Scary rear handling!

[plugy]

Hi gang! 

Well ive had my rebuilt cab on the road for the last few months and as good as it goes there is one major issue clouding the overall experience.

I stripped the cabriolet leaving only the engine and box in. The underside was stripped to bare still etc etc and now looks good. 

Rear beam rebuilt by imaxles
New rear dampers and mounts
Calipers rebuilt  all round
New gearbox mount and engine mounts and lower arms and front shock absorbers etc. 

The issue im having is... Drive below 50mph and everything is fine. 

60 or above and any amount of steering i.e to overtake on the motorway or to take avoiding action for example. The rear feels like its a few seconds behind the front steering input. 

This below is copy and pasted from another forum (not mine but descibes it to a T!) 

Just been on holiday in the South of France for a week and naturally this involved a decent amount of Autoroute driving. I noticed some (frankly bloody worring) handling from the rear of the car on the way down though, this was at higher speeds: 60 to 70mph.

The best way I can describe it is that the back end was wallowy and seemed to lag (if that makes sense) behind the reaction of the front end. For example, at 60mph I'd very quickly snap the steering wheel left-right just to sort of 'wiggle' the car and there was a clear noticeable time difference for when the back would follow the turn/wiggle - about quarter to half a second after the front had settled. 

It was extremely disconcerting in swooping bends at motorway speeds and the back end just felt loose!

There was no real answer provided in the thread. 

Any thoughts?

Thanks in advance!

Rob

[Piggy]

Imaxles.

Enough said.

[plugy]

Imaxles.

Enough said.

I can see or feel any moverment in the radius arms nor any knocking.. 
The torsion bar is the correct thickness for the cab. 19.3mm. Ive phoned them and spent quite some tine on the phone and even sent them videos and they never got back to me via email. 

One thing i did wonder is.. Has the torsion bar been remade i.e tempered or just an old one they have put in?.. Not sure but ive checked everything the mounts are in correctly and everything is tight. 

Rob

[Piggy]

Are the mounts new?

What tyres are you using and are they set to the correct pressure.

[plugy]

Imaxles.

Enough said.

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All mounts are brand new from gsf. The 2 smaller ones near the spare wheel and the 2 bigger metal ones in front of the spare wheel are all new from gsf. The tires are riken (mitchellin?) Pressure i have tried 34 psi at rear and 36 at front as per factory and also tried 36 at rear and 36 at front and makes no difference. I really want to get this sorted as my 2 year old daughter goes in this car. Appreciate your effort fella. Thanks.

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Not sure why its quoting sorry about that.

[Martin306]

My experience of IM axles is that they simply re-use old bars and just give them a soda/sand blast and a powdercoat.

I'd say it's down to your tyres if you're convinced it's not the axle. What size of tyre are you using and how old are the tyres?

[plugy]

Took the car to my tyre place today and they checked the car over and when i said take it out.. Within minutes the lad was back and confirm theres deffinately a serious issue. Believes its the axle at fault so phoned imacles and theyre sending a newnone

[Mighty306]

Interesting. If there was a serious issue with the axle I would have thought it would be making some nasty noises.

[Martin306]

Might not be noticeable play when feeling it by hand, jacked up.

Once the weight is on it it's probably behaving different. The IM Axle on my 106 behaves like that but I've just got used to it, it's not too bad.

I'm driving on 80 profile tyres too so there's plenty of warning before it even thinks about letting go.

[Stef205]

My experience of IM axles is that they simply re-use old bars and just give them a soda/sand blast and a powdercoat.

The re use of torsion bars / arbs is perfectly acceptable providing they are in good order, new bars are very expensive at times.

[Martin306]

My experience of IM axles is that they simply re-use old bars and just give them a soda/sand blast and a powdercoat.

The re use of torsion bars / arbs is perfectly acceptable providing they are in good order, new bars are very expensive at times.

What I meant was them using bars that have lost too much across their section. It's the same principal as re-painting a coil spring. I would imagine a few axles they get back have pretty flaky bars!

OR using 2 left hand bars on the same axle which usually ends up with your car being lop sided because the metal has been sprung one way for so long.

It does depend on the condition of the bars I know dis

[plugy]

My experience of IM axles is that they simply re-use old bars and just give them a soda/sand blast and a powdercoat.

The re use of torsion bars / arbs is perfectly acceptable providing they are in good order, new bars are very expensive at times.

What I meant was them using bars that have lost too much across their section. It's the same principal as re-painting a coil spring. I would imagine a few axles they get back have pretty flaky bars!

OR using 2 left hand bars on the same axle which usually ends up with your car being lop sided because the metal has been sprung one way for so long.

It does depend on the condition of the bars I know dis

I know with leaf springs they can lose their spring rate especially after 20 years of use.. And have to remade and tempered.  But if this tends not to be the casr with torsion bars fair enough. 

They're sending another axle out either way.. Never been convinced by this axle i currently have. Everything around the axle is brand new.. Mounts, shocks, hubs and bearings so i really dont know what else the issue could be. Ive worked on various cars new and classics and never had such an issue before. Only similar issue i had was my old 79 dolomite the rear radius arm bushes began to perish and made the rear feel very wooly. Going to try a few things before swapping the axle over.