e46 M3 suspension setup, or how to not downgrade your car with suspension mods

[Slideways]

Make sure to watch a lot of Shailh's videos on his channel, there is a lot to learn.

Here is a demo of gas shock pressure effect https://youtu.be/DOK-BvIORVQ

I will repeat what I have said before. When I did my dyno session with him on Ohlins strut/shock at his shop in Redwood City, we discovered that there is way too much pressure in them and the valving was way tight. Force vs velocity curves (he printed me a copy but I misplaced it somewhere) were close to straight lines, so he recommended to run both fronts and rears at full soft irrespective of spring rates. Not ideal but it would help counteract the initial pressure and smooth out curves. I run them at soft street/autox/track without any adjustments.

Flat ride is a simple concept, where hang time needs to be introduced in the front via lower frequency/softer spring (to react slower) so that once the front rolls over that bump it gives enough time for the wheelbase to travel over it and allow the rear to hit the same bump so that both front and rear settle back down "together". Depends on the wheelbase, weight distribution, etc. Running high frequency/stiff fronts makes the car pitchy, where the front is disconnected from the rear. So when you run over thebump, the front reacts and settles quickly, then the rear runs over the bump and settles independently. That is a much less comfortable/bouncy ride. Vs having front and rear settle at the same time.

If you don't need the car to transition fast like on an autox course, you can go much softer all the way around as long as you don't bottom out.

Just remember that springs impact front to rear comfort (flat ride vs pitch) while also the roll side to side. Swaybars only impact roll. You need all components to work together to get proper balance.

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For the R&T kit, it seems that Ohlins chose the high front spring rate to control body roll and have it work with the stock front sway bar. With a stiffer aftermarket front sway bar, the front springs don't have to control as much roll; therefore, a softer spring rate can be used.

[mrgizmo04]

For the R&T kit, it seems that Ohlins chose the high front spring rate to control body roll and have it work with the stock front sway bar. With a stiffer aftermarket front sway bar, the front springs don't have to control as much roll; therefore, a softer spring rate can be used.

Correct, most people don't understand that, and their r&t kit literally swaps out only the struts/shocks and springs. It assumes you change absolutely nothing else - top mounts, rsm, swaybars, etc. But noone selling coilover kits cares to incorporate your other setup and goals unless you call around. Like what swaybars you will run and how the car will be used.

Now Barry at 3dm and team are figuring out the next phase of their support for enthusiasts who have different camber plates (that somewhat started with the strut/knuckle spacer), how to offer different spring rates, what lengths, how that impacts droop/bump, how to make it work for various ride heights people want to run, what shims/spacers to include, etc.

Fun stuff.

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[cobra]

Make sure to watch a lot of Shailh's videos on his channel, there is a lot to learn.

Here is a demo of gas shock pressure effect https://youtu.be/DOK-BvIORVQ

I will repeat what I have said before. When I did my dyno session with him on Ohlins strut/shock at his shop in Redwood City, we discovered that there is way too much pressure in them and the valving was way tight. Force vs velocity curves (he printed me a copy but I misplaced it somewhere) were close to straight lines, so he recommended to run both fronts and rears at full soft irrespective of spring rates. Not ideal but it would help counteract the initial pressure and smooth out curves. I run them at soft street/autox/track without any adjustments.

Flat ride is a simple concept, where hang time needs to be introduced in the front via lower frequency/softer spring (to react slower) so that once the front rolls over that bump it gives enough time for the wheelbase to travel over it and allow the rear to hit the same bump so that both front and rear settle back down "together". Depends on the wheelbase, weight distribution, etc. Running high frequency/stiff fronts makes the car pitchy, where the front is disconnected from the rear. So when you run over thebump, the front reacts and settles quickly, then the rear runs over the bump and settles independently. That is a much less comfortable/bouncy ride. Vs having front and rear settle at the same time.

If you don't need the car to transition fast like on an autox course, you can go much softer all the way around as long as you don't bottom out.

Just remember that springs impact front to rear comfort (flat ride vs pitch) while also the roll side to side. Swaybars only impact roll. You need all components to work together to get proper balance.

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I disagree with the statements made about gas force in that video and his other one about the same topic.

Ohlins r&t require gas pressure to make compression force.

[fattycharged]

It's shit like this that would keep me away from FCM 😂


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[Cronenberged]

It's shit like this that would keep me away from FCM 😂


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Why? They do every tedious thing everyone is talking about.

[fattycharged]

Why? They do every tedious thing everyone is talking about.

it was my direct response, without clarifying, to his videos on YouTube...just not my style, but I get how and why some might click with his style.

Not my objection to his points, I realize that wasn't clear, at all.

[bigjae46]

Why? They do every tedious thing everyone is talking about.

Following his spreadsheet has resulted in nothing but transformative results.

My home track is shit and all of the braking zones are super bumpy while the rest of the track is just bumpy. It casually runs within 2-3 seconds of the NASA TT3 record despite bad driving and meh Toyo RRs. Flat ride found me over 4 seconds from a low 1:50 lap to high 1:45s.

At the smoother tracks, I’m pretty sure I could use more spring rate in the front. The one place where my car isn’t as good is on tracks with a lot of late apexes. There you really need that extra weight transfer to the rear tires to drive the car out.

[mrgizmo04]

I disagree with the statements made about gas force in that video and his other one about the same topic.

Ohlins r&t require gas pressure to make compression force.

What do you disagree with?

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[mrgizmo04]

it was my direct response, without clarifying, to his videos on YouTube...just not my style, but I get how and why some might click with his style.

Not my objection to his points, I realize that wasn't clear, at all.

Have you driven the setup for an extended period of time to experience the difference, or just philosophically not your style?

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[cobra]

What do you disagree with?

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The statement that the damper does not move until the gas force is overcome on every cycle of the shock.

[IamFODI]

The statement that the damper does not move until the gas force is overcome on every cycle of the shock.

Curious to hear more here

[fattycharged]

Have you driven the setup for an extended period of time to experience the difference, or just philosophically not your style?

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No, I have not.

I was merely being critical of the deliverer of information, his style of delivery, not the concept. In retrospect, I shouldn't have made the comment and it added nothing to the conversation, but I did, so here we are.

I'll be giving his concept a go myself, with a set of Ohlins I just ordered, though it sounds like the gas pressure “issue” will still be present.

His concepts make a lot of sense to most of us I'm sure, because “it just feels off”, that is something everyone who has been chasing the handling/comfort dragon for years has experienced, some of us on multiple platforms with not much success.

I totally understand trying to push a new way of thinking and way of doing things into a very established marketplace, even if what you're offering is much better than what currently exists, so I should be less critical.


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[fattycharged]

The statement that the damper does not move until the gas force is overcome on every cycle of the shock.

I replicated this experiment on a set of used MCS 1wnr after watching this video and I agree completely.

I don't see why he was straining so much to hit that 100lbs using his body weight.


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[cobra]

Curious to hear more here

I tried to make an simplified graph to explain it. This is what the spring force diagram would look like for a shock with a linear spring with no preload, and a gas pressure from the shock.

By pressing on the shock on a scale, you are fighting against the gas spring (which is very real and can take 100+lbs to overcome). But once you do overcome that force (such as the weight of the car), the only additional force required to move is from friction.

[IamFODI]

I tried to make an simplified graph to explain it. This is what the spring force diagram would look like for a shock with a linear spring with no preload, and a gas pressure from the shock.

By pressing on the shock on a scale, you are fighting against the gas spring (which is very real and can take 100+lbs to overcome). But once you do overcome that force (such as the weight of the car), the only additional force required to move is from friction.

Pretty much what I thought – i.e. the gas force "has to be overcome" in the same sense as a spring's force has to be overcome. So we could say the gas pressure functions like adding a bit of both rate and preload to the spring, all of which could be fully compensated by taking some of those out of the spring itself. Accurate?