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Which means "Evil Twin". Lets see your projects where you change boring into fun or create the fun from scratch.
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 Post subject: Re: Anti roll bars
PostPosted: Fri Jan 29, 2021 10:41 am 
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mk e wrote:
TheDarkSideOfWill wrote:
Oh yeah, I forgot you know the Ti64 dude. I re-discovered them and have been thinking about snagging a few bolts from them.
A pair of Ti 5/8" bolts in each rear strut should save me about 1 lb of unsprung weight per rear corner. I'm thinking of titanium clutch cover bolts to reduce engine speed rotating mass and using Ti in the Northstar external case half locations just for S&Gs.


I'm starting to think you like the fiero more than you like your ferrari....... :lol:


Just practice for doing a good job on the Ferrari :P

Also, I need to organize my way into a garage again.


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 Post subject: Re: Anti roll bars
PostPosted: Mon Mar 22, 2021 10:14 pm 
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pulled the trigged on a set of 600ft/in front spring that should better match the 400lb/in rear.....mentally very close to the front sway bar to go with....its in the cart.....


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 Post subject: Re: Anti roll bars
PostPosted: Tue Mar 23, 2021 6:34 am 
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Posts: 263
Do it! Do it! Do it!

I know, not helping.. :?

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 Post subject: Re: Anti roll bars
PostPosted: Tue Mar 23, 2021 7:28 am 
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MerlinTech wrote:
Do it! Do it! Do it!

I know, not helping.. :?

You keep that up and I'll show Lana your posts! ;)

It is all picked out and in the cart....

Coleman doesn't carry the rear bar I thought I liked.....I'll need to look at the numbers a bit more or find another speedway engineering dealer. My thought was I'd kind of set the front then tune the rear as those bars come in 1/32" OD steps but that could be over kill and why Coleman doesn't carry them.


Attachments:
front swaybar.JPG
front swaybar.JPG [ 109.28 KiB | Viewed 70 times ]
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 Post subject: Re: Anti roll bars
PostPosted: Wed Mar 24, 2021 6:28 am 
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:o Not Lana !
I am in big trouble now.

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 Post subject: Re: Anti roll bars
PostPosted: Wed Mar 24, 2021 7:41 am 
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1 1/4 is a big bar
Is there any kind of institutional knowledge of 308 setup that says that's a good idea... on the front end of a mid-engine car.

Admittedly, using the 308 style gearbox puts the engine 6 inches higher in the body than it should be, but I'd expect that to show up in the rear bar...


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 Post subject: Re: Anti roll bars
PostPosted: Wed Mar 24, 2021 9:14 am 
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TheDarkSideOfWill wrote:
1 1/4 is a big bar
Is there any kind of institutional knowledge of 308 setup that says that's a good idea... on the front end of a mid-engine car.

Admittedly, using the 308 style gearbox puts the engine 6 inches higher in the body than it should be, but I'd expect that to show up in the rear bar...


Notice its hollow though....1.25OD, .75ID making 30% more stiffness than a 1.125" bar not the nearly double a solid 1.25 would be. For sure its the stiffest I'd consider....but once the car is set up for these bars a new bar is $150 and maybe 30 minutes to install so changing my mind becomes easy.

The aftermarket solid bars came 1.0, 1.125 front and .75, .875 rear so I would say that is a good baseline for where most setups ended up back in the day and the 1, .75 combo is the hot street car setup as I understand it anyway.

The 1.25 hollow bars are available in .095, .125, .188, .250 wall. .095 is 17% stiffer than a solid 1", .125 is about 20% under a 1.125, .188 about 20% over the 1.125. All probably good options.

on the rear solid 3/4, 13/16, 7/8, 5/16, 1 are available as are hollow 1" OD with .095, .125, .188, .25 wall with .095 wall almost as stiff as a solid 7/8. Almost available are 1.25 bars that are gun drilled .75" and OD turned so only the bearing area is 1.25. they com with ODs from 0.91 to 1.25 on .030 steps.

Lots of options....which has me pondering quite a few variables including spring rates which also effect roll stiffness. I've seen a lot of talk about doing springs by frequency which leads to very different than normal 308 setup spring choices, like rear springs that are stiff than the front. That would cause MASSIVE oversteer without a MASSIVE front sway bar.....that seems wrong and why I ordered the new 600lb/in front springs that are 50% stiffer than the rear and should get the car near neutral steer with no sway bars....well, probably still a bit of oversteer completely bar less but close. I'm not sure this is right though as the point of springs is to hold up the car....which is what the frequency method is all about, use the spring to hold up the car and respond to bumps and that sway bars to tune roll stiffness. So much to think about.....


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 Post subject: Re: Anti roll bars
PostPosted: Wed Mar 24, 2021 11:30 am 
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mk e wrote:
TheDarkSideOfWill wrote:
I've seen a lot of talk about doing springs by frequency which leads to very different than normal 308 setup spring choices, like rear springs that are stiff than the front.


Is that spring rate or wheel rate? The wheel rate needs to be stiffer on the heavier end of the car BUT the rear suspension motion ratio is close to 1, while the front suspension motion ratio is <1, so the front spring rate will be higher than the wheel rate.


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 Post subject: Re: Anti roll bars
PostPosted: Wed Mar 24, 2021 12:04 pm 
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TheDarkSideOfWill wrote:

Is that spring rate or wheel rate? The wheel rate needs to be stiffer on the heavier end of the car BUT the rear suspension motion ratio is close to 1, while the front suspension motion ratio is <1, so the front spring rate will be higher than the wheel rate.


Its spring rate. Yes the motion ration is different but so is the weight....it ends up about a wash but the rear wanting slightly stiffer springs to have equal settling at each end. That is the idea in talking frequency...that is all in the math so you can compare setups on any car directly.....but as I said it doesn't seem to work out well on a 308 other than the stiffer front spring I just ordered put the front freq at 1.6 I think it is which is good number, that rear is way soft though.


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 Post subject: Re: Anti roll bars
PostPosted: Wed Mar 24, 2021 3:34 pm 
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Here's where the car is with the new front springs....1.49 front, 1.42 rear.
Attachment:
308 spring frequency.JPG
308 spring frequency.JPG [ 97.38 KiB | Viewed 54 times ]



the ref I found is:
passenger car: 1.0
sports car 1.25-1.75
low/no down force autoX, roadrace 2.0-2.5

stock subaru brz 1.45 so my new super stiff springs are nothing like super stiff and are actually what would be considered a soft spring, stiff bar setup.

To get to 2.0 would be 1100/900....that's a lot of spring compared to what I here people are running! Another way I've done the math is 4" travel is good, 1.5" sag max with 0 preload, that pops out 715/595 and says my new front spring belong on the back and I need new new front springs. The other end is 1" sag min pops out 1073/894 which matches the 2.0hz numbers

With my current 450/400 springs the numbers are 1.29/1.34.....so the rear is stiffer than the front which certainly explains the oversteer issue.

Here's my swaybar math


Attachments:
swaybar math.JPG
swaybar math.JPG [ 77.92 KiB | Viewed 54 times ]
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