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Frame size: How to choose(10 posts)

Frame size: How to chooseSle
Jun 15, 2003 5:33 PM
According to mesurement, I should buy a 58cm bike. I currently have a Cannondale RS400 (58cm) and I'm looking to buy another bike this summer. The dealer offer me a great deal on a 2002 Cannondale R1000 but it is a 56 cm bike. What should I do: Pay a little bit more and buy a 2003 R800 or the 2cm difference does'nt make a big difference. The reason why I am hesitating is that the R800 need some upgrade (It come with cheap wheel) and is made with CODA (brake) Tiagra (front derailleur) and 105 (rear derailleur). The R1000 is made with good wheel (mavic) 105 brakes and Ultegra front and rear derailleur. Please help me on this subject.

Simon
2 cm doesn't make much differance...the bull
Jun 15, 2003 5:55 PM
in horseshoes! But on a bike it is all the differance in the world!Get the bike that fits you.Its more important than the group the bike comes with.
I'm with Bull..Dave Hickey
Jun 15, 2003 6:46 PM
Can you ride with the stem/bars 2cm lower than your size? The biggest problem I see with bikes too small is the saddle/handlebar drop. Of course you can always flip a stem or add spacers but IMHO, it just doesn't look right. 2cm is a lot when it comes to road bikes.
Some guidanceKerry
Jun 15, 2003 6:02 PM
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).
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 from the saddle. You simply cannot say "this is the right position for someone of your body dimensions" because there are too many variables and things that change with time. Get used to your position, and then occasionally make small changes: raise/lower your saddle, move your saddle forward/backward. Ride a while with the changes (a few 100 miles, anyway) and decide if it is better or worse. If it is better, keep moving in that direction. If it is worse, try moving the other direction. If you don't try, you won't find out, but it is a long term process, often taking years, to really dial in your position. And since your strength and flexibility are changing with time, it is reasonable that your position would need to change also.
this should be the FAQ on fit for RBRtarwheel
Jun 16, 2003 4:37 AM
Kerry covered all the bases. Gregg/Doug should put Kerry's response on the FAQ page -- if there is one.
I have a question to ask you...russw19
Jun 15, 2003 8:14 PM
As a shop employee who sees this situation all the time from some rival shops (we refuse to do it... and I actually try to talk people out of this) I have to ask you:

Are you willing to ride the wrong size bike for the next 2 to 5 years in order to save a few hundred dollars? Are you willing to suffer thru 2 to 5 years of bad fit and an uncomfortable bike for the sake of a nicer front derailleur and a nicer boutique wheelset? Is a front derailleur worth poor bike fit for that long?

2 to 5 years is what many active cyclists will keep a poorly fitting bike before replacing it according to industry numbers. Is it worth it to you for a few better parts or having that better bike right now! instead of in a couple months when the one that actually fits you is available and in your budget?

I personally could make this arguement, because as far as Cannondale goes, I actually take a 57. So either way, I am going up or down a centimeter and will have to change the stem to fit acordingly, but if you take a 58cm normally, you can "try" to make a 56cm fit with a seat post with a lot of setback and a longer stem with a zero rise or a lot of spacers under it, but I wouldn't really recommend that unless you are adjusting because you are between sizes rather than trying to fit a wrong size.

That's just my advice....

Russ
Listen to Russ!!!Kristin
Jun 15, 2003 8:45 PM
I sit around whining more than I ride these days because of bad fit. Just 2 days ago, I was so sick and tired of being uncomfortable--which can lead to severe pain--that I was ready to sell my $1300 road bike for $600 and buy another $500 hybrid. God, if someone could learn a lesson from my suffering, at least it might have some redeeming quality. It sucks having a bike that doesn't fit well.
Thanks everyoneSle
Jun 15, 2003 9:03 PM
Thanks for your answer. I will probably put a few hundred more and take a 2003 R1000 58 cm. Like this, I will have a good size frame and quality components I was seaching for.

Simon
Ah, well upgrading your budget is always the best answerKristin
Jun 15, 2003 9:12 PM
At least I keep telling myself that. While driving home tonight, I passed a license plate that read, "My Cake." Great plate!!
What is your true size? Are you in between sizes?Fez
Jun 16, 2003 5:23 AM
Its like Russ said. If you are truly a 58, then going to a 56 will be extreme.

If you are more like a 57 in a Cannondale, then you could go down to a 56 just like you could go up to a 58. Each direction has its pros and cons. But why compromise? Get the most accurate frame fit possible.