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New Sway Bar Option and Sway Bar Summary

Old 01-26-2013, 09:56 PM
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Originally Posted by HiFlite999 View Post
Rest of my weekend is full of movie events and cute actresses ...
Now there's a topic more interesting. Picts or GTFO.
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Old 01-27-2013, 11:54 AM
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Originally Posted by TeamRX8 View Post
thanks for starting a new thread on an old subject rather than just adding it on so all the misinformed n00bs can have a place to play
Oh you're so welcome. The old threads are scattered all over in both time and in different forums. One could hypothesize that getting by getting post 1 into reasonable shape to the point RIWWP could refer to it, it would cut down on the number of noob same-question threads.

Or not.
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Old 01-28-2013, 08:31 PM
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Originally Posted by blu3dragon View Post
Following on from above, a 28.58mm bar with a 4.783 wall gives a raw rate of 1762.7, which is almost exactly the same as the 27mm whiteline bar and 1.58x stiffer than stock.

Assuming this is correct, then this is the bar I need :-)
At this point, that seems like a big assumption to make though!
The weight with better scales is 9.1 +/- 0.15 lbs, which is more consistent with a .25" wall.

Your info emails on the PT RX-8 bar are inconsistent with previous info on that bar: 1 1/4" diameter, and 1/4 inch wall. One source: https://www.rx8club.com/wheels-tires...y-bars-109096/

another: Progress Technologies RX8 FRONT AntiSway Bar. for RX8 2004-2011

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Old 01-29-2013, 11:31 AM
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Originally Posted by HiFlite999 View Post
The weight with better scales is 9.1 +/- 0.15 lbs, which is more consistent with a .25" wall.

Your info emails on the PT RX-8 bar are inconsistent with previous info on that bar: 1 1/4" diameter, and 1/4 inch wall. One source: https://www.rx8club.com/wheels-tires...y-bars-109096/

another: Progress Technologies RX8 FRONT AntiSway Bar. for RX8 2004-2011

Hmm, thanks for the more precise weight. That's still a little bit lighter than what I would expect for a 0.25" wall, but I agree it is now close to that.

Actually knowing it is in the range of 3/16" to 1/4" is perhaps good enough. The 1/4" wall will only be ~12% stiffer than the 3/16" wall.
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Old 02-18-2013, 08:55 AM
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Well, thanks to the data from HiFlite I decided to order the PT miata front bar as combined with the adjustments it should be close enough for my needs. If there is any way to actaully measure the stiffness when it is on the car I'm all ears.
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Old 02-19-2013, 11:52 AM
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Originally Posted by Charles R. Hill View Post
Not in any way that would be objective or not subject to many variables.
Thanks, I had some crazy ideas about jacking up one side of the car while on some scales, but I don't have easy access to any scales anyway. I think I'll just try driving it, see how I like the balance, and then adjust from there.
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Old 06-19-2013, 02:19 PM
  #32  
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So this thread turned me on to the FCM calculator and I guess I have a couple of questions for the more experienced.



So above is a snippet of my results, and there are a few things that make me . So reading some of their resources on the value each of those columns has, I was focusing a bit on the bounce frequency.

They mention that higher bounce frequencies can induce worse traction on the road when hitting bumps and that ideally, for a non-dedicated race vehicle, you want the frequencies to be about 1.8. Now my question is, how exactly does damping come into play? For example, we can see that my bounce frequency on the front is "high", now can that not be compensated for by increasing damping on the coilover, and furthermore, is that what one would ideally do to balance my setup more?

Also, how would one simulate running no rear bar? Putting a 0 in the rear sway size throws some of the numbers out of whack, whereas putting a 1 in the sway diameter and thickness seems to make more sense.
Attached Thumbnails New Sway Bar Option and Sway Bar Summary-untitled.png  
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Old 07-10-2013, 05:11 PM
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Originally Posted by paimon.soror View Post
They mention that higher bounce frequencies can induce worse traction on the road when hitting bumps and that ideally, for a non-dedicated race vehicle, you want the frequencies to be about 1.8. Now my question is, how exactly does damping come into play? For example, we can see that my bounce frequency on the front is "high", now can that not be compensated for by increasing damping on the coilover, and furthermore, is that what one would ideally do to balance my setup more?

Also, how would one simulate running no rear bar? Putting a 0 in the rear sway size throws some of the numbers out of whack, whereas putting a 1 in the sway diameter and thickness seems to make more sense.
Hmm, bounce frequency is a measure of how stiffly spring the car is. For a track or autocross car, you want to be up around 2.3-2.5Hz. That's not going to be too comfortable on the street. I think the 1.8 figure is basically seen as a good compromise between street comfort and performance. You also want the rear to be slightly higher frequency than the front (5-10%) so when you hit a bump, both ends of the car land at the same time (the faster rear catches up with the slower front). When setting the front to rear spring rate ratio though you also affect the balance of the car. So, if you change this, you need to change the sway bars to compensate.

Yes, if the damping is correct then it will help keep the tire in contact with the road.

On the sway bar settings, putting 0 in seems to work for me.
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Old 07-10-2013, 06:01 PM
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I've since started using the NC calculator. It is a little more flexible and you can edit all the fields to input the RX8 values.

Attached Thumbnails New Sway Bar Option and Sway Bar Summary-rx8_fcm_suspension_calcs.png  
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Old 07-11-2013, 07:53 AM
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That calculator looks great blu3dragon. Is it available to the public?

I did not see wheelbase in the calculator though, and I think this will affect the ratio bounce frequency. The wheelbase will also affect the pitch frequency, but that isn't listed on your spreadsheet.

Do you mind sharing the equation that provides the ratio bounce frequency?
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Old 07-11-2013, 08:04 AM
  #36  
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Thanks for the info blu3. I will check out the NC calculator and report results.

JCrane: FRC_NC.xls
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Old 07-11-2013, 09:09 AM
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Ok so here is my results with the NC sheet and after realizing how to put in solid bar data. Setup 1 is what i run daily, and what i run at autocross. Setup 2 is what I would have if I threw on 8K in the rear. I have a set of 8K swift springs sitting in my garage which is why i put that data there, just for comparison.
Attached Thumbnails New Sway Bar Option and Sway Bar Summary-untitled.png  

Last edited by paimon.soror; 07-11-2013 at 09:15 AM.
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Old 07-11-2013, 11:18 AM
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Originally Posted by JCrane82 View Post
That calculator looks great blu3dragon. Is it available to the public?

I did not see wheelbase in the calculator though, and I think this will affect the ratio bounce frequency. The wheelbase will also affect the pitch frequency, but that isn't listed on your spreadsheet.

Do you mind sharing the equation that provides the ratio bounce frequency?
The ratio bounce frequency is simply (rear bounce freq/front bounce freq). Wheelbase does not change that, but wheelbase and speed will change the way the car pitches over bumps. I have not done the math on the rx8, but ~10% higher rear frequency (so a bounce ratio frequency of 1.1) is a good ballpark to aim for, with any thing in the 5-15% (1.05 to 1.15 BRF) range acceptable. This is for ride, for racecar, then you are more concerned with front to rear roll couple (FRC) to get the balance right.
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Old 07-11-2013, 11:27 AM
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Originally Posted by paimon.soror View Post
Ok so here is my results with the NC sheet and after realizing how to put in solid bar data. Setup 1 is what i run daily, and what i run at autocross. Setup 2 is what I would have if I threw on 8K in the rear. I have a set of 8K swift springs sitting in my garage which is why i put that data there, just for comparison.
Thanks for sharing. How do you find the balance with your current setup?

What bump stops are you using - are the bump stop rates you used correct?

I'm going to try and dial my balance (FRC) in this weekend which will be the first time I drive on track with coilovers and sway bars.
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Old 07-11-2013, 11:50 AM
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Originally Posted by blu3dragon View Post
Thanks for sharing. How do you find the balance with your current setup?

What bump stops are you using - are the bump stop rates you used correct?

I'm going to try and dial my balance (FRC) in this weekend which will be the first time I drive on track with coilovers and sway bars.
I actually used to have 8K/6K on my stance coilovers, but then at the advice of another member who autocrosses their 8 a lot, i bumped up to 11K and left the 6K in the rear. It gave me an insane boost in confidence on the track and after about 4 clicks up from full soft and a disconnect of the rear bar, I started really putting down my best times (my definition of 'best times' is my delta from the first place finish in my class, they are generally the same group of guys).

I am not too sure what to put down for bump stop. I am using the ones that came with stance coilovers. I can't seem to find any data about their size or rate online.

2 questions:

1. based on what you were saying about about the bounce freq.... if i wanted more street comfort, I would be using the 11K/8K setup, and for a more aggresive track setup, I would stick with the 11K/6K?

2. Any idea what the front arm measurement would be on a swaybar on full soft?

edit: *derp* just noticed you had the full soft measurement above
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Old 07-11-2013, 12:06 PM
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Hrmm, interestingly enough, it looks like I should keep my rear bar on and my front on the softest hole as it will put my FRC closer to 69%? I am reading through the FCM tutorial and it comments on how a AutoX Miata shoots for about 65%

And even lower if you go with the MX5 Bar in the front, while keeping the PT rear bar.
Attached Thumbnails New Sway Bar Option and Sway Bar Summary-untitled.png  

Last edited by paimon.soror; 07-11-2013 at 12:12 PM.
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Old 07-11-2013, 12:53 PM
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^So you are thinking 69% FRC since the RX8 has more power than the miata? I was actually aiming for 66% expecting that to give me slight understeer at the limit (the first row in my screenshot is my starting point this weekend...).

It is likely your bump stops are stiffer than 100 lbs/in since those are the softest ones FCM have. Stiffer bump stops will bring that FRC down. Given your experience and the unknown here, I would just use the spreadsheet as a guide to increase or lower FRC based on whether you want more front or rear grip.

In theory, you want to set the springs right first, and then tune FRC with the sway bars (and finally bump stops). So, I'd expect the stiffer 11k/8k setup to be better for racing/AX as long as the shocks can control those stiffer springs. If I were you I would try that, along with bars to keep the FRC where it works for you (11k/8k with the PT miata front bar and no rear bar should give you similar balance/FRC to your current setup) [EDIT: I meant miata front bar on softest setting. Stiffer bars reduce grip over mid corner bumps, so softer bars with stiffer springs is better for handling than softer springs with stiffer bars]

On your other question, I would expect the stiffer rear springs will have more effect on ride than the improved bounce frequency ratio. No way to know without trying it though

And yes, I measured (well more eyeballed) my front sway bar holes to be 15mm apart, with the furthest hole giving an arm length of ~200mm (leading me to trust Shaikh's 187mm measurement for the middle hole)

Last edited by blu3dragon; 07-11-2013 at 01:01 PM.
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Old 07-11-2013, 01:05 PM
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Originally Posted by blu3dragon View Post
^So you are thinking 69% FRC since the RX8 has more power than the miata? I was actually aiming for 66% expecting that to give me slight understeer at the limit (the first row in my screenshot is my starting point this weekend...).
Well I only mentioned 69 because it was the lowest I could go, for "free" lol.
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Old 07-11-2013, 01:14 PM
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Originally Posted by blu3dragon View Post
It is likely your bump stops are stiffer than 100 lbs/in since those are the softest ones FCM have. Stiffer bump stops will bring that FRC down. Given your experience and the unknown here, I would just use the spreadsheet as a guide to increase or lower FRC based on whether you want more front or rear grip.

In theory, you want to set the springs right first, and then tune FRC with the sway bars (and finally bump stops). So, I'd expect the stiffer 11k/8k setup to be better for racing/AX as long as the shocks can control those stiffer springs. If I were you I would try that, along with bars to keep the FRC where it works for you (11k/8k with the PT miata front bar and no rear bar should give you similar balance/FRC to your current setup) [EDIT: I meant miata front bar on softest setting. Stiffer bars reduce grip over mid corner bumps, so softer bars with stiffer springs is better for handling than softer springs with stiffer bars]
So here is what would happen with:

Front bar on full soft
Rear bar on full soft
11K front
8K rear
200mm bump stops (set arbitrarily, only affects the last column)
Attached Thumbnails New Sway Bar Option and Sway Bar Summary-untitled.png  
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Old 07-11-2013, 01:18 PM
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^Unless you have a lot of understeer right now, I would guess you are going to get too much oversteer going that far! However, front bar on medium, or hard, with rear bar on soft will probably work well.
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Old 07-11-2013, 01:36 PM
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Originally Posted by blu3dragon View Post
^Unless you have a lot of understeer right now, I would guess you are going to get too much oversteer going that far! However, front bar on medium, or hard, with rear bar on soft will probably work well.
Same as above with front bar on medium
Attached Thumbnails New Sway Bar Option and Sway Bar Summary-untitled.png  
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Old 07-11-2013, 04:33 PM
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Originally Posted by paimon.soror View Post
Thanks for the info blu3. I will check out the NC calculator and report results.

JCrane: FRC_NC.xls

This only gives me an imbedded spreadsheet in html format. Do you have an excel file?
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Old 07-11-2013, 04:57 PM
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Originally Posted by JCrane82 View Post
This only gives me an imbedded spreadsheet in html format. Do you have an excel file?
Nope, I am just using it in a browser and then "saving" my work via a screenshot.
The spreadsheet is created and owned by Fatcat Motorsports.
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Old 07-11-2013, 08:01 PM
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OK, sounds good......I will update this thread with my current settings and my impressions as to how I like my current setup. I will also include alignment settings for those interested.
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Old 07-11-2013, 08:17 PM
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Swapped my rear swift springs to 8K. So far loving it on the twisty backroads near my house.
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