Is my ride height too low?
03-09-2017, 08:44 PM
#76
Three Wheelin'
Thread Starter
Yes, that is a problem.
Your Castor is minimized, this causes the rear to react very quickly and can be hard to keep up w/. Twitchy is a common description. The wheel is moved down and forward relative to the chassis.
RSR spec was +3° 00' max @93mm ride height
I don't know what the correlation is between the #s on the gauge that you have and degrees,
Most stable and slowest rear will be from having the bubble near the other end at 0. From there you experiment, adjust the suspension to move it forward until you are uncomfortable w/ it than back off a bit. You want the rear to react as fast as possible but that still feels comfortable for you. Everyone's skill and comfort level is different. You want the gauge to have the same reading on both sides.
This process moves the wheel up and back relative to the chassis.
Your Castor is minimized, this causes the rear to react very quickly and can be hard to keep up w/. Twitchy is a common description. The wheel is moved down and forward relative to the chassis.
RSR spec was +3° 00' max @93mm ride height
I don't know what the correlation is between the #s on the gauge that you have and degrees,
Most stable and slowest rear will be from having the bubble near the other end at 0. From there you experiment, adjust the suspension to move it forward until you are uncomfortable w/ it than back off a bit. You want the rear to react as fast as possible but that still feels comfortable for you. Everyone's skill and comfort level is different. You want the gauge to have the same reading on both sides.
This process moves the wheel up and back relative to the chassis.
Do I have this wrong?
03-09-2017, 08:47 PM
#77
Three Wheelin'
Thread Starter
this is also true but doesn't address the real issue
less castor means less toe change w/ rear travel, but the issue is that the rear now reacts faster, sometimes to the point where it is uncomfortable to drive. More caster increases toe change w/ wheel travel, this slows down the reaction of the rear and makes the car more stable, but it won't turn as well.
I have mine adjusted to as low(little caster) as is comfortable, the limit is turn 3 at WGI, I feel a slight twitch in the transition from left to right across the track, any more and I would be uncomfortable w/ it. It's totally comfortable at every other corner on every track.
less castor means less toe change w/ rear travel, but the issue is that the rear now reacts faster, sometimes to the point where it is uncomfortable to drive. More caster increases toe change w/ wheel travel, this slows down the reaction of the rear and makes the car more stable, but it won't turn as well.
I have mine adjusted to as low(little caster) as is comfortable, the limit is turn 3 at WGI, I feel a slight twitch in the transition from left to right across the track, any more and I would be uncomfortable w/ it. It's totally comfortable at every other corner on every track.
Since it takes a full alignment to change it, I don't know that I'll get the chance to experiment with it too much more unless it feels 'off' again.
03-09-2017, 08:49 PM
#78
Three Wheelin'
Thread Starter
It is a shame that it was butchered but in the end its just one more thing to work through and I'll make sure its made right.
On the upside it has forced me to dig in and learn more than I would have otherwise.
Last edited by Tlaloc75; 03-09-2017 at 09:15 PM.
03-09-2017, 09:25 PM
#79
Taking caster out moves the wheel forward and down, this causes the bubble to float to the high numerical end of your gauge. This means that 8 is min caster and 0 is max caster.
Since yours is messed up any way, experiment w/ it.
03-09-2017, 10:01 PM
#80
Three Wheelin'
Thread Starter
Let me see if I understand how it works theoretically. If I extend the KT arm it moves the top of the wheel backwards, increasing caster. If I shorten the KT arm it moves the top of the wheel forwards, decreasing caster. I figure it must work this way because the wheel is rotating over the top of the a-arm balljoint which is static in location. Is this correct?
I've observed that when I hold the gauge and move the top of it forward the bubble moves towards 0, if I move the top of the gauge backwards the bubble moves toward 8. So I think that corresponds to less caster goes toward 0?
Last edited by Tlaloc75; 03-09-2017 at 10:18 PM.
03-10-2017, 10:19 AM
#81
Its already at the shop unfortunately, so I can't experiment further.
Let me see if I understand how it works theoretically. If I extend the KT arm it moves the top of the wheel backwards, increasing caster. If I shorten the KT arm it moves the top of the wheel forwards, decreasing caster. I figure it must work this way because the wheel is rotating over the top of the a-arm balljoint which is static in location. Is this correct?
I've observed that when I hold the gauge and move the top of it forward the bubble moves towards 0, if I move the top of the gauge backwards the bubble moves toward 8. So I think that corresponds to less caster goes toward 0?
Let me see if I understand how it works theoretically. If I extend the KT arm it moves the top of the wheel backwards, increasing caster. If I shorten the KT arm it moves the top of the wheel forwards, decreasing caster. I figure it must work this way because the wheel is rotating over the top of the a-arm balljoint which is static in location. Is this correct?
I've observed that when I hold the gauge and move the top of it forward the bubble moves towards 0, if I move the top of the gauge backwards the bubble moves toward 8. So I think that corresponds to less caster goes toward 0?
03-10-2017, 10:47 AM
#82
Three Wheelin'
Thread Starter
This is the passenger side rear wheel. The red arrow shows the top of the wheel moving forward and down. This is how the wheel moves when reducing caster, correct?
Note the highly realistic KT gauge in blue
.
03-10-2017, 11:38 AM
#83
The red arrow is backward, it is clockwise from the trans side, cc from the street side
03-10-2017, 12:02 PM
#84
Three Wheelin'
Thread Starter
I thought reducing caster toward 0 degrees would move the wheel forward like it does on the front of the car? Adding caster would move the top of the wheel backwards in relation to the balljoint connection point at the base of the wheel carrier? Looking at suspension diagrams the center of the wheel carrier appears to sit behind the a-arm balljoint so we are looking at positive caster here, not negative.
I really want to understand this and I feel like I'm really close but not... quite... there...
Your clockwise notation is also confusing to me since it would reverse depending on which wheel you are looking at. Clockwise (from transmission) moves the wheel forward on the driver's side and backwards on the passenger's side.
Once I understand how it works, I can correlate that to what you've said earlier in terms of where the KT should be, correlate that to my gauge and then feel comfortable I've picked a good adjustment setting.
Help!
03-10-2017, 12:22 PM
#85
Wow, I'm having trouble understanding that.
I thought reducing caster toward 0 degrees would move the wheel forward like it does on the front of the car? Adding caster would move the top of the wheel backwards in relation to the balljoint connection point at the base of the wheel carrier? Looking at suspension diagrams the center of the wheel carrier appears to sit behind the a-arm balljoint so we are looking at positive caster here, not negative.
I really want to understand this and I feel like I'm really close but not... quite... there...
Your clockwise notation is also confusing to me since it would reverse depending on which wheel you are looking at. Clockwise (from transmission) moves the wheel forward on the driver's side and backwards on the passenger's side.
Once I understand how it works, I can correlate that to what you've said earlier in terms of where the KT should be, correlate that to my gauge and then feel comfortable I've picked a good adjustment setting.
Help!
I thought reducing caster toward 0 degrees would move the wheel forward like it does on the front of the car? Adding caster would move the top of the wheel backwards in relation to the balljoint connection point at the base of the wheel carrier? Looking at suspension diagrams the center of the wheel carrier appears to sit behind the a-arm balljoint so we are looking at positive caster here, not negative.
I really want to understand this and I feel like I'm really close but not... quite... there...
Your clockwise notation is also confusing to me since it would reverse depending on which wheel you are looking at. Clockwise (from transmission) moves the wheel forward on the driver's side and backwards on the passenger's side.
Once I understand how it works, I can correlate that to what you've said earlier in terms of where the KT should be, correlate that to my gauge and then feel comfortable I've picked a good adjustment setting.
Help!
03-10-2017, 08:44 PM
#86
Three Wheelin'
Thread Starter
Quick update. I got my car back from the shop today and they changed ride height to 140/130. They did not have time to do corner balance or to fix the KT yet, that's going to happen next week. So the good news is I got to feel what a change to ride height alone feels like.
Result is that car feels much better. I must have been getting some bump steer in front and some in back as well. The car is not wandering at all any more, feels much smoother over lumpy pavement and I can just drive without constant focus.
Since they didn't do the alignment yet it also means I can experiment with the KT settings and see how they work. Should be a fun weekend!
Result is that car feels much better. I must have been getting some bump steer in front and some in back as well. The car is not wandering at all any more, feels much smoother over lumpy pavement and I can just drive without constant focus.
Since they didn't do the alignment yet it also means I can experiment with the KT settings and see how they work. Should be a fun weekend!
03-11-2017, 01:00 PM
#87
Rennlist Member
I look forward to hearing the results of playing with KT alone. When I went from 5.5 to 3.5 it was part of a whole bunch of other stuff so I can't be sure what did what. I do know the car responds to steering input like never before. I did not do a lot in the rear (solid subframe bushings and RS KT and CA bushings) and none of it was really worn out (31k miles) so I have to believe the KT settings played a big role.
Do you have a way to check toe settings after playing with KT? If not the results will be skewed.
Do you have a way to check toe settings after playing with KT? If not the results will be skewed.
03-11-2017, 01:13 PM
#88
Three Wheelin'
Thread Starter
I look forward to hearing the results of playing with KT alone. When I went from 5.5 to 3.5 it was part of a whole bunch of other stuff so I can't be sure what did what. I do know the car responds to steering input like never before. I did not do a lot in the rear (solid subframe bushings and RS KT and CA bushings) and none of it was really worn out (31k miles) so I have to believe the KT settings played a big role.
Do you have a way to check toe settings after playing with KT? If not the results will be skewed.
Do you have a way to check toe settings after playing with KT? If not the results will be skewed.
My thinking is that I'll move the side that's 8.5 to match the other so they are both at 6.5. Minimum change to even them up and then see if I can feel a difference.
I'm quite amazed at how different the car feels with the ride height adjustment. The feel has changed from twitchy, slightly punishing go-kart to mature GT with a 10mm rise in height. I need to get into the corners a bit more to finalize my thinking. Twitchy go-kart was fun but would be hard to deal with on a long road trip. Just amazing how much impact alignment and height settings can have on how these cars feel.
As surmised earlier in the thread, the suspension settling probably moved my toe and camber a bit.
03-11-2017, 03:54 PM
#89
Racer
FWIW, I dug up the report for my last alignment. Prior to this, the front was about 5 mm lower and I didn't like how it handled (too twitchy, at least, that is how it seemed to me). The camber and toe settings were recommended by the shop as being appropriate for street use, giving some consideration to tire wear. I've been very happy with how the car handles. I set the PSS10 damping for 3 front and 4 rear (4 front and 5 rear also works well).
Front ride height:
140 mm
Rear ride height:
127 mm
All of these measurements are in degrees...
Front Camber:
L = -0.3, R = -0.3
Front Caster:
L = 5.1, R = 5.4
Front Toe:
L = 0.05, R = 0.05
Front SAI (I don't recall what this is ??)
L = 20.5, R = 20.7
Rear Camber:
L = -1.2, R = -1.2
Rear Toe:
L = 0.19, R = 0.18
I don't have the settings for the KT; but, I know that they did adjust it. They were delayed in getting my car back to me because they had to replace the control arms due to the eccentric being frozen on one side, and they had to order the Motorsport version of the KT tool from Darin Fister.
Front ride height:
140 mm
Rear ride height:
127 mm
All of these measurements are in degrees...
Front Camber:
L = -0.3, R = -0.3
Front Caster:
L = 5.1, R = 5.4
Front Toe:
L = 0.05, R = 0.05
Front SAI (I don't recall what this is ??)
L = 20.5, R = 20.7
Rear Camber:
L = -1.2, R = -1.2
Rear Toe:
L = 0.19, R = 0.18
I don't have the settings for the KT; but, I know that they did adjust it. They were delayed in getting my car back to me because they had to replace the control arms due to the eccentric being frozen on one side, and they had to order the Motorsport version of the KT tool from Darin Fister.
03-11-2017, 04:01 PM
#90
Three Wheelin'
Thread Starter
That's great, thanks for sharing.
Its very close to what I have for ride height - within a couple mm. The alignment is similar except I'm going to run a little more camber: 1.2 front and 1.7 rear.
I'm still running PSS10 at 5 front and 6 rear and continuing to like that level of shock damping. Once I'm aligned again I'll probably experiment some more to see how it feels. I'm surprised at how much more supple and comfortable the suspension feels at the higher ride height.
It looks like we are converging on very similar settings.
Its very close to what I have for ride height - within a couple mm. The alignment is similar except I'm going to run a little more camber: 1.2 front and 1.7 rear.
I'm still running PSS10 at 5 front and 6 rear and continuing to like that level of shock damping. Once I'm aligned again I'll probably experiment some more to see how it feels. I'm surprised at how much more supple and comfortable the suspension feels at the higher ride height.
It looks like we are converging on very similar settings.