MCS SS+ and JCW

Which are they? I've heard both

 

the have a constant wind....

Matt

 

We've tested the SS and SS+ springs and know they're linear for a fact... Haven't tested the JCW springs, but they look linear to me...

 

JCW springs are linear - as Dr O notes, constant wind....

 

I thought so.
Thanks

 

With that answered...

Which are better for more sporting performance, progressive or linear? I was all gung ho for progressives till reading the Texas Speedwerks topic where the guy is touting the linear rates..

 

I haven't really heard any convincing arguments that the stock SS+ springs are BAD for performance. As Txwerks notes, they are linear for a reason, and they are pretty stiff. Now, if it's looks and ride height you're looking for, then they really are bad. But, as txwerks will also note, there is such thing as too low.

So that makes me really wonder about redskunk's question - what's better for the street and occasional track use, linear or progressive?

mb

 

There is no single perfect answer as some of the traits are subjective.

Having used both on the same car (actually stock '03 MCS SS+, SPAX RSX linear rate coilovers, and Bilstein PSS9 coilovers with a progressive front and linear rear) if you are looking for relatively sporty street use but you live in the Frost Belt and deal with potholes, cracked pavement, etc. then the progressive might be a good choice. The softer initial rate soaks up a bit more of the sharp bumps and once you are settled into a sweeper like an off ramp the stiffer rate feels pretty good.

What you give up is some of the responsive transient behavior that makes the MINI so fun on really twisty roads. You might also notice the difference during track use, or especially autocrossing. In those cases I think linear rate springs are the way to go, as they give quicker response to steering input and are a little more predictable at the limit.

Of course road quality, spring rate, sway bar sizes, tire sidewall height and construction, and driver preferences all act to complicate the equation.

For what it is worth, I'm planning on putting linear rate springs on the front PSS9s this winter as I really don't like the progressive springs FOR MY USE.

I haven't tried the TXwerks myself, but given their spring rate is in between SS+ and the SPAX that I have used I suspect that they'll work really well for street use and occasional trackday/autocross folks. Making them stiffer to better suit serious autocrossers and track day junkies would start to hurt the ride quaility on anything but smooth streets.


Scott
90SM

 

Matt

 

In our experience, linear rates are just more predictable at the limit... They don't change as they load, and in quick transitions, there are no surprises as the suspension unloads and loads again on the opposite side. Call it more planted, if you will...

 

I liked the improved ride of H-SPorts on the street, but didn't like them on the track. My coil overs have linear, and it's MUCH more predictable for me, but that may just be my skill level, or maybe all the stuff posted previously!

Matt

 

Very helpful posts, thanks!

mb

 

Great explanation

Like Dr Obxns, I currently have the H-sports. While ride quality is fine, I was disappointed to lose that responsiveness the eom springs had. Having increased my track time, I am now considering installing KW V2s. My question being, will the V2s with progressive fronts and linear rear (or any other coilover kit with a similar configuration) bring back the responsiveness of oem linear rate springs?


Dr Obnxs - what coilovers are you running?

 

with linear springs. But I bought them used, and the spring rates are all wrong. But when I change them, I'll be sticking with linear.

Matt

 

One of the reasons, I suspect, the Mini handles so well despite possing a layout similar to other front wheel drive cars is that BMW devoted a lot of time to controlling weight transfer and subtle wheel movement. Roll center migration and the swing arm affect have a lot to do with how a car grips and transitions thru turns. I think progressive rate springs feel very good while driving down the highway, but dilute the harmonies designed into the Mini's suspension by allowing 'odd' or 'extraneous' movements to occur.

As was noted by STX90 above, there isn't one perfect setup, because every choice determines the next set of choices. I personally believe a perfect track/road spring rate combo to be 315# springs up front and 300# springs in the rear - this assumes the use of 10mm wider stance up front, hence the slightly heavier rate to make up for lost motion ratio - about 10% or 285# spring with no increase in track. A pure track setup will be different. However, I also don't think the Mini requires huge spring rates because the suspension geometrys have been so well designed. Toe changes with travel are basically non-existent up front and although camber does move from slightly neg to positive in stock fashion, there is a fairly large usable amount of travle before pos. camber is reached. Add a camber kit and problem solved...but this changes roll center locations and SAI - see it gets complicated.

My current Megan set up uses 469# springs up front and 335# springs in the rear - way too much spring up front for this car on the street...and the balance is poor.

By the way, I may be purchasing a suspension program this winter; I've been thinking about this for a while and Dr. Obnxs also suggested I look into one of these. I've also solicicted some outside suspension theory assistance - from Maranello. This sort of ties into something I wrote about about motion ratios and spring rates. When the Mini's track is increased up front, spring and damping rates become less affective because the control arm's leverage has increased. So, larger rates are needed. I also assumed the same for the rear...until my friend pointed out that Mini's rear control arm pivot point is virtual and quite far outside the other side of the car. So track changes in the rear do not affect motion ratio in the rear. But increasing rear track will decrease 'camber stiffness' because the virtual swing arm is longer. The swing arm pivots off the instantaneous center. If this swing arm is longer, camber change at the rear will be less as the suspension moves. I assume some camber gain in the rear is vital to stable handling with the Mini - as in most cars. God I love this stuff!!!

 

but remeber, since the rear arm pivot point in on the opposite side of the car by a long shot, spacers won't really effect the camber gain or anything else that much, because while the virtual swing arm is longer, in percentage terms it's not much of a change..... Also, for the camber stuff, the gain is actually independant of the spacer thickness. Now scrub distances get changed, but camber gain doesn't. That much that is.... To change camber gain, one would need an eccentric rear control arm mount....... Hmmmmmm.

Matt

 

I used an eccentric in my 1981 Ford Fiesta's LCA. Worked great!

The camber changes are small for sure, but interesting to get a feel for the dynamics at work; and since the wheel offset change also affects RC migration, it has some affect on weight transfer as well as the location of center of gravity.

What I'm missing as a novice are the actual force values these changes represent. The exact camber change may be meaningless with regard to the mini, but may be huge if we were tuning an F1 rig. But even a 5mm spacer has a noticable affect on the Mini's handling up front or in the rear. A 15mm up front and a 10mm in the rear feel very nice!

 

Meb / others – the Nex coilovers have spring rates of 336lbs front and 224lbs rear according to one source. Whatcha think of this rate combo, esp. with other standard entry-level suspension (rear sway, camber plates)? Besides a harsh ride, what other drawbacks are there from going too stiff?

 

The quality of public roads ia a big factor. Comfort is one obvious reason to avoid big rates.

Big spring and damping rates don't always allow the suspension to, well, suspend! Weight transfer is a key part of good handling and we simply don't, or shouldn't, drive at the speeds we do on the track. So, less damping is required. Also, big spring rates will cause a car to pitch and yaw over subtle road irregularities while traveling in a stright line. This unecessary movement can sometimes upset a car, make it feel nervous. On the other hand, soft rates on a track will make the car feel sluggish.

Lime Rock is considered a bumpy track, but it in no way does it compare to my commute; Lime rock feels glass smooth against the roads I commute on.

Regarding Nex coilovers...The front rates are borderline stiff, but if you run 38mm offset wheels or less these will feel more comfortable. The rear rates are a nice in terms of comfort; the backend will not bob up and down over a series of undulations perpendicular with the road. I don't like the balance, though. Somewhere around 300#s front and rear is not a bad place to be for road and track. All road, go lower...all track go higher...FWIW

 

Lime Rock is only considered "bumpy" LOL

I was watching the Miata Cup race this weekend and I couldn't believe how bad that track was. I have seen uncountable races there before, but never saw that kind of action before.

OK back to our regular programming and geek talk...........

This has been a very informative thread. Thank you gentleman.

 

I now have another data point. Waylen and I installed a set of Hypercoil 2.5"diameter 350lbs/in linear rate springs on my front PSS9s. I was expecting some decline in ride comfort but willing to trade that off in order to get better transient response for autocrossing.

The ride height went up (intentional for winter, though further than I'd originally planned) and the alignment was set very close to the prior settings (same toe, but a touch less camber in front (2.0 vs 2.3)).

I haven't really driven too aggressively, since our autocross season ended a couple weeks ago and I'm snow tires now anyway. Still, the response to steering input is better so that worked as expected.

What I wasn't expecting was for the ride to improve. I can feel a little more going over rough seams and the like since the progressive fronts did soak those up a little better as intended. But the choppy, bouncy effect just driving down the highway is mostly gone. It now feels much more like the SPAX and stock in this respect. I suspect this is a result of the front and rear rates being better matched. Whatever the cause, I'm happy as my wife won't be complaining when she has to drive the Mini occasionally plus the ride back and forth to work will be more pleasant.

I orignally set the dampers with the new springs at 8F/8R but found 7F/8R felt better. My "best" street settings with the original Bilstein springs was 6F/8R.

Now if I had just gotten slightly shorter springs up front I'd be a truely happy camper.

Scott
90SM

 

the less I understand the firmer rear spring. The car is 60.9 / 39.1 front bias for weight. The rear springs travel pretty much 1 to 1 with the wheel, the front less than this (though just how much I don't know). These two items would leave me to believe the right spring combo would be more than 1.5x stiffer in the front! So, firmer front springs, softer in the rear, softer front bar, and real big rear bar. Then the spring constants are right for the weight distrubutiong and motion ratios, and the weight transfer in turns is managed by bar diameter.

But to be honest, that's a phycisists perspective, not a suspension gurus!

Matt

 

We've tested a lot of spring setups... Just our $.02, but square rates and linear springs work best to go fastest (square meaning the same rate front and rear). We've tested a lot of offsets and messed with a lot of valving... Also, I'd rather get almost all the way there with the spring rates and then fine tune with swaybar and the adjustable coilovers.

I'm running 2x the OEM spring rate on the street everyday, and it rides better than it did stock...

 

What springs would those be?

 

And that's exactly how a car should be set up!

Regarding Doc's note about heavier rear rates; There will be a perfect rate for the front for every driving venue, I suspect. But what the ideal rate is for the track or road is sort of a guess without a proper suspension program, shock dyno and lots of seat time. Heavier rear spring rates are, to me, more predictable than a heavier rear bar as bars wind-up exponentially...and at it's limit, lifts the inside rear wheel off the ground. But, a heavier rear spring is also a compromise to ride, and in some instances handling if the road is really bumpy. And, every car has a different wheel base and tire compliance and bushing compliance and these all factor into how much rear spring a nose heavy car needs to assist rotation.

Complicating bar and spring rates is damping characterisitics. Damping values or force is one thing, but the force/velocity curve is another thing altogether. Two dampers may share the same damping force while their force curves make each feel like completely different animals...and hence, why some dampers work better with some spring rates...as STX90 may have experienced.