Hello guys,

My dropzone springs recently arrived, and I am about to get them put in the IROC, but just had a few questions first.

The springs themselves, are advertised as a 1.75" drop on both the front and back. Is this going to be less on the IROC, seeing as they most likely did the measurement on a normal Z28 model? (i.e., how much lower is a stock IROC then a stock Z28?)

Also, somewhere down the line I know I need to install an adjustable PHB (to center the rear axle). Is this something I need to get RIGHT away? Or can it wait a few weeks? (I daily drive my car, but I don't race it or anything...).

Thank you very much.

 

The V8 cars had V8 springs, the V6 cars had V6 springs - no difference in stock ride height between a Z28 and an IROC (all the IROCs were Z28's, but not all the Z28's were IROC's anyway).

With that much drop, you're gonna need the adjustable panhard rod to be put in with the springs - dropping that much your rear end axle will be greatly shifted (to pass side I think), and the car will ride funny, might scrub tires on pass fender, etc. I dropped only 1inch and I had to get an adjustable rod to recenter the rear. There's no need for the adjustable bars with adjusters on both ends (waste of money in my book) - just need one end adjustable - I think the Edelbrock rod is a fine piece and under or close to $100 I think.

 

usually ends up more then the advertised drop rate. dropping front and back looks nice!!
but you will end up with new draw backs.. lack of clearance..and Z's are lower then birds
harder to hook up when you launch!!
I left my rears stock.. this time.

 

Hello
I would suggest installing the adjustable pan hard bar when you install the lowering springs. To eliminate any clearance issues that are possible with having those specific springs. Like mentioned above seeing how the vehicle is a daily driver you will be just fine with a single adjustable pan hard bar with poly bushings to maintain a great ride quality. Below is a link to show you what I am explaining.

http://www.umiperformance.com/catalo...69l7h6h1mibq66

If you have any other questions feel free to ask.
Thanks
Brad

 

I'm not 100% sure and correct me if i'm wrong but in 1985 when the iroc-z was introduced it offered a .5 inch lower ride height as compared to the stock z28. Ive read this in several articles, including one of ours on TGO. Now I am not sure if they used this lower suspension on all the cars after 1985. As far as I know in 1985 the Iroc-z was 1/2 inch lower than the z28.

the 85' Iroc-Z also got delco-Bilstein rear gas shocks, special front struts, increased spring rates, special jounce bumpers, 5 degrees of caster in front wheel alignment, (up from 3.5 on Z28) 'WonderBar' front frame rail stiffener, special valving in the steering box for increased steering effort, larger rear stabilizer bar with stiffer bushings. That the z28 did not get. (This is all from the artical in our history section.)

Im not sure about the 86 and newer models though.

 

Could be then - I've never heard of it - but there's alot I don't hear about. At this stage in the game, anyone who has stock springs (even 1992 cars), there's going to be so much sag in them that any spring replaced is going to increase the ride height anyway for a few weeks until the new springs settle. When I dropped in my lowering springs, my car actually raised 1/2 in until it settled.

And 1.75 is about as practical a drop as you can make - anything much deeper and you won't be able to clear speed bumps, driveway entrances, etc. My 1in drop I still scrub the driveway, and some larger speed bumps in parking lots.

 

Thanks a lot guys!

I'll get the pan hard bar, and install it when the springs are going in.

Brad - I think I'll get that PHB if it's what you recommend, seems as though people on this site had good things to say about UMI.

 

Even on stock springs, stock tires, good shocks & good bushings everywhere....My 87 GTAs rear axle was offset to the drivers side by almost a full inch. Sometimes the car can get away with being lowered & never touching the PHB (my 092 RS & my wife's 90 RS both were that way).

 

Yea me too. Ive done A LOT with my car the few months Ive had it. early 350 build/swap, headers, welded up true duels, full brakes all around/master/lines, minor paint work and interior work, wheels tires. I have yet to touch the suspension, I'm still not sure what I want out of the car and how much I want to spend on a suspension, but I would like to do it all together.

My car has the original stock 85' iroc suspension I will say one thing it does handle very nicely for a 25 year old car but there is bounce more in the front and sag more in the rear. The spring rates I'm sure are shot. And stock the car scrapes the chin as well coming up my driveway. Not to mention I have to tuck my duals up more before I can think about dropping it anymore than stock.

I think the cars look great with the front dropped where the front fender meets the tire line and about a half inch of gap between the rear fender and the rear tire.

The previous owner had manual airbags installed inside the rear springs to raise it up :/ not sure why. The car had stock wheels/tires as well as the tired old 3054bbl it came with.

 

Great to hear! When you are ready feel free to give me a call and I will be more than glad to help with your order.
Thanks
Brad

 

I'm looking to get a set of those myself. I have a 4th gen LS1 rear, sticks out some on each side - if I load up for a long distance car show or something, I will bottom out on some dips - those air bags inside the coils would solve my issue without making permanent changes - just pump them up a bit and go!

 

If your tires rub, the problem is not in your axle, but in your wheels. What are you running? What is their bs?

 

Oh yeah - I understand that. I'm running stock twin-lined 3rd gen RS 16 wheels. The longer 4th gen axle makes them stick out farther. If I'm loaded down with luggage, coolers, etc for a weekend trip, on some of the larger dips in the highway I'll rub tires on the fenderlip with the Eibach lowering springs. It's not often, and only when I'm loaded down. For instance, 7hr ride to Carlisle, PA for the GM Nat's - I may hit 5-6 dips that rub.

And the wife and I like to go camping, having that gear in the car weighs it down just enough to rub on a larger dip. Don't have to worry about passengers - except the wife there aren't any - no one has ever sat in my back seats, and never will!

And I like the stock wheels alot. If I ever get cash to blow, I might consider chrome replicas, and in that case I'll get deeper offset to accomodate - but I don't see that happening anytime soon, thus I'm out in the 100 degree heat today sanding off the casting marks on my stock rims to polish them up.

 

you can correct that tire rub issue
I have a 4th gen diff.. when i installed my C clip eliminators..
you need to cut the ends slightly off the housing.. I machined my axles toward the flange to allow them to slide in approx 1.5 - 2.0 into the eliminator bearing.
to retain 3rd gen width.. with 4th gen rims

 

I'm lost on what your trying to say ... If I had 4th gen rims, I wouldnt have any rub issues. I have 3rd gen rims.

There's no way to correct the axle length issue without removing the axle tubes, having them shortened and reattached, and then using 3rd gen axles.

It's really no big deal - unless I'm loaded down, and that's only a couple times a year - I just drive more cautiously then looking farther ahead in the road for dips.

 

Get you a set of drag bags. That will stop the rubbing, if you inflate them when needed.

 

Yeah, that's what I was thinking.

 

the way I explained with the C eliminator.. yes you need to do a little fab work
no you don't need 3rd gen axles. the bearing is pressed on your machined axle allowing the bearing to pressed in farther AS I did..
you don't need to shorten your housing..
and yes if you have 3rd or 4th gen rims with a 4th gen diff installed in a 3rd gen car you will have tire issues