Toe-in (total) - is that both sides added up?

[stevesey]

Probably one for WIM (and some maths for NC).

Both track rod end gaiters are perished, so I'm aware I'll been to replace the ends soon. In advance of this I tought I'd check the tracking (using a peice of string) so I had a good reference when replacing them (also knowing a spreader bar is needed to do the tracking properly but I wanted to know the without spreader bar setting before and after I did the job and compare with after getting the tracking done a the end).

Anyway I got a 5mm toe in on each wheel over the 520mm between the high spots on the tyre - which translates to 0 degrees 33 minutes. Haynes manual says 0 degrees 33 minutes total - so is that the deviation on both wheels - so 1 degree 6 minutes in my case?

I'm not too worried, especially as the tyre wear is pretty even. Just interested to know how far out the measurements are. Anyone know how much difference the spreader bar normally makes to the measurement (exact amount will depend on the state of your bushes etc of course) and in which direction?

 

[Number_Cruncher]

I'm not clear exactly what you've measured and how, so I can't answer directly.

However, I would recommend a Gunson's Trakrite (see Ebay item 250530964760 as an example).

Using a Trakrite, you can happily forget the numbers, and simply set the car up to track without scrub.

For a job like yours, where fancy 3D alignment simply isn't needed, a Trakrite will be fine - I've always obtained very good tyre life after using them.

 

[Number_Cruncher]

Sorry, I forgot to say, without a reasonable alignment machine, you can only really work with the total, because the individual angles a referred to a virtual line, the thrust line, which you can't reference with your string.

The only thing the individual angles really give you is some hope of obtaining a straight steering wheel straight off the machine.

The way I get a straight steering wheel using a trakrite is to make the car track without scrub first, and then go for a test drive. If the steering's off centre, I just swap some adjustment side to side until the steering wheel is centred, finishing off with a final check using the trakrite.

If you find that after doing this most of the thread is showing at one side's track rod and little at the other, then, you've got a bigger problem, and you need a full alignment check.

 

[stevesey]

Will a trackrite work on a merc? Given that you are supposed to load the suspension with a spreader bar, the slow speed over the trackrite won't be enough to load the bushes will it?

Which sort of brings back to the question of how much difference a spreader bar makes.

 

[Number_Cruncher]

>>Will a trackrite work on a merc?

It works very well. As the Trakrite doesn't measure any angles or distances, it only measures scrub as the car rolls over. Minimise the scrub, and you get excellent tyre wear. Using a spreader bar AND a Trakrite together would give you worse results.

At first glance, Trakrites look way too simple to be any good, and initially, I was very much a skeptic. However, I think for the DIYer, they are a very sound approach, and will pay for themselves very quickly in saved "alignments" and in reduced tyre wear - of course, we would all like to own an all singing all dancing computer driven optical 3D alignment system!

 

[wheels-inmotion]

I'm not comfortable with this procedure at all at a professional level... DIY it's great to explore but at the paying "give me results level" this just won't do.

 

[stevesey]

I'm not comfortable with this procedure at all at a professional level... DIY it's great to explore but at the paying "give me results level" this just won't do.

Obviously - a professional should have the proper kit - although about 20 years ago I did have a garage use trakrite's on my car. Same goes for string, a spirit level and a ruler really, quite accurate if you take your time - but a DIY/pitlane exercise, not a professional garage one.

Any thoughts on my spreader bar question - how much difference does it make (depends on the bushes I guess) but are we talking degrees, or just a few minutes?

 

[Number_Cruncher]

>>I'm not comfortable with this procedure at all

c.f. Mandy Rice-Davies!

We are talking about DIY procedures, and IMO, in the DIY context, a Trakrite is a major advance in ease of use over a length of string!

Spreader bars can't apply any significant load into the steering, and really only bias any slop or free play towards toe out - thus you can always be sure you'll get some toe in when you've finished the adjustment.

Again, to do the job properly, you should use one, however, I haven't found it necessary on my W124.

After using a Trakrite, I changed some tyres on my W124 this August - they had done 13K on rear plus 23K on front.

 

[stevesey]

I'm not comfortable with this procedure at all at a professional level... DIY it's great to explore but at the paying "give me results level" this just won't do.

>>I'm not comfortable with this procedure at all

c.f. Mandy Rice-Davies!

We are talking about DIY procedures, and IMO, in the DIY context, a Trakrite is a major advance in ease of use over a length of string!

Not with you on the Profumo reference.

Spreader bars can't apply any significant load into the steering, and really only bias any slop or free play towards toe out - thus you can always be sure you'll get some toe in when you've finished the adjustment.

That's one of the things I'm interested in - has anyone measured a car with and without a spreader to see what difference it actually makes?

 

[Number_Cruncher]

I was thinking of her famous retort "Well, he would, wouldn't he?" in that we can hardly expect someone in the suspension alignment business to countenance the use of anything less than their expensive equipment.

 

[stevesey]

I was thinking of her famous retort "Well, he would, wouldn't he?" in that we can hardly expect someone in the suspension alignment business to countenance the use of anything less than their expensive equipment.

Ah got you - but then his nice expensive equipment will do so much more. And much more easily than a peice of string and a calculator - athough to be fair it only takes me 5 minutes to check the tracking with string. Doing the set back takes a bit more setup work though.

Actually - that does get me thinking - how would a member of the public react if he took his car in for a tracking check (not a full alignment) and the guys got out a bit of fishing line (more accurate than string) and started measuring stuff. I'm sure next time he'd be off to the place down the road with the lasers.

 

[Number_Cruncher]

>> I'm sure next time he'd be off to the place down the road with the lasers.

He he!

The use of lasers on these alignment rigs really is sales BS!, there's nothing on any car's suspension that needs the accuracy of a laser to set up - BUT!, customers love it, and think it MUST be better.

As the car has been about for a century or so, you can be sure that just about everything to do with it has been given a good look over by marketing people!

 

[wheels-inmotion]

>> I'm sure next time he'd be off to the place down the road with the lasers.

He he!

The use of lasers on these alignment rigs really is sales BS!, there's nothing on any car's suspension that needs the accuracy of a laser to set up - BUT!, customers love it, and think it MUST be better.

As the car has been about for a century or so, you can be sure that just about everything to do with it has been given a good look over by marketing people!

Shame on you..... How can you say that the modern car chassis doesn't need the accuracy of a Geometry calibration? A century ago the front toe positions was dead ahead give or take a foot, now it's dead ahead give or take a 60th of a degree.... cars have come a long way.

I have every respect for those able to set the front toe using string because there is some serious math involved but i ask this...... Front wheel alignment, what are you aligning the wheels to?

 

[Number_Cruncher]

Shame on you..... How can you say that the modern car chassis doesn't need the accuracy of a Geometry calibration?

I didn't say that. My point is that nothing as accurate as a laser is strictly necessary to obtain the accuracy required, BUT, the use of lasers doesn't half impress the punters. It's a nice bit of pseudo-science used for marketing ends.

Front wheel alignment, what are you aligning the wheels to?

Yes, we dealt with that question in post #3 of this thread.

 

[Rory]

I didn't say that. My point is that nothing as accurate as a laser is strictly necessary to obtain the accuracy required, BUT, the use of lasers doesn't half impress the punters. It's a nice bit of pseudo-science used for marketing ends.

Surely it's not accuracy that lasers bring that is useful, it's ease of use? Attach the gubbins to each wheel, press some buttons on the computer and Hey Presto you''ve got all the alignment readings.
The skill is in interpreting and adjusting everything so the owner is happy.

 

[stevesey]

Shame on you..... How can you say that the modern car chassis doesn't need the accuracy of a Geometry calibration? A century ago the front toe positions was dead ahead give or take a foot, now it's dead ahead give or take a 60th of a degree.... cars have come a long way.

I have every respect for those able to set the front toe using string because there is some serious math involved but i ask this......

Serious maths? A bit of basic trig - which I now have a speadsheet set up for - just feed the the difference (in mm between the front and rear of the rim and out pops the angle).

Accurancy - agreed any "proper" device will give you more accurancy, but on a 16in wheel a measurement difference of 1mm equates to an angle of 8 minutes. Which is within the tolerances in most on the Haynes manuals I have (and with a bit of fishing line I'd probably be happy to take reading down to 0.5mm accuracy).

Surely it's not accuracy that lasers bring that is useful, it's ease of use? Attach the gubbins to each wheel, press some buttons on the computer and Hey Presto you''ve got all the alignment readings.
The skill is in interpreting and adjusting everything so the owner is happy.

Yep ease of use is what anyone doing it for a business is after, so they can turn more cars around. Of course the old **** in, **** out motto still applies when it comes to using the stuff. Equally, listening to the customer, interpreting the result and making the changes are what lifts those with good reputations (like WIM) above the rest. I suppose one could agrue that even just using a bit string those with the skill would still come to the top.

 

[wheels-inmotion]

I didn't say that. My point is that nothing as accurate as a laser is strictly necessary to obtain the accuracy required, BUT, the use of lasers doesn't half impress the punters. It's a nice bit of pseudo-science used for marketing ends.



Yes, we dealt with that question in post #3 of this thread.

So we did, sorry..... Question though, as much as i admire those able to math the math with string what sort of tolerance's do you work to? Is there any accounting for wheel run-out? How do you math the KPI/ SAI/ Included angle?

 

[Number_Cruncher]

I don't think anyone is suggesting measuring the other angles with string - however, it's certainly true that there are mechanical gauges which can be used to obtain these values - the complex expensive kit isn't absolutely necessary to obtain the data, however, it necessary if you want to get them in reasonable time in a commercial setting with a nice easy procedure to follow.

For DIY use, the spirit level castor camber KPI gauges are perfectly adequate.

 

[stevesey]

So we did, sorry..... Question though, as much as i admire those able to math the math with string what sort of tolerance's do you work to? Is there any accounting for wheel run-out? How do you math the KPI/ SAI/ Included angle?

Think I answered that one above regards toe - 8 minutes if I measure to 1mm accuracy on a 16in rim - and I probably could do better than that (also of course the wider the rim the greater the accuracy). So 5 minutes (5/60ths of a degree) is probably the level to be aiming for.

The full string process involves setting up a string reference box around the car, so you can measure front/rear setback and toe (I've only ever done front -> rear strings to check toe). Camber is done using a spirit level. Then run out checked by moving the car forward by 1/2 a wheel turn and repeating the measurements (although I think 1/4 turns would be more reliable). I imagine the calculations that follow are not dissimlar from what goes on within the laser systems.

 

[lynall]

Steve if its only the gaiters that are split and the joint has no play and is mechanically safe you can buy new gaiters cheap.



Lynall