Opinions irs vs watts link 4 bar question

[IMPALAMAN1]

im at a cross road... was talking with my chassis guy.. and he has a 2010+/- camaro rear cradle setup that he is willing to sell me. from rotor to rotor.

1968 impala
plans are for a high 600 hp 6.0 motor 4l80e trans. spirted driving with occational track days.


my current setup. has not even been driven on.
12 bolt series 1 carrier posi with 3:73 gears
4 bar
watts link. disc brakes

camaro setup
The good...... is obvious.
Factory big disc brakes.
Decent gears
I don’t have to worry about drive shaft angle
Off the shelf parts.

The bad
weight????
brackets/ alignment
Possible custom control arms
Possible custom axle shafts
frame rail cutting....
would be better suited for autocross


the good for the factory setup
already have the parts
85% completed on the chassis. need to mount shock brackets and final weld the watts link.
should work for both autocross/ drag pass

The bad if I keep the current setup........ I have a lot invested in the current setup with time and research/ not a whole lot of money but money none the less.
I would have to change the posi unit in the current rearend to a stronger one
Have to upgrade the rear brakes
Possible weak link in the drive train

So at min.
Im bigger brakes and a posi unit on the current setup.



I refuse to run pancaked rear wheels on an old car. so the shortening of the rear would be a must ( i have not compaired width yet)

[mikedc]

If you are really enthused about getting an IRS, then nothing less will ever really satisfy you, so you might as well go for it.

If you are on the fence, then IRS is probably not worth it over what can be done with a well-sorted live axle.


(I'm not saying there aren't benefits to an IRS - but it usually fails the cost/benefit test.)

[bergers59]

I would never do the irs if you have to the make control arms, and well...don't really know how to. I'm not referring to welding and making them but designing them to avoid wheel hop and proper toe in/out. A lot is different between a 2010 camaro and a 68 impala as far as weight distribution and suspension geometry. I don't think it's worth it for your application, but if you're dead set on it it will take some time to get it properly built/tuned

[IMPALAMAN1]

good responses fellas. the idea behind the drive shaft not being an issue with suspension travel intrigues me.

[silver69camaro]

The stock Camaro hub width is 66.8", so it's pretty darn wide. Just off the top of my head, a 10" wide rim will need roughly 6.5" of backspace to make that work.

In my opinion, narrowing that IRS is out of the question. It's not easy, trust me I spent three years on it.

IF you can find a way to make it work, hands down that suspension will provide a ride quality and drivability so far over and above a good solid axle design. Don't get in the mindset of IRS being a performance-only suspension, in my opinion the improvment in street manners are every bit as big as on track performance. Multilinks (like the Camaro IRS) are a very advanced design.

[cornfedbill]

The IRS should provide a better ride due to lower unsprung weight. However, that may not be your goal.

The IRS will weigh more overall. It may not hook up as well in straight line acceleration. A live axle keeps the tires parallel to the road surface under all conditions except when the road surface is very uneven, not likely on tracks and autocross.

If it were my car, I would stick with the 4 bar and watts link. I believe it is the better compromise.

[silver69camaro]

A live axle keeps the tires parallel to the road surface under all conditions

That's the problem with a live axle. With an IRS (at least a well-designed one) you have the ability to have 0 camber at the drag strip by alignment and shock tuning, and have camber during other others. Toe and camber control will allow you to get on the power earlier on corner exit when autocrossing. With a live axle you can't have that kind of flexibility - but it all comes at a cost of course.

[ChevelleNV]

Well you have two choices when it comes to the IRS, narrow it on the long side and make both side equal length and loose all the torque steer engineering that GM did, or modify the frame and trunk for it to fit at its current full width. I know this because I am in the process of grafting one into a 70 Chevelle. now you might not have to modify the frame if the Impala frame is wider than the Chevelle. It will take some work to make it fit, but well worth it.

[IMPALAMAN1]

Thanks Greg. cutting into the floor isnt on my list of to do's. ill be following along. thanks for the pics.

[j-c-c]

To me your big issue is, you have a thought out 80% set-up right now, vs a nearly start from scratch sloution that your builder wants to sell you, and all that entails. You can always add IRS later, or do it on another car, besides all the upsides of IRS, a bird in the hand, .........
From a guy who is installing an IRS from square 1 (CTS).