Hi all,

Something that is worrying me is the instability that I feel when I am going 70-80 mph on a freeway transition that has some bumps to it. It seems that when I take this transition at 60-65 mph it does not react the same way. Are the stock shocks garbage for high speed cornering?

My 1995 bmw M3 takes this transition easily at 80 mph like its on rails- it has a simple bilstein/ h&r spring combo.

Maybe its time for some coilovers for the vette or should I just get fresh shocks?

- Concerned noob

 

The stock suspension and tires will provide amazing levels of traction in high speed driving. The main questions are 1) How many miles on car ? 2) Stock shocks and suspension or aftermarket ? 3) What tires are on the car and how old are they ? Wear in any suspension items or rock hard old tires could cause the problem you are experiencing.

 

 

This was the first thing that I noticed when I bought my vette. I figured it would go away with coil overs but as I was purchasing the coil over I explained my reasoning for wanting the setup to Jeff at TPE and he said the unsteady feeling through high speed corners was a result of the stock A arm bushings flexing. I still bought the coil overs as I was mainly getting them to lower the car and sure it enough the unsteady feeling was still there after the install. It was not as bad but still noticeable. I just installed polyurethane bushings kit and it completely got rid of the unsteady feeling while in turns. It's like a whole new car and definitely the best mod I've ever done to the car.

 

Your BMW has a shorter wheelbase. That is the main differance.

The "corvette kick" in bumpy corners, drives me crazy also. I always wanted to try a set of double adjustable shocks. A little less compression, and a touch more rebound.

A set of poly bushings would sure tighten up the suspension, on the street the noise gets old real fast.

 

I notice the same, slight kick on bumpy corners. Gonna get a more aggressive alignment and see if that helps.

I too have a 1995 M3..ex NASA Track car turned DD....

 

Nice- thanks for the feedback guys. The bushings would make sense but wow, I didnt think that stock vette bushings would be this bad. I refreshed my whole suspension in the BMW and I love the results. Bushings are so vital to a well handling car and Im dreading doing the same thing on the vette. It was A LOT of work! My tires are relatively fresh stocker Goodyear supercar f1s.

My car has 39k miles and was very well taken care of by an old foogie owner when I got it- now Im driving the sh*t out of it and lovin every second of it. =) How much would a kit of poly bushings cost?

BTW- my BMWs bushing kit makes no noise at all- they have to be properly installed, preferable by a DIY owner =)

 

My suggestions, in order of importance:
1. Check bushings, wheel bearings, and ball joints.
2. Alignment
3. Shocks (Bilstien or new C6Z)
4. Upgraded Bushings, but only if they have moved or look torn / damaged.

 

My suggestions. 1. Get rid of the Goodyears for a better tire, they suck. Just about any tire will be better. Personally I've used either Michelins or Vredesteins, and both are so much better in ride, handling, wet weather and noise. 2. Get a good alignment. 3. Replace your shocks, yours just might be shot. Bilstein Sports or new Z06 shocks. I've got close to 100k miles on my Z and it still rides and handles fantastically with no sign of looseness.

 

First off, the Bilstein/H&R combo on your M3 is real good set-up...better than a "simple set-up".

Unless you have an '04 C5Z, the stock shocks just plain suck. Not sure if you're lowered, slammed, or stock height. Suggetsions will vary based on that info, but cars that are stock or slightly lowered (stock bolts) benefit greatly for a set of Bilstein Sport shocks which will only set you back about $300.

 

Rough road instability in our experience has to do with the large amounts of high speed rebound built into the Z shocks, this is considerably worse in the C6Z shocks but is still present with the C5Z. With too much high speed rebound over rough surfaces the weight of the wheel is fighting to maintain a contact patch with the ground but is being momentarily suspended in the air by the shock valving. This can create instability when trying to push the car hard over rough surfaces. There are definitely other items in the equation such as bushing deflection and worn parts, but shock valving does play a large role.

High speed rebound is one of the many differences between our Johnny O'Connell replacement shocks and the factory C6Z shocks that are so popular here on the forums. Although those changes are one of the biggest impacts on performance over imperfect roads. We designed our Johnny O'Connell shocks as a direct OEM replacement that would increase performance for C5 and C6's, while maintaining great ride quality. If you're looking for a suspension package for your daily driver and occasional track day Corvette that's easy to install and setup with no fuss, look no farther than our Johnny O'Connell package!

 

I used the pfadt bushings kit because it comes with the strut bushings(where the strut attaches to the lca) as most other kits dont come with this bushing. I believe I paid 390 or somewhere around there for the kit. I had a friend who has a press install the kit and he didn't complain too much, I guess some of the bushings are hard to get the right angle to press in and out and you have to get creative but I don't think it would be too too hard if you had access to a press.

I did have an issue with the rear lca bushings being too long to get back into the rear cradle( still wondering why they didn't make this a 2pc bushing as most of the others are 2pc) so I had to press them back out and cut them in half and shave down some material to get them to fit. I made a thread about this if you want to look into it more.

I don't have any noise from the bushings whatsoever. If you used the lube they supply with the kit when installing them you shouldn't have any noise come from the bushings. You do feel it a little bit in the ride as far as rough roads and crack and things like that but its not horrible and I have my coil overs set pretty stiff as I'm very low so that may exacerbate it more. I don't remember where I herd/read this but I remember that the stock gm bushing can have up to a 1/4" deflection under load and seeing them after being pressed out I wouldn't doubt it. I still can't believe I waited as long as I did to do this as I feel it's the best mod I've done to the car and makes it 100x more fun to drive aggressively through turns as I don't feel so "out of control" mid turn and makes it much more predictable.

 

I have a 2004 Z06 and I have none of the issues that you mention. Therefore, I would suggest that you use the STOCK 2004 Z06 shocks, OR the Bilstein "Sport" shocks

 

What "born on" date are those tyres?

Any critique of suspension behaviour of a car running old tyres is moot.

When fresh the GYSC F1's are excellent.

Lest we forget a stock C5Z06 on stock GYF1 SC's lapped the Nurburgring in 7m54s. When all components are fresh the car displays very few standout handling flaws.

Over the last 9 years I have taken my car from stock suspension in stock GYF1 SC's all the way to Pfadt coil overs, poly bushings, camber plates, T1 sways, big brakes and Kumho V700's.

At either extreme tired tyres have been the biggest and simplest issue to address.

 

Hmmm so shocks and tires. I want to auto-x and even track my car before doing any drastic changes so I can get a baseline going. After that- then I can start tweaking the car. I want to keep it as stock as possible and if I start tinkering I wont be able to stop. Haha. The first mod on the list is SEATS. Stock seats are the worst I have ever experience. The damn things are loose. >=(

 

Everyone complains that the stock F1 supercars suck, but independent tests from professionals have shown that they are one of the best performing non R compound tires available.

 

They're noticably heavier than PS2's, and they get noisey at about 50% tread life; but new, they were a very good tire. I think they get a bad rap because lots of folks buy these cars used with low mileage, and a lot of times the stock tires are still on the car...and most people don't realize that 8-10 year old tires, regardless of tread depth, far exceeds the useful shelf life of a performance tire.

 

 

Yes, the backend can skip out easily over bumps on higher speed corners. At 20k I ended up replacing my shocks with original single-adjustable pfadt coilovers shortly after Aaron released them like... 4 or 5 years ago. Big improvement and still the best mod I ever did, and I'm now at 60k.

Now if you play with the settings you CAN adjust them to such a degree that that some of that behavior comes back. So it makes sense what has been said about the valving.

Obviously old tires need to be replaced but I doubt your bushings are shot.