Measuring Toe in

[andyhodg]

This feels like a really stupid question but when measuring toe in where do you measure, is it at the rim diameter or the tyre diameter. Also if you want to achieve say 1/8" toe in is that the difference between the measurements across the two wheels at the front and rear of the tyre or half the difference?

Also what would you guys recommend I set the toe in to? I am running a +2 with standard springs and rubber (not poly) bushes.


Many thanks Andy

[tvacc]

On the LOONY site. www.lotusowners.com


In the repairs/upgrades section I have someting called the "old man method" for adjusting your toe in.


Works great..

Tony Vaccaro
www.lotusowners.com

[bcmc33]

Andy,

I've just done my car this week having reconditioned and modified the rack for wider wheels. You?re correct in saying that the toe in is half the difference between the front and rear wheel rim edge.

However there appears to be lots of ways to take the measurements ? I used the Jackie Stewart/Rohan method of two strings, one each side of the car on the wheel centre line. With the strings parallel take measurements to the rims and the necessary calculation is simple.

For future use I have now made two lengths of dowel to make the strings parallel very quickly.

[twincamman]

yes I agree ----stringing a car is good for a formula car or a road car ----BUT remember to use only one half of the measurement per side --IE 1/8th = 1/4 per side --you can get dead on with string ----I use dental floss -----ed

[ppnelan]

I thought toe-in = (distance between rear edges of rims) minus (distance between front edges of rims) rather than half of this See http://autorepair.about.com/library/glo ... ef-381.htm

And I if you wanted 1/8" toe-in, wouldn't you set each side with 1/16" difference between front & rear rim edges from the string lines, not 1/4"

Matthew

[twincamman]

yes --better put -ed A TRAMEL BAR IS VERY GOOD ALSO ---SAME APPLIES ---ed

[lotuselan2]

There are several other simple tools I prefer to string for the front toe in. The normal racing supply places (Pegasus in US) sell both the low and high cost set-ups. Two toe plates and identical tape measures are my current favorite.

I have long used the string method to determine if the rear toe in is identical for each side and this method is very accurate because of the amplification of the distance to the front wheel hubs which is where I check them. Method is to have your helper hold the string touching the rear center of the rear tire. At the front of the car have a tape measure held to the center of the front hub. Slowly move the string towards the center of the car until the string touches the front edge of the rear tire. Due this identical procedure on each side and you will know if your rear toe in is equal (at least with respect to the front wheels which I guess is all that matters).

[bcmc33]

I know my formal automotive education finished some 50 years ago, but the basic principles always stay the same.

I have always believed that toe-in (or toe-out for that matter) is the a measure of the wheel pivot point to the front edge of the wheel rim. The only practical way to do this measurement is to measure the difference between the front and rear rim dimensions and halve it.

Modern cars have the tracking measured by the angle of the wheel to the centre position. So when I take my car to the tyre centre in the spring to verify the toe-in, what angle should I specify for their high tech laser set-up?

[paddy]

To convert toe-in (degrees) to toe-in (measured centre to rim)

toe-in (mm) = d * t * pi / 360

(or approximately d * t / 115)

where:
d is wheel diameter in mm
t is toe-in in degrees

So for a wheel of 365mm diameter, a toe-in of 1 degree corresponds to a toe-in of 3.2mm (measured centre to rim) or 6.4mm (measured rim to rim).

Converting the other way:

toe-in (degrees) = t * 115 / d

where:
d is wheel diameter in mm
t is toe-in in (centre to rim) in mm

Paddy

[alan71]

My understanding of toe-in measurement is that in the diagram it equals b-a, no need to half the result.

Alan.

[twincamman]

i DO A HALF OF A HALF ---AND A HALF OF A HALF ---ROLLING THE CAR BACK AND FORTH SETTING UP AGAIN ETC ----TILL ITS PERFECT ------OLD AND RETIRED WITH LIITTLE ELSE TO DO I GUESS

[stuartgb100]

"OLD AND RETIRED WITH LIITTLE ELSE TO DO I GUESS"

C'mon Ed. You can do better than that.

Don't give up yet, or Morris Dancers & Shapecrafts will finally get your goat ........... !

Regards,
Stuart.

[twincamman]

- they wont get me as long as I wear my tinfoil hat -----ed

[paddy]

I've just realised that my formula was misleading (OK, wrong ).

I've found 3 different definitions of toe but for the sake of clarity I'll use this one, which was also the most common:

My understanding of toe-in measurement is that in the diagram it equals b-a, no need to half the result.

Lets say:

td = toe-in distance = difference in track measured at front and rear of rims (measured in mm) = (b-a) in Alan's figure.

ta = toe-in angle (measured in degrees)

d = rim diameter (measured in mm)

To convert from degrees to mm:

td = ta * d * pi / 90

or approximately:

td = ta * d / 29

To convert from mm to degrees:

ta = td * 29 / d

So for a wheel of 365mm diameter, a td of 1/8" corresponds to a ta of about .25 degrees (or 15 seconds).

If your favourite definition of toe is different, adjust the formula by a factor of 2 or 4 as appropriate.

One obvious advantage of quoting toe as an angle is that it is unambiguously defined, and also doesn't vary according to the size of wheel.

Sorry for any confusion caused

Paddy

[twincamman]

OR you can measure the front and back of each front wheel from the string and turn in 1/2 the distance per side on each side until you have the toe in you want and go 200 miles an hour and make equations later -------[ HURRY the mother ship is hovering] ---ed