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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. |
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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OEM is 150lbs so over 6 times the spring rate over stock, one will be bouncing and will know the difference Cheers, Lutfy |
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01-27-2015, 02:40 PM | #5 | |
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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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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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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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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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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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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. What are your wheel spec's if you don't mind me asking?
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Last edited by AP3X_FTW; 01-28-2015 at 01:32 AM.. |
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01-28-2015, 09:08 AM | #14 | ||
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Quote:
Quote:
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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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Stoptech 380mm/355mm | PFC08 / Pagid RS-29 | Akrapovic EVO - CF tips | Benvo Tune | MS UDP | AA air filter | MCS 2-way with 700/1000lb springs | Solid bushings and adjustable links | RD front swaybar | Apex EC-7 18x10 square 275/35-18 NT01 | Turner Race Studs | GT4 Brake Cooling | GT4 Power Steering Cooling | Alekshop Oil Cooler | Performance Steering Wheel | | CF Spoiler | Varis System 1 Full CF Diffuser | Extended Paddle Shifters | Schroth Quick Fit Pro | Turner Steering Rack Stops | Vorshlag Camber Plates
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01-28-2015, 08:15 PM | #20 |
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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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Stoptech 380mm/355mm | PFC08 / Pagid RS-29 | Akrapovic EVO - CF tips | Benvo Tune | MS UDP | AA air filter | MCS 2-way with 700/1000lb springs | Solid bushings and adjustable links | RD front swaybar | Apex EC-7 18x10 square 275/35-18 NT01 | Turner Race Studs | GT4 Brake Cooling | GT4 Power Steering Cooling | Alekshop Oil Cooler | Performance Steering Wheel | | CF Spoiler | Varis System 1 Full CF Diffuser | Extended Paddle Shifters | Schroth Quick Fit Pro | Turner Steering Rack Stops | Vorshlag Camber Plates
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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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Stoptech 380mm/355mm | PFC08 / Pagid RS-29 | Akrapovic EVO - CF tips | Benvo Tune | MS UDP | AA air filter | MCS 2-way with 700/1000lb springs | Solid bushings and adjustable links | RD front swaybar | Apex EC-7 18x10 square 275/35-18 NT01 | Turner Race Studs | GT4 Brake Cooling | GT4 Power Steering Cooling | Alekshop Oil Cooler | Performance Steering Wheel | | CF Spoiler | Varis System 1 Full CF Diffuser | Extended Paddle Shifters | Schroth Quick Fit Pro | Turner Steering Rack Stops | Vorshlag Camber Plates
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