Steering, Suspension, & Brakes

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

Go to Thread: PreviousNext
Go to: Forum ListMessage ListNew TopicLog In


rficalora
Rob Ficalora
Willis, TX
(2740 posts)

Registered:
10/24/2007 02:46PM

Main British Car:
'76 MGB w/CB front, Sebring rear, early metal dash Ford 302

authors avatar
IRS revisited
Posted by: rficalora
Date: September 26, 2008 09:46PM

Getting ready to put my fender flares on; decided it'd be a good idea to align the rear end... finished that this evening -- within about 1/32" so plenty close enough, but notice where the wheels are in the wheel wells once the IRS is aligned... 1" gap at the front & 2 7/8" at the back. Also, distance from center of front hub to center of rear hub is 90" instead of 91" as this diagram Andrew Bird on the MGBE board gave me says it should be... [www.andrewbirdonline.com]. Todd mocked it up on his early CB GT -- I wonder if there's a 1" difference between it & the later RB cars somewhere?

(Don't worry about the jagged edge, that'll get cut away more & tied into the fender flare when I put it on)

Wheel Placement.jpg

Anyway, the way the IRS is designed, there's no way to shift it further back w/o moving the ledge in the back of the trunk closer to the rear of the car... I'm thinking i'm going to have to do that to make it right -- very frustrating because that'll likely eat up most of the weekend. I sure hope this thing works well cause it's been a hassle so far. Oh, I'm also thinking I'm going to need heavier springs too because right now I can VERY easily bounce the car up & down several inches in both directions. While I'm messing with it, I'm going to see if there's a way I can move where the shocks mount so they're more vertical; that'll make the springs more effective. They lay at about a 45* angle -- the most recent Classic Rods mag has a coil over article that says the coil rating at 45* needs to be 1.4x whatever you need at vertical.

I'll be messing with it tomorrow; will post whatever I decide to do.


BlownMGB-V8
Jim Blackwood
9406 Gunpowder Rd., Florence, KY 41042
(6069 posts)

Registered:
10/23/2007 12:59PM

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

authors avatar
Re: IRS revisited
Posted by: BlownMGB-V8
Date: September 27, 2008 08:12AM

Rob, consider stiffening the settings on your shocks instead of the springs. One of the best features of the IRS is a compliant ride and too high of a spring rate will negate that. As long as it doesn't droop too much with your weekend luggage you should be good. Using a softer rate and stiffer valving can do wonders for your comfort level while still providing good handling. The exception would be a long sweeper where side forces overcome the range of the shocks and you might need a swaybar to help out. If you do modify the coil-over angle, try to do it in such a way that you can mount it at several different angles.

Jim


rficalora
Rob Ficalora
Willis, TX
(2740 posts)

Registered:
10/24/2007 02:46PM

Main British Car:
'76 MGB w/CB front, Sebring rear, early metal dash Ford 302

authors avatar
Re: IRS revisited
Posted by: rficalora
Date: September 27, 2008 11:35AM

Good input Jim. The coil overs have adjustable valving so that makes sense... good tip on the multiple angles too.


rficalora
Rob Ficalora
Willis, TX
(2740 posts)

Registered:
10/24/2007 02:46PM

Main British Car:
'76 MGB w/CB front, Sebring rear, early metal dash Ford 302

authors avatar
Re: IRS revisited
Posted by: rficalora
Date: September 27, 2008 02:07PM

I've been outside looking at it for an hour or so; this isn't going to be fun. Essentially, I need to remove this section & move it to the rear by 1"...
IRS Wheel Placement 001.jpg

That will get the wheelbase back to where it belongs & center the tires in the arches. It will put the back of the IRS about 1/4" from the fuel tank (you can't read it in the pic, but there's 1 1/4" clearance right now) but it will fit -- although I'll probably have to do something to attach the front of the tank because it'll be right where the trunk floor starts to curve up...
IRS Wheel Placement 005.jpg

I'll also have to modify where the IRS bolts to the frame (through the stock shock holes) because when i move it back, the holes will be 1" further forward...
IRS Wheel Placement 009.jpg

Oh, and I'll have to have another drive shaft made if moving the diff back 1" doesn't leave enough of the splines engaged. It doesn't move in/out like on a regular rear axle though so I might get away without having to do that.

Aaarrrrggghhhh!

The only other alternative I can see would be to have new control arms made that move the wheels back, but that feels like throwing good money after bad.


Moderator
Curtis Jacobson
Portland Oregon
(4495 posts)

Registered:
10/12/2007 02:16AM

Main British Car:
71 MGBGT, Buick 215

authors avatar
Re: IRS revisited
Posted by: Moderator
Date: September 27, 2008 03:45PM

Since you're going to install fender flares anyway, why not just install the fender flares a little forward of where you would otherwise have put them, so that the wheels are centered in the flares. Approaching it that way, the IRS suspension can be left where it is and nothing else needs to be modified. Why not? What am I missing?


rficalora
Rob Ficalora
Willis, TX
(2740 posts)

Registered:
10/24/2007 02:46PM

Main British Car:
'76 MGB w/CB front, Sebring rear, early metal dash Ford 302

authors avatar
Re: IRS revisited
Posted by: rficalora
Date: September 27, 2008 06:38PM

I thought about that, but I want to be able to go back to a regular axle if I don't like the IRS + when i clamped the flares on it looked "squatty" to me.


rficalora
Rob Ficalora
Willis, TX
(2740 posts)

Registered:
10/24/2007 02:46PM

Main British Car:
'76 MGB w/CB front, Sebring rear, early metal dash Ford 302

authors avatar
Re: IRS revisited
Posted by: rficalora
Date: September 27, 2008 10:15PM

Bit the bullet... about 1/2 done with the trunk piece...
IRS Wheel Placement 010.jpg

Welded the seam; still have to cut & weld in the 1" filler...
IRS Wheel Placement 011.jpg



Sorry, only registered users may post in this forum.