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Thread: P11: Lowering Rear UCA Mounting Point

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2016-06-14 05:14:00
#1
P11: Lowering Rear UCA Mounting Point
I've been thinking about lowering the rear UCA mounting point to help the ECU be on a more aggressive side of the camber curve. After doing some researching I found out that muscle car guys do this change the camber curve and to raise the front roll center. It's called the Guldstrand Mod.

For Chevy's this mod is super simple, just lower the mounts by .5-1"


Not only does it improve the camber curve, it also raises the front roll center, which is a welcome addition.




Even though our suspensions are not your traditional double wishbone setup, It's still a SLA (Short Long Arms) style suspension, thus a lot of double wishbone concepts can apply to us.

Our UCA brackets are slant cut, which limits on how low we can go without welding. I wanted to lower the mount by 1", but the best I got was 15mm (0.59"), and to have enough meat on the mount I moved it back a few mm.


I would have moved further back to help with increase the static camber, but I was afraid that the fat Cusco's would contact the bracket.


Stock Mounting


15mm Lower, you can see the UCA having a bigger angle then stock.



Now onto the fun part, the camber curves. These are camber gains to be added to static camber (-1.30* in my case with 1" drop). Notice how the stock deadzone where there is no camber gain up or down around laden height has been completely eliminated. Negative camber also comes in faster and you gain slightly more, you also gain positive camber, which is good for the inside wheel to help create camber thrust.
(Positive travel is bump, negative travel is droop)



Changing the mounting points gave me 1/2" of toe in, even then the car was very stable and turned in very well. Adjusting the toe to be 0", now that made this mod really shine, it majorly increased the liftoff oversteer. This allows you to reduce the rear stiffness, which should help overall traction level.


UPDATE: I measured the camber curves of Stock UCA's and Cusco UCA, in stock mounting holes and the new modified location, details and graphs can be found in this thread.
Last edited by Vadim on 2016-10-04 at 13-57-32.
2016-06-14 17:51:46
#2
Just to clarify, is the travel on the left side of the graph + for wheel droop and - for compression or opposite?
2016-06-14 18:20:51
#3
No problem, negative travel is droop, positive travel is jounce. Maybe I should add labels to the graph .
2016-06-30 16:46:59
#4
Originally Posted by Vadim
I've been thinking about lowering the rear UCA mounting point to help the ECU be on a more aggressive side of the camber curve. After doing some researching I found out that muscle car guys do this change the camber curve and to raise the front roll center. It's called the Guldstrand Mod.

For Chevy's this mod is super simple, just lower the mounts by .5-1"




Not only does it improve the camber curve, it also raises the front roll center, which is a welcome addition.




Even though our suspensions are not your traditional double wishbone setup, It's still a SLA (Short Long Arms) style suspension, thus a lot of double wishbone concepts can apply to us.

Our UCA brackets are slant cut, which limits on how low we can go without welding. I wanted to lower the mount by 1", but the best I got was 15mm (0.59"), and to have enough meat on the mount I moved it back a few mm.


I would have moved further back to help with increase the static camber, but I was afraid that the fat Cusco's would contact the bracket.


Stock Mounting


15mm Lower, you can see the UCA having a bigger angle then stock.



Now onto the fun part, the camber curves. These are camber gains to be added to static camber (-1.30* in my case with 1" drop). Notice how the stock deadzone where there is no camber gain up or down around laden height has been completely eliminated. Negative camber also comes in faster and you gain slightly more, you also gain positive camber, which is good for the inside wheel to help create camber thrust.
(Positive travel is bump, negative travel is droop)



Changing the mounting points gave me 1/2" of toe in, even then the car was very stable and turned in very well. Adjusting the toe to be 0", now that made this mod really shine, it majorly increased the liftoff oversteer. This allows you to reduce the rear stiffness, which should help overall traction level.


Holy crap, how did I not think of this! I am going back to my stock length UCA to have less static camber for more straight line traction, accelerating and braking. So I can give this a shot as well while I am in there.

Awesome Vadim! I will be changing my LCA ball joint with spherical bearings and cup to adjust roll centre there as well.
2016-06-30 20:10:30
#5
Changing the mounting points gave me 1/2" of toe in, even then the car was very stable and turned in very well. Adjusting the toe to be 0", now that made this mod really shine, it majorly increased the liftoff oversteer. This allows you to reduce the rear stiffness, which should help overall traction level.


Adjusting the roll centre essentially stiffens the compression so it would roll less at the front when trial breaking or lifting off on turn in.
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