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MG MGB GT V8 Factory Originals Technical - Ford IRS

I was screwing around online this weekend, and found the website for factory five racing ( and took a look at their Independent Rear Suspension utilizing the Ford thunderbird IRS, and their own design of shocks and cage. The Differential is the popular ford 8.8" version that can be had in many different configurations. I called factory five today, and their technical support department measured the width from mounting face, to mounting face, and it was about 54.25". With a higher offset wheel, that should fit under a mgb fender without modifications. I'm still waiting for a copy of the installation instructions so I can further acertain the feasibility of this conversion, but for $1950.00, It's EXTREMELY appealing. That figure of $1950.00 included everything but the hubs and differential which are easily sourced from the Thunderbird Coupe. Shocks are supplied, control arms, axles, everything but the differential and hubs. As soon as I get more information, I'll share it with everyone, but I thought this would be a great way to get IRS without a TON of fabrication, excessive costs, and antiquated parts.


Hi Justin, I have finally my car in the garage. Now I can start looking into the IRS that I have been working on. I plan on using the Ford Merkur rear end but this Ford set up might be another way to go. Keep me informed of the info you get.
Werner Van Clapdurp

I don't mean to rain on anyone's parade, but there are two suppliers (that I know of) who offer an IRS kit (which seems to be the same kit) for the MGB based off the Ford Sierra (Merkur in the US).

NG Sports Cars:

and Hawk Cars:

The price is higher due to the crap exchange rate, but the kit is already developed and is a bolt in deal.

Mario Funk

What fun is buying something when you can pain stakingly build it yourself? :)

Besides, like you said, the exchange rate BLOWS right now. $1.62 US for each 1.00... that's crazy!

I received my copy of the instruction manual for the factory five kit, and after reading it a few times, and checking out all their pictures of it. I think this could come darn close to being a bolt in affair. I'm still going to have them measure some of the widths and see what we get. My biggest fear is the 54.25" width from wheel mounting hub to wheel mounting hub. My wheels have a 40mm positive offset, so I shouldn't have any problems, but there's no way rostyles will make it under the fender with this setup.


P.s. Werner, nice to see you online again, I lost my old e-mail account, and lost track of you, hope work is going well!

Ok guys, I've come to the conclusion that I physically CAN put the factory five IRS into an mgb with some modifications, but now the questions is should I? Would anyone care to give a dissertation on the benefits and costs of IRS vs live axle? During the spring/summer/fall the car is driven daily to work. (Just because I can.) For every stoplight I race a mustang at, there's 50 that I pass through normally. There will be the occasional long trip in the car (couple hours here and there) but mostly it will be my daily commute to and from work when it's pretty outside. Oh, and lets toss the argument of cost right out the window. I'm not worried about that. The IRS setup will be a 3.27:1 gear ratio with positraction. Coil over rear springs, and quad shocks to help hold it in place. And it happens to have disc brakes on it, so I'll retain those as well.

I think that's about all the pertinent information


A friend of mine who's a fairly prominent architect from time to time offers the following piece of advice:

"If you can, you should."
David D.

Just, DO IT.

This thread was discussed between 10/02/2003 and 22/02/2003

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