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MG MGB Technical - Suspension bushes & lowering

I bought a 77 RB roadster a few weeks ago and have since driven about 1500 miles. Compared with my MGA, the ride is not as firm although the car corners quite well despite being at full height. The PO fitted new springs, arms and standard bushes all round and the cars sits with its tail in the air. It measures 17" at the rear from wheel centre to the chrome strip which I think is correct for this model. If I lower the car at the rear I have a choice of blocks or springs but my qustion is would the "soggy" ride be improved more by leaving the front and rear springs as standard and changing the rubber bushes to polyurethane. I've read all the archive stuff and there seems to be a certain amount of conflicting information, and taking 1" off the rear with lowering blocks seems a simple and relatively low cost way forward. For the record the car has four new Firestone tyres so the grip is fine. Body roll is not bad but it rides a little unpredictably, especially on country roads where the surface is not smooth. My MGA has standard rubber suspension bushes but the handling is firmer and more predictable. Any suggestions?
roger lawson

You'll be hard pressed to get the B to ride and handle like the A. The B was designed to be a bit more refined, to appeal to a wider market. Hence, the roll up windows, more spacious interior and softer ride. Adding some hefty sway bars will help your handling more than upgrading your bushings.
Rob ('61 A and '80 B )
R. L Carleen

Roger,

On the basis that 14ins is prob ideal ride height for a road B, any drop in height will help. lowering blocks are just not the best engineering solution but they work. Blue superflex will firm up suspension and removing the RB's will help handling.

Paul
Paul

Does anyone have advice/recommendations regarding switching to coil over suspension in a '72 B roadster fitted with a Moss supercharger. My car is beginning a complete overhaul and in addition to the SC I am leaning towards going with the coilover kit. -Chris



C.E. Sampson

Roger,
I've a '75 Rubber bumper. An went about improving the handleing in stages, just by chance.
I initially changed to chrome bumpers, this was a big improvemenr on handleing, those bumpers weigh 25KG each!
Then I put a 3/4 inch antisway bar on the front (there wasn't one previously) and this was a furthur big improvment.
I then lowered the car by fitting shorter uprated springs at the front and redrilling the spring hangers at the rear and moving the bolt holes up 46mm. Again an improvement. By redrilling the spring hangers ie. moving the front of the rear springs back to the chrome bumper position. You can get the ride down about an inch. This left the rear higher than the front, not a good idea really, but still better than before.
I then fitted 15 by 6 inch minilight replicas (195 by 60 tyres) as part of the V8 conversion. This also improved things a little.
Finally I fitted a pair of one inch lowering blocks and got the ride down to chrome bumper height front and rear. After the fitting of the antisway bar, this was the biggest improvement of all.
In order of value
1-Antisway bar
2-Lower (even) Ride height (blocks, redrilling and springs)
3-Bumpers
4-Big tyres.
Peter

Peter, I've considered most of what you recommend but I think I'll speak with a few MGB specialists first. Changing the front suspension bushes to V8 type and PU bushes on the upper links seems a good idea but I'm worried about shorter springs causing geometry problems. It's really the rear I want to lower but shortening the spring hangers is something I hadn't considered and would need to check since they are fundamental to the leaf spring movement. Surely it is safer and easier to fit the flatter springs. I want to retain the rubber bumpers since the car has been sprayed in metalic gold and it looks okay. For what it's worth the handling and cornering isn't too bad but the car feels a bit bouncy and unpredictable. My MGA has standard springs and bushes throughout and is a much firmer ride. I think tightening up the front end and dropping the rear should do the trick.
roger lawson

Roger
I'd agree with Peter. I have a 1980 GT which benefitted from front and rear anti-roll bars (I think all post 76 cars had the front and rear bars because of criticism about the handling on the 75/76 r/b cars).

This is what I did in addition to removing the bumpers altogether:

Front:
c/b springs
blue poly bushes
3/4" arb

Rear:
Removed rear arb
fitted 1" lowering blocks
swapped the lower two unstrapped leaves up to the top of the springs (car now sits at 15.5")

Recon dampers were fitted front and rear.

Initially I left the rear arb in place but because one of the bushes was loose and clonking on the hanger plate, I removed the whole thing. Prior to removal, though the car could be easily induced into hooligan oversteer on roundabouts, now it is less willing to do so without the arb. Also with the rear arb in place, the cornering felt very upright,although flat, rather than tucking in.

The lower c/b front springs also induce a small amount of negative camber which is useful, but the 3/4" front arb did seem to make the cornering better. A problem I do have to attend to is front wheel balance, as at 65-70mph I get a lot of steering wheel wobble which I am wondering if this is the result of using c/b springs on the r/b x-member.

As to removing bumpers, the front is easy enough and doesn't necessarily involve any cutting, welding or painting. At the rear, this too can be done but will need painting if it is to look right, but again can be done without welding. If you want more details on how I did my bumper removal, I can send you pictures.

I may consider the option of turning over the number two leaf on the rear springs and drilling the hanger plates if I want to get the height down a bit more, but frankly, just an overhaul of the existing set-up can bring big improvements in the ride and handling.

Martin
Martin ZT

Roger
I just redrilled the front (of the rear spring)hangers, not the back. Quite easy and quick to do, Just make sure you use a centre punch and small piolot hole becasue of the awkward angle. You don't want to go off centre, it'd be time consuming to correct.
The reason for adopting this approach was financial, you're quite right uprated flatter springs are better, just a whole lot more expensive!
The back hangers looked (a) to hard to adjust and (b)-As you say.
Also doing it this way gives you the ideal location for antitramp bars if you should upgrade the power output of your car.
I didn't mention that I also fitted blue poly bushes. These didn't seem to effect the handeling through corners (there might have been an improvement) but they certainly did effect the ride. Everything was firmed up, an impression of every joint being tight and no rattles. The ride did not become hard at all, if anything more elastic, just "firm-er". The car is much more pleasant to drive now.
Peter

This thread was discussed between 16/08/2004 and 20/08/2004

MG MGB Technical index

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