Rear lower control arm endlink/shocks ratio adjustments - Toyota GR86, 86, FR-S and Subaru BRZ Forum & Owners Community

Brzerker · 01-04-2018, 01:49 AM

Hi all,

Just wondering if anyone uses the extra holes (left, center, right) in their adjustable rear lower control arms to tune stiffness for the rear suspension/sway bars.

Tried looking for information on how much stiffer or softer can we expect when switching to different configurations, not much info on these. Hopefully, some can share their experiences on these.

churchx · 01-04-2018, 03:06 AM

Aren't those different mount-holes more meant for rather different lowering/drop, then for suspension stiffness tuning? As in if one wishes for extreme drop to relocate lower mountpoint aswell, to keep some of coilovers travel, in similar fashion like special upper mounts do? Leave stiffness tuning to rollbars & coilovers themselves, no?

wparsons · 01-04-2018, 09:13 PM

^^ Those specific holes pointed to by the arrow are to adjust the motion ratio for the sway bar, which would effectively tune the stiffness a bit. The holes are beside each other, not above or below.

Now, the shock mounting point has two rows of three, one above the other, that could be used to gain bump travel.

As for how much stiffer or softer, it's just math based on how much further in/out the extra holes are. It's not going to be a drastic difference though.

Brzerker · 01-04-2018, 11:36 PM

Quote:

Originally Posted by wparsons

^^ Those specific holes pointed to by the arrow are to adjust the motion ratio for the sway bar, which would effectively tune the stiffness a bit. The holes are beside each other, not above or below.

Now, the shock mounting point has two rows of three, one above the other, that could be used to gain bump travel.

As for how much stiffer or softer, it's just math based on how much further in/out the extra holes are. It's not going to be a drastic difference though.

Do you happen to have any references on calculating the stiffness in regards to the extra holes?

I would be trying it out to get a butt feel but some numbers would be nice.

Racecomp Engineering · 01-04-2018, 11:51 PM

You'll have to measure the change in the motion ratio (which would increases as you move the mounting point out towards the wheel).

Wheel rate = spring rate * motion ratio^2

Same for the sway bar. There are estimates of the spring rate of the swaybars floating around somewhere on here.

- Andrew

jamal · 01-05-2018, 01:05 AM

The extra swaybar holes can be useful if you don't have an adjustable bar and want to make the rear softer or stiffer. Farther out should make it a touch stiffer.

Having a lower hole on the shock mount is also handy if the car is low because it'll give you back some much needed bump travel.

But all those other extra ones for the strut i would probably not ever want to use.

01-04-2018, 01:49 AM	#1
Brzerker Senior Member Join Date: Jan 2015 Drives: World Rally Blue BRZ Location: Singapore Posts: 150 Thanks: 24 Thanked 39 Times in 25 Posts Mentioned: 0 Post(s) Tagged: 1 Thread(s)	Rear lower control arm endlink/shocks ratio adjustments Hi all, Just wondering if anyone uses the extra holes (left, center, right) in their adjustable rear lower control arms to tune stiffness for the rear suspension/sway bars. Tried looking for information on how much stiffer or softer can we expect when switching to different configurations, not much info on these. Hopefully, some can share their experiences on these. __________________

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01-04-2018, 03:06 AM	#2
churchx Senior Member Join Date: Mar 2015 Drives: 2014 GT86 Location: Latvia, Riga Posts: 4,334 Thanks: 696 Thanked 2,086 Times in 1,436 Posts Mentioned: 53 Post(s) Tagged: 1 Thread(s)	Aren't those different mount-holes more meant for rather different lowering/drop, then for suspension stiffness tuning? As in if one wishes for extreme drop to relocate lower mountpoint aswell, to keep some of coilovers travel, in similar fashion like special upper mounts do? Leave stiffness tuning to rollbars & coilovers themselves, no?

01-04-2018, 11:51 PM	#5
Racecomp Engineering Join Date: Nov 2011 Drives: 2016 BRZ, 2012 Paris Di2 & 2018 STI Location: Severn, MD Posts: 5,511 Thanks: 3,536 Thanked 7,406 Times in 3,030 Posts Mentioned: 310 Post(s) Tagged: 9 Thread(s)	You'll have to measure the change in the motion ratio (which would increases as you move the mounting point out towards the wheel). Wheel rate = spring rate * motion ratio^2 Same for the sway bar. There are estimates of the spring rate of the swaybars floating around somewhere on here. - Andrew

01-05-2018, 01:05 AM	#6
jamal Senior Member Join Date: Nov 2011 Drives: Legacy GT Location: compton Posts: 534 Thanks: 9 Thanked 367 Times in 205 Posts Mentioned: 11 Post(s) Tagged: 0 Thread(s)	The extra swaybar holes can be useful if you don't have an adjustable bar and want to make the rear softer or stiffer. Farther out should make it a touch stiffer. Having a lower hole on the shock mount is also handy if the car is low because it'll give you back some much needed bump travel. But all those other extra ones for the strut i would probably not ever want to use.

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