les wrote: ↑Thu Mar 16, 2023 9:11 pm
Out of interest If the toe in was set with the wheels on full lock, or, for that matter, any position other than straight ahead, and then the wheels turned to the straight ahead position. Would the toe in still be correct? My suspicions would say no.
The ackerman principal . If you visualise turning on a lock the inner wheel is traveling on a smaller circumference circle than the outer wheel.
So the tracking can and must only be set in the straight ahead position, hence moving back and forth after every adjustment.
Screenshot_20230317-134514_Chrome.jpg (55.81 KiB) Viewed 1682 times
Myrtles Man wrote: ↑Thu Mar 16, 2023 4:46 pm
Sorry Culp, but I don't think much to your choice of string - something like fishing line is what you need. Also, as Simmitc points out, you do your check on the edge of the wheel rims, not the tyres.
I could replace the string with fishing line but I dont think its going to fix the problem. I cant check on the wheel rims because the tyre bulges out and without a tracking gauge string and axle stands is all I have
Yes, but toeing in or toeing out? From your previous posts, they are toeing out, and should be in.
the track rod ends are wound in as tight as they will go.
And that's your problem. With the TRE screwed on to the rod as far as possible, the rear of the wheels will be pulled in. As written previously, you need to unscrew each side equally. a bit at a time, so that the TREs are further apart, thus pushing the rear of the wheels out and the front in. The telescopic pole suggested above is a very good method of measuring and better than string.
Good luck, you will get there.
Sorry a typo on my behalf. They are toeing in the measurment you are looking at is the front of the front tyre
simmitc wrote: ↑Thu Mar 16, 2023 9:45 pm
Myrtles Man raises an interesting point. I suspect that with modern laser tracking then it might be possible to measure all wheels against each other and against a central datum point. However, traditional optical tracking gauges with mirror and a periscope down which one looks to take the reading:
TG1.png
were only ever applied to the front wheels, with no connection to the rear. Similarly, the Gunson Trackrite drive-over device:
TG2.png
requires that you drive over it only with the front wheels. I have not seen any manual that suggest that the front needs to be checked against the back when tracking. If course, such a manual may exist, but I have not seen it.
It would be necessary to check that the wheels were all pointing in the same direction to check chassis alignment, for example after accident damage or spring hanger repairs, but that's a different subject from front wheel alignment or tracking toe-in.
All gauges that I have used require that the vehicle is on level ground with the wheels pointing straight ahead (or as much as they can), and that the vehicle is moved back and forth after adjustment before rechecking.
I agree with Les that the angles involved in steering will affect the tracking reading, hence the need to a straight ahead setting before checking.
I cant afford a tracking gauge those things are £600 I do have one of the Gunsons track right devices and it comes out ok, pointer in the middle all of this has been checked with the car in a straight line
If you want to use string stretch it full length of car move front point until measurement at rear wheel string to rim is the same front and rear of the wheel, it doesn't have to touch the rim, you now have parallel to rear wheel. Without moving string measure string to wheel rim on front, rear of rim and front of rim, the difference in these two is your toe.
Thank for the explanation Bill, makes sense, however I’m trying to overcome thinking that the steering rack would hold the two wheels parallel despite being on two different radii.
les wrote: ↑Fri Mar 17, 2023 7:53 pm
Thank for the explanation Bill, makes sense, however I’m trying to overcome thinking that the steering rack would hold the two wheels parallel despite being on two different radii.
Because of the off set of the steering arms relative to the pivot point if that makes sense.The ball joint of the steering rack is inboard of the hub pivot point, so giving a positive ackerman system.
The diagram is only demonstrating the angle theory so doesn't show a steering rack staying fixed.(not my diagram just generic)
Remember the measurement is to be nil to 3/32. The point of having some toe in is due to any looseness in the linkage that might cause the wheels to wander from straight to toe in to toe out. The looser the geometry is the larger the toe in needs to be to ensure the wheels can not swing out to a toe out condition. What point on the rim does everyone measure to? The outer edge is not perfect all the way around and the section before that is sloped. For final check it's best to measure a point on the outer edge and then move the car forward to measure the same spot on the rim 180° apart.
The reason that the wheels toe in on a rear wheel drive car is that the wheels are forced outwards by the forward movement/pressure acting on the wheels so the toe in is there to compensate for that outward movement/pressure.
On a front wheel drive car the opposite movement/pressure take place so forcing the wheels inwards so the initial tracking is set to toe outwards.
jaekl wrote: ↑Sat Mar 18, 2023 11:35 am
Remember the measurement is to be nil to 3/32. The point of having some toe in is due to any looseness in the linkage that might cause the wheels to wander from straight to toe in to toe out. The looser the geometry is the larger the toe in needs to be to ensure the wheels can not swing out to a toe out condition.
It's not for looseness or wear as it's set from new.
On the front of the car, toe in increases straight line stability. This is because if one of the wheels is disturbed during straight line driving and is pulled rearward of the steering axis then the wheel will steer outwards.
This minimal outward steering would only straighten the wheel and develop zero toe so would help the car stay straight.
Okay, I was looking for the term stability. That's helps the road feel. Thanks more making me look it up and I had mixed the "nil to" from camber to toe in. Haynes states it as 0 to 1/8 with 3/32 being optimum This shows how tight the Minor geometry. I'm not finding where exactly on the wheel it should be measured. An angle spec could be converted to wherever one wants to measure.
I couldn't find any site that states a negative toe in for FWD. It's just the act of moving that pushes them out and the toe in helps to hold them stable.
Checking the manual for ADO16 the "toe out" is 1/8, so thank you for showing me the light on FWD. We are still left to as where to apply this 3/32 difference.
"First, let's define what we mean by toe. It is the difference in the distance between the front and rear edges of the rims on one axle"
Above quote from something called Northstar Racing. However, another source on the mighty interweb states that the measurement must be taken from halfway up the tyre so yer pays yer money and yer takes yer choice. Whichever you do opt for the important thing thereafter is to keep a close eye on front tyre wear; evidence of wear on outer edges says you've overdone the toe-in, wear on inside edges says you aint got enough or, even, toe-out so, either way, a bit more tweaking will be required.
jaekl wrote: ↑Sun Mar 19, 2023 1:02 pm
Okay, I was looking for the term stability. That's helps the road feel. Thanks more making me look it up and I had mixed the "nil to" from camber to toe in. Haynes states it as 0 to 1/8 with 3/32 being optimum This shows how tight the Minor geometry. I'm not finding where exactly on the wheel it should be measured. An angle spec could be converted to wherever one wants to measure.
I couldn't find any site that states a negative toe in for FWD. It's just the act of moving that pushes them out and the toe in helps to hold them stable.
As someone earlier posted fwd cars normally are set to toe out, is that what you mean by negative?. Positive and negative terms normally relate to camber.
In front wheel drive the torque reaction of applying drive tries to pull the wheels towards toe in, so from static toe out in becomes more toward zero.
The alignment must be measured on the wheel rim not the tyre. The wheel rim should stay in the same orientation when the wheel is rotated 180 degrees providing the wheel is not damaged, the tyre does not remain the same.
The measurement must be firstly taken on the rim halfway up at the rear of the wheel. Note the measurement. Mark the rim. Roll the vehicle forward so that the mark on the rim is rotated 180 degrees, re-measure at the front of the wheel.
The difference between the two is either toe in, toe out or somewhere between. Adjust as necessary.
Using a Dunlop tracking gauge make setting the toe in/toe out so much easier. https://www.ebay.co.uk/itm/165976407684 ... R_S0qbvfYQ
I have used the string method very successfully in the past.
I have also used a earlier version of the Gunson tracking gauge which gave good results. https://www.ebay.co.uk/itm/180708096231 ... R8SWl7vfYQ
Thanks all for the feedback. I'm no further on really I can see that I should measure the toe In more accurately and I'm bidding on a dunlop tracking gauge but it still doesnt explain why I have too much toe in with track rod end screwed all the way onto the steering rack.
I do have one of the Gunsons track right devices and it comes out ok, pointer in the middle all of this has been checked with the car in a straight line