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Discussion Starter #1
people who autox, i need your help.


im ordering ksport coilovers. the first gen that had a decent shock on the back.

the default rates are 11kg/9kg. im worried that it is biased to understeer, which it is. BUT i have a rear swaybar. a big one. custom endlinks. BUT, i really have lost throttle off oversteer recently because im running 245's all around.

9kg/9kg and a rear swaybar might be twitchy. im trying to setup the car for the track, as i think ill be doing more of that vs autox in the future, but i want to be able to have the car do what i want it to around the autox course as well.

Stretch has said (in my searches) that both are good for the v6. crossbow ran 13/13 but im not sure if he ran a rear sway.
please help.


vote.

11/9

or

9/9.


im pumped. anyone interested in some used H&R Springs?
 

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I say go with a neatral set up, the rear bar should help induce some oversteer, or u could get stiffer in the rear and get a front sway to balance.

Feel it out, do a few courses and see what u need.
 

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Discussion Starter #3
well, a bit too little, to late, ordered 11kg front 9kg rear. im keeping the racing beat rear bar on.


time for fun.
 

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I have the D2's which is what crossbow has and they are 13F 9R, with the RB sway, and let me tell you, this car is very twitchy at high speed. Anything above 60kph, and you are well aware that the rear end can slide out at even the slightest jerk of the steering wheel. I have the RB front bar awaiting installation because of this. Yeah, it's fun for the first little bit and then it's OHH no in the rain. I have had the car do a complete 180 at 40kph when making a right turn on damp roads.
 

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Discussion Starter #5
what tires are you running? and why were you driving agressive in the rain?


ive got massive ( the widest tires for the 6) 245's all around. and the new default rates for the ksports are 11/9.

im keeping the rear bar, and after more research, i found that this setup is almost exactly how stretch had his setup ( with the rear bar, rate wise) BEFORE he found he wanted more oversteer.

here's a link to the thread.

http://forum.mazda6club.com/index.php?show...32159&st=15

very interesting, stretch outlines the addition of the rear swaybar, and what it accomplishes rate wise.

im wondering, however, if this is the same force, because in reality, the swaybar uses the other spring on the other side to apply more force at 1/3 the moment arm of the actual spring. so the swaybars force is completely dependent on the spring rate. its effectivley a multiplier.

now, i believe it is a 1/3 or 1/6 multiplier, because it acts at 1/3 the length on both sides of the suspension.

i need to go find kevink2's swaybar calculation stuff
 

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Discussion Starter #6
stretch. i need your input. im tuning for a bit less oversteer than you like, but enough that i can call upon it rather easily. i dont think your idea with the rear swaybar's rate is correct, because it is dependent on the spring rates in the rear.

i could effectivley be making my rear springrate 12kg/mm in the rear while cornering. perhaps a bit less. im not sure tho.

i need help with how much the rear swaybar will affect the springrate in the rear. kevink2 says its a 4x multiplier, i dont buy it at all. that is impossible.
 

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Actually, I calculated the sway bar provides five times more reistance than stock, but I think Kevin says my math is wrong. Either way, the difference is HUGE:
http://forum.mazda6tech.com/viewtopic.php?t=1630

In regards to the coilovers: I'd suggest not getting K-Sport coilovers because the shocks suck. Without good shocks the car is very hard to control, something I learned the hard way. Thus, if you do get K-Sports, Koni shocks in the rear are a mandatory upgrade- but at that point you'll have paid near as much as KW coilovers anyway (which I hear come with 11kg/9kg/mm springs).

Anyway, I'd go with 9kg/mm springs in all four corners. Crossbow was running 13kg/mm front, 9kg/mm rear and his car understeered like crazy until he got the rear sway bar. I had 11kg front, 9kg rear with the rear sway and felt it still understeered way too much. 8kg, 6kg springs felt better because it allowed the sway bars to play a proportionally larger role in providing roll resistance, and my rear sway dwarfed the front.

Anyway... yada yada yada, don't get K-Sports, but if you do, I'd recommend 9kg/mm all around. And because I don't trust that company, make sure the springs they send you actually look different from the normal kits. I have a hunch they'll send you the normal kit in hope that you'll never be the wiser. FWIW, after three years I'm still waiting for my D2 rear shock replacements (not that I care anymore).

Considering how much better Koni shocks are than K-Sport shocks and that so much roll resistance comes from sways, don't rule out the Racing Beat suspension package purely because of the low spring rates. It's still pretty good at the limit, and (if you care) it totally romps the K-Sports as a daily driver package.
 

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Discussion Starter #8
well, stretch, i got the older rear shocks for the ksport kit, they are valved better ( not adjustable tho). they only just make the clunking noise or such later on, making ksport change the rear shocks to the ones you got, the weaker ones.


just a thought.
 

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we acutally got ksport to go back to the orignal chorme rear shocks which provides much better damping performance compare to the the current orange rear shocks. There will be some squeek noise from the chrome shcoks at low speed (which was the reason that ksport revised the kit)
 

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Discussion Starter #10
ok, stretch, perhaps i didnt pose my question correctly. the rb bar provides 5x the resistance of the stock bar, sure, but what im talking about is what actually matters, how much force the swaybar can add to the spring ? it should be a multiplier of the spring. be it 10%, 20%, 30% or somthing. thats what im wondering.


it depends, on the spring, correct? and the amount of deflection depends on the spring. you posted before a solid number to add to the rear as increasing the spring rate, but adding a larger spring, changes that number, correct?


i think ill have a very much oversteering car. despite the 11/9 rate, because after i added the lb/in that you said it added a long time ago, it went to 11/12-13. and you were talking about softer 4.5 kg/mm springs at that time.
 

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Arch I was not driving agressively, my brother can vouch for me as he was in the car when it happen. I'm running on sotck tires which have taken there fair share of autoX abuse over the past 2 years. Even on freeway offramps you can feel the rear of the car slide out if you are pushing it too hard.


Stretch where did you get your info on the KW coilovers. I installed them on a members car already and they didn't feek and stiffer than the Tein's. The front spring helpers seems to offer a progresive spring rate which I didn't like and made the car handle a little odd. The didn't feel as stick as my D2's either.
 

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....... the rb bar provides 5x the resistance of the stock bar, sure, but what im talking about is what actually matters, how much force the swaybar can add to the spring ? it should be a multiplier of the spring. be it 10%, 20%, 30% or somthing. thats what im wondering.
it depends, on the spring, correct? ........[/b]
1st, mazda says 60/40 weight dist'n for all models. Nope. Using a cornerweighted Car and Driver mtx wagon as a base, and catalog model weight differences, I figure an mtx i sedan at 56/44, and an mtx s sedan at 59/41. Also, my experience is you want more oversteer for auto-x, vs big track days. You see almost all cars lifting a wheel at the scca autox nationals, but watch the mazda6 sedans on speedchannel at the big tracks an they only lift a rear if they hit a curb on a corner. --->Point being what is good for a 6i at autox will not be best for a 6s at watkins glen.

Th RB is 4x siffer than the sedan rear, which is 19mm. It is 5x stiffer than the 18mm bar in the hatch and wagon.

Stretch had the puhn formula right, but interpretation regarding single wheel rate and roll rate and motion ratio incorrect, as I explained here:

http://forum.mazda6tech.com/about4155.html

The oem rear spring is about 160 lb/in, or 2.9 kg/mm

Below I list the rear bar size, and it's effective spring rate (lb/in and kg/mm) in roll at the spring location. This value would be added to whatever spring is used for the net effective spring rate in roll.

18 ---- 210 --- 3.6
19 ---- 250 --- 4.5
22 ---- 440 --- 7.9
24 ---- 630 -- 11.3
27 --- 1010 -- 18.0

Note these theoretical rates will be reduced based on bushing flex, and body structure flex.

For the 6s with the glen in mind, I would suggest the 11/9 springs, which better match the weight distribution, and tweek with bars.

assuming stock front bar is used in your 6s sedan, going from oem 19 rear to 24 rear is the same in cornering as if you added 6.8 kg/mm more rear spring rate, and kept the 19mm bar. Even assuming bars are 80% effective due to bushing flex, the 11/9 springs with 24mm rear bar is like cornering with 11/14 springs and oem bars.
 

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Kevin would you be kind enough to do these Calculations for the front swaybar by Racing beat as well with 11kg/mm front springs as well. Thanks.
 
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