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. …
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.
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.
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.
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.
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!
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.
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.
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.
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.
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.
In reply to Keith Tanner :
And it goes both ways. Since getting the Miata back on the road a few years ago, I have bought parts from Flyin’ Miata plus others in the biz.
Please know I'm not impugning your editorial integrity. But when you are putting something like this together, you need an expert, and those folks tend to work for the aftermarket companies that serve the market for whatever car you're talking about. And those experts are naturally going to promote the products that their company sells. If you talk to Terry Fair, he's going to say Vorshlag solutions are best, for instance.
Now, I may have made a leap based on my own experience in marketing and assumed that these articles were sponsored content of some kind or another. Which, again, I have no problem with. But it seems that's not the case, so I apologize for making that assumption.
In reply to theruleslawyer :
Same with my Vorshlags on the 235. A little chattery, especially noticable at low speeds, like driving through my neighborhood...
But I can get -4*, so I'm not bitching! (We're all so broken)
RacerBowie said:In reply to theruleslawyer :
Same with my Vorshlags on the 235. A little chattery, especially noticable at low speeds, like driving through my neighborhood...
But I can get -4*, so I'm not bitching! (We're all so broken)
How long have you had them on there?
Honestly I'm not even going to complain about a tiny bit of clicking, because that's the price of metal on metal and I'm willing to accept that. But I've been pleasantly impressed so far that they've been so silent.
In reply to JG Pasterjak :
Probably depends on your road quality as to how livable the noise is. Im in Chicago and compared to Florida our roads are a warzone of potholes and expansion joints. Smoother sections of road, no big deal.
theruleslawyer said:In reply to JG Pasterjak :
Probably depends on your road quality as to how livable the noise is. Im in Chicago and compared to Florida our roads are a warzone of potholes and expansion joints. Smoother sections of road, no big deal.
Yeah i'm fully willing to admit that this story hits different for anyone living north of central Kentucky.
Then again, you get to live in a big city with pro sports and entertainment and amazing food and we get to chase alligators out of our yards occasionally, so it kind of balances out.
I would expect clicking noises on spherical balls to be insufficiently specified components. We use sphericals in one of our top mount applications and learned very quickly that they need to be very good ones to deal with the axial pounding. Clicking/rattling is the sound of a worn out bearing. Get the spec right and they're good for years.
JG, if you can get away with a lower ride height and a stock spring rate because your roads are super-smooth, that's worth a mention in the article. I'm guessing the FIRM has fairly gentle berms on it as well, as that's another place that having travel helps out. Will this car be as fun to drive in PA or on a track with aggressive kerbing? When we develop suspension products, we have to test as many environments and situations as we can, as road conditions vary as much as our customers do.
Nothing wrong with asking experts who are in the industry for information. Those experts should be able to explain why the recommended products are the best, though. The discussion of the special nut for the Koni shocks on those camber plates, for example. Good stuff there, we know about the challenges, the design choices and the solution. If I were looking for a similar product, I'd now be taking this information into consideration and it would probably help me select a better part.
The springs, though. It's more traditional to specify spring rates instead of the percentage of wire thickness change - especially when the number of coils are also changed, making it an irrelevant number. Sounds very technical but is useless, which is a sign of marketingspeak. It's implied that keeping the stock spring rate is desirable when lowering a car, when it is not. GRM has had some trouble with their suspension articles for BMWs, it may be a market that is more interested in low than speed or they don't have access to a good subject matter expert.
I'm probably coming across as harsh here, but it's only because I hold GRM to a high standard and I felt this article was weak by comparison to the usual.
Keith Tanner said:GRM has had some trouble with their suspension articles for BMWs, it may be a market that is more interested in low than speed or they don't have access to a good subject matter expert
In my experience for F chassis bmws springs are heavily focused as an appearance product. They all just want to know about eliminating wheel gap. If you're lucky they consider if the drop works with stock damper length. Performance is a distant 3rd. People who care usually are shopping coilovers. Thats not to say there aren't people who care or you can't make improvements with springs. Just low and flush is generally the objective.
We always talk about suspension travel. Can we quantify that in some way? I realize it's going to be different based on car, but how much we talking about?
As much as you can get, really. We have something like 7.5" of travel in the rear of our high end ND Miata suspension, and the press reviews of that stuff have been superlative.
The big thing is the balance between spring rate and travel, particularly compression (bump) travel. You need enough spring rate to keep you off the bumpstops as much as possible, as bumpstops aren't a comfortable place to be and will also lead to abrupt handling changes. So when you take away compression travel by lowering the car, you need to raise the spring rate accordingly. In our NA/NB Miata application, that means nearly doubling the stock rate with our springs which will lower the car roughly 1". I say roughly as the stock height of an NA Miata varied quite a bit, and the final ride height with our springs is consistent. And those springs are regarded as having a very good ride quality for a performance spring despite that spring rate, when in fact it's because of that spring rate.
Can you come up with a rule of thumb that decreasing bump travel by 50% means you need 100% more spring rate? I suspect so but I've never mathed it out specifically. It seems like it should work that way, the suspension would only move half as far on a given bump. But there may be an exponent in there I'm neglecting. I should check.
In reply to Keith Tanner :
You also generally need to increase spring rate over and above that because the roll center will drop faster than the center of gravity*, so a lowered car will tend to roll more.
IMO body roll isn't a negative as long as it is controlled and it doesn't result in running out of travel, but this relates directly to that second point.
*unless you have a solid axle, which tends to do the opposite, so lowering will prefer a much softer spring. Not that anybody built a sporting car with a solid axle lately.
So while I would love to discuss how Tom is getting fabulously wealthy on product endorsements I'd rather talk about the concept behind this.
I bought my Foxbody Mustang clearly with dual duty in mind.
Today my new front springs arrived; the current springs have the car two low. I may also raise the rear slightly (the spring perches in back are height adjustable) as I feel it's to close to the bump stops.
I already have Koni dampers and camber plates. Currently the car rides like crap on rough roads......mostly the front.
Why do you use positive toe in at the rear? You shouldn't need the understeer from the toe with the -3 deg camber.
My daughter's M440i cabrolet has the factory rear alignment of 6' toe in with -1.35 camber. The rear tires lasted about 10,000 miles so she gets a new pair at each oil change. After the first pair, she got an alignment at the dealer. They INCREASED the toe to 12'. I suggested getting it aligned to zero rear toe. She said no, that's not the BMW specification.
C R Hammond
In reply to rhammond :
Positive toe / toe in for the rear combats power oversteer.
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