as it looks haha
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#30 atlex

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Posted 16 May 2020 - 02:26 PM

Yeah those dots do mean something. Also if you're hard on your wheels you can spin the wheel inside the tyre and put it out of balance.


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#31 jarno

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Posted 16 May 2020 - 03:05 PM

if you're hard on your wheels you can spin the wheel inside the tyre and put it out of balance.


Haha that might be it then
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