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Old 07-12-2010, 05:40 PM   #111 (permalink)
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Quote:
Originally Posted by CapriRacer View Post
The sidewalls do not consume much of the fuel when rolling. About 90% is the "tread" - the tread itself , the steel belts. and the plies.
CapriRacer, would you warn against cutting deeper threads (say 3 mm or 1/16") in a worn down (2 mm remaining) tire? Cutting custom threads is customary among racers, but I don't know if they start from special, non-treaded cores. In my case the tires in question are 6.00 x 16 diagonal threaded and retreaded (I think that's the correct term) tires for my 1938 Chevrolet pickup, the pattern being simple zig-zag that's easy to cut deeper.

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Originally Posted by CapriRacer View Post
Large capacity tires tend to weigh more - and that affects the accelleration - but in the big scheme of things, how much more fuel is consumed when accellerating larger tires, compared to the amount of fuel consumed when rolling.
Driving my 2000 Th!nk City EV I've found that a sudden deceleration (emergency stop, but not blocking the wheels) from 80 kph/50 mph to zero followed by a relatively fast acceleration to 80 kph takes as much energy as driving 5 km/3 miles at 80 kph constant speed on level road.

As each wheel acts as a flywheel I would think that there is something to gain in the weight of the wheels. No rim supplier nor any tire supplier have been able or willing to give the weight of their product.

My 155/70R13 Continental EcoContact summer tires are fitted to original aluminium rims and my 155/70R13 Continental WinterContact tires are fitted to original steel rims. Would you believe that the winter wheels are lighter than the summer wheels? Can the winter tires be that much lighter than the summer tires? Taking one of each apart to weigh them separately is out of the question as the work would cost as much as a new set of tires.

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Old 07-12-2010, 07:58 PM   #112 (permalink)
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Originally Posted by El Rayo View Post
No rim supplier nor any tire supplier have been able or willing to give the weight of their product.
Practically every manufacturer of alloy wheels worth a crap lists out the weights of at least some of their wheels! And I'd bet a shiny nickel that you could ask for the weights of the sizes that they don't advertise, and they would tell you...

Tires, not so much. But you may be able to get a shipping weight for them from the mail-order tire shops.

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Old 07-13-2010, 06:11 AM   #113 (permalink)
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Quote:
Originally Posted by El Rayo View Post
CapriRacer, would you warn against cutting deeper threads (say 3 mm or 1/16") in a worn down (2 mm remaining) tire? ....
Yes. In passenger car tires, there is only a little bit of rubber on top of the belts. Reducing it tends to produce cracks, which allows moisture and other contaminants into the belt, which causes corrosion, which leads to the belt coming off - ala the Firestone tires.


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Originally Posted by El Rayo View Post
.......Cutting custom threads is customary among racers, but I don't know if they start from special, non-treaded cores. In my case the tires in question are 6.00 x 16 diagonal treaded and retreaded (I think that's the correct term) tires for my 1938 Chevrolet pickup, the pattern being simple zig-zag that's easy to cut deeper........
Truck tires get a little more tread and are a little safer to regroove - particularly if they are designed to have this. Your retreaded tire no doubt have been retreaded with this in mind.

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Originally Posted by El Rayo View Post
......Driving my 2000 Th!nk City EV I've found that a sudden deceleration (emergency stop, but not locking the wheels) from 80 kph/50 mph to zero followed by a relatively fast acceleration to 80 kph takes as much energy as driving 5 km/3 miles at 80 kph constant speed on level road.......
I think what you are saying is that each time you accelerate or brake, you get the equivalent of 2 km or 1 miles of fuel (including how much distance you travel it takes to do that). This doesn't sound like a lot. When I drive to work, I drive 10 miles and accelerate (and stop) 5 times = 15 miles.

If I improve the weight of the tires by 50% (which is pretty much absurd), I am only improving the mass of the car around 1%.

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Originally Posted by El Rayo View Post
........As each wheel acts as a flywheel I would think that there is something to gain in the weight of the wheels. No rim supplier nor any tire supplier have been able or willing to give the weight of their product......
I think you'll find that Tire Rack has the weight of every tire they sell!

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Originally Posted by El Rayo View Post
...........My 155/70R13 Continental EcoContact summer tires are fitted to original aluminium rims and my 155/70R13 Continental WinterContact tires are fitted to original steel rims. Would you believe that the winter wheels are lighter than the summer wheels? Can the winter tires be that much lighter than the summer tires? Taking one of each apart to weigh them separately is out of the question as the work would cost as much as a new set of tires.
I think you'll find that alloy wheels are not as light as you may think. Properly designed, a steel wheel should weigh exactly the same amount as an alloy whel. The principal is called "strength density" and for most metals, it is the same. (Carbon fiber is really good compared to most metals) The trick is to make sure the metal is being used effectively and not just occupying space - which happens a lot (and not just in wheels!)
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Old 08-30-2010, 12:16 AM   #114 (permalink)
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Thank you for the information...........
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Old 08-30-2010, 11:04 AM   #115 (permalink)
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I apologise if this has been covered already but I've not been through all twelve pages - but aren't many of the tires listed in the first post actually quite wide ones? Surely the biggest rolling resistance benefit is from finding narrower tires.

Obviously that's not often possible the further you go up in rim diameter, but for the smaller tires there must be narrower options? The narrowest listed for 15" wheels there are 195 section, which is what my Miata has on aftermarket wheels... and I consider those quite wide for the size of car... I'm damn sure there must be LRR tires in narrower widths than that for 15" rims!

The original Insight had 165/65 R14 tires, Bridgestone Potenza RE92s. I'd expect those are fairly LRR and I can't believe there aren't competitors for other brands in that size or similar widths.

This isn't criticism... more an observation on what's otherwise a very comprehensive list
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Old 08-30-2010, 08:06 PM   #116 (permalink)
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Quote:
Originally Posted by AJI View Post
.......Surely the biggest rolling resistance benefit is from finding narrower tires.........

You would think that but the data suggests that there are other things that may have more impact. I've tried to catalog them here:


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Old 08-30-2010, 10:47 PM   #117 (permalink)
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AJI: IIRC 15" tires are readily available down to 135 width for the old school VWs.
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Old 08-31-2010, 12:31 AM   #118 (permalink)
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Quote:
Originally Posted by CapriRacer View Post
You would think that but the data suggests that there are other things that may have more impact. I've tried to catalog them here:


Barry's Tire Tech
Are you sure about the testing methodology you mentioned here?
Quote:
When tires are measured for RR, one of the test conditions is the load - which would be larger for larger tires.
Do You have a link to a description of the testing methodology? I've never heard of upping the test weight/force for larger tires.
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Old 08-31-2010, 06:12 AM   #119 (permalink)
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Are you sure about the testing methodology you mentioned here?....
Absolutely! You can even see it if you compare the 2 graphs. It's obvious there is something that changes the RRF to RRC - and that something is the test load.

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Originally Posted by roflwaffle View Post
..........Do You have a link to a description of the testing methodology? I've never heard of upping the test weight/force for larger tires.
Google "SAE Rolling Resistance Testing" Lots of references there to RR methodology.
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Old 08-31-2010, 12:19 PM   #120 (permalink)
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I can't find any info on the test load. Is it just the tire/wheel combo, loaded proportionally to the tire's load rating, or something else, what's the ratio of load?

Edit- NVM, standard load is 70% of the max.

I'd also be cautious about coming to any broad conclusions regarding Crr/tire size w/o excluding OEM tires and insuring all the tires were constructed via the same method. It could be that the more expensive version of the same name brand are using different compounds that lower Crr, and/or that the OEMs (they tend to shoot for lower Crr to help out w/ the EPA mileage testing) are moving things around a bit, not necessarily that larger tires in and of themselves have lower Crrs.


Last edited by roflwaffle; 08-31-2010 at 12:37 PM..
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