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

Reply  Post New Thread
 
Submit Tools LinkBack Thread Tools
Old 03-16-2018, 06:25 PM   #11 (permalink)
Batman Junior
 
MetroMPG's Avatar
 
Join Date: Nov 2007
Location: 1000 Islands, Ontario, Canada
Posts: 20,490

Blackfly - '98 Geo Metro
Team Metro
Last 3: 70.09 mpg (US)

MPGiata - '90 Mazda Miata
90 day: 51.34 mpg (US)

Winter beater Metro - '00 Chevrolet Metro
90 day: 69.74 mpg (US)
Thanks: 2,467
Thanked 5,302 Times in 2,704 Posts
trivia: BMW i3s with wider tires has lower efficiency

Quote:
Originally Posted by westygo View Post
The BMW electric with the large diameter and narrow tires...
FYI: they released a "sport" version of the car for 2018 with wider tires, and the combined EPA range is down 6% vs. the regular version. (107 vs. 114 miles)

Differences of sport vs. regular i3:
  • tires: front 175/55/R20 / rear 195/50 R20 vs. 155 & 175 19's on the regular
  • rides 0.4 inch lower on a wider track
  • 184 hp / 199 lb-ft vs. 170 hp / 184 lb-ft, via modified motor controls and tapered roller bearings
Source: REVIEW: The first delivered BMW i3 S in the United States

However, aside from the tire width / RR changes, we don't know what other changes they made that might affect rolling efficiency

__________________
Latest mods test: 15 mods = 15% MPG improvement: A-B test, 2007 Honda Civic 1.8L, 5-speed
Ecodriving test:
Manual vs. automatic transmission MPG showdown: Nissan Micra 1.6L



EcoModder
has launched a forum for the efficient new Mitsubishi Mirage
www.MetroMPG.com - fuel efficiency info for Geo Metro owners
www.ForkenSwift.com - electric car conversion on a beer budget
  Reply With Quote
The Following User Says Thank You to MetroMPG For This Useful Post:
aerohead (03-17-2018)
Alt Today
Popular topics

Other popular topics in this forum...

   
Old 03-16-2018, 09:39 PM   #12 (permalink)
Master EcoModder
 
freebeard's Avatar
 
Join Date: Aug 2012
Location: northwest of normal
Posts: 11,186
Thanks: 2,539
Thanked 3,582 Times in 2,836 Posts
My target weight is 1 ton so the 155-70/19 would likely be adequate.

I've tired of visiting websites that don't tell the weight of OP's Honda Odyssey.
__________________
.
Make Google don't be evil again.
_________________
  Reply With Quote
Old 03-16-2018, 10:11 PM   #13 (permalink)
Custom User Title
 
Gasoline Fumes's Avatar
 
Join Date: Oct 2009
Location: New York State
Posts: 1,091

Nut Wagon - '91 Honda Civic Wagon DX
Team Honda
Wagons
90 day: 67.84 mpg (US)

CRXFi - '88 Honda CRX XFi
Thanks: 502
Thanked 460 Times in 264 Posts
Quote:
Originally Posted by freebeard View Post
My target weight is 1 ton so the 155-70/19 would likely be adequate.

I've tired of visiting websites that don't tell the weight of OP's Honda Odyssey.
3,450 to 3,483 lbs according to cars.com via Google.
__________________
Best tank with the Honda so far is 81 MPG.

Last edited by Gasoline Fumes; 03-16-2018 at 10:17 PM..
  Reply With Quote
The Following User Says Thank You to Gasoline Fumes For This Useful Post:
freebeard (03-16-2018)
Old 03-16-2018, 11:47 PM   #14 (permalink)
Master EcoModder
 
oldtamiyaphile's Avatar
 
Join Date: May 2009
Location: Australia
Posts: 1,328

UFI - '12 Fiat 500 Twinair
Team Turbocharged!
90 day: 43.3 mpg (US)

Jeep - '05 Jeep Wrangler Renegade
90 day: 18.09 mpg (US)

R32 - '89 Nissan Skyline

STiG - '16 Renault Trafic 140dCi Energy
90 day: 31.99 mpg (US)

Prius - '05 Toyota Prius
Team Toyota
90 day: 50.25 mpg (US)

Premodded - '49 Ford Freighter
90 day: 13.48 mpg (US)

F-117 - '10 Proton Arena GLSi
Pickups
Mitsubishi
90 day: 35.66 mpg (US)
Thanks: 269
Thanked 339 Times in 247 Posts
Quote:
Originally Posted by Ecky View Post
My understanding of this is that "faster" on bicycle tires isn't strictly rolling resistance. Having very hard tires increases rider fatigue, even if the bike rolls easier, so you find people can't put as much power to the road for as long. It's a human limitation which motors do not share.

Correct me if I'm wrong, but a smaller contact patch will result in less rolling resistance, and there are several ways to achieve this. Adding pressure reduces sidewall flex, and sidewall flex eats less forward motion. However, sidewall flex is also what gives a suspension effect, because it also eats vertical motion. The reason we use hollow tires filled with air is not for speed, but for comfort, and to prevent irregularities in the road from tearing our vehicles to bits.

All else being equal, it's better for rolling resistance if the contact patch is longer and less wide, so if you're shooting for lowest rolling resistance possible (often at the expense of ride quality) you'll want very narrow tires with a relatively large diameter - approaching the shape of a bicycle tire.
These are lab test results, considering only RR, not rider fatigue. The difference is even greater with a rider and suspension losses.

A smaller contact patch has a lower RR in theory. Even the smoothest concrete is too rough for that to work in the real world.

Tech FAQ: Again, bigger tires roll faster! | VeloNews.com

EM style coast down testing:

https://janheine.wordpress.com/2012/...ance-of-tires/

Shape of Contact patch:

FLO Cyling - The Contact Patch... Why Wider is Better

Remember also CapriRacer's various posts on the subject, I used to be skeptical too

The i3 could be an example of an evolutionary dead end. No OEM since has gone that way.
__________________







Last edited by oldtamiyaphile; 03-16-2018 at 11:58 PM..
  Reply With Quote
Old 03-17-2018, 06:55 AM   #15 (permalink)
Duck duck duck
 
RedDevil's Avatar
 
Join Date: Dec 2012
Location: Nieuwegein, the Netherlands
Posts: 2,568

Red Devil - '11 Honda Insight Elegance
Team Honda
90 day: 59.18 mpg (US)

It - '09 Hyundai I10 Active Cool
Team Hyundai
90 day: 31.69 mpg (US)
Thanks: 927
Thanked 1,060 Times in 694 Posts
Racing bicycle tires cannot be compared to car tires. The shape of the contact patch, pressure on the tire, profile, construction, cross section are all completely different.

So Flo Cycling claims racing bicycle tires (with a extremely long and narrow contact patch) would have less rolling resistance if the patch was shorter and wider.
Sorry, I disagree wholeheartedly.
While it may seem logical at first glance it ignores what's really happening when the tire moves.

The contact patch is not static. As the tire rotates it shifts, obviously.
Now imagine the difference after shifting one inch. There'd be a new C-shaped section on one side while on the other side such a section is removed.
The total surface of the new section is the distance traveled times the width of the patch. That's the amount of rubber getting into contact with tarmac.

If the contact patch shortens and widens (assuming identical load and pressure) the C shape for the same distance will have shorter ends but a wider body. The surface still is distance traveled times width of the patch; as the patch is now wider, that area is also bigger; more new rubber getting in touch with tarmac, while the pressure is still the same.
That seems to indicate more friction for the wider tires, not less.
Now this was a simplified model; there are many other variables at play like the flexilbility of the tire, angle of attack on the contact patch, friction in the patch as the rounded tire progresses, etc.

Yet the truth is easy to find by looking at the tires used by professional road bicycle race teams. They typically use the narrowest tires possible at very high pressure.

As I wrote it is very hard to compare bicycle and car tires as they are fundamentally different. Yet, also on cars a wider tire does mean the contact patch area delta (change over a small distance) is equally larger, and so would be the rolling resistance.

Narrow tires with relatively high sidewalls and high pressure rule economy runs.
__________________
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 0.13 Gm or 0.08 MM.


Last edited by RedDevil; 03-17-2018 at 07:02 AM..
  Reply With Quote
Old 03-17-2018, 08:31 AM   #16 (permalink)
Cyborg ECU
 
California98Civic's Avatar
 
Join Date: Mar 2011
Location: Coastal Southern California
Posts: 4,889

Black and Green - '98 Honda Civic DX Coupe
Team Honda
90 day: 60.87 mpg (US)

Black and Red - '00 Nashbar Custom built eBike
90 day: 3671.43 mpg (US)
Thanks: 1,710
Thanked 1,394 Times in 955 Posts
Quote:
Originally Posted by MetroMPG View Post
... However, aside from the tire width / RR changes, we don't know what other changes they made that might affect rolling efficiency
Absolutely. But it is a reasonably safe assumption that they would not be using narrower tires if they knew it would undermine any further changes they were making to improve rolling resistance and range. Especially in the era of wide and low profile tire popularity.

This is a great discussion thread in general, too.

When I bought the MINI seven hole 15" wheels recently, it was partly because it had 175/65 tires. That is the same width as the tires on my 13" VX wheels. The new wheels are just 12 pounds to the old ones 9.7 lbs.

In sum, same width, much taller gearing modest but significant weight penalty.

I learned all of that on EM (sure hope it is true, haha!).
__________________


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 03-17-2018, 09:01 AM   #17 (permalink)
Tire Geek
 
CapriRacer's Avatar
 
Join Date: May 2008
Location: Let's just say I'm in the US
Posts: 684
Thanks: 0
Thanked 272 Times in 171 Posts
As has been pointed out, there are a lot of variables.

In fact, I looked at tire rolling resistance here: Barry's Tire Tech - Rolling Resistance and Fuel Economy

With a followup here: Followup an Rolling Resistance and Fuel Economy

Bottom line:

All other things being equal, a wider tire is better for rolling resistance - and it is likely that it will still be better overall - including aerodynamics, because tires are typically surrounded by the car body and only a small portion is exposed to oncoming air.

The biggest problem is that very rarely are all things equal. Proper selection of a tire can pay dividends in fuel economy.
__________________
CapriRacer

Visit my website: www.BarrysTireTech.com
  Reply With Quote
The Following 2 Users Say Thank You to CapriRacer For This Useful Post:
California98Civic (03-17-2018), COcyclist (03-26-2018)
Old 03-17-2018, 10:24 AM   #18 (permalink)
Cyborg ECU
 
California98Civic's Avatar
 
Join Date: Mar 2011
Location: Coastal Southern California
Posts: 4,889

Black and Green - '98 Honda Civic DX Coupe
Team Honda
90 day: 60.87 mpg (US)

Black and Red - '00 Nashbar Custom built eBike
90 day: 3671.43 mpg (US)
Thanks: 1,710
Thanked 1,394 Times in 955 Posts
Quote:
Originally Posted by CapriRacer View Post
... All other things being equal, a wider tire is better for rolling resistance ... The biggest problem is that very rarely are all things equal....
That's the problem alright. As the links you posted offer, there are four variables here (atleast). I'm certainly not about to put a 215 width tire on my car instead of a 175 and suffer an aero penalty unless I also take into account the publicly available "data" of weight, LRR reputation, and wheel face design (smooth or turbine?) for that 215 width tire/wheel combo.
__________________


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 03-17-2018, 01:07 PM   #19 (permalink)
EcoModding Lurker
 
Join Date: Jun 2009
Location: Vancouver, BC
Posts: 43
Thanks: 0
Thanked 30 Times in 15 Posts
Great discussion.
Freebeard, GVWR is 2150 kg according to door jamb sticker. Which seems incredibly high for. 2.3L 4 built on an accord chassis.
looks like I have to compare RR in tires in the size range I am looking for, as well as available rims. No real comparison to make, and once I bite the bullet and buy, I get what I get!
  Reply With Quote
The Following User Says Thank You to westygo For This Useful Post:
freebeard (03-17-2018)
Old 03-17-2018, 01:38 PM   #20 (permalink)
Master EcoModder
 
aerohead's Avatar
 
Join Date: Jan 2008
Location: Sanger,Texas,U.S.A.
Posts: 8,910
Thanks: 12,001
Thanked 4,704 Times in 2,661 Posts
tire width vs Cd

Some other reports which confirmed a direct correlation between tire width and aero drag were found with the:
*Pontiac Trans Am
*Subaru XT
Also,many of the lowest drag concept cars ran narrow tires as a low-drag strategy,including:
*GM Aero 2000
*GM Aero 2002
*GM Aero 2003
*Renault Vesta-II
*Ford Probe-IV
*LOREMO
*Daihatsu UFE I,II,III
*VW 1-Liter 2002
*VW 1L c 2009
*VW XL1 2016

__________________
Photobucket album: http://s1271.photobucket.com/albums/jj622/aerohead2/
  Reply With Quote
The Following User Says Thank You to aerohead For This Useful Post:
California98Civic (03-17-2018)
Reply  Post New Thread


Thread Tools




Powered by vBulletin® Version 3.8.11
Copyright ©2000 - 2018, vBulletin Solutions Inc.
Content Relevant URLs by vBSEO 3.5.2
All content copyright EcoModder.com