Tracking - string method

[Grumpy21]

Just been watching a video of a chap setting the toe-in of his Morris with a stretched piece of string. I’ve read about this on here a few times too. One thing has always concerned about this method. If the datum is set by measuring the distance from the string to the rear wheel and error of 0.5mm is induced this will extrapolate to 2-3mm at the front. Or am I missing something?

Oh, just a curiosity as I have a tracking gauge (gunsens trackrite)

[les]

Perhaps I should watch the video, because as I see it, the string length is determined by how hard you pull it !

[Grumpy21]

Sort of hard to explain but the chap in the vid sets the string parallel to the rear wheel rim by measuring. Even an error of 0.5mm would be 2.3mm when projected to the front wheel so how car an accurate measurement be obtained?

[Bill_qaz]

Why would you have an error? If you can't accurately measure parallel to rear you'll struggle to accurately measure the front. If you set tracking on fronts only then you are setting toe in or toe out but not relative to the drive axle. The only truly accurate system is the lazer type which measure all axles relative to the chassis but even this is down to the operators standard. The lazer alignment equipment is the go to on multi axle vehicles where it can have a major impact on tyre wear and fuel economy.

[geoberni]

Perhaps I should watch the video, because as I see it, the string length is determined by how hard you pull it !

I'm with you on that ...

I've a Trakrite, which seems to work fine for my Minor.

[Bill_qaz]

https://youtu.be/n3DBI6nY-XU

But my toe in is perfect

[Grumpy21]

Why would you have an error? If you can't accurately measure parallel to rear you'll struggle to accurately measure the front. If you set tracking on fronts only then you are setting toe in or toe out but not relative to the drive axle. The only truly accurate system is the lazer type which measure all axles relative to the chassis but even this is down to the operators standard. The lazer alignment equipment is the go to on multi axle vehicles where it can have a major impact on tyre wear and fuel economy.

Thanks I may be explaining my point poorly. Lots of folk mansion a string method of seeking toe in. I watched a video on YouTube of two chaps using this method. A piece of string is pulled tightly between two objects (axle stands on one vid) and set parallel to the rear rim by measuring (quite poorly in the vid) the distance from the rim to the string.

https://youtu.be/TVGIq4769PY

Now purely for interest I can’t get my head round how, if there’s an error at the rear, the string can be accurate at the front. Even 0.5mm inaccuracy at the rear will be an inaccurate of 2-3mm minimum at the front.

I use a trackrite so it’s purely an academic question, although I may have a look later as I’m sure I’m missing something in my understanding

[StillGotMy1stCar]

No wonder you can’t get your head around it, the guy in the linked Youtube clip is doing it wrong.
He has the basics, but you need two pieces of thin string or fishing line mounted beyond the car bumpers pulled very tight, they need to be parallel to each other and the car.
When setting it up it helps if you are a bit OCD about it, I perhaps take it to another level by checking the wheel rims are running true at the measuring point.
I’ve had very good results using this method on modern cars where the rear tracking also needs setting.

Regards John

[Grumpy21]

No wonder you can’t get your head around it, the guy in the linked Youtube clip is doing it wrong.
He has the basics, but you need two pieces of thin string or fishing line mounted beyond the car bumpers pulled very tight, they need to be parallel to each other and the car.
When setting it up it helps if you are a bit OCD about it, I perhaps take it to another level by checking the wheel rims are running true at the measuring point.
I’ve had very good results using this method on modern cars where the rear tracking also needs setting.

Regards John

Now that was my thinking. Thanks for confirming I’m not mad

[Sleeper]

You can't beat Youtube for a good laugh, the latest I saw was someone explaining about dangerous gasses, he said Carbon Dioxide was explosive , just couldn't wait to drop him a message to check out CO2 fire extinguishers ...

Maybe he got in touch with the manufacturers to explain where they were going wrong...

John ;-)