Wheel alignment - string method

[Cup_Phil]

I want to play around with some different toe/camber settings this year - and really don't want to pay £60 each time to have the local garage monkeys do it

After watching a load of BTCC teams use the string method I've decided to have a go

I understand the concept - fishing line between 2 equal height axel stands, parallel to hubs - then measure front and back of the wheel
And I understand that to have no toe at all the measurements should be the same

But say I want 10minutes of toe out (which is what I ran last year) - how the hell do I work out what measurements from wheel to string that equates too

Do I have to measure the diameter/radius of the wheel and do some trigonometry?

 

[Cup_Phil]

Hrmmm bit of maths searching and found this

Wheel diameter in mm x sin(toe degrees)

10minutes of toe is 0.16degrees
15inch wheel is 375mm

so 375 x sin(0.16) = 1.04mm

So the back part of each wheel should be 1mm roughly further into the car than the front part of the wheel..

Sounds straight forward :|

 

[Dan@SJM]

I'm running 1mm toe out each side on mine.

 

[Cup_Phil]

Cool that's what I'll aim for

Do you have to compensate for the rear track being narrower than the front when you set the string up?
I read that the 172 has a 1406mm front and 1386mm rear track width - so do I measure the string 10mm further out each side at the back so it's perfectly perpendicular with the car center line?

 

[Cup_Phil]

Ignore me - just realised it'll be easier to put 2 long rods front and back - on 4 axel stands. Then tie the fishing line to those so they are equally spaced front to back

Then measure distances to center of wheels to get them aligned

Fun for saturday morning lol

 

[Steven103]

Two tips:

1) Cut a single notch in either end of your "long rod." The distance between the notches needs to be sufficient so that the widest point of the car (at the height of your stub axle) doesn't interfere with the string, but ideally leaves 20mm or so between the wheel and string. The exact distance between them isn't crucial, but both rods need to have an identical notch-spacing.

2) Rather than tying string to a rod, attach a weight to either end of the string (can be anything, a half full drinks bottle would do lol), and hang the string over the grooves so that they self tension AND self-parallel. Then all you need to worry about when setting up your string is that the string is parallel to the centre line of the car.


*I keep saying string, use fishing line or sewing cotton etc.

Also make sure to have a jump around on the sills to settle the car, have something to hold the steering central (bungy cord can be good) and ideally get the steering straight (ish) beforehand to avoid including any slip angle, backlash, deflection in rubber bushes etc.


P.S. Needless to say, I hope your wheels are 100% straight haha...

 

[Cup_Phil]

haha cheers mate

Just looked on B&Q website and they do 15/20mm dowel in 2.4m lengths - so gonna grab 2 of those and then like you say I can make notches at exactly the same distances on both. Get some old fishing line with some heavy metal washers tied on the end and I should be able to do as you've said fairly easily

My alloys are absolutely 100% straight. Bought them brand new and they've never had any knocks or impacts etc... but I'll jack the car up at the weekend and put a micrometer on the wheel and rotate it to make sure they are 100%

 

[Dan@SJM]

Another tip is mark the wheel where your measuring, keeps it easy then.

 

[Cup_Phil]

Ahh yeah - bit of masking tape on the rim and put a dot where I'm measuring from - makes sense

Thanks

 

[Chri5]

http://www.negative-camber.org/jam149/technical/alignment.html

Have a look at that page bud, I used this method last year when I was experimenting. It also includes the maths thats needed to work out angles relative to wheel size etc

 

[NorthloopCup]

This is why i enjoy having my own Dunlop gauges and turn plates!

 

[Cup_Phil]

I did look for a set on ebay but feck me they're expensive even 2nd hand

 

[NorthloopCup]

I did look for a set on ebay but feck me they're expensive even 2nd hand

I struck lucky with mine and get the whole lot for £80!!! My corner weight scales were, erm, free! It's always nice to be in the right place at the right time! Lol

 

[Tony Hunter]

Easiest way, is to get it done properly once, then take all your figures from that. Then you will always have a reference point.

4x axle stands, 2x rods grooved, 2x builders plum bob lines and a steel rule.

 

[The Fatty]

instead of the string, couldn't you just use a laser pointer? (i.e. a green laser would be ideal where you can see the beam?)

 

[marshall878]

Cant measure from a laser to the wheel face...

 

[James28]

Could you take pictures of it when you do it Phil? I am a little confused ha.

 

[marshall878]

 

[The Fatty]

Could you take pictures of it when you do it Phil? I am a little confused ha.

minus the music in the background, this video is a good watch to learn how to do it. Its pretty easy stuff, calculating how much toe to have is what I find difficult (when the cars been lowered etc.).

 

[DTM]

I got one of these - http://www.ebay.co.uk/itm/Trackace-...UK_Measuring_Tools_Levels&hash=item4609ee7803

incase you want something to help you out, not the best admittedly but seems to do the job to a basic degree, the test for me is that when I come to check the tracking with it time after time I get the same readings, and after having it setup on some proper gauges I also get the readings I'd expect from them.

 

[imprezaworks]

I had my old Clio tracked this way, great too watch as I'd never seen it before

 

[James28]

So Phil is talking about doing it like this? Groove's in the wood equal distance apart, string running parallel to car from groove to groove.
Measure from string to centre of wheel to get string parallel.
Measure from rear of wheel to string, and front of wheel to string. Adjust accordingly.

 

[Cup_Phil]

Yup exactly that mate - obviously rear wheels can't be altered easily you have to fit toe shims etc... but front you can then just turn the track rods in or out till the back of the wheel is 1mm further in than the front of the wheel - for 10minutes of toe out

I think standard sport 172/182's run 0 degrees as a factory recommended setting - so that'd be even easier you just adjust until the distance from the string is identical front and back

 

[MG cup]

I got one of these - http://www.ebay.co.uk/itm/Trackace-...UK_Measuring_Tools_Levels&hash=item4609ee7803

incase you want something to help you out, not the best admittedly but seems to do the job to a basic degree, the test for me is that when I come to check the tracking with it time after time I get the same readings, and after having it setup on some proper gauges I also get the readings I'd expect from them.

Would this work with really low cars? How tall is the degree scale in mm's? Having a lowered car is what usually trips up these home kits.

 

[DTM]

The mirror and laser / gauge are pretty low to the floor, mines just on some prolines, but it fits comfortably under the edge of the tyre / front bumper and would imagine you'd have to be a good 4 - 5 cm lower to start effecting them. Don't get me wrong they're not up to the quality of proper gauges but I get consistent results from them. If you do want to consider them I can have a better look on the clearance and take some pictures.
​

 

[Chip-mk1]

So Phil is talking about doing it like this? Groove's in the wood equal distance apart, string running parallel to car from groove to groove.
Measure from string to centre of wheel to get string parallel.
Measure from rear of wheel to string, and front of wheel to string. Adjust accordingly.

Just found this while searching for something else.

This is exactly how I do it and it does give you quite a high degree of accuracy so long as you take your time.
I reckon it takes me best part of an hour all in, but then so does driving somewhere to have it track and waiting while they do it and driving back, where as this is free and I dont have to trust some monkey to put gauges on properly (can have best equipment in the world and still misuse it!)

 

[imprezaworks]

Ive had a car set up using that before, i was impressed as i've never seen it done before.

 

[GrahamS]

I've strung every car I've every owned. Could do a guide on it if people want. Gives fantastically accurate results and allows for home toe in/out adjustments.

This is generally how I measure it up. Make sure measurement from the hub is even before starting. Measure from front and back of lip. Set it up so your front has the same directional amount as the non adjustable rear. Get someone to hold the wheel dead straight.

For toe you use simple trig with the wheel size.

 

[Chip-mk1]

Yeah the trig is completely trivial, but TBH I just think in MM instead in the first place these days.

But for example

2mm on a 15" rim is just:

sin of angle = 2/300 (close enough)

so angle = sin-1 (2/300) = .38

ie 2mm toe is a third of a degree

 

[GrahamS]

it is you're right Chip. I set up straight and go from there.

Forgot what I was doing once and put 3 degrees of toe in on my golf. Wasn't bad round the track but went through a set of front tyres in 800 miles. I only realised what I'd done when I had got to my campsite in Switzerland so had to ruin the rears on the way back!

 

[Chip-mk1]

3 degrees? WTF you can get it better than that just by looking at it, lol.

 

[GrahamS]

Honestly have no idea what I was thinking.

 

[Chip-mk1]

Honestly have no idea what I was thinking.

Lol.

My Mrs car has 6mm (1 degree ish) of toe in one the rear at the moment, just ordered some shims to try and correct it.

 

[James28]

Yeah the trig is completely trivial, but TBH I just think in MM instead in the first place these days.

But for example

2mm on a 15" rim is just:

sin of angle = 2/300 (close enough)

so angle = sin-1 (2/300) = .38

ie 2mm toe is a third of a degree

So what is standard toe on clio's in mm?

 

[bozothenutter]

Lol.

My Mrs car has 6mm (1 degree ish) of toe in one the rear at the moment, just ordered some shims to try and correct it.

when using shims to correct, would u use a straight shim on the other side to equalize the track?
always wondered about this.

 

[MG cup]

So were saying 2mm is only 20 minutes? Sounds a lot but then I don't know.

I am away to source some ally rod today to make rigs for hanging of the front and back.

grazo22 have you done all your cars on the ground or have you rolled all four wheels onto small ramps. I'm thinking from being able to turn the track rod for setting on a lowered car.

 

[GrahamS]

MG cup


I do mine in the garage and have been known to do it just on the road.

If in the garage I put wood under each wheel until the car is as level as possible. My garage floor isn't flat. That gives me enough room to lay on my back and turn the rod.

2mm is more than 20 minutes depending on your wheel size.

Use this

You put in the degrees you want over both wheels so 1 degree put into the equation gives you half a degree per wheel

Example: with a wheel size of 16" (406.4mm)

Over both wheels 1 degree toe in/out

you get out

This means you adjust the track rod end until you see this adjustment away from straight line like this

Hope that makes sense

 

[imprezaworks]

would you say this method is better or just different than using computer systems etc, just curious.

 

[Chip-mk1]

So were saying 2mm is only 20 minutes? Sounds a lot but then I don't know.

I am away to source some ally rod today to make rigs for hanging of the front and back.

@grazo22 have you done all your cars on the ground or have you rolled all four wheels onto small ramps. I'm thinking from being able to turn the track rod for setting on a lowered car.

2mm difference from front of wheel to back of wheel is just over 20 minutes if the readings are taken 300mm apart yes.
Apolpgies though that 300mm was referring to my minis 12" wheels not the 15" on the Clio. It actually would be 2.5mm for the same on a Clio as it's more like 380mm.
sorry for that error, like I said I just work straight in mm these days anyway.

That 2mm difference is only 1mm of toe though as the front will be in 1mm and the back out 1mm when measured from the centre.

i will put up a more detailed answer when back in the office.

 

[GrahamS]

I'm not a mechanic and never have been but the hunter I watched someone use once was a great piece of kit. The cheapy ones some garages use have never had such good results. I wouldn't touch anything that wasn't full 4 wheel alignment as I've seen a fair few clios with just slightly off rear axles which needs to be taken into account with front adjustment

As Chip says it's good to get a basic set up and play from there but this can be used to easily and cheaply try different set ups.

Having done over 80k in cars with this done I have never had adverse tyre wear (apart from when I slipped up) so if you take you're time and check everything twice it's pretty dead accurate.

The above should explain what you mean Chip-mk1