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Downsizing Wheels & Tires

6 messages,  Last post on Apr 13, 2010 at 3:52 AM

You are in the Toyota Camry Forum.

What is this discussion about? Toyota Camry, Tires, Sedan

Messages Page 2 of 2

#4 of 6 Re: 2005 LE- Downsizing Wheels & Tires [matt_e_boy] by capriracer

Apr 10, 2010 (6:27 am)

Replying to: matt_e_boy (Apr 09, 2010 6:40 am)
Matt,
 
Here is what I am basing my statement on:
 
http://www.energy.ca.gov/transportation/tire_efficiency/documents/2007-12-07_wor- - kshop/presentations/Lambilotte_Bruce_Task%204%20Rolling%20Resistance%20Testing.p- - df
 
This is a study performed by Smithers Scientific Services for the California Energy Commission to explore rolling resistance in tires and what effect certain laws might have on the general public.
 
On page 31 is a graph showing the Rolling Resistance Coefficient (RRC) for various sizes of tires but all the same make/model. I think it is easy to see that small tires (load carrying capacity wise) have better RRC.
 
They actually calculated a correlation value - and it was pretty poor at 50% - but the trend is there.
 
Conclusion: If you want to improve fuel economy by changing tire size: More load carrying capacity = Better

#5 of 6 Re: 2005 LE- Downsizing Wheels & Tires [capriracer] by matt_e_boy

Apr 12, 2010 (8:21 am)

Replying to: capriracer (Apr 10, 2010 6:27 am)
Ummm Capriracer, did ya see page 35?
Looks like a positive correlation between rolling resistance and load index to me.....
It's also interesting to note rolling resistance increases with UTQG ratings and tire weight.

#6 of 6 Re: 2005 LE- Downsizing Wheels & Tires [matt_e_boy] by capriracer

Apr 13, 2010 (3:52 am)

Replying to: matt_e_boy (Apr 12, 2010 8:21 am)
Matt,
 
Be very careful here. The way tires are tested for rolling resistance includes compensation for the load carrying capacity of the tire. What you get is rolling resistance force. To compare tires of a different load carrying capacities, you need to divide by the load to get rolling resistance coefficient (RRC). When you change tires on a given vehicle, the load on the tire doesn't change - so you have to use rolling resistance coefficient (RRC).

Messages Page 2 of 2

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