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Does treadware differences affect mpg?

I didn’t know @shanonia was the tire guy. I thought it was @CapriRacer.

I was hoping someone would clarify that!

Tire rolling resistance gradually drops by about 20% during the life of a tire as the tread wears from its original molded depth to worn out. This can be attributed to the reduction in tread mass and rubber squirm, as well as subtle hardening of the tread compound during years of service and exposure to the elements.

While this gradual reduction in tire rolling resistance and minor increase in fuel economy may be too subtle to register during the tire’s life on a tank-by-tank basis, the virtually instantaneous switch from worn tires to new tires (even if they are the same brand, type and size) will typically result in an increase in rolling resistance of about 20%. Since the automotive industry estimates a 10% increase in tire rolling resistance will result in a 1% to 2% decrease in vehicle fuel economy, drivers should expect to experience a potential 2% to 4% decrease in mpg

You have a rear wheel drive car, you may not be using much more fuel. Your new rear tires are larger in diameter than the worn out ones they replaced. You are now recording less miles on the same trip than you were with the worn tires. If it was windier than the previous trip, that can affect mileage also.

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For crying out loud George ! That is completely wrong , where is the world have you been.

The recommendation throughout the industry is to put the better tires on the rear. Many shops, if you buy two tires, will not put the new tires on the front. Their company policies forbid it.

The theory is thus: FWD cars, which comprise most of what’s on the road today, have typically 60/40 weight distributions. 60% of the weight is on the front, 40% on the rear. In short, the front has 50% MORE weight than the rear. And when stopping, weight transfers to the front. making the distribution more front-oriented.

Weight = traction. Ergo, the front has significantly more traction than the rear with all else equal. Putting the new tires, with the better traction, on the front only exacerbates the traction difference. On slippery roads, this can allow the rear to lose traction first and spin the car out.

Years ago I saw a video put out by Michelin on this issue on a wet test track. The video showed a significant advantage to having the better tires on the rear.

Caveat: they did not test in snow.

Lots of luggage and gifts, so probably the extra weight had a lot to do with this.

Thanks for pointing out that error. I deleted that post above.

Why is this tread still active…I gave the OP an expert opinion by and thats exactly what he wanted to know.

Seriously? No thread stops just because a good answer appears.

Especially when someone brings up the issue of putting the good tires on the rear instead of the front. As some may recall, this was discussed at great length and there simply is not consensus. I gave up the argument though and just buy four tires instead of two. I don’t know who is right and neither do they. I’ve done both ways with not much noticeable difference. On a FWD if the rear begins to slide, the front tires pull the car out of the slide.

But I think your answer was incomplete. It wasn’t clear if Mickey was asking about worn tires vs new or the differences in the wear rating. As you can see from his followup, he was confused about the affect wear rating difference have on a car.

Besides, it is pretty common for the folks here (and elsewhere) to chime in with their opinions - fact based or not.


Tire Rack isn’t 100% the source of all information about tires. Like so many websites, they have some errors of fact and errors of judgement printed there. They are a good resource and generally worth the link, but every so often they make a mistake.

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There was no need to. While most of us have had the discussion before, those who have not can benefit by seeing all sides of the issue.

So how do I deactivate this topic? Website is not intuitively obvious, and I am a retired programmer.

Mickey , there is no need to deactivate the thread . Just don’t post to it and it will move down the list . You can tag it as ’ SOLVED’ if you wish.

Actually someone will revive it 10 years from now and ask if the tires really made a difference.

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I just discovered something.

If you are on the page where the threads are listed, in the upper right hand corner is a circle that if you click on it, allows you to choose how the website will notify you of a new post. It seems to be done by category - that is, if you select to “All Categories”, it disappears, but if you only look at - say - “General Discussion” which is where this thread is, you can deactivate the notification.

In the case of Mickey, our OP, if he does that, he can choose to never get notifications of posts (or whatever option he chooses). The thread goes on, but you just don’t know about it. (or I think that’s how it works.)

Yep, once you say something, it is here for eternity. I still get a response once in a while to a problem with my Riv about ten years ago. Every decade or so either the software is changed or blows up though and everyone starts over again, so there is some hope.

The thing to remember though, is like funerals, it’s not necessarily about you, but there to help others that may have the same issue.

Re: Best set of tires on the front or the rear?

If you just put-put about town, rarely over 50 mph, in a fwd car, do you tire experts still agree the best place to put the two best tires is on the rear? In snowy Colorado where traction in the winter was at a premium, whenever I started to skid it was always – every single time — b/c the front tires lost traction, not b/c the rear tires. I just about bought the farm one time on a road that traversed a steep cliff face b/c the front tires on my truck lost traction on black ice. I was only going maybe 15 mph, front tires lost traction on a turn. Fortunately I rebounded off the side of the hill and got going straight again.

If A person drove very aggressively, accelerated sharply out of corners, etc, I could see the rear wheel argument. But for put-putting about town in a fwd car I think there’s a pretty valid argument to place the best tires on the front, not the rear. What do you folks think?

I agree. I used to put snow tires on the front wheels (only) on my '76 Fiat 128 and was amazed at how it would putt-putt around in snow. At those speeds, in a curve, it also would lose front traction first.