Go Back   EcoModder Forum > EcoModding > EcoModding Central
Register Now
 Register Now
 

Reply  Post New Thread
 
Submit Tools LinkBack Thread Tools
Old 05-18-2011, 11:24 PM   #1 (permalink)
Pishtaco
 
SentraSE-R's Avatar
 
Join Date: Jun 2009
Location: Bay Area, California
Posts: 1,484

Mean Green Toaster Machine - '06 Scion xB
Team Toyota
90 day: 48.92 mpg (US)
Thanks: 56
Thanked 283 Times in 180 Posts
Tall tire test (taller gearing advantage offset by wider, heavier wheels/tires?)

I did some testing of my new 205/50-17 wheels/tires v. the stock 185/60-15 wheels/tires. There are too many variables for this to be a realistic comparison, but this testing is better than just guessing what happens if you swap to 6% taller tires and wheels that weigh 12 lbs more, each.

Car with stock tires/wheels

Car with new tires/wheels

Internet tire specifications:
======= ..... new ...... old
diameter ......... 25.07"...23.74"
revs per mile.... 829.6 ....876.1
speedo diff...... -5.605%...0%
diameter diff..... 5.31% ....0%

In their favor, the new shoes are taller geared, look better, and have 51 psi sidewall maximums (v. stock 44 psi). Working against them is their extra weight, worse aerodynamics, and wider tread. On balance the newer, taller tires should get me worse mpg, as it's likely the minuses outweigh the pluses.

New weight 47.3 lbs Old weight 35.3 lbs (tire + wheel weight)

distance calibration (tested against GPS after 40 miles, minimum distance)
new 1.099 old 1.033 (odometer shows 10.0 miles, I've traveled 10.99 miles with the new tires, or 10.33 miles with the old tires)

The drive is a 10 mile loop (cruise control, 32 mph) with minimal traffic, and no stop signs. I do have to turn around at each end to go the other direction. It's at sea level with a few hills - the tallest one perhaps 100' high. Temperature was 65-70 degrees, partly cloudy, winds 0-5 mph from the west. The route runs north and south. Roads were dry. Mpg calculated with Ultragauge.
new1..49.2 mpg.....old1..50.1 mpg
new2..50.4 mpg.....old2..50.0 mpg

Essentially identical performance. It's roughly confirmed by my 900 mile trip last weekend with the new tires. I got 53.7 mpg my first tank and 47.7 mpg topping off the tank in preparation for the drive home. The 53.7 is my best highway tank, and 47.7 is about average for me when I had the old tires. The new tires get similar mpg to the old ones.

Considering the 17" tires/wheels weigh 12 lbs apiece more than the stockers, are less aerodynamic, and are 20 mm. wider, I'm pleased that I didn't lose mpg with the trade.

*Edited 5/19/11 to correct incorrect original tire diameter

__________________
Darrell

Boycotting Exxon since 1989, BP since 2010
Have you ever noticed that anybody driving slower than you is an idiot, and anyone going faster than you is a maniac? George Carlin
Mean Green Toaster Machine
49.5 mpg avg over 53,000 miles. 176% of '08 EPA
Best flat drive 94.5 mpg for 10.1 mi
Longest tank 1033 km (642 mi) on 10.56 gal = 60.8 mpg

Last edited by SentraSE-R; 05-20-2011 at 02:11 AM..
  Reply With Quote
The Following User Says Thank You to SentraSE-R For This Useful Post:
kurzer (01-26-2013)
Alt Today
Popular topics

Other popular topics in this forum...

   
Old 05-19-2011, 12:00 AM   #2 (permalink)
Cyborg ECU
 
California98Civic's Avatar
 
Join Date: Mar 2011
Location: Coastal Southern California
Posts: 4,151

Black and Green - '98 Honda Civic DX Coupe
Team Honda
90 day: 61.22 mpg (US)

Black and Red - '00 Nashbar Custom built eBike
90 day: 3671.43 mpg (US)
Thanks: 1,479
Thanked 1,156 Times in 768 Posts
Quote:
Originally Posted by SentraSE-R View Post
Essentially identical performance. It's roughly confirmed by my 900 mile trip last weekend with the new tires. I got 53.7 mpg my first tank and 47.7 mpg topping off the tank in preparation for the drive home. The 53.7 is my best highway tank, and 47.7 is about average for me when I had the old tires. The new tires get similar mpg to the old ones.
Well, the new wheels look cool. And these numbers could mean that your MPG has actually improved, as you noted, the test itself is usefully suggestive but not conclusive. You might learn more as you drive around more. The extra weight will of course matter more in city driving, while the taller gearing won't help as much, no?

At minimum you know your new wheels are not costing anything too significant in mpg. And they look sharp.
__________________


See my car's mod & maintenance thread and my electric bicycle's thread for ongoing projects. I will rebuild Black and Green over decades as parts die, until it becomes a different car of roughly the same shape and color. My minimum fuel economy goal is 55 mpg while averaging posted speed limits. I generally top 60 mpg. See also my Honda manual transmission specs thread.

  Reply With Quote
Old 05-19-2011, 12:26 PM   #3 (permalink)
Pishtaco
 
SentraSE-R's Avatar
 
Join Date: Jun 2009
Location: Bay Area, California
Posts: 1,484

Mean Green Toaster Machine - '06 Scion xB
Team Toyota
90 day: 48.92 mpg (US)
Thanks: 56
Thanked 283 Times in 180 Posts
Aside from the looks, the main reason I wanted to go taller was to get the engine buzzing less at freeway speeds. It used to buzz at 3200 rpm @ 60 mph. Now it's "only" 3000 rpm @ 60 mph.
__________________
Darrell

Boycotting Exxon since 1989, BP since 2010
Have you ever noticed that anybody driving slower than you is an idiot, and anyone going faster than you is a maniac? George Carlin
Mean Green Toaster Machine
49.5 mpg avg over 53,000 miles. 176% of '08 EPA
Best flat drive 94.5 mpg for 10.1 mi
Longest tank 1033 km (642 mi) on 10.56 gal = 60.8 mpg
  Reply With Quote
Old 05-19-2011, 01:35 PM   #4 (permalink)
EcoModding Lurker
 
Join Date: Apr 2009
Location: Oregon
Posts: 65
Thanks: 6
Thanked 9 Times in 8 Posts
Looks really nice and they didn't seem to hurt your impressive mileage. If you don't mind me asking, have you lightened your Scion from the factory curb weight? I noticed you have it listed at 2400 lbs with no mods whereas wikipedia states 3000 which is what I would have expected. Not doubting you at all but just curious.
  Reply With Quote
Old 05-19-2011, 02:48 PM   #5 (permalink)
Pishtaco
 
SentraSE-R's Avatar
 
Join Date: Jun 2009
Location: Bay Area, California
Posts: 1,484

Mean Green Toaster Machine - '06 Scion xB
Team Toyota
90 day: 48.92 mpg (US)
Thanks: 56
Thanked 283 Times in 180 Posts
The second generation (2008-2011) xBs weigh 3000 lbs. First generation (2004-2006) xBs are substantially smaller and lighter at roughly 2400 lbs. I haven't stripped any weight off of mine.
__________________
Darrell

Boycotting Exxon since 1989, BP since 2010
Have you ever noticed that anybody driving slower than you is an idiot, and anyone going faster than you is a maniac? George Carlin
Mean Green Toaster Machine
49.5 mpg avg over 53,000 miles. 176% of '08 EPA
Best flat drive 94.5 mpg for 10.1 mi
Longest tank 1033 km (642 mi) on 10.56 gal = 60.8 mpg
  Reply With Quote
Old 05-19-2011, 03:16 PM   #6 (permalink)
EcoModding Apprentice
 
Join Date: Apr 2011
Location: Houston
Posts: 228
Thanks: 0
Thanked 23 Times in 17 Posts
Same mileage, fewer revs, looks better, probably handles and stops better. All around a good move, I think. Thanks for testing and posting.
  Reply With Quote
Old 05-20-2011, 01:55 AM   #7 (permalink)
Blow stuff up
 
phunky.buddha's Avatar
 
Join Date: Jul 2010
Location: DFW Metro, TX
Posts: 67

S2000 - '03 Honda S2000
Team Honda
90 day: 24.42 mpg (US)
Thanks: 2
Thanked 5 Times in 4 Posts
Very nice! I didn't lose any efficiency going to a taller wheel combo compared to stock (215/50-16 on 16x7 +40 wheels) on my wife's xB either- didn't do an A/B test like you did though.
__________________
Intercrew Auto Salon
  Reply With Quote
Old 05-20-2011, 08:37 AM   #8 (permalink)
Master EcoModder
 
mcrews's Avatar
 
Join Date: Oct 2009
Location: Texas
Posts: 3,521

The Q Sold - '02 Infiniti Q45 Sport
90 day: 23.08 mpg (US)

blackie - '14 nissan altima sv
Thanks: 2,183
Thanked 658 Times in 474 Posts
why do i feel like we already had this discussion......

12x4=48lbs
4 tires =192lb additional moving mass
almost 8%
__________________
MetroMPG: "Get the MPG gauge - it turns driving into a fuel & money saving game."

ECO MODS PERFORMED:
First: ScangaugeII
http://ecomodder.com/forum/showthrea...eii-23306.html

Second: Grille Block
http://ecomodder.com/forum/showthrea...e-10912-2.html

Third: Full underbelly pan
http://ecomodder.com/forum/showthrea...q45-11402.html

Fourth: rear skirts and 30.4mpg on trip!
http://ecomodder.com/forum/showthrea...tml#post247938
  Reply With Quote
Old 05-20-2011, 10:20 AM   #9 (permalink)
EcoModding Apprentice
 
Join Date: Apr 2011
Location: Houston
Posts: 228
Thanks: 0
Thanked 23 Times in 17 Posts
Quote:
Originally Posted by mcrews View Post
why do i feel like we already had this discussion......

12x4=48lbs
4 tires =192lb additional moving mass
almost 8%
Soooo, yeah, just think if the wheels weren't heavier, there could be a noticeable improvement in mpg, maybe. Also, it probably means that this change would not help "city" mileage.
  Reply With Quote
Old 05-20-2011, 06:05 PM   #10 (permalink)
Pishtaco
 
SentraSE-R's Avatar
 
Join Date: Jun 2009
Location: Bay Area, California
Posts: 1,484

Mean Green Toaster Machine - '06 Scion xB
Team Toyota
90 day: 48.92 mpg (US)
Thanks: 56
Thanked 283 Times in 180 Posts
That's a possible option - to put taller tires on the stock wheels. 195/65-15s would be 5% taller than stock while only weighing 37 lbs. I'll keep my eyes and ears open for used tires in that size, for a future test.

I don't follow Mark's math. Unsprung weight affects inertia and handling, but I don't see how it equals an 8% increase in the effective weight of my vehicle, nor how that necessarily affects fuel economy. I pulled 48 mpg with 600 lbs of passengers on a 150 mile drive last Fall. The added momentum on downhills pretty much made up for the extra work getting the weight up to speed.

__________________
Darrell

Boycotting Exxon since 1989, BP since 2010
Have you ever noticed that anybody driving slower than you is an idiot, and anyone going faster than you is a maniac? George Carlin
Mean Green Toaster Machine
49.5 mpg avg over 53,000 miles. 176% of '08 EPA
Best flat drive 94.5 mpg for 10.1 mi
Longest tank 1033 km (642 mi) on 10.56 gal = 60.8 mpg

Last edited by SentraSE-R; 05-20-2011 at 06:47 PM..
  Reply With Quote
Reply  Post New Thread


Thread Tools




Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2017, vBulletin Solutions, Inc.
Content Relevant URLs by vBSEO 3.5.2
All content copyright EcoModder.com