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Discussion Starter · #1 ·
A long read for those who dare. Setting up the DD for best tire wear and MPG. I drive allot!

In another thread I posed the question about track width as I saw my rear wheels were pointed just inside of the front wheels tread when front wheels were straight ahead. http://forum.mazda6club.com/suspens...idth-front-vs-rear-front-wider-than-back.html Seeings that I hadn’t seen the track width listed I was hoping the front was wider but it’s not and I know all my wheels are the same width and offset. From this, I know the TOE is toed –in based upon how it drives. My guess is the REAR is more at fault than the front.
Here is some support evidence:

1) Owners manual lists the track width as being the same front and rear.
2) Sighting down sidewall of Rear tires they are equally aimed inward on the front wheels tire tread.
3) The car rolls forward easier than it does backwards (by hand pushing).
4) The car coasts further when its wet out than it does when it dry out. Tires slip easier in the wet.
5) When driving and the rear end (either one side or both) hits a slippery spot, I feel the car nudge over.
Those are some tell tail signs that it needs the rear alignment corrected. From that I have this question: For a daily driver with 18” 225/40 tires running -0.75 deg camber (Rear), what is the ideal toe-in that counteracts the Negative camber but isn’t so Toed-in so as to scrub the tires or impair the MPG? Also, car is new to me as of 2012-09-01 with NEW tires; they still had tits on them when I bought it. Mostly highway miles but also occasional spirited runs into the twisties!

WEAR:
I’m currently showing wear on the front and rears in this manor: 0 = no wear / 5 = Extreme wear
Fronts inner = 3.5, middle =0, outer = 1.5 Toe and camber are unknown at this point. Pressure was 36PSI. Corrected to 41 psi.

Rear inner = 2, middle =0, outer = 1 Toe and camber are unknown at this point. Pressure was 34PSI. Corrected to 37 psi.

I string aligned my 95 Camry which has near 0.0 deg Camber on both axles using a string and tape measure setting the rear toe to Zero and the Front Toe to +1/16 and got 65,000 from a set of 225/50R17s. The 6 has negative camber at both ends and likely needs a little toe-in to offset this.

Also, does anyone know what size the rear adjusting sleeve and Jamb nuts are for making Toe-Adjustments?

Factory info:
==============================
I'll want it tighter than the +/- setting they give but will ADJUST AS NEEDED based upon Tire Wear observed!

3.0 V6 5DHB
Left to right wheel well height within 10mm (0.40")

Front Camber: -0.17 deg +/-1.0 deg
Front Caster: 3.40 deg +/-1.0 deg
Front Total Toe Tire: 2.0 mm +/-4.0 mm (0.08" +/-0.16")
Front Total Toe RIM: 1.4 mm +/-2.8 mm (0.06" +/-0.12")

Front Toe Adjustment NOTE: 1 revolution = 0 deg 36' ~ 0.24" at the wheel
Front Toe jamb nut tq: 51 - 72 Ft/lbs

**
Rear Camber: -1.08 deg +/-1.0 deg (I'll be shooting for -0.75 deg
Rear Total Toe Tire: 2.0 mm +/-4.0 mm (0.08" +/-0.16")
Rear Total Toe RIM: 1.4 mm +/-2.8 mm (0.06" +/-0.12")

Rear Toe Adjustment NOTE: 1 revolution = 0 deg 43' ~ 0.28" at the wheel

Rear Cam nut Torque: 64 - 86 Ft/lbs
Rear Toe jamb nut tq: 51 - 72 Ft/lbs
==============================

PRESSURE:
Also, what tire pressure are people using front and rear for 225/40R18 on 18 X 8"?? As said, until alignment is fixed, 41psi Front, 37 PSI rear based upon wear. No observable change in DD from pressure bump.

Thanks in advance!
@KevinK2
@CanyonRider
@Final Impact < Easier to find my threads!!
 

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Is there a reason not to check the alignment on a trusted Hunter machine?

There is one more qualitative roll test to check for toe problems. For each case, check whether the tire sidewall is being pulled out, or pulled in toward the center of the car.

Find a place to park the car, with enough slope for the car to roll down if the car is in neutral, but just enough slope to do it. Do the same thing in each direction: Bring the car into the slot with light braking, in gear, then turn off the ignition. The forward test should result in the rear tire sidewalls being pulled in, and the fronts a bit too. The revese test should have the opposite results.


In brief, set the alignment to what you had on your Camery. The apparent excessive rear toe-in could be causing low mpg's.

I made a reference in the 1st page of this thread that the lower the aspect ratio ( with larger dia wheels ), the less agressive you should be on all alignment settings. Here is a reference table from my Rx7 racing days, from the Pettit Racing Co.







This is the Pettit page where the table is located: http://www.pettitracing.com/gen-info/#respond I was happy to do business with these guys ( I thing Jeff was the parts guy ). The main man "Cam" made an appearance at the Summit Point Raceway during a 3rd gen Rx7 meet, and took some very fast laps with his own 3 rotor (oem is 2 rotor) engine'd Rx7 turbo, boosted to just 10 psi.


Notice the low settings for the street use with 18" wheels. I think that's where you should be.

To your question about using toe to compensate for camber ... it doesn't work that way, you just add more squirming of the contact patch.

.
 

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Discussion Starter · #3 ·
In short, offset the negative camber (inner tire wear) by burying it into the corners, increased tire pressure, and rotation intervals?
For MPG = Zero Toe front and back.
For tire life the more Neg the camber perhaps a bit of toe-in but not to exceed 0.06".

I'll play with it and see what kind of life I can get from the tires.

Thanks!
 

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"For tire life the more Neg the camber"

Sorry if I mislead you. You want to get rid of all neg camber, even at the front.

There should be very little neg-camber up front. Easy to measure as you noted, with a plumb bob string, a ruler, and a calculator.

You should be able to reduce the tire pressure to a few psi above the placard pressure recommended for the 18's.(there was a thread about 18" pressure spec's).

I think once you get rid of the excessive rear toe-in, as I did on another car, you will feel how nicely the car glides along the road.

On a last note, make sure the brakes are not dragging because of a messed up caliper bore or piston.

.
 

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Where are you doing all this driving, and what's the driving style? It seems to me that those are both equally important considerations as highest mileage specs.

You're gonna get different specs for high mileage if your ripping through twisties with attitude than you will for a highway star.

So, where & how do you rack up those miles?
 
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Discussion Starter · #6 ·
"For tire life the more Neg the camber"

Sorry if I mislead you. You want to get rid of all neg camber, even at the front.

There should be very little neg-camber up front. Easy to measure as you noted, with a plumb bob string, a ruler, and a calculator.

You should be able to reduce the tire pressure to a few psi above the placard pressure recommended for the 18's.(there was a thread about 18" pressure spec's).

I think once you get rid of the excessive rear toe-in, as I did on another car, you will feel how nicely the car glides along the road.

On a last note, make sure the brakes are not dragging because of a messed up caliper bore or piston.

.
Call me greedy as I like how it drives so I'm not wanting to shed it of all negative cam but retain the best of all things! The back sticks just enough the to get a uniform drift on some round abouts, freeway entrances, but doesn't come around in the twistys when pushed in hard. The Tires are sipped, (never had a set with this) and its quite impressive how well it sticks for being such a fatty.

I've looked trying to find 225/40R18 load tables, very hard to find and the tires are not stock so sizing so no placard listing or info from the "theTireGuy" listing.

Brakes are good, but thanks, no drag there. I think this was taken out of context "For tire life the more Neg the camber perhaps a bit of toe-in but not to exceed 0.06"." No worries - I think we are on the same page.

Thanks for your input. Now to get under it and dial it in a tad.
 

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Discussion Starter · #7 ·
Is there a reason not to check the alignment on a trusted Hunter machine?
As for this; I've talked to 3 different alignment shops and was not impressed. Two of them went by the book and specifically said if its in spec, the thrust angle is good and the wheel is straight, not gonna touch it. AND WE KNOW WHAT THAT MEANS! :(

An independent was just a [email protected] as if I insulted him. Adding to that I'm cheap! lol
 

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Discussion Starter · #8 ·
I live out in the sticks a few miles from here are some very fun roads here. Like back to back sharp S curves winding up the hill, switch backs and mile upon mile of "entertainment". Perhaps why I have a street bike!!! To the north about 40 miles away a place called Wind River Rd in WA. Google it - its street bike heaven and very fun in a car. But the fact is, its my DD driver and does 50 miles daily on the freeway.
 

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I've looked trying to find 225/40R18 load tables, very hard to find and the tires are not stock so sizing so no placard listing or info from the "theTireGuy" listing.
You don't really need the tables. You just need to read the load rating off the tire directly .... 89Y, 92H, 93Z for example, the number gives load rating and letter gives speed ratings. The placard info (or fuel box door) gives the maximum load and speed rating for the oem tires. You can use the posted tire ratings on the car, and compare it to what's on the special 18's. Just make sure what's on the tire is greater than the stamped values on the chassis.


I live out in the sticks a few miles from here are some very fun roads here. Like back to back sharp S curves winding up the hill, switch backs and mile upon mile of "entertainment" ..... But the fact is, its my DD driver and does 50 miles daily on the freeway
Understood. Put about .04"-.06" total toe-in up front to quicken the steering response. And just use the street settings from the table, ignoring the listed caster setting.

.
 

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Discussion Starter · #10 ·
To lazy to go look in down pour but the tires are Federal Steel 595, 225/40/ZR18 88W puts the Max Load at 1235 lbs per tire @ 44psi. While i'm here, that W gives them a speed rating of 168 mph (up there w/exotic cars lol), tire weighs 25.1 lbs!!! Damn!

Tire Tech Information - How to Read Speed Rating, Load Index & Service Descriptions
Lots of info at this site. You should take a look.


More if someone cant sleep.. .. ..
Tire Tech Information - Air Pressure/Load Adjustment for High Speed Driving
Tire Tech Information - Alignment

Heck, all this stuff is there. Looks well done too.
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"To lazy to go look in down pour but the tires are Federal Steel 595, 225/40/ZR18 88W puts the Max Load at 1235 lbs per tire @ 44psi. While i'm here, that W gives them a speed rating of 168 mph..."

Actually, the tire realizes it's max load capacity at 35psi. Adding more pressure up to 44psi improves high speed performance, and normal speed handling, if done correctly.

.
 

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Discussion Starter · #12 ·
"tires are Federal Steel 595, 225/40/ZR18 88W puts the Max Load at 1235 lbs per tire @ 44psi."

Actually, the tire realizes it's max load capacity at 35psi. Adding more pressure up to 44psi improves high speed performance, and normal speed handling, if done correctly.

.
Ok - how did you extract that from the info given when the manuf spec has it at 44psi? Although it makes sense cause at 168mph the deflections per second would be some crazy number for a 25" dia tire so it would build heat pretty quick. Like I said, I bumped the ##s higher to reduce edge wear until the alignment is corrected. Still not at 44 on either end tho. Sadly I've found that my faithful gauge reads 3.5psi low compared to another - so I may be to blame for under-inflation. :( I only mention this is its not the only ride showing edge wear on both edges which indicates low pressure. It has been sent to the dumpster! :mellow:
 

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Discussion Starter · #14 ·
Nice: 88 is the bare min for this vehicle and thats what it has. The times I've checked the temps, there is no elevation on the fronts but I see what you're saying about 35psi. Assuming published info is correct; the tire branded is 44 is of no value. Copy that.
 

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Discussion Starter · #16 ·
It's been below freezing for the past few weeks and seeing my tires gettin eaten was bothering me.

Its a 25" OD tire and I strung a tape between the leading and trailing edges of both axle sets to see where the toe was. A 1/16" up front and 5/32" out back just as it looked and felt.

4 days later had it up on the lift for the actual numbers. All in degrees.
AS FOUND is BLACK! AS LEFT IS BLUE!

FRONT:
CAMBER:
L: - - - - R:
-0.4 _ _ -0.4

CASTER:
4.7 _ _ 4.3

TOE:
0.0 _ _ _ 0.15 = Total = 0.15
0.05 _ _ _ 0.05 = Total = 0.10

REAR:
CAMBER:
L: - - - - R:
-1.5 _ _ -1.8
-1.5 _ _ -1.5

TOE:
0.0 _ _ _ 0.30 = Total = 0.30
0.05 _ _ _ 0.05 = Total = 0.10

Now when the tail hits slippery or different transitional sections it no longer bumps the car sideways and tends to be far less twitchy in the rutted freeway grooves. Also it drove straight then and it drives straight even with the Caster difference. Caster is not huge factor in tire wear so I don't care as long as it drives straight and it does.

Lastly: the camber on the nose showed measure error before as the before/after changed. Again - measurement error as no changes were made to that setting.

And yes, the car ROLLS further than it did before coasting longer. Tire scrub matters!
 
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