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Best street suspension setup

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Hi all. Long time lurker here, but first time poster. With the track day/time trial season looking like it will be shortened because of COVID, my car is only going to be seeing street driving for the foreseeable future. Instead of springing for a new set of coil overs for the track, I think the $$$ would be better off spent on a nice set of shocks & struts for the street. My car is a 2012 GT with Steeda shocks & struts that have 30k+ miles on them, and don't exactly provide the best ride possible. I'm looking at Koni, Bilstein B6, or Ford Performance right now and was wondering what others would suggest. Some specs for reference:

Tires: Michelin PS4 275/40R19 all around
Springs: I have both BMR lowering springs for the street (165 lb/in front, 160 lb/in rear) or SR lowering springs (225 lb/in front, 200 lb/in rear) that I use for the track
Bump stops: Ford Performance kit
Front mods: GT500 strut mounts
Rear mods: full BMR kit (re-location brackets, trailing links (poly/rod end), 3rd link (poly), adj PH bar with rod ends)

I realize my rear end setup isn't helping me for street comfort, but it's not really the gear whine that bothers me as much as the bouncing over the pothole'd New England roads. I'd think that the softer BMR springs would give a better ride than the SR's, but since they are shorter they engage the bump stops earlier which probably makes them act stiffer overall. I don't generally want to cut bump stops since the Ford engineers are smarter than me when it comes to designing these things, but I think it could help make that initial bit of travel over smaller bumps a bit softer. I'll have to be very careful to ensure I cut both sides about the same (+/- .1 in) to ensure consistent engagement. A lot of this is thinking aloud, but I would like to get some input before breaking out the cutoff wheel and blindly charging the credit card.
 

Norm Peterson

Corner Barstool Sitter
939
712
Exp. Type
HPDE
Exp. Level
5-10 Years
a few miles east of Philly
Hi all. Long time lurker here, but first time poster. With the track day/time trial season looking like it will be shortened because of COVID, my car is only going to be seeing street driving for the foreseeable future. Instead of springing for a new set of coil overs for the track, I think the $$$ would be better off spent on a nice set of shocks & struts for the street. My car is a 2012 GT with Steeda shocks & struts that have 30k+ miles on them, and don't exactly provide the best ride possible. I'm looking at Koni, Bilstein B6, or Ford Performance right now and was wondering what others would suggest. Some specs for reference:

Tires: Michelin PS4 275/40R19 all around
Springs: I have both BMR lowering springs for the street (165 lb/in front, 160 lb/in rear) or SR lowering springs (225 lb/in front, 200 lb/in rear) that I use for the track
Bump stops: Ford Performance kit
Front mods: GT500 strut mounts
Rear mods: full BMR kit (re-location brackets, trailing links (poly/rod end), 3rd link (poly), adj PH bar with rod ends)

I realize my rear end setup isn't helping me for street comfort, but it's not really the gear whine that bothers me as much as the bouncing over the pothole'd New England roads. I'd think that the softer BMR springs would give a better ride than the SR's, but since they are shorter they engage the bump stops earlier which probably makes them act stiffer overall. I don't generally want to cut bump stops since the Ford engineers are smarter than me when it comes to designing these things, but I think it could help make that initial bit of travel over smaller bumps a bit softer. I'll have to be very careful to ensure I cut both sides about the same (+/- .1 in) to ensure consistent engagement. A lot of this is thinking aloud, but I would like to get some input before breaking out the cutoff wheel and blindly charging the credit card.
Koni yellows have a big advantage as far as dual-purpose cars are concerned. You can dial them up for the track and back down for the street. Even establish settings softer than your own normal street preference for travel over really bad stuff or where passengers with different ride quality preferences are aboard. Ride quality-wise, dampers are where harshness (too much damping) or floatiness (not enough) mainly comes from.

I'll try to make a case for BMR's GT500 Handling Springs. They're slightly stiffer than those SR's at 260/220, but they only drop the front by around half an inch and the rear by a little over an inch. The rear can be shimmed up to better match the front. I've done that (strictly as a DIY effort), and I did trim the OE bump stops back slightly, not as far as the amount you're most likely to read about people doing/suggesting. Partly because I wasn't the lighter GT doesn't drop as far as the heavier GT500, and partly because I wasn't taking the rear of my car down the full amount of GT500-spring drop in the back anyway.

I did add a ring inside the rubber isolator and some other details to make sure that the springs stayed centered. It's not supposed to be a show car.

IMG_0678 web.JPG


Bumpstop mod pic 1.jpg

There's no hurry, but you might want to consider Steeda's HD strut mounts for the camber adjustability that they provide. There are a couple of O-rings in each that may deteriorate over time, but these can be refreshed with O-rings sourced from any of the big-box hardware/home improvement stores.

Polyurethane bushings as supplied are not generally the hot tip for a corner-carving rear suspension, especially in any of the three trailing links. But if you have any poly in there already there are a few things you can do on a DIY level to improve them for cornering (and as a side effect, you might end up eliminating nearly all of the squeaking that poly is infamous for). Possible downside - shorter service life, but polyurethane bushings should properly be considered 'wear parts' anyway. Here's one sketch that shows enough of a poly mod for the LCAs; I may be able to find another one showing further "DIY mods to further soften poly bind" somewhere. Think "voided bushings".

Poly Bushing Mod.jpg

FWIW, with the 260/220 springs, Koni yellows, lightly modified poly/spherical rear LCAs, and 285/35-18 MPSS tires on 11" wide wheels, my 70 y/o (shhhhh!) wife doesn't complain about riding in my '08. As long as I dial the Konis back closer to full soft for longer rides.


Norm
 
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Thanks for the suggestions. Unfortunately it seems the OEM BOSS 302 shocks/struts are NOT cheap (~$1350 on RockAuto for all 4), though it'd likely be a good option. Koni yellows are very tempting, but my Autocross buddies are trying to push me into the Bilsteins which are a little cheaper. My only experience with either is Bilsteins on a circle track car and they were great. I'll need to mull it over before spending that kind of $$$.

Those bump stop cuts looks like just what I was thinking, so I'll be getting out the cutoff wheel to shorten mine some. The spacers are a good solution for the rear. I'm not sure there's a non-hack way to raise the front to match with the BMR springs I have, so maybe the GT500 springs are the solution.
 

Norm Peterson

Corner Barstool Sitter
939
712
Exp. Type
HPDE
Exp. Level
5-10 Years
a few miles east of Philly
I probably ground the tips of the bump stops down on the bench grinder. I also plugged the hole in the center of the bushing with a vacuum cap and some glass sealer.

Bumpstop mod pic 2.jpg

I can think of a way to shim the fronts up, but it would involve more work than swapping the springs. Kind of a "technique of last resort".


Norm
 
UPDATE:

Upgraded to the Bilstein B6 set from a 2009 GT500 as I use the early S197 GT500 strut mounts. I strongly considered the Koni's but the extra cost made me go with the Bilstein. Turns out the Steeda's I had on the front were totally blown out.

I also cut the rear bumps and stuck with the SR springs (225/200) for now. It rides MUCH better! Still not quite as good as my dad's ZL1 with magnaride, but a huge improvement over what it was. Hopefully I'll be able to try it out on track once the state governments here in New England decide to allow racetracks to operate, even if it's just smaller events.
 

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