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Old 09-22-2012, 09:15 PM   #1
aarfocus
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Lost 8MPG with New Tires!

This is really weird. Replaced the stock Kuhmo's (16") on my 2009 with 17" BF Goodrich's. Decided not to replace the pressures sensors and put up with the light. Noticed right away that the computer said MPG was down, confirmed with calculations on a number of tanks of fuel, both highway and around town. I was getting 34mpg around town and 38mpg on highway at around 75mph.

Warning light/message usually came on at start, message went off by pushing "RESET" botton. Once in a while the warnings didn't come on!?

Today I put the origional tires and wheels back on and MPG went right back to 38mpg on a 250 mile trip!! The old and new tire circumferences are very close (within .250") if I recall correctly. Can the lack of TPS and the warning be causing a the computer to mess up the engine, causing the MPG loss?

ANy help would be appreciated!!!

Thanks, Ned


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Old 09-22-2012, 10:00 PM   #2
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it shouldn't. It may just be the design of the tires and wheels.
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Old 09-22-2012, 10:07 PM   #3
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not that it'd affect mpg's but if you have valve stem sensors just put those in your new wheels dude. you shouldn't have to re-balance the new wheels/tires if they just break the outside bead and push the bead down some (w/ a rim clamp). its only held in by a torx head screw... sorry just dont think its worth having the TPMS light on the dash on all the time when it can be turned off easily.
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Old 09-22-2012, 10:17 PM   #4
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don't forget the sensor does weigh a few ounces
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Old 09-22-2012, 11:22 PM   #5
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Quote:
Originally Posted by mikebontoft View Post
it shouldn't. It may just be the design of the tires and wheels.
I can't believe wheels and tires can change it that much!! I have done similar things many times before with no noticiable change. This is just too much!!
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Old 09-22-2012, 11:26 PM   #6
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Quote:
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not that it'd affect mpg's but if you have valve stem sensors just put those in your new wheels dude. you shouldn't have to re-balance the new wheels/tires if they just break the outside bead and push the bead down some (w/ a rim clamp). its only held in by a torx head screw... sorry just dont think its worth having the TPMS light on the dash on all the time when it can be turned off easily.
I believe I have the banded type. Is there a way to tell without breaking the bead? I would think you could take out the valve core and see if the hole goes thru or not.
Does anyone know if the valve stem sensors will work if the car came with the banded type sensors?

I really like these wheels, but the mpg loss is just crazy!!!

sorry just dont think its worth having the TPMS light on the dash on all the time when it can be turned off easily. I would agree but what if it can't be turned off "easily" and tire rack wants $100's of dollars for the sensors-I've driven for nearly 50 years without BS sensors!! lol I'm really only concerned with the MPG, I figure that is a 25% decrease!!!
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Old 09-22-2012, 11:49 PM   #7
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Quote:
Originally Posted by aarfocus View Post
I believe I have the banded type. Is there a way to tell without breaking the bead? I would think you could take out the valve core and see if the hole goes thru or not.
Does anyone know if the valve stem sensors will work if the car came with the banded type sensors?

I really like these wheels, but the mpg loss is just crazy!!!

sorry just dont think its worth having the TPMS light on the dash on all the time when it can be turned off easily. I would agree but what if it can't be turned off "easily" and tire rack wants $100's of dollars for the sensors-I've driven for nearly 50 years without BS sensors!! lol I'm really only concerned with the MPG, I figure that is a 25% decrease!!!
yes. the appearance of the valve stem differs on valve stem types and band types. this is a TPMS style valve stem. you can pretty much tell by how the valve stem cap looks.



as for the valve stems that band style TPMS that Ford use to use, they were just regular valve stems. the same valve stems a car w/o TPMS would have.
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Old 09-23-2012, 10:51 AM   #8
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Quote:
Originally Posted by Red Jay 918 View Post
yes. the appearance of the valve stem differs on valve stem types and band types. this is a TPMS style valve stem. you can pretty much tell by how the valve stem cap looks.



as for the valve stems that band style TPMS that Ford use to use, they were just regular valve stems. the same valve stems a car w/o TPMS would have.
Thanks for the reply. Mine are the standard valve stems. I'm gonna do some experimentation and see what I can learn about this MPG deal. It seems unbelievable that the new wheels and tires car change the mileage that much!
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Old 09-23-2012, 02:27 PM   #9
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If the diameter is really close, I don't think the difference in rolling resistance would cause such a drastic change in mileage.

Is it possible your driving style might have been more spirited with the new 17" tires and wheels, then when you switched back to the old ones for the road trip, back to conservative driving style?
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Old 09-23-2012, 04:58 PM   #10
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There could be a considerable weight difference between the the 17" wheels and tires vs your previous tire and wheel set. This increases rotating mass. You also didn't say what kind of tires you went with or the tire size. A wider stickier tire (especially a summer one) will negatively impact mileage as well. A larger tire will also throw off the odometer and any resulting computer calculations.
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