9" 6UL's - Setup issue? - Miata Turbo Forum - Boost cars, acquire cats.

Welcome to Miataturbo.net   Members
 


Race Prep Miata race-only chat.
Sponsored by:
Sponsored by:

Reply
 
 
 
LinkBack Thread Tools Search this Thread
Old 02-13-2014, 09:46 PM   #1
Senior Member
Thread Starter
 
Join Date: Dec 2010
Location: Auckland, NZ
Posts: 782
Total Cats: 23
Default 9" 6UL's - Setup issue?

Hi Guys

This is for the guys who have race/autocross experience with the 9" 6UL or similar....

In swtiching to the 9" rim from the 7" rim my lap times have improved by 1-2 seconds at various tracks. So overall I am very pleased.

However, I believe a consequence of this change is a strange/new handling problem....

On corner entry, If i turn the wheel beyond a mild turn in (i.e for a slower/tighter corner) I get a really nice hard turn in but as the steering wheel gets to a certain point the rear end just lets go and the car starts to spin....

It "feels" to me that it is somethting like when you turn the wheel in a Kart how the chassis jacks up...by design in a Kart.

I can drive around the problem but wonder if there is a different caster/camber setting you guys use for the wider wheels...i have pretty much tried to adhere to the suggested 949racing specs at this point.

One of more experienced guys here wonders if it is related to the wheel extending in beyond the lower ball joint and it changing the geometry as you turn in more and more....along the lines of my kart analogy above..

Can anyone help, make suggestions based on experience?
mx5-kiwi is offline   Reply With Quote
Old 02-13-2014, 10:23 PM   #2
Senior Member
iTrader: (6)
 
Join Date: Jun 2010
Location: San Rafael, CA
Posts: 1,124
Total Cats: 41
Default

What are your caster numbers? Increasing castor also increases the jacking effect. Try backing it down some and see what happens.
k24madness is offline   Reply With Quote
Old 02-13-2014, 10:50 PM   #3
Elite Member
iTrader: (1)
 
Leafy's Avatar
 
Join Date: Jun 2012
Location: NH
Posts: 9,091
Total Cats: 90
Default

Making more grip, getting more roll, running out of rear droop travel either because of the rear sway bar binding or the shocks not having enough droop travel. If these koni race shocks are more than a couple years old, they're the old too short in the rear body koni race's and that could be the problem.
Leafy is offline   Reply With Quote
Old 02-13-2014, 11:06 PM   #4
Senior Member
Thread Starter
 
Join Date: Dec 2010
Location: Auckland, NZ
Posts: 782
Total Cats: 23
Default

Aha, thanks guys. Good places too start.

I'll try and find my last alignment chart for the Caster. Is there a different setup generally used with the wider wheel?

These Konis are at least 4-5 years old....can you elaborate a bit on what you said Leafy?
mx5-kiwi is offline   Reply With Quote
Old 02-13-2014, 11:09 PM   #5
Elite Member
iTrader: (1)
 
Leafy's Avatar
 
Join Date: Jun 2012
Location: NH
Posts: 9,091
Total Cats: 90
Default

The common koni setup is race fronts and sport rears, not entirely because of the damping curves, but that the race rears used to be much too short of shocks and didnt have enough droop travel. A couple years someone brought this up to Koni Lee at solo nationals and they fixed it. I cant say for certain that its your problem.
Leafy is offline   Reply With Quote
Old 02-14-2014, 09:23 AM   #6
Junior Member
 
guttedmiata's Avatar
 
Join Date: Sep 2012
Posts: 438
Total Cats: -3
Default

You said nothing about a tire change, so I assume you are stretching the same tires onto a 2" wider wheel. You now have less radial roll. In other words, your side walls cannot flex as much to be forgiving of either over driving or a less than optimal set up. The sidewall flex you had before was masking one or both of these problems. Now with less "forgiveness" you need to make appropriate adjustments. In additional to sharing alignment specs, please also share sway bar and spring info.
guttedmiata is offline   Reply With Quote
Old 02-14-2014, 05:05 PM   #7
Elite Member
iTrader: (5)
 
Join Date: Dec 2010
Location: Raleigh, NC
Posts: 1,970
Total Cats: 49
Default

sounds more like a bumpstop/stiffness/traction issue to me.

I think most suspension geometry is calculated with reference to the contact patch centerline. I think there is slightly difference between offset from the 7" and 9", but probably not enough to have a significant issue.
Seefo is offline   Reply With Quote
Old 02-15-2014, 01:39 AM   #8
Junior Member
 
Join Date: Apr 2011
Posts: 194
Total Cats: 10
Default

Camber numbers?
oregonmon is offline   Reply With Quote
Old 02-15-2014, 02:38 AM   #9
Senior Member
Thread Starter
 
Join Date: Dec 2010
Location: Auckland, NZ
Posts: 782
Total Cats: 23
Default

Oddly, just got back from a track day at a different track (home base) and it is less of a problem...in fact it is almost a benefit as it helps the car turn in a bit better (almost karting style)...at this track..Hampton Downs. Some off camber corners and down hill off camber etc..Long sweeper can use the "kick" to get the rear to come out a bit when required....as well as throttle.

At the A1 Taupo track the corners must be slightly slower/tighter and it was a hinderence...

Re the tyres, I have only used the 225 on the 9" previously I had 205 on a 7"...

Okay found the last wheel alignment sheet...

Toe front Ttl +0.3mm Lft Fr 0.00 Rt Fr +0.3

Camber Frt Lft Fr -02.30' Rt Fr -02.47'

Caster Frt Lft Fr +03.26' Rt Fr +5.44'

Toe rear Ttl +5.2mm Lft Rr +2.70mm Rt Rr +2.4mm

Camber Rear Lft Rr -02.37 rt rr -02.29'

One of my alignment cam bolts is worn/screwed so he had problems with it...have been meaning to order new ones but keep forgetting...not sure which one now...

Sway bars are Whiteline.

24mm front mid setting of 3
16mm Rear soft setting of 2
mx5-kiwi is offline   Reply With Quote
Old 02-15-2014, 02:40 AM   #10
Senior Member
Thread Starter
 
Join Date: Dec 2010
Location: Auckland, NZ
Posts: 782
Total Cats: 23
Default

Just to clarify, the 9" with 225 was/is worth 1.5 - 2 seconds per lap at most tracks...so overall there is a huge improvement from the 7" 205 combo....
mx5-kiwi is offline   Reply With Quote
Old 02-15-2014, 10:02 AM   #11
Elite Member
iTrader: (5)
 
Join Date: Dec 2010
Location: Raleigh, NC
Posts: 1,970
Total Cats: 49
Default

Quote:
Originally Posted by mx5-kiwi View Post
Oddly, just got back from a track day at a different track (home base) and it is less of a problem...in fact it is almost a benefit as it helps the car turn in a bit better (almost karting style)...at this track..Hampton Downs. Some off camber corners and down hill off camber etc..Long sweeper can use the "kick" to get the rear to come out a bit when required....as well as throttle.

At the A1 Taupo track the corners must be slightly slower/tighter and it was a hinderence...

Re the tyres, I have only used the 225 on the 9" previously I had 205 on a 7"...

Okay found the last wheel alignment sheet...

Toe front Ttl +0.3mm Lft Fr 0.00 Rt Fr +0.3

Camber Frt Lft Fr -02.30' Rt Fr -02.47'

Caster Frt Lft Fr +03.26' Rt Fr +5.44'

Toe rear Ttl +5.2mm Lft Rr +2.70mm Rt Rr +2.4mm

Camber Rear Lft Rr -02.37 rt rr -02.29'

One of my alignment cam bolts is worn/screwed so he had problems with it...have been meaning to order new ones but keep forgetting...not sure which one now...

Sway bars are Whiteline.

24mm front mid setting of 3
16mm Rear soft setting of 2
in bold either looks suspect, or awful. not sure how balanced the sway bars would be with 10k/6k springs... I would put that in a suspension calculator and aim for 60% FRC range. that should put you close and do the fine tuning with the sway bars, shock adjust and possibly tire PSI if you have to.

fixing the difference in caster probably won't fix your problem, but caster is important as it has an effect on dynamic camber.

Rear Toe...I don't know, I am not used to seeing alignment in mm, but that is just too much. 5.2mm ~ 1/5"...and that is in toe out? probably the problem right there.
Seefo is offline   Reply With Quote
Old 02-15-2014, 12:51 PM   #12
Senior Member
iTrader: (1)
 
Join Date: Nov 2010
Posts: 951
Total Cats: -252
Default

I'd drop down to the 14mm Mazdaspeed rear swaybar or jump up to the Racing Beat Large Race front swaybar.
wannafbody is offline   Reply With Quote
Old 02-15-2014, 06:54 PM   #13
Elite Member
iTrader: (24)
 
Join Date: Jun 2007
Location: Sherman Oaks, CA
Posts: 4,480
Total Cats: 3
Default

Disconnect your rear sway bar for 1 session and see if it improves anything.
UrbanSoot is online now   Reply With Quote
Old 02-16-2014, 02:31 AM   #14
Junior Member
 
Join Date: Apr 2011
Posts: 194
Total Cats: 10
Default

Quote:
Originally Posted by Track View Post

in bold either looks suspect, or awful. not sure how balanced the sway bars would be with 10k/6k springs... I would put that in a suspension calculator and aim for 60% FRC range. that should put you close and do the fine tuning with the sway bars, shock adjust and possibly tire PSI if you have to.

fixing the difference in caster probably won't fix your problem, but caster is important as it has an effect on dynamic camber.

Rear Toe...I don't know, I am not used to seeing alignment in mm, but that is just too much. 5.2mm ~ 1/5"...and that is in toe out? probably the problem right there.
That's total toe though. So it sounds like about .10"-11" each side. Which is around 1/16" give or take. So that should be fine right? The caster needs to be equalized, was this with you or ballast in the car?
I think you should probably shoot for more front camber by maybe a 1/2 degree than the rear from what I've seen recommended.
Also your front toe should be even as well.
oregonmon is offline   Reply With Quote
Old 02-16-2014, 07:24 AM   #15
Senior Member
iTrader: (3)
 
Join Date: Jun 2008
Location: Port Orchard, WA
Posts: 620
Total Cats: 4
Default

Quote:
Originally Posted by oregonmon View Post
That's total toe though. So it sounds like about .10"-11" each side. Which is around 1/16" give or take. So that should be fine right? The caster needs to be equalized, was this with you or ballast in the car?
I think you should probably shoot for more front camber by maybe a 1/2 degree than the rear from what I've seen recommended.
Also your front toe should be even as well.
1/16" = .0625"... he's closer to 1/8" per side which is way too much. 1/8" total is the max 949 recommends. IMO he needs to have a shop do the alignment a little more carefully, and with him (or his weight) in the drivers seat (if he wasn't). The numbers should be quite a bit closer than that side to side.
Rennkafer is offline   Reply With Quote
Old 02-16-2014, 01:27 PM   #16
Elite Member
iTrader: (5)
 
Join Date: Dec 2010
Location: Raleigh, NC
Posts: 1,970
Total Cats: 49
Default

Quote:
Originally Posted by oregonmon View Post
That's total toe though. So it sounds like about .10"-11" each side. Which is around 1/16" give or take. So that should be fine right? The caster needs to be equalized, was this with you or ballast in the car?
I think you should probably shoot for more front camber by maybe a 1/2 degree than the rear from what I've seen recommended.
Also your front toe should be even as well.
1/5 divided out is 1/10 per side really. I think 1mm on each side is probably just fine. toe out is nice to have, but definitely not in large amounts...especially if you like your tires. At least he can turn it down to see if it has an effect. Just a suggestion.
Seefo is offline   Reply With Quote
Old 02-16-2014, 01:31 PM   #17
Junior Member
 
Join Date: Apr 2011
Posts: 194
Total Cats: 10
Default

Quote:
Originally Posted by Rennkafer View Post
1/16" = .0625"... he's closer to 1/8" per side which is way too much. 1/8" total is the max 949 recommends. IMO he needs to have a shop do the alignment a little more carefully, and with him (or his weight) in the drivers seat (if he wasn't). The numbers should be quite a bit closer than that side to side.
Ewww, your right.
oregonmon is offline   Reply With Quote
Old 02-18-2014, 05:23 PM   #18
Supporting Vendor
iTrader: (31)
 
Savington's Avatar
 
Join Date: Nov 2006
Location: Sunnyvale, CA
Posts: 14,353
Total Cats: 1,319
Default

Your front sway is too small, rear sway is too large, and you have too much rear camber/not enough front camber.
Savington is offline   Reply With Quote
Old 02-18-2014, 08:33 PM   #19
Elite Member
 
Join Date: Jul 2007
Location: Little Rock, AR
Posts: 3,109
Total Cats: 127
Default

I think the first thing I would try would be the stiffest hole on the front sway and more front camber. Then if you want less tail happy then that switch to the stock rear bar.
jacob300zx is offline   Reply With Quote
Old 02-19-2014, 12:58 AM   #20
Supporting Vendor
iTrader: (3)
 
emilio700's Avatar
 
Join Date: May 2005
Posts: 5,308
Total Cats: 1,326
Default

Quote:
Originally Posted by Savington View Post
Your front sway is too small, rear sway is too large, and you have too much rear camber/not enough front camber.
This.
emilio700 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 57 07-19-2017 05:11 PM
WTB MP62 (Hotside) (NB2) Rick02R WTB 3 01-03-2016 08:18 PM
Leaky Wilwoods mx592 Suspension, Brakes, Drivetrain 1 10-01-2015 01:45 AM
Low oil pressure after 1.8 swap and new turbo setup JesseTheNoob DIY Turbo Discussion 15 09-30-2015 03:44 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 10:38 PM.