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MG MGB GT V8 Factory Originals Technical - Rear anti-roll bar mountings

Hi folks,

Happy New Year to you all.

Can anybody advise regarding rear anti-roll bar mountings for a V8 conversion.

I am using a 1972 Costello converted MGBGT as a donor with, I presume, an MGBGT back axle with an MGC differential - 3.07:1. The recipient car is a 1978 MGBGT with the later back axle. Unfortunately the old axle, with the diff I want to use, doesn’t have the fixings for the post-76 rear anti-roll bar.

My car is using the lowered suspension kit with V8 suspension bushes and Spax telescopic rear dampers. I assume that it would be best to use the rear anti-roll bar, although earlier cars didn’t have one fitted by the factory. I can see a couple of options, which would allow me to connect up the factory rear anti-roll bar.

Firstly, I could have the diff taken out of the 1972 axle and fitted to the 1978 axle; however I understand that this is easier said than done because of pre-load considerations.

Secondly, I could fabricate some brackets, using the 1978 axle as a template, and weld them to the axle tube from the 1973 car. I might use the car as a jig, tack-welding the brackets in situ and completing the welding after stripping out.

I don’t see any other ways of solving this problem. Moss no longer market their rear anti-roll bar kit; Ron Hopkinson has now been absorbed into the Moss empire. Roger Parker at MGOC has no other ideas. I’d be very grateful for any advice.


Peter Hills

What does the car do that causes you to think a rear anti-roll bar is necessary? Does it have an objectionable amount of understeer that can't be overcome with the engine? I'm not fond of rear anti-roll bars on live rear axles as they increase the tendancy of the inner tyre to lift in tight corners, but the higher RB cars seemed to benefit some from the fitment.
George B.

Peter,

I agree with George re rear anti roll bars.

Tim Fenna at Frontline has a rear traction control kit.

Paul
Paul

Peter
I reinstalled the sway bar on my GM rear by using 4" long pieces of 2" square tubing.I clamped them together and used a 3" hole saw on a drill press to cut the required radius.I then purchased new urathane bushings for a 11/16" sway bar.They have much heavier straps.I bolted them to the new blocks and tack welded the assembly in place under the car.After removing,welding and reinstalling,the bar is back in original location.I then cut the center out of the bar.I used set collars on either side of the bushings to hold the bar straight.This results in perfect traction control,similar to a four link.I have done some experiments and found unhooking them results in severe wheelhop.With a 300 Buick,I need traction control! Just a thought,Mike
Mike Moor

In my opinion any aftermarket rear anti-roll bars are a waste of time and in fact can be dangerous.
You have only one of the two options you already mention.
If the 3.07 axle is from a 72 car it will probably need a rebuild in any event so having it fitted to the 78 casing could be the best option.
The factory roll bar also acts as an effective anti tramp bar when used with uprated bushes.
I did this on my car and I can give you the number of someone who can do these axles properly if you want.
He is located in north london.
Cheers
Les.
Les Cole

As Top Gear showed last week having suspension including ARBs set up ideally for the track makes them almost impossible to drive on the road, but only 1 sec faster in the hands of The Stig. The PO fitted a rear bar and uprated front to my V8, and it certainly does corner flatter than the roadster, but so what? The down-side is a greater tendency to lose the rear end in the wet, but it does seem to aid axle location when accelerating hard over poor surfaces.
Paul Hunt

Many thanks guys,

I only asked because the rear anti-roll bar was fitted by the factory to my car. I have not yet reached the point of driving the conversion sufficiently to be able to tell whether it would be necessary to modify the '78 axle to fit the anti-roll bar.

Indeed, several Wise Men from the East, and also some from the West, seem to think that it would not be necessary on a lowered rubber bumper car. Apparently some folk hold the view that the anti-roll bar does indeed improve roadholding but at the cost of a sharper final breakaway.

Would it be a general opinion that the rear anti-roll bar would not be an assett for a lowered car with only moderate (say 150bhp)?

Regards

Peter
Peter Hills

Peter,

I forgot to mention that it is Frontline Costello, so you may able to obtain information on your donor car.

Roll bars are a driver preference, drivers feel uncomfortable with roll and uprating springs and roll bars prevent roll. Lowering car prevents roll. A front anti roll bar may gain additional grip by controlling camber changes, but in general there is less grip as the inner wheel is lifted.

I would therefore uprate front anti roll bar first. Also a very stiff car tends to be a handful in wet so if used all year a softer set up may be preferable.

PH mentioned that on Top Gear The Stig only reduced lap time by 1sec with a track set up compared to softer road set up, some quaint TVR.

Paul
Paul

> Apparently some folk hold the view that the anti-
> roll bar does indeed improve roadholding but at the > cost of a sharper final breakaway.

I think Peter's nailed it. I use the Hopkinson set (7/8" front, 5/16" rear) on a chrome bumper GT that's slightly lowered in the rear. Superb roadholding and overall stability BUT the breakaway is very sudden and you don't get much warning. The key is to use MATCHED bars front and rear. I have heard that guys like Glenn Towery favor the Evolution II kit; I'm not sure who makes that but it's even more stout, with a 1" bar in front and I think a 3/8" in back.
Ted

This thread was discussed between 02/01/2003 and 05/01/2003

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