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Swaybar stiffness. Such thing as too stiff?

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Swaybar stiffness. Such thing as too stiff?

 
Old 03-23-2019, 09:21 PM
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Default Swaybar stiffness. Such thing as too stiff?

Hey guys. Recently been pondering this. I haven’t really seen this being this discussed, so hoping to look for clarification here.

To my understanding, you want to go as stiff as possible for coilover spring-rate, as long as the damping can handle it, and it can still properly absorb bumps. However, is there a limit to how stiff you can go with sway bars? Does going too stiff limit the ability of the coilovers to soak up bumps?

Currently on stock ohlins dfvs, 245 rs4 non-staggered, with Karcepts front bar on medium setting, and 00’ ap1 rear sway (car is an ap2). Car handles great. What got me curious though, it seems like a decent amount of people are running Miata rear sways, and aftermarket options also seem to be low-stiffness.
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Old 03-24-2019, 01:23 AM
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Your car is setup for a lot of understeer. If you don't feel it your not going fast enough.
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Old 03-24-2019, 06:32 AM
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At some point you will lose compliance and lift tires off the ground, which is obviously not good for traction. The reason for the stiff front bar normally used on the s2000 is to counteract rear wheel lift and to make the vehicle handle more neutral with a square setup. This is something that the AutoX people use because the B/C street category only allows changing of one bar. People change to the softer Miata bars to combat snap oversteer and again with a square setup would help to make the car more neutral again. You have added front grip by going square and this would cause the car to oversteer worse. I have the Karcepts .25 bar and started on max and really wondered what the heck was up with how badly it handled. It horribly understeered, so I would just throw it into the corners to get rotation and would just end up spinning out. I want to get the Karcepts rear bar to soften it, so I could also soften the front a bit more. Currently have it on the middle setting and seems to handle great now!
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Old 03-24-2019, 09:07 AM
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Originally Posted by roel03 View Post
Your car is setup for a lot of understeer. If you don't feel it your not going fast enough.
You are mistaken. At my local track I have not seen a faster lap time by an na s2000 on street tires (been at least 50 times), and cars in general that are posting faster times are usually race cars or really fast production cars.

Setup has been great for me. It is borderline oversteer at mid/low speeds. It is one turn on the ohlins adjustment knob away from being neutral-handling.
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Old 03-24-2019, 09:10 AM
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Originally Posted by BoboTheMonkey View Post
At some point you will lose compliance and lift tires off the ground, which is obviously not good for traction. The reason for the stiff front bar normally used on the s2000 is to counteract rear wheel lift and to make the vehicle handle more neutral with a square setup. This is something that the AutoX people use because the B/C street category only allows changing of one bar. People change to the softer Miata bars to combat snap oversteer and again with a square setup would help to make the car more neutral again. You have added front grip by going square and this would cause the car to oversteer worse. I have the Karcepts .25 bar and started on max and really wondered what the heck was up with how badly it handled. It horribly understeered, so I would just throw it into the corners to get rotation and would just end up spinning out. I want to get the Karcepts rear bar to soften it, so I could also soften the front a bit more. Currently have it on the middle setting and seems to handle great now!
I see, that makes a lot of sense. Thanks for the input.
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Old 03-24-2019, 10:18 AM
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Going square induces far more understeer than stock. Therefore, you want to stiffen the front and soften the rear. You have done so with the front bar. Now, change the rear bar to an '04 or later, and you'll notice the handling shift towards neutral immediately.
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Old 03-24-2019, 11:28 AM
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Originally Posted by davidc1 View Post
Going square induces far more understeer than stock. Therefore, you want to stiffen the front and soften the rear. You have done so with the front bar. Now, change the rear bar to an '04 or later, and you'll notice the handling shift towards neutral immediately.
Wait..what? Square means bigger front tire, which means more front grip, therefore introducing more oversteer providing no other changes are made.

The suspension setup changes you recommended are for a setup that is oversteering.

My setup is borderline oversteer, one click on ohlins away from neutral.
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Old 03-24-2019, 01:10 PM
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You didn't say where. On the street? At track days? In Autocrosses? Each has different criteria.

For example, competitive competition classes have rules, where w2w or not. Street autocross classes can't lower the car, must use OEM springs, can't use offset ball joints limiting front camber to -1.9°. STR limits rims to 9" width, tires to 255. Can't use metal bushings. The negative camber that would be optimal on track would cause excessive tread wear on the street.

For track cars, that is often the most important criteria with enough other cars running to establish what is the best practice.

For street cars, a driver will never be at continuous maximum lateral forces. First, there are few street turns tight enough and fast enough to be at the limit. Second, if you are at the limit all the time, eventually you go past it, with really bad outcomes on the street. Third, on the street there are oncoming cars, pedestrians, police, and the assumption you stay in your own lane. So feel is much more important. The Mazda Miata is widely praised but runs on narrow tires with a fairly soft suspension.

That stiff front bar makes it seem more responsive on the street from my personal experience.

On the track, the combination of springs, bars, and shocks will depend on the track surface, the track shape, speeds involved, and aerodynamics. Generally less stiff adds more mechanical grip and more aero needs stiffer springs. With the short wheelbase, many have found they went to stiffer springs to control pitch (e.g. brake dive) and roll, requiring less from the anti-roll bars.

If you search the threads here you will find cars running competitively in SCCA E/Production and T3, and NASA TT3, TT4, and TT5. In autocross SCCA A/Street (well, there used to be A/Street CRs), B/Street, STR, and DSM (with 315/30 Hoosier A7 tires). Plus large numbers of owners running track days. You could PM them for their specific recommendations.
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Old 03-24-2019, 09:50 PM
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Originally Posted by DavidNJ View Post
You didn't say where. On the street? At track days? In Autocrosses? Each has different criteria.

For example, competitive competition classes have rules, where w2w or not. Street autocross classes can't lower the car, must use OEM springs, can't use offset ball joints limiting front camber to -1.9°. STR limits rims to 9" width, tires to 255. Can't use metal bushings. The negative camber that would be optimal on track would cause excessive tread wear on the street.

For track cars, that is often the most important criteria with enough other cars running to establish what is the best practice.

For street cars, a driver will never be at continuous maximum lateral forces. First, there are few street turns tight enough and fast enough to be at the limit. Second, if you are at the limit all the time, eventually you go past it, with really bad outcomes on the street. Third, on the street there are oncoming cars, pedestrians, police, and the assumption you stay in your own lane. So feel is much more important. The Mazda Miata is widely praised but runs on narrow tires with a fairly soft suspension.

That stiff front bar makes it seem more responsive on the street from my personal experience.

On the track, the combination of springs, bars, and shocks will depend on the track surface, the track shape, speeds involved, and aerodynamics. Generally less stiff adds more mechanical grip and more aero needs stiffer springs. With the short wheelbase, many have found they went to stiffer springs to control pitch (e.g. brake dive) and roll, requiring less from the anti-roll bars.

If you search the threads here you will find cars running competitively in SCCA E/Production and T3, and NASA TT3, TT4, and TT5. In autocross SCCA A/Street (well, there used to be A/Street CRs), B/Street, STR, and DSM (with 315/30 Hoosier A7 tires). Plus large numbers of owners running track days. You could PM them for their specific recommendations.
Hey David, thanks for the response. I guess my original post was pretty vague. Car mostly sees track duty. Car handles great, but in the process of moving up in spring rate a bit to improve on body roll and brake dive. Was just curious if it was a good idea to get a stiffer aftermarket rear bar and move up in swaybar stiffness equally in front and rear, but that is probably a bad idea because of mechanical grip, as the 00’ ap1 rear bar with the karcepts front bar are a pretty stiff combo.
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Old 03-25-2019, 06:22 AM
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Originally Posted by kt411gcn View Post
Hey guys. Recently been pondering this. I haven’t really seen this being this discussed, so hoping to look for clarification here.

To my understanding, you want to go as stiff as possible for coilover spring-rate, as long as the damping can handle it, and it can still properly absorb bumps. However, is there a limit to how stiff you can go with sway bars? Does going too stiff limit the ability of the coilovers to soak up bumps?

Currently on stock ohlins dfvs, 245 rs4 non-staggered, with Karcepts front bar on medium setting, and 00’ ap1 rear sway (car is an ap2). Car handles great. What got me curious though, it seems like a decent amount of people are running Miata rear sways, and aftermarket options also seem to be low-stiffness.
Its a bit of a general question, so here is a general answer as I understand it:
Yes, you can have too much spring rate in your ASB. Generally speaking you want as little spring rate as possible without running out of travel regardless if it’s from your ASB or coil springs. Caveats are running more spring rate to make your aero function better and most people find it easier to drive a car with a little more spring rate.
ASBs are springs. If you go to stiff you will over power a shock not designed for it just like you would buying a stiffer coil spring.
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