BMR Performance vs. Handling Springs

[Norm Peterson]

Ok. You a-holes have me looking into ALL kinds of crap when all I wanted to do was lower my new car.

Let's just say that lowering can be done "thoughtfully" or "hastily and not so thoughtfully". Your long term satisfaction could depend on which approach you choose . . .


I'm personally a fan of plates over bolts even for just street driving, less "drop" over more, and somewhat higher spring rates over OE-ish rates (you need more spring rate to reduce nose dive and squat, the lowering alone hardly does anything for those). Linear-rate springs over progressives too, but that may not matter for your driving.


Norm

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[aleccolin]

So the BMR springs are both supposed to be a 1.2" drop, but the "performance" springs are 170 lb/in and the "handling" springs are 300 lb/in!? That's a crazy high rate.

Edit: Okay so their website says 300 lb/in but several places here say 250 lb/in - which is correct?

 

[Bluemustang]

So the BMR springs are both supposed to be a 1.2" drop, but the "performance" springs are 170 lb/in and the "handling" springs are 300 lb/in!? That's a crazy high rate.

Nah. The new handling spring is 0.88" drop and 250 lb. rate in the front. Also, don't compare the handling improvement between the performance springs and the handling springs. It's not going to be close. The performance springs will not appreciably improve handling and will probably make it worse, due to the larger front drop messing with the geometry and the rates near to the stock. The result is more body roll and twitchy steering. The performance springs are mainly for looks.

The new rates and drops of the handling springs are as follows:

0.88" front - 250 lb/in
0.75" rear - 980 lb/in

 

[aleccolin]

Okay so the info I had on the BMR springs is completely wrong then?

Long story short I've got FRPP Track dampers and Steeda adjustable height springs on the rear with a rate somewhere around 900-1000 lb/in.

The Steeda progressives I had on the front were causing a bouncy front end with the PP struts, Steeda Pro-Actions, and now with the FRPP Track struts.

I'm throwing a Steeda sway bar on to eliminate the glued-on bushings of the PP bar and hopefully some unwanted exponential springrate from that, but as far as front springs I have the option of (a) a new set of Steeda progressives of a revised design (supposed to be less drop) or (b) a set of BMR performance lowering springs (SP081) I've had for almost a year, or I could try the handling lowering springs (SP084) instead and maybe they'd let me do a return on the others.

This'll be round 4 pulling my suspension out, alignments are getting expensive.

 

[aleccolin]

FYI the other thing I'm considering is the extra 80-100 lbs on the front end when I do my blower install, plus probably 15 for the BMR brace I have already. Maybe the higher rate springs would be better after all so long as the struts can keep up.

 

[aleccolin]

The plot thickens - so I looked back and while I usually buy parts straight from BMR, the springs on my shelf were purchased from American Muscle in April 2019 and they're actually the handling springs.

The info on AM's site says 1.2" drop and 250 lb/in rate. Really not crazy about the lack of consistent information on these.

 

[BmacIL]

The plot thickens - so I looked back and while I usually buy parts straight from BMR, the springs on my shelf were purchased from American Muscle in April 2019 and they're actually the handling springs.

The info on AM's site says 1.2" drop and 250 lb/in rate. Really not crazy about the lack of consistent information on these.

What are the part numbers on the springs? Don't trust AM.

Front:
SP084A, SP084B - 300 lb rate, 1.2" drop
SP084C - 250 lb rate, 7/8" drop

Rear:
SP085A - 980 lb rate, 0.5" drop
SP085B - 980 lb rate, 0.75" drop

 

[Roadway 5.0]

Okay so the info I had on the BMR springs is completely wrong then?

Long story short I've got FRPP Track dampers and Steeda adjustable height springs on the rear with a rate somewhere around 900-1000 lb/in.

The Steeda progressives I had on the front were causing a bouncy front end with the PP struts, Steeda Pro-Actions, and now with the FRPP Track struts.

I'm throwing a Steeda sway bar on to eliminate the glued-on bushings of the PP bar and hopefully some unwanted exponential springrate from that, but as far as front springs I have the option of (a) a new set of Steeda progressives of a revised design (supposed to be less drop) or (b) a set of BMR performance lowering springs (SP081) I've had for almost a year, or I could try the handling lowering springs (SP084) instead and maybe they'd let me do a return on the others.

This'll be round 4 pulling my suspension out, alignments are getting expensive.

Be sure you cut the strut bumpstops down with the Steeda Progressives or any other lowering spring that drops the nose that much.

 

[aleccolin]

Be sure you cut the strut bumpstops down with the Steeda Progressives or any other lowering spring that drops the nose that much.

Yeah I did that, trimmed the OE bumpers per the instructions, then throughout the course of troubleshooting my issue trimmed another 1/2” off, then tried the Steeda poly bumpstops on the short height, then the shorter OE style bumpers that come with the track dampers. No change in behavior and no other indication it’s riding on the bump stops.

 

[aleccolin]

That's very helpful, thanks! I'll check as soon as I get home.

SP084RC

 

[BmacIL]

SP084RC

250 lb, 7/8" drop.

 

[aleccolin]

So I guess I'll roll with these. I wonder what the GT500 is using in the front? I know the GT350R is over 200 lb/in and the GT500 is going to be heavier esp on the front, pretty much the boat I'll be in when it's all said and done.

 

[BmacIL]

So I guess I'll roll with these. I wonder what the GT500 is using in the front? I know the GT350R is over 200 lb/in and the GT500 is going to be heavier esp on the front, pretty much the boat I'll be in when it's all said and done.

GT350R is 245, so it's probably similar.

 

[Norm Peterson]

"The GT500 also gets bigger sway bars and stiffer springs than the GT350, while opting for the Handling or Carbon Fiber Track packages brings adjustable top mounts, too."
https://www.roadandtrack.com/car-sh...ord-mustang-shelby-gt500-engineering-details/

I thought I saw a number starting with a '3' for the CF Track Pack front springs from some link, but I'll be damned if I can find either the data or the place where the link was again.


Norm

 

[Zelek]

I'll be rolling with the SP083 springs here on the B6's once everything comes in. Look forward to the results based on the feedback I've seen on this forum.

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