MGB vs Jag IRS suspension

289, FIA & Daytona topics
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Hamy-hoo
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MGB vs Jag IRS suspension

Post by Hamy-hoo »

Hi All,

I'm wondering what everyones opinion is on MGB rear axle vs the alternative Jag IRS unit?

I'd like my build to be a street car, but want to have the option to (maybe) do the odd track day and hillclimb as well. Should I go to the extra time and trouble of the Jag IRS or just stick with the MGB setup? Will the MGB unit handle the torque/power of a mild Ford 289 (aiming for circa 250hp)?

To avoid Q plates, I assume I'd have to get the V5 along with the rear axle for either option?

Any help on this would be marvellous.

Thanks one and all.

Hamish
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amulheirn
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Re: MGB vs Jag IRS suspension

Post by amulheirn »

Hi Hamish and welcome!

I've got a mild 302 with MGB back axle, which just passed IVA and I'm about to register. I went this route because I was more comfortable that it would satisfy the requirements for getting an age-related plate. Talking to Gerry Hawkridge he said the MGB axle was good for more horsepower than you expect and it would be fine. I can't tell you how it drives of course - I've only driven it onto a trailer and round the DVSA's car park so far, but it felt good while I was doing it!

I'm sure a few people will have better experience than I do of what these are like to drive. Gerry told me the MGB one was more forgiving in that when it is losing grip it does so gradually, where as the IRS one grips better but loses grip more suddenly.


Andy
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David Large
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Re: MGB vs Jag IRS suspension

Post by David Large »

I have a 29 year old BRA with a 240bhp 4 litre Rover and an MGB rear axle with a GT V8 differential. I have done 60,000 miles the first 30,000 with a different differential in it and the last 30k with the V8 3.07:1 diff. I changed the diff after some one tried to adjust the back lash in it for me; the V8 diff suits the car much better anyway. It is fine but the ride quality is I guess nowhere near as good as I would expect from the Jaguar back end. Most of the BRAs (except those that have been seriously modified) and the early Hawks I think will run the MG back axle with a number of them having 300+ bhp engines.

David
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clive
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Re: MGB vs Jag IRS suspension

Post by clive »

My car has a Ford 302 with Gerry's uprated tubular wishbone front suspension and Jag IRS rear. Like you Hamish, my choice was for a street car that was to be used primarily on the Highland roads where I live, but also has the grunt necessary if required. As a Cobra it had to have a Ford engine and the balance of the Jag rear end makes it very driveable as it is pretty much 50:50 weight distribution. From what I recall when discussing with Gerry, The Rover/MG combination is lighter and well balanced too, but just not right in my opinion. One other factor to consider, especially if driving quickly, the MG rear axle apparently gives more feedback as to when it is about to let go and apparently is easy to correct, whereas the Jag rear grips better but if it lets go it is difficult to correct and there is less warning that you are nearing the limit.
Cheers, Clive.

(If I'm not here I'm in my workshop or on the golf course!)
Hamy-hoo
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Re: MGB vs Jag IRS suspension

Post by Hamy-hoo »

Thanks everyone for your posts.

Given the feedback I think I’ll go down the MGB route, not least of all for IVA compliance and the feedback it offers when driving. This may sound odd, but despite building an AC 289 I actually don’t see myself doing silly speeds and needing the extra grip offered by the Jag setup.

Thanks again!

Hamish
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