Thread: Narrowing a C4 IRS....Wow....my head hurts!

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I can't tell you all my worries with this C4 IRS. LOL's. But I think I can...I think I can.

Who on here has done the C4 IRS set-up on thier street rods? I did a search in the photo gallery but I'm still having trouble.

What angle do I need to set the frame bracket for the dogbones? 55 degrees looks like it will still allow plenty of suspension travel (3.5" or so).

How narrow have you guys gone? I was thinking about making a 1" spacer between the differential and the cover, which would move the batwing back 1" and narrowing the rearend 6" over-all. I would still have to hog out a small portion of the hubs (knuckles) to clear the batwing....but not much with the spacer added.

I could really use some help here. I'm about to ditch it and opt for a nine inch. I dont usually give up this easy...but man my head hurts.

I've got another thread similar but this one isnt really about alignment....please dont burn me.

Dave

How much you narrow it will depend to some extent on what offset wheels you are using.....

What angle are the bars at when the IRS is in the Vette, parallel with the ground, or front up a bit????

Last IRS I played with was a Ford 8.8", about the same headaches though.... Ended up having to do a lot of mods on the hubs and built both half shafts.....

Lots of extra work and expense, especially for a fendered car.... If I do it again it would be on a fenderless car, and just for the aesthetics.....

Originally Posted by Dave Severson

How much you narrow it will depend to some extent on what offset wheels you are using.....

What angle are the bars at when the IRS is in the Vette, parallel with the ground, or front up a bit????

Last IRS I played with was a Ford 8.8", about the same headaches though.... Ended up having to do a lot of mods on the hubs and built both half shafts.....

Lots of extra work and expense, especially for a fendered car.... If I do it again it would be on a fenderless car, and just for the aesthetics.....

I'm gaining a little ground. The options seem unlimited.....cant decide which route to go. I'm still trying to get info from some of the Corvette forums. Still diggin.

Dave

use one from the earlier years of the C4 as they are narrower

Also---narrowing that rear end ANY pretty much means that you need to redesign the frame back there--it really isn't compatable with a ladder style frame because you need room for the spring, shocks and the 4 bars

Look at using it the width it is and use wheels with an offset that works

I have a C3 under mine, and frankly had I had my say in it, it would have been a 8 3/4 or a 9". Expensive to acquire, expensive to put in, expensive to repair, and the ride and handling ain't all that more wonderful than a standard set up. Never again.

Well....I've decided to ditch the idea. I've decided I'm going to lose too much bed space. I can do it...but I'll have to raise the floor of the bed to make it work. I've decided to chock this up to a painful waste of money....and will give it to my dad for his 41 Ford Coupe. It has a much wider frame and losing a little space in the trunk won't matter as much. Thanks everyone though. Dad is tickled with my mistake!

Dave

Tell him it was an early Father's Day gift.

The Vette rears look great and under some cars it really rides well. A lot of things must be taken in to consideration when installing one in anything other than another Vette. Specifications such as wheel base, body type (steel or glass) front/rear weight ratios, hp/torque/ rear end clearance, etc. must all be given consideration. If the setup and body weight is very similar to a Vette, then the ride should be very good. If the body weight is heavier and/or the weight over the rear is greater than it was on the Vette, then the ride quality may be less than ideal.

I have an all steel sedan, with a wheel base that is 16 inches longer than the Vette that the suspension came out of and the added weight over the rear suspension creates a less than perfect ride. Mine has the composite rear spring and standard vette shocks (not coil overs), so I may be able to improve the ride by switching out to coil overs. Not sure if the cost would justify the improvement. Also due to the location of the bat wing and gas tank there is no room for a rear sway bar, which would really help my ride control and comfort.

A couple of years back I had to have one of the half shafts replaced along with a new composite spring. Cost was over to $1200. Parking brake adjustments can be a real pain in the ass as they may need constant attention to keep them working right. Like I said Vette rears are really cool, but they can be a pain.

I think you will be much happier in the long run with a solid rear in your choice of flavor.

Originally Posted by mopar34

Tell him it was an early Father's Day gift.

The Vette rears look great and under some cars it really rides well. A lot of things must be taken in to consideration when installing one in anything other than another Vette. Specifications such as wheel base, body type (steel or glass) front/rear weight ratios, hp/torque/ rear end clearance, etc. must all be given consideration. If the setup and body weight is very similar to a Vette, then the ride should be very good. If the body weight is heavier and/or the weight over the rear is greater than it was on the Vette, then the ride quality may be less than ideal.

I have an all steel sedan, with a wheel base that is 16 inches longer than the Vette that the suspension came out of and the added weight over the rear suspension creates a less than perfect ride. Mine has the composite rear spring and standard vette shocks (not coil overs), so I may be able to improve the ride by switching out to coil overs. Not sure if the cost would justify the improvement. Also due to the location of the bat wing and gas tank there is no room for a rear sway bar, which would really help my ride control and comfort.

A couple of years back I had to have one of the half shafts replaced along with a new composite spring. Cost was over to $1200. Parking brake adjustments can be a real pain in the ass as they may need constant attention to keep them working right. Like I said Vette rears are really cool, but they can be a pain.

I think you will be much happier in the long run with a solid rear in your choice of flavor.

Thanks Mopar 34. Have you looked at Vette Brakes site? http://www.vbandp.com/detail.aspx?ID=379
They have a multitude of spring rates that may help you if you don't want to go coil-over. I spoke with them on Friday and they were very helpful.....he told me spring rates werent an issue as there were many to choose from.

Also...can your sway bar be mounted in this way? On the backside of the support bar for the pinion? Scroll down nearly to the bottom. They have some good shots of the swaybar for the rear. http://temp.corvetteforum.net/c5/ric..._Project.shtml

Another alternative for the swaybar that I've seen is passing it through the frame using say, 1 5/8 tubing welded within the frame, with the swaybar passing through and adjustable arms on the ends (which are splined). Just a thought.

Thanks for the input on this. I think this will be better suited for my dad's car. He has more room to work with. My gosh....you could literally put the bathroom sink in the back of the 41. The trunk is huge!

Thanks,
Dave