How I adjusted the toe in / out, camber and caster on my W123 300D - PeachParts Mercedes-Benz Forum

Stretch · #1 09-06-2010, 03:03 PM

G'day Folks,

I've recently rebuilt and renewed the rear and front suspension of my 1981 W123 300D. I've also attempted to do a four wheel alignment. I've done this for “fun” as a hobby. I plan to take my finished efforts to the dealer to get the ultimate verification of the method and my ability.

This method is not new – it is an amalgamation of information I've found from several sources.

This method is not a quick method – it takes a long time – it is fiddly and for many people I guess they will find it frustrating. It has the potential to save you money, however, there is no such thing as a free lunch – read on!

Quick note about safety:-

If you do this to your car you are potentially doing something dangerous. It is not only dangerous performing this technique - cars on slip plates do move! - but it is also potentially dangerous if you get this wrong. After adjusting suspension components don't head straight off into the sunset trying to break the land speed record. Take your time and be sensible – make sure your car is doing what you expect it to.

Warning:- At present I have not taken my car to the dealer to get a 4 wheel alignment to confirm the validity of this method.

Stretch · #2 09-06-2010, 03:04 PM

I'm sorry to start with a lecture but these irritating preliminary steps could potentially save you a lot of time and effort.

Before you start it is best to check

1)The condition of your tyres – bulging side walls for example could mess up your measurements
2)Tyre pressures need to be correct
3)The car should not be overladen – take out all of that stuff in your trunk!
4)The fuel tank should not be empty – it is best to do this with a nearly if not a full tank
5)The condition of your suspension components should be good
6)The car should be level AND on a level surface (this was difficulty for me)
7)Your wheel bearings should be correctly adjusted and your wheel bolts need to be tight.
8)Your wheels must not be damaged

I think these are the main things to check. Even so read through this thread for a better overview:-

http://www.peachparts.com/shopforum/showthread.php?t=134630

(Please do this: undoubtedly whunter is more experienced than I am)

Stretch · #3 09-06-2010, 03:05 PM

The first thing I did was to make up some slip plates and get the car on a level surface. From the pictures, you can see that my driveway is a mess. Over long distances it is approximately level but over short distances each concrete bit isn't. I ended up using plywood on the underside of the slip plates and checked the levels of each slip plate with a spirit level. It took a long time to sort this – I recommend using a better level surface like a garage floor if you can.

I made my slip plates from pieces of aluminium sheet with grease in between. You can use other stuff, it doesn't have to be aluminium. For example, I thought of melamine backed wood. Make sure that what ever you use it won't crush / splinter / break under the weight of the car. You just need two flat smooth surfaces with grease in between.

I planned to put the car on four slip plates, but as Internet shopping isn't always as reliable as it should be, only 7 of the 8 aluminium plates turned up... so I put the car on 3 slip plates. The right hand rear wheel was on the ground. This turned out to be a fortunate compromise. I've found that having the car on 3 slip plates works fine. The wheels move nicely on the slip plates and there is a sense of security that the car won't slip off and crush something. It is very easy to push the car about when it is on slip plates – I understand the warning given in this link now!

http://www.elantragtclub.com/id554.html

(This was found from this thread http://www.peachparts.com/shopforum/showthread.php?t=134630 )

I'll say it again => Working with a car on slip plates is dangerous: I found that a good check is to turn the steering wheel from lock to lock to see if the car slips off the slip plates. If it slips off then your car will not be on a level surface – you need to go back to the start and correct this.

Once the car was in position I bounced it up and down to get it to sit properly.

Stretch · #4 09-06-2010, 03:07 PM

I have added the “Optional?” bit in the title above because in order to adjust the ride height of a standard W123 and W126 (without level control suspension) you need to either replace the rubber shims that are fitted above the springs or you need to replace the springs... this is likely to be a bit extreme for most of us. However, I've added in a general method in case you want to check this out.

If you have different circumference wheels / tyres on the front and the back or you have decided to lower the front or jack up the back then you're kind of on your own. I don't know how to account for that... but the following might help:-

As far as the FSM chapter 40-300 is concerned (for a standard car) the W126 is level when certain suspension parts are within a specified distance.

Place the front wheels in the straight ahead position to check that the front suspension is level by measuring the control arm position. The FSM states that you need to obtain a mean value by pushing the body of the car down by about 30mm – measuring – and then pulling the body of the car up by 30mm and measuring. You add these two measurements together and then divide by 2 to get your mean value.

You are meant to use special tool 123 589 03 21 00 to do this – however I used a bit of wood, a spirit level, and an angle brace. You need to measure a vertical value between a position on the underside of the LCA below the lower shock absorber mount and the centre of the LCA inner mounting point – the eccentric pin.

The nominal value is quoted by the FSM to be 45mm +10mm / -15mm for a W126 with standard suspension up to 1987 (so between 30mm and 55mm). Disclaimer:- I couldn't find the value for a W123 so I used the W126 values. I guess it will be similar if not the same as the same type of suspension is used on both cars. THERE ARE LOTS OF OTHER VALUES for cars with different types of suspension so this value might not be good for you – check with your FSM!

For the rear suspension I used the same bit of wood, a different longer spirit level, and angle brace to measure the (rear) trailing arm position. Here you need to measure between the centre of the inner trailing arm bearing and the bottom of the constant velocity joint (axle can) closest to the differential. This measurement is appropriate for a standard trailing arm set up without starting torque compensation. The value for a W126 with standard suspension – no level control - is 38mm +10mm / - 12mm (so between 26mm and 48mm). Disclaimer:- I used this value for my W123 – again there are LOTS OF OTHER VALUES for different suspension set ups and configurations. If you have a trailing arm with torque compensation then you need to measure different points. Again check your FSM.

Stretch · #5 09-06-2010, 03:08 PM

This is a “very” optional step. You don't need to do this – but if you come across some unexplained problems with the procedure later on this step may help.

I decided to do this extra stage as I had previously discovered that there had been some welding work on my W123's sills which has resulted in a wonky driver's seat. (See)

I don't have the jealously guarded crash repair man's data of exactly where each part of the W123 body should be – but – I figured that if I measured between certain points on the underside of the car I could get a pretty good idea of whether the chassis is straight or not.

I chose to measure between the solid mount points, such as the differential mount, the sub frame attachment pins, the lower control arm mounts (eccentric pin), and either end of the stay that hold the LCA in place (the FSM calls this the brake support). In other words each easily accessible part of the chassis that is utilised to hold the wheels in place.

I used a plumb bob to transfer the positions of each point on the car onto a point on the ground. By chalking each position on the ground. I then rolled the car out of the way so that I could measure between, across, and diagonally from point to point. I built up a set of relative measurements from which I then made a scaled drawing (on a computer drawing package actually – but pen and paper is just as good) that would show if there was a misalignment.

Despite my worries – my car turned out to be fine. Each dimension I measured put each point within a few millimetres even though I was measuring with a tape measure on my terribly uneven driveway.

Stretch · #6 09-06-2010, 03:08 PM

You need to set the steering wheel in a straight ahead position before you start to set out your measuring points of reference. I managed to do this with the help of the steering lock – and I think I got away with it. The FSM says you need to fit a special pin into the steering box to locate the straight ahead position... or when the steering box has been removed you need to remove the steering wheel and align marks on the steering shaft. I elected not to do this. An alternative way would be to lock the steering wheel in position as shown in this link:-

http://www.elantragtclub.com/id554.html

slowrider240D · #7 08-22-2020, 11:50 AM

Should you not want to do the math, I calculated the following. I use these calculations with optical systems I have made to align my vehicles. I suggest the use of a laser pointer (sufficiently mounted and referenced to level) to do determine level and parallel for the wheel pads Thank you for having the patience and taking the time to post Stretch

When you consider that 0.002 inches (roughly 0.5 mm) is one minute of angle, PAY ATTENTION TO STRETCHE's admonition about bearing adjustment and wheel straightness. It makes a huge difference

14 inch wheel Inches mm
Diameter circle 14 355.60000
Circumference 43.982297150 1117.15035
1 degree (Circ/360) 0.122173048 3.10320
1 minute (Deg/60) 0.002036217 0.05172
1 second Min/60) 0.000033937 0.00086

15 inch wheel Inches mm
Diameter circle 15 381.00000
Circumference 47.123889804 1196.94680
1 degree (Circ/360) 0.130899694 3.32485
1 minute (Deg/60) 0.002181662 0.05541
1 second Min/60) 0.000036361 0.00092

Stretch · #8 09-07-2010, 04:14 PM

I'm still searching through my SD cards for those other photo's - it will probably be quicker to go and stage some new ones...

Anyway - does any one have any thoughts on the brakes on / brakes off issue?

Should brakes be applied when measuring on slip plates or not?

I got the feeling that allowing a little bit of movement on the wheels when measuring caster (with the turn the wheel by 20 degrees method) gave a more "realistic" wheel position. The point of wheel / slip plate contact only seemed to be about 20mm further round on the circumference - take a look at the photo in step 9 (post #10) there's a bit of masking tape with marks on it - I was tracking the movement you see...

rkpatt · #9 05-09-2011, 06:23 AM

Thanks for posting this thread . Please post more information about the toe spreader bar you made .

"Sorry for the lack of photographs – in particular I wanted to show the DIY spreader bar but I can't find that photograph at the moment. I'll post some more photographs if there seems to be a requirement for them when I find them. "

Stretch · #10 05-09-2011, 08:15 AM

Quote:

Originally Posted by rkpatt

Thanks for posting this thread . Please post more information about the toe spreader bar you made .

"Sorry for the lack of photographs – in particular I wanted to show the DIY spreader bar but I can't find that photograph at the moment. I'll post some more photographs if there seems to be a requirement for them when I find them. "

Don't worry it is on the list - along with the transmission rebuild, engine rebuild, paint, steering box rebuild etc etc etc - I'll get there in the end!

If I fake a picture now it will probably confuse people as all of the bits you usually see aren't there! But if you're in a hurry then I used this sort of thing => http://www.wolfcraft.de/jcatalog_generated/en/products/product_groups/14804_product.html If you scroll down to the bottom of the page you can see that the ends of this woodworking clamp can be switched round so that it spreads.

I've got a cunning plan as well to check to make sure that the spreader applies the prescribed force in the FSM too - that involves a spring balance and some bungee cords. Really simple - I bet you can work it out for yourself.

rkpatt · #11 05-09-2011, 04:52 PM

Great . I would like to see a picture of the wheel toe - in spreader bar you made when you can get to it .

QUOTE=Army;2714297]Don't worry it is on the list - along with the transmission rebuild, engine rebuild, paint, steering box rebuild etc etc etc - I'll get there in the end!

If I fake a picture now it will probably confuse people as all of the bits you usually see aren't there! But if you're in a hurry then I used this sort of thing => http://www.wolfcraft.de/jcatalog_generated/en/products/product_groups/14804_product.html If you scroll down to the bottom of the page you can see that the ends of this woodworking clamp can be switched round so that it spreads.

I've got a cunning plan as well to check to make sure that the spreader applies the prescribed force in the FSM too - that involves a spring balance and some bungee cords. Really simple - I bet you can work it out for yourself.[/QUOTE]

funola · #12 05-09-2011, 09:39 AM

Hey Army, nice work with the documentation of your DIY alignment rig! FYI, I have adjusted toe-in on all my cars for ages with a simple caliper that I make, without spreader bars. Set-up is simple, there isn't any! It is done with all 4 wheels on the ground. Some tells me my method will not work because I do no use spreader bars. My guess is the need for spreader bars (for toe-in adjustment) is required only if the tires are on sliding plates?

My proof that my method works is I never have uneven tire wear. That is good enuf for me!

Stretch · #13 05-09-2011, 12:53 PM

Quote:

Originally Posted by funola

Hey Army, nice work with the documentation of your DIY alignment rig! FYI, I have adjusted toe-in on all my cars for ages with a simple caliper that I make, without spreader bars. Set-up is simple, there isn't any! It is done with all 4 wheels on the ground. Some tells me my method will not work because I do no use spreader bars. My guess is the need for spreader bars (for toe-in adjustment) is required only if the tires are on sliding plates?

My proof that my method works is I never have uneven tire wear. That is good enuf for me!

Fair enough - I'm no expert - I just follow instructions in the FSM up to the point where it is about to cost me money for special tools. At this point I think of something to replicate the special tool.

Also what I would really really like to do is to adjust my caster, camber and toe with my bits of metal, grease and wood and then take it to the dealer and for them to say "it doesn't need any adjustment".

That would bring a smile to my face.

funola · #14 05-09-2011, 03:50 PM

Quote:

Originally Posted by Army

Fair enough - I'm no expert - I just follow instructions in the FSM up to the point where it is about to cost me money for special tools. At this point I think of something to replicate the special tool.

Also what I would really really like to do is to adjust my caster, camber and toe with my bits of metal, grease and wood and then take it to the dealer and for them to say "it doesn't need any adjustment".

That would bring a smile to my face.

When will you be bringing it to the dealer for an alignment? Ask them to give you a printout of the readings before and after so you can compare. Good luck!

Stretch · #15 05-10-2011, 03:29 AM

Quote:

Originally Posted by funola

When will you be bringing it to the dealer for an alignment? Ask them to give you a printout of the readings before and after so you can compare. Good luck!

The only reason why I'd do it is to get the bit of paper. It would be an expensive bit of paper but it could be a serious ego boost if I've got it right...

...alternatively I'll be looking like a right ninny.

Stay tuned to find out which!