Took the '65 out for a ride today. A noticeable difference in steering feel compared to a modern car. The '65 has 205/75 radials. Similar situation with the '56, with radials. The caster specs are about 1-1/2 to 2 deg, (for bias ply tires). C-7 corvette caster is about 7 deg, for radials. I'm thinking a C-1 or C-2 should have more than 1-1/2 deg caster when equipped with radials to improve the feel.
Thoughts?
Anyone gone from bias ply to radials and felt a big difference?

 

[QUOTE=davekp78;1591701967]Took the '65 out for a ride today. A noticeable difference in steering feel compared to a modern car. The '65 has 205/75 radials. Similar situation with the '56, with radials. The caster specs are about 1-1/2 to 2 deg, (for bias ply tires). C-7 corvette caster is about 7 deg, for radials. I'm thinking a C-1 or C-2 should have more than 1-1/2 deg caster when equipped with radials to improve the feel.
Thoughts?
Anyone gone from bias ply to radials and felt a big difference?QUOTE]

Absolutely - there's an enormous difference in steering feel; neither the C1 nor the C2 steering/suspension systems were designed to accommodate high levels of caster (or camber gain, for that matter); they are what they are, short of total redesign.

 

with everything John said.
I added new upper control arms to mt '65 that allows for up to 6* of castor. Mine are set at 4.5* of pos. castor. Big difference in tracking. It tracks in a nice straight line. Even when I take my hands off the wheel she still goes in a straight line for a distance.
I also have radial tires - 215/70 R15.






65-StingRay
Wayne

 

What brand arms are those and where can I find them?

 

Set the castor at the factory spec 1-2*positive and and get the suspension tight with new rubber bushings. Make sure the steering box is adjusted correctly where it's snug at the straight ahead position you will be very happy with the steering feel with radial and bias tires.

If you want the new car feel you need a new car, don't spend $$$ trying to re-engineer something that was designed with 50 yr old technology.

 

Good advice here - you should definitely enjoy your car the way he says as the entire restomod industry is obviously blasphemous. You may want to send this man a private message so you can paint your car his favorite color, as all the other colors are wrong too.

 

Sorry if my response offended you, the O/P did not say anything about restomod.

The question asked was did anyone else go from bias to radial tires and feel a big difference and he felt a C1-C2 car should have more caster. I answered the question based on my opinion that's all.

PS, I like all the Corvette colors.

 

I'm not offended, I just laugh at narrow-minded replies like that and can't help poking fun at them. One of the coolest things about the classic cars - especially Vettes - is that you can go NCRS or use C7 suspension to make it handle like a modern super car or anything in between. Adding caster makes a big difference in handling and if you don't want to do it to your car that's perfectly understandable but why advise him against it, especially if he has power steering and modern tires and can do it with no detrimental effect? Everyone gets different pleasure from their cars - I like modifying them, but I don't tell a guy that's asking about original colors or markings for a restoration that he's wasting his time.

 

If you need more castor but want to keep the original upper control arms [and a crap ton of $$ in your pocket] They make offset upper control arm shafts that allow you more adjustment. I have them in one of my GTO's...huge difference.

 

Who makes them?

 

K6104 Moog I think....

 

Has anyone tried maxing out caster with the stock components? I wonder what can be obtained. I'm going to talk to my local Corvette specialist and see what he thinks. I assume increasing the caster will decrease the positive camber. I'd be OK ending up with 0 to about -.1 degrees negative camber.

 

I asked my very Corvette-literate alignment guy to put as much caster as he could when he did mine.... He said he only was able to get 1.9 - 2.0 As he explained it, these cars just weren't designed with the need for much more caster in mind and if he tried to achieve more with the stock components it would require a taller stack of shims than he felt was safe and that much shim would begin to push the camber out of spec. Made sense to me, so I put aftermarket adjustable upper control arms on my Vette wish list!

 

Yes, radial tires do make your C1 or C2 handling "feel" differently. However, I believe there is another factor here which needs to be considered. Modern car tires are (relatively) extremely low profile. I run 30 or 35 profile tires on my C5 Corvette, but even my wife's car runs 40 profile tires on her Infiniti. In the 60s most tires were 70 profile and 60 tires didn't arrive until the late 1960s. My point is that the higher the profile the more "compliance" the tire has, and therefore when you turn the steering wheel there is a large steering wheel movement before the actual tire contact patch begins to move and therefore change the direction of the car it is atached to. Modern, very low profile tires with an aspect ratio of 30 or 35 "seem" directly connected tot he contact patch, and seem to give a much more immediate response to steering input.

 

With the OE alignment settings, radial tires should give better tracking and steering "feel" than bias ply because radials have more self aligning torque.

You didn't actually state what your alignment settings are. Have you measured them?

Cars of that era were designed with low caster because manual steering was standard. Higher caster is good for better tracking, but it increases steering effort, especially at low speed and can increase kickback.

If you believe your car lacks good tracking and/or steering "feel" the first thing to do is get it aligned to OE spec other than toe-in, which should be no more than about 1/16" total with radials.

Then thoroughly check the steering system. Has the steering gear ever been properly rebuilt? How about all the steering linkage joints. Are some worn and sloppy?

Are all the steering system components properly assembled so the steering gear is at it's high point with the wheels straight ahead and the steering wheel centered?

When I installed Michelin X radials on my SWC in 1964 all steering aspects improved dramatically - better tracking, much more linear response to steering inputs, greater maximum grip, and much better "feel" (feedback) without creating excess kickback.

I never understood why Duntov recommended NOT installing radials on C2s. Especially with high speed rated high performance radials they make the car dramatically more responsive and easier to drive.

Duke

 

Yes! Radials are a great improvement; I made this change in 1968 with less road wander and less disturbance to pavement irregularities. This was with my '65 corvette without power steering - no changes were made to the alignment specs either and I've always run with very little caster to keep the steering effort low.

Since you made no distinction about power steering or not, if you do have power, then you can get more directional stability if you increase caster. The stronger tendency to return to straight-ahead helps with power steering, but is not needed with manual steering at road speeds.

Tire aspect ratio also makes a significant difference with higher aspect ratio tires feeling less precise and less responsive - a 70 or 75 series tire will feel sloppy compared to a 40 or 50 series tire. The only partial mitigation is to use as much tire pressure as the tire maximum allows.

Also in this regard, using a wide tire on a narrow rim will feel less responsive. A rule of thumb I try to observe is to keep the tire section width no greater than 1 1/2 inches wider than the rim width. In other words, using a 205mm radial tire (205mm/25.4=8.07") on a 5 1/2" rim won't feel as responsive as using it on a 7" rim. I do violate this sometimes (I'm currently using a 215-70-15 tire on KO rims, which are 6" wide, but I don't use this for autocross as it doesn't work as well as the same tires on 7" rims.

 

Settings are .7 deg camber both sides. Caster is 1.7 deg on the left and 1.3 deg on the right. Toe is.48 total but I think this is toe out. Maybe this is part of the issue. Alignment was done on a Hunter alignment rack. I'll swing by my Corvette specialist tomorrow to ask about the toe.
Steering components all check out fine.

 

Is the toe in inches, mm, degrees. What?

You should have a paper copy of the final settings. Scan and post it.

Duke

 

My wife's car is a stock 57 Nomad, she never liked the way it "drove", years ago I removed the bias ply's and installed radials. It is the nicest driving old car I have ever owned. We are planning a cross country trip in it. Original 283 w/power pack, factory air, tinted windows and padded dash. Cruises at 70 all day, going to be a great trip. Adding radials IMO is the single greatest thing to add to any old car.

 

degrees