Poll: Linear vs. Progressive Spring Rate

[Cardude99]

Theoretically it can control either quite well, and it depends on what you most want for the car.

Thanks man for the reply, I like having a good balance of street and performance. Might lean 60/40 toward the performance end of the spectrum.

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[Bluemustang]

My theory - Ford puts the dual rate on the rear for the GT350/R to try to help balance the handling you'd expect out of the GT350 while still maintaining ride quality suitable to their targets. The rear suspension seems to be the most penalized in terms of ride. In this way, they can still get the max rear spring rate they want to achieve while still making it compliant enough.

I've gone from BMR SP080 (linear, stock PPish rate) to Ford Racing "track" Y springs (dual rate, rates similar to GT350 cars) to BMR SP083 handling springs (linear, GT350R"+" rates). The latter has been the best. And each time I've gone UP in the spring rate not DOWN. And it's a daily driver. But the Ford Racing track is a very good kit. It cornered very well.

 

[Roadway 5.0]

I chose linear because it’s what I know works.

There is, however, a huge temptation to venture into the unknown and try Steeda progressives with bigger bars.

 

[Norm Peterson]

Cardude99 said: ↑
To add on, how about for a magneride car, sport vs dual rate, what would be the better choice. I have been wondering about this topic for the last few weeks.

Theoretically it can control either quite well, and it depends on what you most want for the car.

Agreed.

If anything, MR ought to be better suited to controlling progressive or dual-rate springs than conventional dampers.


Norm

 

[Coyote Red]

I wanted to lower my pony,but not too much as I dd the car for work. In the twisty's I tend to be very aggressive so I went with "progressive" SVE was my choice, 1.5" front drop, 1 1/4" rear, on oem springs now w/BMR caster/camber bolts. Alignment is
-1.1 camber front, -1.6 rear. Still on oem dampers after 12,0000 miles. FRPP track dampers are next. I like the turn in I have presently and if the new dampers improve the "feel" and control, I'll be grinning!

 

[bootlegger]

Went with DR, as the car will be more for street than track. I am very happy with the choice so far. Feels close to stock until you push it.

 

[morgande]

Went with DR, as the car will be more for street than track. I am very happy with the choice so far. Feels close to stock until you push it.

I assume they are the Steeda competition Dual Rate springs?

 

[bootlegger]

I assume they are the Steeda competition Dual Rate springs?

Correct.

 

[NightmareMoon]

Anyone notice how there are no linear lowering springs with rates as high as the Steeda Ultimate DR rates or higher? Its cause such a spring can't exist with the required travel for our cars using the stock perches.

If the spring rate is high enough and the drop big enough, you need a second softer helper spring to give you the suspension droop travel without the spring coming loose between the perch and top hat.

That's where Dual rates come into play (or main spring + helper spring for coilovers). Dual rates act more like linear lowering springs as compared to true progressive springs. The softer spring rate at the top is there just to give you that full travel range.

So the debate between linear and progressive should remain that. Don't try to throw DRs in the mix. Linears and progressives are only interesting to compare in the range of spring rates and drops where they both can operate.

 

[BmacIL]

Anyone notice how there are no linear lowering springs with rates as high as the Steeda Ultimate DR rates or higher? Its cause such a spring can't exist with the required travel for our cars using the stock perches.

If the spring rate is high enough and the drop big enough, you need a second softer helper spring to give you the suspension droop travel without the spring coming loose between the perch and top hat.

That's where Dual rates come into play (or main spring + helper spring for coilovers). Dual rates act more like linear lowering springs as compared to true progressive springs. The softer spring rate at the top is there just to give you that full travel range.

So the debate between linear and progressive should remain that. Don't try to throw DRs in the mix. Linears and progressives are only interesting to compare in the range of spring rates and drops where they both can operate.

Excellent points here.

 

[Norm Peterson]

Exactly where along the bump/rebound travel a dual-rate spring switches rate probably matters, and it would make sense to choose that point when looking for a specific end result. I would not assume that all spring mfrs/aftermatket suppliers are going to select the exact same point.


Norm

 

[Bluemustang]

Good points @NightmareMoon - and I should also point out for those who don't know:

- There are true progressive rate springs that continuously increase in rate as the spring is compressed AND
- Dual-Rate springs which feature two separate regions with different rates. A lower rate and then a transition into the higher rate. And like you said, sometimes the lower rate region just serves as a helper spring and isn't really contributing at all at ride height

 

[BmacIL]

Exactly where along the bump/rebound travel a dual-rate spring switches rate probably matters, and it would make sense to choose that point when looking for a specific end result. I would not assume that all spring mfrs/aftermatket suppliers are going to select the exact same point.


Norm

Exactly. For instance the Steeda DR have about 1/4-3/8" of travel in the lower rate from ride height before transitioning into the higher rate. Others, like many coilover offerings, have helper springs that are fully compressed at ride height.

 

[Bluemustang]

Exactly. For instance the Steeda DR have about 1/4-3/8" of travel in the lower rate from ride height before transitioning into the higher rate. Others, like many coilover offerings, have helper springs that are fully compressed at ride height.

So if true they do act as dual-rate springs and not linear rate.

 

[Norm Peterson]

So they do in fact act as dual-rate springs and not linear rate.

Depending on what suspension height the rate transition occurs at (and how hard the car is being driven), they can.

If the transition is right at static ride height, you'll be constantly going back and forth between the firm and soft rates.

If the spring transition occurs at a ride height higher than static, you may not encounter the transition very often, or hardly ever if it's high enough into rebound. You'll be in the firm rate until that corner rises up far enough. So how far up the transition is will affect how much of the time is spent at the 'firm' rate and how much at the 'soft rate'.

Going the other way, if the transition needs the suspension to have moved a noticeable amount into 'bump', you'll be in the soft rate region at static ride height and for more than half of every suspension cycle. The further down into bump the transition to 'firm' is, the more of your driving will be in the soft rate.

Will you feel the transition when it happens? Maybe, though it may not be as obvious as the change in stiffness numbers might lead you to expect. As a practical matter, it's probably not a true 'step change' between firm and soft . . . more like a very rapid progression that's over and done with in a fraction of an inch or so.


Norm

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