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Old 01-16-2019, 11:57 AM   #1
benji01
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Member#: 439517
Join Date: Feb 2016
Chapter/Region: International
Location: UK.
Vehicle:
1999 Sti Ra / 02 Wrx
white

Default 2002 Ride Height.

Afternoon chaps,

I've recently fitted a bunch of parts to my 02 wrx and in the process of few other items, but i thought id ask.
ive fitted the coil overs and to a height that to me looks nice but i've wondered if over done it, i've attached a few pictures of the control arm.
Parts fitted -
Bilstein coil overs
Whiteline Camber top mounts KCA335
Whiteline roll correction kit
CDF anti lift kit
super pro bushes
stock 20mm ARB.

To me the control arm should have some angle to it not parallel?
Ride height is 335mm center to the arch lip.
any advice is great full





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Last edited by benji01; 01-16-2019 at 12:15 PM.
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Old 01-16-2019, 03:09 PM   #2
T-37
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Member#: 175624
Join Date: Mar 2008
Chapter/Region: MWSOC
Location: Wichita, KS
Vehicle:
0304 WRX WRX
SY WRB

Default

Ideally you want the roll center to be as close to the CG as possible to reduce the length of the moment arm between the two. The closer the two are, the less roll there should be. That said, it's fairly difficult to accurately locate your CG at each axle.

There's also likely a tradeoff in total cornering speed between having the GC lower with the outside tire optimized with more roll at a lower ride height vs having the CG higher with less roll with both tires optimized. It's probably pretty dependent on how the car is being used though. I think this is why you see some people opt for a lower front ride height with a lot of static negative camber. But what's (debatably) good for one intended use isn't great for a street car.

Here's an excellent article about it https://motoiq.com/the-ultimate-guid...e-roll-center/
(take note the image on page 3 about lowered vehicles)

That said, you're using geometry correcting ball joints/tie rods which does help the case a little bit, and your ride height isn't terribly low, but it's still likely not ideal. Remember the angles you're measuring should be from the pivot point (ball joint and inner pivots) not the control arm itself. To me that looks like an intersection somewhere below the oil pan. Both of my cars have the roll center kit. One of my cars is higher than yours (~343mm) with similar static camber (daily driver) and the other is lower (~330mm) with a lot more static camber (and bigger tires). The higher one is more responsive, the lower one corners faster.

Last edited by T-37; 01-16-2019 at 03:20 PM.
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Old 01-17-2019, 04:59 AM   #3
benji01
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1999 Sti Ra / 02 Wrx
white

Default

Thankyou for taking the time to reply to me.
i think i may try a ride height at 340mm and see how it feels, the car is just a fun toy that sees the odd track day and sprint so still needs to handle well ,
What height did you set the rear too?
and what size tyres do you run? as im currently on the stock 225, but have pondered on 235-40-17
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Old 01-20-2019, 02:30 PM   #4
Crispy 1
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SRP

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I hope I'm not hijacking your thread but this interests me and made me think a little more about my setup. So what is stock ride height in mm on a usdm02 wrx? I'm on lowering springs and Tokico blues and I just noticed how level my control arms look after putting on sti aluminum ones. I definitely need the roll Center correction kit. After you go lower than the roll center correction kit will fix then what? Are you just too low there no matter what without custom work or? Is the whiteline roll center correction kit the one that makes the biggest change or is there a different one that is better or offers more correction?
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Old 01-20-2019, 02:53 PM   #5
Blktrax
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Very similar setup, front arms and rear arms have a very slight angle down.



Stock Measurements

Last edited by Blktrax; 01-21-2019 at 09:11 AM.
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Old 01-21-2019, 06:28 AM   #6
2pot
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https://forums.nasioc.com/forums/sho....php?t=1744593

For a road car:
Minimum 14.25" front, 13.75" rear.
Personally, I prefer more height and forward rake. 14.5" front 14.2"-14.75" rear - Increased positive rake mitigates against understeer, without using a bigger rear bar.
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Old 01-21-2019, 06:28 AM   #7
2pot
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double post
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Old 01-21-2019, 03:16 PM   #8
T-37
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Quote:
Originally Posted by benji01 View Post
Thankyou for taking the time to reply to me.
i think i may try a ride height at 340mm and see how it feels, the car is just a fun toy that sees the odd track day and sprint so still needs to handle well ,
What height did you set the rear too?
and what size tyres do you run? as im currently on the stock 225, but have pondered on 235-40-17
I'm not sure about a shorter tire on a 17". Your actual speed would be slower than the speedometer and overall gearing would be faster - maybe fine with a 5 speed, wouldn't want that with a 6 speed. In your case I would go with a good 225/45/17 (are you looking at all seasons or having a dedicated summer/winter set.) Something to keep in mind when going to grippier tires and trick suspension setups is your front wheel bearings especially are a weak link. If you're going to drive the car hard, they will not last long. I've done this upgrade to 08+ WRX knuckles and it's been great so far http://bbs.22b.com/forums/showthread...eavy-Track-use

Quote:
Originally Posted by Crispy 1 View Post
I'm on lowering springs and Tokico blues and I just noticed how level my control arms look after putting on sti aluminum ones. I definitely need the roll Center correction kit. After you go lower than the roll center correction kit will fix then what? Are you just too low there no matter what without custom work or? Is the whiteline roll center correction kit the one that makes the biggest change or is there a different one that is better or offers more correction?
Basically yes, those roll center kits don't correct for a much lowering, they're only about 1/4"-3/8" longer than a stock ball joints. A lot of people run stiffer front springs/bars to reduce roll/limit bump travel and more static camber to make it work in a performance setting, which is not great for a street setup.

If you want to run a lower height with better geometry look into Wisefabs knuckle kits that they just released a few weeks back. ~50mm/2in of geometry correction front and rear. This is the right way to be tarmac WRC/BTCC levels of low, and have the car perform well. (plus you get upgraded wheel bearings)

Quote:
Originally Posted by 2pot View Post
https://forums.nasioc.com/forums/sho....php?t=1744593

For a road car:
Minimum 14.25" front, 13.75" rear.
Personally, I prefer more height and forward rake. 14.5" front 14.2"-14.75" rear - Increased positive rake mitigates against understeer, without using a bigger rear bar.
Keep in mind that the thread you linked to was mostly a discussion of autocross setup. The OPs car in that thread was an STU car. For a couple years he ran in my region. Very fast driver and well set up car - regularly top pax. I would trust his data, but look for something more current if he's shared it. I should also add that the last time I saw his car it was very low in the front, but he had enough data that I'm sure he was not the set-and-forget type, and it must have worked for his setup. Around that time my WRX was regularly several seconds slower than him around a course, but my setup and driving were pretty poor, admittedly. That said, OP in this thread is in the UK, so probably not concerned about autox.

We don't know OPs spring rates or alignment settings, but your numbers are good rules of thumb and I would generally agree. Similar to RCE's recommended heights as well. But it wouldn't be the end of the world to go lower on a street car as long as it isn't always in the bumpstops. The best approach is to use some empirical data. Measure tire temps across the front tire at various heights within the intended usage (sounds like back roads, track days, etc). At a minimum, watch the tire wear for excessive outside shoulder tire wear over time.

Something to think about OP is that ride height and pitch changes will affect more than just the roll center, and there can be unintended consequences if you don't consider what all is changing. Too low and bumpstops are a problem. Overall CG height. Roll axis. Lower ride height increases caster. Increased reverse/negative rake will increase caster, and vice versa. Plus ride height changes will affect static camber and toe. So if you're going to to some testing and measurement, try to control the variables that you can (toe, camber), and consider the effects of those that you cannot (caster, CG, Roll axis, etc).

Last edited by T-37; 01-21-2019 at 03:25 PM.
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