How to upgrade suspension without compromising comfort

J.G.
Update by J.G. Pasterjak to the BMW 435i project car
May 14, 2024 | BMW, SCCA, Time Trials, 435i

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Maybe the single most tortured descriptor of cars in our world is “dual duty.” It’s typically used to describe a car that’s intended for both street and track, but in reality is typically optimized for one and rendered nearly unusable for the other.

And yeah, that kind of makes sense. After all, the keys to success through the Carl’s Jr. drive-thru …

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Comments
theruleslawyer
theruleslawyer Reader
5/14/24 9:28 a.m.

I think the scca tt classing achieves the opposite of the intended effect. Its a laundry list of what you need to do to compete in a class and not just a menu.

Maybe it tolerable at the lowest classes, but it still picks winners in classes as different cars respond differently to that list. At higher classing that list really explodes and it still suffers from the issue that a single mod can throw you into really rough classing super quick. 
 

SCCA tt classing seems to be more about attempting to attract their autocross audience to TT than anything. The prep levels are nearly identical and they support alternate classing eg ST cars in tuner. 
 

It is a weird choice too as most people seem to progress through hpde before reaching TT. While in hpde they learn than scca solo rules were not built with track in mind. I wish they had gone with a more track focused ruleset. Id be far more interested in competing under nasa or even gridlife if the series weren't so scattered geographically. 
 

But back to the main point- dual duty isn't that hard. It just requires pretty expensive dampers. The issue being that cheap ones are harsh at rates suitable for the track. Better dampers can manage high spring rates without that edge. 100% liked my Ohlins better than the stock suspension on my old m4. I've heard the same thing from owners of even more expensive dampers like mcs or jrz. The challenge is everyone wants to throw on a set of $1k bc coilovers and is surprised when they ride like ass. 

Keith Tanner
Keith Tanner GRM+ Memberand MegaDork
5/14/24 9:48 a.m.

How to upgrade suspension without compromising comfort?

Travel.

Don't just dump it, or use a two-piece coilover setup that has little overall shaft travel so you have to choose between compression and droop. Let the suspension move, and give it enough spring rate to keep it out of the bumpstops. And yes, spend the money on good dampers. Konis are a pretty solid choice at this level.

I would love to actually try this setup without the rose colored glasses, as I suspect ride quality has indeed been affected over rougher surfaces. The clue?

The overall result here is springs that have only a very slightly higher rate than stock, but they drop the rear of the car about 5/8 of an inch and the front by around ¾ of an inch

At least 5/8" of loss of wheel travel in bump, but no significant change in spring rate. That's not a recipe for success, and the article reads like it was heavily influenced by the vendor - all that stuff about wire thickness but no actual mention of spring rates. The method of increasing wire diameter, increasing the number of coils but decreasing the free length also has the side effect of making coil bind more likely. The car will be spending more time on the bumpstops but will hopefully be avoiding coil bind, as that's destructive to suspension components including the springs themselves.

The handling changes are likely mostly due to that alignment and not "cg optimization". It would be a telling test to install the camber plates and do the alignment without the spring and shock changes, and also with just the shocks.

 

Tom_Spangler (Forum Supporter)
Tom_Spangler (Forum Supporter) GRM+ Memberand UltimaDork
5/14/24 9:58 a.m.
Keith Tanner said:

the article reads like it was heavily influenced by the vendor

I mean... that's kind of how it works, right? No disrespect to GRM or the vendor, but these articles tend to be thinly-veiled advertisements most of the time. And I get it, I work in marketing, my company pays big money for "neutral" articles and longer form content that's absolutely intended to make us look good without being too obvious about it. It's just how the game is played, and kind always has been in enthusiast magazines.

theruleslawyer
theruleslawyer Reader
5/14/24 10:06 a.m.
Keith Tanner said:

The handling changes are likely mostly due to that alignment and not "cg optimization". It would be a telling test to install the camber plates and do the alignment without the spring and shock changes, and also with just the shocks.

I got plates on my M4 on stock suspension before coilovers and the alignment alone was huge for track. Granted a 435 has more to gain from stock spring rates, but still, huge difference. The stock non adjustable front factory camber is a travesty on BMWs.  Also FWIW if you're really looking to keep it streetable the Millway street camber plates are a much better choice. Instead of a monoball they have a delrin bushing on top and are dead silent. I never could get my vorshlags to stop chattering over rough roads. They are great track plates, but not the best dual use option if you care about NVH.

Keith Tanner
Keith Tanner GRM+ Memberand MegaDork
5/14/24 10:18 a.m.
Tom_Spangler (Forum Supporter) said:
Keith Tanner said:

the article reads like it was heavily influenced by the vendor

I mean... that's kind of how it works, right? No disrespect to GRM or the vendor, but these articles tend to be thinly-veiled advertisements most of the time. And I get it, I work in marketing, my company pays big money for "neutral" articles and longer form content that's absolutely intended to make us look good without being too obvious about it. It's just how the game is played, and kind always has been in enthusiast magazines.

Not always. Years ago, GRM tested one of our big brake kits and did not exactly give it a glowing review because of what it did to brake bias (something we have addressed in all our kits in the decades since). It's one of the reasons why I'm a fan of theirs, because they were right. And it's why I want better from them instead of weak advertorial. It's worst with the newer cars like this BMW, less of an issue for things like Tom's mutant Miata.

Our company doesn't pay for articles anywhere, although we do sometimes provide free product to someone we think will give them good visibility. It's no coincidence there are so many pictures of Andy's triple thread car on our wheels ;) But they're good wheels!

JG Pasterjak
JG Pasterjak Production/Art Director
5/14/24 10:18 a.m.
Keith Tanner said:

How to upgrade suspension without compromising comfort?

Travel.

Don't just dump it, or use a two-piece coilover setup that has little overall shaft travel so you have to choose between compression and droop. Let the suspension move, and give it enough spring rate to keep it out of the bumpstops. And yes, spend the money on good dampers. Konis are a pretty solid choice at this level.

I would love to actually try this setup without the rose colored glasses, as I suspect ride quality has indeed been affected over rougher surfaces. The clue?

The overall result here is springs that have only a very slightly higher rate than stock, but they drop the rear of the car about 5/8 of an inch and the front by around ¾ of an inch

At least 5/8" of loss of wheel travel in bump, but no significant change in spring rate. That's not a recipe for success, and the article reads like it was heavily influenced by the vendor - all that stuff about wire thickness but no actual mention of spring rates. The method of increasing wire diameter, increasing the number of coils but decreasing the free length also has the side effect of making coil bind more likely. The car will be spending more time on the bumpstops but will hopefully be avoiding coil bind, as that's destructive to suspension components including the springs themselves.

The handling changes are likely mostly due to that alignment and not "cg optimization". It would be a telling test to install the camber plates and do the alignment without the spring and shock changes, and also with just the shocks.

 

Also remember that when it comes to ride height reductions for street cars that we exist in a fairly idealized world where the road are smooth and the hills are theoretical. One thing I liked about the lowering with the Eibachs is it was minor enough to still allow the car to function 100% as it had before in regards to daily use. The car can still go on the trailer without the use of supplemental ramps, and I've not once chosen not to drive it because it's too harsh. 

So we're in a fortunate situation where we can afford to sacrifice a bit of travel and never notice the ill effects and just feel the benefits.

JG Pasterjak
JG Pasterjak Production/Art Director
5/14/24 10:24 a.m.
theruleslawyer said:

I think the scca tt classing achieves the opposite of the intended effect. Its a laundry list of what you need to do to compete in a class and not just a menu.

Maybe it tolerable at the lowest classes, but it still picks winners in classes as different cars respond differently to that list. At higher classing that list really explodes and it still suffers from the issue that a single mod can throw you into really rough classing super quick. 
 

SCCA tt classing seems to be more about attempting to attract their autocross audience to TT than anything. The prep levels are nearly identical and they support alternate classing eg ST cars in tuner. 
 

It is a weird choice too as most people seem to progress through hpde before reaching TT. While in hpde they learn than scca solo rules were not built with track in mind. I wish they had gone with a more track focused ruleset. Id be far more interested in competing under nasa or even gridlife if the series weren't so scattered geographically. 
 

But back to the main point- dual duty isn't that hard. It just requires pretty expensive dampers. The issue being that cheap ones are harsh at rates suitable for the track. Better dampers can manage high spring rates without that edge. 100% liked my Ohlins better than the stock suspension on my old m4. I've heard the same thing from owners of even more expensive dampers like mcs or jrz. The challenge is everyone wants to throw on a set of $1k bc coilovers and is surprised when they ride like ass. 

I mean, it is a menu because you can choose to not do any of the mods available to you. There's also plenty of variety available within those choices. 

The reality is that any ruleset that applies the same allowances to different cars is not about creating parity, it's about creating accessibility. The only way to create parity is with specific allowances for specific platforms, and ain't no one in the club TT sphere willing to take on that ball of snakes. Some folks think the NASA format solves it, but all it really does is moves the window toward hyperspecialization and away from any pretense of daily drivability.

JG Pasterjak
JG Pasterjak Production/Art Director
5/14/24 10:27 a.m.
theruleslawyer said:
Keith Tanner said:

The handling changes are likely mostly due to that alignment and not "cg optimization". It would be a telling test to install the camber plates and do the alignment without the spring and shock changes, and also with just the shocks.

I got plates on my M4 on stock suspension before coilovers and the alignment alone was huge for track. Granted a 435 has more to gain from stock spring rates, but still, huge difference. The stock non adjustable front factory camber is a travesty on BMWs.  Also FWIW if you're really looking to keep it streetable the Millway street camber plates are a much better choice. Instead of a monoball they have a delrin bushing on top and are dead silent. I never could get my vorshlags to stop chattering over rough roads. They are great track plates, but not the best dual use option if you care about NVH.

I was skeptical that the Vorshlag plates would be clank-free forever, but so far, so good. After a couple track sessions I jacked up each corner and tightened them down again just to put myself at ease after a good shakedown, and they're still quiet enough that a civilian in the car might not even notice a difference on the road riding as a passenger. Will this be the same 10,000 in? We'll see. but so far I'm not complaining.

JG Pasterjak
JG Pasterjak Production/Art Director
5/14/24 10:28 a.m.
Tom_Spangler (Forum Supporter) said:
Keith Tanner said:

the article reads like it was heavily influenced by the vendor

I mean... that's kind of how it works, right? No disrespect to GRM or the vendor, but these articles tend to be thinly-veiled advertisements most of the time. And I get it, I work in marketing, my company pays big money for "neutral" articles and longer form content that's absolutely intended to make us look good without being too obvious about it. It's just how the game is played, and kind always has been in enthusiast magazines.

Bro Eibach didn't even buy an ad in that issue so if that's how the game is played I guess we kind of suck at it.

Tom Suddard
Tom Suddard GRM+ Memberand Publisher
5/14/24 10:31 a.m.

FWIW, we don't do paid content unless it's VERY clearly disclosed. And I'd like to think that if you read through our stuff, you'll find a good bit more editorial integrity than any of our competitors. At least, I hope you do, because it's not uncommon for manufacturers to call and complain that we weren't nice enough when we publish our honest feedback.

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