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MG MGB GT V8 Factory Originals Technical - IRS For MGB

I am not a big fan of IRS due in part to the complexity of getting the right alignment, specially in a narrow car like the B but that's is another story.

I was at a car show where I saw a Street rod that had an IRS that could fit on a B with minor and I mean minor work.

I call the Co. who sells the kit and they make it in a 52" Yes that's right perfect, this is from bolt face to bolt face.
What it would require is the following; The top mounting brace would need a plate welded on each side, this would mount the entire rear suspension to the bolt holes where the shocks are mounted in the rear of the B.
Then it would need a support at front (welded) for the torque arms, that would be it for the installation.
Next would be to fine tune the shocks and springs, and due the alignment. Brakes are inboard and are Corvette type, in fact the whole thing looks like it was inspired by Corvette, not a true Corvette set up.
Ok who is the co. that sells the kit?
Kugel Komponents In La Habra Ca. 2 hours away from me.
I am in no way conected with them.
They have a basic kit for $1495 and it goes up to $4695 with everything plated and custom third member etc. etc...
I think that could be the simplest for a IRS they may even modified them for B's They have excellent workmanship practices, I have seem some of their other products.
I hope this helps those of you who are seeking an IRS for your B Good luck
Bill Guzman

Not bad, it's a 9" and uses the half shaft as a control arm ala Jag. Not sure what function the torque arms serve. I'll be getting back on the t-bird unit in a month or two though so I'll pass.

Jim Blackwood

Don't like IRS? So use a deDion and get the advantages of reduced unsprung weight and fixed camber and toe regardless of body roll or suspension bump and droop
Greg Fast

Actually, even live axle cars exhibit some rear wheel steering due to body roll as either one spring flattens more the the other and cocks the axle or with coils and multi-links the links flatten more on one side than the other with the same effect. The deDion would do the same but has the disadvantage of more total weight, which slows acceleration.
George B.

I must agree with Bill Guzman on this one.

There is a huge difference between just bolting in the components to fit an independent rear end and getting it all to come together in the right way and that applies to de Dion as well.

I can't help getting the impression there are a lot of people thinking that just having IRS will solve every problem thay are likely to have with their car.

Sorry but having a well sorted 5 link or leaf spring arrangement is far and away ahead of a poorly designed and executed IRS.

Thanks for the post and the link Bill.

Cheers, Pete.
Peter Thomas

The Kugel design is based on a Jag IRS. Kugal is just one of many companies that build similar IRS units, in just about any width you want. Check the ads in Street Rodder magazine for names of some of the others. IRS setups from these companies may be had in a Jag type or a Corvette type, with either the stock differential or a custom made Ford 9".

The Torque arms are vital (on a Jag based setup), but are often overlooked. Without them, the only thing locating the wheels in a fore-aft direction are the "A" arms. Not good! The front pivot point for these arms must be in line with an imaginary line drawn through the inner A-arm pivot point to avoid binding.

Agreed, an IRS in and of itself is not the be-all, cure-all many may think it is. However, A well designed IRS is better than an equally well designed live axle or a DeDion setup. On the other hand, a well designed live axle is more than adequate for most street driven cars.

An IRS unit does have one significant advantage over the others - it has tons of "gee-whiz" factor. The gee-whiz factor is of prime importance to the typical street rodder; less so, I hope, to most of us. Less, maybe, but still of importance.

There are two significant advantages to an IRS, both related. One is the reduction in unsprung weight, and the other, obviously, is the independance of one wheel with respect to the other. If you were driving on a billiard-table smooth road, neither would be of any benefit. If the wheels are not bouncing, unsprung weight is not a factor. And, again obviously, if the wheels are not bouncing, one wheel's movement can't effect the other.

Suspension design - front or rear - is not trivial. Before making any suspension changes, it would be well worth the effort to do a LOT of reasearch and study.

Maybe an article on the subject would be worthwhile in the Newsletter?
Dan Masters

Bill where did you see the price of $1495? The base setup on their website is $4695.00. If they're selling just the framework, and you have to supply your own diff,suspension, etc, then $1495 isn't really anything special. It just allows you to break up your purchase into several small events.
I chose my IRS setup because it comes from a car the same size, and weight of an mgb, is almost completely adjustible, is designed for high power applications, and has been the pivotal factor for several racers having won scca championships in the cobra categories. Yes I'm having to do some welding work, and yes it's 2" wider then an mgb rear end, but in the end I'm going to have a more sturdy frame, the famous ford 8.8" differntial, and the stubs, and brakes from a big ford thunderbird. Short of cutting out the battery box, and moving the gas tank to the trunk, it's the best IRS option I've seen for an mgb. I may have a line on a welder who can do the work to get my system in before winter, so we'll see what happens. I think the handling characterists of my car should improve dramatically over the bone stock live axle that I currently have.


I resisted the lure of IRS for many many years, and in fact still believe that the stock MGB rear axle and suspension can be made to work admirably well under most circumstances. However things eventually changed. Time passed, and my back is no longer as tolerant of a stiff suspension. Horsepower increased and the life of a stock axle was correspondingly reduced. In the interest of handling the extra horsepower there is an abundance of choices for a replacement axle. In the interest of preserving the aging discs in my spine, a longer travel suspension with progressive spring action and minimal unsprung weight would be a significant benefit. Handling must not be compromised. Several IRS designs hold promise of satisfying these requirements. In terms of safety, I've had more than my fair share of universal joint failures and am loathe to place a pair of universal joints in any suspension control arm. This pretty well eliminates the Jaguar inspired units. It turns out that the Ford T-bird IRS meets the requirements and has a lot of promise, plus it has the lower control arm pivots spaced widely enough to eliminate the torque arm requirement that Dan explained. However, it does require modification to be suitable for installation in an MGB. One such modified unit is the one Justin is installing, and seems a pretty good choice. I am pursuing a slightly different route and fabricating the needed components myself. Don't scoff, I do this sort of thing for a living, and do reasonably well at it. Solid attachment and suitably compliant isolators combined with adjusters in strategic locations are the keys to a solid, tunable suspension which can provide a good ride. Inboard brakes can reduce the unsprung weight.

A good bit of development work remains to be done and it may be summer before the job is finished. But when it is I'll be happy to report all the details.

Jim Blackwood

Hi folks,

The question of IRS for MGBs is rearing its head again in the UK. There are a couple of companies retailing them.

Roger williams - he of 'How to give your MGB V8 Power' - has a second book 'How to improve your MG, MGc and MGBV8' ISBN 1-901295-76-1 published by Veloce. See also

In this second book Roger discusses Walden Suspensions and Hawk/NG Cars IRS products. Ford donor parts are used on both versions.

Roger also discusses more modern rigid rear axle suspensions but leaves his readers to make up thier own minds as to what they feel will best meet their requirements.

Hope this helps.

P L Hills

Geoff King has a superb IRS setup on his V8 roadster, it's the nicest engineered car I've seen so far, you could ask him about it, I'm sure it was a UK engineered kit, and it uses all the cart spring fixing points, so no welding or drilling.

Michael barnfather


Waldren went out of business - it was used on Cosworth by Falla but needed a lot of welding.

The Hoyle IRS is Cossie based and used by Geoff and tested by the Late Trevor Taylor.

Frontline are in design stage for rear to handle the 340bhp demo car.

Tony Bolton has a possible Chapman Strut system available for B.


I drove my friend Trevor’s V8 RD MGB here in Ca. when we pick the car at the dock at Port Hueneme in Ca. (9 miles from my house) It was shipped here from UK. after his passing, the car was given to his Fiancé here in Ca.
The car handle very nicely and it's well done, that rear suspension was specially design for the MG and I think is the best IRS for the MGB that I have seen.
I have seen the Cobra, and Jag adaptation and they are ok but not great. I saw one no to long ago that was copy from the C4 Corvette using an 8 inch Ford and it also has the camber arms just like the Corvette in smaller version, it's no on the car at the moment, I am just waiting to see how it will handle.
Corvette uses camber arms to control the changes of camber in the swimg axle set up, it also uses to unequal links on each axle with a single leaf spring.
very simple. I hope it works ok.
Bill Guzman

Very interesting thread.The IRS system mentioned by Bill Guzman is The Hoyle Engineering unit who are based in Epsom Surrey UK Tel no. +44(0) 208 393 2555
e-mail and is a straight bolt in conversion with double wisbones and coil overs diferential and uprights are from English Ford Sierra
or you could possibly use Mercury Merkur parts also uses rear discs from same source.
This is the same system used by Hawk cars Cobra replica and NG Cars own Kit.
Hope this of assistance.
Kevin Jackson.
Kevin Jackson

This thread was discussed between 21/09/2003 and 03/10/2003

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