Springs rates too stiff?

[TeeLew]

The SP763 package is the minimum drop front springs matched with the same rear springs as the SP080 performance set, which have a 1/2 inch drop and 740 spring rate.

OK,OK, I put a note in the sheet, but I can't change it. Stop yelling...

Sponsored

 

[StangTime]

OK,OK, I put a note in the sheet, but I can't change it. Stop yelling...

It won't get updated unless someone else takes the sheet and reposts it as their own. The original creator hasn't been on the forum in years. I would question or cross check any info on the spreadsheet as it hasn't been kept up to date.

 

[TeeLew]

Bummer...

 

[WD Pro]

I started my own sheet (biased to finding out how the FP MR kit fits in with Fords other offerings).

I don’t know what was on the original, but I’m happy to share where I am up to with mine (when I’m back on my work PC)

WD

 

[MidwayJ]

OK,OK, I put a note in the sheet, but I can't change it. Stop yelling...

Just trying to provide clarifying information.

 

[S550 Recon]

Did I read the OP correctly, that you are saying 170F/740R springs are too stiff for you?

 

[v8hgt]

Yeah. I’m happy with the front, but I’ve come to the conclusion that on roads where I live, the rear springs at 740 lb/in are too stiff when paired with the PP dampers which are a bit underdamped especially in rebound. I’m going to try Bilstein b6 dampers matched with stock PP springs with a little cut off the ends to drop by 0.5 inches.

 

[S550 Recon]

Def not a bad plan. I think it was mentioned above, the non PP GT rates are in the 660lb/in range so that might be a good idea.

Do keep in mind that because of the motion ratio, that sort of change is not actually noticed much. Its been a long time since I did the math for comparing, but I think it was around 15lb/in wheel rate increase when going from a GT spring to the BMR 740 spring. FYI. Definitely an increase in wheel rate, but.....not much.

 

[shogun32]

Adding stronger mounts has been known to tear them clean out of the shell. Go too stiff on the compression damping and you may risk structural damage

there is no shim stack on the planet that can be so strong as to match the crash impact forces that bottoming out the shock produces - which tears the sheet metal apart.

I'm still working out what I like. I did the Steeda progressive springs and pro-Active. too much drop and not a good-enough damper. On straight-rate springs of modest rate <200/800 they might suffice.

The Steeda DR springs and pro-Action adj. are really quote decent except the front is busier than I like. I also would prefer the rear 800/1200 transition to be deeper into the stoke. Watching IMSA and Supercars on TV last night I cringed every time the front end got thrown up in the air going over bumps. Their front spring rates are so high (or travel so short) that the whole car moves wildly instead of gliding undisturbed over disruptions. But then again they have their reasons for their choices (aero-support) and brake dive.

Right now I'm running 275 (but have 325 and 400 on the shelf) on Fortune Auto 510 dampers up front and the Pro-Action+DR on the rear. Tim has brow-beat me into trying a straight-rate 800'ish rear spring or digging up my PP1 rears which I still have I think. I'm going to give the 'soft ass' thing a try.

I will say my still-stock EB base is f'n SCARY in how much it pitches and dives compared to my GT and how tenuous it's lease on grip seems in corners. Though skinny, tall sidewall factory tires also play a role. Whatever the solution, the Mustang definitely needs help in roll support.

I think the reason nobody with M1 is bitching about the soft rear spring rates is partly because they are still in love/infatuation. While it's probably 'righter' than going 800+, it's also because you can do things with Magneride that is not possible with traditional valving. When your dampers suck-ass the solution most reach for is more spring so that the damping weakness isn't so obvious. This is very common in the cut-rate coil-over solutions.

 

[TeeLew]

Just trying to provide clarifying information.

I was just playing.

 

[TeeLew]

there is no shim stack on the planet that can be so strong as to match the crash impact forces that bottoming out the shock produces - which tears the sheet metal apart.

I'm still working out what I like. I did the Steeda progressive springs and pro-Active. too much drop and not a good-enough damper. On straight-rate springs of modest rate <200/800 they might suffice.

The Steeda DR springs and pro-Action adj. are really quote decent except the front is busier than I like. I also would prefer the rear 800/1200 transition to be deeper into the stoke. Watching IMSA and Supercars on TV last night I cringed every time the front end got thrown up in the air going over bumps. Their front spring rates are so high (or travel so short) that the whole car moves wildly instead of gliding undisturbed over disruptions. But then again they have their reasons for their choices (aero-support) and brake dive.

Right now I'm running 275 (but have 325 and 400 on the shelf) on Fortune Auto 510 dampers up front and the Pro-Action+DR on the rear. Tim has brow-beat me into trying a straight-rate 800'ish rear spring or digging up my PP1 rears which I still have I think. I'm going to give the 'soft ass' thing a try.

I will say my still-stock EB base is f'n SCARY in how much it pitches and dives compared to my GT and how tenuous it's lease on grip seems in corners. Though skinny, tall sidewall factory tires also play a role. Whatever the solution, the Mustang definitely needs help in roll support.

I think the reason nobody with M1 is bitching about the soft rear spring rates is partly because they are still in love/infatuation. While it's probably 'righter' than going 800+, it's also because you can do things with Magneride that is not possible with traditional valving. When your dampers suck-ass the solution most reach for is more spring so that the damping weakness isn't so obvious. This is very common in the cut-rate coil-over solutions.

1. Bottoming forces are a way bigger deal than compression damping. At most, your damper might put a few hundred pounds of force into the chassis. Bottoming can be thousands in a big impulse load.

2. Be careful watching aero cars, because there will always be an aero/mechanical compromise. The Pilot Challenge GT4/TCR cars are really more representative of what our cars should look like on track. Check out the Sebring GT4 race on the IMSA site to see what purely mechanical cars look like on a rough track.

3. Brow beat! Ya, kicking and screaming the entire way, lol!

4. It's funny that there is so much difference between base and performance of the same model. You knew it was that going in, but I think the magnitude of difference is bigger than either of us suspected.

5. Very, very true. Let's face it, damping is tough to get right and springs are easy to change.

 

[shogun32]

Who updates the spreadsheet? We should put this in.

I maintain my copy here.
https://www.dropbox.com/s/yytkee6jlsmvofj/S550 Mustang Springs.xlsx?dl=0

I cribbed BMac's sheet when it was still public, put formulas in where he had hard-coded frequency calculations, and filled in a bunch of stuff he didn't have.

If for some reason you can't download the file, let me know.

 

[GreenS550]

Interesting reading. I sold my M1 last summer because of things beyond my control. But I have done suspension stuff on other S550s as well as having owned a Bullitt with Magneride, but the Bullitt was just PP1 with mag ride.
I have since ordered another M1 in auto. So, I can say, to me, the M1 was by far the best riding, quiet (NVH) S550 I have ever owned, and I've owned 6. Whatever Ford did with the M1 is very, very good. I don't know all the parts, but sucks up bumps very well, handles very well, and quiet.

 

[StangTime]

I maintain my copy here.
https://www.dropbox.com/s/yytkee6jlsmvofj/S550 Mustang Springs.xlsx?dl=0

I cribbed BMac's sheet when it was still public, put formulas in where he had hard-coded frequency calculations, and filled in a bunch of stuff he didn't have.

I thought Steeda Min drop was 200/800 spring rate now? Ref: https://www.mustang6g.com/forums/th...drop-s550-lowering-springs.90203/post-1995692

@shogun32 can you change the value from 750 to 800 for the Steeda min drop springs please?

 

[Hack]

I’ve been thinking lots recently about my suspension and I’ve come to the conclusion my rear spring rates are too stiff and the dampers too lose. The fronts are slightly too stiff too but no where near as bad. I’m running BMR min drop springs front and BMR sp080 rears on PP dampers which give rates very similar to a gt350. They are fine on smooth roads but not great on typical U.K. roads. I would really like to try some softer lowering springs with adjustable dampers to see if that sorts the problem. Lotus always used soft springs and firm dampers. I think Ford are using stiff springs and soggy dampers…

anyone tried this approach on a road driven mustang? I know the top rear shock mounts are weak on mustangs. Would firm dampers and soft springs rip them right off?

What are your goals? Good handling, soft ride, appearance?

PP suspension is extremely soft, so the dampers are going to match. I would recommend buying shocks to go with whatever springs you select. If your goal is a lower ride height, realize that stiffer springs should be selected to prevent the suspension from bottoming out.

The main thing I disliked about how my GT350 rode on rough surfaces was the tramlining. I think going to narrower tires can help with that if you aren't looking for the best cornering performance but rather for a more comfortable ride.

Sponsored