Any suggestions from the group on replacement shocks for the front and rear of a 67 327/300HP Vette? I am adding a larger front sway bar, and the appropriate smaller rear bar, plus 460 lb/inch GT front springs. I would prefer to keep a nice riding car rather than making the ride any rougher. Maybe GM Reacteks, or KYB GR-2's??? What shocks are known for a good smooth ride, or a good balance of ride and handling?
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Re: Request shock absorber suggestions
Let's get serious, here. You're installing huge anti-roll bars and
springs that are nearly as stiff as F-41 and you are asking about shocks
for a smooth ride!!! The ride rate is established by the SPRINGS, not the shocks! If you doubtle the ride rate, it's going to ride like an empty dumptruck regardless of shocks.
Forget the big springs, just install the bars and adjustable shocks. As bar and/or spring rates go up you need more damping and the only shocks
that will have a ghost of a chance of working properly are Koni or Spax
adjustables. I prefer Spax ( www.spax.co.uk ) because the have a wider range of adjustment can can be adjusted on the car. Koni's have to be removed to adjust.
Also, since tires are about 90 percent of the handling equation the big
bars won't yield much improvement if you have junky hard-as-a-rock S-rated tires.
Tires, shocks, alignment, and anti-roll bars are the way to improve handling in the stated order. The very LAST thing you want to change is springs, and unless you are building a dedicated race car, I would highly recommend keeping the original base suspension springs.
If you review my two part tire article from The Corvette Restorer a year ago you will find some tips on improving handling. It starts with tires, but shocks, alignment, and bar tuning can be very effective at getting the most out of the best available tires.
Improving your Corvette's handling requires an understanding ride/handling basics, an understanding of your objectives and the typical ride/handling tradeoffs you will have to make, and then appling a systematic approach to modifications. The way you are going is to just bolt on parts, which is what most guys do, but it rarely results in a satisfactory outcome.
Duke -
Re: Request shock absorber suggestions
Well, you are accurately highlighting my ignorance on handling - or at least where I was a few years ago!! But in my defense let me tell you how I got to this point. Handling of my car was never one of it's strong points. Whenever I drove it (it was my dad's car) it leaned, dove, slid, and just didn't handle well in my opinion. We replaced all suspension parts back around 1983 with new GM parts, installed Michelin X radials size 205/75R-15, and it rode nicer and smoother, but still sloppy. Next, move forward in time to 2000. Dad is gone and the car is mine, and I figured I wanted to take the car and continue the restoration process towards making it a nice fun driver car. The car has basically sat around since the mid 80's. I attended the Houston Corvette Expo (which takes place again this weekend coincidentally) and Vette Brakes had a nice display there. I guess in my ignorance I fell for their sales line and what I think they called the Level 1 handling kit interested me. That approach, which I purchased parts for in that time frame, was to install GT front springs, thicker front bar and add rear bar, and new shocks. I also purchased poly bushings front and rear.
Unfortunately, at that time I don't think I really even knew what the NCRS was so I didn't have access to this wealth of information. Most people I talked to seemed to support the approach that Vette Brakes was selling and that I was taking.
So, here we are today. The front springs are installed as is the front bar and front poly bushings. Rear bar not installed yet nor rear bushings. It has taken me all this time to get the engine back together and many many other things done (you guys know how that goes!! :-) This weekend, one of my shocks started leaking fluid out of it, so they need replacing. In my brief test drives over the last few weeks, I can see that the suspension is much stiffer than it used to be (even without the rear bar). I am withholding drawing a conclusion on ride just yet, but my first impression is that it is stiffer but really not objectionable - the sloppiness seems to be gone. As I mentioned in another post, I think I have a 1 1/8" bar up front and 7/16" rear (when it gets installed). Vette Brakes claimed they were "balanced".
I figured I would complete the installation of the parts I have since most of the work is done, and then see what I think about it. Like I said, I am not against pulling the springs out and maybe reducing bar sizes. I have learned a tremendous wealth of information from this forum and from local folks here in Houston recently, and greatly appreciate the honest comments that folks make.Comment
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Re: Request shock absorber suggestions
When these cars were new there wasn't much on the road that handled better!
In later years an immediate improvement could be had with radial tires, and
the more performance oriented the tire (high speed rating, low wear rating) the better the improvement.
Much better handling and ride control can also be obtained with adjustable shocks, which allow the user to tune the ride/handling to their specific requirements. Performance alignment settings go a long way, too, and the use of hard urethane bushings in the front anti-roll bar links yield a noticeable improvement in steering response and stabililty at the ragged edge of the handling envelope. Like initial engine timing and centrifugal advance curve, shocks and alignment are "tuning parameters" that apply to the ride/handling rather than the engine torque curve.
As time passes wear and degradation occur. Many vintage Corvette owners probably dont' have a clue what their current alignment setting are or when the car was even last aligned or the settings that were used - or what settings are
even desireable to achieve their objectives.
If suspension bushings are deteriorated, some serious repair/restoration is needed, but if they are sound, tires, shocks, alignment, and minor anti-roll bar tuning goes a LOOOOOOOONG way.
The basic ride quality is established by spring rates and the OE springs create a ride frequency that is in the range appropriate for a high performance sports car. If the springs are not seriously corroded or otherwise damaged they should not be replaced. If replacement is required, an OE equivalent spring should be installed.
You've fallen into the aftermarket trap! You don't need high rate springs and huge bars to restore the car's original excellent ride and handling characteristics, and you will probably not like the harsh/bouncy/jarring ride they create. The suspension DOES NOT need to be completely re-engineered, but restored to original component performance. Then installation of the best modern high performance radials, adjustable shocks, and alignment settings appropriate for your primiary mode of driving - be it cruising, canyon carving, mild racing, or some combination of all. You will have a car that is significantlly improved from its original form with bias ply tires, "average driver" aligment settings, and limp shocks.
DukeComment
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Re: Request shock absorber suggestions
Duke, You make a number of good points. I need to replace the bushings in my 67 big block coupe with air and am concerned that the car presently rides a little low in front. The springs look good and are not corroded but I have had a couple of people tell me that I should replace them. I have seen a number of mid year coupes where it is onbvious that the springs have been replaced since the from end arches up dramatically and I do not want to do all the work on my suspenion with that result. Another person recommended that I use the OEM spring spacers that Doc Rebuilsd sells and my original springs. You have obviously had a lot of experience in this area. What do you recommend?Comment
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Re: Request shock absorber suggestions
Well, first what does a "little low" mean? You should measure the "Z" dimension and compare it to spec. Same with the "D" dimension at the rear.
If/when you remove the springs measure their free length and wire diameter and compare them to the AMA specs that GM provides with the "restoration package" complimentary to anyone who calls customer service and provides their VIN.
Also, inspect the rear leaves for serious corrosion, and if they appear okay and the "D" dimension is in spec, just rebuild them with new liners. I also recommend applying a corrosion resistant coating to coil springs and spring leaves, which is satified by just wire brushing them and applying Rustoleum Rusty Metal Primer and a top coat of your choice, but it will cost a deduction if you have the car judged.
Once you have the necessary data, you can determine your path.
Available anecdotal evidence indicates that the so-called "reproduction" coil and leaf springs are not very faithfull to original specification, so I would do everything possible to save and use the original springs unless they show clear evidence or serious corrosion or other damage.
DukeComment
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Re: Request shock absorber suggestions
There are two distinct schools of thought on suspension tuning for handling. One is stiff springs and bars, the other is soft springs and stiff bars. Herb Adams is a proponent of the latter. Either way, shock rebound rates will have to increase - substantially with stiff springs - to control body motion.
As average speeds increase, stiffer springs are usually desireable, but for a street driven car I believe that Adam's philosophy is best - OE spring rates and then select bars to control roll and achieve the handling balance you desire.
Big bars do not effect wheel rate on a two wheel bump such as a dip or rise, but they have a big effect on one wheel bumps. High rate springs and big bars will make the ride STIFF no matter what kind of bump or road condition.
Shocks are probably the most under rated component of the suspension, but they are critical to ride and handling, and adjustables allow you to tune the damping to what you need.
Bilstein does have a SUPERB warranty. They rebuilt the 20 year old shocks on my Cosworth Vega under the warranty (I still had the original receipt.), but they never went back on the car. Replaced them with Spax, which FINALLY allowed me tune the damping rates to what was needed. I sold the Bilsteins to another CV owner.
I also have Bilsteins on the SWC, but they will be replaced with Spax before it goes back on the road, so I have an unused set of Bilsteins for sale.
DukeComment
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Re: Request shock absorber suggestions
I am one of those who mainly goes to the medium spring/big bar philosophy, because unless the road surface is perfectly smooth, then you have the problem of keeping the wheel on the ground.
On a race track (most anyway), there are no potholes or washboard areas. The tires do not skip across bumps, so you can run a much stiffer spring. However, you really don't need it unless you are using them to counter the roll effect or on a track that dips or on a high-banked oval. On Daytona, you need the stiff springs because you need to resist the force that tries to smash you into the pavement as you go around.
However, a track like Mid America Raceway (now closed 18 years), there were so many patches that stiff springs would cause a car to skip around corners. My standard suspension '68 was faster than many of the F41 suspension cars in lap times there, mainly because I could keep power on in the corners when they had to work to keep from bouncing off the track.
On the street, you never have a perfectly smooth surface. Basically, you get the empty 1 ton truck effect on wheel hop over the potholes and the washboard at corners where the road ripples from braking loads of heavy trucks.
He can expect that he will get a lot of wheel hop trying to accelerate at some corners, an unnerving skipping sideways in some corners, and a feeling that the car is far inferior in handling than it really is.
Soft springs prevent a lot of that. There is a reason those springs were as soft as they were for the street.Comment
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Re: Request shock absorber suggestions
Mike, you are close regarding the kit that I purchased. What I have is basically the kit shown on page 8 of VBP 2004 catalog. It includes a standard 9 leaf steel spring (old one was sagging), 1.125" front and .75" rear bar, GT 460 lbs/inch springs. I kept my existing shocks since they were very similar to the KYB GR2's that the kit included. I added poly pushing kits for front and rear. Now my shocks are, well, shot.
So, assuming I decide to pull the springs off and go back to my stock front springs, I take it that a 1 1/8" front bar and 3/4" rear bar are probably too large right? If this is correct, what size front and rear bar would be a good choice? My first thought is the smallest rear bar that I can get, and the appropriate front bar that balances it. I hope to leave the poly bushings installed. Sounds like with this approach adjustable shocks would be a good thing so that I could "dial" in just what I want and like?
Regarding tires, I am soon to replace them, possibly with Duke's recommended Pirelli P4000 215/70R-15's. I have to make sure they fit my particular car however.
By the way, when I walk up to the Vette Brakes booth this weekend, I hope I don't walk away with a racing suspension!! :-)Comment
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Re: Request shock absorber suggestions
Tim first let me say that I think it is great that have your Father's 67 to enjoy.
I have a 70 and have installed a Vette Brakes full performance suspension. This includes front and rear transverse fiberglass composite springs, 360# on the rear, poly bushing front end Vette Brake control arms, sway bars front and rear, and adjustable Carerra shocks. The front spring is adjustable and I run it on the street at the softest setting. The shocks are adjusted for the softest setting. Installed it about 10 years ago and still like it enough to keep the suspension system in place, as I have retained the removed suspension components. Sure handles great in traffic, that is the only area I compete the car. I can come onto and leave the interstate with the great handling of this system. One easy thing about this system is that is the rear sway bar can be just simply disconnected very easy if one wanted to test out the difference in handling. This car sits in the garage more than it is driven, but I do enjoy the ride when I take it out.
Before I installed this system I changed out the front springs of my 70 air conditioned, power steering, power brakes, and turbo 400 350/300HP with the much stiffer Corvette 518 springs. I also installed the 360# rear fiberglass Vette Brakes spring. I was using gas shocks and liked the change. The rear did not bottom out like on the ole factory rear spring when the car was loaded for a trip. Never really thought the car as riding rough with the stiffer front springs, just handled better as far as I was concerned.Comment
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Re: Request shock absorber suggestions
Jim -
How do you like the transverse front spring? How does the handling and ride quality compare to OE coil springs? I ask because I recently heard someone describe the ride as "bouncy".
Mike S
#33053Comment
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Re: Request shock absorber suggestions
I have used Bilsteins on several drivers, Vettes and otherwise, and have had mostly wonderful success. Out of about ten sets I had one shock go bad. One set has over 100k on them and still going strong.Dick WhittingtonComment
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Re: Request shock absorber suggestions
I agree that Bilsteins are very high quality and the deCarbon high pressure
gas charge is excellent technology, but that doesn't mean that the damping
rates will be to my liking.
DukeComment
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Re: Request shock absorber suggestions
Mike-
I had been using the Vette Brakes rear fiberglass for years before I put the complete front transverse system on the front. I installed the 360# composite spring, so it was a definite difference from the original much softer steel spring on my 70. I liked it, some bounce, but not enough that made me constantly aware. I don't know if the 330# spring would be more bouncy like you mentioned or not. Perhaps the 360 is not as bouncy as a 330.
The front system totally changed the way the car handled. The change placed poly bushings in the Vette Brakes control arms and the sway bar. The front transverse spring has four settings of adjustment. I started out using the second inboard position and changed it to the first inboard positon which made the spring ride a little softer. I also adjusted the Carerra shocks to the softest setting. With the car set up this way I really don't have the bounce you mentioned. The car is really handles. Swaping lanes at speed and getting on the interstate the handling is very predictable. Next time I get the car out I will pay more attention on how much bounce I have.
I have installed the 360# Vette Brakes rear spring on my 68 and like it as well. The front only has poly bushings and gas shocks, rest of front suspension is original. What is missing from both cars is the Corvette squat when you get on it. The 68 being a 4-speed still lifts the front some, but not like it used to.
Recommend you take a ride in someones car with the Vette Brakes suspension to see if you like the change. The ride will reflect how the installer set it up.Comment
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