New tyres and clean alignment but pulling to left

[Considered]

Hi,

Recently purchased a used Macan GTS from an 'official' Porsche dealership. Before purchasing, they put four new Michelin tyres on it an alignment, which shows everything within tolerance (green on a hunter machine).



However, the car seems to have a pull to the left. On roads that slope left, it seems to drift left (not massively unexpected). On roads that slope right, it seems to drift right. On roads that are (or at least appear to be) flat, it tends to drift left. In case it's relevant, the front tyres are 265/45 R20s with 295/40 R20s at the rear.

Presumably on a perfectly flat, straight road, I should be able to let go of the steering wheel for a few seconds, with the car continuing in a straight line?

The OPC has offered to pay for an investigation but I do not want to 'waste' the goodwill if it's all in my head and/or this is how these cars are supposed to drive... The other half seems to think I'm making it up!

Any ideas?

Edited by Considered on Friday 5th September 13:49

[bobtail4x4]

find a road without a camber,

most cars will run down the slope to a degree,

[Robertb]

I seem to recall Chris at Center Gravity road-testing my car and saying a gentle drift in the direction of road camber was how it should be.

[wyson]

Hunter machine is only as good as the operator, it isn’t fool proof. I had an all green printout, my car was worse than before the alignment, and needed a good 10 degrees of lock in the opposite direction. They failed twice to correct it, Hunter print out all green again. I had to take it elsewhere to return it back to normal.

Try a big car park, early in the morning or after hours. Drive in different directions. If it always pulls to the left, you know something is up.

[DodgyGeezer]

TBH I felt similar on both Mrs DG's Macan and my Challenger... both were different.

- Challenger was uneven brake-pad wear. TBF this was accompanied by some judder at c.50mph, new pads and discs problem resolved
- Macan was... well weirdly I don't know, it either just went away or I got used to it

[Sheepshanks]

I had a Merc that, rather than drifting, would roll on more lock depending on which way the camber went. Supposedly Merc designed it like that so you wouldn't run into oncoming traffic if you fell asleep.

On the Merc it could be corrected with offset camber bolts but I never had that done as it wore the tyres evenly and I, as I was doing at lot of miles in it, I didn't want to less it up. However it was a bit of pain to have to hold it ever so slightly to the right on motorway journeys.

Wife has had various VW Group cars and you could take your hands off for a while and they'd run straight. Then her Tiguan had new rear shocks and the dealer was adamant that wouldn't affect things but it was never the same after that, and the more they messed with it the worse it got until we got rid of it.


Are the tyres on the Macan directional? If not, it might be worth swapping the fronts over - sometimes tyres can have runout, they're supposed to be marked when new with coloured bands,

[g3org3y]

DodgyGeezer said:

TBH I felt similar on both Mrs DG's Macan and my Challenger... both were different.

- Challenger was uneven brake-pad wear. TBF this was accompanied by some judder at c.50mph, new pads and discs problem resolved
- Macan was... well weirdly I don't know, it either just went away or I got used to it

Uneven brake pad wear caused the car to pull to one side on driving? How unusual. How does uneven wear cause that?

[Panamax]

Presumably the uneven wear was the effect, not the cause, the cause having been a sticking caliper. May well have pulled to one side when braking.

[E-bmw]

Panamax said:

Presumably the uneven wear was the effect, not the cause, the cause having been a sticking caliper. May well have pulled to one side when braking.

Much more likely.

[E-bmw]

Considered said:

the car seems to have a pull to the left. On roads that slope left, it seems to drift left (not massively unexpected). On roads that slope right, it seems to drift right.

What you describe there is obviously exactly what should happen.

[g3org3y]

Panamax said:

Presumably the uneven wear was the effect, not the cause, the cause having been a sticking caliper. May well have pulled to one side when braking.

Right, my thoughts also. It seemed implied from the post that it was the uneven brake pad wear that caused the steering issues which I couldn't work out logistically why/how that would happen.