W126 Rough Front End Alignment? - PeachParts Mercedes-Benz Forum

JamesDean · #1 06-25-2013, 01:04 PM

Hey everyone,

Tonight I plan on finishing the front end rebuild on my 420SEL.

I need to get the camber and caster---I think those are the correct terms set to acceptable/drivable values.

The guide rod needs to be set and the control arm eccentric bolt position..

Does any one have a rough method of doing this? The FSM said to put the LCA bolts at the center position. I did that as best as I could. Not sure about the guide rods though. I left 4-5 threads exposed on the back side.

The tie rods were not adjusted. I just removed the steering arm from the spindle.

Anyway, thanks!

Stretch · #2 06-25-2013, 03:04 PM

If you want a really rough alignment do it by eye for a castor adjustment - the wheel shouldn't be too far back or forward in the wheel arch. Place spirit level with a vertical eye up against the tyre for camber and for toe a long straight bit of wood point along the car will give you an idea.

This is pretty rough though!

JamesDean · #3 06-25-2013, 03:08 PM

All I need to do is get it to the dealership so they can properly align it. Dealer is <25 minutes away.

If all goes well tonight, I'll be able to drop the car on her wheels and see how it looks. With ANY luck...it'll be acceptable enough that I won't have to make adjustments.

97 SL320 · #4 06-25-2013, 10:27 PM

The only way a bubble level works is to have the car on a level surface.

A rough way is to use a framing square on the ground and measure the distance from it to the top and bottom of the wheel. ( Not the tire as there is a bulge at the bottom. ) The tire should be square to the ground or slightly tipped in at the top.

More importantly, the toe must be set as that will affect stability much more than camber / caster. To measure, use an angle or 1" square tube pressed against the tire. Be sure to place the material above the tire bulge but not so high as to cause the measuring tape to hit parts under the car.

Measure between the material in front and rear of the tire, they should be equal or up to 1/8" shorter at the front.

Stretch · #5 06-26-2013, 12:13 AM

Quote:

Originally Posted by 97 SL320

The only way a bubble level works is to have the car on a level surface.

...

Good point I forgot to mention that - though I think JamesDean is experienced enough not to try to do this job with one wheel up on the curb or something like that!

Quote:

Originally Posted by 97 SL320

...

More importantly, the toe must be set as that will affect stability much more than camber / caster. To measure, use an angle or 1" square tube pressed against the tire. Be sure to place the material above the tire bulge but not so high as to cause the measuring tape to hit parts under the car.

Measure between the material in front and rear of the tire, they should be equal or up to 1/8" shorter at the front.

Absolutely, the wrong toe will most certainly give a very weird feeling. I have tried many times to measure toe roughly across the width of the car as you suggest. In my experience these smaller measurement distances are harder to get right than to assume that the rear wheels are straight and to then try and get the front wheels to be "turned" parallel to those at the back. I have found that it is best to simulate the laser guided hanging targets on the back wheels method of alignment such as this =>

<= than to try to measure across the width of the car.

To be honest I think the whole concept of taking your car to someone else to be aligned quite a weird one when you can easily out perform any gucci laser calibrated system with the box of string method.

JamesDean · #6 06-26-2013, 12:46 PM

Well good news! I dropped the 420SEL off the jack stands last night and the alignment was acceptable enough to take to the dealership.

When I dis-assembled the entire thing I left the tie rods alone, just taking off the steering arms. So i think that helped keep things together.

The only issue I had was the camber was off a little, probably castor as well. Steering was OK. "Center" was at about 2 o'clock somehow but when the wheel was "centered" the car drove straight and I had no problems controlling it over the 10 mile journey.

Eh when it comes to alignment I plainly don't care enough to do it myself. I've no problem paying someone to do a proper job on it.

JamesDean · #7 06-26-2013, 06:15 PM

SIGH.

The dealership said they made the front end too high and they couldn't align it.....

I used the 4-nub spring pads like was previously installed on it. We double checked the springs..the old ones were just as tall as the new ones....

The EPC reported that the part numbers were compatible..
(left spring)

JamesDean · #8 06-26-2013, 06:31 PM

I wonder if my spring shims are too thick...I've got the 4 nub, 23mm ones. They were on the old springs, I just bought the same size.

My friend's 560SEL has 1 nub 8mm ones.... Hmmmm

Stretch · #9 06-27-2013, 01:32 AM

The reason why they have one nub, two nub, three nub four (day time comes and I wanna go home!)...

...is that there might be slight differences in chassis structures as well as the springs and the bushings and the other suspension parts. Comparing car with car isn't necessarily the same as comparing apples with pears but a little bit like that. As the dealer said it was too high I hope he said by how much. There are limits in the FSM that compare parts of the suspension with other parts - i.e. making the car level. With this information it is easy to work out the size of the pad / number of nubs.

But I guess he didn't actually measure that did he.

JamesDean · #10 06-27-2013, 08:28 AM

Well I did some checking with FSM.

It looks like I do indeed have the wrong springs. Contrary to what I believed the "points system" applies to springs and not to pads.

The spring I have is 126 321 18 04.

The base point value for the 420SEL is 48. Add 2 points for the sunroof and you've got 50.

50 points to spring 126 321 17 04. Now based on some color code thing that I am not quite sure on, it can use either a 18mm or 23mm pad. SINCE my old springs were the 17 04 springs and they had the 23mm pad..I can assume I will be safe with the 23mm pad once again.

Additionally you can see in the chart below the 18 spring is slightly taller, slightly stiffer and has thicker coils.

Where I went wrong was just checking the EPC which said, yeah the 126 321 18 04 is compatible with all 126 front ends. This, technically, is true however you have to apply the point system.

hookedon210s · #11 06-27-2013, 08:54 AM

Quote:

Now based on some color code thing that I am not quite sure on

Mercedes color codes certain parts to denote tolerances in manufacturing. Your springs should have a slash of either blue or red paint which will tell you which spring pads should be used for a given points value. Based on 50 points and the 126 321 17 04 spring, blue-marked springs would use the 18 mm thick pad and red-marked springs would use the 23 mm thick pad. Unfortunately, the 126 321 18 04 spring does not appear to be compatible with your car but if you happen to have the red-marked springs you may be able to make it work with the 8mm thick pads. Mark

JamesDean · #12 06-27-2013, 09:13 AM

Thanks for the clarification.

Now, my new springs likely will not have these color codes on them as they are not direct from Mercedes. I've never seen the color marks on "new" springs either.

hookedon210s · #13 06-27-2013, 01:35 PM

Quote:

Originally Posted by JamesDean

Now, my new springs likely will not have these color codes on them as they are not direct from Mercedes. I've never seen the color marks on "new" springs either.

Even if they are not OE if they are German they probably will. If I were you I would buy the 8mm pads and give them a try rather than buying new springs. Due to the geometry of the front suspension the change from 23mm pads to 8mm pads will decrease the ride height by more than 15mm. I would bet that your ride height won't be any more than 1/2 inch higher than normal. Mark

JamesDean · #14 06-27-2013, 01:46 PM

None of the Lesjofors that I've bought in the past have had any paint marks on them.. At least none that are as obvious as the factory springs.

I ordered the new springs last night.

I have two 300SDs that have original springs still so "old/incorrect" springs will have a future home for sure.

I wasn't able to find a 8mm pad on the same website as the one I bought the springs.

My parents were planning on a trip to Philly Monday of next week and I was set to have the car finished in time. The springs were a set back but the place I bought the "new" springs from typically ships quick and arrives within a day.