1.) What can be done to make my camaro not shake as much at higher speeds (besided wheels/tires and alignment)...is there naything else i can do (with in reason) to make it more steady?

2.) What was the biggest size stock wheel that ever came on a 3rd gen camaro? 16 or 17 inches?...any pics? thanks guys.

 

16's came on later irocs i think it was an option. you need a wonderbar to prevent your frame from cracking with 16's+ though.

 

why would the frame crack with 16 or 17 inch wheels?...i want to keep the aspect ratio the same, but i was thinking about getting 16,17, or 18 inch wheels with maybe a little wider tires, maybe 235's instead of the stock 215....

 

With 16's and upwards on the front, the frame would crack because of the higher stresses placed on it by the steering gear. The 16's would have a larger contact patch with the ground, assuming that you'd gone up in tyre width. So, more rubber on the ground = more force needed to steer = more stress on the frame exerted by the steering box. The wonderbar ties the frame into the frame on the other side of the car and dramatically cuts down on the flex by distributing the forces. Hope this helps.

My T/A had stress cracks and she's running 235/60 15's on the front

Mark.

 

besides wheels and tires you may want to look into having your driveshaft balanced or buy an aluminum one.

16x8 was the largest stock wheel.

 

Stock tire size for the 16 x 8 wheels was 245/50/16 not what you quoted.

 

How about not shake at all-

Carbonfiber driveshaft. Smooth as silk.

 

Just shake $700+ out of your wallet for a alot of overkill. This is a siock 305 TBI car.

 

If you do alot of higher speed cruising and driving then its plenty worth it. I do and I have a 2.8 V6 in the car. Mostly cruise between about 75 & 100 mph. Have maxxed this car out at 138mph(all she's got) but the car is smooth as silk with absolutely no vibrations at all.

Is it worth it- it was definately for me.
It used to shake like a bastard with the old stock steel shaft.

 

by stock i mean whats on my car now, which is the 215's...i might consider going up to 235 or maybe a bit wider (the 245 that you suggested) can someone post some pics of a wonder bar installed on their/a car?

 

I do alot of high speed freeway racing with my Z28, its pretty much what I built the car to do (not 1/4 mile). I've spent quite a bit of time trying different things out to increase stability, from different wheel/tire setups to different suspension setups and settings. I've got it to the point where 150mph runs are stable and the car is responsive enough to be able to handle the speeds with confidence. The main problems with the stock setup is the 50 series sidewalls of the stock 16's are too soft, the suspension is too soft, and the car is too high. I totally re-did the suspension with new springs, dampeners, and bushings. Off the shelf springs were still too soft for this type of application so I had to go custom. Correct suspension geometry is a must. Stiffen everything up and lower the GC and the car is much more responsive and stable at higher speeds. Sometimes you need to avoid certain areas of the road, or react to unseen conditions so you need as much responsiveness as possible. You need to eliminate any form of body roll, it will fight against you and screw you up. The biggest difference came from the wheels and tires. For top speed runs you dont want anything taller than a 40 series sidewall, the tires just wont be responsive enough. I was actually able to tell a difference between 45 series tires on 17's in front and 40 series tires on 18's in front. And of course an even bigger difference between the 50 series on 16's and the 40 series on 18's. My setup on 18's is within .03% of the OEM specs for the 16" wheels and I've had no adverse effects (245/40/18 front). Combine responsive tires with responsive suspension and you're good to go. The car still has the stock driveshaft, stock wonderbar, stock LCA's, and stock torque arm, and I have no issues with stability at 150mph. Ride comfort is a different issue, its definately worse than stock. Its a compromise and I went to the extreme end of performance, not caring about ride comfort. This is because of the speeds I have reached and plan to reach in the future when power and gearing are worked out. For now I've been focusing on suspension, wheels/tires, cooling, and brakes.

 

The wonderbar doen't prevent the frame from cracking. It supports the power steering mount from ripping out. Going with larger wheels doesn't mean you will have this problem. Lots of RS cars came with 16x8's and didn't have a factory wonder bar. It is a good mod none the less but I ran 17x9's for years on a lowered car and no wonderbar without any problems. If you are worried about the frame than you need a set of SFC's.

 

All depends on the suspension and tire quality. 245-50-16's are very stable at speed if you by good quality tires. Mater of fact I pefer to have a little bit of tire under me in the event you hit something abrupt at that speed, your rubberband tires are going to take 1 heck of an impact and so will the rim- not safe on street use where the roads are not kept clear of debris like a race course.

Also, if 15's are so unstable, why are NASCAR's running them up to 230 mph?
Becuae most people are trying vhigh speed crap on the wrong quality tires- don't skimp on spending hard cash on very good tires and 16" is better than an inexpensive 18" by far when it comes to safety and control.

Before anyone with 17's or 18's begin to argue with me on this point, let me first ask and you answer "have you ever bought ands ran a upper quality set of 16" tires that are high psi?" Most here have not. I ran my Goodyear GS-D3's at 46.5rear and 49 psi front ALWAYS (51psi max rating) and got 25,000 miles out of the with perfect wear. High psi tires are designed so that the psi helps stiffen the sidewall yet the integrity of the tire design does not cause distrotion of the contact patch- they are designed to run high psi and you should do so. Most people still only run 36psi in their tires because the door sticker tells them to

Its the reason why these current crappy BFG KDW tires I currently have on the car feel unstable at speed, they are only 44psi max tires, they only feel good up to 90 then you notice a slow deterioratiion in confidence as speeds increase above that. They are coming back off this car very soon- I bought them in a pinch because they were redily availiable and I based the purchase off of what others on here have said about them- wrong- they are crap.

 

Wow, I couldn’t disagree more (does that mean that I’m agreeing with dean? Not entirely but to a large extent I am…).

Have you ever been in a big boat of an old Cadillac at HIGH speed? They are actually nice and stable and happy well past 120 if there’s nothing wrong with them. No, they won’t handle great, but they are stable and happy, usually with tall, 70 series tires and a suspension designed for comfort.

THE ONLY reasons for bigger wheels with shorter sidewall tires to exist are to clear bigger brakes and for appearance reasons, because they’re popular. More side wall protects things but more importantly allows the tires to work at a bigger slip angle before they let go, making them far superior to a lower profile sidewall if you know what you’re looking/feeling for.

Where I will disagree with Dean is with running tires at the maximum inflation pressure. There are tires out there that have tall sidewalls that are plenty stiff with fairly low pressures. Indy cars and similar race cars run pressures in the teens and last I checked the circle track/nascar guys are all in the 20’s and low 30’s. I used to love some old school G15 hoosier racing slicks for autoxing and they really didn’t need more then about 26-28psi before they got so stiff that they felt like they were going to break your rims, then you just adjusted pressure to change slip angles and do some fine adjustment of suspension stiffness to adjust for track conditions.

High pressures do tend to work well on street radials, mostly because they were never designed for hard handling situations and the high pressures keep the tread flat/on the road, but this is often at the expense of braking and treadwear, unless you’re running a very wide rim for the tire size.

Well, there is a 3rd reason now for low profile tires, the low profile/big wheel look has become so popular that it’s hard to get good tire compounds and construction in 15’s (without going with real, race tires) and although decent street tires are available in 16’s, they are very limited in the sizes that are available (give me a good, high performance 265/50, 275/50 or 275/45 16 to run on the back of the car or make a set of some of the bigger 15’s in a good performance tire and I’ll be happy)

BTW, another fact, a stiff, big 15” tire/wheel will weigh much less then a similar 18. Rubber and air is much lighter then aluminum or steel. It’s not uncommon for even steel race rims + tires in 15’s to weigh in the 35# range where it’s pretty uncommon for a big, 17” combination to weigh less then 50#, and I’ve never seen a wider 18” come in at under 50#

 

And the answer is YES, I've run high quality 16" tires. I now run 17s all around and I'm considering 18s for the front (to clear the steering to fit 315s).

The problem with running really high air pressures is the tire gets so hard that it can't conform to the road's imperfections and will begin to skip across the surface. It will feel good up to the point it starts to push, which will come sooner than with a lower air pressure. Your also reducing the size or the contact patch so you have less mechanical grip.

The main reson that I went to 17s is tire width. It's hard to fine a 16" tire wider that 255mm, in 17s and 18s it's easy to find tires in 315-335mm widths.

 

No, Thats you have noises V8 car pushing the nose through the corners instead of turning. Thats why you had to go the wider front tires to get it to turn

 

You are not disagreeing with me on that point. We were not talking non radial racing skins that are unsafe for daily street use- So we 100% agree- Go figure

 

You guys can agree or disagree with me all you want. I've tried alot of different tires on alot of different wheels, and I personally feel that the lower profile tires are more responsive at higher speeds in this type of application. Before questioning what type of 50 series tires I've tried, ask yourself what 40 and 35 series tires you've tried. Forget the theory behind it, go give it a try and get back to me at which ones feel safer at 150mph.

 

CH, In general I will have to agree with you for the most part because there are only three 245/50-16 tires ever made that would be in the catagory I am speaking of, and one of them is discontinued due to customer distrust of Firestone products and lack of sales. The others are the Goodyear GS-D3, and the Michelin Pilot. But the Pilot is a very unpredictable and unforgiving tire on lateral grip so rule that one out (and its overpriced for what you get.)

 

my fulda extremos 245/50/zr16's held fine at 130mph... and seem to do well elsewhere

car\ handles high speeds well...very stable etc..... handles most situationsgood. very good tires

 

Believe what you want, learn for you self.

 

Here I'll fix my quote, My keyboard has been sticking and my typing is terrible to begin with...

-------------
"No, Thats your heavy nosed V8 car pushing the nose through the corners instead of turning. Thats why you had to go the wider front tires to get it to turn."
-------------

Then I will add...

because you are getting bad weight transfer and plowing, then trying to correct the dive with overinflation and then you are merely skidding forward instead of turning. Maybe you have never seen the chalk marks on my front tires showing my perfect tread scrub with 52psi in them while racing- and then look at the times I ran in comparison to all the other Camaros and Firebirds there.

When you learn to setup you car to perticular combination rather than hunting for larger tires for more grip to get it balanced, Then you can preach to me. If you want to run a V8 Camaro on 245/50-16's, you HAVE TO strip the nose weight or you are going to roll the tire at low speeds. And if you are overinflating any tire you are going to skid. Try that with your 17's and 18's, they do it also when overinflated.

Its just simple pyhsics that the shorter the sidewall the less roll in general when the same PSI is applied to each. HOWEVER, the higher PSI tires have a contruction design that allows them to run in the 50psi range and NOT DISTORT THE CONTACT PATCH- Thats the lesson learned here.

snip: I'd bet yoyu $500 bucks any day of the week my little V6 can take you out on an autoXcourse Axiod if we are both on race tires, or we are both on street tires. Learn for yourself also. I mean, how many competitors you got in Ohio running ESP? 3?

 

What the general makeup of low aspect tires is the car manufacturers have found a way to please the public by designing a soft suspension car that can be responsive with small sidewall tires. Plus they look great mainly to the ever popular crowd wanting 27" RIMS now-a-days- its a stupid trend.

Problem arrises when you put a stiffer suspension onto those small sidewall tires and the comfort ride quality becomes sh*t (to put it bluntly) They work great on very flat very smooth roads but g()d help you when you hit an imperfection.

Low aspect tires will make any softer suspension car that has weight transfer feel more stable and responsive at lower cush psi readings. Once you suspension doesn't move hardly anymore from building it radiacally, that low profile low psi tire NOW takes most of the absorbtion FIRST and hammers it into the rim. Race tracks don't have severe road imperfections, public roads do. Thats why you never see cars running around on low profile tires with very stiff suspensions unless its some riccer kid and watch him hit a bump next time- pretty entertaining.

A larger aspect tire will absorb high speed road defects because the tire will give more and bulge under extreme pressure and not bounce the car off the learger diameter rim like a bumpstop on a heavily modified suspension at speed- EVEN AT HIGH PSI- but retains a decent cruising feel a slower speeds still with the high psi reading.
This is hard to explain to people that have no experience with different combos. You have to drive many different combinations and have that experience under your belt to truely understand

 

Now with all that said...

"Whatts your worst enemy at speed?"

Answer-
road imperfections or debris in the road.

Its much safer to stick with an upperend tire with a little bit of meat on it (meat meaning not a rubberband tire)

Go to a dealship someday and ask a Mercedes mechanic how many cars they get back into there a year replacing low profile rims that were damaged in normal street use from road imperfections- you'll be amazed.

 

Low profile tires are more responsive then taller sidewall tires… no doubt. But any well built 15” or larger tire will actually respond faster then a human can react (forget assorted play and tolerances in the mechanical systems between you and the tire), and all that is happening is that you’re compesating for a suspension that is really too soft or too slow to react. Tighten everything up in the suspension so that it does exactly what you tell it to do, get rid of crappy, progressive rate springs, put proper shocks/struts on it and you’ll have all the response you need with the smaller wheel/taller tire combination.

Going the other way, well, will feels similar to a responsive suspension but will never be faster around the track assuming similar tread compounds. For one, 3rd gen suspensions are not tunable for camber gain and therefore you’re stuck setting them up where they work and then cutting down travel till you stay in a relatively narrow range where they do work (making softer suspension/stiffer tires worse then worthless), and like I already said, that taller profile tire can operate at a greater effective slip angle before it actually breaks traction, not only allowing it to work over a greater range of conditions but also giving the driver much more feedback when you start getting close to the tire’s limits.

My favorite combination was a fairly light V8 car (think everything unnecessary stripped under the hood, all the emissions, AC, assorted plumbing…) with 890# front springs and rear springs somewhere in the low 2xx# range. This car was actually very nice to drive on the street on 15” tires, and downright awesome on 15” race rubber. On a whim I tried some identical size/compound/brand/even the same rim design… 16” rubber at an autox and ran a consistent 2 seconds slower on them (2 heats, 3 runs each…)

I suspect if I had more time with that car I would have finally settled with front springs somewhere in the low 9xx# range and then reinstalled the harder rear bushings and shocks (ended up with rubber rear sway bar bushings… to balance the car out)

Simple physics basically states that if there is nothing to upset the contact patch it’s size has nothing to do with the available traction. A taller sidewall tire is generally more forgiving of things that would upset a lower profile tire’s contact patch, so you don’t need nearly as much of it.

If you’re running an appropriate pressure and you feel that too much of your sidewall is contacting the road surface in competition (white shoe polish on it will show you right away), then I would start with trying to add some negative camber. With good 15” tires and most 16’s I like something just over -1* (usually something in the 1.1-1.2 range), and with good 17’s something in the -.8-.9 range is more appropriate… in general 18’s aren’t appropriate for serious handling use). BTW, somewhere around that -1-1.2 range gets prefect tread wear on the street also, at least if it sees some aggressive driving.

No, they make people think “wow, this is SOO MUCH more responsive!” while the suspension is rolling around and doing all sorts of f’ed up stuff. There is a significant difference between a tire that doesn’t handle any issues at all and forces it all into a compromised suspension and actually “more responsive”

I have been wondering if tire manufacturer’s have thrown in the towel and have been trying to build softer sidewall low profile tires that still protect the rims. I know that the 17” Kumhos that I just put on my WS6 feel much more appropriate then the Eagle GSC’s, Nittos and Comp TA’s that were on there before, they feel a lot like a taller profile tire. Of course, I also already have one egg shaped rim that I replaced…

Again, if they’d just release a good compound/construction 15” tire in the bigger sizes that say something like the BFG Radial TA’s come in (I keep hearing noise that that tire is the newer firestone tire), or some of the good 16’s out there in wider sizes I would be happy.

 

Not to agree or disagree with anyone here. I was watching the race today (NASCAR) and they were showing the suspension cam.
At 126+ mph you could actually see the tire/sidewall move 1 1/2 to 2 inches when diving into the curves. It looked like the tire was going to seperate form the rim. Now I know they run very low tire pressures since pressure increases when the tires heat up. Anyway it was pretty cool to see.

 

that was an interesting discussion...can someone give me the stock tire size for a stock 16" IROC wheel? is it 235/60?...also, someone mentioned that the camber was not adjustable?...I thought it was...i thought camber, caster and toe are all adjustable on our cars

 

The actualy quote was:

You are right camber is adjustable, what he is talking about is the camaber curve on our cars is horrible, so to crutch that, you see people run crazy ammounts of negative camber, or the go with a really stiffly sprung setup, so that the suspension travel is limited, and thus the relative camber loss.

 

I understood what you meant the first time, which I took was a thinly veiled insult. We're talking about general tire handling characteristics, not how my car setup.

That last was inappropriate and your welcome to come into town anytime you would like. But I do not need to justify myself, what I know or how good I may be, to you.

 

Good points

I read a slalom test showing a 245/50 16 outperforming 275/45 17s and so on...

 

Yea, I don’t think that I’ve mentioned it in this thread (to lazy/tired to pick through the whole thing again right now) but a few years ago I got to run some identical compound and size 15 and 16” hoosiers back to back at an autox and found that I ran faster on all 3 runs with the 15’s then I did with the 16’s (and I ran the 16’s about 30 min after the 15’s, so if anything I should have been more familiar with the course…)

Funny thing is that I am _mostly_ agreeing with Dean here. The big/probably only difference is that I think that his tire pressure recommendations are foolish at best (why would something like my WS6 come from the factory with gsc’s rated at inflation pressures up to 44psi and have a recommended tire pressure of 30 psi if that was the case?), but that’s relatively minor since it is not hard to experiment with pressures under the actual conditions that you’re using them and find the best setting…

 

I think where we kind of dont agree is you're looking at it from a "which is faster" standpoint in regards to racing on a track and I'm looking at it from a "which one feels safer" in regards to blasting it on a public freeway at 100mph+. If you are talking about what is faster then you're right, the smaller wheels are alot lighter. And if its track racing, maintaining OEM height of the tire wouldn't really matter so you could run whatever tire you want. But if you're talking about what feels safer on the street at higher speeds, I say the smaller sidewall tires are safer mainly because they are much more responsive at speed compared to other street tires with the bigger sidewalls. Makes a noticable difference at 100+. And if you want to maintain OEM tire height or anything close and still run the smaller sidewall tires, you'll probably need the bigger wheels. I guess it all depends on the application, what you consider streetable, and how you prefer the car to feel.