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MG MGB Technical - RB to CB

1978 MGB GT( Rover 3.5 conversion)
Thanks to all you guys for the info on lowering the rear suspension,could I please have advise on the FRONT suspension,namely
1)Anti roll bar 3/4 or 7/8 inch dia.?

2)Springs,part no. and diamentions?
3)Do I have to fit the shortened bump stop(part no . MGS30756)?
Finally any report back 0n the affectness of relocating the front rear spring mount WITHOUT lowering blocks.
Thanks Trevor Burnett
t burnett

Antiroll bar. This one is the last piece of the puzzle.
It is going to depend. Car height, Wheel size and tyres you use, weight distribution, front wheel camber, panhard rod (if yo have one) height, stiffness of springs at the back etc. Essential, set up the car, try it in wet and dry conditions then give it your best guess. You might get it right first time, but I doubt it. I initially tried a 3/4, but in wet conditions still had plenty of over steer, a bit dangerous. I've now gone to a 7/8ths and it is pretty well perfect. There is a tiny bit of inducible over steer, and that is what you are supposed to have say all the experts. It I went to a one inch I'm pretty sure I would end up with over steer. For reference, , my car is a Rubber bumper car converted to V8 and chrome bumpers. The engine is set back about one inch further than factory, I'm using a supra gearbox which is about 25kg less than the mg one (weight out of the front =weight distribution increase in back). I have light weight composite springs (5 lbs, or about about 15 lbs less each) antitramp bars and a panhard rod. I'm using a saab space saver spare (about half the weight of std). I've used lowering springs at the front, bought from an MG place. I asked for uprated and lowered to chrome bumper height springs. 13.75 inches from wheel centre to bottom of chrome strip. This gives a small amount of negative camber, which in theory will grip a tiny bit better in corners. I've got a tow bar fitted. Wheels are performance supalites (minilight replicas) 15 by 5" with 195 by 60 Xm1 Michelins. Weight distribution is pretty much 50/50.

Front bump stop-best solution, remove/move the Aluminium spacer up. With your up rated springs ad heavy sway bar this may not be necessary, try it and see I suggest.

Reverse eye springs are probably the easiest approach. Take the top leaf of your springs to a spring maker and get him to reverse the curve. This will bring it down 2 inches. you might also experiment with re-stacking the spring leaves. That's wher you move one of the longer leaves to the bottom so it excerts its resistance later. Wont cost you anything to try.
You definitely need to cut about 20mm off the bump stop. If this contact prematurely in corners you will get snap over steer. An easy job.
Because I'm using composite springs which are one size fits all, I've both redrilled the front spring hanger and fitted blocks. Without antitramp bars fitting blocks will increase the amount of axle tramping. With antitramp bars this is not a problem. You absolutely should be using antitramp bars. I tried it without for a long while and had to go very easy on the accelerator. After I fitted them (bars) I could not believe how much more controlable the car was. Also how much greater the acceleration was. I could put power on te road. Just point and go. Mine came with the composite springs, but you could easily make some.
I'm attaching a couple of photos of how to best redrill the hangers if that's what you want to do.
Because of the angle you need to use a simple drill guide to drill a pilot hole. Also because of the angle, expect the hole to move about one tenth of an inch. you also need to cut out the rubber bumper reinforcing web, or allow the axle to move back about 10mm. Initially I tried it (about a year) with the axle slightly further back, then had to move it forward again to fit the panhard rod.


Peter Sherman

After you've drilled the pilot hole, you then drill it out to about one or two sizes smaller than final. This leaves you with an oval hole. Drill angle again.
Then you wind the final drill bit though with some grips, this rounds and aligns the two holes. Easy to do as the end of the drill bit fits in the hole.

Peter Sherman

Here is a photo with the web uncut. Actually it turns out to be easy to cut the web, 5 minutes with a large angle grinder.
Note that the old hole becomes a perfect antitramp bar location.


Peter Sherman

Ishould add,
45mm at the hanger gets you about one inch at the axle.
I also used one inch blocks.
I should also add you can buy reverse eye springs from moss. LOTS cheaper to alter your own of course.
Peter Sherman

Hi Peter,thanks a million for all the info,much appreciated,do you remember the front springs part no.?
Rgds Trevor burnett
t burnett

If you do use lowered front springs you can make the lowered front bump stops themselves. I bought some then found they seem to be normal ones cut and re-welded. If you are careful you should be able to do it without upsetting the rubber.

There is a picture of my bought ones here: http://asciimation.co.nz/pics/page14.html

The front springs I used are Moss AHT21s. You can see how much shorter they are.

I went for a 3/4 inch front ARB but the car isn't on the road yet so not sure how that will go.

Simon
Simon Jansen

I should have said I also had the rear springs flattened to lower the back. Still need to cut the rear bump stops down. I also fitted telescopic dampers but I wanted to stiffen the car up all around. Some people find them too stiff on the rear although I wonder if that's because they don't uprate the front at the same time.

Simon
Simon Jansen

Sorry Trevor,
This was the first thing I did to the MG when I bought it and knew nothing about that sort of thing then. I simply asked for Uprated RB to CB conversion springs.They were $110 and set the car at 13.75inches, middle of wheel to bottom of chrome strip. For me that was a 2" drop. My car is a 74.5.
You can also get lowered kingpins/axle stubs.

http://www.mgbmga.com/tech/mgb14a.htm
peter

If you redrill the hangers, when you are setting up the guide make sure you measure from a common point up front somewhere. The crossmember or jacking point, for example. The backs of the hangers are not symmetrical.

Here are some photos of Simons reverse eye springs down the bottom of the page.

http://www.britishv8.org/MG/SimonAustin.htm

As you see, the top leaf is effectively flipped over. A spring maker will only charge one or two hundred dollars to reverse the curve for both of them, an easy job for him.
Peter

typo up there,
"If I went to a one inch I'm pretty sure I would end up with over steer".


Should read understeer
The dangers of typing when drinking a very fine Durif.
peter

This thread was discussed between 07/04/2009 and 08/04/2009

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