MatraSport Forum

Each model => Bagheera => Topic started by: sakarlsson on October 11, 2009, 12:17:05 am

Title: Rear height adjustment.
Post by: sakarlsson on October 11, 2009, 12:17:05 am
Hi All!

I know that the rear height adjustment is notorious for seizing up - and this is also the case on my bag. I thought that I should not need to adjusted it, and therefore it should not be a big problem.

However, after assembling and adjusting the front suspension as good as possible I realize that the rear right hand side is actually rather too high. I have welded new attachment points, left and right, but I'm pretty sure they should not be off by more than a few mm.  Can't figure why, but it is definitely to high, perhaps 2-3 cm.  I guess I could try to switch the torque spring one step, but in my book that must lower it way too much?

So my question is: has anyone, ever, manged to "unseize" the rear adjustment mechanism? I have read that one (destructive) method is to make one functional assembly out of two seized.  This may of course be an option if I can get hold of a spare assembly or two...   

BTW, have had my bag painted orange this week. Will post some pics later on...


  -- Anders

Title: Re: Rear height adjustment.
Post by: andyowl on October 11, 2009, 12:53:34 am
Yes, I have unseized the S2 rear suspension in the last 2 months.  I just have not had time to write to the Forum with the method and pictures. Apologies. Thanks to Greig Dalgleish in the UK for his advice and his research.

I will try to do the write up after tomorrow,Sunday, when I am testing the now absolute minimum suspension at "Sprint Royale" near Aldershot.

In summary:-
- Remove the trailing arm
- make a diagonal cut with a 1mm angle grinder cutting disc on the forward face on the arm in the aluminium casting almost through to the steel torsion bar socket (say 1-2mm ally left)
- Split the remaining aluminium with a heavy screwdriver or chisel,
- This releases the pressure of the corroded aluminium and "unseizes" the arm
- Put oil into the gap and hold the gap open with a scredriver while you force stainless steel wire or galvanised nails into the cut to keep the gap open while it is welded up again. The aluminium is good quality and not difficult for an experienced aluminium welder - get a professional to do it for you.
- The result is that the arm will move stiffly although you may need to hit the cam with a hammer to make it lower. Raising the ride height with the allen screw is easy.
- My arms were done 5-6 weeks ago and they were still free in the last week when I had to take the drives shafts out (again!)

It can be done!

And Boy, does a lowered Bagheera look mean and racey?

Andy Owler

Other things to think about with a lowered Bagheera..
- Can you get the jack underneath?  we had to make new jacking points
- You may need to reposition the rear brake hydraulic hoses in the new position
- You will need to check for tyres fouling the rear wings and bumper
- When you put the car on a trailer can you still open the doors over the mudguards?
- On the trailer, will it still go up the ramps or will the chassis contact the top of the ramps?
- Check any speed control ramps in your street. The bottom of the gear linkage will be the first thing to hit the concrete
- The second thing to hit the concrete will be the silencer and maybe break one of the manifold pipes!
- If you still want to carry three people and their baggage there will be a limit to the amount you can lower the rear before you run out of suspension travel.

It has not been just the problem of unseizing the trailing arms!


Title: Re: Rear height adjustment.
Post by: Spyros on October 11, 2009, 09:25:14 am
I heard others saying that they managed to unseize them by slow eating of the arm.
The Bagheera specialist of Matra Passion told me that he does it with force only

Title: Re: Rear height adjustment.
Post by: andyowl on October 14, 2009, 09:08:10 am
Pictures of the unseizing process.

I was using an old camera and I did not check the picture for quality after taking the shot. The quality is terrible and I apologise most sincerely but I hope you get the idea of how it was done.

See also the description I posted a few days ago.

Title: Re: Rear height adjustment.
Post by: andyowl on October 14, 2009, 09:39:14 am
Before I resorted to cutting the aluminium I also tried force - and lots of it as you can see from the pictures below. The adjusting screws were not too difficult to free off after a good soaking in PlusGas. (I used to think that WD40 was perfect for releasing seized threads until Chris House introduced me to PlusGas - which is perfect! Buy it on eBay if you can't get it locally).

Force is usually my second thought after science (I was trained originally as a ship's engineer whose motto is "If in trouble or in doubt, get a bigger hammer out" followed by "Hit it once and hit it hard")

Nothing moved!

The grease nipple addition, as recommended by TUV for all German Bagheeras, also did not help. You can see why from the pictures in my next post which show the severe corrosion between the aluminium casting and the steel torsion bar socket. If the grease nipples had been fitted by Matra originally they might have been effective but fitting them 30 years later is never going to work. There is nowhere for the grease to go!

Andy Owler

Title: Re: Rear height adjustment.
Post by: andyowl on October 14, 2009, 10:03:44 am
Trailing arn corrosion..

Greig Dalgliesh in the UK Club (Bagheera S1 expert) cut open an old trailing arm to check its condition. He lent it to me when I was starting to unseize my S2 suspension. You can see how bad the corrosion is at the interface between the steel and the aluminium. I doubt if any amount of force would move that much rust.

It is a tribute to the quality of the aluminium that the arms do not split by themselves just from the pressure created by the corrosion!

You can see where he cut 95% of the way through the aluminium and then split the rest. That is what gave me the idea of our diagonal cuts and subsequent re-welding.

Greig is a true pioneer! Thanks Pal!


Title: Re: Rear height adjustment.
Post by: andyowl on October 21, 2009, 06:49:01 pm
I have put an update on the "rear height adjustment" experiment on the "Roll cage wanted" thread today.