Bilstein B8+RCE Yellows vs Tien Flex A's

[itschris]

Originally Posted by ZDan

I think B14/B16 springs are progressive and start out with much softer rates than Spec R. Main reason I went with Swift Spec R/B8. Also no height adjustability saves me 42 lb. for car classification for time trials!
https://www.ftspeed.com/part/47-2283...a#.X73BQMhKhPY
https://www.ftspeed.com/part/48-2282...t#.X73B9MhKhPY
Front: 2.5-4.5kg progressive
Rear: 3.0-7.0kg progressive

Yes, they start very soft but that's at full droop. With the car's weight, the effective rate is stiffer. Here is a spring dyno by Vorshlag. Take the sprung weights at each corner, and then calculate the corresponding displacement and rate at that displacement. You should get pretty close to the 4.2f/5.5r I quoted. Quoting the 2.5/3.0 rates is a bit like quoting helper rates on other coilovers.

[asdf]

not exactly what you’re asking, OP but my personal experience on this car was:

trd springs + blistein b6 -> bilstein b14 -> ohlins r&t

and i honestly felt like each progression made the car feel better all around. from cruising around town, to canyon runs, to autocross.

[jflogerzi]

Next season I will get new coils and try and get some ride alongs at the track. Was not ready to drop that much coin on coils and I really want to skip the ground so hence just getting a new damper+peddler top hats

Sent from my GM1915 using Tapatalk

[Racecomp Engineering]

PP shocks are fairly firm on compression damping, meaning they work well on softer (stock) springs and with stiffer lowering springs they do perform really well but you do feel some more harshness.

17+ non-PP shocks are the most comfortable of the OEM shocks.

Previous OEM shocks have a lot of rebound (and also plenty of compression) which affects the ride.

Plenty of rebound headroom on all of the above for a stiffer than stock spring, but obviously that's not the only thing to think about!

Coilovers can definitely perform and ride better if done right. More money than just springs. And of course the wheel size issue.

The valving on Bilstein B6 and their B14/16 coilovers is just far superior to OEM. It's not about the spring rate they can support, it's the overall design of the valving. They're very good.

If adding up springs + camber plates + Bilsteins, it's definitely worth thinking about a coilover, especially if you're hitting the track (and rules allow). But it's still very good.

Different strokes, budgets, rules, and priorities for different folks. Bilstein + good springs is easy and simple and very good. Good quality coilovers can be awesome especially on track with a little more set up and usually more cost. Using just good springs on OEM shocks might be the way to go if you only have ~350 bucks to spend and want to improve performance.

- Andrew

[ZDan]

Originally Posted by itschris

Yes, they start very soft but that's at full droop. With the car's weight, the effective rate is stiffer. Here is a spring dyno by Vorshlag. Take the sprung weights at each corner, and then calculate the corresponding displacement and rate at that displacement. You should get pretty close to the 4.2f/5.5r I quoted. Quoting the 2.5/3.0 rates is a bit like quoting helper rates on other coilovers.

Great info! Yeah, looks exactly like the soft initial rate is just a built-in "helper". I had some bad info on these, someone reported negatively on the "soft initial rate"!
My math says there's ~825 lb. on front springs and ~855 lb. on the rears (2850 lb. car+driver, 55F/45R, 0.95 front 0.75 rear motion ratios). That's out of the range measured for the fronts, going by the last half inch of travel measured I get 232 lb/in or 4.14 kg/mm, close enough to 4.2! For rears in the range of static load I get 404 lb/in or 7.3 kg/mm.

Anyway, glad to confirm the *actual* real-world stiffness for these! Still glad I went with the Swift RSpec, these rates seem very rear-stiffness biased...

[itschris]

Originally Posted by ZDan

Great info! Yeah, looks exactly like the sof initial rate is just a built-in "helper". I had some bad info on these, someone reported negatively on the "soft initial rate"!
My math says there's ~825 lb. on front springs and ~855 lb. on the rears (2850 lb. car+driver, 55F/45R, 0.95 front 0.75 rear motion ratios). That's out of the range measured for the fronts, going by the last half inch of travel measured I get 232 lb/in or 4.14 kg/mm, close enough to 4.2! For rears in the range of static load I get 404 lb/in or 7.3 kg/mm.

Anyway, glad to confirm the *actual* real-world stiffness for these! Still glad I went with the Swift RSpec, these rates seem very rear-stiffness biased...

Ahhh good catch with the motion ratios! I think when I measured the springs myself I got a slightly higher rate in the front than Vorshlag, so I managed to get the same answer there with the wrong methodology.

Don't those weights include unsprung mass? I had used ~685 lbs front/~560 lbs rear for just the sprung mass. Corresponding force on the springs would be (685/.95) and (560/.75) or ~720 lbs and ~745 lbs, leading to ~4.1-4.2 kg/mm front and ~6.4 kg/mm rear. About halfway between our two numbers

[ZDan]

Originally Posted by itschris

Ahhh good catch with the motion ratios! I think when I measured the springs myself I got a slightly higher rate in the front than Vorshlag, so I managed to get the same answer there with the wrong methodology.

Don't those weights include unsprung mass? I had used ~685 lbs front/~560 lbs rear for just the sprung mass. Corresponding force on the springs would be (685/.95) and (560/.75) or ~720 lbs and ~745 lbs, leading to ~4.1-4.2 kg/mm front and ~6.4 kg/mm rear. About halfway between our two numbers

Oh yeah, good catch yerself!

I def would have given these more consideration if I'd had a better idea what the *real* spring rates are. But I saves 42 lb. with no ride-height adjustability, and not gonna lie, I like the idea of competing against "serious" coilover setups with "just lowering springs and struts/shocks" :P