When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
Proper caster setting for a 1969 Cutlass Convertible
I had a bunch of new suspension parts (springs, disc conversion kit, front and rear sway bars, shocks, rims and tires) installed on my 1969 Cutlass convertible and we are wanting to set the front end caster as far positive for better handling down the road, which he has already done. The initial setting was 8 degrees positive(UPDATE caster was actually set at 2 degrees positive NOT 8), with that setting it does well on the highway but when I drive through a long curve or turn like a 55mph on-ramp from one interstate to another interstate, when the car "slightly bounces" through the highways expansion joints, the steering wheel pulls slightly, enough to make you pucker a bit. I read here that the most we can go with positive caster is about 2 to 3 degrees. Any input would be appreciated
Unless you've changed to aftermarket upper control arms, I don't know how you can get 8 deg of caster angle with the stock suspension. I'd be surprised if you can get 5 deg. I would certainly use more than 2 or 3 deg if there's enough adjustment.
Unless you've changed to aftermarket upper control arms, I don't know how you can get 8 deg of caster angle with the stock suspension. I'd be surprised if you can get 5 deg. I would certainly use more than 2 or 3 deg if there's enough adjustment.
Yes, My suspension guy said generally he can only get 2 or 3 but he did "something" to allow for more, I cant remember exactly what he did but at the time when he explained it to me it made sense.
Yes, My suspension guy said generally he can only get 2 or 3 but he did "something" to allow for more, I cant remember exactly what he did but at the time when he explained it to me it made sense.
Well, without knowing exactly what was done to the car, it's hard to offer useful info on the problem. Caster alone won't cause your "pucker" problem, in fact it should make the car more stable.
Stix:
This sounds like a bump steer issue. The toe is changing as the suspension cycles up & down causing the car to "steer" itself. Without knowing what parts have been replaced or modified I can't speak directly to your set-up, but adding or subtracting caster changes the pickup point location of the outer tie rod enough that it no longer tracks the lower control arm movement. Here's a quick example; the stock steering arms are about 6" long, changing the caster setting from 0 degrees to +8 degrees will raise the tie rod end about 7/8" of an inch. You can compensate for this with different steering arms, installing adjustable height tie rod ends or reducing the camber setting.
To measure bump steer you have to remove the spring and measure the toe change while cycling the suspension up and down. There are bump steer gauges or measuring kits available that can make the process a bit easier but you can mark the ties and take your own measurements as well. Most well designed factory suspensions have around .040" of toe change for every 1" inch of suspension travel (race cars are designed with only .020" toe change/1" of travel). The bumpsteer kits include a longer tie rod end stud and spacers of various thickness to lower the tie rod end - see pic below. I've also included a link to a Motortrend article that does a pretty good job explaining all this. Hope this helps!
Stix:
This sounds like a bump steer issue. The toe is changing as the suspension cycles up & down causing the car to "steer" itself. Without knowing what parts have been replaced or modified I can't speak directly to your set-up, but adding or subtracting caster changes the pickup point location of the outer tie rod enough that it no longer tracks the lower control arm movement. Here's a quick example; the stock steering arms are about 6" long, changing the caster setting from 0 degrees to +8 degrees will raise the tie rod end about 7/8" of an inch. You can compensate for this with different steering arms, installing adjustable height tie rod ends or reducing the camber setting.
To measure bump steer you have to remove the spring and measure the toe change while cycling the suspension up and down. There are bump steer gauges or measuring kits available that can make the process a bit easier but you can mark the ties and take your own measurements as well. Most well designed factory suspensions have around .040" of toe change for every 1" inch of suspension travel (race cars are designed with only .020" toe change/1" of travel). The bumpsteer kits include a longer tie rod end stud and spacers of various thickness to lower the tie rod end - see pic below. I've also included a link to a Motortrend article that does a pretty good job explaining all this. Hope this helps!
Thanks for the write up. I found out today that the caster is only at 2 degree positive, my mechanic guy got my car mixed up with another car so Im NOT at 8 degrees. So the bump steer tie rods and/or bump steer kit would not help me if Im correct?
I mean EXACTLY what did your suspension guy do to achieve 8 deg caster, which is impossible without modifying something.
My mechanic said he was mistaken when he told me the caster was set at 8 degrees positive, he was mixing my car up with another.
Mine is actually at 2 degrees positive. Front sway bar is a UNI 1", rear sway bar UNI and I believe is 3/4", springs are Hotchkis 1" lowered, all new A arm bushings and ball joints, steering linkage is tight, new shocks, I am using the Inline Tube spindles/disc brake set up.
Thanks for the reply, my caster is actually 2 degrees positive NOT 8 degrees positive so would this kit help me issue or should I be looking for another fix? Thanks
It will certainly help with the bump steer issue, but some upper control arms that allow for more positive caster will make i big difference also. From what i have read, taller upper ball joints that allow for more distance between the upper and lower control arms are supposed to improve the angles of the flawed A-body front suspension as well.
Caster is for steering feel and to help the steering return to center on its own. Camber helps the car through the curve and tow makes it track straight. These cars were not designed to be cutting corners at high speed and feeling like your floating on air. Your tires may also be over or under inflated causing your issues.
