Best place for alignment work.

[Mr Whippy]

I want to get my tracking done, but want someone who actually knows about steering/geometry to be doing it, not someone who just points the steering wheel straight and adjusts the TRE's until the computer says "yes"

My concern is, if the steering rack is say 4% over on it's travel, then a given degree of ackerman is already active (ie, one wheel turned more than the other) and so adjusting the TRE's at that point is meaning you have non-symmetric steering!?

I'm not sure why my steering wheel is slightly to the left (5 deg or so) on a flat smooth road, and I'm not sure the tracking is 100% either.

Main dealer, tyre place, specialist tyre place, independant specialist?

Any help or recommendations much appreciated!

Dave

[leorest]

Unless you get a cast iron good personal recommendation you would probably be better off doing it yourself.
Flat bit of ground, fishing line, axle stands, el cheapo laser spirit level, steel rule, tape measure, plumb line, metal plates, grease, and some schoolboy mathematics. With all this and a bit of research on the web you should be able to do full four wheel alignment with high accuracy, just not as quickly as with the professional kit.

[wildoliver]

Go on post up how to do it you sound like a bit of an expert

[Mr Whippy]

leorest said:

Unless you get a cast iron good personal recommendation you would probably be better off doing it yourself.
Flat bit of ground, fishing line, axle stands, el cheapo laser spirit level, steel rule, tape measure, plumb line, metal plates, grease, and some schoolboy mathematics. With all this and a bit of research on the web you should be able to do full four wheel alignment with high accuracy, just not as quickly as with the professional kit.

As always I probably could do it DIY with some time and patience, however a this time of year spending TLC time with the car doing such jobs is not really an option.

I was just after a good trusted place I could slip £££ to do it right and leave me knowing they have done a job to a level I would be happy with!

Considering most places I go today with so called professionals who do work to a lower level of quality that I do myself is why I'm asking for a good decent place really.


Might have a stab myself. Anyone know how to check the steering rack itself is centred 100% before locking it in place and straightening the steering wheel itself and adjusting the TRE's?

Dave

[leorest]

wildoliver said:

Go on post up how to do it you sound like a bit of an expert

I'm not keen on the term "expert" as most self proclaimed "experts" are disappointing in their abilities and lacking in morals to say the least. I would describe myself as an interested fiddler (no smirking at the back please). I have spent a lot of time researching this subject on the net but would like to get some proper reference books to move on to the next stage. I'm not going to start teaching before I've learnt it properly myself!
Though here's a useful link for you.

To get a bit more on topic... I don't blame Mr Whippy for trying to find someone to do it for you. If you've got the money and not the time then it's the sensible way to go. It's such a shame it's so difficult finding a tradesman who's honest and good at his job!

[leorest]

Mr Whippy said:

... Anyone know how to check the steering rack itself is centred 100% before locking it in place and straightening the steering wheel itself and adjusting the TRE's?

I believe some racks have marks to show where they are centred and some even have holes you can stick a bolt or pin into to lock them at actual designed centre.

[Mr Whippy]

leorest said:

Mr Whippy said:

... Anyone know how to check the steering rack itself is centred 100% before locking it in place and straightening the steering wheel itself and adjusting the TRE's?

I believe some racks have marks to show where they are centred and some even have holes you can stick a bolt or pin into to lock them at actual designed centre.

Thanks for the link above. Not sure how his little jig works to be honest, unless thats built to exact standards to start with

I've seen a few camber gauges around relatively cheap but not sure on using those.

As far as I know camber is not adjustable to any degree on my current car, and the rear geometry is static to the trailing arms so the only real adjustment is toe.

My main concern ultimately though is making sure I have symettric steering so the ackerman and so bump steer, turn camber and so on are all consistent in bends left or right... I've got this feeling it's out but I can't be sure, but the new TRE on the nearside along with a wheel not 100% straight is telling me it's not 100%

I'll continue to ask around and see what methods are employed at a few places I know, just don't want to pay some monkeys to set up my car with guessed toe settings off-rack centre

Dave

[wildoliver]

off topic that link has just shown the underside of an Mx-5 i knew they were a copy of an Elan but the rear suspension looks identical!!!!! Copycats!

[stevieturbo]

Depends how far you want to travel...

The Powerstation in Tewkesbury can sort any alignment matters.

[leorest]

I have a camber gauge which uses a digital spirit level which is accurate to 0.1 of a degree. It looks very nice and professional but similar (if not better) accuracy can be had out of a plumb line, straight edge and steel rule (credits to Mr GreenV8S). You hold the straight edge against the wheel and the plumb line against the straight edge, then use the rule to measure the difference top and or bottom. Some trig will tell you that if the top is 10mm further away from the straight edge then the bottom (where vertical distance between top and bottom is 570mm) then that wheel is cambered in (-ve) by 1 degree. If you have a steady hand and a good eye you can easily and quickly measure to 1mm which equated to 0.1 degrees. More than good enough.

The link about M(X5)iata alignment shows most of the principals but don't get caught up in the complexity of the machined tools. That's a typical engineers solution to a problem when they have too much time on their hands and a workshop full of idle machine tools. I know 'cause I'm an engineer and I'd do the same. All the shinny metal and micrometer nudgers don't necessarily add accuracy but they sure do look nice [Tim Allen voice] Hurr Hurr Hurrr [/Tim Allen voice]

I had not thought of the rack centring error as a problem. Though it obviously exists, is it significant enough to worry about on a road(or even track day) car? I'm not expressing an opinion I'm just asking the question! Throughout the life of a car the Track Rod Ends will be changed, bushings will wear, and various bits of suspension will become bent. This might result in the (designed)centre position of the rack being offset from the "driving in a straight line" position. If this offset was 10mm how much would it affect the differential camber gain on turns in either direction? I don't know the answer or even how to work it out, but my gut feeling is that it would be pretty minimal and the least of your worries if things have worn or bent to that extent and replacing parts would bring everything back to within acceptable limits.

A slightly Noddy way of finding the centre might be to place tape on the steering wheel at the twelve O'clock position for full lock in either direction then return the wheels to straight ahead and trim such that the two bits of tape are either side of 12 O'clock. This assumes everything is symmetrical with the steering and suspension which is also probably wrong.

The more you think about this the more intricacies and complications appear. The trick (as with all things in life) is to know when to stop worrying about the insignificant things!
Leo

[Mr Whippy]

leorest said:

I had not thought of the rack centring error as a problem. Though it obviously exists, is it significant enough to worry about on a road(or even track day) car? I'm not expressing an opinion I'm just asking the question!

I'm asking the question too.

Imagine I turn 1/4 turn left, then take off the wheel, re-centre it, and then adjust the TRE's to point the wheels dead ahead.

Yes, a bit silly, the TRE's would probably be at their extents of adjustment, but the steering would in theory be noticeably unsymmetric.
Ackerman on the E46 M3 for instance is ~ 1.15x, so after 1.5 turns from centre the outside wheel has turned 1.15x more than the inside. over 1/4 of a turn that is maybe 2.5%.

So as you turn in 1/4 of a turn to the right say (90 deg) the left wheel thinks it already a bit turned left, so is turning faster than the right hand wheel (because it has to, to make up the ackerman).


Yeah, I'm going to extremes, and maybe it's something I shouldn't worry about, it's just a mental concern at how sloppy TRE replacement time and time again, along with just removing wheel and re-fitting it to straighten it, can introduce errors?

Will have a look through the Haynes manual for my car and see if there is any instructions on centring the wheel to the rack etc...

If anyone knows if TRE/rack/steering wheel true centre error can cause significant problems with ackerman effects on toe (and I guess camber as one strut rotates slightly quicker one way than the other if an error exists, so KPI effects on camber will obviously be in action too) then let us know

Cheers

Dave

[leorest]

This may help.
www.eland.org.uk/steer_intro.html
I know it's based on three wheels but it should give the principals

[Mr Whippy]

leorest said:

This may help.
www.eland.org.uk/steer_intro.html
I know it's based on three wheels but it should give the principals

Cheers

Dave

[Jaguarnut]

I've had some fun (!) with front wheel alignment. After having had a lot of new bushes and mounts fitted, I found I needed a new steering rack. I then found that the old one had been set up completly wrong. After many splinters in fingers scratching head, I realised that the solution was quite simple. Firstly, jack up the front of the car and support on axle stands, ensuring that the tyres are clear of the ground. Turn the steering wheel full to the steering stop and note its position (find some reference point). Then count how many turns it takes to the opposite full lock. It is likely to be some odd figure rather than a convenient 3 turns lock to lock. Having got that meusurement, devide it by 2. For simplicity then, the mid point would be say 1.5 turns from full lock on either side. Now in my case, I found the steering wheel position to be way off, and I had to remove the airbag to centre the steering wheel on the shaft. (Easy on my car but you need to know what to do with airbags). Once refitted, try it again. You should now find that at the mid-point of the rack travel between full lock left and full lock right, your steering wheel should now be in the straight ahead position. This should negate the effects of Ackerman! Now, lower car and take it for a test drive carefully. You may then find that to drive in a straight line, your steering wheel is off to one side slightly, or significantly. At this point, get the vehicle on a 4 wheel laser alignment rig, and ensure the operator locks the steering wheel in your new found straight ahead position. The system will now show the operator how much to adjust the wheel alignment on which wheel and by what amount. It worked perfectly on my Jaguar and it will go down a straight road, steering wheel straight ahead, and maintain a straight line without me adjusting it. Now that is good as my particular model is notorious for tramlining! Simple but effective!!!

[Mr Whippy]

Jaguarnut said:

I've had some fun (!) with front wheel alignment. After having had a lot of new bushes and mounts fitted, I found I needed a new steering rack. I then found that the old one had been set up completly wrong. After many splinters in fingers scratching head, I realised that the solution was quite simple. Firstly, jack up the front of the car and support on axle stands, ensuring that the tyres are clear of the ground. Turn the steering wheel full to the steering stop and note its position (find some reference point). Then count how many turns it takes to the opposite full lock. It is likely to be some odd figure rather than a convenient 3 turns lock to lock. Having got that meusurement, devide it by 2. For simplicity then, the mid point would be say 1.5 turns from full lock on either side. Now in my case, I found the steering wheel position to be way off, and I had to remove the airbag to centre the steering wheel on the shaft. (Easy on my car but you need to know what to do with airbags). Once refitted, try it again. You should now find that at the mid-point of the rack travel between full lock left and full lock right, your steering wheel should now be in the straight ahead position. This should negate the effects of Ackerman! Now, lower car and take it for a test drive carefully. You may then find that to drive in a straight line, your steering wheel is off to one side slightly, or significantly. At this point, get the vehicle on a 4 wheel laser alignment rig, and ensure the operator locks the steering wheel in your new found straight ahead position. The system will now show the operator how much to adjust the wheel alignment on which wheel and by what amount. It worked perfectly on my Jaguar and it will go down a straight road, steering wheel straight ahead, and maintain a straight line without me adjusting it. Now that is good as my particular model is notorious for tramlining! Simple but effective!!!

That sounds a good way of doing it, thanks.

If my rack is central then everything else from that must be.

Can't do this with the gti6 model though, as it has a right hand lock cut-off at about 90 degree's from the end so the wheel doesn't rub the gearbox
Fortunately my car has symmetric steering (I hope ) and so your method should work a treat.

Odd that cars don't have some kind of effective "TDC" on the rack or steering wheel hub.

Dave

[leorest]

I was following you until you said that putting the steering wheel on at a newly defined angle "should negate the effects of Ackerman". I don't see how this has done anything to the geometry.

I think I know what you are getting at and if I understand correctly you're using the lock limits as a datum to define the rack centre and then adjusting left and right toes with the rack in this new centre position?

[leorest]

Just thinking about the centring issue a bit more and it occurs to me that the important thing is the lateral distance between the inboard end of the track rod link, and the suspension pickup points, must be the same on both sides. When the rack is "centred" obviously.

In other words the centre of the rack is on the chassis centreline.

[Mr Whippy]

leorest said:

Just thinking about the centring issue a bit more and it occurs to me that the important thing is the lateral distance between the inboard end of the track rod link, and the suspension pickup points, must be the same on both sides. When the rack is "centred" obviously.

In other words the centre of the rack is on the chassis centreline.

Well, the chassis centreline isn't the best datum for that either really, or so the links posted above suggest

I think the idea is to find the centre of the rack by using it's extents, this then assumes that the ackerman effects are not present because as you say the tre links and the suspension pickup points are symmetrical at each side (we hope anyway)...

It is a mine field. This is kind of why I expected there to be professionals out there who just knew all this and could get your car 100% in half an hour with fancy equipment and good knowledge and £50 or so lighter...

Seems this area of alignment is one of those "lets sweep that fact under the carpet" kind of things because it opens up about 20 more cans of worms

Dave

[leorest]

agreed

[Jaguarnut]

Hey Guys, I think that I may inadvertantly caused you to go too deep now. The real issue is one of physics. Look at it this way. With all wheels aligned so that the car goes straight ahead without correction (road surface permitting), the steering wheel should be in the normal straight head position. The position of the rack body in relation to the chassis centre line is normally fixed by it's mounts and therefore is not the issue. The important bit is the actual rack bar inside. If the internal pinion driven by your steering column is in the centre of the rack bar, you will obtain the same amount of 'steer' be it left or right. In this position, the so-called angle of Ackerman is out of the equation. It may be then that you have dissimilar amounts of thread showing at each track road end, but in my opinion, this will be minimal and is not an issue. The three points then to avoid the pitfalls is to (1) centralise the rack bar and pinion, (2) ensure the steering wheel is then in the correct position (and the cancelling mechanism for your indicators - normally adustable once covers are removed)(3) have the front wheels set up with respect to the rears by a 4 wheel laser alignment rig. It works - I have proven it!!!