Frame size pitfalls?

[novanino]

What would go wrong if I got a bike which was not the recommended frame size?
I've looked around for a secondhand bike to replace my broken one, and I've done the sizing thing and it seems like a 15" is recommended for my height (5'2") and type of bike I want (hybrid with 700c wheels).
I've never checked the frame size before getting a bike before, I always just checked whether I could put the seat at the right height. I haven't got my old bike to look at - it's being held at the police station til the case over the accident it sorted - so I don't know what size I was riding.
If I was to get a bike with a 17" frame for instance, what would be the problem?

I'm not saying I don't believe the advice on getting the right size. Just curious as to what goes wrong when you don't.

 

[cyberknight]

Assuming you can get the seat height right the biggest factor for frame size is the length of the top tube ,as the bike gets bigger the reach to the handlebars gets longer as taller people generally have longer torso`s and arms.
If the bike is a bit too big you can get away with putting a shorter stem on the handlebars to bring them closer but if you put a too short one on this can affect the steering of the bike , moving the seat to far forward can only cuounteract this slightly as your optimum setback for your seat affects the efficiency of your pedal stroke .
When overreaching for the bars you can also cause problems with your bike position causing aches and pains , i once bought a bike that was too big asit was a "bargain" and even though i tried to alter it to fit i could not get it right and suffered with back ache .
Another factor in bike sizing is whether the manufacturer measures the height where the seat meets the top tube or where it would meet if the top tube were level with the ground.The standard is the latter but some don`t which can be confusing.

 

[vickster]

I rode a bike which was a size too big for me for 6 months or so and ended up with chronic tennis elbow needing physio and a steroid jab - despite fitting a shorter stem. Hand ache, back ache and neck ache are other pitfalls

 

[simon.r]

The stated frame size should only be taken as a guide. There seems to be more consistency now, but a few years ago different manufacturers measured their frames in different ways anyway.

What's most important is that you feel comfortable, regardless of whether the sticker on the frame says 15" or 17".

 

[novanino]

Thanks for the very informative responses
If I'm 5'2" and a frame size measures 51cm I'm guessing that's a bad idea then....? (it's a ridgeback comet, and it needs work, so I can't try it out before buying )

 

[fossyant]

Are you a lady ? My missus has a small pinnacle stratus that just about right at 5,4 and only a couple of inches spare seat tube . Hers is about 15 inch. My son has a small full size mtb and he is 11.

I am male and 5.9 and would ride a 17 inch mtb. Most important is reach, and so long as you are correctly fitted for leg height as well the rest is adjustable.

Most importantly, try one out.