Q for MDJay, others - any Heidt's rear IRS installs?

(besides Reenmachine, that is, it's all up there on his thread)

Just wondering if there are any Heidt's rear IRS installs that are completed, with final ride impressions, etc. I'm wondering:

-Ride vs. handling

-Clearance for larger tires depending on track width you choose?

-Quality of the brakes?

-Maybe most importantly, ride height change? Do they raise or lower it (I should probably check Reen's thread on this) and how much room for lowering is there?

I know Mustang Depot is starting to sell these and that MDJay was hoping to install some soon, so I'm looking to get some impresssions. Yes, I know that something has to be fabbed to mount the forward support a la Reen . . .

Thanks, tons of info

Brad,

Yeah, when you think about it - rear housing, gears, coilovers, brakes, it's a pretty good deal because it rolls a few projects into one.

Great job on getting everything installed there, I'm impressed. It sounds like, without the fab skills, the tools, or the room to get it installed that I would be incurring some pretty heavy labor costs.

Believe it or not, that backspace issue might be a dealbreaker for me. I've already got my wheels and tires done (17x9, 5.5bs, coy's c-67 edelbrock copy) with a 275/40/17. If you're saying 4.5 or 4.75 bs is the most, looks like my project would be dead in the water.

I was going to go the composite springs route as another option - that, and a Maier new-style panhard rod kit. No need for the torque arm until I get to the engine. But then the cost of rear discs on top of that . . .

The last one, more for dialing in the "stance" and for ride and after I finally read a few ride impressions saying it handles well, would be the Air Ride Air Bar 4-link adjustable air shock system. But at $2k, and then on to rear brakes, still not a bargain, and there's nothing IRS about it . . . still, tire clearance would seem to be maximized and the adjustability would be pretty sweet. A narrower rear could be put on later, but since mount ears have to be welded on to the axle I would have to order up another set of mount ears later on, not a biggie.

Looks like this might turn into a general rear suspension thread . . .

Thanks for all the info, I hadn't heard/thought of the backspace issue,
Joe

mustbereel said:

Hi 70 Vert,

I am in the process of installing a Heidt's IRS in my 65 Fastback. I bought the IRS from Mustang Depot and have been following Reen's progress as inspiration. Although my car is far from complete I have learned much so far that I am happy to pass on.
This install is very fab heavy. There is nothing "bolt in" about it. Good fab and welding skills are a must. That being the case you can mount it in such a way to get just about any ride height you want. I notched and reinforced the rear subframe where the Heidt's IRS mounts to match the pinion angle to my TKO500. I modified my TCP subframe x brace to attach the forward struts. Even with many measurements taken I still managed to mount the IRS a little bit crooked requiring some rework.
I thought I would gain some clearance for larger tires by eliminating the leaf springs but the bracket for the foward struts limit the amount of backspacing you can use. I found that on a 17" rim the max bs is about 4.5-4.75". In retrospect I should have gone with one size smaller track width and used less backspacing to allow for more tire. As it is I am going to use 9.5" rims with 275/40/17 tires. I modified the outer wheel housings to give about 1.5" more space.
The only thing I haven't figured out yet is where to run the exhaust pipes. I want to run the pipes all the way out the back and between the various struts and crossmembers there isn't much room for pipes. There really isn't much room for side exiting exhaust either. I will probably find a place to route the pipe to the back and mount the mufflers beside the gas tank.
I don't know if there will be a significant improvement in ride and handling vs a solid alxe. My other choice was to go with composit springs, aluminum 9" housing and torque arm. Belive it or not the Heidt's IRS is significantly less money since it includes everything from hub to hub.

Wow, this was a long post. It's just I've been working on the car all morning and it is fresh in my mind.

Brad

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Thanks B, I am driving myself nuts on this . . .

(apologies for length)

That seems like a promising kit, but I'm at a loss as to how they are going to do a 3-link without cutting up the backseat floor. I would buy it if it were a 3-link that worked w/o surgery. And if they go 4-link, well, I've pretty much convinced myself that the only viable 4-link without a lot of bind is the Satchell angled-lower-arm 4-link. I would hate to get my money into it and find out that they go with a non-Satchell 4-link.

Obviously I've been spending some time over at corner-carvers. ;-)

I am surprised that they are promising easy exhaust routing - maybe with just the Watts but if you look at the sta-bar, it's a jungle gym back there.

If 66gmachine on this forum had a shipping kit that was more than a CNC drawing at this point, (he has a Satchell design, and I just resurrected his thread, check out "tri 4-link" on the first forum page, and especially the photo I dug up from corner-carvers.) I am wary about 66g's upper shock mount points, as I have not seen anything - I don't think you can expect the coilover spring-plus-shock to mount to the same place as the stock shock, it's just slightly reinforced sheetmetal. Before I commit to anything I would want to see the upper shock mount. Plus, he intends it for 65-66. Once again '69-70 is the redheaded stepchild. (apologies to '71-73, you got it worse) amnit:

I know exactly what I want, it's basically this, with a stout front crossbeam (since it needs to resist braking forces AND locate the rear axle) and some rigid bracket to mount the upper shock to that contacted at many points including the frame rail - hell, I'd fill that crossbeam with structural foam and reinforce the driveshaft loop too just to be safe: (I just don't want to give up my life to designing and building a rear suspension that works for the 'stang) I probably sound stubborn about this, but the guys at Corner Carvers, wiser by far than I, have more or less come to a consensus on this . . .

(I am currently stressing on this bit as my rear end is sitting too high and my subframe strategy is stalled until the rear gets sorted out, and I have a little chunk of change to spend. Until I get this sorted my rear's up too high and the car is flexy, and I don't want to have to pay to do it once then do it again . . .)

bnickel said:

70 vert, check out

http://www.evolutionmsport.com/evmCart/index.php?main_page=product_info&cPath=22&products_id=38

they are about to start production on the watt's link and the rear stabilizer bar and the rest of the rear suspension should get going good in the next 2-3 months i would think, not sure how long it will be until it actually gets released, though. they are going to be doing either a 3-link or a 4-link and i think they are leaning to the 3-link right now. it should be a bolt in system with tubular control arms and should still have room for the exhaust to go out teh rear. i would hold off making any final decisions for at least a little while, you might even contact them every now and then just to check the progress. i think this is going to be the most promising rear suspension setup to come out for an early stang to date. i will probably be going with one of these myself eventually.

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Here it is, the Aussie 3-link

http://www.rrs-online.com/html/new_products.htm

The subframes look kind of spindly, and I don't see if the shock has some kind of reinforced mounting point to the frame, otherwise, pretty cool, good price. Wonder about shipping costs, though . . .

Do you mean just the airride shocks?

65,
Do you mean the airride shocks or the whole unit? The unit is a whole cradle that goes up inside your rear frame rails and is a 4-link with short UCAs and longer LCAs, kind of like a modern Mustang 4-link. Which has its' problems.

Never thought of airride in an IRS. Could be cool. You might get some weird camber when you drop the shocks below what a coilover is capable of . . .

65mistress said:

Jay

Would the Airride setup be just a bolt in at the point after the welding with that rearend?

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dump the rear for the 'hood look.

mdjay said:

(snip) Trust me I have considered the ART shockwaves the entire time. If nothing else, getting it on and off the trailer.

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and for me, Air Ride rears would help me fit in in Oakland. Whenever I'm going through the 'hood, just dump the rear and drag my rearend, that's the look around here. That and dubs with spinners.

Wow, can't wait to see it!

Mike,

Thanks for clearing up the exhaust routing question. I'm curious as to where the torque arm will be relative to the pumpkin (I know you're still making the final determination) as I've seen all sorts of different designs, from solid below the pumpkin to decoupled above the pumpkin, etc. It seems that with a low center link, you have to reinforce it like the RRS-Online guys have done:

http://www.rrs-online.com/html/new_products.htm

with that cool ladder-style arm. But if you can get the arm above the pumpkin, it can be simple and do its' job. But then it seems like it has to intrude into the backseat.

My brain hurts. My hat's off to you guys, this is tough stuff to get your head around, much less manufacture a unit that works on a wide range of cars.

Evolution said:

70vert,



It will be a Three Link. As for the floor, there will be no surgery. If there are issues with the floor, we can always offset the link to one side. We will make the final determination on the center link, once our Watts Link is in production form (a few weeks from now).



Not sure if we ever said easy We have more room with this watts than our current one, and we are able to rout the exhaust through. The stabar is not the problem. The problems are usually centered around the axle towers.


Thannks...Mike

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