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      01-27-2015, 11:52 AM   #1
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Track spring rates

Doing a lot of research before my track build starts. I need some input on spring rates. My car would be track only, so I'm thinking 700-800 front and 900-1000 rear for spring rates. It will be lighter too, think mildly stripped interior (all carpets, seats). Anybody run 700-800 front, 900-1000 rear?

Still deciding on shocks, I want a single adjustable setup. I've been on revalved Ohlins R&T for high rates, and they are fantastic. Also had them on my GT3RS, and they are were great (they came with more track focused rates for that kit). Most people discount this setup because of low spring rates, but just have somebody like PSI revalve them for high rates and you have a great track setup, with long rebuild intervals.

Nitrons are supposed to be great, but rebuild intervals are supposedly much shorter.

JRZ and MCS are also options. Tough to decide. Input is appreciated.
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      01-27-2015, 12:02 PM   #2
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Your analysis is actually backwards. First you have to decide on dampers and only then you can match spring rates to the quality of the damper. The basic rule of thumb is you want to use the least amount of spring rate you can get away with because only then are you getting what you paid for in the dampers. In other words, if you overpower a high-end system like a JRZ RS Pro with 900-1000, you will be robbing the dampers of their ability to work for you and you will be mostly riding on your springs.

FYI, with JRZ RS Pro, the factory recommends 550-750 for the E90.

Best thing you could do though is give a call over to Alex Roy at Olsen Motorsports in IL. He's the shop BMW guru and super helpful with all things suspension (312-810-5353).
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      01-27-2015, 01:15 PM   #3
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If you are going on coilovers, 1k is super soft still.. prob feel like oem.. barely any difference.

Fot a real track car, you can go much stiffer. but also depends on your ride height and how picky you are about comfort when on the streets.
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      01-27-2015, 02:37 PM   #4
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Quote:
Originally Posted by GabeS View Post
If you are going on coilovers, 1k is super soft still.. prob feel like oem.. barely any difference.

Fot a real track car, you can go much stiffer. but also depends on your ride height and how picky you are about comfort when on the streets.
1K in nm (which is used by most Japanese manufacturers) yes is still soft. But NOT 1K in lbs. a 1000lb spring on the front will possibly rob the suspension travel a fair bit. I have NEVER seen any race car with a 1K (at least not until now) and certainly not recommended even with slicks.

OEM is 150lbs so over 6 times the spring rate over stock, one will be bouncing and will know the difference

Cheers,

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      01-27-2015, 02:40 PM   #5
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Quote:
Originally Posted by okusa View Post
Your analysis is actually backwards. First you have to decide on dampers and only then you can match spring rates to the quality of the damper. The basic rule of thumb is you want to use the least amount of spring rate you can get away with because only then are you getting what you paid for in the dampers. In other words, if you overpower a high-end system like a JRZ RS Pro with 900-1000, you will be robbing the dampers of their ability to work for you and you will be mostly riding on your springs.

FYI, with JRZ RS Pro, the factory recommends 550-750 for the E90.

Best thing you could do though is give a call over to Alex Roy at Olsen Motorsports in IL. He's the shop BMW guru and super helpful with all things suspension (312-810-5353).
Thanks for the contact, but I completely disagree. Every high quality, rebuildable track oriented damper can be valved to match any spring rate you want. Choosing spring rate has nothing to do with the "quality" of the damper. You can run any rate you want on a single adjustable such as MCS, JRZ, Ohlins...they simply match the valving to the spring rate. More knobs to turn doesn't necessarily mean better "quality", or more spring rate, it just means more adjustability.

You choose spring rates ranges that match your intended use, including other considerations such as tire choice, local tracks, car weight etc. etc. Most M3 "kits" assume they will drive to the track and around town, that is not my case. However, this doesn't mean I need/want a triple adjustable setup.

Like I said, I've driven on high quality, correctly valved single adjustable monotubes, and just seeing if anybody has run on spring rates higher than the KW and Bilstein clubsports which both seem to be about 500/800, which IMO seems soft for a "clubsport" track car.

I ran 700/800 on my E46 track car, and it was considerably lighter, and had big turner sway bars. I have no idea how 500# front spring is nearly enough for the E92.
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      01-27-2015, 03:35 PM   #6
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depends on your setup. If you're not using slicks or aero you probably don't need that much rate. Also if you're ditching the divorced spring and damper for a true coilover for the rear you won't need as much rear rate either.

I'm running 860 up front and 980 in back on AST doubles. The setup is very balanced running 305 square with a GT wing and front splitter. I could probably increase the rates even more since most the tracks I frequent are very smooth surfaces. I'll likely wait until I need another rebuild before go up more.

I had them rebuilt for these rates, and I've got the dampers set close the middle range of its adjustments. It's nice having a nice set where I'm not having to run them maxed out like some other people I know. The previous setup was 1000 in front and 1100 in the rear. That setup worked too but the springs were too short for a car that still drives to and from the track.
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      01-27-2015, 04:27 PM   #7
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Quote:
Originally Posted by TrakBch View Post
depends on your setup. If you're not using slicks or aero you probably don't need that much rate. Also if you're ditching the divorced spring and damper for a true coilover for the rear you won't need as much rear rate either.

I'm running 860 up front and 980 in back on AST doubles. The setup is very balanced running 305 square with a GT wing and front splitter. I could probably increase the rates even more since most the tracks I frequent are very smooth surfaces. I'll likely wait until I need another rebuild before go up more.

I had them rebuilt for these rates, and I've got the dampers set close the middle range of its adjustments. It's nice having a nice set where I'm not having to run them maxed out like some other people I know. The previous setup was 1000 in front and 1100 in the rear. That setup worked too but the springs were too short for a car that still drives to and from the track.
305 Nittos? widebody?

Mine will be GT4 type front splitter and rear wing, so not big aero, but a little. 275 square, NT01 tires. I might try to use a 275-40-18 in the rear, instead of 35, for a little more grip and progressiveness. Will use the divorced rear setup, as my rear shock tower will not be reinforced (only a alekshop rear bar).

Nice to see your front/rear rates closer. The front needs roll resistance anyway, 700/900 was kinda what I was thinking.
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      01-27-2015, 08:07 PM   #8
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I went with 700/1000 on MCS 2 ways and NT-01s. Specific to track use and occasionally to and from the track.
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      01-27-2015, 08:46 PM   #9
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Quote:
Originally Posted by Mvez View Post
Nice to see your front/rear rates closer. The front needs roll resistance anyway, 700/900 was kinda what I was thinking.
Disclaimer: I know nothing about BMW setups, just trying to learn.

Don't you think double or triple adjustable shocks would be better suited with those spring rates?

Also, why the square setup? Does that provide better balance on the M3 or is it more for the economics of tires?

TIA.
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      01-27-2015, 10:06 PM   #10
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When discussing spring rates, especially for the rear, are you planning on stock spring perches or true coil-overs in the rear?

Why not call James at Bimmerworld and ask for a recommendation (or call MCS directly?). They can likely valve your shocks to match the spring rate you desire, though they may steer you in a different direction.
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      01-27-2015, 11:05 PM   #11
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Quote:
Originally Posted by evilspiritM3 View Post
I went with 700/1000 on MCS 2 ways and NT-01s. Specific to track use and occasionally to and from the track.
That's what I'm looking for, thanks. How does it feel? Pretty balanced?
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      01-28-2015, 01:06 AM   #12
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Quote:
Originally Posted by Mvez View Post
305 Nittos? widebody?

Mine will be GT4 type front splitter and rear wing, so not big aero, but a little. 275 square, NT01 tires. I might try to use a 275-40-18 in the rear, instead of 35, for a little more grip and progressiveness. Will use the divorced rear setup, as my rear shock tower will not be reinforced (only a alekshop rear bar).

Nice to see your front/rear rates closer. The front needs roll resistance anyway, 700/900 was kinda what I was thinking.
I've also got the GT4 Splitter with GT4 flaps and APR GT250. I've got a APR splitter waiting to go on, but I need to have the oil cooler cutouts done before installing it.

Stock Body. I run 305/645-18 Pirelli Slicks all around. -3.7 Camber up front.
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      01-28-2015, 01:25 AM   #13
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Quote:
Originally Posted by FTS View Post
Disclaimer: I know nothing about BMW setups, just trying to learn.

Don't you think double or triple adjustable shocks would be better suited with those spring rates?

Also, why the square setup? Does that provide better balance on the M3 or is it more for the economics of tires?

TIA.
Throwing money at the car is not always such a good idea. Double and triple adjustable dampers provide just that, more adjustability. More adjustability can equal more confusion. I would bet that most drivers do not have their high-end double or triple adjustable suspension dialed in properly. JRZ and MCS singles are a great way to go for anyone who is heavily into HPDE's and not racing competitively. Don't get me wrong, doubles and triples in the right hands obviously have there advantages. For me, absolute overkill.

Most e36, e46 and e9X drivers prefer a square setup for multiple reasons. More front end grip creates better turn in, and the square setup will also dial out the factory understeer. Furthermore, the ability to rotate tires effectively on all four corners can have a great impact on your yearly track budget. If you pack for the track like I do (trailer is not in the budget yet), then space is limited. With a square setup, you can get away with having one spare since all wheels/tires are the same.

Quote:
Originally Posted by TrakBch View Post
I've also got the GT4 Splitter with GT4 flaps and APR GT250. I've got a APR splitter waiting to go on, but I need to have the oil cooler cutouts done before installing it.

Stock Body. I run 305/645-18 Pirelli Slicks all around. -3.7 Camber up front.
What are your wheel spec's if you don't mind me asking?
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      01-28-2015, 09:08 AM   #14
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Quote:
Originally Posted by AP3X_FTW View Post
Throwing money at the car is not always such a good idea. Double and triple adjustable dampers provide just that, more adjustability. More adjustability can equal more confusion. I would bet that most drivers do not have their high-end double or triple adjustable suspension dialed in properly. JRZ and MCS singles are a great way to go for anyone who is heavily into HPDE's and not racing competitively. Don't get me wrong, doubles and triples in the right hands obviously have there advantages. For me, absolute overkill.
Yes certainly double or triples require more knowledge, but it is just about learning. Mvez has quite a bit of experience already in this regard if I remember correctly. Just because it is more confusing should not mean throwing money out the window. The potential issue with high spring rates and single adjustables is you will be very limited to finding a good setup from track to track. Controlling the energy those springs generate without compression and rebound independent of one another will not yield good results IMHO. If you go with doubles, you might as well go with triples to be able to control the low and high frequency compression settings independently as well.

Quote:
Originally Posted by AP3X_FTW View Post
Most e36, e46 and e9X drivers prefer a square setup for multiple reasons. More front end grip creates better turn in, and the square setup will also dial out the factory understeer. Furthermore, the ability to rotate tires effectively on all four corners can have a great impact on your yearly track budget. If you pack for the track like I do (trailer is not in the budget yet), then space is limited. With a square setup, you can get away with having one spare since all wheels/tires are the same.
I understand this; however, isn't the front clearance much more limited than rear? So, if the front allows only for 275 or 285 tires, you will limit yourself to that size in the rear as well? Or is it that if the rears are wider than the front, it creates terminal understeer?
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      01-28-2015, 12:49 PM   #15
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Since it sounds like you are building a serious track car, you will need multiple sets of springs for different tracks and conditions. Your ranges look about right. Get springs in 100lb increments, gather data, and seen what you like. I personally like springs on the softer side of the range, but everyone has their preferences.
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      01-28-2015, 12:55 PM   #16
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OP, what I am not seeing in your thread (and might be irrelevant) is your plan on swaybars. Will you be using OEM or go a tad stiffer and run aftermarket (RD Sport maybe)?

Since spring rates are also affected by sway bars, running a stiffer spring might not necessarily be a good thing when the sway bar can provide that added support while not overpowering the chassis (rear spring rate of 1k lbs).

Just a thought to consider and remember that stiffer is not always better...in some cases
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      01-28-2015, 04:45 PM   #17
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I have a track buddy that runs 700 in front (don’t know rears). He and the car is very fast at 3200lbs. dry no driver. aero, MCS doubles on Yoko slicks. He seems to like it.
I have run 1000 front 500 rear (coilovers in rear) on my 2900lbs. e46 M3. It takes precise, smooth and quick inputs or it will not do what you want. Going forward we are adding weight (S62) and lowering the spring rates down to 900 or 950. I only mention because the lower spring rates (700) might be easier to drive.
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      01-28-2015, 06:09 PM   #18
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Quote:
Originally Posted by evilspiritM3
I went with 700/1000 on MCS 2 ways and NT-01s. Specific to track use and occasionally to and from the track.
I am using 700/1000 with MCS 2 way.
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      01-28-2015, 06:45 PM   #19
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I am using 700/1000 with MCS 2 way.
Bimmerworld's goto numbers.......
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      01-28-2015, 08:15 PM   #20
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Quote:
Originally Posted by PrimeBMW
Quote:
Originally Posted by surlynkid View Post
I am using 700/1000 with MCS 2 way.
Bimmerworld's goto numbers.......
Yup. I spent a lot of time on the phone with James Clay building the entire suspension of the car. The car really moves now.
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      01-29-2015, 08:53 AM   #21
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Do you guys run a rear bar with those spring rates? What's the wheel rate on an E92M3 in the rear?

Goodness those seem like high numbers, but the E92M3 is a big girl to dance with, so you want some help!

Going to the track with double adjustables requires pre-planning. If I didn't have a plan of attack prior to arriving at the track (written down, btw), I was struggling b/c there were a million other things to do/remember on a race weekend. I'd tweak this or tweak that based on what the butt dyno and tire temps were telling me.

Having a plan, especially if there is a test day the day before, will help you realize great results. Design of experiments can really help (as does experience, of course...) narrow things down with a completely new setup on a new track.
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      01-29-2015, 12:27 PM   #22
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I swapped to bigger bars per BimmerWorld recommendations, and mine are 3 way adjustable.
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