How big is too big of a frame?
03-29-10, 11:35 PM
#26
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I'm 5' 10" with short legs and long torso. I have a 32" inseam measured Rivendell style). My favorite bike is my Bottecchia Grand Turismo. It's a 23" (58.5 cm) with a 73.5 degree seat tube angle. It's "square" so it also has a 58.5 cm top tube. I use a 105mm stem. I can just straddle it with shoes on and the top tube in contact with my pubic bone. My several other bikes are all slightly smaller, about 22" and are quite comfortable as well but not as much as the Gran Turismo. My Bianchi's are both much smaller (55cm for the Veloce and 53cm for the Pista though it has a high bottom bracket) but they both have proportionally longer top tubes so essentially they fit the same as the others but with more seat post showing. I don't find it bothers anything that I don't have clearance at the top tube. If I do crash I'll be falling off the saddle and landing on the top tube so I doubt an inch of clearance is going to help. And I've already had a vasectomy so no problem there 
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1959 Bottecchia Milano-Sanremo(frame), 1966 Bottecchia Professional (frame), 1971 Bottecchia Professional (frame),
1973 Bottecchia Gran Turismo, 1974 Bottecchia Special, 1977 Bottecchia Special (frame),
1974 Peugeot UO-8, 1988 Panasonic PT-3500, 2002 Bianchi Veloce, 2004 Bianchi Pista
1959 Bottecchia Milano-Sanremo(frame), 1966 Bottecchia Professional (frame), 1971 Bottecchia Professional (frame),
1973 Bottecchia Gran Turismo, 1974 Bottecchia Special, 1977 Bottecchia Special (frame),
1974 Peugeot UO-8, 1988 Panasonic PT-3500, 2002 Bianchi Veloce, 2004 Bianchi Pista
03-30-10, 12:39 AM
#28
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Use of a bike is a huge factor in both sizing and adjusting (ie. determining stem size and seatpost position) a bike to "fit". For road bikes, TT length (or more accurately saddle to handlebar length) is more important that ST length. I am riding 4 road bikes that vary in size from 51 to 57 cm (ST C-C) but their TT+stem are within one or two cms. My do it all mule and long distance bike (not included in the above count), has a longer TT
As far as stand-over height goes... I suspect that a lot of men really want to avoid the possibility of an involuntary vasectomy without anesthesia in a hard stop, thus the recommendation for straddling over the TT. And, frankly, it all depends on how experienced a rider is (so he can avoid such an unfortunate close encounter with the top tube.) If you think you are good enough to deal with a close encounter, more power to you, but if you try to size a novice cyclist...
As far as stand-over height goes... I suspect that a lot of men really want to avoid the possibility of an involuntary vasectomy without anesthesia in a hard stop, thus the recommendation for straddling over the TT. And, frankly, it all depends on how experienced a rider is (so he can avoid such an unfortunate close encounter with the top tube.) If you think you are good enough to deal with a close encounter, more power to you, but if you try to size a novice cyclist...
03-30-10, 05:32 AM
#30
Senior Member
A frame that is so tall that your crotch is smashed into the top bar is too big, and DANGEROUS. Your frame should be at least one inch (25.4 mm) shorter than your crotch height. You will usually find that a little smaller than your normal size will work better than slightly larger. A ROUGH estimate of proper size would be something like: your leg length minus 10 inches. So a 33 in. inseam = about 23 inch frame, or 58 cm. One cm smaller would be about right as well. Anything much larger would be too large.
03-30-10, 06:04 AM
#33
Senior Member
...QUOTE]
03-30-10, 09:51 AM
#34
PanGalacticGargleBlaster
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Different Manufacturers and Models have different Top Tube to Seat Tube relationships in terms of length...that makes it hard to pin down a size based on seat tube length....Knowing both the Seat tube and Top Tube length gives you a much better picture of how things are gonna fit.
03-30-10, 12:28 PM
#37
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Bottom bracket height can also affect frame sizing. A high BB will have a shorter C-C distance to the top tube.
Rim size and tire OD can alsoaffect frame sizing - large diameter rims and high profile tires dictate a smaller frame is needed.
The real key is stand-over height. You have to be able to straddle the bike without hitting your crotch on the top tube. It's as simple as that. If you cannot do that, the frame is too big. It doesn't matter how much you might like the frame, it is just too big for you.
Rim size and tire OD can alsoaffect frame sizing - large diameter rims and high profile tires dictate a smaller frame is needed.
The real key is stand-over height. You have to be able to straddle the bike without hitting your crotch on the top tube. It's as simple as that. If you cannot do that, the frame is too big. It doesn't matter how much you might like the frame, it is just too big for you.
03-30-10, 04:44 PM
#38
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Stand over height. It is important.
But it is of relative importance. I would never ride a bike I could not stand over for commuting -because I'm going to have to stand over the bike at red lights, waiting for turns, and sometimes just when I'm stuck in traffic and there are no apparent escape routes....
On the other hand if I was say going for a long ride out away from the city, then having a slightly oversize bike wouldn't be much of a hassle or safety concern.
In any event, the stand over height is the only fixed measurement of the bike (that pertains to rider fit), unlike handle bars and seat which can be adjusted to different positions, or stems that can be replaced to alter reach. So it IS important in that once you've chosen it, you have to stick with it.
And of course if you just collect bikes and hang them on the wall, then any size you like is right.
But it is of relative importance. I would never ride a bike I could not stand over for commuting -because I'm going to have to stand over the bike at red lights, waiting for turns, and sometimes just when I'm stuck in traffic and there are no apparent escape routes....
On the other hand if I was say going for a long ride out away from the city, then having a slightly oversize bike wouldn't be much of a hassle or safety concern.
In any event, the stand over height is the only fixed measurement of the bike (that pertains to rider fit), unlike handle bars and seat which can be adjusted to different positions, or stems that can be replaced to alter reach. So it IS important in that once you've chosen it, you have to stick with it.
And of course if you just collect bikes and hang them on the wall, then any size you like is right.
03-30-10, 06:17 PM
#39
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I understand your point but I disagree entirely. The safety concern exists at all times. Accidents happen. Things break. Stuff goes wrong. It happens. If you get dumped down off the seat it is going to hurt - maybe more, maybe less but it WILL get your attention.
When you are riding casually, as you suggest, it is no problem to slide off the seat and over to one side and let your thigh straddle the top tube. That's easy to do and you have plenty of time to effect the maneuver. But when the stuff hits the rotary air circulation device,...
Well, they are your future children at risk, not mine. :-)
When you are riding casually, as you suggest, it is no problem to slide off the seat and over to one side and let your thigh straddle the top tube. That's easy to do and you have plenty of time to effect the maneuver. But when the stuff hits the rotary air circulation device,...
Well, they are your future children at risk, not mine. :-)
