Archives

I was doing so well and was looking to upgrade my car a little. I purchased some new light weight rims and new tires, but became very sad when I watched the scangauge. I've seen about a 5 to 8 mpg drop and it looks like it will get worse. I'd suggest staying away from the Bridgestone Fuzions for FE. They grip the road like velcro, but as we know that hurts the mpg real bad. I have them at max sidewall of 44psi and I'll probably get them up to 50psi soon. Hopefully that will help a bit.

Didn't know where else to cry about it but here, lol. Thanks for hearing me.

o wow, got you some sticky tires there huh.. they should get better with a little bit of wear ;)

Hi Coda:

___I am very sorry to hear about the loss :( You will get some back in about 2 to 3,000 miles but not 5 - 8 mpg.

___Good Luck

___Wayne

You should probably do a cross analysis of the tires/rims you had before and the ones you have now. If there is a difference in over all circumference then you should compensate for the difference. I would bring them up to max sidewall asap instead of waiting (no gain in lower tire pressure).

These rims are 17" where my old ones where 16". Could that possibly cause scangauge to misread my actual mpg and rate it lower than normal? My old rims weighed 18lbs where these ones now weigh 14.2lbs. I will be blocking the upper and lower grille to improve aero once winter comes around so hopefully that will boost it. And also, the old tires were 205 for the width and these new ones are 215, bleh! I could have gotten the 205's but they were 30 bucks more a tire. :(

xcel, I hope you're right and wearing them down a bit helps. I'll keep trying though, I haven't given up yet.

coda if you replace the tires with the exact same width/aspect ratio say 215/60/16 with a 215/60/17 then you have a increase in circumfernce and therefore less reves per mile and getting false readings, a lighter tire may also have softer side walls

the circumference of your tires = the diameter of your wheel plus the aspect ratio converted times Pi. Make sure you have the correct units of mm for the wheel diameter (17 x 25.4).

The value of the aspect ratio in mm (from rim to outer edge of wheel) is equal to the aspect ratio divided by X, where X is the number that is used to divide the tire diameter to get 100.

"the old tires were 205 for the width and these new ones are 215, bleh! I could have gotten the 205's but they were 30 bucks more a tire. "

I have a suggestion........take your car onto a highway that has mileage markers. Then drive for 10 or more miles and see if your odometer agrees with the markers. I bet it does not agree.

You have increased the size of your tire without redoing the speedometer and odometer gearing.

Your car will now read slower speed and less miles than are actually driven by what fraction the (new circumference/old circumference) -1 is.

These rims are 17" where my old ones where 16". Could that possibly cause scangauge to misread my actual mpg and rate it lower than normal? My old rims weighed 18lbs where these ones now weigh 14.2lbs. I will be blocking the upper and lower grille to improve aero once winter comes around so hopefully that will boost it. And also, the old tires were 205 for the width and these new ones are 215, bleh! I could have gotten the 205's but they were 30 bucks more a tire. :(

xcel, I hope you're right and wearing them down a bit helps. I'll keep trying though, I haven't given up yet.


Sir, It will read less no matter how you look at it. You have to include the %age difference in tire size at the end of your tank/miles driven.

If he followed proper "Plus One" sizing conventions, he should end up with the same revs per mile as the old tires, or at least within 1%.

He seems to have fallen for the old "lighter is better" scheme when it comes to wheels. Even though the new wheels are lighter in total weight, moment of inertia is what matters. A larger diameter wheel locates the weight of the tire itself further from the center of the hub, increasing it's "effective" weight. In addition, the new tires are certainly more than 4 lbs heavier than the old ones, probably more like 8-10 lbs heavier.

And an aggressive sports tire will normally have a bit more drag.

No surprise here that you lost a few mpg.

Gah, I can't take it anymore.

Here's all we know from what you've said here.

You went from
205/?? R16 ? tires
to
215/?? R17 Fuzion ? tires.


You went from
18 pound 16x? ? wheels
to
14 pound 17x? wheels.


WAY too many unknowns.


Adding in some SWAGs:

From
21 pound 205/55 R16 Bridgestone Turanza EL400-02 tires
to
23 pound 215/45 R17 Fuzion HRi tires.


From
18 pound 16x6.5 Unknown Aftermarket Alloy wheels
to
14 pound 17x7 Motegi,Kosei,Enkei,Other Aftermarket Alloy wheels.

Given the swags above, less than a 1% difference in revolutions/mile, so don't even worry about that noise.


It would be helpful to confirm the SWAGs or fill in the remaining blanks.

A little bit more research prior to your purchase could have avoided the temptation to increase the PSI to "compensate" for your choices.

-mr. bill

Bill is absolutely right - too many unknowns.

FWIW:

1) New tires have higher RR values than worn out tires - all other things being equal.

2) Wider tires have higher RR values than narrower tires - all other things being equal.

3) OE tires have LOWER RR values than replacement market tires (as a general rule)

From what little information has been posted, it sounds like the OP took 4 hits (if I count the rim!)

cOda, the good news is that you have good tread between you and the road. As xcel points out, as those new shoes wear in, your MPG should increase, not get worse.

Think of your radiator block as something to minimize the normal decrease in MPGs in the Winter. Make sure you have a ScanGauge or something to accurately report the coolant temperatures while your radiator block is in place. If you can make it in removeable segments, you can play around with it a little more (more flexibility with temperature changes). If you go whole-hog, you could set it up with a variable opening that you could control from the cockpit.

Back to your tires, what are the Traction and Temperature capabilities of your new shoes? How often do you check tire pressure and inspect your tires?

I will fill all those unknowns in when I get home. Sorry for the lack of info, but I will give you what I know off the top of my head.

I check my tire pressure twice a month. They are set to the max psi of 44 right now, but I will raise them to 50psi soon.The original wheel/tires were stock Goodyear eagles on steelies(the stock 8th gen civic tires on 16x7 rims I believe). I now have Konig daylites that are 17x7.

Thanks for helping me with this.

FWIW, Wayne just today explained to me one reason why new tires, regardless of dimensions, might show worse FE at first. See:

http://www.cleanmpg.com/forums/showthread.php?t=14643&page=3

Your original tires were 205/55/16 and you went to 215/45/17's ?
You did put 45's on those wheels ?

If your speedometer read 65 mph at 65 mph with the old tires and wheels.
At 65 mph with the new tire wheel combination your speedometer
should read 64.32 mph. That is only a 1% change in your mileage recorded by your speedometer. If you drive 300 miles you have actually traveled 303 miles.