54 front end
Race Director
Joined: Apr 2015
Posts: 17,571
Likes: 3,460
From: Fresno California
What Jim is saying is dead-on. And 2 degrees is huge in the alignment world. Think of caster as rake on a bicycle or chopper. The further the front forks stick out, the more stable at speed. At the cost of slower speed flexibility and steering balance. Also, too much caster can cause harsh feedback through the steering wheel, as the front wheels ram rather than roll over potholes, etc. I would not dial any more caster into a car if it already drove straight and steered well. If it drove like a bicycle with the forks flipped around, 'nuther story.....
Thread Starter
Burning Brakes
Joined: Dec 2008
Posts: 1,123
Likes: 303
From: PURCELLVILLE VA
C1 of Year Finalist (performance mods) 2019
2017 C1 of Year Finalist
Well, I'm building a period correct Hot Rod. 283, w/2 fours and a 3 or 4 spd. I thought if the shims would improve handling I'd go for it.
Thread Starter
Burning Brakes
Joined: Dec 2008
Posts: 1,123
Likes: 303
From: PURCELLVILLE VA
C1 of Year Finalist (performance mods) 2019
2017 C1 of Year Finalist
What Jim is saying is dead-on. And 2 degrees is huge in the alignment world. Think of caster as rake on a bicycle or chopper. The further the front forks stick out, the more stable at speed. At the cost of slower speed flexibility and steering balance. Also, too much caster can cause harsh feedback through the steering wheel, as the front wheels ram rather than roll over potholes, etc. I would not dial any more caster into a car if it already drove straight and steered well. If it drove like a bicycle with the forks flipped around, 'nuther story.....
Pro
Joined: May 2014
Posts: 530
Likes: 360
From: San Clemente CA
There must have been a good rationale for engineers to use shims on all subsequent C1s. You would assume the benefits outweigh the downside. is it the radials that effect the steering effort, more so than bias ply tires?
Race Director
Joined: Feb 2007
Posts: 15,455
Likes: 8,915
From: northern california
C2 of Year Finalist (track prepared) 2019
Based on these observations, he developed several suspension changes to improve the car's handling. Included in these changes were, of course, the 2* shims and also re-located rear spring hangers to reduce the roll understeer. These changes had nothing to do with radial tires versus bias ply tires; all tires in use back then were bias ply.
So, yes, there were good reasons to make the changes. The reasons primarily involved handling at the limits of adhesion.
Jim
Race Director
Joined: Apr 2015
Posts: 17,571
Likes: 3,460
From: Fresno California
The steering effort with modern radial tires is significantly greater at low speeds than the old bias ply tire, mainly due to the radial's bigger contact patch with the pavement. I used to run bias plys on my GTO's, and the steering got a lot harder at low speeds/parking when I upgraded to radials. I have bias plys on my '61 'Vette right now, and it steers just fine. Here's a thought: how about fabricating a ONE degree positive caster shim, and trying it on for size. Might be a good upgrade/compromise for a street driven car.
