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MG MGB Technical - Rear springs

My 73 Roadster is sagging on the rear drivers side about 3/4". When I looked closer I found that someone has already added a helper spring on both sides to try to remedy the situation.

So now I guess it's time to replace the springs. My question is simply should I get these from Moss or is there an alternative source I should look into.

Thanks,
BH
BH Davis

Oh boy. Unless it is causing you problems now, you can almost guarantee it will cause you problems afterwards. OE spec springs seem very difficult to get hold off, especially in the USA, those that are available usually result in a very high rear and difficulties getting the rear shackles and rebound straps fastened. The lower the ride the better the cornering.

Out of interest, what distance do you have between the centre of the axle and the bottom of the trim-strip on the rear wing? CB cars are typically 14.25", but can vary from 13.5" to 15.5".

Sag at one corner can be caused by a problem at the diagonally opposite corner. And if it isn't that and only one side - especially if it is the drivers side - I'd swap the springs over from one side to the other first.
Paul Hunt 2

Paul,

As always, thanks for the help !!

The passenger side has 15" from center of axle to bottom of the fender chrome trim strip above the axle.

The driver side has 14 1/4" for the same measurement.

Hummmmmmmmmmmmm......perhaps the passenger side is high as versus the drivers side being low ???

Maybe I should pull off the add-on helper springs and see what happens.

BH
BH Davis

try spraying lots of grease or penitrating oil between the leaves first and drive around for a while as they can stick together and make the car uneven
worked on mine so worth a try first
ste
Ste Brown

BH,

Are the front heights about the same? You can try swapping the springs side to side, but don't be surprised if the car still leans to the left. You can also switch the front springs. That didn't help me. I weighed my car a few years on some wheel scales, the rear was LS 541# RS 545#. On the front it was LF 583# and RF 559#. It's actually well balanced but it still leaned a little to the left. I think I had a little less than a half tank of fuel when I weighed the car. Later when doing some switching and measuring I noticed the lean was less with a full tank of fuel, however the rear dropped a little on both sides due to the weight of the extra fuel. I took two pairs of shackles and cut them to make longer shackles with a longer shackle on the left. That helped but the corner handling wasn't as good. I changed back to the standard shackles. The front was about 1/2"-3/4" higher than the rear. I decided to cut the front springs to match the rear. I made the right spring a little shorter than the left and now my car is close to the same on all corners, or it was the last time I checked. You may not want to try what I did on the front springs. You cannot cut an inch off and have the car sit an inch lower. You to work out the front spring location and figure the ratio of the spring center to the A arm lever ratio and work out the loaded height to the free length to determine how much to cut. Lots of work and if you mess it up it's new springs. I'm not suggesting you do what I did but it worked for me. Some people have experienced good results with lowering springs. They usually stiffer than stock springs.

FWIW, Clifton

Clifton Gordon

Two-word answer: John Twist. He makes 'em and they're right.

FWIW,
Allen
Allen Bachelder

Clifton,

I noticed this lean when the tank was below 1/4 full. I filled up today and the lean is almost completely gone.


So, what do you think? Perhaps the helper springs that were added are pushing up on the passenger side making it closer to 15" axle center to bottom of chrome trim instead of 14 1/4" as on the drivers side.

Without your information of 14 1/4" axle center to bottom of chrome trim it never would have occurred to me that the passenger side might be high.

BH
BH Davis

BH, I don't know why, but the rear springs are very soft and it seems to require very little weight change to affect their height. I have no experience with helper springs but I believe I would remove them and see what happens. It will probably be too low without the helpers, but it will probably improve the ride. I didn't know John Twist makes springs. Allen, have you tried his springs? Results?
I remember some people using some Jensen Interceptor rear springs that the Jensen Intercepror expert had made, on some cars the rear would still be too low.

Clifton
Clifton Gordon

As the tank is not that far off central it is sounding like something partially siezed on one side or the other if it makes that much difference. Measure them again putting a significant amount of weight in one rear corner then slowly lifting it up, then the other corner, then lifting one rear corner of the body and lowering it slowly, then the other, and measuring the ride height each time. For good measure do it to the front corners as well. Stiffness one side (or corner) compared to the other will be shown as a bigger difference in post compression (weight placed and removed in the boot) height and post expansion (raising and lowering the body) height between the sides.
Paul Hunt 2

Paul,

Thanks here as well. I will remove the helpers first....when I get around to do it. In the mean time I'll keep thank full!

Thanks,BH
BH Davis

This thread was discussed between 10/08/2007 and 12/08/2007

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