Quick question on sway bar adjustment on alignment

[ghoonk]

I'm having my Whiteline sway bars installed this week in preparation for track day this Friday evening.

The front one (26mm, non-adjustable) was installed today, and the rear ones (24mm, adjustable to 22mm and 26mm) will be installed on Wednesday (I've just been told that they'd been shipped out of the UK today via DHL 2-day shipping).

I'll be getting my alignment redone immediately after the installation of the rear sway bars

Question is:

Will I need to have the alignment re-done if I change the stiffness of the rear sway bar?

[Fourdoor]

The sway bars should have zero effect on the alignment of your car... under steady state conditions (car not moving / cornering) the sway bars should be totally unloaded and have no effect on alignment.

Keith

[ghoonk]

Thanks, Keith. That's what I was guessing, but I wanted someone with actually has sway bars to confirm that

Cheers

Kenneth

[Fourdoor]

I don't have them on the EVO, but I have had upgraded sway bars for past vehicles

Keith

[ghoonk]

Eh? I would have thought you'd had sway bar-ed your Evo.

Another quick question:

I'm looking at this setup matrix now at http://www3.sympatico.ca/cbarnett/SetupMatrix.html

I'm getting a bit of corner entry understeer, and my car has been corner balanced with a cross corner weight of 49.3% and front-rear weight distribution of 61%/39%.

To correct this, I'm thinking of making the following changes:

installation of front and rear sway bars -- whiteline 26mm front, 24mm (adjustable to 22mm, 24mm and 26mm) rear sway bars

reduce tire pressure to
front 32 psi (currently 34 psi)
rear 30 psi (currently 34 psi)

lower front ride height by 8mm
rear no change

set toe-in (positive toe)
front 0 toe (currently 0)
rear 0.05mm per side (-0.1mm total) (currently toe-out of 0.03 per side)

damping (from softest, max 30 clicks)
front 15 clicks (currently at 30)
rear 25 clicks (currently at 15)

Question:

1. too many changes in one go?
2. will lowering of the front ride height affect the cross-corner balance?

Track day is just 3 days away, my rear sway bars come in tomorrow and will be installed tomorrow and alignment done (until robi comes to Dubai) in the same day. Toyo R888s are in port but will not be released on time for track day, so I'll be running ADVAN Sport tires that have seen 5 track days so far.

[Warrtalon]

Yes, way too many changes in one go, and the changes aren't all accurate either. You would not put more pressure in the front tires than the rear to combat understeer - that's backwards. You want more grip in the front and less in the rear. Toe-in is also not what you want - you would want toe-out in the front.

Instead of all of those changes, I would suggest combating understeer by getting the proper spring rates and damping/valving without adding two swaybars and making all those other changes. Lowering the front ride height will likely throw off the balancing.

[ghoonk]

Okay, that seems contrary to what many sites are stating, e.g. http://en.wikipedia.org/wiki/Racing_setup

So, I'll run higher psi up front (32, cold) and lower psi down rear (30, cold). It's too late to get new spring rates and custom valving, and the sway bars are already sorted out anyway.

I've been advised to try to set slight toe-out on front, slight toe-in on rear, to help the car handle more neutral, but I have my concerns about it.

As of right now, I'm running 0 toe front, 0.03mm toe-out on the rear.

I can induce corner entry understeer without scrubbing the tires, lift-off and get the rear to rotate, get on the throttle when the nose points towards the apex, unwind the steering, get on the throttle and get some really decent corner exit speed.

I will not adjust the ride height for now (and leave that to robi), but will probably try out a softer damping/rebound setting on the front and firm up the rear, and test out the settings on the Friday track day.

[Warrtalon]

I'm not sure what you're saying. I said to run more psi in the REAR, but you again wrote that you'd put more in the front. Which of us is confused? You want more pressure in the rear and less in front, because that INCREASES front grip. More front grip means less understeer just as less rear grip means more oversteer (in general). You're saying that you're reading major Evo handling/tuning sites that say differently? I run 30F/33R on my V710s when autocrossing and similar pressures on the road course, although what really matters is your hot pressure after running hard on track.

I don't think your sway bars are sorted out. Just adding them doesn't mean they will work. They _HAVE_ to be combined with the proper spring rates, valving, and alignment. Putting them on by themselves will not work as desired. It's more like putting on a blindfold and throwing a knife at a target right in front of you. It may or may not hit the desired spot, but it's DEFINITELY going to hit something.

I would do 0 rear toe with 1/16th toe-out up front. However, if Robi is doing your alignment, then let him decide. For now, go with 0 toe all around or 0 toe rear plus slight toe-out front, imo.

[ghoonk]

right, so less pressure on the front, more on the rear.

Got it, thanks

[Warrtalon]

Yeah, I'm not sure why Wikipedia has it backwards, but that's definitely not a racing setup resource. It's just a public, online dictionary.

[ghoonk]

Will try the same tire pressures as you have (I'm running Enkei RPF1s in 17x8.5 with 235/34/17 rubbers)

Have you got a link to a decent resource? I'm surprised that no one has put a reference together for F/AWD cars so far...

If I soften the rebound settings on the front, I should get less understeer, right?

[Warrtalon]

You shouldn't run the same tire pressures on street tires. On street tires, your sidewall is much weaker, so you have to inflate the tires a lot more to avoid rollover. On street tires, I'd start at 38f/40r.

Not sure on the rebound settings. There's a lot more to it than that - depends on many other factors of your setup.

[ghoonk]

Alright. I'll run 38f/40r on street tires and 30f/35r on my semislicks.

As it were, my street tires have seen 5 trackdays and they have gone hard. I'm wondering now if high tire pressures and hard rubbers are a good combination for a 2.46km, tight technical course -- I'm just worried it'd be a bit twitchy

[Warrtalon]

You can adjust between sessions.

[ghoonk]

Hi Warr

I got the alignment done today --

3 deg negative camber up front
1.8 deg negative camber
0 toe front (I would have gone for negative toe,but I decided to keep the front end a bit more neutral for now to see the effect -- i can get it changed before next track day to see the difference)
+1.2 mm toe (toe-in) on the rear
38f/40r tire pressure on street tires (Yokohama ADVAN Sport 235/45/17 on Enkei RPF1 17 x 8.5)

Initial impressions :

Seems that I need to turn my steering wheel more to make the same turn. Either that or the front just seems to turn with less effort. Understeer is still there, but I can use delicate application of lift-off oversteer to make minute corrections while taking a bend. The rear doesn't step out suddenly as much as before (probably because I have gone from -ve toe to +ve toe on the rear.

I'm still fairly inexperienced where alignment is concerned, and I hope you can spare the patience to explain the benefit of -ve toe (toe-out) on the front wheels -- better turn-in and less understeer? With 3 deg of -ve camber, would a -ve toe make better use of the contact patch while turning?

Cheers

Kenneth