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MG MGB Technical - Rear anti-roll bars on a 72 GT

A couple of Britiah Classic car magazine articles have recommended that adding a rear anti-roll bar is a good way of upgrading a B's handling. However, in contacting a local Mg supplier, they state that only rubber bumper Mgb's can be fitted with a rear anti roll bar.

Is this true and if so is there a conversion kit to overcome this problem?

Cheers

Iwan
Iwan Jones

'tother way round I reckon, from June 76 a rear anti-roll bar was fitted as standard.

My 75 V8 has the Ron Hopkinson rear bar and thicker front bar. It does ride very flat, seems to significantly improve axle location compared to my CB roadster and a friends CB V8, but the rear does break away sooner in the wet than the roadster.
Paul Hunt

I've got a 1" bar on the front and a 5/8" bar on the rear of my 72B and would not have it any other way. Will do the same to my GT if I ever find another set of bars. They were sold as "Evolution 2" but have not seen them lately
gerry masterman

Iwan-
Like you, I've got a 1972 MGB. Like Paul Hunt, I've got the Ron Hopkinson anti-roll bars front and rear, so your MG supplier is dead wrong about only Rubber Bumper models being able to accept a rear anti-roll bar. Early Rubber Bumper cars (1975-1976) had no anti-roll bars at all and later Rubber Bumper cars 1976-on) had them both front and rear. Paul is correct about the flat ride characteristics with the Ron Hopkinson kit. The car has almost no body roll going through the curves. The kit is sold under the name of the Ron Hopkinson Stage I Handling Kit and consists of a 7/8" front anti-roll bar and a 5/8 rear anti-roll bar. If you're interested in this, you can contact Ron Hopkinson via Email at Ronhop@easynet.co.uk . Be warned that if you add a rear anti-roll bar without increasing the diameter of the front one you'll damage the car's handling by making it tend towards oversteer!
Steve S.

Ron Hop is out of business but Moss-UK has picked up his line of products..I'm in process of buying a set right now from them...person to contact is Jason at derby@moss-europe.co.uk
Tony Barnhill

Steve,

With the specific anti-roll bar combination you have, what is the largest tire you can suggest front and rear? The good advice so far has it at 205's. As part of my decision to switch to hubs for bolt-ons, I am seekijng to maximise my tire patch. Going to 15 inch rims and rolling the fenders a wee bit is in the offing, but not flaring, at this time, anyway ;).

Tony,

Which diameter bars did you opt for? About how much does it cost with shipping?

Dean
Dean Lake

Dean-
I use Michelin XGTV4 tires, size P195/60R15 with stock rear wings (fenders). I also use an MGOC Panhard rod to keep them from rubbing under high lateral forces (cornering stress). These tires use a very soft rubber compound that sticks like glue and has surprisingly gentle breakaway characteristics, but you can expect the tread to be completely bald at 20,000 miles. Lifting the inside rear wheel on hard curves is quite possible. At $160 each, they're not cheap, but at least you get what you pay for. If this isn't enough traction, then you're probably using an uprated Rover V8. A P205/50R16 would retain the original rolling radius, but the shallow sidwalls would make for a punishing ride quality and twitchy handling characteristics. The difference in tread width would be a mere 0.10", so the liabilities would outweigh the small benefits.
Steve S.

Dean,

Just adding to Steve's comments, generally using wider tyres does not change the contact patch, but a wider contact patch will deal with more traction as well as cornering forces, too wide and you may lose any power oversteer unless engine is uprated and probably add to unsprung weight and be more expensive.

Iwan

With regard to anti roll bars, these may improve handling but also lose you grip as the inside wheels will start to lift, for racing this can be an advantage, but not for general road use. The rear bar will also give oversteer and possible early break away.
Frontline are currently working on a traction control link which basically acts like a panhard rod but allows for an adjustable roll axis, which should allow fine tuning of handling.

Paul
Paul

Iwan-
I can state from experiance that what Paul says about the inner rear wheel lifting under very high cornering stresses is true. To understand why, some information is necessary: An antiroll bar is nothing but a torsion bar, which is a type of spring. However, when a car is moving straight ahead on a smooth road the force on the axle is nonexistant because the transverse axis of the body of the car and the attached antiroll bar is parallel to the longitudinal axis of the axle. Only when the longitudinal axis of the axle deflects out of parallel with that of the bar does any springing effect occur. When the body of the car tries to lean over in a turn the logitudinal axis of the axle deflects out of parallel with that of the antiroll bar whose arms are attached to each end of it. The bar resists being twisted along its axis under the car, attempting to return to its original untwisted shape. Thus the end of the axle on the outside of the curve is forced downward and the end of the axle on the inside of the curve is forced upwards. As long as the leaf spring on the inside of the curve exerts more downward force than the opposing lifting force of the antiroll bar, the inner wheel will be held onto the ground. If the lifting force of the antiroll bar is greater than the downward force of the leaf spring, the wheel will be lifted off of the ground. Fortunately, such conditions are rarely encountered outside of a race track. Many manufacturers offer antiroll bars offer their producrs in standard diameters such as 9/16", 5/8", 3/4", 7/8", and even 1". However, this does not mean that all bars of the same diameter have the same torsion spring rate. This is dependent upon what alloy they're made of and to what level of hardness they're taken during heat treating. This is why it's so important to get then in sets from the same supplier, preferably from one of established reputation such as Ron Hopkinson. Naturally, these cost more. Quality always does. Generally, cheap antiroll bars increase their resistance more slowly as they twist and wear out sooner.
Steve S.

Dean...I'm running 205's on a set of 14"x6-1/2" Enkei wheels...I went with Ron Hop's sway bars (didn't know he had optional sizes so went with his recommendations; 1 is larger than OE, the other smaller)..shipping was $123...
....also have his Stage 2 handling kit that does away w/front OE shocks & uses his upper control arms & Bilstein tube shocks all around....have Doug Jackson anti-tramp bars, panhard bar, and composite springs...
...all this on a rubber bumper car that's lowered to chrome car height utilizing lowered composite spring on rear & MG Ltd vertically modified stub axles on front!!!
Tony Barnhill

Tony-
I hold before me the August/September issue of MG World. On page 10 there is a short article about Ron Hopkinson's new relationship with Moss Motors Europe. I quote:

"Well-known mg specialist Ron Hopkinson has joined Moss Europe as its Director of Marketing. Hopkinson's Derby-based outlet will continue, though, under the new banner Moss-Ron Hopkinson, and will be managed by Ian Wride, who has been with Ron since 1988. Moss says that the new arrangement will have an immediate effect on the Derby shop, with increased MG stocks, including parts for MGAs and MGFs, plus a wide range of tuning accessories. Ron Hophinson's in-depth MG technical knowledge will be put to good use, says Pete Buckles, the company's Managing Director. 'I am delighted that Ron has joined us. We see him as a major building block of our plans.' Moss Europe is on 0800 281182, while Moss-Ron Hopkinson can be contacted on 01332 572332; website: http://www.mosseurope.co.uk "

So, you see the Good News: Ron Hopkinson and his shop are both alive and well, still serving The Cause.
Steve S.

I remember that article...&, that's what got me woried as I was in the middle of my suspension converison...however, Moss-Europe told me "Ron stopped trading in May and we're assuming his stockage"...basically, the same thing the article said....
...except, they're harder to deal with than Ron was....with Ron, you told him what you needed, sent him a check in US $$'s (plus about $8 forhis bank to convert the check to Pounds)& he shipped the items...no questions...
...Moss-Europe requires credit card or Pounds Sterling-cash-only....&, their order line is not secure so there's no way I'm gonna send a card number in the clear...& they won't take even take a check on a British bank in Pounds Sterling....I have an account with a bank in Canterbury & could have a check issued from there, but Moss-Europe won't accept it...go figure!!!
...but, now that my friend is walking into their store & handing them Pounds Sterling, they've shipping direct to me....
...having to do the same thing for a European radio console for a MkII car w/steel dash...Pounds Sterling at the counterin the store!!!
Tony Barnhil

This thread was discussed between 05/01/2002 and 07/01/2002

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