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More questions from the owner of the Vette from Hell:
Now that I have the brakes, clutch, and carburetor problems under control I can actually drive the car. Being my first Corvette, I didn't know what to expect and what I got was not up to my expectations for sure. The car is a stock '65 327-300, 4-speed, convertible with power steering. The car came out of a recent and mysterious restoration. The suspension is stock with almost all new front end parts (except the springs). The rear is also mostly new with a new 9-leaf spring. The shocks are big gray things that probably came from some catalog as the past restorers' modus operandi was to buy loads of new parts and throw them at the car. The front bar is 3/4" and there is no rear bar.The tires are Coker orange line classics: P205 75 R15 (I'm convinced that this is most of the problem). The wheels are stock steel (I believe 5.5" width and they have the stock hubcaps, which I personally find hideous....). This car will be street driven only but I'd like to take advantage of an exit on/off ramp now and again. I'd like to do this with confidence and no surprises.
The car sits level and appears to be the correct ride height. The ride, with respect to harshness and spring/shock balance is okay. I don't want to change that too much. The handling is difficult to explain. It's "wiggly". Turning a corner at a light seems to produce a lot of body roll and coming out of the corner (15-20 mph) and accelerating normally makes the car "wiggly" like the rear suspension is playing games. Otherwise, the car tracks straight down the road. At least it does that well. I don't know what the alignment specs are. There's an excellent alignment shop just down the street so I can get that done with confidence, once I determine what they should be.
My first fix would have been to put a rear bar on it but other discussions (with excellent comments from SWC Duke and Jerry Gollnick) have convinced me otherwise for now. I don't think the car needs to be anymore twitchy (it's not now but it certainly doesn't suffer from excess understeer like stock GM A cars). My other fix would have been to put some 15 x 7 (or 8) rims on it and some BFG's (this has worked wonders for many other project cars). However, now when I look under the car there doesn't seem like a lot of room for going too different on the tires. For example, as it sits now, the parking brake cable is less than 1/4" from the inside rear tire side wall. If I'm going to increase wheel and tire width it's going to have to be all outwards and I don't want to have to modify my wheel wheels (intentionally or otherwise).
So, my questions are:
1) Does this "wiggly" feel sound familiar or is it my unfamiliarity with the car?
2) Ditto with the body roll. I don't like it but I haven't put the car greasy side up yet.
3) I know the tires aren't optimum and I think excess sidewall flex could be some of the problem. I'd rather not go to 16" or 17" wheels but if shedding some flexible sidewall will cure the wigglies then I'll do it. Also, although BFG's are convenient, decent $, and available, I'm open to suggestions. (BTW, I'm in Upstate NY, the pot hole capital of the nation. SOME sidewall is necessary.)
4) I'd like to put on rally wheels. There are some 15 x 6" available from all the catalogs but this doesn't seem like too much of an improvement. I am concerned with inside and outside clearance. What can I get away with that's close to the OEM diameter?
5) What are some recommended alignment specs and how are they affected by tire/wheel combinations?
Compared to newer cars my BB, stock suspension car is a bit soft and bouncy even with custom HD shocks but I wouldn't call it wiggly. The rear suspension does move and make itself known on these cars, but if it feels like it's loose or steering the car under braking or acceleration I would take a good look at the rear trailing arms and make sure the bushings are tight and the shims are packed in tight on both sides. Tires could be an issue. The alignment could also be an issue. For roll, try a bigger sway bar up front first. Bigger ones are available.
Compared to newer cars my BB, stock suspension car is a bit soft and bouncy even with custom HD shocks but I wouldn't call it wiggly. The rear suspension does move and make itself known on these cars, but if it feels like it's loose or steering the car under braking or acceleration I would take a good look at the rear trailing arms and make sure the bushings are tight and the shims are packed in tight on both sides. Tires could be an issue. The alignment could also be an issue. For roll, try a bigger sway bar up front first. Bigger ones are available.
Agree 100%. My rearend was just rebuilt by a knowledgeable forum member and there is nothig 'wiggly' about it. But, if youre comparing it to a C7 that's a computer on wheels with modern suspension then yeah - you are in for a dissapointment..
More questions from the owner of the Vette from Hell:
Now that I have the brakes, clutch, and carburetor problems under control I can actually drive the car. Being my first Corvette, I didn't know what to expect and what I got was not up to my expectations for sure. The car is a stock '65 327-300, 4-speed, convertible with power steering. The car came out of a recent and mysterious restoration. The suspension is stock with almost all new front end parts (except the springs). What parts are NOT new other than the springs? The rear is also mostly new with a new 9-leaf spring. What parts are not new? The shocks are big gray things that probably came from some catalog as the past restorers' modus operandi was to buy loads of new parts and throw them at the car. Good reasonably priced known brand gas charged shocks can make a world of difference. The front bar is 3/4" and there is no rear bar. The tires are Coker orange line classics: P205 75 R15 A common size many of us run are 205/70/15 or 215/70/15. (I'm convinced that this is most of the problem). These Coker tires serve a resonable purpose, but mostly for show. The wheels are stock steel (I believe 5.5" width and they have the stock hubcaps, which I personally find hideous....). It's common to find many C-2 owners running 15x7 with a back spacing of 3 3/4". I personally have 205/70/15 w/3 3/4 BS on American 200-S wheels with NO interfierence. This car will be street driven only but I'd like to take advantage of an exit on/off ramp now and again. I'd like to do this with confidence and no surprises.
The car sits level and appears to be the correct ride height. Don't trust your eyeballs. Get the specs and locations from the AIM and measure. The ride, with respect to harshness and spring/shock balance is okay. I don't want to change that too much. The handling is difficult to explain. It's "wiggly". Turning a corner at a light seems to produce a lot of body roll and coming out of the corner (15-20 mph) and accelerating normally makes the car "wiggly" like the rear suspension is playing games. A combination of these three might be the source of the "roll and wiggle" you describe. As Dan's Yellow66 suggested, check the trailing arms for shims or the lack of. Get a shim pack with holes from one of our vendors. You may need them at the alignment shop. Otherwise, the car tracks straight down the road. At least it does that well. I don't know what the alignment specs are. There's an excellent alignment shop just down the street so I can get that done with confidence, once I determine what they should be.
My first fix would have been to put a rear bar on it but other discussions (with excellent comments from SWC Duke and Jerry Gollnick) have convinced me otherwise for now. I don't think the car needs to be anymore twitchy (it's not now but it certainly doesn't suffer from excess understeer like stock GM A cars). My other fix would have been to put some 15 x 7 (or 8) rims on it and some BFG's (this has worked wonders for many other project cars). Trying to fit 8" wheels and 60 series might create fender and hardware problems. However, now when I look under the car there doesn't seem like a lot of room for going too different on the tires. For example, as it sits now, the parking brake cable is less than 1/4" from the inside rear tire side wall. If I'm going to increase wheel and tire width it's going to have to be all outwards and I don't want to have to modify my wheel wheels (intentionally or otherwise).
So, my questions are:
1) Does this "wiggly" feel sound familiar or is it my unfamiliarity with the car? Wiggly doesn't sound right.
2) Ditto with the body roll. I don't like it but I haven't put the car greasy side up yet. See above.
3) I know the tires aren't optimum and I think excess sidewall flex could be some of the problem. I'd rather not go to 16" or 17" wheels but if shedding some flexible sidewall will cure the wigglies then I'll do it. Also, although BFG's are convenient, decent $, and available, I'm open to suggestions. (BTW, I'm in Upstate NY, the pot hole capital of the nation. SOME sidewall is necessary.) See above
4) I'd like to put on rally wheels. There are some 15 x 6" available from all the catalogs but this doesn't seem like too much of an improvement. I am concerned with inside and outside clearance. What can I get away with that's close to the OEM diameter? See above.
5) What are some recommended alignment specs and how are they affected by tire/wheel combinations? Try to find an alignment shop that knows Vettes since there alignment process is different than modern day cars. Techs in shops these days may not have ever seen and independent suspension as in our cars.
Many thanks!
Joe
Joe, see my remarks in red. Dennis
Last edited by Bluestripe67; 09-30-2018 at 02:30 PM.
So, my questions are:
1) Does this "wiggly" feel sound familiar or is it my unfamiliarity with the car?
2) Ditto with the body roll. I don't like it but I haven't put the car greasy side up yet.
3) I know the tires aren't optimum and I think excess sidewall flex could be some of the problem. I'd rather not go to 16" or 17" wheels but if shedding some flexible sidewall will cure the wigglies then I'll do it. Also, although BFG's are convenient, decent $, and available, I'm open to suggestions. (BTW, I'm in Upstate NY, the pot hole capital of the nation. SOME sidewall is necessary.)
4) I'd like to put on rally wheels. There are some 15 x 6" available from all the catalogs but this doesn't seem like too much of an improvement. I am concerned with inside and outside clearance. What can I get away with that's close to the OEM diameter?
5) What are some recommended alignment specs and how are they affected by tire/wheel combinations?
Many thanks!
Joe
1) The stock chassis will amplify the poor grip feel of tires with poor traction (quality tires for handling will help). A worn chassis with sloppy 50 year old bushings and ball joints just makes everything worse.
2) Rear body roll is amplified by excessive rear ride height (longer spring bolts will lower the CG closer to the rear roll center and reduce roll).
Front body roll is amplified by soft anti-sway bar end link bushings and pillow block bushings (poly pillow block bushings and end link bushings will reduce the transition, wiggle, duration).
3) 26.5" to 27.5" tall, 15", tires are usually SUV tires, and do not have a street oriented traction tread or compound (there are a number of threads on more race oriented 15" tires with a 65 or 70 series aspect ratio).
The typical 15" performance tires that are guaranteed to fit a 6" rim under the fender are 205/60/15, and are ~24" tall, the equivalent in an 11% lower rear axle gear ratio (11% faster engine speed at the same road mph as the current tire).
There are a number of 16/17/18 inch rim choices for near stock height tires that will provide some tire sidewall with better tread and tire traction compounds.
4) The 1967 style 15x6 Rally rims are guaranteed to fit without chassis modifications, and will fit 205-215 performance rubber. A 7" rim and wider tires will require modifications detailed in many threads.
5) Alignment spec book ranges have been provided.
Adding caster to 1.5 degrees or more (recommended with power steering) will add mild steering effort at low speeds, and reduce steering feedback wiggle at speed.
Adding mild toe-in, to ~3/8" total, will reduce the off center darting steering feel under braking and turn initiation without promoting excessive tire wear.
Verifying rear toe in alignment to the frame at ~1/4" total cures many handling ills. Verify the trailing arms bushings, the lower strut rod bushings, and inboard alignment cam bolts are tight with no play.
Adding mild front and rear camber, to ~1.5 degrees, will help cornering traction at speed but typically noticeable only with good tires at corner speeds over ~75% of the car's traction limits.
Modern mono-tube gas shocks with digressive valving helps a great amount to dampen low speed body roll, while allowing quick suspension movement over road imperfections and jolts (the first improvement to make).
Modern adjustable shocks will help match the damping if you expect to tinker with suspension changes as you improve the tires and chassis.
The stock power assist steering has a number of wear points and bushings that can amplify steering wiggle. Everything needs to be tight. There are good reasons the aftermarket has improved modern integrated power steering boxes and rack & pinion conversions. It is rare to read someone criticize the improved feel of a more modern steering system (and I have never read someone converting back to the stock power steering except to restore a car).
Worn rear differential side yokes can promote wiggle from the rear tire track expanding and contracting from excessive end play. This is a less common concern, but with a 50 year old car it is something to have the alignment technician check while the rear tires are in the air.
The ride height and CG of a C2 is higher than modern sport sedans, so the feel of body roll is on a longer leverage arm than what is typical for a modern car. You should be able to eliminate the wiggle, but achieving more of a modern roll feel typically requires higher rate springs that lower the chassis on the suspension (new springs, with or before fitting big anti-sway bars).
If you have not archived a copy of the Chevy Power Book, the link below will download a pdf of the book with a focus on the C2/C3 chassis. You don't have to implement all of the race modifications, or welding, but the bolt on bushing improvements and recommended alignment settings provide what works. It is a good read as a beginning guide to understand what can be accomplished with the chassis.
My advice-- Tires and wheels 1st--alignment 2nd--stiffer front sway bar 3rd.--SMALL rear bar if needed. These 3 changes should give you a much better car.
Your car CAN and SHOULD drive like a new 1966 car. Mine does. It will never, however, drive like a "modern" radial tired car. Alignment done properly by an alignment shop that has done it before will yield neutral, reasonably light handling and steering without darting or wandering. The tire issue is HUGE. Your Coker's are retreads on radial carcasses which don't do a good job of being either type. I took my knock-offs and Coker's off and put on stock '66 steel wheels and narrow, period correct looking Kelsy's. It darts like crazy on the horrible grooved roads we have around here (due to the studded tires -Oregon) but on a smooth (normal) road it drives like it just rolled off the car carrier at the dealership.
C2/3 Corvettes are extremely sensitive to rear toe. With the typical "van tires" that most guys run the car will never develop more than about 0.75 lateral g, but the handling should be neutral and stable up to near the limit where they can often snap into oversteer.
Visit the alignment shop and discuss the rear toe situation. Does the car have "captured" or "slotted" shims? Does the shop have any experience adjusting C2/3 rear toe, especially with the captured shims? I've posted recommended alignment settings for both "touring" and "sport" several times.
Unless you are thoroughly grounded in vehicle dynamics and have chassis tuning experience, forget about adding/changing anti-roll bars or changing springs or adding wider wheels. The OE setup is fine for normal driving as long as alignment settings, especially rear toe, are in the ballpark. In fact the ride is much more supple than most modern "performance cars". If you want more grip, use the sport settings and get a set of 205/70R15 Avon CR6ZZ tires.
The other thing that can lead to "sloppy handling" or vagueness on center is a worn steering gear. If this is the case remove it and send it to a reputable pro for rebuild. Don't try to adjust it on the car.
First, thank you for all of the great comments and advice. This has helped me confirm what the issues may be, what to check, and a good strategy to follow.
I'm pretty confident that most of the suspension pieces are in good shape-I've done all the conventional checks on the ball joints, tie rod ends, etc. I'm pretty sure my steering box is good. I've faced bad steering boxes in the past and am familiar with their characteristics-this car does not exhibit these.
Considering that the past owners threw parts at the car and threw the car together in a hurry tells me that the alignment could be suspect. Even though it tracks well and stops straight that's not an indication of a correct or optimum alignment. As I mentioned previously, there's a boatload of shims on each side of both trailing arms but there are no really thin shims, which could indicate that they were just stuffed there to take up space and not necessarily for fine tuning. Assuming that the alignment parameters don't need to be changed for the potential difference in tires I may choose in the future, the first thing I'm going to is have the car aligned. Again, I don't know if the guy down the street has specific experience on Vettes but I've seen just about everything at his shop from contemporary cars to antiques to exoteric Italian cars to muscle cars. He understands suspensions and his equipment. It's like choosing a good engine shop: a good engine machinist should be a machinist first and a car guy second, not the other way around. This alignment guy just understands and he's been doing it for 40 years. The alignment shop will also confirm if parts are okay. Once realigned, I'll reassess the situation. 6" Rally wheels appear to be a safe bet and perhaps a 215-60 15 tire is a good compromise. I've seen comments on Avon tires. Any other suggestions? I like BFG's but mainly because they're plentiful. Oh, while I'm at it, what about snow tires? (Just kidding....)
Again, many thanks!
Joe
First, thank you for all of the great comments and advice. This has helped me confirm what the issues may be, what to check, and a good strategy to follow.
I'm pretty confident that most of the suspension pieces are in good shape-I've done all the conventional checks on the ball joints, tie rod ends, etc. I'm pretty sure my steering box is good. I've faced bad steering boxes in the past and am familiar with their characteristics-this car does not exhibit these.
Considering that the past owners threw parts at the car and threw the car together in a hurry tells me that the alignment could be suspect. Even though it tracks well and stops straight that's not an indication of a correct or optimum alignment. As I mentioned previously, there's a boatload of shims on each side of both trailing arms but there are no really thin shims, which could indicate that they were just stuffed there to take up space and not necessarily for fine tuning. Assuming that the alignment parameters don't need to be changed for the potential difference in tires I may choose in the future, the first thing I'm going to is have the car aligned. Again, I don't know if the guy down the street has specific experience on Vettes but I've seen just about everything at his shop from contemporary cars to antiques to exoteric Italian cars to muscle cars. He understands suspensions and his equipment. It's like choosing a good engine shop: a good engine machinist should be a machinist first and a car guy second, not the other way around. This alignment guy just understands and he's been doing it for 40 years. The alignment shop will also confirm if parts are okay. Once realigned, I'll reassess the situation. 6" Rally wheels appear to be a safe bet and perhaps a 215-60 15 tire is a good compromise. I've seen comments on Avon tires. Any other suggestions? I like BFG's but mainly because they're plentiful. Oh, while I'm at it, what about snow tires? (Just kidding....)
Again, many thanks!
Joe
Proper alignment and Avon CRZ66 tires will make a huge improvement. Avons are expensive but worth every penny. I have 205/70R15 0n my 63 and have 215/70R15 on my 67,
but the 215s are nearly an inch wider than the 205s (you would think only 1/2 inch). We had to shave the inner part of the lip to 3/8 inch and go 1 degree neg camber for clearance in the rear. Car is not quite done so not sure how that is working.
Never have understood why people skimp on brakes or tires.
One thing that sometimes gets overlooked on these cars is the rear end stub axle clip. If one or both are missing the rear will be all over the place. I had one missing and it felt like you describe. The issue is that if the clip is not there then the stub axle moves in and out when it supposed to be fixed in place. Very simple to check.Try and pry the stub axle out when the car is jacked up off the ground. If the stub axle moves just a few thousandths but stops the clip is there but if it is completely missing it will move a lot, limited only by the trailing arm.
I would stay away from BFG Radial T/As if that is what you are referring to. I know they have their fans but they are a nostalgia tire to me. The Cobra replica crowd considers them out right dangerous on light weight vehicles like Cobra's and their replicas - although more weight like an intermediate Chevelle, GTO, GTX does seem to settle them down some. A Corvette's weight is sort of in-between making them marginal by this whole theory, belief. Take it for what it's worth.
I found the rear strut rods to cause some instability. Could feel it even in slow cornering. My new ones had the rubber sleeves going loose very soon, and that with my very mild driving style. I replaced with Global west adjustable rods. The ball ends make for a tight link, and no twist/torque on the rods ends due to different aligning angles of wheel/rear end fixings. All I can say is that the feel in corners was way better. Some fear for more noise cause it's metal to metal without the rubbers, but I notice none of that in my overall very quiet car.
Last edited by alexandervdr; 10-03-2018 at 05:24 PM.
Proper alignment and Avon CRZ66 tires will make a huge improvement. Avons are expensive but worth every penny. I have 205/70R15 0n my 63 and have 215/70R15 on my 67,
but the 215s are nearly an inch wider than the 205s (you would think only 1/2 inch). We had to shave the inner part of the lip to 3/8 inch and go 1 degree neg camber for clearance in the rear. Car is not quite done so not sure how that is working.
Never have understood why people skimp on brakes or tires.
Where did you get Avons? I tried TireRack and Discount tire and they didn't have anything close to that size.
I found the rear strut rods to cause some instability. My new ones had the rubber sleeves going loose very soon, and that with my very mild driving style. I replaced with Global west adjustable rods. The ball ends make for a tight link, and no twist/torque on the rods ends due to different aligning angles of wheel/rear end fixings. All I can say is that the feel in corners was way better. Some fear for more noise cause it's metal to metal without the rubbers, but I notice none of that in my overall very quiet car.
The rear strut rods look like one of the only pieces in the suspension that hasn't been replaced. Although they don't have any play when wrestled with, the rubber isn't pristine looking. A friend of mine had an extra set of adjustable rear struts. They're not Global but they look like decent quality. I'll put them in before I bring it to the alignment shop-that should make the job easier to do.
Roger Kraus Racing in Castroville, east side of the SF Bay area. He has the spec sheet on his Web site, and you can also get it from the Avon Web site.
It doesn't appear that the CR6ZZ conforms to Tire and Rim Assc. dimensional specs. The difference between the 205/70 and 215/70 OD is only 0.1", but the 215/70 has nearly one inch wider tread width, so if you don't want to shave the fender lips, go with the 205/70.
Also the revs per mile appear to be based on the "rigid body" calculation, so it's actually greater than specified. The actual loaded revs/mi is probably close to 775 for both, so they shouldn't add much to typical slightly high speedo readings with OE tires.
09-30-2018, 12:58 PM
More questions on C2 handling
Dennis
