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Old 09-19-2009, 01:37 PM   #1
CT03911
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Default Sway bar adjustment

I want to correct slight understeer. I am going to tighten the rear sway a notch. If I recall correctly, just jack the car (I'll do one side at a time) and that relieves the pressure to make the adjustment. Right? Torque number anyone?
Next question. anyone move the bar up a hole on just one side for a smaller correction and if so which side would you do where you drive tracks that are orientated clockwise?
Lastly, my understanding is if you want a tire pressure setting adjustment to correct understeer you would ADD pressure to the front tires (or take it out of the rears). I don't get how essentially reducing the footprint of the front tire could do this?
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Old 09-19-2009, 04:31 PM   #2
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Doesn't matter which side if u just do one side- just adds stiffness or softness since tension or lack of is even all across. U should soften the front bar for less push and maybe one off stiff from the back. U may want to put loctite on the swaybar links they mite loosen up and hear the dreaded clunking noise. Tire pressures I tend to run them lower like 31-32 hot they grip better for me(Mpsc or kuhmos). Nething over 36 it starts to slide for me. Mike
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Old 09-19-2009, 04:57 PM   #3
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I believe proper torque is 48 ft/lbs.

Cheers,
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Old 09-19-2009, 05:09 PM   #4
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^ sounds low?
i tight it with all the muscle i got (not much).
i do not use loctite.
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Old 09-19-2009, 06:02 PM   #5
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Quote:
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^ sounds low?
i tight it with all the muscle i got (not much).
i do not use loctite.
When you're on your back trying to tighten those nuts, 48ft/lbs might seem impossible to some folks.

I don't use loctite either.

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Old 09-19-2009, 06:59 PM   #6
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I use two nuts on each bolt.

To help with understeer, like you mentioned make the rear sway bar one hole tighter.

I would always adjust both sides.
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Old 09-19-2009, 07:00 PM   #7
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adding air to the front reduces understeer and removing air from the rears reduces oversteer. It's counterintuitive.
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Old 09-19-2009, 07:02 PM   #8
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The trick is, after screwing around looking at it and jacking it up and down, jack the car just a bit on the side you want to adjust. Just lighten the car really and the sway bar bolt comes right out.
I did one side only on the back, one hole tighter to reduce understeer slightly.
I just tightened it very firm and no locktight. It's not going anywhere.
I still have the tire pressure question but perhaps it's academic because with MPSC's I find outside of a small pressure window for me the car feels loose.
I just don't understand why increasing front tire pressure reduces understeer. I was referencing Tire Rack's graph somewhere on their site on the various ways to effect oversteer and understeer (tire pressure, springs, tire width, sways, etc. Interesting chart)
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Old 09-19-2009, 07:47 PM   #9
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you did WHAT? you need to adjust BOTH sides at the same time.
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Old 09-19-2009, 07:51 PM   #10
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The reason I loctite mine is we have lovely paved roads in San francisco. Can't even count number of times front swaybar went clunkity clunk. Mike
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Old 09-19-2009, 08:08 PM   #11
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va122, a well recognized race shop advised that moving one side a single hole was an effective way to make a small change. That was all I wanted.
I was wondering before I did it (when I originally posted) if it made a difference which side. I now know it does not. Did my homework and searched which I was too busy for before because I wanted to do an oil change, air filter, pads, brake bleed and tire swap before dark.
I will check the bolts more frequently because I did not use locktite and see what happens.
Also, I agree the tire pressure change to effect oversteer/understeer IS counterintuitive so I was wondering if anyone can explain WHY it works.
Thanks all.
Dennis
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Old 09-19-2009, 08:57 PM   #12
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Quote:
Originally Posted by CT03911 View Post
va122, a well recognized race shop advised that moving one side a single hole was an effective way to make a small change. That was all I wanted.
I was wondering before I did it (when I originally posted) if it made a difference which side. I now know it does not. Did my homework and searched which I was too busy for before because I wanted to do an oil change, air filter, pads, brake bleed and tire swap before dark.
I will check the bolts more frequently because I did not use locktite and see what happens.
Also, I agree the tire pressure change to effect oversteer/understeer IS counterintuitive so I was wondering if anyone can explain WHY it works.
Thanks all.
Dennis
Yes , changing one side of the bar is fine, although I've never been able to detect changes in balance at such a fine level. And the bar adjustments are usually easier when both sides are lifted, since raising only one side generates quite a large pre-load.

Increasing tire pressure reduces slip angle. So, within reason, when pressure is increased, the contact patch of the tire is in closer alignment with the direction of the wheel, due to less sidewall flex, thus better traction. Assuming you increase pressure in both tires on one end, that is the end that will have better traction (relative to before the adjustment). In cars with substantial understeer or oversteer, adjusting tire pressure will not offset a suspension or weight imbalance, but it can reduce the level of that condition.
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Old 09-19-2009, 10:06 PM   #13
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Thanks ELH. Finally, it is starting to make sense. Perhaps my one side only single hole adjustment will be too small to detect. I will tweak tire pressures next and see from there.
Actually the track I will be at next (Lime Rock) has less slow speed tight corners than the last track (Lightning) and I suspect the understeer I was feeling will be less evident anyway so a very small change is fine by me.
Great info, thanks to all.
Dennis
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Old 09-20-2009, 01:35 AM   #14
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Dennis what are your alignment settings ie camber/toe- that in itself can negate me understeer. I take it u did the aftermarket rear towlinks(stock eccentrics can shift or loosen). Toe out in the front does wonders to turn in. Mike
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Old 09-20-2009, 03:41 PM   #15
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Why the rear??? If it is understeering soften the front. No jacks needed just drive up on a 2x6 reach under loosen move tighten. I use 1 nut and a lock washer. Takes me less than 5 minutes to do either front or rear. I have done this a lot


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Old 09-20-2009, 03:41 PM
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