Major oversteer issues

Started by maffiozo1234, January 12, 2023, 16:54

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maffiozo1234

Hi all,

Been really struggling with oversteer recently, Ive had a few moments in the last few months of compete loss of control of the car while going round roundabouts (In the UK).  Is there anything I can do to help reduce this oversteer.

I have recently replaced the rear tyres (They were past the indicators) and its felt 'better' but still had a few close calls on the edge of loss of control while driving at low speeds.

Would replacing suspension bushes etc lead to much of an improvement? Was also looking into getting an aftermarket front anti roll bar.

Anyone with more car setup experience then me here that is willing to give advise it greatly appreciated.

TIA

Gaz2405

I'd go in for a full alignment check first before replacing anything.
1zz turbo. Home built and home mapped.

Now 2zz turbo. Home built and home mapped

Build thread https://www.mr2roc.org/forum/index.php?topic=67004.0

cptspaulding

What were the conditions?

I've had it happen to me when wet & very cold. I put that down to tyres & conditions but if it's happening regularly...
Former owner 2003, 2zz conversion.

Joesson

I can see your a new member and we have not had any reports from you of ongoing problems.
"Approaching loss of control at low speed" is not symptomatic of this car. Something is obviously wrong.
Assuming the car is new to you there may be something very basic that is not correct.
Are the tyres, noting you have new rears, OE sizes?
Are all tyres inflated to OE spec?
I would do nothing until you have determined what is wrong and you have come to a good place to help with that diagnosis.

Carolyn

What tyres do you have?  What pressures are you running?
Perry Byrnes Memorial Award 2016, 2018.  Love this club. 
https://www.mr2roc.org/forum/index.php?topic=63866.0

Gaz mr-s

What  mph are you talking.  I had one that was nervous, particularly in the wet. I didn't get the chance to get it checked before it was too late. But this was around 45/50 mph & upwards.

If it's at lower roundabout speeds I'd be wondering about tyres. What's on the front & back? And as Joesson asks...sizes?

maffiozo1234

I've had the car for almost 2 years. The car has 205/45/17 on front and back. Conditions were wet and cold, it seems to feel more like it's worse on the right hand side then left (that's probably conformation bias as Turing right is more common in the uk)


The car has 35mm lowering springs (previous owner) front tyres are Avon zv7 at 32psi and rear are currently on my spare wheel set so not really sure what they are but it used to be on a set of Yokohama something running at 36psi.



maffiozo1234

Both of my full loss of control facing the wrong way moments were at about 20/25 mph

Gaz mr-s

General consensus on here is that the ride & handling is poor with 17's. And you have an 'all-square' set-up. If you don't know, the car is meant to have two or three sizes wider on the back...
Standard pressures are 26F 32R.  If you drop the front pressures it might help.

But personally if I bought the car with those sizes I'd be getting them off.

maffiozo1234

I have noticed that im yet to see anyone else with 17s. I put that down to people keeping closer to the oem setup. I wouldve thought that dropping the front pressure would increase the likelyhood of oversteer as there would be more grip at the front.

Im going to be getting the car back of having Avon zv7s front and back soon. Has anybody else had much experience with these tyres?

Gaz mr-s

Some of the younger guys on the f'book groups have 17's.  There are some on here have tried, & got rid of them.
If I were you I'd see if you can get a drive in closer to o/e sizes.

Look up tyre tests of zv7. They are not well regarded. They also have a tendency to perish in the tread grooves MUCH earlier than they should.

If you were determined to stick with the 17's, there is a much greater choice of good tyres available.

Be aware also that the stiffer springs present a greater force through the damper. Heavier 17" wheels & tyres won't help that.

Joesson

#11
Over sized wheels and tyres, same size front and rear, possibly also over pressurised. Perhaps three reasons for over steer. Likely highlighted by the recent change of rear tyres.

Petrus

Quote from: Joesson on January 12, 2023, 18:09Over sized wheels and tyres, same size front and rear, possibly also over pressurised. Perhaps three reasons for over steer.

Adding to this my limited knwledge of the english language has not enabled to figure out what the brand/type on the rear is.

I suggest the topic opnener first sorts out his data.
In parallel figure out wa¡hat the correct tyre pressure is for his tyres converting from the OEM pressures.

Ah and include the rim data like width and offset. The whole alligment can be mess even without taking the 35 mm lowering into account.


Call the midlife!

Apart from the obvious and previously discussed tyre issues I'd give your subframe a good looking at, it's not uncommon for them to rot and lead to a loosening of the rear end when the trailing arm's start to move around.
60% of the time it works everytime...

Ardent

#14
@maffiozo1234

All of the above.
A full breakdown of the tyres would help.
Inc age.
Your pressures in terms of oem are way off.
You should find a little sticker in the bottom of the glove box. That will show what should be on the car.

Any work done to the subframe?
If not correctly torqued up, can present as the car wanting to kill you.

Anyone local you can hook up with  to know how a stock 2 behaves.

Edit.
Cross Post with #13

McMr2

Could be a combination of a few things based on the thread so far. For what it's worth I had similar issues when I first got mine. Tyres and a 4 wheel alignment made the biggest difference.

Still catches me out in the wet if I haven't driven it for a while.

The other factor might be the diff. On an open diff the inner wheel will spin away the power on tight, low speed corners or roundabouts, but it's quite easy to get both rear wheels over-rotating in these cars (in the  wet at least).
2004 Silver. Stock(ish).

Dev

#16
 I would get that car on an alignment machine and then you will know what is happening. I am guessing negative toe as the car likes to go negative in the rear if it hasnt had an alignment for a very long time.
 
 In regards to 17 inch wheels I have them on my rears and they do not have any issues what so ever and are not in anyway a disadvantage in regards to handling and are lighter than the OEM 16" wheels.  However it is very easy to mess up with larger size aftermarket wheels if you choose the wrong ones along with limited tire selection. 
 Because they have a thiner profile they have an advantage of better response at the expense of less driver warning at the limit but that is not what is happening here.






maffiozo1234

The subframe has recently been repaired, was a little bit of rust which has been properly cut out and rebuilt.

I suspect that the alignment is also a big factor. I got all 4 aligned about 9 months ago but the car has had some work done on it since so will need to book that in pronto.

As far as tyres, i dont have the biggest budget for tyres at £150 each what are the best mid to higher range tyres people recommend from their experience (not too fussed about dry performance as its not getting tracked)

The tyre pressures im now very conflicted as ive had a group of people tell me that that is where they should be and know people are saying theyre too high

Thanks all for the input, will look to sort some of the things highlighted to me out



shnazzle

So many avenues of potential issues.
150 per tyre is a perfectly healthy budget for good tyres on the mr2 normally, but on 17s (especially in the odd sizes for the mr2) the choice is very limited. Falkens general work well.
Avons zv7 generally would get a thumbs up as well for tempered use.

Alignment is a biggie. But you know that. 

Then there's the sheer physics of running 17s; less profile, meaning less give in the tyres, transferring more of the load to your suspension. So if that's not up to scratch then that can have negative effects. 
They're likely wider than stock. Bigger/wider tyres in wet/cold = less grip. 
Ivll also wager you're no longer running stock stagger (rears wider than fronts), which also impacts handling. 


I'm in the "tried 17s, hated it, went back to stock" club. 
Included a 950mi trip on the 17s and it was absolutely fine on the long haul, but twisties and city driving? Doesn't hold an candle to 15/16 setup 
...neutiquam erro.

Gaz mr-s

Look up the web for the o/e pressures.....
It's a bit of a guess with 45% 17's though. In theory you've got a stiffer sidewall, so over 30psi in the fronts sounds totally wrong to me.

Look up tests of Hankook k125. They have done well. Good in dry & wet.  Available in correct o/e sizes. (edit....maybe not rear, new K135 maybe replacing it. Even better apparently. Not being made in 15" though. Camskill is usually best source. But shipping on tyres is getting pricey.

Your first decision needs to be whether to stay with the 17's though.  16 or 17" rear £100 or less.

JB21

Alignment is my bet. I find a millimeter or 2 toe in on the rear works best for stability on these cars. Front, you can go with a millimeter or 2 toe out to aid sharp turn in.

threepot

Concur with all above - get it aligned properly with someone with a proper idea of rear tracking - not many places do this so tend to stab in the dark. Seeing as its had the rear subframe etc messed about with it is probably geometry being the main culprit. Someone I know had his done at quickfit once and it was tracked backwards thus I took it back and had to give them the "half a clue" they were missing.

I suspect that issue is then amplified by:-

I've not drove an MR2 on 17", but all the other FWD cars with 14" or 15" OEM sizes of customers I've drove always tram track and steer weird. The bigger wheel dominates the rotary forces more. 17" will require lower pressure than the cars OEM spec. 17" will make the handling weird. 17" makes your tyres more expensive...... it is all because the tyre sidewall is smaller, the mass is concentrated to the outer of the circle, the rolling radius is typically bigger.

Putting ill suited wheels on a fwd hatch is far more forgiving than putting them on light little rear engine car. They are pretty twitchy in the wet at the best of times to start with.

cptspaulding

Are you absolutely convinced you want to stay with 17" wheels?

A set of stock wheels can be picked up pretty cheap. Possibly even with some decent rubber still on them, you might get lucky. Have a look around on here or put up a wanted ad on here or on FB pages.

That way you'll have the car back to how it was designed with correct stagger.

& + alignment, + tyre pressures as others have said.
Former owner 2003, 2zz conversion.

maffiozo1234

I have no reasoning to stay on 17s. I am yet to change/undo and of the stuff the previous owner has done to the car. Currently looking or a set of OEM wheels( if anybody has any) to bring the car closer to as it was.

Quote from: cptspaulding on January 13, 2023, 09:53Are you absolutely convinced you want to stay with 17" wheels?

A set of stock wheels can be picked up pretty cheap. Possibly even with some decent rubber still on them, you might get lucky. Have a look around on here or put up a wanted ad on here or on FB pages.

That way you'll have the car back to how it was designed with correct stagger.

& + alignment, + tyre pressures as others have said.

J88TEO

I have 2 sets of OEM wheels - PFL and FL ones.