So, a while ago I asked Bark and community what to replace my broken Audi wagon with. I ended up purchasing a 2010 Lincoln MKT Ecoboost. So far, it has meet all my needs and — more importantly — my expectations, with one minor but irritating issue. At speeds around 70 mph and up, I notice a constant “twitch” in the steering on some highway surfaces — a sensation of vibrating left and right just enough to be noticeable, but not enough to change the actual trajectory of the car.
Thinking that it was an alignment issue, I ran to discount tire (free rotations and balance because of my previous purchase history), where it was pointed out to me that the aftermarket wheels the car came with (future note: check the width and not just the diameter) did not align with what their computer system said I should have.
A stock tire on an Ecoboost MKT is 255/45-20 Goodyear Eagle RS-A. The tires on my car are 235/60-18 Michelin Premier LTX. The gentleman explained to me that my tires were basically an inch narrower than stock, and while the ratio for the tire and the wheel was correct, because of the prodigious power output of a front-wheel-drive Ecoboosted car, my front tire might be “slipping” on some surfaces at higher speeds due to smaller tire contact patches. It’s not enough to get the AWD system to kick in but enough to get the vibration sensation when driving at higher speeds.
He said the best solution would be to get wider wheels and tires. Now, I consider myself somewhat knowledgeable on the benefits of higher-profile tires in terms of ride, snow traction, and towing performance, I have no experience with tire width. The cost of a wheels and tires swap-out for a stock setup is about $2,000. Thus, I would like to know what the community and yourself thinks before I start looking for ways to part with a sum of money that, in theory, could get me into old but reliable Civic or Camry.
“The gentleman explained…because of the prodigious output of a front wheel drive Ecoboosted car, at higher speeds because of the smaller tire contact patches, my front tire might be “slipping” on some surfaces.”
Never. Double the power and it’ll still hook up at highway speeds at throttle inputs soft enough to not activate the power take-off unit. Your vibration is related to aftermarket wheel quality, not throttle input.
The circumference difference is only 0.3 percent (91.2 inches vs. 91.4 inches), so the tire choice is valid. My relationship with aftermarket wheels is still love/hate, since my Fox-body Cougar is daily driven: the reproduction Cobra wheels vibrate at around 40-50 mph on certain paved surfaces, even after switching to factory lug nuts.
I’m sick of it, and I feel your pain. We both need higher-quality aftermarket, or factory, Ford wheels. I should grab some 15×7-inch factory turbine wheels and you should consider a set of “take-off” hoops from an MKT, MKX, or perhaps that newfangled Town Car thingy.
Send your queries to sajeev@thetruthaboutcars.