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Thread: how much cruise speed loss with 29/31 Bushwheels

  1. #1

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    Default how much cruise speed loss with 29/31 Bushwheels

    Just wondering how much speed did guys lose switching from 600 or 850 size tires to 29 or 31 inch bushwheel tires?
    THANKS

  2. #2
    N981MS's Avatar
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    Default Re: how much cruise speed loss with 29/31 Bushwheels

    I lost 1-2 knots with 26s. I was surprised that it was that little.
    Maxwell Duke

    Kitfox S6 IO-240 Built it (Flying since 2003)
    Maule M7-235C Sold it (liked it though)
    RV-10 IO-540 Bought it
    Zenith CH-750 Built with 7 friends (DAR Vic Syracuse)

  3. #3
    Senior Member PapuaPilot's Avatar
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    Default Re: how much cruise speed loss with 29/31 Bushwheels

    I didn't notice any loss of speed going from the 600 to 850.
    Phil Nelson
    A&P-IA, Maintenance Instructor
    KF 5 Outback, Cont. IO-240
    Flying since 2016

  4. #4
    Senior Member AirFox's Avatar
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    Default Re: how much cruise speed loss with 29/31 Bushwheels

    1.5 mph going from 26" to 29"
    Scott Noble
    Kitfox SS7

  5. #5

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    Default Re: how much cruise speed loss with 29/31 Bushwheels

    So next question is what kind of cruise speeds are you seeing and with what engine /prop combo ,at what RPM on what model of kitfox ,just out of interest.
    I have 31 inch bushwheels on my Model 4/1200 with Rotax 912UL 80 hp and the IVO inflight adjustable prop,also have 12 inch tailwheel and yesterday was my first flight with this setup and cruise at 2500 ft at 5400 RPM on GPS was 97 MPH which I was very happy with.

  6. #6
    Super Moderator Av8r3400's Avatar
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    Default Re: how much cruise speed loss with 29/31 Bushwheels

    Specs:

    Classic IV-1200
    105 hp Zipper 912
    78" x 48" Prince fixed pitch prop
    26" Airstreaks
    700# empty weight

    I cruise about 100 mph at 5200 rpm. I can get 115 at 5800.

    With the large tires I can sustain climb at 1700+ FPM, solo with half fuel.


    With my 21x800-6 tires I am seeing about 3-5 mph more speed at the given power settings and 200 FPM more climb.




    My old plane, IV-1050, 650#, with 80 hp 912 and 68" 3-blade Warp taper tip, would easily see 15 mph more speed across the board, with a max of 1200 FPM climb when very light. Takeoff distance was substantially longer.
    Av8r3400
    Kitfox Model IV
    The Mangy Fox
    912UL 105hp Zipper
    YouTube Videos

  7. #7
    mattkalin's Avatar
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    Default Re: how much cruise speed loss with 29/31 Bushwheels

    Sorry to Revive an old post but is anyone actually running 31" Tires ? I am considering them for my build but probably will just stick to the 29". If you are running 31" can you post a pic and any comments on them?

  8. #8

    Default Re: how much cruise speed loss with 29/31 Bushwheels

    31” tires are not made in the airstreak line. The 29” Airstreaks are 25lbs each and the standard 29” are 31lbs each and the standard 31” are 32lbs each, and heavy tread are 36lbs each, so the standard 31” are a total of 14lbs heavier than the Airstreak 29” tires.
    Bryan
    Project Kitfox
    Bowen Aero LLC
    Kitfox Model 5 Lycoming O-290 D powered
    Building a Model 7 Apex powered
    Redding, CA
    http://www.youtube.com/c/ProjectKitfox

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