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does size matter?

I'm just starting out on this tri gig and plan to do a wee super sprint in may. i've a folding Airnimal bike with 24inch wheels that i plan to undertake this on, what i wondered was witht he loss of 2 inches how much speed am i loosing?


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    Jack HughesJack Hughes Posts: 1,262
    Lots. Unless your course is all up hill!

    I've planning an objective experiment to compare my 26" wheel mountain bike, with my nice shiny new 27" road bike.

    Currently, I have only subjective evidence.

    Last three rides on the same 10 mile course (mainly hilly, but all roads - "B", "A" and unclassified).

    Ride 1: MTB - Low wind - 45 mins

    Ride 2: MTB - High Wind - 50 mins

    Ride 3: Road Bike - Very High Wind (almost got blown over by side wind) - 42 mins.

    These were carried out over the space of about 4 days - so the quality of the engine is about the same!

    Other things being equal, I think the Road bike is worth about 10 minutes - i.e. a dramatic 20% faster.

    On the flat it would probably be greater.

    As I say, I plan to do a more controlled experiment to measure the difference - if I can get round to it.

    MTB is a good quality (shimano group set) from c. 1992 - no front suspension though!

    Road bike is not too expensive - only has carbon forks. But it is red.

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    its not the size of the boat its the motion in the ocean :D
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    gomiboygomiboy Posts: 59
    Wooly - yes tyre size makes a huge difference, but also the type of tyres. My road bike with 27" wheels has tyres that are about 1/2" thick, so almost no friction on the road. My mountain bike has 26" tyres that are nearly 2" thick, meaning more friction on the road even if they are slicks rather than nobbly tyres for off-road. A bike with 24" tyres, especially a folding commuter bike, will have not only smaller tyres (slowing things down) but likely thicker tyres (also slowing things down) than a road bike.

    I'd say heck yes for the folding bike increasing cycle time, but also increasing effort leading to a slower run because you've exerted more energy. The one time I did an Olympic tri on my mtn bike (Some caring, understanding, nineties-type had thoughtfully nicked my road bike a week before the race and I was too skint to afford slicks on my mtn bike) added 40 minutes to my bike time, but also an added 20 or so minutes to my run because I was so wasted after pushing that bloody mtn bike around the course that I had to walk large sections of the run.

    All that said, if you've got nothing else, then carry on, sir and have a great race! But if you've got the option, then a road bike will make all the difference in both your cycle time and the run as well.

    Good luck!
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    WoolyWooly Posts: 63
    Kinda confirms my suspicions, although the 24s at 1 1/8th thick so not much in the way of rolling resistance obviously going to be more effort, seem to spin out at 28-30 (albeit down hill). have to see if i can loan one for may, then try to preempt the WAT to get a tri bike for August.[:D]
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