Sprung corner weights, motion ratios, and hertz

[Melchior]

Originally Posted by Melchior

It's linked through Google photos, and it's a shared picture and album... do you need to have a gmail account to view these? Can anyone else see them? If not, I'm still a former photobucketer, where should I host these to link?

Try this link to my shared album with the two screen shots I posted.

https://photos.app.goo.gl/LJL20kKWjZPKO8q03

[MidLifeM3]

Originally Posted by Melchior

Try this link to my shared album with the two screen shots I posted.

https://photos.app.goo.gl/LJL20kKWjZPKO8q03

thank you!

when I remove a swaybar and offset it with the equivalent calculated spring rate. No matter what I did to the shocks, I could not get the spring only end of the car to transition as quickly through slaloms or fast changes in direction.

Interesting that you had this experience. On my previous car (a 1st gen MR2), I intentionally built that one around keeping the (wimpy) stock bar and setting the roll rate balance with springs. On that car it worked out really great, corner entry stability was vastly improved from reduced dive under braking and much more predictable and stable transition from braking to cornering. Ride quality, ummm, less than comfy, but handling and responsiveness was great. But, that was a very different car with very different constraints than the M3 so not surprising to get a very different solution.

[Richbot]

I like having a bar at both ends for tuning behavior at the opposite end of the car too. More front bar to keep the inside rear down for instance

[Visceral]

I cant seem to shake this bunch of #'s:

Suspension Freq (Hz)
LF RF
2.35 2.35
LR RR
2.05 2.05


Motion Ratio
F R
0.96 0.563

Wheel Rates
Front Left Front Right
479.1439129 449.8315794
Rear Left Rear Right
298.1287448 272.8199737


Spring Rates
Front Left Front Right
519.9044193 488.0985019
Rear Left Rear Right
940.5612057 860.7150026

Avg F Metric
504.0014606 9.000026083 <---
Avg R
900.6381042 16.08282329 <---

I've noticed *a lot* of people and kits go for either 500/800 (KW & Bilstein Clubsports, JRZ) OR 600/900 (MCS, lots of good experience).

Its really tempting to try 500/900 (9/16) and see where to go from there, possibly adjusting a front bar to "get up to" 600.

Anyone else try 500/900?

[Melchior]

I show 500/900 to have a slightly lower front bias compared to my setup when you include OEM swaybars into the equation. That’s probably close to where I’ll end up next if I swap out rear springs to something stiffer. It should be balanced, but depending on tires it could be more towards oversteer at times.

You may have trouble putting power down out of corners with the stock front bar too. This is more an autocross thing, but slower corners on track may act the same.

[Visceral]

The next thing I'm struggling with is dampener quality. Where are the spool-valve applications?

A new set of 2way-remote MCS with all the necessary bits is $6500. Fankly, that's a sh*t-ton of $$$.

KW, Bilstein (when they start building aftermarket stuff again), and JRZ all make much less expensive coilover systems, but if you listen to the forums and the vendors you believe that these are inferior systems that will ruin your streetability.

I need to take this whole process cautiously, so I should have time to watch the classified in case any MCS w/remote come available.

Also, if someone has an "Actually, my experience with XXXXXX was amazing...", I'd be excited to hear it. I don't mind trying out $2k brakes as an iterative process, but I don't have the data acquisition gear to successfully iterate suspension.

[ricardofors68]

Visceral, that's why I went with the Ohlins, $6.5k is too much for a driver and car that will not see a proper race, maybe, with luck a tt event, years from now. Matter of fact I have used the same approach to the car build and so far, with two hpde events in the books, couldn't be happier with the level of performance.
Just need to pay attention to how the whole package behaves and evolves. For instance, already know that my track oriented pads were not enough for me, so on will be a more focused set. Suspension-wise, I will be adding a couple of click to stiffen things up a bit more. Have fun, be safe..
All in all, seems like we are traveling parallel lines with our builds. Good luck with yours.

[Fitzpadj]

Originally Posted by Visceral

The next thing I'm struggling with is dampener quality. Where are the spool-valve applications?

A new set of 2way-remote MCS with all the necessary bits is $6500. Fankly, that's a sh*t-ton of $$$.

KW, Bilstein (when they start building aftermarket stuff again), and JRZ all make much less expensive coilover systems, but if you listen to the forums and the vendors you believe that these are inferior systems that will ruin your streetability.

I need to take this whole process cautiously, so I should have time to watch the classified in case any MCS w/remote come available.

Also, if someone has an "Actually, my experience with XXXXXX was amazing...", I'd be excited to hear it. I don't mind trying out $2k brakes as an iterative process, but I don't have the data acquisition gear to successfully iterate suspension.

"Damper" quality lol. You aren't watering your shocks

The MCS is fantastic. Good dampers are worth every penny even though you might not see the lap time.

Going from a Bilstein or KW, you will drop a bit of time going to a quality damper; but mostly the car will be easier to drive and the shocks will stay more consistent over their life.

As far as single vs 2-way remote; I did not see a significant difference going from a MCS single to an MCS 2-way remote in the dry. The huge advantage was in being able to adjust for differences in track conditions. I think for an HPDE-er; a single MCS is the way to go; and even most club racers it's more than enough. A MCS single vs a KW 2-way? I'll take the MCS every day.

[Visceral]

Originally Posted by Fitzpadj

"Damper" quality lol. You aren't watering your shocks

http://grammarist.com/usage/dampen-damper-dampener/ makes it sound like both work for shocks but only one works for making something wet.

But I appreciate the rest of your post

My big app for the dual adjustability is street vs track. My wife still loves to drive the M3 and I don't want to ruin that.

[CSBM5]

Originally Posted by Visceral

http://grammarist.com/usage/dampen-damper-dampener/ makes it sound like both work for shocks but only one works for making something wet.

But I appreciate the rest of your post

My big app for the dual adjustability is street vs track. My wife still loves to drive the M3 and I don't want to ruin that.

He's referring to the generally accepted mechanical engineering term in vibration analysis where engineers make fun of the "dampener" outsiders.

Any update on where you ended up with your decision?

[Visceral]

Originally Posted by CSBM5

He's referring to the generally accepted mechanical engineering term in vibration analysis where engineers make fun of the "dampener" outsiders.

Any update on where you ended up with your decision?

I'm currently saving up for the MCS (or biding my wife's attention since the purchase of the brakes).

My calculations suggest further apart #s (550/900) than the vendors want to sell me (550/800, 600/900, 700/1000). So I'm still confused by that.

[admranger]

Originally Posted by Visceral

I'm currently saving up for the MCS (or biding my wife's attention since the purchase of the brakes).

My calculations suggest further apart #s (550/900) than the vendors want to sell me (550/800, 600/900, 700/1000). So I'm still confused by that.

Does the friction of the suspension components (especially any bushings in the system) effect your calculations?

Also, have you looked at any back issues of Racecar Engineering out of the UK?

Racecar Engineering That magazine had lots of technical articles.

SAE papers are also great references.

[Chris_PDX]

Originally Posted by Visceral

I'm currently saving up for the MCS (or biding my wife's attention since the purchase of the brakes).

My calculations suggest further apart #s (550/900) than the vendors want to sell me (550/800, 600/900, 700/1000). So I'm still confused by that.

Have you talked to Eddie @ AR yet? They have a customer car (grey E92 M3, he's on this forum but I can't remember his forum name now, his name is Mark) that's running MCS and is dialed really well. Probably the quickest E9x M3 on track in the state.

Understand you are looking for a starting point and not someone to just do it for you, but Eddie can probably give you that starting point even with MCS doubles.

[rhyary]

Subscribed.
Like to learn what you find.
I have 750 front / 900 rear (not a daily driver)
I am a drive and adjust, but will appreciate the scientific approach

[Visceral]

Originally Posted by Chris_PDX

Have you talked to Eddie @ AR yet? They have a customer car (grey E92 M3, he's on this forum but I can't remember his forum name now, his name is Mark) that's running MCS and is dialed really well. Probably the quickest E9x M3 on track in the state.

Understand you are looking for a starting point and not someone to just do it for you, but Eddie can probably give you that starting point even with MCS doubles.

Yeah, I have a little. Gabe and Martin at AR have put quotes together. I'm excited that they'll match Bimmerworlds $'s, since they're local and would offer local support.

They believe that a maximum spread (f-r) of 250 lbs is what works. This is in direct opposition to the numbers, but its a good data point. I think 550/800 is where they'd like me to be, rather than the 600/900 or 700/1000 everyone related to Bimmerworld suggests and the 500/900 the number recommend. It will be fun nonetheless.

[Visceral]

I ended up with MCS doubles (non-remote, latest "setup") and 700/1000 springs. I need to do the math, but I'm incredibly surprised how compliant it is. The MCS make the 700/1000 workable.

Strangely, the car can't put power down well on corner exit, so I'm double-checking alignment, moving from the Dinan non-adjustable to Hotchkiss adjustable front bar (stiffer), and adding the solid rear subframe bushings. I'll then work into spring rates, but offhand 700 seems like a really high (~2.8) front.

Once I dig up my calcs and redo them, I'll repost.

[Visceral]

My current camber is -2.6 front, -2(.1) rear.

[tsk94]

Originally Posted by Visceral

I ended up with MCS doubles (non-remote, latest "setup") and 700/1000 springs. I need to do the math, but I'm incredibly surprised how compliant it is. The MCS make the 700/1000 workable.

Strangely, the car can't put power down well on corner exit, so I'm double-checking alignment, moving from the Dinan non-adjustable to Hotchkiss adjustable front bar (stiffer), and adding the solid rear subframe bushings. I'll then work into spring rates, but offhand 700 seems like a really high (~2.8) front.

Once I dig up my calcs and redo them, I'll repost.

Originally Posted by Visceral

My current camber is -2.6 front, -2(.1) rear.

What's your rear toe? You don't have too much rear negative camber and 1000 in the rear isn't unheard of by any means. I'm running 1150 in the rear with -2.3* and 1/8" toe in per side. Car puts down the power very well. Solid subframe bushing and solid rear arms help as they eliminate toe change and deflection under load, such as throttle application.

Could also just soften the rear compression, that will help as well.

[ThunderMoose]

Originally Posted by Fitzpadj

Many a people have done this for lots of different platforms and I have never seen it be right. Find your local fast guy/shop and duplicate his setup and test/change from there.

My coach who is also a race engineer for ARCA driver says the same thing.

[fsmtnbiker]

Originally Posted by Visceral

I ended up with MCS doubles (non-remote, latest "setup") and 700/1000 springs. I need to do the math, but I'm incredibly surprised how compliant it is. The MCS make the 700/1000 workable.

Strangely, the car can't put power down well on corner exit, so I'm double-checking alignment, moving from the Dinan non-adjustable to Hotchkiss adjustable front bar (stiffer), and adding the solid rear subframe bushings. I'll then work into spring rates, but offhand 700 seems like a really high (~2.8) front.

Once I dig up my calcs and redo them, I'll repost.

Did the 2WNR come with bumpstops? Make sure you're not getting into them on exit, I fought with this a bit on the KWs I had prior to the MCS I have now.

I'm on MCS 2WR with 700F/1200R on stock bars currently, car works really well. I also have a clutch-type rear diff, and I needed to add a bit of rear spring to get the car loosened back up after adding it.

[tsk94]

Originally Posted by fsmtnbiker

Did the 2WNR come with bumpstops? Make sure you're not getting into them on exit, I fought with this a bit on the KWs I had prior to the MCS I have now.

I'm on MCS 2WR with 700F/1200R on stock bars currently, car works really well. I also have a clutch-type rear diff, and I needed to add a bit of rear spring to get the car loosened back up after adding it.

I would get a bigger rear bar before upping the rear spring rate. Besides, you shouldn't have any issue being able to get the car to rotate with that spring rate, tweak your setup before doing anything (rear spring rate or bigger rear bar). Plenty of things you can do to make it rotate better.

[Visceral]

Originally Posted by fsmtnbiker

Did the 2WNR come with bumpstops? Make sure you're not getting into them on exit, I fought with this a bit on the KWs I had prior to the MCS I have now.

I'm on MCS 2WR with 700F/1200R on stock bars currently, car works really well. I also have a clutch-type rear diff, and I needed to add a bit of rear spring to get the car loosened back up after adding it.

1200??? Good lord. I dont know your corner weights, but with my weights that would work out to 2.76/2.36 natural frequency... damn.

I had Ryan Otis and Adam Ruff drive the car this weekend and the common phrase was "the back end is very loose."

Which differential did you choose? I have a weird feeling mine is toast and that may be the issue.