My E90 M3 Dedicated Track build (with pix!)

[dogbone]

Originally Posted by tsk94

Can someone try the link now and let me know if it works? When you open it now it should ask if you want to make a copy, click yes. Then you should have access to the spreadsheet and be able to edit it. You will need a google account for this but I assume most do. Otherwise I can post the original link which has an option to download the spreadsheet so you can open it in Excel.

https://docs.google.com/spreadsheets...p-FDeDMek/copy

Works! Thanks!

[tsk94]

Originally Posted by dogbone

Works! Thanks!

Great!

I made a few typo corrections in the sheet for anyone that's downloaded it originally. Namely in the wheel frequency section where it said How to calculate wheel rates instead of how to calculate wheel frequencies - should be straightforward but incase anyone got confused lol.

[e36clubracer]

Something to consider besides your spring rates is your shock pressure. That will affect ride height and dampening characteristics. Not sure if the JRZs you had previously allowed for pressure adjustments.

The info I got from MCS is its not linier like a spring but a basic average is 10psi to 5.7lbs.

[tsk94]

Originally Posted by e36clubracer

Something to consider besides your spring rates is your shock pressure. That will affect ride height and dampening characteristics. Not sure if the JRZs you had previously allowed for pressure adjustments.

The info I got from MCS is its not linier like a spring but a basic average is 10psi to 5.7lbs.

I agree that shock pressure is a consideration, but it's more useful as a fine tuning option.

You're not going to play around with reservoir pressure to alter handling balance to large degrees. It's not an effective approach because as you mentioned the changes are very small and the range of adjustment is fairly limited. You'll want to be doing this with springs and sway bar adjustments, and use canister pressure to fine tune. Also, a lot of people don't have remote reservoir shocks, so it's not even applicable to them.

The goal of this analysis is to put a numerical value to a certain handling balance feel an individuals car has in the steady-state. Roll-stiffness is what contributes to this, shocks (low and high speed adjustments) do not play a role. Canister pressure does have a slight influence, but not enough to be concerned with. You could always estimate the effective spring rate the canister pressure contributes front and rear and add it to the spring rate if you want them to be roughly considered in the analysis.

The front roll couple distribution spreadsheet is much more useful and I hope to get it posted shortly. The wheel rate and frequency one I posted is more for peoples curiosity. Unless you have a good understanding of wheel frequencies and your own opinion on how to tune a car around frequencies, the numbers themselves aren't very useful.

[e36clubracer]

No doubt it's fine tuning. But if you're calculating wheel rates you should be documenting this too if your shocks allow for adjustment of pressure easily trackside. It's something you should be tracking regardless to make sure they are operating in the expected windows.

[dogbone]

Originally Posted by e36clubracer

Something to consider besides your spring rates is your shock pressure. That will affect ride height and dampening characteristics. Not sure if the JRZs you had previously allowed for pressure adjustments.

The info I got from MCS is its not linier like a spring but a basic average is 10psi to 5.7lbs.

I have my own nitrogen rig that can do very accurate psi and with the JRZ, I did experiment with different pressures in the remote canisters. I tended to like the higher pressures.

On the MCS, I was advised to start on the low side, so I've started low. I have some pretty stiff springs so I think it has been a good place to start. Feels good to me so far.

[derbo]

Originally Posted by tsk94

I agree that shock pressure is a consideration, but it's more useful as a fine tuning option.

You're not going to play around with reservoir pressure to alter handling balance to large degrees. It's not an effective approach because as you mentioned the changes are very small and the range of adjustment is fairly limited. You'll want to be doing this with springs and sway bar adjustments, and use canister pressure to fine tune. Also, a lot of people don't have remote reservoir shocks, so it's not even applicable to them.

The goal of this analysis is to put a numerical value to a certain handling balance feel an individuals car has in the steady-state. Roll-stiffness is what contributes to this, shocks (low and high speed adjustments) do not play a role. Canister pressure does have a slight influence, but not enough to be concerned with. You could always estimate the effective spring rate the canister pressure contributes front and rear and add it to the spring rate if you want them to be roughly considered in the analysis.

The front roll couple distribution spreadsheet is much more useful and I hope to get it posted shortly. The wheel rate and frequency one I posted is more for peoples curiosity. Unless you have a good understanding of wheel frequencies and your own opinion on how to tune a car around frequencies, the numbers themselves aren't very useful.

I appreciate your efforts.

I definitely don't understand why this magical "300" spring rate delta has been so popular. 400/700, 500/800, 600/900, 700/1000. I don't get how 300 has the same weight in all these configurations (if it does at all) or why it is fixated in this gap. fsmtnbiker tsk94

[tsk94]

Originally Posted by derbo

I appreciate your efforts.

I definitely don't understand why this magical "300" spring rate delta has been so popular. 400/700, 500/800, 600/900, 700/1000. I don't get how 300 has the same weight in all these configurations (if it does at all) or why it is fixated in this gap. fsmtnbiker tsk94

Likely because one of the biggest aftermarket names for BMW in North America recommends it, and similar spring rates have been used for generations since the E36's. Not saying BW doesn't know what they're talking about, you can definitely make a setup using these spring rates work - my question is, is there a better option?

Interestingly, the 300 delta is not linear in the front to rear relative stiffness. A 800/1100 setup is more front biased (stiffer in the front relative to the rear) then a 500/800 setup is. Because the front spring rates increases by 60%, but the rear only be 38%. So, as you go towards more track/race orientated spring rates (using this popular 300# delta) the car becomes more understeer biased as the front roll stiffness is increasing by more then the rear. Yes.. this can be offset by other changes but we're talking specifically about spring rates here.

[Bartledoo]

Just did a session on 628f/1120r and it's pretty nice. Could still use more rear bias.

[tsk94]

Originally Posted by Bartledoo

Just did a session on 628f/1120r and it's pretty nice. Could still use more rear bias.

I believe fsmtnbiker used ~630 in the front and ~1200 in the rear. I think he's gone a bit softer front and rear, similar to you but slightly softer in the front.

What sway bar setup are you using?

[fsmtnbiker]

Yup I'm 560/1120 right now with an Eibach front bar on either the middle or stiff setting.

I've also run 515/1000 w/ eibach and 670/1230 w/ OEM front bar.

All are pretty good and pretty similar on front/rear bias. A little oversteer biased at low speeds on the stiffest setup, I was going to try the eibach bar with that setup but I let a coworker borrow the front springs so I'm just waiting until I get those back.

Having the adjustable front bar is a nice fine adjustment to really dial the car in. I wouldn't bother with anything stiffer but I keep having to raise the car to keep the aero off the ground, so I'm hoping I can bump the rates up a bit and bring the ride height back down incrementally.

[Bartledoo]

Originally Posted by tsk94

I believe fsmtnbiker used ~630 in the front and ~1200 in the rear. I think he's gone a bit softer front and rear, similar to you but slightly softer in the front.

What sway bar setup are you using?

Stock sways.

I dusted off the sim rig and turned AC the other day. The M3 GT4 spoiled me with its rotation.

[tsk94]

Originally Posted by fsmtnbiker

Yup I'm 560/1120 right now with an Eibach front bar on either the middle or stiff setting.

I've also run 515/1000 w/ eibach and 670/1230 w/ OEM front bar.

All are pretty good and pretty similar on front/rear bias. A little oversteer biased at low speeds on the stiffest setup, I was going to try the eibach bar with that setup but I let a coworker borrow the front springs so I'm just waiting until I get those back.

Having the adjustable front bar is a nice fine adjustment to really dial the car in. I wouldn't bother with anything stiffer but I keep having to raise the car to keep the aero off the ground, so I'm hoping I can bump the rates up a bit and bring the ride height back down incrementally.

How did you arrive at your spring rates? Did you base it off any calculations like wheel rates or natural frequencies, or was it solely based off of feel and adjusted accordingly?

I want to increase my rear stiffness relative to my fronts. Just not sure if I want to go softer in the front or stiffer in the rear, or perhaps a combo of both. Currently have 800/1150 (570 in a coilover), so pretty inline with the typical track 'recommended' setup. Definitely needs more rear relative to the front at the moment.

Originally Posted by Bartledoo

Stock sways.

I dusted off the sim rig and turned AC the other day. The M3 GT4 spoiled me with its rotation.

You mention you're looking for a bit more rear bias, is that specifically for mid corner rotation/less understeer still? If it's for entry/exit, any reason you'd want to accomplish this with stiffer springs vs. damper tweaks?

This is assuming by wanting more rear bias still you meant more rear spring..

[Bartledoo]

Originally Posted by tsk94

You mention you're looking for a bit more rear bias, is that specifically for mid corner rotation/less understeer still? If it's for entry/exit, any reason you'd want to accomplish this with stiffer springs vs. damper tweaks?

This is assuming by wanting more rear bias still you meant more rear spring..

yea mid-corner rotation could be better, and entry at mid-lower speeds. I can't really trail brake any harder haha. I softened front compression a click but I don't really want to go any softer in the front. I have rear compression set harder than front which gives good exit. Maybe I'm just lazy, but I also don't want to turn the steering wheel so much lol.

Problem is that I don't really think I should throw anymore spring at the KW CS dampers. I also could use a good diff.

Sorry for the general track chit-chat dogbone!

[dogbone]

Since I trailered the rig to Colorado a couple weeks ago, I've done a bunch of maintenance work to the towing rig and the car. After all the work was done, I was eager to get to High Plains Raceway with the E90. I've been wondering for 2.5 years what the E90 could do at High Plains. Until now, I've only been able to drive there with the street E92.

Buuuuut, HPR didn't have any events on the schedule until the New Year. The weather this week was looking really nice (high 68ºF), so I decided to book HPR semi-exclusive and went today. Turns out I was the only one at the track today.

This marks the first time that the E92 and E90 have been to the same track. The E92 never went to a CA track, and the E90 has never been in CO until now.

My best in the E92 was a 1:58.6. I did that in 2019. In 2020, my best has been a 1:59.1. The question was, how much faster would I go in the E90. I knew the layout of the track, but everything simply happens at a different pace in the E90. Definitely took some getting used to. And if I'm being honest, my driving was not clean today. I struggled to get through a single clean full lap all day. The track is tricky and I was not adapting to the E90 right away. I admit, I was pushing really hard which quite often doesn't give you the result you want. I was also experimenting all day with braking zones, gear selection, track position, etc. Yes, I enjoyed my 3x going 4-off. I'm sure the blooper reel would be more interesting than the fast lap---giving myself the middle finger for driving like a moron....you know, the normal stuff.....

Anyway, I managed a 1:51.2 on my 3rd outing. I was on scrubs all day. Sadly, I gave up numerous 1:50.xx because I couldn't put all the pieces together consistently. My fastest lap was with Pirelli on the front and Yoko in the rear. I tried several tire combinations.

Of all the things I ordered in the last couple weeks, the one thing I did not receive yet were the softer rear springs. Today's event confirmed that I want to try softer springs in the rear. The rear comes around more frequently and easily than I'd like. Hopefully they'll arrive soon. Otherwise, the MCS felt good again.

Ok, prepare for the messy fast lap:

There's definitely more to be had out there. I was much more comfortable later in the day, but at 70ºF, it wasn't pulling like when it was 45ºF. I'll probably do this again a couple times before February. Definitely want to go back with softer rear springs and new front aero.

(The grip level difference between the newly paved Chuckwalla and older pavement HPR is quite dramatic.)

[tsk94]

I can't believe rhyary 's mixed tire idea is catching on..

[dogbone]

Originally Posted by tsk94

I can't believe rhyary 's mixed tire idea is catching on..

Haha it’s really quite simple. The Pirelli 305 is the fattest slick I can fit in front and the Yoko 300 (which is an inch wider than the Pirelli is the fattest slick I can put at the rear.

[tsk94]

Originally Posted by dogbone

Haha it’s really quite simple. The Pirelli 305 is the fattest slick I can fit in front and the Yoko 300 (which is an inch wider than the Pirelli is the fattest slick I can put at the rear.

Haha, I understand. I just like poking fun at him for it

Are you doing the mix simply because you had both and decided to try them together? You could always run a 315 or 325 DH in the rear.

[dogbone]

Originally Posted by tsk94

Haha, I understand. I just like poking fun at him for it

Are you doing the mix simply because you had both and decided to try them together? You could always run a 315 or 325 DH in the rear.

Yokos are the spec tire for Global Time Attack now, so I have them around since I just did a GTA event. Pirelli scrubs are what I like to knock around on. I gave the combo a try at Chuckwalla and like it, so I figured I’d give it another go today. I guess I could explore a fatter DH. I just got so used to running square and being able to rotate around.

[tsk94]

Originally Posted by dogbone

Yokos are the spec tire for Global Time Attack now, so I have them around since I just did a GTA event. Pirelli scrubs are what I like to knock around on. I gave the combo a try at Chuckwalla and like it, so I figured I’d give it another go today. I guess I could explore a fatter DH. I just got so used to running square and being able to rotate around.

Makes sense. The square setup is definitely nice for rotating around, but if you like the current setup, which is essentially a stagger as the Yoko's measure wide, you might like the 305/315 or 325 DH setup -something to consider maybe

Sounds like a nice day though, having the track all to yourself!

[PrimeBMW]

Try more front camber for those Yoko's 😉

[dogbone]

Originally Posted by tsk94

Sounds like a nice day though, having the track all to yourself!

Yeah, it’s pretty darn cool to be the only one on track. I’ve had that situation at Buttonwillow too—-no one else around.

Apparently, someone else had booked today but cancelled last minute.