Several people on here had said they felt vibration with the weels hard over under acceleration. I (mis)diagnosed it as a problem with the power steering pump.

Well, I just felt it (actually just noticed it matched the descriptions people posted). At the risk of sounding like an Audi dealer, it is normal.

It happens to me when at a corner (like a light), with the wheels turned far over, and you apply gas from stop. You get a short series of pulls left and right on the wheel. For me, it's usually 2-3 in each direction (for 4-6 pulls total).

Well, it's nothing, don't worry about it. It's just an interaction between the wheels being leaned over (due to the steering geometry) on edge, having fat tires, and a lot of torque. The feeling comes from "microslips", as someone called them.

Tires are made up of bands of tread blocks. A tread block is one of the protrusions of rubber that the grooves separate. A band of them is a group across the tire (not around the circumference, perpendicular).

Basically, you apply power to the tires, and the torque deforms the tread blocks on one of the tires (if you are turning, it's the inside one that goes first), as they bend, it allows that wheel to go a little faster, so the tire can slip a little bit, but that causes fresh tread block groups to come into contact with the road, ones which aren't deformed yet. (And the deformed ones snap back as they come out of contact with the road) So the tire catches grip. But the driveline had gained a little speed and momentum when that tire sped up for a while, now when it slows down, there does that momentum go? Well, it goes to the other tire, which overloads it, so it slips, catches, and sends the power back the other way. This happens a couple times until the car is up to speed where the tread blocks aren't at the bottom of the tire long enough to cause trouble.

Basically, your car "walks" from left front tire to right front tire for a very short time. Wider tires make this worse, as they are flatter and wider, so the tilt raises the inside part of the tire up more than on a narrow tire.

Race-type performance tires would reduce this a little since the tread is less deep and so they deform less. But it can also happen due to some gravel on the road, and nothing can stop that I don't think.

So anyway if you feel these short pulls turning sharp turns from stop, don't worry about it, it really is normal for FWD or AWD cars.

 

I have been driving old Land Cruisers so long now and actually off-roading them ( ;-) ) during my fly fishing an bird hunting trips that I was very familiar with this drivetrain trait. You ought to feel the binding in a solid axle 4wd system in low range! But your explanation for those who have never experienced this was very well put!

 

such as my front wheel drive Accord? I've switched to wide tires, and still none of this.