I have a 92 Z28 with a mildly cammed 355 TPI, a 700R4, and 4.10 rear gears and I can't get my car to launch worth anything. I have stock suspension other than a few polyurethane bushings and welded in SFC's, but I am indeed running the stock wheels with 245 width tires on them so that factors in quite a bit. I would like to know what suspension mods I can do to launch better, besides tires. I say besides tires because I have brand new kumho ecsta tires (not very good I know, but I bought them when I was pretty much flat broke and needed new tires). But so far I'm thinking maybe LCA's? I don't know what else I could do suspension wise to launch better.

 

That's your problem right there.

 

Yeah you've got like about a 12½:1 final drive ratio... guaranteed to give tires fits.

LCARBs would be the very first thing I'd try. ESPCIALLY if the car is lowered, either intentionally, or just by way of old age sagging.

 

i know you dont want to hear about it, but slicks are the best bang for the buck to launch.

i went through it too. glass hood, moroso front trick springs, moved battery to the rear, LCARB's, poly swivel control arms, beefed up torque arm, poly TA mount, etc, etc. even different drag radials. nothing will beat some good slicks, IMO.

 

I'd start by getting an adjustable torque arm and relocation bracket. By doing so you can adjust the instant centre of your car and better control your launch. The relocation bracket will stop your tailshaft from failing during a hard launch too.

BMR, UMI and Spohn all have solutions for your issue.

 

It's a complete package. One thing will help a tad but everything helps a lot more. The factory parts are thin stamp steel that flexes.

Here is a few things to think about and get.
Limited slip/posi/locker rear end if you don't already have it.
Aftermarket adjustable torque arm
Lower control arm relocation brackets
Aftermarket lower control arms
Drag bags in the rear springs
Adjustable shocks
Good drag radial tires or slicks

 

NITO DRAG RADIALS

 

Thank you guys, so I guess the biggest things I need to do are LCA's, LCARB's, and torque arm? I do have a posi rear end already fortunately. But essentially I'm not gonna be able to hook until I get some really sticky tires on the car?

Also at the moment the car is lowered due to totally worn out coils, but I plan to change those out for new moog factory replacement springs soon.

 

The most important thing, the one that should be done FIRST, is LCARBs.

Get a set of LCARBs. Now. Right away. Stop posting on the Internet, get up off yer keyboard, and JUST DO IT.

Reason for that is, the GEOMETRY of these cars' rear suspension is DEFECTIVE from the factory, and does nothing but get worse over time as the car sags. LCARBs move the control arm to the place it really ought to have been from the get-go: why it wasn't I don't know, but I suspect it had something to do with manufacturability (the bracket would have been too big to fit in some assembly fixture or something like that) as opposed to any kind of deliberate "design" decision.

If the car either wheel hops, or if it squats and fails to hook at all and just immediately goes up in smoke, then LCARBs are the first line of repair.

Stock LCAs are SO WEEEEEEEEEEK you can pick em up and bend em and twist em in your hands. (at least, I can, in my hands, anyway) Needless to say, ANYTHING in a suspension that doesn't stay in the same shape it was meant to be, adds an element of TOTAL unpredictability and looseness to the whole thing. I put the real simple cheeeeeeeep Lakewoods in mine; made a noticeable improvement, but it was before I wised up and figured out I REALLY needed LCARBs, so the car was still not right.

Same for the torque arm. I put one of those in my car, again before the LCARBs, and it made a YUUUUUUJJJJJJJJJE improvement; felt like I had just take a giant rubber band out of something and replaced it with something solid; but the car still didn't hook. Then when I put LCARBs on it, it was REVOLUTIONARY.

Get a set of LCARBs.

Did I mention, all those other things are GREAT as far as they go, but THE REAL MALFUNCTION is the CABs? In case I didn't, THE REAL MALFUNCTION is the CABs.

Get a set of LCARBs.

 

Are the Hawks Sinister bolt in ones any good? I'm just about to order but I want to make sure I'm not ordering junk first. They're about $90, and I know there are weld in LCARBs, should I get some of those instead? It's just that if I get weld in ones I'll need to have a shop do it, but bolt in's I can do myself.

 

No idea about those particular ones. But bolt-in in general won't cut it over the long term.

However, you might be able to get some bolt-ins, bolt em in, and drive em somewhere (exhaust shop maybe) to get welded. A place that could set up for a 4-wheel alignment while welding, would be ideal.

Making sure they're on STRAIGHT is the most important thing.

Some years ago I got my "ideal" rear end core (91-92 w PBR brakes); tore it all the way down; and had the tubes welded up since they leaked like every other rear does and were loose in the pumpkin, and the LCARBs (Spohn) welded on at the same time. I had the guy use a pipe and cones to make sure the tubes were welded on straight, and a rod through the LCARBs to make sure they were straight, or at least the same on both sides. Then had the housing powder coated, put an Eaton posi (NOT a Gov-Bomb) in it, the stock gears for my car (3.73), new better-than-stock axles, and a T/A girdle cover.

I was not prepared for how much difference they made in how the car hooked up. I expected some sort of incremental, "just noticeable" kind of deal, like when I put a wonder bar on the front. WRONG. The difference was ASTOUNDING. I shoulda done that 15 yrs before I finally did.

 

Okay, I'll order some spohn weld in ones since they would match my SFCs anyways and I'll take it to the same shop that did my SFCs. Thanks!

 

http://www.bmrsuspension.com/?page=p...416&superpro=0

 

Tires are your problem.

Lcarbs wont help if tires cant hold track

You need a mickey drag radial 255/50/16

If car is lowered abit, lcarbs to correct lca geometry

Then get adjustable shocks

 

4.10 gear really needs a 28" tall tire (slick, DR or anything but a street tire), more footprint and helps kill a bit of the gear.

 

I just ordered some Spohn weld in LCARBs, but as soon as I can I plan to get some different wheels and run some toyo r888s because this is a street car that I drive quite often and I know the Mickeys don't last very long at all. I mean, I could get a set to run just at the track, but since my track is about an hour away I don't really go that often.

Taller tires would help as well but I would like to see where I could get running close to my current height tires.

 

Biggest single change I made was a set of drag radials. However since you asked "besides tires", the LCARBs (mine are Spohn along with the SFCs) helped. After that I went with air bags. The move to a drag racing orientated strut and shock didn't appeal to me as mine was more street and cross country than anything else. I just wanted some consistency (and respectability...still looking for that) at the strip.

 

The street drag radials last a fair amount of time. I got over 6k miles on my mickey 19's and alot of burnouts and they still have half tread. I used to daily drive 10k miles easily on nitto drag radials. The 555r are so so drag radials but the nt05r is awesome

I dont think those r888's will be any better than what you got and being a soft tire they still will wear fast

 

Hmm, reviews I've read have showed the nitto drag radials to have fairly okay tread life but not so great traction, and the flip for mickeys. I've heard great things about r888's when it comes to both. Obviously tread life will not be that of a street tire, and same for wet traction, but it is true that I have never used any of those tires. I do think that as soon as I can, I'll give the R888s a shot, and if those aren't what I want then I'll keep using them until they're done and then I'll switch to either the MTs or Nittos.

 

I have not used r888'sbut they are a stiff sidewall road handling tire. That is not a drag construction. softer sidewall is what you want

Mickeys are not a good wet tire, neither are nitto nt05r.

555r are ok drag and a great street tire in all weather

I have run mickeys, both nittos, and a few different street tire compounds.

 

So what would you recommend for daily driving my setup as well as running it at the track once in a while? The MTs with different psi for street and strip respectively? Or something else?

 

I think with your mild build any good street tire will hook up once you've got your chassis figured out. Getting the instant centre sorted out with an adjustable torque arm, then doing LCAs and LCA relocation mounts will make a huge difference and likely let you get a good launch on a non-slick tire.

If you are doing the torque arm make sure you get it off your trans with a relocation bracket.

 

If you put on sticky tires but don't fix the geometry (usually w LCARBs), the car will likely wheel-hop so bad it'll break something.

It's kinda all gotta work together as a system...

 

This ^^^^

 

Okay, so my current plan of action is to install LCARBs, then aftermarket adjustable LCAs, then a torque arm (with the relocation bracket), and then maybe by the time all that is done my current tires will be worn enough to justify getting some MT ET streets or something. Sound good? Anything I should add?

And I'm guessing an adjustable panhard bar doesn't help much with traction but should be installed at some point anyways?

 

That will be more for re-centering the rear end. If you raise or lower the body the differential will no longer be centered, hence the need for an adjustable panhard bar.

 

I run the Nitto 555R 275/60-15 on my car. It was a true daily driver for years. I got about 12,000 miles out of the tires and that's with almost every weekend at the track, plus daily driving.

As already been said. The suspension is a system.. This or that, helps but the sum of the total is greater. I don't have my detailed track logs anymore but like most of us, I built my car on a budget, so that meant long time frame between this or that being bought and installed.

Of course I built the engine 1st, after that, without doing anything to the engine, the car went from a high 13 second car with 2.50s 60' times spinning to the 1/8 mile mark, to a 11.40's car with a 1.60s 60' time.

Here is the order in how I done mine and parts I used.. Not the right way or best way but it was the way things happened.

Yukon axles, powertrax locker, TA support cover
Spohn SFCs
Spohn LCARBs and adjustable LCAs
Moog Iroc rear springs, KYB AGX adjustable rear shocks
Nitto 555R drag radials
Spohn adjustable panhard rod
S&W 10 pt. roll cage
Lakewood driveshaft loop
Jegster adjustable saddle mount torque arm
Air lift drag bags
Battery moved to rear of car
Ford 9" rear end

 

So I just slowly build up my suspension at what I can afford over time? But basically it is the more I have done, the better it will do than just picking some stuff?

 

Couple of things and perhaps someone will tune me in if I'm wrong.
The adjustable torque arm isn't for adjusting the "instant centre". It's for the adjusting the pinion angle so as to get the u-joints properly orientated. At least that's what the adjustment at the differential is for. When LCARBs are installed, it effectively rotates the axle and pinion upward and that angle needs to be addressed. To change the IC, the point at which the torque arm connects to the transmission or cross member would have to relocated. Isn't that correct?
And I'm not certain what the advantage of an adjustable lower control arm would be other than centering the tire in the wheel house (front to back).

 

As it was explained to me, the torque arm angle does affect the instant centre of the car. Raising or lowering the front bracket of the TA affects how the car lifts or squats when holding torque on the brakes before it launches. My TA is non adjustable so I tune the cars handling by raising or lowering the bushing and clamshell on the front relocation bracket.

 

Yes. That is true. Moving the front of the torque arm (at the trans or cross member) will move the IC. The same is true of making a move to a shorter TA such as the Jegster or similar where the forward point is further rearward in the trans tunnel. However, in an arrangement such as my own, there is no adjustment at the front. Only the at the point at which the TA attaches to the differential and that is only for setting the proper pinion angle. It will no effect on the IC.
Just a clarity thing.

 

You'll most likely be breaking some component of the 10 bolt so purchase some bolt in relocation brackets that you can weld onto a better rear end whether it be a 8.8, 9" or 12 bolt. Buy the tires recommended to you when the current ones get low. There will be a memorial day sale from UMI and BMR and maybe Spohn, usually 10%. Founders is the least expensive but they usually don't have sales. You should be able to buy the lower control arms and panhard rod as a package. Buy the Torque arm package on a 4th july or labor day sale too. I wouldn't change gears until you break this rear end. I've never broken a rear end but I've heard enough and seen enough of stock rear 10 bolt breaking with slicks and decent suspension with only 300 horsepower.

 

Skinny, you are correct: adjusting an adjustable torque arm, in the stock configuration (e.g. Spohn), ONLY rotates the rear end housing. It DOES NOT change the instant center.

LCARBs on the other hand, DO change the instant center.

In the suspension design we have, the instant center is at the point along a vertical line through the torque arm clamshell, where a line through the LCAs intersects it. Ideally, you want to set the car up with the instant center somewhere close to a point along an imaginary line between the tire contact patch and the center of gravity, which can usually be guessed as somewhere close to the shifter ****. Maybe not exactly along that line, but get it somewhere close, then kinda tune from there.

With the stock control arm angle, which had the rear of the LCA about ½" above the "frame" end, the instant center in factory trim was about a foot too low, near the floor of the car somewhere. Lowering the car further just sodomizes the angle even more, and can put it a foot or more below the pavement. This makes the car squat something awful - literally trying to lift the tires off the pavement for a period of time until the car can fall down far enough to put some weight back on them - which is where the wheel-hop and/or up-in-smoke situation comes from. LCARBs allow the CA to be pointed upwards slightly. With the rear of the CA about ½" - ¾" below the front, the line through it intersects the vertical line through the TA mount at about the right place for "neutral" suspension operation. Lowering the rear of the CA even FURTHER can literally DRIVE THE TIRES INTO the pavement on application of power, by LIFTING the car instead of making it squat (aka "anti-squat"), and can thus actually be carried TOO FAR for ideal operation. You can get it to the point where it's TOO violent, especially with a stick or with a trans brake.

Also keep in mind that the rear's behavior under braking is the opposite of its behavior under acceleration: if acceleration makes the rear squat and wheel hop, then the rear will tend to raise under braking; and vice-versa. You can thus make a car wheel-hop on the brakes BAD by getting carried away with lowering the rear of the CAs.

That's speaking strictly about the STOCK arrangement. Different aftermarket ones, with their different adjustments and whatnot, don't necessarily work the same.

 

Precisely the result I was experiencing prior to making a few suspension changes. Even the addition of the LCARBs wasn't enough to get past the unloading of the rear tires. I'm probably an inch to an inch and a half lower than stock which is of no help whatsoever (except for the cool factor). It's evident in some of the videos of my launch. It wasn't until the addition of the air bags where I could A) preload the suspension to some degree with 20 lbs right side and 15 pounds left side but probably more importantly ( I think) was B) raise the rear of the car thereby changing the IC to something that was workable.
At least that's what my findings were from testing last season. I managed to get my 60' down from an embarrassing 2.x to a somewhat more respectable 1.8. There's more in too as I had a PB of 1.71 a few years back when the ET Streets were fresh.

 

I think the torque arm mount height has very little influence on instant center, whereas the torque arm length has a powerful influence on instant center.

To the OP, you really need to dial down your rear gear ratio. Not only would you leave the line better, but the car will be quicker. The TPI doesn't have lungs to rev and your gear ratios are making the engine spend time in an upper rpm band that it doesn't work well. You need to cause the engine to spend more time in an rpm band where it can perform.

 

Thats if the geometry is off. that only seems to happens on severely lowered cars. I would definately recommend atleast bolt in ones since they are easy to install tho but if its somewhat stock height, the cars work well.

In all my testing with 4th gens and 3rd gens of various suspension setups, i never had one wheel hop. Also havent seen lcarbs make huge changes on stock suspension cars at the dragstrip but does make a feel difference around corners. If its lowered then it seems to help bring it back to stock like geometry or abit better.

All setups are different tho i guess, your mileage may vary. Test away

 

But don't you think that if he puts all of our other suggestions to use--He now has a suspension and tire setup that affords him traction--that the ten bolt becomes a big question of its not if but when? I think you are absolutely right about the gears but it might be better financially to put the money for a new gear set towards a better rear end.

 

Yep I can say for sure the rear end will become a ticking time bomb. I broke 2 of them. Then got smart and put a ford 9" in.

 

It's hard to tell. Auto trans with low stall speed and not a lot of power.... doesn't sound too bad. Biggest risk in my mind is the 4.10 gears that normally break like a pretzel. If he had stayed with a lower gear set then it would have been stronger. A differential cover with bearing cap supports will help.

 

The gears are actually Richmonds so they are a bit stronger than stock and I have a TA cover with fresh bearings in the rear as well. Also I don't really plan to up the power level too much, the only other engine component I may change in the future is the intake, I don't have any plans to do heads/even bigger cam, etc.

To everyone else, so basically these cars just have pretty much junk suspension setups from the factory and I should change pretty much all of it? Getting suspension dialed in as well as some sticky tires will probably get the car to leave like it should if I'm right.

Also, in my last 1/4 mile run even without being able to launch worth anything at all (about a 2.2 60), I still ran a 14 flat so I think I should be able to get a pretty respectable time out of my setup if I could launch better and do some tuning.

 

My original chassis had a BW 9-bolt and it wasn't until I made my first 12 second pass (12.9x) with a 1.78 60' (all new personal bests due to the new roller cam) that the pinion got a couple of teeth knocked off. Is the 9 bolt stronger than the 10? It depends on the 10 I would say. That suspension had LCARBs, boxed lower control arms, a UMI torque arm and old BFG drag radials.
As far as the suspension is concerned and it being junk, yeah, pretty much when you start pushing the performance envelope. And the faster you want to go, the more it takes.
All things being equal, at the ETs were talking about, it's said that a tenth in the 60' is worth a couple of tenths at the stripe.
You may find that all you will need is a fresh set of drag radials to get you to stick. Bolt in a set of LCARBs and I bet you can get consistent 60's.

 

Yeah, I'm fairly certain my rear will be okay for what I'm going for, but suspension I feel like should really all be done at some point regardless of power level due to the torque that an L98 makes. I have weld in LCARBs on the way right now, and after that I'm still going to do LCAs and new springs all the way around (I know it doesn't help traction, but mine are totally worn out). I'm going to get some ET streets as soon as I have the money for new wheels and tires, but it will be okay because I'm not gonna hit the track until I get them.

And if my rear does for some reason give, then I guess I'll be saving for a 9".

 

I'm currently running on a used up set of ET Street bias ply tires. When I started shopping around for a replacement set, I found that particular line has been discontinued. The replacement is the MT Street S/S.

http://www.mickeythompsontires.com/s...tem=ETStreetSS

It seems the radial is the way to go. That's long been the consensus opinion regarding bias ply vs radial anyway. The proof is in the list of suggestions in the earlier posts in this thread. Seems the bias ply tire is geared more toward the stick shift crowd.

 

This thread is getting silly. A 14 second car does not need a set of ET Street drag radials. Get some shocks that aren't worn out, drop brackets, box the control arms and go have some fun. I would also make sure the torque arm bushing is in good shape or replace it. You don't need the thousands of dollars of other stuff. Will you dead hook? No, but it will work decent.

 

Silly or otherwise, even when my heap was running 14's, then 13's, the tires made the single biggest difference. The suspension would still unload initially (no LCARBs) but the tire would hook up a few feet out. With street tires, I could spin well past the 60' mark.
That's just my experience though. Other's may be different.

 

My shocks are fairly new, my torque arm bushing is most likely worn out though. I'm ordering new LCAs tomorrow and I have LCARBs on the way already. Right now I can most definitely spin my street tires well past the 60' mark and I don't think that just suspension stuff is going to fix that. I have BFG G-Force Sport Comp 2's.

Whether or not my car needs drag radials based on its time alone is clearly not going to make it look like it needs them, but it is still a TPI with a 700R4 and 4.10 gears, therefore it is making gobs and gobs of torque at the line. Granted that torque goes away probably right around the eighth mile, which is all the more reason to need them. In my car the launch is everything, if that car can't get off the line, then it's getting a crappy time because that's where all of it's potential is at.

I have that spinning past the 60' mark problem right now.

 

i suggest you get a spare set of wheels. buy a set of used slicks off a buddy or somewhere. that is the absolute best way to get good traction.

i do agree that everything else should be in good working order, condition and geometry.