rear end unstable

[cartledge_uk]

So I drove the supercharger today properly for the first time, had the geometry set up and the rear has issues.

The rear wants to step out at all times and just feels loose. With the supercharger on and under load in a straight line I was at an angle of about 45degrees. disconected the charger and it still wants to break loose.

Anyone else had similar issues?

[oukie]

Silly question Tim but you checked the rear ball joints ?

Mine are slightly worn (ie have minnor play) and I find I can step the back out a bit to easy even in the dry with Yoko's

Ive ordered a pair as thats about all I could find that wasn't 100%

Chris

[cartledge_uk]

Silly question Tim but you checked the rear ball joints ?

Mine are slightly worn (ie have minnor play) and I find I can step the back out a bit to easy even in the dry with Yoko's

Ive ordered a pair as thats about all I could find that wasn't 100%

Chris

Everything is new on the rear end, ball joints, bushes, tie bars, arb, suspension, drop links

Currently checking for loose bolts, hopefully i'll find some

[jon_st205]

Does it crab under braking or just under power? Could be a CV joint if open diff?

[Finn]

Just a guess or two:
- tightened the control arm and strut rod bolts with the car weight on?
- wheel alignment OK?
- motor mounts?

[SuperRedMR2]

What are your rear tyres like Tim?

[PW@Woodsport]

Tim i've come across this before and it was on a Mk1 that someone had mixed and matched Mk1a and Mk1b rear suspension parts.

If you have used Mk1a hubs with Mk1b suspension triangle or vice versa it will bump steer unbelievably badly on the move but look straight when static.

Could be anything though, that is just one of the more extreme causes. For info what i've described causes crazy toe in with very little spring compression which gives the rear a wild fishtail.

It could just as easily be a loose nut/bolt.

[sideways247]

My mr2 tends to step out alot but only the wet, bit unstable too.
but i put it down to the tyres. which are maxxis 205/45/15

[PW@Woodsport]

I think what Tim is describing appears to be more than the normal Mk1 tail happiness.

[cartledge_uk]

I think what Tim is describing appears to be more than the normal Mk1 tail happiness.

45degree angle at 20mph with a thottle blip

I think you may have it Paul, i've no idea what hubs/suspension parts etc are on the car I have 1a and 1b lying around. Is there anyway to tell by looking?

[cartledge_uk]

Does it crab under braking or just under power? Could be a CV joint if open diff?

Dosconected the charger and it was still bad, just generally at all running speed and types.

Have played with the geo and got it drivable (ie it doesnt want to kill me) and we'll see what happens

[cartledge_uk]

Just a guess or two:
- tightened the control arm and strut rod bolts with the car weight on?
- wheel alignment OK?
- motor mounts?

Thanks for your reply. I went back and checked the mounts and bolts and they were ok. The alignment had just been done too, although it felt more planted before they did it

[PW@Woodsport]

Tim a quick way to check if the suspension parts have been mixed up is by jacking the whole rear end up, if the rear wheels (or one of them) deflect wildly toe in or toe out then it must have mismatched parts fitted.

They appear to be straight with the cars weight on them, i've seen it a few times now when people presume a Mk1 part is a Mk1 part. If your rear subframes had been changed the crossmember bolt won't be in the right place, so have a quick look at that, unless someone cut them off and rewelded the tabs in a different place. Check your rear hubs match each other, in particular the rear adjustable track rod mounting point on the hub and the track rod itself.

I've had several cars like this over the years and all of them would try to kill you at low speed.

[cartledge_uk]

That's exactly what is happening paul.

I guess I need a new rear end. Lol.

[PW@Woodsport]

Do you mean one or both wheels are deflecting in/out when jacked up?

If so then that's definately the problem mate.

[cartledge_uk]

Both, by a lot! Will try and get photos.

[cartledge_uk]

To add some more details.

there is Toe out under load, toe in under breaking, toe out under compression of a suspension strut, toe in under relief (? is that right) of the strut. The car is basically undrivable.

But I gave it a damn good go

[PW@Woodsport]

So it definately has wrong parts on there, Tim if you look at the rear hub mounting point for the track arm (adjustable tie rods), on a Mk1A the mounting is quite close to the hub, On a Mk1b it sits 3 inches inboard.

I suspect you have the correct susbframes fitted, because you do need to modify those to fit them, my money is on the hubs being wrong.

This makes the relationship between inner mounting point/hub swing in a different arc to the lower control arm, which then makes the hub steer in/out on compression/extension.

[cartledge_uk]

So it definately has wrong parts on there, Tim if you look at the rear hub mounting point for the track arm (adjustable tie rods), on a Mk1A the mounting is quite close to the hub, On a Mk1b it sits 3 inches inboard.

I suspect you have the correct susbframes fitted, because you do need to modify those to fit them, my money is on the hubs being wrong.

This makes the relationship between inner mounting point/hub swing in a different arc to the lower control arm, which then makes the hub steer in/out on compression/extension.

Yep

Thinking back, (I forgot to take pictures of the suspension componants before I left the car). I'll try and get some this week at some point.

Like you i'm sure the subframes are correct.

I'm not sure if the lower control arm is 1a or 1b (I think i could be 1a) the hubs I will need to check.

Thanks again paul.

[PW@Woodsport]

The lower control arms are all the same, so don't worry about that, i think it'll just be the wrong hubs/rear track arms.