How to Use Whatever Rear Spring You Want

[P71Nero]

Hello, I have a 2013 Lincoln MKS EcoBoost I've been using as a track car. Mechanically almost identical to a Taurus SHO. The adaptive suspension the MKS is equipped with may have a sport mode, but it's not suited to this kind of use. My shocks were all either on their last leg or completely dead, so I ordered some of the BC Racing DS Series coilovers. Their default rates are 6kg/mm front, 8kg/mm rear. 8kg/mm seemed much too soft for the rear though, as I had taken measurements of the rear control arms and found that the motion ratio was 0.578. With this, I found the rear spring should be at least 12kg/mm, and I decided I wanted to use a 14kg/mm spring.

The problem is, BC doesn't have options for the rear rate. The rear springs are not a conventional spring design. I ordered the coilovers from their site with the 12k rear spring and I was told they only had an 8k that would fit the car. So I went with that, and looked for a way to adapt a linear coilover spring to the rear. I discovered that the 350Z uses a rear spring of the same dimensions in BC's kits, but they also have an option to get the 350Z coilovers with a lower spring perch for linear coilover springs. These perches can be ordered separately (D-17-LSA), so I ordered them along with some 7" 14k Swift Springs. (As of August 2022 I have gone to a 14k front/28k rear setup)



They do in fact fit the car and seem to work perfectly. I haven't track tested the car yet with the new setup yet, and it still needs an alignment, but if I do ever need to change rates in the future I will now be able to use whatever rate I want for both front and rear.

[bpd1151]

Interesting and an outstanding, creative way to achieve your goal by mix/matching.

Please report back and let us all know how your experiences are with them. Track, or motoring around off the track.

Sent from my SM-N986U1 using Tapatalk

[P71Nero]

I plan on track testing the car this Saturday at Streets of Willow. I just added some more transmission cooling as the PP Trans cooler by itself wasn't cutting it. I also just got the car aligned to -2.8 camber in front and -2.0 in rear, zero toe. The settings the BC coilovers were at from the factory seemed way too stiff. I ended up turning them to full soft then turning the fronts up by 2 clicks and the rear up by 4 clicks. The ride quality is similar to the MKS sport mode now but body roll is enormously reduced as well as brake dive. My previous personal best at this track was 1:29 while on stock suspension and 275/40R18 Nitto NT555 G2s. I will be on 275/40R18 Goodyear Eagle F1 Supercar 3s for the upcoming event.

[P71Nero]

I updated my setup, put the 14k springs in the front and put 28k springs in the rear. I'm really happy with how it handles now and the ride actually isnt bad unless its a really bumpy road. At this point the biggest issue i'm having is the temperatures out here in Nevada and Southern California. I can usually only make it 1 or 2 laps before the car goes into limp mode. I'm looking into getting a custom radiator made by a local shop that will be able to withstand the sustained full power of the vehicle. Ideally i'd want to get the gearhead turbos and some downpipes at some point but theres no point in adding power when the cooling system cant withstand the current power in track conditions.

[Macgyver]

I updated my setup, put the 14k springs in the front and put 28k springs in the rear. I'm really happy with how it handles now and the ride actually isnt bad unless its a really bumpy road. At this point the biggest issue i'm having is the temperatures out here in Nevada and Southern California. I can usually only make it 1 or 2 laps before the car goes into limp mode. I'm looking into getting a custom radiator made by a local shop that will be able to withstand the sustained full power of the vehicle. Ideally i'd want to get the gearhead turbos and some downpipes at some point but theres no point in adding power when the cooling system cant withstand the current power in track conditions.

What thermostat are you using ?

[P71Nero]

What thermostat are you using ?

170 degree that i got from gearhead. I think the issue comes down to putting down full power for an extended duration during 100+ degree temperatures. The MKS has no cooling trouble towing my Ford Focus up mountains at 75mph so i doubt theres anything actually wrong with the cooling system. It seems that the MKS and non-PP SHOs have a 1" thick core while the PP SHO has a 1.25" core from looking at the specs on RockAuto, so I could always try the thicker PP radiator if I can't get something made for a reasonable price. I know the PP SHO is designed for road course/track use, but since it has the same amount of power as the normal SHO and the MKS i'm concerned it still wouldn't be enough cooling for my increased power levels.

[802SHO]

Hello, I have a 2013 Lincoln MKS EcoBoost I've been using as a track car. Mechanically almost identical to a Taurus SHO. The adaptive suspension the MKS is equipped with may have a sport mode, but it's not suited to this kind of use. My shocks were all either on their last leg or completely dead, so I ordered some of the BC Racing DS Series coilovers. Their default rates are 6kg/mm front, 8kg/mm rear. 8kg/mm seemed much too soft for the rear though, as I had taken measurements of the rear control arms and found that the motion ratio was 0.578. With this, I found the rear spring should be at least 12kg/mm, and I decided I wanted to use a 14kg/mm spring.

The problem is, BC doesn't have options for the rear rate. The rear springs are not a conventional spring design. I ordered the coilovers from their site with the 12k rear spring and I was told they only had an 8k that would fit the car. So I went with that, and looked for a way to adapt a linear coilover spring to the rear. I discovered that the 350Z uses a rear spring of the same dimensions in BC's kits, but they also have an option to get the 350Z coilovers with a lower spring perch for linear coilover springs. These perches can be ordered separately (D-17-LSA), so I ordered them along with some 7" 14k Swift Springs. (As of August 2022 I have gone to a 14k front/28k rear setup)



They do in fact fit the car and seem to work perfectly. I haven't track tested the car yet with the new setup yet, and it still needs an alignment, but if I do ever need to change rates in the future I will now be able to use whatever rate I want for both front and rear.

Nice find on the rear adapter I

[P71Nero]

I did end up installing the thicker PP SHO radiator in the MKS. It was not a fun install but it seems to have made an improvement. There were also some rubber pieces that are supposed to help redirect air into the cooling stack that were missing. In the 60-70 degree temperatures at this time of the year the car is putting down power consistently and not showing signs of overheating. I was having issues with my Wilwood setup on the front so I had Carbotech cut some XP12 race pads for the stock caliper, but they didnt show up in time for a track day I did at the new Charleston Peak track at Spring Mountain in Pahrump, NV. I had some Porterfield R4-S street pads on there and they had severe fade and ended up completely disintegrating so I unfortunately don't have any good track footage yet.

[P71Nero]

Went to Willow Springs over the weekend and drove the Streets of Willow and Horse Thief Mile tracks there, here are my best laps. The one at Horse Thief Mile was the fastest of anyone there that day. Car is blowing a lot of people's minds. It would sure be nice to add downpipes, upgraded turbos, hpfp, e30, etc but there's no way the cooling system could keep up for 20-30 minute track sessions. Compared to the 6k/14k spring rates, 14k/28k and a degree more front camber saved me 2.6 seconds at Streets of Willow. By my standards, the ride is still quite comfortable to daily/go on road trips. My main goal with this car is to run a sub 2-minute lap at either Buttonwillow or Chuckwalla.

[SHOdded]

you could get extra cooling by plumbing the hvac system but i don't know if it would end up being a benefit or not.

have you removed the weatherstripping at the firewall for your track sessions? that is a quick trick to get/keep temps down since that is the area the heat tends to get concentrated.

[Thomks]

I absolutely love the track MKS! I just got my MKS recently, and I’m going for a similar build. Want to make an American M4. Those videos are awesome though!