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VERY unstable at speed- any ideas? URGENT HELP
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TOPIC: VERY unstable at speed- any ideas? URGENT HELP
#7587
VERY unstable at speed- any ideas? URGENT HELP 12 Years, 8 Months ago Karma: 29
Over the last two weeks, my '91 MK2 SW20 has developed a severe wandering at speed over 60mph, its like the hand of god grabbing the back of the car and shifting it from side to side, worse when I change gear/clutch depression. Its got so bad, I'm going to keep it off the road until I fix it. Until 10 days ago, straight line stabilty at very high speed was better than any car I've ever driven!

Wheel bearings and steering geometry/tracking are fine. Recent changes: New rear shocks, EBC discs/yellowstuff pads, power rack, Polyurethane bushes fitted Dec 2009. Have checked all suspension linkages and they seem tight, no play.

I've just ordered 2 REAR Anti Roll Bar Drop Link Rods, in the hope that'll fix it (its going to be costly to guess and replace like this). Had rear tyre pressure difference, corrected that, which improved things a little, but its still wierd and dangerous.

I have a hunch that the power rack might not be switching off at speed, but that's a wild guess.

Anyone else had this problem?
Briweekes
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#7588
Re:VERY unstable at speed- any ideas? URGENT HELP 12 Years, 8 Months ago Karma: 29
I'm going to follow the tips I've spotted on:

www.mr2oc.co.uk/component/jmrphpbb/topic/106418.html?f=41

Looks a real possibility, but let me know if any of you ahd same trouble. Cheers
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#7589
Re:VERY unstable at speed- any ideas? URGENT HELP 12 Years, 8 Months ago Karma: 6
Hey mate, you say its the back end twitching at speed? and its the rear shocks you've recently replaced? I'd start there. Check for any bushes that may have fallen out or fallen apart after the change of shocks. I think the power steering should become heavier at high speed, you dont want the wheel staying light as you increase speed. Def go through all the suspension parts, from one side to the other.
Good Luck

PS hopefully you havent fitted a spoiler that resembles an ironing board, might be your problem
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#7608
Re:VERY unstable at speed- any ideas? URGENT HELP 12 Years, 8 Months ago Karma: 328
Do a full nut and bolt check on everything you touched when doing the parts change, in fact when you do any work on vital components on your car alway do this set and as you check each item mark it with tipex or paint to know you have double checked it.

This is what I would be looking at first.= in order of preference.

Nut and bolt check.
Sticking brake caliper.
Four wheel alignment.


Then start looking at the items you mentioned, drop links will make a clunking noise when gone, ARB will thud when they are going. After you have done that I would then get a mechanic to go over it on a ramp to make sure its safe.

I had a similar issue, its was down to the front shocks and wheel alignment.

Good luck with it.
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#7611
Re:VERY unstable at speed- any ideas? URGENT HELP 12 Years, 8 Months ago Karma: 314
It's not something silly like loose wheel nuts is it?
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#7620
Re:VERY unstable at speed- any ideas? URGENT HELP 12 Years, 8 Months ago Karma: 25
Track rod end?
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#7641
Re:VERY unstable at speed- any ideas? URGENT HELP 12 Years, 8 Months ago Karma: 29
Thanks for your suggestions.

Have done complete nut/bolt check, bearings, shocker tops, steering rack brackets. All using a torque wrench. Ball joints seem ok. I used a large bar to check. Calipers all ok. It passed the NCT mid Jan 2010.

I'm going to go for another spin, but nothing seems to have changed.

The only thing I can think of, is the rear Anti roll bar, the bit where the horizontal part bolts to the chassis (those U brackets and rubnber bushes), it seems to slide freely thru the bushes, whehn its jacked up via the crossmember. I've not changed these bushes. BUT about 3 weeks ago I sprayed all the bushes with WD40 to get rid of an annoying suspension squeek at low speed (bit of a co-incidence as that's when the back swaying started). These U brackes seem to be bolted to the max.

The plot continues (annoyingly), all suggestions welcome

Cheers
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#7990
Re:VERY unstable at speed- any ideas? URGENT HELP 12 Years, 7 Months ago Karma: 29
Fitted polyurethane bushes to rear AR bar, and new sway bar links, all torqued up correctly. Now I'm really foxed. Am wondering if its a rack prob (eg power steering not swtching off at high speed (erm I'm talking 60mph!). The car was ok for 120++ and was a straight as a die on the Mway (that was only a few weeks ago).

Any more ideas??
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#8002
Re:VERY unstable at speed- any ideas? URGENT HELP 12 Years, 7 Months ago Karma: 102
It's definitely not your wheel allignment?
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#8012
Re:VERY unstable at speed- any ideas? URGENT HELP 12 Years, 7 Months ago Karma: 29
nope, I have the superb Gunsons Trackrite tool, and its within the tolerance level. Am wondering if I have cracked something, the potholes are pretty bad up my local lanes. Wierd that the car is fine under 60mph, even driving hard.

Does anybody know about a spped sensor connection to the power rack??
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#8015
Re:VERY unstable at speed- any ideas? URGENT HELP 12 Years, 7 Months ago Karma: 29
spped= speed
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#8408
Re:VERY unstable at speed- any ideas? URGENT HELP 12 Years, 7 Months ago Karma: 29
Check this out (from a NZ website about a 1990 MR2 www.carsurvey.org/reviews/toyota/mr2/r105960/comments/

"The biggest thing though - was that the hairline cracks developed in the chassis near the front sway bar mounts! This did constitute a WOF failure, So always check here if you are thinking about buying one!! I had it fixed by a chassis repair specialist who informed me that this was a common problem for mk2 MR2's - LTSA have repair guidelines for them (The local Toyota service centre had no idea about it when I approached them though...) Black painted patches on the underside will indicate that the chassis has either been strengthened - or simply welded up, meaning that it may only be a matter of time before it cracks again"

Guess what, I can see the OSF AR bar mount place on my chassis has been welded: will check if its cracked, Mmm
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#8536
Re:VERY unstable at speed- any ideas? URGENT HELP 12 Years, 7 Months ago  
poer sterring not turning off is a good shout.

what tyres are you running , and when was the last time these where balanced.
blackice2

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#8543
Re:VERY unstable at speed- any ideas? URGENT HELP 12 Years, 7 Months ago Karma: 29
N.S. O.S
Front Nanking 235/40R17 Avon ZZ1 235/40ZR17
Rear Ventus 255/45 ZR17 Nanking 255/45 R17

Wheels Hamann PG2 17" (BMW, and I have adaptors to Mr2). Bought the car with that lot fitted, a right mish-mash. Wheels look really pukka though.

Been checking the rear sus geometry again, and its off the scale with too much toe-in (that's after fitting nice n tight 17mm polyurethane AR bushes). I have a full set of PU-thane bushes for the rear and will hang back adjusting the sus settings til that's all fitted. Rear camber visibly negative.

Front AR tie bars seem weedy and look almost bent. have replacement new ones ready to fit, and they look much more beefy (see how ling the strut tie bar brackets last with those).

OSF bearing seems a little duff, replacing that at the weekend.
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#8545
Re:VERY unstable at speed- any ideas? URGENT HELP 12 Years, 7 Months ago  
brianweekes wrote:
N.S. O.S
Front Nanking 235/40R17 Avon ZZ1 235/40ZR17
Rear Ventus 255/45 ZR17 Nanking 255/45 R17

Wheels Hamann PG2 17" (BMW, and I have adaptors to Mr2). Bought the car with that lot fitted, a right mish-mash. Wheels look really pukka though.

Been checking the rear sus geometry again, and its off the scale with too much toe-in (that's after fitting nice n tight 17mm polyurethane AR bushes). I have a full set of PU-thane bushes for the rear and will hang back adjusting the sus settings til that's all fitted. Rear camber visibly negative.

Front AR tie bars seem weedy and look almost bent. have replacement new ones ready to fit, and they look much more beefy (see how ling the strut tie bar brackets last with those).

OSF bearing seems a little duff, replacing that at the weekend.



That will be some of your problem , different tyres , each tyre has it's own sidewall strenght , and as soon as you put them under alot of pressure the back end will if twitchy .
blackice2

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#8551
Re:VERY unstable at speed- any ideas? URGENT HELP 12 Years, 7 Months ago Karma: 328
brianweekes wrote:
Been checking the rear sus geometry again, and its off the scale with too much toe-in

From this site: www.torqueracing.com/mr2suspension.php

I adjusted mine and very quickly readjusted it back to OEM spec.

Rear Toe-in/Toe-out

Toe-in Toe-in at the rear make's your car more sticky at the back and easier to drive This may stabilize your car. But be careful, this is a very sensitive adjustment. E.g. 0˚– -3.5˚

Toe-out Rear Toe-out makes the rear of your car very instable. This adjustment is never used and we advise you to not use it. E.g. +1˚

Neutral-Toe For a neutral feeling adjust less toe-in. The car will be slightly faster and more efficient. But the car may stick less in the back and that could cause slower laptimes. E.g. 0˚
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#10293
Re:VERY unstable at speed- any ideas? URGENT HELP 12 Years, 6 Months ago Karma: 29
PROBLEM FIXED !!!! WEY HEY

Replaced front and rear AR tie bars, and spent this weekend removing the rear suspension and changing to Superfex Urethane bushes, all torqued up nicely.

I'm delighted with the result, the car is totally different, its even good over dodgy back roads, cornering is as good as it gets, and straight line speed fabulous. I was really worried I had a cracked chassis, so am over the moon.

They should sell cars with Urethan bushes as standard, its the dogs bollx
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#10294
Re:VERY unstable at speed- any ideas? URGENT HELP 12 Years, 6 Months ago Karma: 314
Great stuff mate, glad you got it resolved
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#67477
Re:VERY unstable at speed- any ideas? URGENT HELP 8 Years, 5 Months ago Karma: 29
Well 4 years later, the old problem has come back.

I suppose those Urethane bushes are worn out, I've done about 5,000 miles, thats all. Seriously thinking about fitting a Rev 3 rear crossmember and suspension parts now, more beefy than rev 1. I've spent bundles on this car suspension and steering to get it right, I'm not at all impressed with the rev 1 Mk2 MR2 in this respect.

70mph and above its dangerous when overtaking on the motorway, oversteer and sways the other way, like the car is going to turn upside down. have checked all the bolt torque, its recently passed the NCT and I've just had the laser wheel alignment and fitted roll centre adjusters, in the hope it would help.

Hmm, not happy. Wonder what the racing boys do with their Mk2's to change from the weedy stick parts to make it fit for purpose?

B
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#67486
Re:VERY unstable at speed- any ideas? URGENT HELP 8 Years, 5 Months ago Karma: 47
Racing boys tend to completely change to a different suspension. One of the best available is the fully adjustable TEIN Super Street kit like I have. Very stable at very high speeds. More info here: www.tein.com/products/super_street_with_pillowball.html

Only Con's is expense and the lower firmer ride. In the countryside this could prove tiresome but if you live in an Urban area This might be the choice for you!
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#67491
Re:VERY unstable at speed- any ideas? URGENT HELP 8 Years, 5 Months ago Karma: 154
Yeah I was going to ask what suspension set up you have?
If it's cheap coilovers it will have a negative effect on handling and will also stress other parts much more, e.g. bushings and joints etc.
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#67493
Re: VERY unstable at speed- any ideas? URGENT HELP 8 Years, 5 Months ago Karma: 141
I have Tein Type Flex which are good but expensive.

I have read good reports on BC Racing coilovers.

Good performance, comfortable on road and a reasonable price.

www.bc-racing.co.uk/applications/toyota-...2-sw20-21-90-99.html
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#67494
Re:VERY unstable at speed- any ideas? URGENT HELP 8 Years, 5 Months ago Karma: 29
Infamous wrote:
Yeah I was going to ask what suspension set up you have?
If it's cheap coilovers it will have a negative effect on handling and will also stress other parts much more, e.g. bushings and joints etc.


My current setup on this Rev 1 Mk 2 is:

Superfex Polyurethane bushes
Uprated adjustable rear AR Bar- Whiteline
Whiteline lateral locks
Whiteline adjustable rear drop links
FK Coilovers (€450)- hight adjustable, but not damping rate adjustable
TRD rear topmounts, pillowball adjustable front topmounts
TechToy tuning Roll centre adjusters all round
Brand new ball joints front and rear
Brand new front track rod ends

Lowered to max setting

Right now I'm thinking the Urethane bushes life isn't that great. My powersteering electric motor seems to be running a lot longer than normal, wondering if that could be it. Right now its guesswork
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Last Edit: 2014/06/25 21:47 By Briweekes.
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#67510
Re:VERY unstable at speed- any ideas? URGENT HELP 8 Years, 5 Months ago Karma: 154
I'd consider upgrading your coilovers if you are looking for better handling etc.
But then you have to weigh up day to day road comfort with perfomance and handling, finding a balance between the two can be difficult.
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#67513
Re:VERY unstable at speed- any ideas? URGENT HELP 8 Years, 5 Months ago Karma: 47
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#67519
Re:VERY unstable at speed- any ideas? URGENT HELP 8 Years, 5 Months ago Karma: 29
Thanks Cashy, I'll PM you right away
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#67521
Re:VERY unstable at speed- any ideas? URGENT HELP 8 Years, 5 Months ago Karma: 29
I have s/s teins in my track car. Seem very good but have to test and set em up for track yet.
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#67523
Re: VERY unstable at speed- any ideas? URGENT HELP 8 Years, 5 Months ago Karma: 328
Hey Brian, I would be looking to get the car up on a ramp and have it checked out.

Even if the suspension was shot the likely hood of it causing the instability is slim IMO. I would look at the geometry set up first specifically look at the rear toe in as this can have a major role in how the car behaves when turning and can infact make the car feel unstable.

Are you aware of the issues with the rear sub frames and trailing arms where the nut inside the sub frame breaks and that can give an unstable feeling also.
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#67547
Re: VERY unstable at speed- any ideas? URGENT HELP 8 Years, 5 Months ago Karma: 5
See you've uprated your rear arb only-? On a rev1 rear end. Surely that would make it very tail happy? The trd bars are stiffer at the front to quiet down the rear end at the limit.
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#67587
Re: VERY unstable at speed- any ideas? URGENT HELP 8 Years, 5 Months ago Karma: 29
Agree I should change the stock front ARB and upgrade, also the tie bars. All drop links upgraded. Looking at BC racing coilovers now
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Last Edit: 2014/06/29 21:46 By Briweekes.
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