Re: Bridgestone Ecopia EP-03 Tires - Page 3 - DIY Electric Car Forums

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#21
07-31-2007, 03:44 PM
 EVDL List EVDL List Bot Join Date: Jul 2007 Posts: 70
RE: Bridgestone Ecopia EP-03 Tires

Phil,

I have not researched this much. Again, was looking for a narrow tire because all of the LRR machines I had used up to this point had always had narrow tires. Your argument that a narrower tire will have more sidewall flex and therefore greater rolling resistance makes perfect sense. You win!

However, I still wonder if the following reasoning could account for the perceived lower rolling resistance that I experienced on my road bike and on my street luge. As a tire of a specific tread width rotates, a length of rubber, whose length is identical to the tires tread width, is constantly coming into contact with the ground. This is the leading edge of the contact patch. As this length of rubber meets the ground, it must conform to the shape of the road. Every little rock and pebble will compress its own little area of rubber along this length of rubber. This requires energy in the same way that compressing the tire's side wall requires energy.

Now, I realize how difficult it is to imagine that this would consume very much energy, but how else can I explain a roller blade wheel out performing a skate board wheel down Donald street in South Eugene?

I guess a person could estimate how much energy is wasted this way. He could measure how much force is required to press a 1/2 inch by 1/2 inch square piece of rubber flat against a smooth surfece with a pebble sandwiched between the two. Then, that force could be multiplied by the number of pebbles across the front of a tire of a given tread width. Then, that number could be multiplied by the distance that tire would travel at a specific speed for a given amount of time.

I think that reading the rolling resistance chart would be easier though.

Brian

[quote]- Cor van de Water <xxx@xxx.xxx> wrote:

=============
Oh yes, width will definitely impact the rolling resistance.

The Bridgestone Potenza RE92 are the OEM tire specified for the
Prius from years 2001 to 2003, they used the XL variant, which
allows a higher load rating than the standard RE92.

They certainly have a low rolling resistance.

In fact, I switched from the RE92 to HTR-200 on my Prius
and noticed an MPG hit (which is normal when putting new tires
on a car, as the increased amount of rubber means more energy
wasted in friction during compression)

Hth,

Cor van de Water
Systems Architect
Proxim Wireless Corporation http://www.proxim.com
Email: xxx@xxx.xxx Private: http://www.cvandewater.com
Skype: cor_van_de_water IM: xxx@xxx.xxx
Tel: +1 408 542 5225 VoIP: +31 20 3987567 FWD# 25925
Fax: +1 408 731 3675 eFAX: +31-87-784-1130
Second Life: www.secondlife.com/?u=3b42cb3f4ae249319edb487991c30acb

-----Original Message-----
From: xxx@xxx.xxx.edu [mailto:xxx@xxx.xxx.edu] On
Behalf Of Phil Marino
Sent: Friday, July 27, 2007 5:48 AM
To: xxx@xxx.xxx.edu
Subject: Re: Bridgestone Ecopia EP-03 Tires

>From: Brian Jackson <xxx@xxx.xxx>
>To: xxx@xxx.xxx.edu
>CC: "Joseph T. " <xxx@xxx.xxx>
>Subject: Re: Bridgestone Ecopia EP-03 Tires
>Date: Thu, 26 Jul 2007 23:45:16 -0700
>
>True, old tires are very dangerous. Even if they don't blow out, they
>get hard and have poor traction. I am ashamed to admit that I actually
>caused an accident this way. I have an old set of tires on my Corvair truck
too.
>They don't have many miles on them, but they're about 10 years old. One
>of them blew out last week while the truck was parked.
>
>I have been looking at these tires for my EV project.
>
>http://www.tirerack.com/tires/tires.jsp?tireMake=Bridgestone&tireModel=
>Potenza+RE92&vehicleSearch=false&partnum=665SR4RE 92&fromCompare1=yes&pl
>ace=0
>
>Sorry for the long link. I have been looking at these because they are
>as narrow and as low profile as I can find for a 14" tire.
>
>Brian
>
>
Brian - do you know the rolling resistance factor for RE92's ? I don't
think I've ever seen them in a chart of low rolling resistance tires.

If you look at the GreenSeal paper, two of the lowest tires ( the
Bridgestone B381's and the Sumitomo HTR 200's are available in stock at
TireRack in 14 inch sizes - although not as narrow as the RE92 you are
looking at.

Why do you want the narrowest tire? Do you need a tire that small to fit

If not, it is more important to have a low rolling resistance tire. This
depends on the material and construction of the tire, not its width.

Phil Marino

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