THSCC Forums

I too am working on the setup. Currently I'm painting a set of Kosei K3's. This week the wheels, 32mm sway bar, AST DA's, and Kartboy End Links have been delivered.... The 34mm sway bar showed up today.

I also bought a full clear bra for the car that I will be installing tomorrow. I already have a stainless shorty exhaust and a set of low use 295's to practice on (along with a 315 to test fit). Everything should be on and ready to go for the Triad event at Danville on the 22nd.

I hate to miss the Jimmy V, but my co-driver bought a new house and has a busy schedule that weekend. Plus with the Blytheville Pro on June 5th and DC on June 19th, the wife would probably kill me - AB

_________________
'14 Toyota Sequoia Platinum 4WD
Super Westerfield Bros - '93 Integra - LeChump Du Jour
STX 93 - Scion FR-S

Cool! Another one joins the S2000 party.

In the interest of full disclosure, my shocks should probably be called the "Lee Grimes valving," since it was Lee who made the suggestion that I try them. Lee told me at Nats 2008 that they have a bunch more rebound in them than the standard ones, and like 3 "units" more compression. They do the valving by replacing some kind of widget inside the shocks, and those widgets are numbered. I can't imagine Saini steering you wrong. I seem to remember him having run a curious alignment on his, but hey, it obviously worked.

The shock setting strategy you mention is unlike what Chris, Eric and I do with mine. We show up with all four at 50%; my thinking is that this allows the maximum amount of adjustment in any direction, at all ends of the car.

What exhaust did you get for it? I drove mine to VIR this afternoon, and at the end of the trip, my ears were ringing like I'd been at a rock concert. It's time to make this thing go away.

_________________
Karl S.
2014 Baby, 2014 House, 2013 Ford Focus ST, 2013 BMW 328i, 1994 Mercedes E320
(Insert passive aggressive signature line here)

BTW Aaron:



You're doing this yourself? I'd like to pick your brain if you are. I've got some film for my headlights that I've yet to put on. I tried one side and ruined it. Hopefully I won't ruin a second one.

_________________
Karl S.
2014 Baby, 2014 House, 2013 Ford Focus ST, 2013 BMW 328i, 1994 Mercedes E320
(Insert passive aggressive signature line here)

I'll take some pictures after it's done. The kit came with everything I need to do the job, along with an 30 minute instructional DVD. After putting on an ass load of graphics over the years, I think I should be able to do it ok, as long as I take my time. - AB

_________________
'14 Toyota Sequoia Platinum 4WD
Super Westerfield Bros - '93 Integra - LeChump Du Jour
STX 93 - Scion FR-S

Don't have one. Planning to just cut the stock one off and modify it so it can be easily clamped back on or we can clamp on a piece of straight pipe that will dump out the back. Probably with a turn-down tip and that way it could be rotated directionally should it be a sound problem somewhere.

Probably won't have that done by next weekend, though.


--Donnie

_________________
My Blog

Aaron, could you enlighten me as to the need for a FSB that big? 32/34mm?

I understand with the front strut suspension, you want to stay in negative/neutral camber for both lateral grip purposes as well as to keep from eating up the outside shoulder on your expensive and very wide r comps. But isn't there a point at which your effective wheel rate in roll conditions is so high that there is no more benefit of going any larger...in fact wouldn't it eventually be come a detriment to go stiffer given that you'll be lifting inside front tires to a greater degree (as in per unit turn, that tire will be off the ground for a longer amount of time)? And this will in turn transfer even more weight to the rear at corner exit (than it would purely from starting to accelerate hard again) and cause the car to push?

Just something that I've been wondering.

_________________
2011/2012 Autox VP
2013/2014.5 President
2013 Top Gun

2015 Fit

22R-EC => 4G63 => D16Y7 + D16Y8 => EJ255 + K24Z2 => K20Z3 + K24Z2 => K24Z2 + M54 => L15B

When it comes to setup, I'm not very technical and will never claim to be.

For autocross, there are very few "long" sweepers. It's all about quick transitions. The previous versions of the STi suffered from lacking the ability to quickly transition due to a soft front spring and a heavy car that was somewhat under-tired, even with 275's on the GD chassis. With stock class, only being able to change the FSB, you move to the biggest bar the car can handle and adjust toe to get it to rotate.

I spoke with Chris Carris for about 1.5 hours the week after I ordered the car. He was running a 32mm bar (as was anyone serious about running an STi) and said that it could have used a 34mm bar. If he hadn't ditched it, he would have had Niles build him the 34.

I also PM'd a bit with Jonathan Roberts, who piloted Donnie's '05 STi to 3 ProSolo championships. Jonathan said the car was best when the front bar was binding up, just prior to ripping the tab off the control arm

Obviously, roll stiffness has a point of diminishing returns. I have both a 32mm and 34mm bar and could change it out in about 10 minutes. With the SE's spring rates upped 16% in the front and 29% in the rear, my guess is the car could be fine with the 32mm bar, but I'm going to start with the 34mm. If I have to toe it out to make it rotate properly, that's fine, for what I gain transitionally from it will be worth it.

In your car, if I were to put R compounds onto it, I would be running at least a 30mm FSB. While the front end roll on streets wasn't horrible with your 25mm, it was noticable.

My view on FSB sizes changed a lot when driving the Corvette. We had 3 FSB's for the car: 32mm solid, 35mm hollow and 35mm solid. Of all of the bars, I liked the feel of the 32mm solid the best, but the clock said that the 35mm hollow was fastest.

There's a guy named Matthew Braun who has won a bazillion Tours/Pros/National Championships. He's a serious alien. The way he setups his cars (he tends to only drive RWD cars) is to put the biggest bar on a car that will make the car *slightly* push in transition and then steer with the throttle to make it rotate. There is a reason he is fast. - AB

_________________
'14 Toyota Sequoia Platinum 4WD
Super Westerfield Bros - '93 Integra - LeChump Du Jour
STX 93 - Scion FR-S

Good to know. I wasn't being critical, just wondering. I have no intention of going too crazy on the WRX till have I have another DD .

So the gist is that while in long-ish sweepers the monster FSB might not be ideal, it is more than made up for in the lack of lateral weight transfer in faster transitions?

Yes the larger RSB paired with the much stiffer spring rates in the rear of the SE is likely to be a major improvement to the balance of your car compared to the WRX/regular STI. Subaru sure wants their cars to push . If you look at the stock rates on the GR STI, you'd think it'd be decently balanced, but you have to remember the motion ratio of the rear double A-arm suspenion is much less than the front struts, so the effective wheel rate at the rear wheels is a lot lower than the GD STI.

Anyway, I wish I had done the alignment before you drove it. The -1.0ish deg of front camber (compared to stock 0) and 1/32" toe out per side made it handle like a different car. I've also been able to get comfortable with throttle lift rotation and trail braking to get it to push less (though it is likely partly/mostly to do with the alignment).

Are the 32/34mm bars tubular or solid?

_________________
2011/2012 Autox VP
2013/2014.5 President
2013 Top Gun

2015 Fit

22R-EC => 4G63 => D16Y7 + D16Y8 => EJ255 + K24Z2 => K20Z3 + K24Z2 => K24Z2 + M54 => L15B

Aaron,

Do you know what the relative stiffness was of the 35 mm hollow compared to the 32 mm solid? It is pretty easy to end up with a softer holow bar than a smaller diameter solid . . . in fact it can be hard to get a hollow bar as stiff especially if it is a complex shape.

Dick

_________________
Dick Rasmussen

FS 50 2018 Mustang GT

Yeah, I could tell pretty quickly that an alignment hadn't been done on the car and I'm sure it would help a lot

The 32 and 34mm are solid. - AB

Edit: Yes, what I gain in transition will be less than what I lose in the sweepers. I can usually drive a different line in the sweepers to make it work, but driving a different "transition" line isn't viable.

_________________
'14 Toyota Sequoia Platinum 4WD
Super Westerfield Bros - '93 Integra - LeChump Du Jour
STX 93 - Scion FR-S

All 3 bars are Addco bars. I went up to Addco (beautiful drive through the NC mountains) to pick them up. The 35 hollow was 20% stiffer than the 32mm solid. The 35mm solid was 30% stiffer than the 35mm hollow.

It was pretty evident which bar was the stiffest. The 35mm solid would make the car push like a dump truck. The 35mm hollow had a slight push, but alleviated a lot of corner exit hard throttle oversteer. The 32mm felt the best on corner entry with no push, but induced a ton of corner exit oversteer on throttle. - AB

_________________
'14 Toyota Sequoia Platinum 4WD
Super Westerfield Bros - '93 Integra - LeChump Du Jour
STX 93 - Scion FR-S

A hollow bar's J/m ratio will always be greater for a hollow bar (r_outer == r_solid) compared to a solid bar regardless of the thickness of the bar walls. That being said, an autocross is more after wheel rate/stiffness and if in meeting our needs, the bar is lighter? Then great. So the question is why would you not get a hollow bar? Well if you are constrained to say 35 mm OD due to mounts and a 35mm hollow doesn't meet your stiffness needs, then go solid.

Since J (torsional constant) goes up on a hollow bar with R_outer^4 - R_inner^4, small increases in OD on a hollow bar compared to a solid bar, causes this term: R_outer^4 to get very large, very quickly. However, you still have to subtract out the R_inner^4 term on a hollow bar. But with that, said, the R_outer^4 goes up so quickly that the R_inner^4 terms is almost negliglble.

So yes, would suspect a 35mm with ~5mm wall thickness will be stiffer than a 32mm solid AND be lighter (assuming equal moment arms and torsional length and material ie density and elastic modulus).

32 solid J = pi/2*(32/2)^4 = 103000mm^4
35 hollow (5mm wall) J = pi/2*(17.5^4-12.5^4) = 109000mm^4
35 hollow (7mm wall) J = pi/2*(17.5^4-10.5^4) = 128000mm^4
35 solid = pi/2*(17.5^4) = 147000mm^4

Just an example. The wall thickness might be more than 5mm or materials might be different, or moment arms might be shorter to make Aarons numbers work (percent differences). And this is purely the torsional constant and not the spring rate. You still need elastic modulus, torsional length, moment arm length etc to get those figures.

_________________
2011/2012 Autox VP
2013/2014.5 President
2013 Top Gun

2015 Fit

22R-EC => 4G63 => D16Y7 + D16Y8 => EJ255 + K24Z2 => K20Z3 + K24Z2 => K24Z2 + M54 => L15B

Did you do this since the last autocross? (I hope not!)

James,

??? My old engineering math is pretty weak, especially anything mechanical but I'm not sure all your notation made it through the web.

Are you saying that with the same material a given OD hollow bar will be stiffer than a solid bar? Not according to all the equations I used to use since they subtract out the contribution of the "missing" solid diameter.

I agree that the "inner" portion of a solid bar contributes much less to the twist resistance than the outer portion. This is why (according to what I thought was correct) a larger OD hollow bar can provide the desired twist resistance with less weight.

Dick

_________________
Dick Rasmussen

FS 50 2018 Mustang GT

I fully understand. Been there, done that, won a a Nationals in 77 . My 260Z was tail happy and would spin the inside tire much too easily. Put a big front bar on it, improved balance, turn in response, AND allowed better corner exit traction. Too big a bar would cause push immediately after turn in . . . before the car could rotate.

_________________
Dick Rasmussen

FS 50 2018 Mustang GT