Notices
C7 Z06 Discussion General Z06 Corvette Discussion, LT4 Corvette Technical Info, Performance Upgrades, Suspension Setup for Street or Track
Sponsored by:
Sponsored by:

Turning lca eccentric for positive caster

 
Old 05-21-2019, 08:17 PM
  #1  
bhk2
CF Senior Member
Support Corvetteforum!
Thread Starter
 
bhk2's Avatar
 
Member Since: Apr 2011
Location: Kent WA
Posts: 761
Received 23 Likes on 18 Posts
Default Turning lca eccentric for positive caster

The dealer checked and recorded (took picture) of rear caster on '19 Z06. The reading, not very visible, is -0.4 and is within factory spec. The rear wheels showed identical caster readings. I occasionally track the car and read about the potential for snap oversteer and want to adjust the lca eccentric to get caster positive. Questions: Does each tic mark on the eccentric bolt correspond to a specific change in caster degree? And, if I am interested in going from neg to positive caster, looking from the rear of vehicle, which way does the eccentric bolt rotate? I cannot remember if changing caster affects camber or toe, so in reality, I will likely take it back and have the dealer realign everything. Thought it was worth a CF ask.

-0.4
bhk2 is offline  
Old 05-22-2019, 01:24 PM
  #2  
Bill Dearborn
Tech Contributor
 
Bill Dearborn's Avatar
 
Member Since: Oct 1999
Location: Charlotte (formerly Endicott, NY) NC
Posts: 33,307
Received 3,663 Likes on 2,435 Posts
Default

The marks don't really mean anything except as a reference. Rear caster setting is very touchy to adjust. Small movements of the lca cams make big swings in rear caster while also swinging camber.

You may get more caster movement using the front cam and more camber movement using the rear cam. Once set you can see large swings just tightening the cam bolts down to the 125 ft lb torque setting. The reason you see large swings in the number is because the measurement is so small with a spec of 0.0 degrees plus or minus 0.8 degrees. Getting the DSC -1.7 degrees of rear camber along with the +0.7 degrees of rear caster makes it hard to set toe since you run into a lack of adjustment range on the toe link cam. I could not get any toe in adjustment at all and the least amount of toe out I could get was about 1/32.

Bill
Bill Dearborn is offline  
Old 05-22-2019, 07:58 PM
  #3  
X25
Sr.Random input generator
Support Corvetteforum!
 
X25's Avatar
 
Member Since: Jan 2008
Location: Sammamish, WA
Posts: 4,278
Received 481 Likes on 382 Posts
Default

In order to solve that range issue (that Bill mentioned), you can remove all the washers behind the UCA mounts at the rear, and replace them with a thin washer instead (I've used 1/64" shim from Harbor Freight). GM recommends leaving one washer behind the arms, so I left the shims in case it's a mounting surface issue.

This allows you to get an additional 0.3-0.4 degrees of camber for free.

Last edited by X25; 05-22-2019 at 07:58 PM.
X25 is offline  
Old 05-22-2019, 09:51 PM
  #4  
bhk2
CF Senior Member
Support Corvetteforum!
Thread Starter
 
bhk2's Avatar
 
Member Since: Apr 2011
Location: Kent WA
Posts: 761
Received 23 Likes on 18 Posts
Default

Bill, thank you. I do recall reading about the adjustable toe links. Not sure if the dealer would touch those and that might force a DIY route. Appreciate the help.

Originally Posted by Bill Dearborn View Post
The marks don't really mean anything except as a reference. Rear caster setting is very touchy to adjust. Small movements of the lca cams make big swings in rear caster while also swinging camber.

You may get more caster movement using the front cam and more camber movement using the rear cam. Once set you can see large swings just tightening the cam bolts down to the 125 ft lb torque setting. The reason you see large swings in the number is because the measurement is so small with a spec of 0.0 degrees plus or minus 0.8 degrees. Getting the DSC -1.7 degrees of rear camber along with the +0.7 degrees of rear caster makes it hard to set toe since you run into a lack of adjustment range on the toe link cam. I could not get any toe in adjustment at all and the least amount of toe out I could get was about 1/32.

Bill
bhk2 is offline  
Old 05-22-2019, 09:56 PM
  #5  
bhk2
CF Senior Member
Support Corvetteforum!
Thread Starter
 
bhk2's Avatar
 
Member Since: Apr 2011
Location: Kent WA
Posts: 761
Received 23 Likes on 18 Posts
Default

X25, great idea. I'll swap out the uca washers with a thinner one and then schedule appt. with dealer. Appreciate the pro tip.

Originally Posted by X25 View Post
In order to solve that range issue (that Bill mentioned), you can remove all the washers behind the UCA mounts at the rear, and replace them with a thin washer instead (I've used 1/64" shim from Harbor Freight). GM recommends leaving one washer behind the arms, so I left the shims in case it's a mounting surface issue.

This allows you to get an additional 0.3-0.4 degrees of camber for free.
bhk2 is offline  
Old 05-23-2019, 01:30 AM
  #6  
HNK
CF Senior Member
 
HNK's Avatar
 
Member Since: Jan 2006
Posts: 1,005
Received 25 Likes on 23 Posts
Default

Is it better to do the caster align with weight in the driver area?? How long does it usually take to do the rears?
HNK is online now  
Old 05-23-2019, 01:44 AM
  #7  
X25
Sr.Random input generator
Support Corvetteforum!
 
X25's Avatar
 
Member Since: Jan 2008
Location: Sammamish, WA
Posts: 4,278
Received 481 Likes on 382 Posts
Default

Originally Posted by HNK View Post
Is it better to do the caster align with weight in the driver area?? How long does it usually take to do the rears?
It definitely will help. After all, this car never drives itself, and a driver (weight) on the seat makes it more accurate. And yes, it impacts all alignment numbers in my experience (though none too significantly).

Last edited by X25; 05-23-2019 at 01:44 AM.
X25 is offline  
The following users liked this post:
HNK (05-23-2019)
 


Thread Tools
Search this Thread
Quick Reply: Turning lca eccentric for positive caster


Contact Us - About Us - Archive - Advertising - Cookie Policy - Privacy Statement - Terms of Service

© 2019 MH Sub I, LLC dba Internet Brands

We are a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for us to earn fees by linking to Amazon.com and affiliated sites.
 
  • Ask a Question
    Get answers from community experts
Question Title:
Description:
Your question will be posted in: