16v best alignment numbers.
 

Its alignment time for my stock 190e-16v. This car tends to understeer when pushed hard. Ive seen some old posts suggesting setting camber -1.0 and castor close to 10.0. How do these numbers sound for a stock 16v? Ive got to find a good alignment shop within 100miles of austin tx if anyone could suggest someone. Like many other mercedes owners my experiences with the tire shop and even alignment shops has not been confidence inspiring.

On a 16V alignment (changes) rarely will help understeer unless the alignment is WAY off now!

Those figures will work well for a stock 16V as long as the lower control bushings are GOOD.

The stock 16V doesn't have enough front sway bar! That is the reason for understeer.

Front alignment did help reduce the understeer on my 2.6, which is front heavy.

I just set the cam bolts for for maximum negative camber and maximum positive caster, equal on both sides and ended up with negative 3/4 degree camber and plus 10.5 degrees caster. The combination of increased negative camber and increased positive caster will keep the outside front tire closer to vertical relative to the pavement as the steering angle and body roll increase. Turn-in is crisper with less understeer at the limit, and the tires are wearing evenly.

Using this alignment method you just rotate the cam bolts on both front and rear locations of both control arms to push the bolt axes as far outboard as possible. Then you back off the highest caster and camber readings to make both side equal. Tighten the bolts and then set the toe-in.

A larger front anti-roll bar will increase front roll stiffness, which will increase understeer unless the rear roll stiffness is increased to compensate via stiffer springs or a larger anti-roll bar.

Duke

Thanks for the responses,M.B.doc I didnt mention that there is definately to much toein. Tire wear confirms that. Duke I noticed some posts of yours concerning alignment using an inclinometer. I remember when I was a kid that was standard procedure, nothing electronic back then. How do you get the instrument in contact with the wheel rims? Ive seem some very accurate electronic inclometers for construction use but they are way too short to span the wheel rim to rim.

IF the alignment is way off then understeer can happen! As I stated before! However if the alignment is in specs now changing by 0.25-0.5 deg won't have any real effect!

AS I have raced & autocrossed MB's for over 10 years I can tell you that a larger rear bar has little OR no effect on a 16V. In fact on track we went to a regular 8V bar on the rear! 2MM smaller
Autocrossing we disconnect the rear bar, & that allows the rear to hang out & give oversteer.

M.B.DOC, interesting about the rear bar. Was the 8v change to a softer bar due in part because of the open diff vs the limited one in the 16v? Im also due to change the rear "tie-rods" as they have developed some play. Aside from the slight woggly feeling I wonder if that could contribute to the understeer behaviour? What rear numbers work for you?

I just use a little Sears mechanical inclinometer that has about a six inch long base and a good carpenter's tape for toe measurements.

I lay the inclinometer on the outside of the bead flange. You need to be careful (and consistent), and it is time consuming, but I had one alignment job checked on an electronic alignment machine and it was within 0.1 degree of my measurements.

The inclinometer can be used to measure camber directly with the wheel straight ahead. Caster is the arithmetic difference in camber readings with the wheels at the extremes of steering lock.

Say you turn the wheel to extreme left and the LF wheel measures +6 degrees camber with the inclinometer. Now turn the wheel to the extreme right and the camber measures -4 deg.

Caster = 6 - (-4) = +10

Likewise for the RH side.

The other thing you need is a level "surface plate". Most home garage slabs are level and will work well enough to align a production car, where 0.1 degree accuracy quite satisfactory. Every time you make a change you must roll the car for and aft until you eliminate the tire scrub, which is part of why it is time consuming, but I got tired of alignment shops doing it "their way" instead of "my way" and with the exception of getting my MB dealer to check my alignment on warranty (referenced above) I haven't seen the inside of an alignment shop for 25 years.

They have great equipment, but I never met an alignment tech that really understood alignment and suspension geometry, and they always resisted setting the car to my specs. They always wanted to use "factory specs". Alignment is a handling "tuning parameter" just like ignition advance map, and I like to set my cars up to respond as well as possible when driven at the limit. Most OE settings are established to yield "safe and sane" understeeer at the limit, which is usually too much for my taste.

Duke

Well ive been browsing around looking for info in DIY alignment. One site said to turn the wheel 20deg rt, measure then 20deg lf, measure. They seemed to believe that equal turns (+-20) was important. Another site mentioned that the wheel axial was slightly offset from the steering axis making it difficult to compute castor. It seems these factors have had minimal influence on your alignments.

Heres the stock specs for the 16V:

Front Wheel Alignment Specs:

Camber:
(1)Wheels straight ahead...................................-0~30 min. to -0~

Max. difference between left & right.................0~20 min.


Caster:
(1)Wheel straight ahead.....................................10~30 min. +/- 30 min.

(1)Via Wheel lock...............................................10~ +/- 30 min.

Max. difference between left & right..................0~30 min.

(2)Toe-in............................................................0~20 min. +/-10 min.


Notes:
(1)...............Tolerances for test only. Try for nominal value for adjustment.
(2)...............Wheels at the front with 90-110 N spread.




Rear Wheel Alignment Specs:

Camber (at level) mm:

+20.................................................-0~55 min. +/- 30 min.
+10.................................................-1~10 min. +/- 30 min.
0....................................................-1~25 min. +/- 30 min.
-10.................................................-1~40 min. +/- 30 min.
-20.................................................-1~55 min. +/- 30 min.

Toe-in:

Level ready to drive............................+0~35 min. to +0~20 min.
Permissible range per wheel................between +0~30 min. & -0~05 min.

The method I use is based on some archane Euclidian geomtry prinicipals, and I just use max steering lock both ways and don't worry about the angular displacement. My method does not yield exact caster, just an appromixation that is in the ballpark. What I really want is maximum available caster in the positive direction equal on both side and the approximation assures this.

I've been doing my own alingments for 25 years on cars with recommended caster from slightly negative to the Merc's plus ten. In all cases I set them to maximum negative camber and maximum positive caster (or as far in the positive direction as the adjustment would allow) and then backed off the highest settings to equal the lowest on the other side to equalize everything.

It's worked very well for me.

Duke

You couldn't live with the tire wear that would happen with the race car set-up! I ran almost 3.0 deg of negative camber on both front & rear. But on the auto cross car I ran about 1.5-2.0 negative camber(front & rear) with very little toe-in on both front & back. ON both cars I maxed out the caster for the MOST possible! Also used camber plates(race car) on the upper strut mounts. BIG difference there!

The race car has a welded(locked) 4.08 or 3.92 ratio differential. The factory limited slip doesn't take the power going out of the corners after 6-7 laps at speed!

Auto crossing we used a 3.56/1 or 3.67/1 limited slip and rarely had any traction problems! OF course that is with decicated Hooiser tires! The tires WILL make a big difference on handling! 2-3 seconds on autocross!

However I sold both cars last November! SAD DAY!

I really appreciate all the input for everyone on this! The little 16v deserves good treatment so I want to stay on top of it. Ill post results of alignment and new tires for the lists reference.

Thanks agian!
TomP.

One thing I forgot to mention is that though I generally set all my cars at the maximum negative camber/maximum positive caster (and equal on both sides) available with the adjustments, I do not recommend going beyond negative one camber for street driving to prevent the occurance of excess inside tire wear. If you drive your car on the street and weekend race, then you have to accept some sort of compromise.

The maximum available negative camber, equal on both sides, on my 190 was negative 3/4 degree, so that's where it's set and I'm not seeing noticeable inside tire wear.

My Cosworth Vega is set at negative two degrees front camber, and it is causing higher inside wear on the Toyo Proxes RA-1 DOT legal racing tires. Since I haven't run a track event for some time, I'm thinking about backing it down to minus one.

Duke

Hi Duke, Ive checked out a few inclinometers including one at sears. Boy, its sure hard to see 1 deg on them. Plus at that small angle the needles seem slightly sticky. I guess this just takes a lot of patience?

Yes, DIY alignment is time consuming and requires patience, but once you get it set correctly it should hold. I can read my inclinometer to about a quarter degree and I adjust both sides to the same interpolated readings, and as I said previously when I had my 190 checked on an electronic alignment rack the readings were within 0.1 of what I had recorded as final numbers when I realigned the front end.

After I took initial measurments, I just set the all the pivot bolt to their extreme outboard position, which will yield maximum negative camber and maximum positive caster, then I backed the high camber reading down to the low reading, then did the same with the caster and rechecked everything, Once I was satisfied that I had maximum neg. camber and max. positive caster, equal on both sides I torqued the bushing bolts. Be sure you do this at normal ride height.

The final adjustment was toe.

Duke