Geo & Setup
08-04-2014, 06:25 AM
#31
Three Wheelin'
You could measure to see if the shock piston rod comes up in the same place relative to the mounting bolts on the strut tower on both sides. That would induce an angle in the shock, we're only talking a degree so maybe a few mm further back of forward on one side would do it. This would be caused by a defect or wear in the top mount.
08-04-2014, 07:12 AM
#32
Burning Brakes
I think the rear ride height may be causing the problem, the car is very much nose down if the 127/243 figures are correct. I would look at getting the rear lower and see if this affects the numbers.
08-04-2014, 07:25 AM
#33
Three Wheelin'
Thread Starter
Heights are currently as follows: RS+3mm on the front and RS+13 on the rear. 10mm elevation of the rear won't create an aditional 1degree nose down attitude. You'd need maybe 50-60 mm to induce that and it'd effect both sides equally would it not?
08-04-2014, 07:48 AM
#34
Burning Brakes
The RS numbers are 125 / 223 both +/- 5mm. This will give about 1deg nose down. Your rear figure should be 225 to match the front, at the moment its +17 higher. What affect this has on nose down angle and corner weight I dont know but probably best to get them right and retry the caster issue.....I only suggest this as you seem to have checked all other obvious reasons!
08-04-2014, 08:06 AM
#35
Three Wheelin'
Thread Starter
rough calc with a bit of trig here
tan@ = O / A = 10mm / 2270(wheel base) -> tan^-1 = 0.25 degrees
ok, yep so it's worth doing. Just need to find the other missing 0.75 degrees
tan@ = O / A = 10mm / 2270(wheel base) -> tan^-1 = 0.25 degrees
ok, yep so it's worth doing. Just need to find the other missing 0.75 degrees
08-10-2014, 05:05 AM
#36
Three Wheelin'
Thread Starter
Spent most of yesterday working on the car again trying to identify this caster alignment issue. I got the car up on jacks and exactly level again and checked all my measurements from the previous attempt. All still good. This time I wanted to check the upper shock mount position in the body. I pulled both shock tops out and left them hanging to the side whilst supporting the lower wishbones. I then hung long plumb lines exactly central through the top mount hole in the body. A measurement was then taken from the outer pivot stud of the lower wishbone to the plumb line. I think I've found my problem. There is a 5mm fore/aft difference between these measurements each side. The side lacking in caster with the lower joint fully forward has its body mounting position for the shock top further forward. This will have the effect of reducing the caster and therefore the maximum that is attainable by adjustment. So I've found the issue but there isn't a darn thing I can (easily) do about it. I can only put this down to manufacturing tolerances (that's why they have adjustable caster to start with?) as the car is straight with no evidence of accident damage. I'll just have to live with a max caster of 3.# instead of the usual 4.#
Last edited by robt964; 08-10-2014 at 06:01 AM.
08-10-2014, 05:29 AM
#37
Burning Brakes
Top detective work! So you know the bottom wishbone positions are good but one top mount is further forward than it should be. That would mean either the inner wing is mounted too far forward or the top mount position in the wing is wrong? Is it possible to either redrill or elongate the mounting bolt holes to get the 5mm back?
08-10-2014, 05:58 AM
#38
Three Wheelin'
Thread Starter
Hmm I guess but that is one area I'd rather not touch. Another (future option) could be to remove the top mount from the shock push out the 4 mounting studs, weld fill the holes then redrill in the new position and press the studs back in. This would be a safer (studs purely maintain location of the strut and not load of the car) also be a far less visible change.
08-10-2014, 06:24 AM
#40
Three Wheelin'
Or maybe something adjustable...
http://en.intraxracing.nl/merken/por...4/por5549-cam/
http://en.intraxracing.nl/merken/por...4/por5549-cam/
Do kw do them as an option?
08-10-2014, 06:40 AM
#41
Three Wheelin'
Thread Starter
As far as I'm aware, adjustable top mounts won't provide adjustment in the correct plane. I need for/aft where as camber plates do inboard/outboard.
08-10-2014, 06:42 AM
#42
Three Wheelin'
08-10-2014, 07:07 AM
#43
Three Wheelin'
Thread Starter
Ah yes just read the link ras62 posted
It says the plate adds 18mm to the height of the shock, so the spring collars would need to be loweredby that amount to compensate. That creates a problem for the KWV3s as at RS height they're on the lower limit recommended by KW. Dropping a further 18mm would put you well into the <no not use> zone.
It says the plate adds 18mm to the height of the shock, so the spring collars would need to be loweredby that amount to compensate. That creates a problem for the KWV3s as at RS height they're on the lower limit recommended by KW. Dropping a further 18mm would put you well into the <no not use> zone.
08-10-2014, 09:17 AM
#44
Three Wheelin'
Ah yes just read the link ras62 posted
It says the plate adds 18mm to the height of the shock, so the spring collars would need to be loweredby that amount to compensate. That creates a problem for the KWV3s as at RS height they're on the lower limit recommended by KW. Dropping a further 18mm would put you well into the <no not use> zone.
It says the plate adds 18mm to the height of the shock, so the spring collars would need to be loweredby that amount to compensate. That creates a problem for the KWV3s as at RS height they're on the lower limit recommended by KW. Dropping a further 18mm would put you well into the <no not use> zone.
08-10-2014, 12:01 PM
#45
Three Wheelin'
Thread Starter
I'll give them a call on Monday and find out. One fear I have with adjustable top mounts is increased road noise 
If it were a dedicated track car I'd leap straight in but I'm determined not to degrade the road driveabilty of this car. It's all to easy to go overboard with the suspension performance upgrades and end up with a car that's so noisy/crashy/vibration that you can't wait to get out of it after 1h up the motorway. There's a fine balance. I've gone down that route with other cars and ended up selling them because in the end I just wasn't using them because they become less pleasurable/more hassle to use 90% of the time. I *want* to keep this one hence why I as good as built a new one lol
If it were a dedicated track car I'd leap straight in but I'm determined not to degrade the road driveabilty of this car. It's all to easy to go overboard with the suspension performance upgrades and end up with a car that's so noisy/crashy/vibration that you can't wait to get out of it after 1h up the motorway. There's a fine balance. I've gone down that route with other cars and ended up selling them because in the end I just wasn't using them because they become less pleasurable/more hassle to use 90% of the time. I *want* to keep this one hence why I as good as built a new one lol