RoadBikeReview.com's Forum Archives - Racing


Archive Home >> Racing(1 2 3 )


Frame size, what to do?(4 posts)

Frame size, what to do?sammy
Nov 18, 2003 4:15 PM
Suggestions needed! I feel like my frame is to small, standing flat footed over the top tube in normal shoes my crotch is resting right on it. So that does show the frame is plenty big, but setting on my rollers, spinning away I feel cramped in the hip area. I just added a Thompson set back seat post and my flite saddel is all the way back on the rails, but I would still like to scoot back more, Also have large bars and a longer goose neck. I'm afraid by going to the next sized frame, I will not be able to stand over it flat footed, is there a rule about being able to stradel your bike flat footed?
Very confusingKerry Irons
Nov 18, 2003 6:10 PM
You don't give any measurements so it's a bit hard to sort out, but generally you should have a couple of cm of clearance (roughly an inch) for standover. Yet you say that you have zero standover clearance and are too cramped. I'd suggest you take some measurements and then visit one or more of these fit calculators.

Measure your inseam: stand against a wall with your feet 6 inches/15 cm apart. Push the spine of a 1 inch/2-3 cm thick book into your crotch with significant pressure, with and measure the distance from the book spine to the floor. Your saddle top to pedal axle should be 108-110% of the inseam measurement.

To measure your knee over pedal spindle (KOPS) situation, drop a plumb line from the front of the bony protrusion just below the knee cap.

http://www.bsn.com/cycling/ergobike.html
http://www.coloradocyclist.com/BikeFit/index.cfm
http://www.sheldonbrown.com/harart-frames.html
http://www.rivendellbicycles.com/frameinfo/Frame_Sizing.htm
http://www.peterwhitecycles.com/fitting.htm

For adjusting the fit of the bike, there are roughly five starting points:

1. Seat height (top of saddle to center of pedal axle) at 108-110% of inseam.
2. Saddle parallel to ground.
3. Saddle fore/aft adjusted so that a plumb bob from the bony protrusion just below the kneecap passes through the pedal axle when the cranks are horizontal. This is known as KOPS (Knee Over Pedal Spindle)
4. Front hub axle obscured by the handlebars when riding in your "regular" position (drops, hoods, or tops). NOTE, this is when you drop your eyes to look - if you drop your head, it will "move" the hub 2-3 cm and goof you up.
5. Top of handlebars 1 to 4.5+ inches below the top of the saddle depending on your flexibility and size.

These are all starting points for "average" proportioned people, and many folks like to move away from these starting points as they learn what makes them more comfortable, powerful, or efficient. You want to get the fit of the frame as close as you can, then do minor adjustments with the stem, seat post, saddle position, etc.

A lot of this is personal comfort, and we all tend to adapt to a given position over time. For example, a given stem length may be right for you, but it may feel long at first. I use the "handle bar obscures the front hub" rule for my fit, but others claim better position (for them) with the hub in front of or behind the bar. I'm 6' tall and ride with 11.5 cm drop from saddle to bar, probably more than most people would like but fine for me. Some are suggesting zero drop from saddle to bars - it's about comfort, efficiency, and aerodynamics. The ERGOBIKE calculator is pretty good, but it is not infallible. I would suggest riding some miles (over 100 total, and over 500 would be better) and see if you adapt to the position. There are no hard and fast rules, just general guidelines, when it comes to these things.

Just as important as your size is your flexibility. If you have a stiff lower back, you may not be able to lean over and stretch out as much. If you are very flexible, you may get away with a longer top tube, with the stem in a lower position. Over time on the bike, too, you may become more limber, or at least become accustomed to being lower and stretched out. So, your first 'real' bike may not be anything like what you will want 5 years from now.

Someone new to road riding is highly unlikely to find their ultimate position on the first go. As they become accustomed to the riding position and get some miles in, sometimes over several seasons, people often find their desired position changing. What was "stretched out" now feels OK, or what was "just right" now feels cramped. With time, if you are working on your position along with all your other riding stuff, seat position tends to rise, handlebars tend to be farther below the saddle, saddles tend to move rearward, and handlebars tend to be farther forward fr
Thompson set back seatpost isn't very set back.MR_GRUMPY
Nov 19, 2003 6:11 AM
The Thompson "bent" seatpost gives as much set back as the "average" seatpost. When I changed to an Easton post, I was able to move my Flite to the middle of the rails. It gives almost an inch more of set back over a standard seat post. With that seat post and my 130mm stem, I've got lots of room on my frame.
Thompson set back seatpost isn't very set back.sammy
Nov 19, 2003 1:08 PM
Thank you for your reply's, to both of ya!
The Easton seat post sounds interesting.
I should have just paid and been fitted, but this frame seems plenty big.
The frame is a BIANCHI ALLORO 55 size, stem a 135, bars like 44's. My inseam is like 30''I guess I'm a little short legged, over all hieght, is 5.9.
I feel some discomfort in the right hip while pedaling, possibly to cramped.
I changed my MTB post and was able to move seat back more so, noticed a great amount of relief while riding.