Go Back   EcoModder Forum > EcoModding > Off-Topic Tech
Register Now
 Register Now
 

Reply  Post New Thread
 
Submit Tools LinkBack Thread Tools
Old 09-05-2012, 06:23 PM   #31 (permalink)
home of the odd vehicles
 
rmay635703's Avatar
 
Join Date: Jun 2008
Location: Somewhere in WI
Posts: 3,874

Silver - '10 Chevy Cobalt XFE
Thanks: 495
Thanked 863 Times in 650 Posts
Quote:
Originally Posted by oil pan 4 View Post
If you can pull those from the junk yard new, all day for $10 or $20 each, its unbeatable.
Half were $5 the other half were $10 and I get a few cents for the rims.

Best part is they are the correct size for the car.

  Reply With Quote
Alt Today
Popular topics

Other popular topics in this forum...

   
Old 08-02-2014, 03:55 PM   #32 (permalink)
EcoModding Lurker
 
CargoBoatTails's Avatar
 
Join Date: Aug 2014
Location: New England
Posts: 71
Thanks: 39
Thanked 7 Times in 7 Posts
From my experience yes, less weight and size means less rolling resistance. A simple formula is the max load of the tire should be equal to or greater than half of the GAWR front or rear on the Vehicle Certification Label, usually the rear is less on a fwd car. From there the smallest wheel with the smallest tire is best. You can easily find tire specs on tirerack.com This should be done before lowering the car as it may make it unnecessary to do. There may be a limit to how small of a wheel you can use to fit over brake calipers.
  Reply With Quote
Old 08-02-2014, 04:00 PM   #33 (permalink)
Master EcoModder
 
mcrews's Avatar
 
Join Date: Oct 2009
Location: Texas
Posts: 3,523

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

blackie - '14 nissan altima sv
Thanks: 2,203
Thanked 663 Times in 478 Posts
cargo,
can you show us your tests that verify this.
it runs contrary to my tests and those of others.

smaller DIAMETER of tire results in HIGHER RPM at cruise speed. Higher rpms result in lower gas mileage.
__________________
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 08-02-2014, 05:21 PM   #34 (permalink)
EcoModding Lurker
 
CargoBoatTails's Avatar
 
Join Date: Aug 2014
Location: New England
Posts: 71
Thanks: 39
Thanked 7 Times in 7 Posts
Lightbulb

Quote:
Originally Posted by mcrews View Post
cargo,
can you show us your tests that verify this.
it runs contrary to my tests and those of others.

smaller DIAMETER of tire results in HIGHER RPM at cruise speed. Higher rpms result in lower gas mileage.
The test that I used was the simple fill up to first stop and then use a full tank of gas from a 0 trip odometer and then fill the same way and then divide the trip odometer by the gallons on the pump. This was on a Nissan Versa 4D 1.8SL CVT(which helped) going from a 225/45/17 (summer tires) to a 195/55/15 (snow tires) and consistently showed a difference of 3mpg exactly, 30 to 27 respectively. Even with a difference of 1.6" on a non CVT car you're only talking a difference of a couple hundred rpm which is negligible.
  Reply With Quote
Old 08-02-2014, 05:22 PM   #35 (permalink)
EcoModding Lurker
 
CargoBoatTails's Avatar
 
Join Date: Aug 2014
Location: New England
Posts: 71
Thanks: 39
Thanked 7 Times in 7 Posts
Here's a calculator you may want to make a sticky

Tire Size, RPM, Speed, and Differential Ratio Calculator
  Reply With Quote
Old 08-02-2014, 06:38 PM   #36 (permalink)
herp derp Apprentice
 
Join Date: Oct 2008
Location: Lawrence, KS
Posts: 1,049

Saturn-sold - '99 saturn sc1
Team Saturn
90 day: 28.28 mpg (US)

Yukon - '03 GMC Yukon Denali
90 day: 13.74 mpg (US)
Thanks: 43
Thanked 331 Times in 233 Posts
Quote:
Originally Posted by CargoBoatTails View Post
The test that I used was the simple fill up to first stop and then use a full tank of gas from a 0 trip odometer and then fill the same way and then divide the trip odometer by the gallons on the pump. This was on a Nissan Versa 4D 1.8SL CVT(which helped) going from a 225/45/17 (summer tires) to a 195/55/15 (snow tires) and consistently showed a difference of 3mpg exactly, 30 to 27 respectively. Even with a difference of 1.6" on a non CVT car you're only talking a difference of a couple hundred rpm which is negligible.
So was the difference in tire size factored in (6%)? The other 4% could easily be differences in rolling resistance differences of 2 very different tires
  Reply With Quote
Old 08-02-2014, 06:43 PM   #37 (permalink)
Master EcoModder
 
mcrews's Avatar
 
Join Date: Oct 2009
Location: Texas
Posts: 3,523

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

blackie - '14 nissan altima sv
Thanks: 2,203
Thanked 663 Times in 478 Posts
Quote:
Originally Posted by CargoBoatTails View Post
The test that I used was the simple fill up to first stop and then use a full tank of gas from a 0 trip odometer and then fill the same way and then divide the trip odometer by the gallons on the pump. This was on a Nissan Versa 4D 1.8SL CVT(which helped) going from a 225/45/17 (summer tires) to a 195/55/15 (snow tires) and consistently showed a difference of 3mpg exactly, 30 to 27 respectively. Even with a difference of 1.6" on a non CVT car you're only talking a difference of a couple hundred rpm which is negligible.
It is REALLY important when doing tests (A-B-A ideally) that the variables are consistent.
1. The thread is about TIRE size. It is important to understand that it means ONLY tire size. 15 to 15 etc.
2. Tests comparing different size(14, 15, 16 etc) tires means you have different rims. so weight of each rim HAS to be taken into consideration.
3. Since the rims are different sizes, then there is the consideration for the movement of MASS in and out.
4. Finally, summer tire to winter tire has some weight difference, especially on different size tires and compound difference.
5. finally, you don't say if you are factoring for the odometer being off. YOu seem pretty clear that you don't. THe best way is with GPS mileage, it's always right regardless of tire size.

Cant really say that you 'tested' the results.

Again, MULTIPLE members have posted true tested results. A smaller TIRE, doesnot produce better mileage.
__________________
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 08-02-2014, 06:54 PM   #38 (permalink)
EcoModding Lurker
 
CargoBoatTails's Avatar
 
Join Date: Aug 2014
Location: New England
Posts: 71
Thanks: 39
Thanked 7 Times in 7 Posts
I wouldn't bother going with a smaller tire unless I was going to a smaller rim. Again the speedo error would be negligible and not in favor of the smaller tire anyway recording more miles, so yeah I was probably getting better than 3mpg improvement.

Here's another calculator for you:

http://tire-size-conversion.com/spee...r-calibration/
  Reply With Quote
Old 08-02-2014, 07:03 PM   #39 (permalink)
herp derp Apprentice
 
Join Date: Oct 2008
Location: Lawrence, KS
Posts: 1,049

Saturn-sold - '99 saturn sc1
Team Saturn
90 day: 28.28 mpg (US)

Yukon - '03 GMC Yukon Denali
90 day: 13.74 mpg (US)
Thanks: 43
Thanked 331 Times in 233 Posts
Yes, the smaller tire would record more miles, about 6.1% more miles.
So if you travel 100 actual miles, and use 2 gallons of fuel, you would figure your mileage as 50mpg. With the smaller tires your odometer would show 106.1miles, even though you had only traveled 100 miles, and if you consumed the same 2 gallons, you would falsely calculate 53.05mpg
  Reply With Quote
The Following User Says Thank You to 2000mc For This Useful Post:
mcrews (08-02-2014)
Old 08-02-2014, 07:04 PM   #40 (permalink)
Master EcoWalker
 
RedDevil's Avatar
 
Join Date: Dec 2012
Location: Nieuwegein, the Netherlands
Posts: 3,998

Red Devil - '11 Honda Insight Elegance
Team Honda
90 day: 47.72 mpg (US)
Thanks: 1,711
Thanked 2,245 Times in 1,454 Posts
A smaller circumference will reduce both speed and distance covered so to compensate you'd need to drive both faster and further, at least according to the speedo/odo.
Using GPS data is indeed the best way to resolve it.

Then your winter tires are softer, have higher side walls and narrower thread, these things will contribute to the FE. Even at the correct speed an distance those may compensate for the higher RPMs and higher rolling resistance from the shorter tire radius.

With so many things to consider it is near impossible to draw conclusions from this test alone.

__________________
2011 Honda Insight + HID, LEDs, tiny PV panel, extra brake pad return springs, neutral wheel alignment, 44/42 PSI (air), PHEV light (inop), tightened wheel nut.
lifetime FE over 0.2 Gmeter or 0.13 Mmile.


For confirmation go to people just like you.
For education go to people unlike yourself.
  Reply With Quote
The Following User Says Thank You to RedDevil For This Useful Post:
mcrews (08-02-2014)
Reply  Post New Thread


Thread Tools




Powered by vBulletin® Version 3.8.11
Copyright ©2000 - 2024, vBulletin Solutions Inc.
Content Relevant URLs by vBSEO 3.5.2
All content copyright EcoModder.com