Steering, Suspension, & Brakes

tips, technology, tools and techniques related to non-driveline mechanical components

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roverman
Art Gertz
Winchester, CA.
(3061 posts)

Registered:
04/24/2009 11:02AM

Main British Car:
74' Jensen Healy, 79 Huff. GT 1, 74 MGB Lotus 907,2L

Vette IRS, anyone ?
Posted by: roverman
Date: September 17, 2020 02:37PM

Dana 36 or Dana 44 ? Later units 78' up ? are all aluminum and have limited slip. Common carriers are 3.9/1 and lower numerically.
Haven't weighed compared to Jag IRS, but must be much lighter. These units are usually less $'s than the Jag. rears.
Good Luck, Art.


Jim Stabe
Jim Stabe
San Diego, Ca
(772 posts)

Registered:
02/28/2009 10:01AM

Main British Car:
1966 MGB Roadster 350 LT1 Chevy

authors avatar
Re: Vette IRS, anyone ?
Posted by: Jim Stabe
Date: September 18, 2020 10:54AM

The C4's are all aluminum and have better geometry than the C3's. All the C3's are Dana 44 but the C4's come in Dana 36 (auto trans) and Dana 44 (3 pedal). The width is an issue with either. You can either make the suspension narrower or the car wider - I made the car wider.

Suspension install (5).JPG

reassembly (6).JPG


DiDueColpi
Fred Key
West coast - Canada
(1267 posts)

Registered:
05/14/2010 03:06AM

Main British Car:
What if the Hokey Pokey really is what it's all about?

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Re: Vette IRS, anyone ?
Posted by: DiDueColpi
Date: September 18, 2020 09:38PM

Jim,
every new picture of your car just makes my jaw drop!
So nice.
Cheers
Fred


BlownMGB-V8
Jim Blackwood
9406 Gunpowder Rd., Florence, KY 41042
(5968 posts)

Registered:
10/23/2007 12:59PM

Main British Car:
1971 MGB Blown,Injected,Intercooled Buick 340/AA80E/JagIRS

authors avatar
Re: Vette IRS, anyone ?
Posted by: BlownMGB-V8
Date: September 19, 2020 11:58AM

The Jag IRS is considerably easier to install in a MGB of course. It also used the Dana 44 (Salisbury) differential but had inboard brakes for lower unsprung weight. Custom length tubular alloy half shafts are available and lower control arms are easily shortened to fit. There may be alloy control arms available. The Jag can be used with the stock gas tank.

As for the weight comparison, I'm not sure how relevant that is unless your goal is a featherweight. With the alloy parts the comparison should be very close and the Jag may have the advantage in unsprung weight. Any increase in sprung weight will simply help offset increased engine weight to maintain vehicle weight balance.

Jim


Jim Stabe
Jim Stabe
San Diego, Ca
(772 posts)

Registered:
02/28/2009 10:01AM

Main British Car:
1966 MGB Roadster 350 LT1 Chevy

authors avatar
Re: Vette IRS, anyone ?
Posted by: Jim Stabe
Date: September 19, 2020 04:50PM

I agree with Jim B on the unsprung weight of the Jag. In my car's previous iteration it had a Jag rear and the extra sprung weight combined with the reduced unsprung weight allowed it to soak up bumps and ride really well. The inboard brakes really reduce the unsprung.



Edited 2 time(s). Last edit at 10/01/2020 01:14PM by Jim Stabe.


Jim Stabe
Jim Stabe
San Diego, Ca
(772 posts)

Registered:
02/28/2009 10:01AM

Main British Car:
1966 MGB Roadster 350 LT1 Chevy

authors avatar
Re: Vette IRS, anyone ?
Posted by: Jim Stabe
Date: October 01, 2020 01:14PM

I checked back and I had recorded the weights of the C4 Corvette rear I installed in my car. The one I weighed was the original D36 and it weighed right at 200 lbs including the coilover suspension units. I believe the D44 I have in there now adds somewhere around 10 lbs making the whole assembly around 210 lbs. I'm stretching my memory but I think the entire XKE unit I put in the car back in 1971 was about 320 lbs. If I calculate the C4 unsprung weight (all of the uprights, all of the rotors and calipers, half of the half shafts, half of camber rods, half of the trailing arms, and half of the toe rods) it comes to 92 lbs. Again stretching my memory I think the Jag came to about 60-65 lbs. Reducing the unsprung weight by 30 lbs can make a significant difference in the way a car rides, especially a light car. Adding the additional 100 lbs of sprung weight to the rear makes the difference even more dramatic.


BlownMGB-V8
Jim Blackwood
9406 Gunpowder Rd., Florence, KY 41042
(5968 posts)

Registered:
10/23/2007 12:59PM

Main British Car:
1971 MGB Blown,Injected,Intercooled Buick 340/AA80E/JagIRS

authors avatar
Re: Vette IRS, anyone ?
Posted by: BlownMGB-V8
Date: October 02, 2020 11:31AM

It would. I recorded weights when we did the Roadmaster Jag IRS swap and the total was less because we used one set of aftermarket coil-overs instead of the heavy original units, dumped the stock cage and used lighter isolators but it seems to me it may have still been around 50-65 lbs heavier than stock. (Which included springs, shocks,etc.) Further weight reduction is possible with alloy tubular half-shafts. But the relative simplicity of mounting was the main reason we went that way. The actual numbers should be in the Roadmaster thread.

The ride does bear this out, keeping in mind that we have nearly 8" of suspension travel, most of which is in sag of course. My last drive, and comparing it to my car which also has the Jag, I felt we could use stiffer springs and sway bar without any significant loss of ride quality. But having been a budget build it seems unlikely that we will change that. I think I may be running 375 lb/in springs on my car.

Jim



Jim Stabe
Jim Stabe
San Diego, Ca
(772 posts)

Registered:
02/28/2009 10:01AM

Main British Car:
1966 MGB Roadster 350 LT1 Chevy

authors avatar
Re: Vette IRS, anyone ?
Posted by: Jim Stabe
Date: October 02, 2020 10:28PM

I used the stock coilovers with the stock springs cut to give the proper ride height. I have no idea what the stock XKE spring rates were but the ride was good but firm. At the time (early 70's) I was impressed with both the ride and handling of the car. I would love to be able to compare that car with what I have today. Unfortunately, I cut up the old car to make what I have today so that is impossible. So I guess the brakes will remain spectacular, the ride phenomenal, and the final product a success.


BlownMGB-V8
Jim Blackwood
9406 Gunpowder Rd., Florence, KY 41042
(5968 posts)

Registered:
10/23/2007 12:59PM

Main British Car:
1971 MGB Blown,Injected,Intercooled Buick 340/AA80E/JagIRS

authors avatar
Re: Vette IRS, anyone ?
Posted by: BlownMGB-V8
Date: October 03, 2020 04:28PM

Well I'd say so!

Jim


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