Schirmer Kinematics

[roastbeef]

Originally Posted by 72dan

All cars have steering angle change under suspension travel. Back in the day we would go through a lot to bumpsteer a car, moving steering tie rod connections up or down so they are the same length and angle as the lower control arm. And yes it was a ton of work, moving the suspension through full travel with no spring and taking measurements. But I am old and back in the day it was Datsun 240Z or 280Z and there was a lower control arm and a strut, not 5 links. So stiffer springs, shocks, sway bars, suspension bushings and bump steer was the hot setup back then.

I think subtle adjustments can be made with the length of arms giving stock mounting points.
There are two ways to make significant changes, either change pickup points on the chassis or use a different spindle/upright with different connection locations.
Suspension technology has advanced so much in the last 10-20 years it is really amazing to me. Look at the Nurburgring lap times for the last 10-20 years, new 911's 10 or more second a lap faster than the previous generation chassis with basically the same tires, same weight, all geometry, track width, etc.

What seems to make sense is on the rear suspension if the bushings were softer that controlled the leading edge of the rear tire versus the trailing edge of the rear tire, in a corner the outside tire is loaded so the front bushing would compress more allowing the tire to turn into the corner slightly. At the same time the inside tire with the same softer bushing controlling the leading edge the inside leading edge would flex more allowing for slight toe out on the inside rear tire.
I have no idea how much rear steer is ideal.

is there a way to test and tweak this while the car is stationary? i can see a fun experiment being setting up the car on toe plates so there is no scrubbing and adding weight to each corner independently to see static results. i would imagine this rear steer simulation would yield the same result if the car was moving, right?

it would be cool to be able to test this without having to wait for a test and tune day to come up to get to the track. i mean... someone has their alignment specs somewhere- i doubt they have a non-disclosure agreement with their clients. lol

[72dan]

Originally Posted by M3 Number 86

72dan who are you? you are in los angeles - do you hit the track a lot?

Once in a while, not enough. My suspension became a nightmare dragged out for almost a year. I ran a few NASA races last year in a tube frame car. Take out two stroke karts or a shifter kart once in a while. Tested a few other race cars.

I would like to have a dedicated track car but no space.
I will likely run a few endurance races this year renting a seat with a team.

It’s all about time and money...
I love my M3, yeah race suspension but it’s a steeet car. I bought it new w every option and it’s in excellent condition. I can’t gut it and cage it.
Also hard to put $100K into a 3500 lb street car to make it fast and lose my fun street car. After you start going out in tube frame cars under 2,000 lbs it’s like why bother with a production car.

Tires, brakes, everything lasts longer when the car is lighter. Last one I was driving was 1800 lbs.
I am getting older too, just turned 50, my vision isn’t what it was in my 20’s. So my night endurance racing suffers over what it was years ago.

What about you?
Dan

[72dan]

Originally Posted by roastbeef

is there a way to test and tweak this while the car is stationary? i can see a fun experiment being setting up the car on toe plates so there is no scrubbing and adding weight to each corner independently to see static results. i would imagine this rear steer simulation would yield the same result if the car was moving, right?

it would be cool to be able to test this without having to wait for a test and tune day to come up to get to the track. i mean... someone has their alignment specs somewhere- i doubt they have a non-disclosure agreement with their clients. lol

Way above my pay grade Roastbeef. I imagine the pro race teams put it all into autocad software and run computer simulations and a bunch of math and theory that Is above my head, then make their engineered parts.
Somehow they keep making cars faster.
My buddy just picked up a 2018 Porsche GT3 last week. Ok not an RS but still it will run with a Schirmer M3 no problem and he says it’s really comfortable on the street. No idea how the Porsche engineers pulled that off.

[M3 Number 86]

Originally Posted by 72dan

Once in a while, not enough. My suspension became a nightmare dragged out for almost a year. I ran a few NASA races last year in a tube frame car. Take out two stroke karts or a shifter kart once in a while. Tested a few other race cars.

I would like to have a dedicated track car but no space.
I will likely run a few endurance races this year renting a seat with a team.

It’s all about time and money...
I love my M3, yeah race suspension but it’s a steeet car. I bought it new w every option and it’s in excellent condition. I can’t gut it and cage it.
Also hard to put $100K into a 3500 lb street car to make it fast and lose my fun street car. After you start going out in tube frame cars under 2,000 lbs it’s like why bother with a production car.

Tires, brakes, everything lasts longer when the car is lighter. Last one I was driving was 1800 lbs.
I am getting older too, just turned 50, my vision isn’t what it was in my 20’s. So my night endurance racing suffers over what it was years ago.

What about you?
Dan

That's true. I'm always frustrated how heavy my pig is. But it's a fun dual purpose car for sure. We run in bimmer challenge with a lot of guys on here in fact. Dogbone won last year in his crazy build.

[roastbeef]

Originally Posted by 72dan

Way above my pay grade Roastbeef. I imagine the pro race teams put it all into autocad software and run computer simulations and a bunch of math and theory that Is above my head, then make their engineered parts.
Somehow they keep making cars faster.
My buddy just picked up a 2018 Porsche GT3 last week. Ok not an RS but still it will run with a Schirmer M3 no problem and he says it’s really comfortable on the street. No idea how the Porsche engineers pulled that off.

i have a friend that does high end CAD work in the automotive industry. he drafted the entire suspension of one of his classic cars just to see how much adjusting he would have to do. he has shown me some pretty incredible automotive stuff with cad.
there are some simulations that can be done in cad, but it is pretty rigid and doesn't account for bushing flex- at least not that i know of. so you can sort of do some animation/movement stuff, but i got the impression its more for display illustration rather than function testing.

[roastbeef]

here is another thing- if schirmer is using solid body-side bushings and flexable spindle-side bushings, it really wouldn't be very hard to replicate. my friend could draft an oem spindle-side bushing cup that is threaded to mate it to some SPL links. then we could press in some oem bushings (or whatever bushings we want). that would theoretically put all the toe pressure on the outer ends of the links and create the toe steer.
looking at the pic i found earlier and posted in here- it doesn't tell the whole story.

thoughts?

[72dan]

Originally Posted by roastbeef

here is another thing- if schirmer is using solid body-side bushings and flexable spindle-side bushings, it really wouldn't be very hard to replicate. my friend could draft an oem spindle-side bushing cup that is threaded to mate it to some SPL links. then we could press in some oem bushings (or whatever bushings we want). that would theoretically put all the toe pressure on the outer ends of the links and create the toe steer.
looking at the pic i found earlier and posted in here- it doesn't tell the whole story.

thoughts?

I don't know that they are using bushings, that is from the article in my original post, a system BMW designed for street cars like the 7 series with rear steering. I think they are all monoball, most race car stuff is.
I have all SPL monoball, aluminum subframe bushings, AST 5300's. I think the difference in the Schirmer is the rear lower control arm and maybe their own custom upright/spindle with different suspension connection points.
Look at the attached photos from my suspension. If you changed the connection points for the arms that are in front of and behind the axle shafts you change the angle of that arm, as arms move toward horizontal level they get longer as they angle away from horizontal length decreases.
Toe, camber and caster or thrust angle all change.
Whether or not you need a different upright or not I don't know, they may use spacers to change the connection points up/down or front/back on the upright.

I have been messing with shock pressure, built my own nitrogen system to charge shocks and tires. Had the car out tonight, got the snowflake icy road warning, that cold here but at least no more low tire pressure warnings. I put the tires at 32 psi nitrogen no more fluctuation with temperature. I went from 175 psi to 225 psi on the coilovers, a little stiffer and faster rebound. Sorry off track.

If your buddy can autocad it go for it. I don't know how to exactly measure the factory mounting points in 3d to enter into software.

Then how much angle on the rear? I was thinking about it, if right when you turn into a corner, let's say a right hand corner, if both the front wheels and both rear wheels all turned 0.5 or 1 degree to the right the whole car would move towards the apex with zero scrub but at some point the front tires need more angle than the rear tires to swivel the car or change the direction the car is pointed. I have no idea how many degrees the rears move.

How do we figure that out? Look at race track maps, figure out average radius of corners, then model the suspension so there is no scrub on the average radius corner?

[nigt3]

Just bought this car 6 weeks ago, heading to spa next month so be interesting to see how it goes on track!

[roastbeef]

she's a 'beaut. did you notice anything special or proprietary on it? any one-off suspension parts?

[nigt3]

Originally Posted by roastbeef

she's a 'beaut. did you notice anything special or proprietary on it? any one-off suspension parts?

Its got all his suspension parts, full kinematics, 3way Nitron’s etc

[StripclubDJ]

Originally Posted by nigt3

Its got all his suspension parts, full kinematics, 3way Nitron’s etc

Pics or you're lying

[nigt3]

Originally Posted by StripclubDJ

Pics or you're lying

I’m on holidays at the minute so can’t go out to the car, but here’s a pic from team Schirmer Instagram of when I had it at a charity cancer support car show a few weeks ago.


Team Schirmer ‘s done all the work to the car before my ownership, their full suspension and wheel setup, exhaust, brakes, cams etc, only thing missing is their full cage (only rear) something I’m going to see them about soon

[Alexand3r]

Is that AlexHardt's old M3? She is a thing of beauty!!

[nigt3]

Originally Posted by Alexand3r

Is that AlexHardt's old M3? She is a thing of beauty!!

Don’t think so, most of it’s life it was owned by guy called Phil Morrison, he got Schirmer to build it and also kept it there quite often, he done a Brocher on the car and it also featured in bmw car magazine

[Alexand3r]

My bad.. Just looked at it again and saw some details that are different..
Anyway, we will be waiting on the update of the feel of the car on the track!

[nigt3]

Dropped car off over winter to team Schirmer and got his cage and carbon parts fitted

[SupraSaiyan]

So awesome! Thanks for sharing

[Bruins97]

Originally Posted by nigt3

Dropped car off over winter to team Schirmer and got his cage and carbon parts fitted

You lucky, lucky man

[Epoustouflant]

She's a beauty!

Suspension pictures? 👀

[nigt3]

You’ll all be able to buy his pets online soon, Tom’s opened up an online shop for all his parts, think it goes live within 2weeks!!

[//steve\\]

Originally Posted by nigt3

You'll all be able to buy his pets online soon, Tom's opened up an online shop for all his parts, think it goes live within 2weeks!!

My gut says it's the normal parts, they aren't going to just sell any of the "secret sauce" stuff. Still cool but I have to imagine most of what they'll sell you can already get elsewhere.

[nigt3]

Originally Posted by //steve\\

My gut says it's the normal parts, they aren't going to just sell any of the "secret sauce" stuff. Still cool but I have to imagine most of what they'll sell you can already get elsewhere.

You could be right, time will tell!