Suspension Crew - Your advice goes here. - Miata Turbo Forum - Boost cars, acquire cats.

Welcome to Miataturbo.net   Members
 


Suspension, Brakes, Drivetrain discuss the wondrous effects of boost and your miata...

Reply
 
 
 
LinkBack Thread Tools Search this Thread
Old 07-27-2009, 10:18 AM   #1
Boost Czar
Thread Starter
iTrader: (61)
 
Braineack's Avatar
 
Join Date: May 2005
Location: Chantilly, VA
Posts: 72,900
Total Cats: 1,792
Default Suspension Crew - Your advice goes here.

Ran an autox this weekend and I'd say the car is feeling pretty good. However, I noticed a pretty big weak spot with the car, tight hairpins and sweepers. It just had too much understeer. I tried backing off the front shocks compression and adding more tire pressure up front, but to no real avail. What else can I do so the car is more neutral without dipping into the bank heavily.

Here's my current setup:

7/8" Front sway bar - stiffest setting
No rear bar
Koni Shocks
FM Springs (333/230)
-1.8 F | -2.0 R

I've had the front bar on the softer setting for years now and wit no rear bar the car felt great, however, it had too much lean and both my outside tires would lift and car felt uneasy. The current setup feels great otherwise, just not when I have to double back fast.

You can see what I'm talking about by comparing my car vs. this NC who was significantly faster than me:

was trouble spots were at 0:15, 0:25, & 0:35 the three hairpins.




now watch how this NC takes them, granted he has better tires a more low-end torque but he said he had no issue getting the car around them, my car wanted to push and i had to take them too slow.



0:15, 0:25, & 0:34

His time on that run was a 45.23, mine 48.39 I believe he was one of the fastest cars of the day, I want to be one of the faster guys of the day. I'm faster in the straights and slaloms, but I lost so much time where it counts.
Braineack is offline   Reply With Quote
Old 07-27-2009, 10:42 AM   #2
Miotta FTW!
iTrader: (24)
 
Splitime's Avatar
 
Join Date: Jun 2006
Location: Chicagoland, IL
Posts: 4,295
Total Cats: 26
Default

My format for promoting oversteer is typically stiffen suspension rear and go high on the rear tire pressure (above where it grips the best).
Splitime is offline   Reply With Quote
Old 07-27-2009, 11:24 AM   #3
y8s
2 Props,3 Dildos,& 1 Cat
iTrader: (8)
 
y8s's Avatar
 
Join Date: Jun 2005
Location: Fake Virginia
Posts: 19,038
Total Cats: 407
Default

my daddy always said: add traction to the end without it.

in order of easiest to hardest, I would try:

1. soften front shocks
2. reinstall rear bar (since you like flatter cornering)
3. go get the alignment you asked for (add a half degree of front neg camber)
y8s is offline   Reply With Quote
Old 07-27-2009, 11:25 AM   #4
y8s
2 Props,3 Dildos,& 1 Cat
iTrader: (8)
 
y8s's Avatar
 
Join Date: Jun 2005
Location: Fake Virginia
Posts: 19,038
Total Cats: 407
Default

Quote:
Originally Posted by Braineack View Post
it had too much lean and both my outside tires would lift
btw... ur doin it rong
y8s is offline   Reply With Quote
Old 07-27-2009, 11:50 AM   #5
Boost Czar
Thread Starter
iTrader: (61)
 
Braineack's Avatar
 
Join Date: May 2005
Location: Chantilly, VA
Posts: 72,900
Total Cats: 1,792
Default

haha. inside i mean.

yeah I had the rear shock at full stiff and backed the fronts off a little, I could have softened it more, but got lazy.

My fear with the rear bar, even when I had the stocker on the rear was pretty unpredictable and would let go without warning. I have much better control of it now and if it does ever step out it's a breeze to get back in line.

Would I simply benefit from swapping my springs to a 500/350 GC coilover setup?
Braineack is offline   Reply With Quote
Old 07-27-2009, 12:21 PM   #6
Elite Member
iTrader: (8)
 
Join Date: Aug 2007
Location: Bellingham, Wa
Posts: 2,732
Total Cats: 3
Default

I'm in the same boat. I also want to be up there with the fastest cars of the day. Last event I was half a second slower than a stock 91 :( (good driver, good tires).

Its the hairpins and other such obstacles that are killing my times, I know it. I have too slow waaaayyyy down to make it through otherwise I plow. It wasn't much better in that regard with my stock rear bar fyi.

I think more camber in front might be the ticket.
wayne_curr is offline   Reply With Quote
Old 07-27-2009, 12:26 PM   #7
Elite Member
iTrader: (8)
 
Join Date: Jun 2009
Location: Albany, NY
Posts: 1,523
Total Cats: 4
Default

BTW, you would need to lower front pressures for more front bite. +1 on adding some rear bar, or at least adding more rear pressure.
webby459 is offline   Reply With Quote
Old 07-27-2009, 12:27 PM   #8
Boost Czar
Thread Starter
iTrader: (61)
 
Braineack's Avatar
 
Join Date: May 2005
Location: Chantilly, VA
Posts: 72,900
Total Cats: 1,792
Default

I went in to get a new alignment last week, i wanted -2.0F and -1.8R, unfortunately I had my dad take the car, the shop got it on the machine, said it looked fine my specs were too aggressive, and took it off.

I started the day with 32psi in the front and rear. The wear marks went too far on the sidewall. once I put them to 36psi they were about right, I didn't think of adding any rear as well.
Braineack is offline   Reply With Quote
Old 07-27-2009, 01:18 PM   #9
Elite Member
iTrader: (8)
 
Join Date: Aug 2007
Location: Bellingham, Wa
Posts: 2,732
Total Cats: 3
Default

Quote:
Originally Posted by Braineack View Post
I went in to get a new alignment last week, i wanted -2.0F and -1.8R, unfortunately I had my dad take the car, the shop got it on the machine, said it looked fine my specs were too aggressive, and took it off.

I started the day with 32psi in the front and rear. The wear marks went too far on the sidewall. once I put them to 36psi they were about right, I didn't think of adding any rear as well.
You need more front bias than that. I'd say -2.2 front atleast. Alignment shops are really condescending when you give them funny numbers sometimes. Other times they just say "as long as you know what you're doing" and trust you. Most of the time, however, they treat you like an idiot and dont do what you say.
wayne_curr is offline   Reply With Quote
Old 07-27-2009, 01:28 PM   #10
Elite Member
iTrader: (12)
 
Join Date: Sep 2007
Location: Charlotte, NC
Posts: 6,868
Total Cats: 66
Default

I'm wondering how much of your understeer is attributed to your driving style. Not being condescending about it, but you might not be getting good weight transfer to the fronts to optimise available grip. I know try to brake a little too late, I over work the fronts and end up understeering in tight sections. Unfortunatly, unless you're doing a TnT, trying different techniques is extremely difficult as you only get a few short runs and each autoX layout is different. I'd try going stiffer on the front bar and softening the shocks a good bit.

The battle i'm having is lifting the rear inside tire. I can raise the car up some and increase the droop, but that raises the COG. I have tried disconnecting the rear sway (running 12k/8k springs) but didn't really notice a difference... it could have been my mentality of driving with a different setup. I've also tried running everything on a the stiff side, which feels good, but I can notice the understeer. So far, running the front sway on full stiff, the rear on med. and the shocks 12clicks from full on the front and 15 on the rear have yeilded a very balanced car. My other problem is power delivery to the wheels

My alignment specs would get posted, but I know it's all out of whack at the moment.
Doppelgänger is offline   Reply With Quote
Old 07-27-2009, 01:32 PM   #11
Boost Czar
Thread Starter
iTrader: (61)
 
Braineack's Avatar
 
Join Date: May 2005
Location: Chantilly, VA
Posts: 72,900
Total Cats: 1,792
Default

Quote:
Originally Posted by wayne_curr View Post
You need more front bias than that. I'd say -2.2 front atleast.
Meant to put -2.5F and -2.2R. That's the printout I gave them. They used to be a good shop, PBC, but now they have seem to have been bought out and are a general repair shop, not a spec miata shop anymore.

I guess I'll be giving the alignment another shot before anything else drastic.
Braineack is offline   Reply With Quote
Old 07-27-2009, 01:50 PM   #12
Elite Member
iTrader: (8)
 
Join Date: Aug 2007
Location: Bellingham, Wa
Posts: 2,732
Total Cats: 3
Default

Quote:
Originally Posted by Braineack View Post
Meant to put -2.5F and -2.2R. That's the printout I gave them. They used to be a good shop, PBC, but now they have seem to have been bought out and are a general repair shop, not a spec miata shop anymore.

I guess I'll be giving the alignment another shot before anything else drastic.
Please do and let me know what difference it makes.

Doppelganger; you could be right. I'm having the same problem, however, and have had many chances to test out some different things and just cannot make my car rotate around sweepers and sharp corners. It really does seem to be mostly related to the way the car is set up. Yes i'm a bad driver still and need much improvement on these points, but at the same time its hard to improve when your car doesn't do what you tell it.

These are my weakest points and i'm certain that when I figure them out i'll be one of the fastest cars of the day at our local autox events.
wayne_curr is offline   Reply With Quote
Old 07-27-2009, 01:56 PM   #13
Boost Czar
Thread Starter
iTrader: (61)
 
Braineack's Avatar
 
Join Date: May 2005
Location: Chantilly, VA
Posts: 72,900
Total Cats: 1,792
Default

this is what happens when i run a rear bar:



and here through the first slalom and at the end around 0:14:

Braineack is offline   Reply With Quote
Old 07-27-2009, 02:08 PM   #14
Elite Member
iTrader: (8)
 
Join Date: Aug 2007
Location: Bellingham, Wa
Posts: 2,732
Total Cats: 3
Default

Same problems i had. Although, it looks like we were both running bad tires at the time that we had a rear sway...have you run good tires with a rear sway at autox yet?
wayne_curr is offline   Reply With Quote
Old 07-27-2009, 02:10 PM   #15
Elite Member
iTrader: (8)
 
Join Date: Jun 2009
Location: Albany, NY
Posts: 1,523
Total Cats: 4
Default

Brain, what kind of diff do you have? A good bit of power on understeer could be caused by some lockup on power.

FWIW, my wife's n/a (used to be my track car) is dead-***** awesome neutral at track days with the FM 2.5 setup, front bar set to stiff, rear in the middle, max caster, neg 1.0 in front, 1.5 in back, zero toe in front, 1/16 toe in (max) in back. I run 2 psi less in back than in front. It has an open diff. Note that I have .5* bias in back, which is what I will keep no matter how much camber I dial in.

Looking at your approach to the first hairpin at 0:15, as hard as you were getting in, you need to be doing some trail braking if you don't want to plow. If you look at that other guy, his entry was WAY slower. With your belching turbo beast, you can enter slower and power out, you don't need to get in quite so hard. That car will seem like a different animal if you slow that entry.
webby459 is offline   Reply With Quote
Old 07-27-2009, 02:12 PM   #16
Boost Czar
Thread Starter
iTrader: (61)
 
Braineack's Avatar
 
Join Date: May 2005
Location: Chantilly, VA
Posts: 72,900
Total Cats: 1,792
Default

Torsen rear with 4.1 gears. Five years ago before the turbo and after autoxing the car 5 years N/A prior to that I had the thing nicely setup and was getting top times.

Watch my tach, I'm braking into the turn and I even blip the clutch to try to rotate it. I'm down to 2K in second gear, I probably could have benefited by dropping it in 1st. This is why large turbos plus autox kinda stink.


What if any benefit will these cool frame rails I have yet to install give me?
Braineack is offline   Reply With Quote
Old 07-27-2009, 04:23 PM   #17
Senior Member
iTrader: (4)
 
Join Date: Jan 2008
Location: Falls Church, VA
Posts: 1,367
Total Cats: 16
Default

You had crap tires in those videos though, right? The easiest/cheapest thing that I think would help would be reinstalling the stock rear bar. Most people who pull the rear bar are running springs that are significantly stiffer than FM rates, grippier tires, etc.

With my 450/300 springs and both front and rear FM bars it's just slightly tail happy. I'm going to put the stock rear back in and I should be pretty happy with that. But I don't like how it handles with no rear bar (disconnected end link) and 300# springs back there, no matter how much I play with the Konis or adjusting air pressure, it just understeers too much for me.

In general I'd say you can go with stiffer springs. I was worried that, omigosh I'm tripling the stock rates so it'll be way too stiff , but the roads around here are pretty good. 450/300 is totally streetable.
ScottFW is offline   Reply With Quote
Old 07-27-2009, 04:38 PM   #18
Boost Czar
Thread Starter
iTrader: (61)
 
Braineack's Avatar
 
Join Date: May 2005
Location: Chantilly, VA
Posts: 72,900
Total Cats: 1,792
Default

the tires weren't that bad. i just blamed it on them, both videos were on RT-215s, they weren't even at the wear bars, but were old, the second video they were still new.

my probably is my power output, I really hated the unpredictably with the rear bar. I blame my pole incident on it. It's only going to get worse once I put a smaller turbo on next week.

Playing with Shaikh's camber curves tools, it really looks like i need that alignment i quoted above (-2.5F and -2.2R). I also seem to have coilover sleeves and 550/300 springs on their way to me. Once I fit them I might try the stock bar again, if I can find it. I think I at least have a FM bar that i can put on the softest setting.
Braineack is offline   Reply With Quote
Old 07-27-2009, 05:02 PM   #19
meatbag
iTrader: (50)
 
gospeed81's Avatar
 
Join Date: Nov 2008
Location: Houston, TX
Posts: 7,357
Total Cats: 26
Default

I just finished throwing in Konis and 450/300 springs yesterday. I have a 7/8" front and the stock rear.

Like Scott I'm just a little tail happy, but manageable, which is good for me to prevent grenading 6" diff. I'm biased since I despise understeer, and learned on oversteer machines (83 Celica, 80 Corolla, 92 240).
gospeed81 is offline   Reply With Quote
Old 07-27-2009, 05:19 PM   #20
Senior Member
iTrader: (4)
 
Join Date: Jan 2008
Location: Falls Church, VA
Posts: 1,367
Total Cats: 16
Default

Quote:
Originally Posted by Braineack View Post
...I really hated the unpredictably with the rear bar. I blame my pole incident on it.
Yeah but didn't that happen in, like, February? On a wet road? I'd blame it more on a cold/wet road and cold tires, and maybe a bit on the driver (sorry man ), than on the presence of a rear sway bar. Many years ago through the snake at VIR, I spun the *** end of dad's RX-7 around on a wet track, and the car was not inherently oversteery to begin with. Granted, the bar reduces the compliance of the rear suspension. But cold/wet road + cold tires = low traction, if the turbo spools up in the middle of a corner you will break traction and the *** end will go around. If you set up your suspension based on your experience in poor road conditions, it's going to understeer just as soon as the weather warms up.

You will enjoy the new springs. Any idea what kind of ride height you'll have to run in order to get -2.5° of front camber? Methinks pretty low but I haven't tried. Other random thought- the FM rear bar is pretty damn stiff even on the softest setting.
ScottFW is offline   Reply With Quote
 
 
Reply

Related Topics
Thread Thread Starter Forum Replies Last Post
Project Gemini - Turbo Civic on the Cheap Full_Tilt_Boogie Build Threads 59 12-15-2017 09:00 PM
1994 Spec Miata Race Car SM/SM2/SSM For Sale Quinn Cars for sale/trade 6 10-23-2016 08:58 AM
Hey everyone another n00b here Big_gumby Meet and Greet 80 10-05-2015 05:06 PM
3rd Time's a Charm...hopefully. zephyrusaurai Meet and Greet 2 09-28-2015 11:59 PM


Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off



All times are GMT -4. The time now is 02:05 PM.