Hello,

I haven't posted much but I have an 86 SE with a 3.4 izusu swap . I'm working on replacing/upgrading original suspension components to tighten up the handling. So far I've replaced the rear control arm bushings, ball joints, installed Rodney Dickman aluminum cradle bushings and adjustable coil overs last winter along with the engine swap. This winter it's time to address the front end. I'm now running 18" wheels and the stock brakes look tiny behind the large open rims. I've acquired a set of corvette rotors and calipers to fill out the gap and improve my braking performance ( 13" C5 vette front rotors and 12" rears). With the 18" wheels I'm riding at least an inch over stock ride height and the height and fender gap just ruins the stance.

I've read about issues with using lowering ball joints along with the corvette brake upgrades. I purchased a set of Rodney's lowering ball joints before the brake kit. I also have a set of Eibach front lowering springs.
I'm looking for advice as to how to lower the front end without causing interference when the 13" corvette rotors and calipers are installed. Most of what I have read on the forum has been for an 88 setup, with little on the 84-87. Where should I look for interference, what is the preferred method to lower the front end with a corvette brake kit and what modifications are necessary to use either lowering springs or ball joints with the vette brakes?

Ultimately I'm looking to bring the car back to at least stock ride height while sitting on the 18" wheels, if not a little lower. Ride quality and ease of installation are considerations but I'd like to understand all the options to get there.

Thanks

Bump.

What size tires do you have on there? 255/35-18 would be almost exactly the same as the stock 195/70-14 tires/wheels. 225/45-18 would be the same as the 15" wheels on the GTs.

Yeah rim offset numbers would matter too.

I will have to check the size of the tire and offset tonight, but as measured from the body to the ground the car sits about an inch higher on the 18" wheels I now have. Previously the car had 205/60/R14's I believe, on the stock 14" wheels.

What I am most concerned with is clearance between the brake rotor and caliper, to the suspension. With the 18" wheels I should have no problems with the brakes clearing the wheel, correct? My understanding is that lowering the car through Rodney's ball joints will alter the suspension geometry such that the larger rotor/calipers may contact the suspension throughout its range of motion.

Only the 88's have to be concerned with clearance to the lower a-arm nose. The 84-87 has inches of clearance in this area - especially if using the shallower 13" C5 rotor.

This is a 12" C4 rotor on an 84-87:


Here is the same rotor on an 88 that has had the nose trimmed to provide the needed clearance:


The area where the 84-87s have interference is between the caliper and the shock... depending on caliper, amount of lowering, and rotor application.

[This message has been edited by fieroguru (edited 03-16-2016).]

quote Originally posted by GotScooped: The tires are 225/40/R18

If you had 205/60-14s on the stock wheels, those were 1" diameter less than stock (so car would have sat 0.5" lower than stock), and your current 18" tires are 1.5" larger than that, meaning your car is sitting about 0.25" higher than stock (or 0.75" higher than the 205/60-14s).

225/35-18s would put your diameter 0.5" less than stock, so ride height would be 0.25" lower. I don't know how wide your wheels are, but 245/35-18s would be the sweet spot for closest to stock diameter for an 18" wheel.

If you then want to lower the car to close the wheel well gap, then ball joints or springs are probably the easiest options on the 86. I don't know about interference with the 13" brakes with the ball joints though.

EDIT: Looks like fieroguru provided the clearance answer while I was typing.

[This message has been edited by dobey (edited 03-16-2016).]

quote Originally posted by fieroguru: The area where the 84-87s have interference is between the caliper and the shock... depending on caliper, amount of lowering, and rotor application.

And the location that the mounting bracket places the caliper. DoubleC4's mounting brackets are nicely designed because the clock the caliper up enough that it clears the shock mount just fine.

I have 2 87 GT's, both lowered and both with big brakes. One has 12" Corvette rotors with 88 Fiero calipers, and it's running cut springs. My other 87 has 13" C6 calipers with DoubleC4's brackets, with Rodney's lowering ball joints, but I am also running different hubs on that car, so I don't know if that comes into play. No clearance issues with either setup.

I believe the 88's are the only ones with clearance issues when lowered with big brakes.

[This message has been edited by zmcdonal (edited 03-16-2016).]

Thanks for the replies. That picture really helps guru. I willinstall the drop ball joints and springs and see how things look. If I do end up with problems with the shock and the caliper can the shock mount be shifted within reason? Thanks, I'll update when I get parts on the car