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8 & 10 cyl Bristol cars From Type 407 onwards

409 Torsion bars

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Old 20-05-19, 09:26 PM
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Default 409 Torsion bars

Recently I noticed the 409 is lower on the right side than the left.
The right side adjuster was all the way in, so I backed off the left one so as to level the car. Made no difference.
What have I missed?
Anne
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Old 20-05-19, 11:50 PM
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Anne ,
It is very unusual that the rear torsion bars would ever need adjusting to that extent .
Have you measured whether the front has sagged on one side .
I had this problem with a 411 in the past , one side at the front dropped which made the rear uneven .

Geoff
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Old 21-05-19, 02:25 AM
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Geoff,

I was thinking the same - I'd be checking the front suspension. It's possible the spacer above the coil spring has disintegrated on the right side - they probably all do eventually.
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Old 21-05-19, 09:44 AM
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Also possibly a seized rear shock absorber ?, on the side that hasn't come down?
A quick bounce on all corners of the car will tell you.

If so don't drive it any distance as it will destroy the upper mounting.

Roger
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Old 21-05-19, 03:06 PM
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Thanks,
I renewed the frt including the angled spacer about 3 years ago so it should be fine.
I can bounce the car on all corners and it moves accordingly. The rear is particularly responsive in that it still has old shocks. The frt are new.
Is the adjustment I tried on the left side correct?
I realize it's extreme but regardless of the turns the car remained the same.
Even if the frt was off spec I am surprised that my adjustments gave no results.
It's currently on my 4 post hoist.
Anne

Last edited by Anne; 21-05-19 at 03:59 PM.
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Old 23-05-19, 03:13 PM
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Anne

I have to say that that strikes me as really strange, car moves easily on all four corners, so nothing seized, but slacking off the LH torsion bar adjustment doesn't cause that side of the car to drop at the rear ? ? ?

Mind you (I hope you don't mind me saying), you are starting from the wrong point in that there wasn't apparently any problem with the LH torsion bar until you tried to counter what is actually a problem on the other side of the car. It is an interesting conundrum but it might well be solved by (or while) addressing the original problem. What you should be aiming for is to achieve a level ride both side to side and front to rear. Dropping one side at one end to match the other side is only a bodge. My 410 had sagged at the back (both sides) and the handling was transformed when this was corrected and it rode level all round.

If you already have the car on a lift may I suggest that you also raise the chassis to take all the weight off both the rear wheels. Also remove the rebound straps so that the axle drops just as far as it will go. From memory undoing just one side of the strap is actually sufficient. At that point there should, from memory, still be some tension in both torsion bars WHEN THE ADJUSTERS ARE ALL THE WAY OUT. I recall being quite easily able to take the remaining tension off the adjuster by applying a Stilson wrench to the front end of the bar, when everything was finally set up as it should be. If the pressure is excessive you will need to seek the cause. If the adjusters aren't bearing against their stops under light pressure as I've described with the axle dropped it is time to retension the torsion bar(s) by moving the adjuster arm(s) on their splines. You will need two people to do this. Soak everything around the front torsion bar mounting(s) in penetrating oil for a few days, get out your best (Whitworth, I think) spanners and set to. This is where you need a friend armed with a large Stilson wrench to pretension the torsion bar so that you're not having to fight it. From memory the mounting comes off from the front of the chassis cross bar leaving just enough space to withdraw the adjuster arm from its splines on the torsion bar. The adjuster arm is cast so take care but mine came off quite readily, with just a few taps with a copper hammer. It is all really well built out of quality material, which always helps, but perhaps I was lucky. Take a rest then ask the friend to pretension the torsion bar again and hold it. Move the adjuster arm one spline, replace it, and reassemble the front mounting. Your friend will need a fairly strong right arm, but nothing excessive. Repeat on the other side and replace the rebound straps.

Lower the back of the car back onto its wheels and screw the adjusters just far enough in to achieve a level ride. Don't overdo this as, if you do, the rebound straps will be in action all the time which results in a very odd ride.

By the way on my car I was the chap with the Stilson while a professional (who was a one man band) provided the intellectual input and did all the hard work. It was all a few years ago.

Good luck

Roger
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Old 23-05-19, 03:56 PM
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Thank you Roger.
Your methodology for resetting torsion bars is fine and something I had considered, but will need some help LOL
I see that you agree with me that by backing off the left side I should have seen some results....so a mystery? I will try and figure that one out and in the meantime soak the "guilty" sections in penetrating fluid.

Anne
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Old 25-05-19, 02:06 PM
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Anne

I certainly would have expected some result, I'd expect the car to come down about three or four inches on that side when the adjuster is taken from right in to right out. So, yes, a mystery given that the front of the torsion bar isn't seized in its mounting (if it had been it would quickly have become apparent that the adjuster wasn't bearing any load) and neither the back of the bar, the suspension arm, or the the shock absorber is siezed given that you can easily bounce the car on that corner on its worn shocks.

But continue to bear in mind that it was the other side that dropped. Now why, I wonder, would that have happened? Torsion bars do age over time, but usually both sag at much the same rate, so what has caused that side to drop?

Do please fill us in when you find either answer.

Roger
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Old 25-05-19, 04:21 PM
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I will ....after fitting it in with other projects.
At present it seems to be 3/4" down on the right and I am finding some response to the left adjustment. There is a little more to go so it will help.
I suppose that in the "big picture" it's not too bad.
Will do some driving as soon as the rain stops. Note that the car has been sitting since November so a shake down won't hurt.

Anne
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