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Wheel speed tests- 88 faster than disc cover?
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Had some free time with no racing so I conducted several wheel tests on the TT bike on the same strava segments back to back to back, etc. See the attached word document for specific results and further info. Strava here:

This was not a scientific test but I did no changes other than the wheels and tried to minimize variables. There were very few cars and the shoulder is very wide. Tests were over 20 minutes each and I was going 24mph+ for all of these. Road is very flat. Wind was under 3 mph. Favero dual side assiomas calibrated before the ride.

Fastest to slowest:
#1: front 65, rear 88.
#2 Front 65, rear disc.
#3 Front 38, rear disc.
#4 Aluminum training wheels

Any ideas why the 88 was faster than the disc cover? Could the Ican hubs make that big of a difference? They spin fine in hand.
Last edited by: stevendex: Jul 31, 20 14:42
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Re: Wheel speed tests- 88 faster than disc cover? [stevendex] [ In reply to ]
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Edited to add the attachment. Wanted to test my new light bicycle carbon wheels. So far I'm impressed with them, especially for the price.
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Re: Wheel speed tests- 88 faster than disc cover? [stevendex] [ In reply to ]
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stevendex wrote:
This was not a scientific test...

Variable traffic, variable wind and air density, variable position, different tires, etc. Was the PM zeroed between runs? You can see that for the first 3 runs most of the difference was on the south leg rather than the north.

A deep rear wheel certainly could be better than disc cover, though. Disc covers vary a lot depending on how they fit.
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Re: Wheel speed tests- 88 faster than disc cover? [stevendex] [ In reply to ]
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88s often perform slightly better than a disc at zero yaw. It's really at larger yaws that the disc really begins to shine. Very possible that your test was effectively low yaw due to the wind direction and generally low wind speed. Overall, the disc is likely to be faster under most conditions.



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Re: Wheel speed tests- 88 faster than disc cover? [Titanflexr] [ In reply to ]
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Interesting. Neither section was into the wind, so there was a crosswind both ways, but yes, the wind speed was very low.

I think the fit of the disc has something to do with it too. It's not sitting flat on all the spokes and thus has a slight "wobble" to it.
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Re: Wheel speed tests- 88 faster than disc cover? [rruff] [ In reply to ]
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Position wasn't varied, and the tires are very similar if you review the notes. PM was calibrated before every run. I did not count the cars that passed, but this was a very wide shoulder road and traffic was very low on a Saturday morning.

I do think the fit of the cover has something to do with it. Possibly the changing weather/temperature as well. I wanted to do a couple more tests at higher power but had been riding for over 2 hours at that point; that's a lot of time in the TT position for me. Next time I'll bring a bike stand to assist in changing wheels.
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Re: Wheel speed tests- 88 faster than disc cover? [stevendex] [ In reply to ]
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If I were going to try to figure this out I'd do more runs and over more days. Yes that's a PIA but 1 trial doesn't tell you much.

Mix up the order as well so it wasn't always wheels ABBA. That way you get more diversity in conditions and can reduce the impact from an exceptionally calm or windy outlier type day. You could do adda, cbbc, acca dbbd. Probably wouldn't hurt to go through it all a second time as well.

I'd also buy new tires and use those to negate any advantage in crr that might occur from use and any changes in cda that could occur from squaring off due to use.

Trying to find this stuff out is hard work, love seeing the attempt!

Brian Stover USAT LII
Accelerate3 Coaching
Insta

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