Speed-Talk is running on www.Speed-Talk.com

IMPORTANT: Update your bookmarks to https://www.speed-talk.com/forum/
(Right-click the URL and select "Bookmark this link")

Question - Improved Camber Curve

Shocks, Springs, Brakes, Frame, Body Work, etc

Moderator: Team

User avatar
MadBill
HotPass
HotPass
Posts: 14758
Joined: Tue Nov 15, 2005 10:41 am
Location: The Great White North

Re: Question - Improved Camber Curve

Post by MadBill »

With all the suspension mods under consideration, at least one more parameter will need to be addressed, i.e. bump steer.
Felix, qui potuit rerum cognscere causas.

Happy is he who can discover the cause of things.
enigma57
Guru
Guru
Posts: 1922
Joined: Sun Oct 07, 2007 11:59 pm
Location: Galt's Gulch

Re: Question - Improved Camber Curve

Post by enigma57 »

I agree, Bill. Bump steer must be addressed any time front suspension and steering mods are proposed. However, when retaining the OEM steering gear and original locations of control arm pivot points and ball joints, I have not encountered bump steer on these '55 - '57 Chevys in years past.

Initially, when I was planning for more extensive mods to steering, suspension and drivetrain in support of the 427 small block stroker engine I was building 20 years ago..... The plan was to go with optional 1975 Chevy station wagon/cop car 12" disc brake rotors and build mounting brackets for Aussie PBR calipers (functionally, the same calipers as Baer Brakes use)...... And to install a rear steer power rack and pinion unit from the early '90s Buick FWD T-type and cop cars (quicker power steering with more road feel). Because of the wider position of inner tie rod ends with the R&P unit though...... Either the R&P inner tie rod position must be shortened or the control arm pivot points and ball joint positions must be modified to prevent bump steer...... Much as Jim Meyers did when fitting the Buick R&P units to these cars.

There is a way to do it without modifying the R&P unit (retain original steering cross link and add a 2nd idler arm to replace original steering box and pitman arm...... Then fit R&P unit to move original cross link) but I see no reason to take that step.

So will rebuild original steering and add greasable needle bearings to replace OEM rubber idler arm bushings and modify only the ends of the '57 lower control arms to allow mounting the lower ball joints and larger drum brakes and spindles from the '59 - '64 cars. Planning on keeping the OEM ball joint positions (both upper and lower). May install a set of shorter steering arms I have here to speed up the slow 20:1 OEM manual steering box ratio. But other than the usual stiffening of spring rates and shock valving and adapting large diameter anti-sway bars front and rear, I will keep front suspension and steering mods to a minimum.

I will be getting back into this project when I am recovered more from the medical treatment and will let you know how it works out.

Best regards,

Harry
enigma57
Guru
Guru
Posts: 1922
Joined: Sun Oct 07, 2007 11:59 pm
Location: Galt's Gulch

Re: Question - Improved Camber Curve

Post by enigma57 »

P.S. >>> Bill, I dropped the ball in my earlier post. By increase in bump steer, I assume you mean increased toe-out from bump travel resulting from installation of either taller spindles or upper ball joints having 0.5" taller studs in an effort to increase negative camber gain?

Thanks,

Harry
User avatar
MadBill
HotPass
HotPass
Posts: 14758
Joined: Tue Nov 15, 2005 10:41 am
Location: The Great White North

Re: Question - Improved Camber Curve

Post by MadBill »

You'll have to research the subtitles (lots of info out there), but almost everything you're planning, including caster changes, affects it and the effects especially for roll oversteer can be pronounced. Some race car builders won't settle for more than say 0.010" toe change through perhaps 5" of suspension travel. Production street cars with rubber bushings are far less sensitive but it should always be a consideration.
Felix, qui potuit rerum cognscere causas.

Happy is he who can discover the cause of things.
dannobee
HotPass
HotPass
Posts: 314
Joined: Mon Nov 04, 2019 9:01 pm
Location:

Re: Question - Improved Camber Curve

Post by dannobee »

And to further show the importance of bump steer, in circle track racing I'd shoot for 0.000" toe change over 4" of travel on the right side and a toe out of 0.020" per inch of travel on the left side as that side lifts. Zero change in either side with 4" travel on the road race car.

I cringe and shake my head when I see some car build on teevee and the fabricator welds on suspension brackets by guess and by golly. No engineering or forethought in the process at all.
enigma57
Guru
Guru
Posts: 1922
Joined: Sun Oct 07, 2007 11:59 pm
Location: Galt's Gulch

Re: Question - Improved Camber Curve

Post by enigma57 »

Thanks, Bill and Danno! I will look into this further and educate myself on suspension mods more before making any hard and fast decisions on suspension mods.

Best regards,

Harry
Post Reply