Peakster's Experiment #6: Mmm... DONUTS!
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Stemming off from one of my earliest threads here at GS, I finally got off my butt and did the donut tire experiment today. Here's the breakdown:
YouTube Video of Experiment Attachment 446Attachment 447Attachment 448 Date: May 5th, 2007 Method of testing: A-B-A Time: 3:00pm - 5:00pm Temperature: 19*C-18*C Winds: coming from the North-East @ 20km/h - 26km/h Speed: 50mph with cruise control Route: Attachment 445 As always, there's a fun YouTube video to watch, but here are the findings: 1st run with regular all-season tires: 56.9 mpg run with 'donut tires' for back wheels: 60.9 mpg 2nd run with regular all-season tires: 54.9 mpg Average with regular tires: 55.9 mpg Average with donut tires: 60.9 mpg 8.94% FE increase with donut tires. Needless to say I was shocked at the FE improvement. I could feel the car gliding better with the donuts in the city, but it definitely showed up on the highway too. Another thing I think could be a possiblity is that with the smaller donuts on the rear, the Geo may have had a slightly smaller 'wake' of air behind it. Thus making it more aerodynamic? What do you other members think of the results? |
I think that it's time for me to try this with the Green Machine. Has anyone had any wear problems with donut tires? I've never had to use the spare yet.
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I'm suprised at this. I would think that there would be more drag due to the huge gap between tire and wheel well and the lifting of the front end due to smaller tires. I don't see where the increase in FE is coming from. Couple of questions:
This is non stop right? No EOC on the route when testing? So the distance and speed stays the same because the front wheels were not changed? How much weight difference on the wheels? Although once at speed I won't think it would matter. Wheel skirts would probably be easy(no bulge) and help even more with the spare. I guess now there will be a run on spares at the junk yard all across the contry.:) |
I have been waiting for this experiment. Good experiment and good results. My only question is, "what psi did you have the original tires at and at what psi did you have the donuts at?"
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Very interesting... I would have thought that - but it's great to see it quantized :D
My car comes with a full sized spare though :p |
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Donuts: ~60psi Stock tires: ~50psi I think the main difference is the donuts have much less surface area with the ground. I could do another test with the donuts at 50 psi too just so it would remove that factor... but that just means more work for me :rolleyes:! |
i think the have less rr so thats prolly it
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Less rotating weight + Better rr.
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