|
Technical Chat Ask and answer technical car questions. |
|
Thread Tools |
2007-03-20, 02:11 PM | #1 |
Seņor Cheap Bastarde
Real Name: Dean Join Date: May 2003
Location: $99 Tire Store
Posts: 9,294
Car: $.04 STI
Class: Fast,Cheap & Reliable=STI
Deal, did somebody say Deal? Oh, Dean, yeah that's me.
|
Axle vs. SAI adjustment for camber?
This is probably a question for Austin, but lets see what we come up with.
As I figure it, there are to ways to adjust what we commonly refer to as Camber. 1. Adjust the angle of the axle relative to the strut at the base by use of camber bolts, etc. 2. Adjust the angle of the strut itself by use of camber plates. I am trying to figure out the pros and cons of each from a geometry perspective. Obviously camber plates are easiest to adjust, and the combination can be used to optimize tire clearance issues, but what are the basic geometry considerations to each. Is one more likely to cause bump steer, or some other negative effect? I am going to keep researching, but perhaps Austin or someone else has already done so... Here is some basic alignment stuff to get you started if you are not familiar with these terms. http://www.familycar.com/Alignment.htm
__________________
I am a Commodore PET --- Now get off my lawn you kids... |
2007-03-20, 02:43 PM | #2 |
EJ22T
Join Date: Sep 2003
Location: Reno
Posts: 9,445
Car: '93/'01 GF6, mostly red
Class: 19 FP
|
I think strut angle is better because you get the same static camber but a better curve under roll.
__________________
FWD is the new AWD |
2007-03-20, 03:10 PM | #3 | |
Seņor Cheap Bastarde
Real Name: Dean Join Date: May 2003
Location: $99 Tire Store
Posts: 9,294
Car: $.04 STI
Class: Fast,Cheap & Reliable=STI
Deal, did somebody say Deal? Oh, Dean, yeah that's me.
|
Quote:
Taking an extreme example. With a 0 degree strut angle (vertical) and 88 degree angle at the axle, camber is -2 degrees at both zero and 90 degrees of strut rotation. With a -2 degree strut angle and 90 degree angle at the axle, camber is -2 degrees at zero degrees of strut rotation but 0 degrees at 90 degrees of strut rotation. (The tire has rotated the 2 degrees, I think.)
__________________
I am a Commodore PET --- Now get off my lawn you kids... |
|
2007-03-20, 03:17 PM | #4 |
EJ22T
Join Date: Sep 2003
Location: Reno
Posts: 9,445
Car: '93/'01 GF6, mostly red
Class: 19 FP
|
Okay, expanding. Aside from the better camber curve you get from tipping in your strut tops 2 degrees, you get a better castor curve too. Leave the ridonkulous extreme non-real-world examples out and Dean.
I need to sit down and expand my thinking on it whne I haev more time tonight but it seems at first glance to me that by reducing the angle between strut and axle, you slow down the camber loss as the strut is shortened under compression.
__________________
FWD is the new AWD |
2007-03-20, 03:33 PM | #5 |
Seņor Cheap Bastarde
Real Name: Dean Join Date: May 2003
Location: $99 Tire Store
Posts: 9,294
Car: $.04 STI
Class: Fast,Cheap & Reliable=STI
Deal, did somebody say Deal? Oh, Dean, yeah that's me.
|
You will have to explain the "better camber curve" as well as the caster impact. as caster is 90 degrees from SAI, I would think they are completely independent. They both affect dynamic camber, but not each other as far as I know.
__________________
I am a Commodore PET --- Now get off my lawn you kids... |
2007-03-20, 07:00 PM | #6 |
EJ22
Join Date: Apr 2006
Location: Reno
Posts: 148
Car: RED WRX
Class: Spectator
Mangia la mia polvere
|
OK, so you guys talking about this got me to sit down and make a model of this. Do any of you have any measurements of the Impreza front suspension? Like Control Arm length, strut length and travel etc... (also distance from top of the strut to control arm pivot) I have a working model but have no clue the sizes of anything.
Offhand, with silly guesses for dimensions, I can actually get camber _gain_ if the strut angle is right, even with the control arm up past horizontal. However I may have some dimensions way off. |
2007-03-22, 09:19 AM | #7 | |
Nightwalker
Real Name: Austin Join Date: Dec 2002
Location: Oshkosh, WI
Posts: 4,063
Car: '13 WRX
YGBSM
|
Quote:
For practicality reasons, I would keep the camber plates roughly centered in their range of adjustment and use #1 & #3 as your gross adjustments in the shop to get the camber close to where you want it. Then use the camber plates as your fine adjustment for final alignment & at-the-track adjustment. You don't want to have to monkey with #1 at the track if you can avoid it. SAI has noticeable bad effects on dynamic camber when the wheels are steered, but it's a more important consideration during design of the suspension than when the suspension's already been built and you're just trying to align the car. Making sure you have enough range of adjustment in your camber plates is more important IMO than trying to absolutely mimimze the SAI by keeping your upper strut bearings as far outboard as you can get them. You never know when you're going to want/need to make a camber change in either direction.
__________________
"None of you seem to understand. I'm not locked in here with you.. you're locked in here with me." |
|
2007-03-23, 12:06 PM | #8 |
EJ22
Join Date: Mar 2006
Location: south lake tahoe
Posts: 234
Car: L
just push the brake pedal.
|
does anyone know how much anti dive/lift is built into our system? #3 as described above changes dive/lift too, and i haven't seen it mentioned.
__________________
www.monzospeed.com |
2007-03-23, 01:30 PM | #9 |
Nightwalker
Real Name: Austin Join Date: Dec 2002
Location: Oshkosh, WI
Posts: 4,063
Car: '13 WRX
YGBSM
|
I guess technically it would since any elevation change in the inner LCA pivots affects the side view geometry as well, but I think any rise & fall in pivot height from an eccentric adjuster would result in really miniscule changes in your side view swing arm length, not enough to notice any effect in the anti's.
__________________
"None of you seem to understand. I'm not locked in here with you.. you're locked in here with me." |
|
|
Similar Threads | ||||
Thread | Thread Starter | Forum | Replies | Last Post |
Coilover adjustment question? | ddub | Technical Chat | 19 | 2006-02-04 01:25 PM |
oHs n0S!!!!1! Teh Scott's C4r is teh f4ll1ng ap4rts!?!?!!1! | sperry | Technical Chat | 19 | 2003-09-29 08:03 PM |