5 degrees of caster on a depowered rack - 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 03-18-2013, 11:14 PM   #1
Senior Member
Thread Starter
iTrader: (6)
 
Join Date: Jun 2010
Location: San Rafael, CA
Posts: 1,124
Total Cats: 41
Default 5 degrees of caster on a depowered rack

I had my car aligned with the new NB sub-frame last week. I went over all the alignment specs with the shop (TFB Awesome!). We forgot to talk about caster so he set it at 5 degrees. By conventional miataturbo wisdom it should be set at 3.5 degrees. I was surprised to find steering was great and effort was reasonable at 5 degrees. It maybe because I gutted the rack or because the steering wheel is closer to my body than a street car.

Just wanted to share the results. The extra caster helps with camber gain and has great feedback on the track.
k24madness is offline   Reply With Quote
Old 03-18-2013, 11:55 PM   #2
Tour de Franzia
iTrader: (6)
 
hustler's Avatar
 
Join Date: Jun 2006
Location: Republic of Dallas
Posts: 29,114
Total Cats: 351
Default

5 degrees is the way.
hustler is offline   Reply With Quote
Old 03-19-2013, 12:40 AM   #3
Supporting Vendor
iTrader: (31)
 
Savington's Avatar
 
Join Date: Nov 2006
Location: Sunnyvale, CA
Posts: 14,353
Total Cats: 1,322
Default

5 works, but the steering has noticeably less effort at 3.5 and is generally less tiring to drive.
Savington is online now   Reply With Quote
Old 03-19-2013, 12:52 AM   #4
Tour de Franzia
iTrader: (6)
 
hustler's Avatar
 
Join Date: Jun 2006
Location: Republic of Dallas
Posts: 29,114
Total Cats: 351
Default

Quote:
Originally Posted by Savington View Post
5 works, but the steering has noticeably less effort at 3.5 and is generally less tiring to drive.
Attached Thumbnails
5 degrees of caster on a depowered rack-img_0686.jpg   5 degrees of caster on a depowered rack-img_1021-640x250.jpg  
hustler is offline   Reply With Quote
Old 03-19-2013, 02:53 AM   #5
Senior Member
Thread Starter
iTrader: (6)
 
Join Date: Jun 2010
Location: San Rafael, CA
Posts: 1,124
Total Cats: 41
Default

Quote:
Originally Posted by Savington View Post
5 works, but the steering has noticeably less effort at 3.5 and is generally less tiring to drive.
No doubt that 3.5 is easier than 5 but I was surprised that I never once thought this is tough on track. I assume the additional leverage from the steering wheel being closer and the properly de-powered rack played a role. From all of the bitching I have read about 5 degrees I was expecting a handful.
k24madness is offline   Reply With Quote
Old 03-20-2013, 09:39 PM   #6
Elite Member
iTrader: (12)
 
Join Date: Apr 2008
Location: Springfield IL
Posts: 2,750
Total Cats: 24
Default

Quote:
Originally Posted by hustler View Post
You rack that without blowing your bung out again?
chpmnsws6 is offline   Reply With Quote
Old 03-20-2013, 10:26 PM   #7
Senior Member
 
Join Date: Nov 2010
Location: Pittsburgh PA
Posts: 1,196
Total Cats: 12
Default

Quote:
Originally Posted by Savington View Post
5 works, but the steering has noticeably less effort at 3.5 and is generally less tiring to drive.
THIS


I used about 5* when I had PS. With the "R", and thus a manual box, I started off at 4.5*. A bit stiff to be honest, but not bad. After replacing all the alignment bolts (that's another story) I decided to try out 3.5*. Overall, steering effort is much lower, and low-speed parking can be more easily done with one hand (with the other hand holding open the drivers door, head leaning out the side, lambo-style).


The car feels just as precise as before, just more delicate. YMMV.
2ndGearRubber is offline   Reply With Quote
Old 03-21-2013, 11:20 AM   #8
Junior Member
iTrader: (3)
 
Join Date: Apr 2010
Location: South Bay, CA
Posts: 354
Total Cats: -2
Default

Any doesn't downside handling wise to run less than max caster?
comradefks is offline   Reply With Quote
Old 03-21-2013, 11:32 AM   #9
Senior Member
Thread Starter
iTrader: (6)
 
Join Date: Jun 2010
Location: San Rafael, CA
Posts: 1,124
Total Cats: 41
Default

Let's talk about the upside of running higher caster numbers. The inverse applies to going the otherway.

Requires less static camber due to better camber gain. Less static camber helps with braking. Returns to on center easier. Jacking effect transfers weight better.

On a "race prepped" track only car you should run as much caster as you can tollerate. I tried 5 degrees by sheer dumb luck. I was expecting the worst. I found it easy to drive. Without a properly depowered rack and good steering wheel position (closer to your body) 5 degrees is likely to much.
k24madness is offline   Reply With Quote
Old 03-21-2013, 09:09 PM   #10
Senior Member
iTrader: (2)
 
Join Date: Oct 2011
Location: SE NM
Posts: 1,458
Total Cats: 48
Default

I got an alignment today to prepare for TWS in a few weeks and I told the guy to give me as much front camber as possible, and then as much caster without affecting camber. It ended up with -1 degree camber and 6 degrees caster. This is a stock suspension 2001. Is this ok or should I go with something different?
Chilicharger665 is offline   Reply With Quote
Old 03-22-2013, 03:32 PM   #11
Junior Member
 
Join Date: Feb 2009
Location: The Woodlands, TX
Posts: 328
Total Cats: 12
Default

Let's see: you're driving it from New Mexico to College Station, TX, and you're going to participate in NASA HPDE 1. Yeah, -1 camber is fine.

Later, when you're driving faster (on the track), you'll want more than -2 to get full use of the tread during hard cornering.
Double O 86 is offline   Reply With Quote
Old 04-04-2013, 07:36 PM   #12
Junior Member
 
Join Date: Mar 2012
Location: Portugal
Posts: 199
Total Cats: -12
Default

I have had my car set up at 4.5 degrees almost since I got it. Steering is effortless and the feel is great! I love it and would reccomend it!

BTW my car is a manual steering one. Not sure if anything would change in comparison to a de-powered rack. Does it?
ThunderFox is offline   Reply With Quote
Old 04-04-2013, 07:43 PM   #13
Elite Member
iTrader: (5)
 
Join Date: Dec 2010
Location: Raleigh, NC
Posts: 1,970
Total Cats: 49
Default

I run 5.5* on a depowered rack. If you run longer stints or do lapping days it may get tiring, but I honestly don't notice it. even we I drove to the track and back.
Seefo is offline   Reply With Quote
Old 04-20-2013, 05:46 PM   #14
Elite Member
 
Join Date: Jul 2005
Location: Anacortes, WA
Posts: 2,476
Total Cats: 114
Default

**** I just aligned my car after installing NB front subframe and V8R arms. Can't get less than about 6 degrees of caster. I wanted less. I have good upper body strength but dam I Can't see what is off so far.
bbundy is offline   Reply With Quote
Old 04-20-2013, 07:07 PM   #15
Elite Member
 
Join Date: Mar 2010
Location: Detroit
Posts: 1,524
Total Cats: 27
Default

I just realigned my car last week, 3 times actually. I went from 4* caster on both sides, to 5* on both sides.

After I got the new wheels/tires installed and lowered the car a 1/2in f&r, I found the car overly twitchy on the freeway. Bumping the caster up to 5* completely fixed that and I really don't notice that much extra effort required to steer it.

I ended up with -1.4* camber/+5* caster on both fronts with very slight toe out. Rear was -1.7* camber with factory toe settings.

I'm very happy with the way it handles now. Feels so planted in corners, especially with those new rivals.
flounder is offline   Reply With Quote
Old 04-21-2013, 02:20 AM   #16
Elite Member
 
Join Date: Jul 2005
Location: Anacortes, WA
Posts: 2,476
Total Cats: 114
Default

Quote:
Originally Posted by bbundy View Post
**** I just aligned my car after installing NB front subframe and V8R arms. Can't get less than about 6 degrees of caster. I wanted less. I have good upper body strength but dam I Can't see what is off so far.
I’m considering shimming the upper arm big bolt to adjust some caster. With Delrin or urethane bushings and the right sizes and combination of washers ” shift will get almost 2 degrees of caster adjustment. I bet you could fiddle with the caster settings that way without having to re set all the other settings too.

Interesting that the NB subfram increases caster by 1 degree over the NA to stock setting of 5.48 degrees. It does this by shifting the tube the for the upper arm big bolt back further before welding it to the subframe.

Last edited by bbundy; 04-21-2013 at 02:34 AM.
bbundy is offline   Reply With Quote
Old 04-21-2013, 03:29 AM   #17
Elite Member
iTrader: (24)
 
kotomile's Avatar
 
Join Date: Oct 2006
Location: Monterey, CA
Posts: 7,578
Total Cats: 40
Default

I thought 5-5.5* was normal? I've had mine aligned that way for years, though if Sav says 3.5 is better on track, I'd probably take his word for it. Driving to work and lapping are different things.

I run 5.5 on a depowered rack, smaller wheel, etc. It's definitely not difficult on the street. If anything, it'll help to pump up all of you pathetic girly men.

kotomile is offline   Reply With Quote
Old 04-21-2013, 03:35 AM   #18
Elite Member
iTrader: (24)
 
kotomile's Avatar
 
Join Date: Oct 2006
Location: Monterey, CA
Posts: 7,578
Total Cats: 40
Default

double post because my computer is shitty like that.

Last edited by kotomile; 04-21-2013 at 03:50 AM.
kotomile is offline   Reply With Quote
Old 04-21-2013, 11:39 AM   #19
Senior Member
Thread Starter
iTrader: (6)
 
Join Date: Jun 2010
Location: San Rafael, CA
Posts: 1,124
Total Cats: 41
Default

Quote:
Originally Posted by bbundy View Post
**** I just aligned my car after installing NB front subframe and V8R arms. Can't get less than about 6 degrees of caster. I wanted less. I have good upper body strength but dam I Can't see what is off so far.
When the shop aligned it did they zero out the V8R camber adjustment? I know caster/camber affect each other on the stock ecentrics so depending on where the camber bolt is set (stock one) it will affect caster range. In your situation I would use stock adjusters to get ideal caster (5 IMHO) and use the V8R outer camber bolt to obtain ideal camber.

My car is in the weeds with a NB front sub frame and 5 degrees caster is achievable.

Last edited by k24madness; 04-21-2013 at 07:45 PM.
k24madness is offline   Reply With Quote
Old 04-22-2013, 03:37 PM   #20
Elite Member
 
Join Date: Jul 2005
Location: Anacortes, WA
Posts: 2,476
Total Cats: 114
Default

Quote:
Originally Posted by k24madness View Post
When the shop aligned it did they zero out the V8R camber adjustment? I know caster/camber affect each other on the stock ecentrics so depending on where the camber bolt is set (stock one) it will affect caster range. In your situation I would use stock adjusters to get ideal caster (5 IMHO) and use the V8R outer camber bolt to obtain ideal camber.

My car is in the weeds with a NB front sub frame and 5 degrees caster is achievable.
Stock lower aft camber bolt is all the way inbord and the forward ones are most of the way outboard. It is pretty much adjusted as little caster is it will get.

FWIW my last setup with the NA-front subframe and stock arms I just told the aignment guy to set all 4 of the front lower adjustments full out and see what it is. the result was 3 degrees of camber and 5.1 caster and that was where I left it.

Bob
bbundy is offline   Reply With Quote
 
 
Reply

Related Topics
Thread Thread Starter Forum Replies Last Post
TunerStudio timining issue - 90 Miata 1.6 Turbo spec1sef MEGAsquirt 28 05-09-2017 08:03 AM
Lots of stuff from my NA BRG partout. Corifto Miata parts for sale/trade 8 10-04-2015 05:30 PM
Odd Steering issue interestedofold Suspension, Brakes, Drivetrain 5 09-29-2015 02:42 PM
Twitchy car (tail happy problem) bigben Race Prep 16 09-11-2015 04:41 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 03:14 PM.