rear toe
12-30-2006, 05:04 PM
#1
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rear toe
The guys at the tire shop where I have alignment done can't seem to figure out the difference between toe in degrees and toe in in inches. I requested 1/4" toe in in the rear and their final printout says .25 degrees. They say it is the same, I say they are not.
Anyone know what 1/4" toe in degrees would be?
Anyone know what 1/4" toe in degrees would be?
12-30-2006, 08:00 PM
#2
Melting Slicks
The guys at the tire shop where I have alignment done can't seem to figure out the difference between toe in degrees and toe in in inches. I requested 1/4" toe in in the rear and their final printout says .25 degrees. They say it is the same, I say they are not.
Anyone know what 1/4" toe in degrees would be?
Anyone know what 1/4" toe in degrees would be?
I am not a geometry major, but I know the relationship is not linear......I believe however on your sized wheels that 1/4 degree = half of that number in inches or roughly 1/8". I dont know what kind of machine your shop was using, but if it was a Hunter , I know they could have immediately converted their measurements if they knew how to completely use their machine.
I always like to look at toe in inches, it makes it easier for my feeble brain
12-30-2006, 10:14 PM
#3
Pretty much what Raftracer said, almost 1/8" toe (.125").
.25 degrees comes up to .111" on a 25.6" tire. Great if that is how much each rear wheel is toed in, not so good if that is the total number.
.25 degrees comes up to .111" on a 25.6" tire. Great if that is how much each rear wheel is toed in, not so good if that is the total number.
12-30-2006, 10:27 PM
#4
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I think the guy running the machine this time screwed up.
He set the total toe to .25 degrees and told me it was .25 inches.
The sheet says the toe was .86 degrees before he changed it which may have been the previous alignment of 1/4 inch.
No problem, I'll just take it back and they will redo it. One guy that works there tracks a Miata with a small block in it, that has good to be a hoot. Their rack has no ramp which suits my car as my splitter sits about 2" high.
So back to toe, do I tell them 1/4" total toe in or 1/4" each wheel?
He set the total toe to .25 degrees and told me it was .25 inches.
The sheet says the toe was .86 degrees before he changed it which may have been the previous alignment of 1/4 inch.
No problem, I'll just take it back and they will redo it. One guy that works there tracks a Miata with a small block in it, that has good to be a hoot. Their rack has no ramp which suits my car as my splitter sits about 2" high.
So back to toe, do I tell them 1/4" total toe in or 1/4" each wheel?
12-30-2006, 11:45 PM
#5
Burning Brakes
What car?
1/4" toe (1 side) is 0.55 degrees
3/16" per side is 0.41 degrees, so close to what you had at 0.86 total
I ran 3/8" total (3/16" per side) on my Z06 in Super Stock. 1/4" per side (1/2" total) is quite a bit but not unheard of for Solo. It WILL destroy your tires on the street.
BTW, at 3/16" per side, it is right about 1 full turn of the adjusters from that setting back to zero toe. This allowed me to set the toe back to zero for street driving.
1/4" toe (1 side) is 0.55 degrees
3/16" per side is 0.41 degrees, so close to what you had at 0.86 total
I ran 3/8" total (3/16" per side) on my Z06 in Super Stock. 1/4" per side (1/2" total) is quite a bit but not unheard of for Solo. It WILL destroy your tires on the street.
BTW, at 3/16" per side, it is right about 1 full turn of the adjusters from that setting back to zero toe. This allowed me to set the toe back to zero for street driving.
12-31-2006, 01:29 AM
#6
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What car?
1/4" toe (1 side) is 0.55 degrees
3/16" per side is 0.41 degrees, so close to what you had at 0.86 total
I ran 3/8" total (3/16" per side) on my Z06 in Super Stock. 1/4" per side (1/2" total) is quite a bit but not unheard of for Solo. It WILL destroy your tires on the street.
BTW, at 3/16" per side, it is right about 1 full turn of the adjusters from that setting back to zero toe. This allowed me to set the toe back to zero for street driving.
1/4" toe (1 side) is 0.55 degrees
3/16" per side is 0.41 degrees, so close to what you had at 0.86 total
I ran 3/8" total (3/16" per side) on my Z06 in Super Stock. 1/4" per side (1/2" total) is quite a bit but not unheard of for Solo. It WILL destroy your tires on the street.
BTW, at 3/16" per side, it is right about 1 full turn of the adjusters from that setting back to zero toe. This allowed me to set the toe back to zero for street driving.
Last edited by danswofford; 12-31-2006 at 01:32 AM.
12-31-2006, 02:19 AM
#7
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To change from degrees to inches you need to measure the length (lets call it B) of the line on the face of the wheel from where you measure the distance across the rear of the tires and where you measure across the front of the tires.
The measurent in inches of the amount of toe = B * Sin (the angle).
So for a .5 degree toe in (the angle) across a wheel that is 14.5 inches across the face (B) = .1243 inches difference from rear to front with the front measurement being smaller than the rear. That is almost an 1/8 of an inch.
Bill
The measurent in inches of the amount of toe = B * Sin (the angle).
So for a .5 degree toe in (the angle) across a wheel that is 14.5 inches across the face (B) = .1243 inches difference from rear to front with the front measurement being smaller than the rear. That is almost an 1/8 of an inch.
Bill
12-31-2006, 06:48 AM
#8
To change from degrees to inches you need to measure the length (lets call it B) of the line on the face of the wheel from where you measure the distance across the rear of the tires and where you measure across the front of the tires.
The measurent in inches of the amount of toe = B * Sin (the angle).
So for a .5 degree toe in (the angle) across a wheel that is 14.5 inches across the face (B) = .1243 inches difference from rear to front with the front measurement being smaller than the rear. That is almost an 1/8 of an inch.
Bill
The measurent in inches of the amount of toe = B * Sin (the angle).
So for a .5 degree toe in (the angle) across a wheel that is 14.5 inches across the face (B) = .1243 inches difference from rear to front with the front measurement being smaller than the rear. That is almost an 1/8 of an inch.
Bill
Also, the tire shops typically use 12" for the "B" distance, but you can just use 24" for the total toe.
So, for 1/4" total toe in (B=24):
angle = invsin (toe/B)
= invsin (.25/24)
= .6 degrees
Also, "toe in" is a positive angle, "toe out" is a negative angle.
Dave G.
12-31-2006, 09:06 AM
#9
Race Director
I'm surprised it took so many postes to reach 9th grade math level.
I use 18" as my diameter, as I measure at the edge of the rim.
sin (angle) = .125/18 (.125 per wheel = .25 total)
angle=0.4 deg for each wheel , 0.8deg total for .25 total toe
They basically put on 1/3 as much toe as you want. You basically need an additional bit of toe, but not too much. You need another 3/16" toe, so I'd just loosen each rear toe-link 2 "flats". 1 Flat=1/6 turn, so turn each adjuster 1/3 of a turn.
** I'm not contradicting talon's math, I just use a slightly different diameter number***
I use 18" as my diameter, as I measure at the edge of the rim.
sin (angle) = .125/18 (.125 per wheel = .25 total)
angle=0.4 deg for each wheel , 0.8deg total for .25 total toe
They basically put on 1/3 as much toe as you want. You basically need an additional bit of toe, but not too much. You need another 3/16" toe, so I'd just loosen each rear toe-link 2 "flats". 1 Flat=1/6 turn, so turn each adjuster 1/3 of a turn.
** I'm not contradicting talon's math, I just use a slightly different diameter number***
Last edited by davidfarmer; 12-31-2006 at 10:17 AM.
12-31-2006, 10:16 AM
#10
Race Director
btw, the guy just didn't know any better. Most people barely remember elementary school math, let alone geometry.
You should download my DIY alignment guide and do it yourself anyway
see this thread for more info
http://forums.corvetteforum.com/show...ight=alignment
You should download my DIY alignment guide and do it yourself anyway
see this thread for more info
http://forums.corvetteforum.com/show...ight=alignment
12-31-2006, 12:51 PM
#11
I agree. The best way to do this is just have the alignment shop set to zero toe and then adjust it yourself. Toe plates are cheap and fairly accurate.
As also suggested above, you can just turn each tie rod a specific amount (like 1/2 turn, 1 turn, etc...) and get it close as long as you know where you're starting (like zero).
On my car 1 1/4 turns on both sides gets very close to .5" total toe (measured at ~24" distance) when starting at zero toe.
When comparing toe settings in inches, that distance is critical though obviously. .5" total for me will only be .375" to David Farmer.
(18/24) * .5 = .375 (similar triangles for you math dudes)
Dave G.
As also suggested above, you can just turn each tie rod a specific amount (like 1/2 turn, 1 turn, etc...) and get it close as long as you know where you're starting (like zero).
On my car 1 1/4 turns on both sides gets very close to .5" total toe (measured at ~24" distance) when starting at zero toe.
When comparing toe settings in inches, that distance is critical though obviously. .5" total for me will only be .375" to David Farmer.
(18/24) * .5 = .375 (similar triangles for you math dudes)
Dave G.
12-31-2006, 12:54 PM
#12
12-31-2006, 02:20 PM
#13
Race Director
as in my DIY guide above, you can make very accurate, repeatable measurements with nothing but a tape measure and a straight edge. It has gotten me through tons of alignments, including setup on my old World Challenge ride. I haven't trusted an alignment/tire shop in over 10year. They have awesome hardware, but the operators could care less about your car.
12-31-2006, 02:31 PM
#14
Melting Slicks
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OK, I'm going to ask a stupid question now...
When you are setting the toe using toe plates or David's method, how do you know your thrust angle is 0? I know you're supposed to measure from center line, but where, and how, do you determine the centerline? Any tips?
When you are setting the toe using toe plates or David's method, how do you know your thrust angle is 0? I know you're supposed to measure from center line, but where, and how, do you determine the centerline? Any tips?
12-31-2006, 04:33 PM
#15
Race Director
My DIY guide covers thrust angle as well. I use a laser level and some paper guides I made up. If you can get the the measurement within 3/8", you're within OEM tolerance.
**Assuming your car is right to begin with, just do one side at a time. ie, adjust right camber, set right toe. Adjust left camber, adjust left tow. This way, the thrust angle isn't affected.
**Assuming your car is right to begin with, just do one side at a time. ie, adjust right camber, set right toe. Adjust left camber, adjust left tow. This way, the thrust angle isn't affected.
12-31-2006, 06:30 PM
#16
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You're off by a factor of 2 Bill. That equation just gives you the front or rear difference, not both combined.
I was trying to describe the measurement at one wheel and may have made it obtuse without the benefit of a diagram to show what I meant.
Also, the tire shops typically use 12" for the "B" distance, but you can just use 24" for the total toe.
I wasn't sure what a tire shop would use but the B measurement in my description is based on the distance across the face of the wheel where a person is making the toe measurement. If it the measurement is being made on an 18 inch wheel across the center line of the wheel it will be close to 18 inches. If it is made on a line above the center line then it will be less.
So, for 1/4" total toe in (B=24):
angle = invsin (toe/B)
= invsin (.25/24)
= .6 degrees
Also, "toe in" is a positive angle, "toe out" is a negative angle.
I agree.
Dave G.
I was trying to describe the measurement at one wheel and may have made it obtuse without the benefit of a diagram to show what I meant.
Also, the tire shops typically use 12" for the "B" distance, but you can just use 24" for the total toe.
I wasn't sure what a tire shop would use but the B measurement in my description is based on the distance across the face of the wheel where a person is making the toe measurement. If it the measurement is being made on an 18 inch wheel across the center line of the wheel it will be close to 18 inches. If it is made on a line above the center line then it will be less.
So, for 1/4" total toe in (B=24):
angle = invsin (toe/B)
= invsin (.25/24)
= .6 degrees
Also, "toe in" is a positive angle, "toe out" is a negative angle.
I agree.
Dave G.
12-31-2006, 06:39 PM
#17
Bill, probably also didn't help that I was reading at 5:30am! 
I use David F's method for setting thrust angle. Works perfectly and MUCH MUCH easier than using strings.
Ted, what I was suggesting is to have the alignment shop do the full alignment including thrust angle and then just change the toe equally on each side to maintain the correct thrust angle. This is the easiest way if all your interested is changing toe settings (like going back and forth between street/autox/track settings to save your tires on the street).
I use David F's method for setting thrust angle. Works perfectly and MUCH MUCH easier than using strings.
Ted, what I was suggesting is to have the alignment shop do the full alignment including thrust angle and then just change the toe equally on each side to maintain the correct thrust angle. This is the easiest way if all your interested is changing toe settings (like going back and forth between street/autox/track settings to save your tires on the street).
12-31-2006, 06:43 PM
#18
Also, David F's method works fine for checking toe (I did similar things for a long time), but I will say that the toe plates are well worth the money. Just makes the process easier and more consistent.
Not trying to sell stuff for anybody, but the plates were one of those cheap purchases that you wonder why you didn't buy a long time ago.
Dave G.
Not trying to sell stuff for anybody, but the plates were one of those cheap purchases that you wonder why you didn't buy a long time ago.
Dave G.
12-31-2006, 07:30 PM
#19
Burning Brakes
12-31-2006, 07:34 PM
#20
Burning Brakes