What size bike do I need?

General cycling advice ( NOT technical ! )
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Re: What size bike do I need?

Postby AMMoffat » 30 Jul 2019, 8:55am

5'10" with a 32" inside leg is quite a short inside leg measurement relative to height. I'd go for the size that means that the seat at the right height is no higher than the bars and then you can sort the reach with the right stem. That's assuming you are not doing any serious racing and need an aero, head down position, but if it your first road bike such a position is unlikely to be comfortable anyway.

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Re: What size bike do I need?

Postby 531colin » 30 Jul 2019, 10:42am

Marcus Aurelius wrote:......the 54 would probably give you a ‘twitchier’ ride, in comparison to the more relaxed 56. …...

Why is that then? On many "road" bikes, manufacturers use a steeper head angle on the larger sizes in order to get a longer reach for the same wheelbase. Unless they also use a shorter offset fork, steeper head angle gives less trail, ie faster steering.
The same rider would be expected to need a shorter stem on the larger bike, and its often said that shorter stems give twitchier handling; it may be the case that less weight on the front wheel gives a lighter feel to the steering.
Riding no hands, a short trail bike is easy to (for example) slalom the cats' eyes, but may be difficult to keep a straight line due to random steering inputs from eg road surface. No hands on a long trail bike the bike wants to go straight on and requires exaggerated angles of lean to "steer" it. Stem length has no bearing on how a bike steers no hands. :wink: