prtyatmoontower

I just switched my winter tires ( Dunlop Winter Sport M3 size: 205/60/16 ) for my brand new summer tires ( Avon Tech M500 size: 225/55/16 ) and I lost about 50 miles a tank!!! I know they're bigger tires and I haven't adjusted the pressure yet since they were installed but 50 miles to a tank?!! That's insane!! I haven't been driving any differently and up untill this the MPG was going up every week 'cause I've been using Prestone gas treatment. I don't know how much of a factor pressure is. My winter's were at 40 psi. And these are propably at 32 - 34 psi. I was going to keep them at 35 - 36 psi but will that make any difference? Over the last couple months with using the gas treatment, new iridium plugs and a K&N filter my tank went from 320 miles 'till the gas light came on to 390 miles. That's an extra 70 miles per tank and now it immediatly drops back down to 340 miles. Any ideas??

silver2003tl

iTrader: (1)

The tires just increased by 20mm, and the pressure dropped also raising resistance (and conversley increasing traction). Your contact patch is I'd guess 10% larger so that increases your rolling resistance. Not sure this is the correct math, but a ball park figure here:

10% larger contact pach
10% better traction
10% increase of rolling resistance
10% loss of fuel.

10% of 390 is 39, that's just about 50miles 2 the tank. At least you can take those corners a little harder now.

SFOX

A wider tire generally has more friction. More friction give you better handling at the cost of gas milage.

By the wy. how do you like the Avon M500. I am thinking put it on my TL-S.

fsttyms1

just from 1 tank you noticed this?? id say give it awhile and then see. also adjust your airpressure higher than the recomended 32

im running Goodyear Eagle F1 GS-D3 225/55/16, they are alot stickier than your tires and im no different in mileage over my Winter Sport M3's

prtyatmoontower

fsttyms1 what pressure were you running your winters at and what pressure do you have your summer's at? My winter's were at 40 psi and these are at 32 psi. I want to pump them up to 35 psi but I don't think that will make up 50 miles.

prtyatmoontower

SFOX they're great tires and I can definately feel the added traction. My only complaints so far is the gas mileage obviously and they tug at the steering harder over bumps. Not really sure if that's the tires or an alignment thing though.

fsttyms1

winters i ran at 35. summer i run at 42-44. you would be surprised waht a few psi will do.

and when you got 50 miles less to a tank was that just 1 tank or many?

LegoGT

I put a new pair of the Avon M550 "tyres" on my car about 2 weeks ago from tirerack. I love the extra grip I get through the turns and can appreciate a quieter ride -- my previous tires were Pirelli SuperSports and noisy as hell (both 215/50/17).

I also noticed my mileage went from around 360-370 until the fuel light came on down to about 320. I've added about 6psi (tires were about 30 cool before) and I'll see if that helps out any. I can already notice that there's less drift in my drive line (probably underinflated before). I'll be driving about 1000 miles road trip this weekend so I should know if it makes any difference to my gas mileage.

fsttyms1

woooo those were underinflated. even the factory recomended # is borderline underinflated. the car will respond much better to a higher psi and better mileage. 35 is as low as i go and thats only with the snow tires. even the factory tires i ran at 40F 38R. i got over 50k out of them at that psi and they still have 4-5/32nds tread leaft (havent used them in 4 years though )

prtyatmoontower

Well, I went out to check the pressure yesterday and they inflated my new tires to 40 psi. The same pressure as my winters. I took them down to 36 psi. And to answer your question fsttyms, it was on the very next tank after I switched tires so it was the first full tank on these tires. By the way, you run your pressures opposite of mine ( lower in the winter - higher in the summer ) just curious why is that.?

LegoGT

So, after 3 full tanks this weekend at 36 psi (cool) I ran 27, 29, and 30 mpg. Drove over 1000 miles with 95% on the highway. Used CC most of the time set between 75 and 85 mph. So the gas mileage seems to be about right now.

I do think I'll try adding a few more psi as suggested by fsttyms and see if that can get rid of the slight steering drift at high speeds.

your_mom

Lower PSI = more traction in mud and snow.

ifrisbee

it might not be the tires. I recently replaced the OEMs with new tires BF Goodrich g-Force T/A KDWS and experienced the same 50-60 mile per tank drop. This was right about the tim e they switched to 10% Ethonal gas in Maryland. Research has indicated that alot of people are experiencing 10-20% drop in gas mileage with the Ethonal mix. I'm begging to suspect that might be the culprit. Then again I'm getting similar gas miles as when the OEMs were new. go figure.

TBone2004

What is the recommended pressure for a set of 245/45/17's? I too am experiencing less gas mileage since changing tires on my 2004 TL. What should I have them at?


Thanks!

fsttyms1

gas is a big part. alot of members start to notice teh same thing in the winter when they start to add it for the colder weather.

Recomended is on the door of the car. After that its personal prefrence. Find out the max psi (on the sidewall of the tire) and dont go over that. Start playing with it. many like the psi different. It really comes down to personal prefrence. The higher it goes the less rolling resistance and better mileage, BUT you start to run into a stiffer ride, possible faster tire wear and more road noise. Adjust it to something you feel comfortable with. I like the 38-42 range myself

paul_huryk

Going with a wider tire will lowe your mielage some due to the greater friction of the larger contact patch. A stickier tire compund will also lower mileage due to the "velcro" effect - but I'm talking really stick tires - like ones with a tread rating uner 150. The third and most important thing for mileage is the tire pressure - you might lose about 0.5% gas mileage for each psi you keep a tire. So if you were running 40 and go down to 34, you lose about 3% of your mileage.

derrick

One thing people forget to measure (or compare) ... how about the actual WEIGHT of the tire. Sometimes the replacement tires are heavier than the tire you had on before. Definitely contact patch and tire pressure are considerations but I think so as long as everyone has variables such as the last 2 mentioned somewhat the same ... added weight of the tire is a factor that signficantly decreases in fuel economy in stop and go traffic.

paul_huryk

That is 100% true - tire weight is important too. But the good news is that the difference in weight of tires (in the same size) is typically no more than a few lbs - wheels are the ones with the large variations in weight. Even brake rotors can weigh differently - and they rotate with the wheels and tires all the same.