Grass Roots Toe Adjustment Methods

I have had several requests to describe homebrew toe test and adjustment methods. I have written them numerous times on this forum over the last almost 12 years, but here we go one more time since I have received one very recent specific request.

The vast majority of front tire wear problems are related to toe adjustment. If both front tires are wearing only on the inside or outside edge, then there is about a 99% chance that the problem is incorrect toe adjustment. If both tires are wearing on the inside edge, it is toed OUT. If they are both wearing on the outside edges it is toed IN.

Many alignment specification sheets will indicate a small amount of toe IN. If your goal is maximum tire life, FORGET that specification table and set the toe on ZERO.

Before setting toe make sure that all steering linkage joints are TIGHT. This would include tie rod ends on both end of the outer links and the idler arm bushings. Also ensure that both wheel bearings are properly adjusted with no slack.

Do not measure between particular grooves in the tire tread for setting toe. Tires do not mount perfectly onto rims, so the grooves can be at different points relative to the wheel as you go around the circumference of the tire. Shop based alignment equipment reference the wheel rims for alignment. With my home methods I take this into consideration so as to compensate for any anomalies in tire tread position relative to the wheel.

If after the first series of measurements in either method there is a difference in the measurements, loosen both lock bolts on each tie rod link, this is four bolt and nut combination total. Before turning a link for measurement pay close attention to the directions of the threads. If the steering wheel was centered properly before adjustment procedure, turn each link an equal distance to maintain a centered steering wheel. To adjust toe, either in OR out, turn both links in opposite directions.

If toe is zero, but steering wheel is not centered, turn both links the SAME direction equal amounts in order to maintain toe adjustment, but move the position of the steering wheel.

After finished REMEMBER to retighten all four tie rod link lock bolts and nuts.


Thumb Tack Method:

Press a thumb tack into the deep portion of the tread on each tire on the front of each tire just below a level that allows a tape measure to reach side to side in front and aft of the tire. With both tacks at the same level, measure between the tacks and make note of the measurement.

Roll the car forward far enough for the tacks to be close to the same height, but behind the wheel centerline. Measure again between tacks and if the distance is not the same as previous measurement, adjust tie rods an equal amount on each side and repeat fore and aft measurements moving the car foreward or rearward as necessary for fore and aft measurements. Continue adjustment until the measurements are the same between tacks while tack is either fore or aft. When the measurements are the same, you have achieved ZERO toe.


Tire Scribe Method:

Raise a front wheel safely such that the wheel is suspended and can be turned. Using a pair of vise grips, clamp a good sized nail to the top of a jack stand and position the jack stand such that the nail presses into a flat portion of a raised tread. Turn the wheel 360 degrees to scribe a line all the way around the tire sort of like doing it with a lathe. Repeat on the other front wheel.

Lower the car and roll it at least one full rotation of the tires. This will allow the wheels to seek their correct camber locations after being raised and lowered.

At a level just low enough to miss obstructions in front of and behind the front wheels, measure between the scribed lines. Make note of measurement and make the same measurement between the scribed lines on the back of the tire. If both measurements are not the same, adjust as described above.


Finishing Up:

Don’t forget to retighten the tie rod link lock bolts and nuts after any adjustments were made.

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2001 SLK 320 six speed manual
2014 Porsche Cayenne six speed manual

Annoy a Liberal, Read the Constitution

You forgot the string method, you'll need a string, a ruler, wrenches for tie rods, and I use jack stands to hold the string up at the right height.

Do one side at a time:

Car on a level floor, steering wheel straight (no matter what the wheels are doing), pull a length of string along one side of the car (bumper to bumper) making it level with the center of the wheel hubs (front and back). Mercedes mags are great for this because the tri-star logo on the hub gives you a bullseye for center hub. Move the string so it's the same distance away from the front and rear hub center point, 2 inches is a good working distance from the string to the bullseye. This is your "laser line".

Now, do the toe adjustments. Wherever the string passes a wheel rim (twice at the rear and twice at the front), measure the distance from the string to the rim. Adjust the wheel toe making the two rim-to-string distances at that wheel the same. Do this by turning the tie rods until it is so. When that happens you have zero toe on that wheel. Tighten tie rod in that position, move on to next wheel.

Having some dusty dirt under the wheel makes it easier to move the wheel by turing the tie rod, yes you can do this by reaching in from behind the front wheels with a wrench, lay on the ground.

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Cheers!
Scott McPhee

1987 300D

Zero toe *can* cause tire wear. Sometimes positive toe is specified to offset inner tire wear due to specified negative camber. Bushing deflection can also be a reason that positive or negative toe is specified.

The newer cars I deal with tend to have toe specified closer to zero on the front axle, with the FWD models going a little more to the negative toe range. The W123, W124 platforms specify a lot of toe, considering that they want you to use a spreader bar and still dial in positive toe.

To help readers, maybe describe negative versus positive toe.

And what bushing deflection is.

__________________
Cheers!
Scott McPhee

1987 300D

Good method AS LONG AS you are doing it on a car with the same track front and rear. I have no idea what cars do and do NOT fall into these categories, but I know there are some with different track front to rear.

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2001 SLK 320 six speed manual
2014 Porsche Cayenne six speed manual

Annoy a Liberal, Read the Constitution

The spreader bar is a much more important issue with the 124 as compared to the 123.

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2001 SLK 320 six speed manual
2014 Porsche Cayenne six speed manual

Annoy a Liberal, Read the Constitution

If you want to make sure everthing is centered to begin with:

If you go to someplace like samstag you will see that they have a Tool that goes thorugh a Plug Hole in the bottom of the Steering Box to center the Steering Box and the Steering Wheel if the Wheel is on correctly to begin with.
The Tool is expensive for what it does but you can have one made from a Bolt; See pic.
The Pic shows the Bolt and at the bottom of the Pic the original Plug (the Plug has a Copper Crush Washer).

When it is installed not much Fluid leaks out but you cannot leave it over night with out Putting a O-ring on the Bolt/Washer.

Also a good idea to put a Note on the Steering Wheel to remind you to remove the Tool before trying to drive the Car or turn the Wheel.

Attached Thumbnails

 

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84 300D, 82 Volvo 244Gl Diesel

@air and road and scottmcphee, thankyou for this.

I am also going to utilize two pieces of 2x4 lumber, a scissors jack and a bathroom scales as my spreader bar and then try to align it.

I have got some spare 1x1 ft plyboard and going to use salt as the bearing surface - grease would work too I think, the wheels would rest on the squares.

Great help.

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2012 BMW X5 (Beef + Granite suspension model)

1995 E300D - The original humming machine (consumed by Flood 2017)
2000 E320 - The evolution (consumed by flood 2017)

The main reason for a slight toe-in is to keep all the steering components loaded in one direction, effectively reducing play.

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'83 300D, 126K miles.

For the most part, toe in is a carry over from the bias ply tire days. Not nearly so necessary with radials. I have run a number of cars with zero toe and had excellent tire wear as a result.

My wife had a Mini Cooper that my daughter wrecked. It had about 100,000 miles at the time of the accident and never had any tire wear issues. After the accident it went through a pair of tires so fast I didn't even notice before they were gone. My wife took it to the shop where the work had been done and after setting it up on the machine they said everything was within spec.

I didn't even think of checking toe because I thought something was wrong as a result of the accident. I took it to my own local shop and they said everything was within spec. I asked them if I could go watch the process. The guy set it up on his $30,000 worth of Hunter gear and it was showing significant toe in. He defended himself by showing me the book that indicated that much toe in was within spec. He wasn't very cooperative, so I took it home, got out the jackstand, nail, vise grips and tape measure. The wife and I set it in the driveway and tires lasted seemingly forever after that.

I've had similar situations, although not so drastic with MB's. If you want good tire wear, set it on zero.

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2001 SLK 320 six speed manual
2014 Porsche Cayenne six speed manual

Annoy a Liberal, Read the Constitution

The people who built the car were some of the best mechanical engineers in the automotive world, and then they tested the cars, more than almost any other company in the world. So when they give a spec for toe in, IMHO it is best to listen to them as they have the data and testing to back up their decision.

This / \ <--- is tow in, if the motion of the car is upward and the slashes are the wheels

This \ / <--- is toe out, if the motion of the car is upward

The reason to add some toe in is that the forward motion will tend to push the wheels rearward, flexing the steering linkage as well as taking up any play, and theoretical tow will achieve zero. If a brand new car requires some toe in (as per the specs), then one with some wear will need more toe in. An IR heat gun pointed at the tread can often indicate how the tire is tracking, hotter to outside = toe in, hotter to inside = toe out. Equal temp across the face of the tread would be optimal, what were looking for.

As stated, centering the steering is PARAMOUNT to the start of the alignment process.

But there is another part of this process to consider. As each front wheel is individually and independently adjustable, each wheel can thus be "pointed" in any direction, without respect to the centered steering gear, or the other wheels setting.

To get both front wheels correct, and to keep the steering gear centered, you must reference each wheel to the centerline of the car. IOW, you must simultaneously correct toe, while keeping the steering gear centered, while also referencing that both wheels are aligned to the vehicles centerline. If you fail to reference the centerline, you can have proper toe, yet still have both front wheels turned slightly left or right, and your steering wheel will be turned going straight ahead.


To achieve the greatest perfection, every bit as good as ANY alignment shop, you can simply run strings down both sides of the car, making them parallel to the cars centerline and outboard a short distance, 6 inches per se, and at a height even with the wheel centers. Now you can measure between the string and the wheels rim edge and simply need to equalize everything. With strings set up properly you can also check rear toe, though its generally not adjustable.

Four jack stands, two pairs, each pair with a long wood stick across them set one set to the front, and one to the rear. Tie strings equal and accurate distance apart on both sticks, and move each of them right or left as needed to bring them parallel to the cars centerline while keeping the strings taut.

I learned wheel alignment in Vo-Tech, and did it professionally at a tire shop for about a year. I quit shortly after being sent to a class put on by MOOG, in which its purpose was only to SELL parts. Alignment shops dont make any money doing alignments, they make their money telling you steering parts are worn out and selling them to you. With most shops at $100 or more an hour labor, how much labor do we expect to get out of a $49 alignment, which today usually is only a "check", adjustments are often extra.

30 years ago no one really heard of doing it themselves, we all thought we needed that $30,000 Hunter or Snap-On alignment rack with the fancy ligh beams and mirrors. While I can admit I havnt yet figured out how to check king pin angle, its actually never adjustable anyway and really not needed.

Having that knowledge and experience, in the years following that job and as I brought cars into different shops for wheel alignments, I became disgusted. When I did them I took the time to get it right, and was always getting yelled at by the boss for taking too much time. I wasnt there to fix things, I was there to sell parts and labor. In fact, I was there to sell parts that wernt even needed. Each shop I went to over the years that followed,cut great corners, and gave me back the car no better than when I drove in. They almost always tried to sell me something too.

The final straw was a 78 Mercedes 300D that had the engine crossmember repaired after a collision, in which the pitman arm are got mangled, and I just wanted it aligned. I got the car back with the steering wheel not straight, and when I came back to complain, and got a bunch of BS double talk how it was "impossible", decided then and there I would figure it out on my own. It made even more angry when I found the tool kit missing from the trunk when I got home. I have not had any car on an alignment rack since that day, and never intend to again.

Heres a good site that shows much of the basics and explains it all quite well http://www.hotrod.com/techarticles/chassis/hrdp_0411_wheel_alignment_guide/viewall.html

Good point!

I just found w124 has front/rear track: 59/58.7 inch (1501/1491 mm).

So, adjusting like I mentioned would give me a slight toe out.

With a 2800mm wheelbase, I figure that's around 0.041 degrees toe out (per side).

To correct for that, on my 15" rims, the rim to string measurements would not be equal. For zero toe, I'd have to see 0.14mm more distance to the string at the leading edge of the rim, and see 0.14mm less distance at the trailing edge, using center of hub as the standard. Or more simply, I should see a difference of distances between leading and trailing edge measurements of about 0.28mm (about 11 thousands of an inch).

I feel this is within error margin of most string thicknesses and measuring tools. For a w124 I think "going for equal" is good enough, and maybe error on having smidgens more distances at the leading edge. ... considering I don't use a spreader bar which would force more toe out if it were used and we'd want to compensate for that.

__________________
Cheers!
Scott McPhee

1987 300D

I think this is the preferred way to describe toe. When I hear the phrases positive and negative toe, it casts the question "which is what?" that is laid to rest if everyone just agrees and uses toe in or out.

__________________
Cheers!
Scott McPhee

1987 300D

I obtained 4 somewhat damaged linoleum square foot tiles for free from the hardware store (scraps nobody would purchase), and made two grease sandwiches from these. Slip one under each front wheel.

Slippery stuff! You don't need power steering at all with these things under your front tires, can turn the wheel with your pinky finger.

__________________
Cheers!
Scott McPhee

1987 300D