Geometry problem?

[hedges88]

I have a problem with my 2009 Mercedes A class. I always feel I have to steer right slightly all the time and centering the steering wheel dead on results in a slight left steer.

I got a free inspection at Kwik-Fit for alignment just after I had 4 brand new tyres put on as apparently it's best to setup the alignment when the tyres are new

I don't really get much of a pull under braking, probably no more than normal driving but accelerating does definitely make it pull left more. Kwik-Fit did not charge me for a front alignment because it did not need doing. The rear right toe was out of tolerance but only just.

Could this problem be caused solely by the rear right wheel being out? As it's a parabolic rear axle it cannot be adjusted. The only issue I'm having that's noticeable is a high pitch sound coming from the area of the wheels especially at high speed/motorway it goes away if you turn left but worse if you turn right. I looked on the internet and it said that it can just be a build up of brake dust etc??

I did say the car was a CAT C write off but he says from looking at the machines results there is no reason to think the chassis is bent or anything. I don't really understand much about the printout attached but if someone could confirm what I've been told is true or not I'd sure appreciate it.

[E-bmw]

If your noise gets worse when steering, the weight shift on the bad wheel bearing is highlighting the issue.

eg. Worse when turning right means a left wheel bearing, you just need to isolate if it is front or rear.

Also, just because the alignment is good doesn't mean you don't have a suspension issue, the operator doing the alignment should have checked everything is tight/not worn etc before doing the alignment, as any problems need fixing before an alignment or it is a waste of time.

[hedges88]

E-bmw said:

If your noise gets worse when steering, the weight shift on the bad wheel bearing is highlighting the issue.

eg. Worse when turning right means a left wheel bearing, you just need to isolate if it is front or rear.

Also, just because the alignment is good doesn't mean you don't have a suspension issue, the operator doing the alignment should have checked everything is tight/not worn etc before doing the alignment, as any problems need fixing before an alignment or it is a waste of time.

Ah okay I'll get the wheel bearings and suspension checked. The tyre fitter and MOT tester did say everything seemed good with all that stuff but I guess they are very brief inspections

[LennyM1984]

I am not an expert but I know just about enough to be dangerous...

The 14 minute thrust angle will cause what you describe under acceleration. I'm not sure what the fix for your car would be but a decent specialist could probably advise. In essence, your rear wheels are wonky and are forcing the car to go down the road at an angle. You'll notice this more under acceleration as the rear axle is loaded up.

Kwik Fit are muppets. You have toe in on one rear wheel and toe out on the other. If you draw this on a piece of paper, you'll see why it doesn't go straight.

In terms of the front axle, you car is not pointing quite straight when the wheel is centred (a car will naturally find an equilibrium where the side to side toe is equalised when moving in a straight line). This means that to go straight, you're steering wheel will be slightly off to one side. This should be an easy fix (tweak the tie rods)

Edited by LennyM1984 on Thursday 10th February 11:19

Edited by LennyM1984 on Thursday 10th February 11:22

Edited by LennyM1984 on Thursday 10th February 11:24

[hedges88]

LennyM1984 said:

I am not an expert but I know just about enough to be dangerous...

The 14 minute thrust angle will cause what you describe under acceleration. I'm not sure what the fix for your car would be but a decent specialist could probably advise. In essence, your rear wheels are wonky and are forcing the car to go down the road at an angle. You'll notice this more under acceleration as the rear axle is loaded up.

Kwik Fit are muppets. You have toe in on one rear wheel and toe out on the other. If you draw this on a piece of paper, you'll see why it doesn't go straight.

In terms of the front axle, you car is not pointing quite straight when the wheel is centred (a car will naturally find an equilibrium where the side to side toe is equalised when moving in a straight line). This means that to go straight, you're steering wheel will be slightly off to one side. This should be an easy fix (tweak the tie rods)

Edited by LennyM1984 on Thursday 10th February 11:19

Edited by LennyM1984 on Thursday 10th February 11:22

Edited by LennyM1984 on Thursday 10th February 11:24

Thanks for the information. I took my car to the sandwich platform car specialist I go to for my timing chain and thermostat replacement. He said you can see with your own eyes the front wheels are not aligned just visually. He has said that it's an easy fix on the A class, you can loosen slightly where the damper meets the body and move it into a better position.

The rear alignment would involve replacing the entire rear sub-frame. I may have an accident repair centre do an inspection of the vehicle. It was written off at just 3 years old with very low mileage when it would actually have been a fairly expensive/valuable car (VW Golf money). I had to call the DVLA to find out what category the car was because all the logbook says is something along the lines of structural damage beyond economical repair or something like that but doesn't show the category.

Ever since my new tyres were fitted I get bad hopping and skipping at near or on full lock when parking. Blackcircles said it was just due to the freezing weather at the time and they would be okay when the weather warmed up. They haven't improved at all so I complained again to be told that it's normal for Mercedes to do it! Then when I visited Mercedes-Benz last they said it was because the tyre's I put on were not marked "MO" which indicates they have been approved or tested to work for the car. So I am a bit miffed at Blackcircles because they had my registration number and wheel/suspension derivative but offered me tyres that were not approved. I got the best and most expensive tyre's I could get for my size and profile so it's disappointing to get a problem like that when the old tyres didn't cause any troubles

Ill take it to a real specialist alignment place and see if they can straighten her out a bit for me. Thanks for the analysis of the printout because it's all above my head and hard to understand. Looking on the bright side turning a little bit left is a doddle

[SlimJim16v]

The front is near enough, the rear needs sorting. It depends if the body is out where the subframe/axle mounts, or if it's the subframe/axle that's bent. It may be that there is some adjustment possible by somebody who knows what they're doing.