An INCH of toe(in) at the rear will do it!
 

My car was squirrely in the rear, especially noticed this on uneven traction surfaces. Half the car hits icy patch other half on dry, the car dances all over, and I'm counter-steering and when I hit all-dry again the car is pointing in a new direction. Causing me white knuckles at lame 60 km/h on streets where 80 is posted speed.

Last year, I thought this was due to suspension links, so smart me replaced all 8 in the rear and put new rear shocks in.... me thinks me so so smart, until it finally snows again this year and ice reappears. I'm still all over the place.. I had been planning on 4-wheel alignment after doing all the links and just got around to it today.

The problem was 1 inch of toe-in at the rear :eek:!! I think that works out to be a few hundred yards of sideways drag for every mile traveled. That could explain some tire wear I was getting back there.

Guy adjusted it down to a "fat" 1/8 inch compensating for the slightly more than normal camber (springs softening, but not too bad). WOW! what a difference. I go straight now. What a concept. And I probably get a boost in fuel economy.

We stopped at the rear alignment because guy pointed out that outer tie rod end in front (drivers side) needs replacement. I told him I'll do that and bring the car back when done in a couple weeks to do the front. Didn't charge me for the half-job, just put my job on the wall with the others and said they can wait.
Decent.

The other thing he did was raise tire pressure all around. I asked why, he said the factory F/R 29/35 thing (that I was being religious about) was for original equipment tires that were probably rated 35 max in 1987. These tires (Nokian Hakkapeliitta are excellent winters for this car) are rated at 55 max, so he upped the rear pressure to 40 and put 44 up front ("because this car is heavy"). Said if it's too hard back it off. It is harder but still OK for comfort. Pavement is not dry enough to play with hard cornering to see how the "reversal" of low / high pressure front to back changes the dynamics... I did notice the Nokians road contact patch was not "flat" looking to the road, it did look under-inflated, a bit concave in the middle of the tread. So I am going to leave it as set and pay attention. There are probably many opinions out there about "correct" pressure. We'll see.

Hmm I just got my snows on and I swear I am getting some wiggles in my rear end. I'll drive it a bit more and see if it's just me.

I had my fronts aligned,but am getting a 4 wheel alignment next week.My problem is the fronts wear on the outside.The rears wear on the insides.So even with rotation I get half tire life. I have seen alot of VWs,and BMWs with the back wheels pushed out like that.
I'd like to know the cause.

I am so thankful this was not a post SUGGESTING setting the back tires at one inch of toe in.... There was not going to be anyway to straighten ( pun ) that situation out without hurting some people's feelings..
LOL

Mine was just like this until I did 4-wheel alignment. Also changed the front sway bar bushings. 50 cent part, but big job. I inflate mine to 33 front and 35 rears based on the say-so of some of the experts on this board. I've never understood why the fronta needed to be less than the rears (seeing as its got a really heavy engine to boot!) but on my fuel door cap, it also specifies more inflation in rear than front. That said, I've found that higher inflation really makes for a hard ride. Those Nokians are excellent tyres I'm told. Just can't afford them. :o

Snows on the rear only? They have much less grip than regualr tires so the rear will feel wandery comapred to the front.

I put the Hak Nordman 2 {the old Hak 1 with a new name} on all four wheels with 31 psi up front and 35 in the rear but I stow 200+ lbs of sand and cement for winter traction in the trunk.
The car definitely squiggles around a bit so you have to adjust your dry pavement driving style but the snow traction sure is good.

Show me someone that gets a rear alignment on a 115-123-126, and I'll show you someone that got ripped off...big time.

Can't be done by mere mortals.

>>so he upped the rear pressure to 40 and put 44 up front

That is really bad. Merc recommend higher pressure in the rear for good reasons. I think your mechanic may be a bit of a clown.

But do YOU know the good reasons? If not, you would be considered the clown when talking to this mechanic.

There's the "book learned" type, and then there's the "naive", there's also the "informed", and then there are the "experienced". I tend to put trust in people who are experienced, especially those who do Mercedes alignments on a regular basis for many years... over any of those other types of people speaking said topic.

I'll give it try, for snow tires in our region, maybe higher up front does magic. We're not cornering hard on the autobahn here in December.

No, I have them on all 4s. Either way that explains my wiggle.

Set your tire pressures correctly for the car. If you want to set them higher, keep the rears a couple of psi higher or set them the same. The car's handling is based on the specified pressures. Also, these high pressures are likely to wear the center of the treads and reduce traction. I wouldn't go much higher than about 35 psi. Also, I would install four snow tires, not just two.

If you really had one inch of rear toe-in, something must be bent. If this measurement was made by the same person who told you to overinflate the front tires, I would be very sceptical.

>>But do YOU know the good reasons?

Yes, of course I do.

Generally, mechanics are not experts in vehicle dynamics. Yes, they spend all day on the tools, but, their experience of engineering of vehicles in its broader sense is extremely narrow, and their advice to deviate from spec is usually ill advised.

As per Craig's post above, setting the tyre pressures in accordance with MB specifications is the right thing to do.

>>I would be very sceptical.

I agree.

Glad you got her figured out!

Would you care to share them with the rest of the class?

BTW, I run higher tire pressures than MB reccomends. I like the increased cornering stiffness I get from the higher pressures.