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Frame Size......is it a fine art?(26 posts)

Frame Size......is it a fine art?Wild Bill
Dec 30, 2001 5:20 AM
.67 x inseam, is this measurement carved in stone?
I have short legs compared with my body size. My friend and I are the same height and his inseam is 1.75 longer than mine.
If your size works out to be say 54cm. and you were riding a 56cm. or a 52cm. would this cause a problem?

Would it be better to fit the smaller size?
Would the larger size be more comfortable?
I know the top tube will vary in length depending on the frame size.
KOP, having short legs will force you to have a more forward seat.
What about the stem? Is a longer stem better?
A long stem aids in climing, but what about comfort on a long ride?
The last thing is the difference in the top of the saddle and the top of the bars.
I know this is all been said and done before, but I need to hear it again.(Sheldon Brown just dosen't do it for me).
So let me hear it from the best!
re: Frame Size......is it a fine art?mackgoo
Dec 30, 2001 5:35 AM
Personally I have no problems. I seem to be able to fit to most positions. Then you would hear others on this board they are of by 1mm and they are in so much pain they can't ride. So this really is a personal thing and you go taking responability for your choices. Tere are all kinds of references for starting points and I'm sure you'll get pointed there soon. The reference's work for me and I can even vary from the and still feel good.
To a point.nee Spoke Wrench
Dec 30, 2001 7:06 AM
I've often thought that using seat tube height as the litmus test for frame size was wrong. Seat height is the easiest adjustment to make on a bicycle. I tend to think that top tube length would be a more accurate measure if only we had a nifty .67 X inseam formula to cite.

After saying all of that, I'd recommend you start with your .67 seat tube formula anyway. That's probably going to give you an answer that falls between two frame sizes. If you are an aggressive rider, get the smaller frame size and use a longer than stock stem to match your longer than average torso. If you are more of an enthusiast rider than racer, get the larger frame size because you'll probably like the higher handlebar position better.

While getting the correct size is important, a minor mistake can always be fixed. Truth is, most people make minor adjustments in their riding position as their fitness level changes through the season. I think that the worst mistake you can make is to get tied up in reading so many articles about bike fit that you become afraid to buy ANY bike for fear it will be the wrong size.
re: Frame Size......is it a fine art?cycleguy
Dec 30, 2001 7:28 AM
If I only choose my bikes by some of the fomulas that I have used I would never of bought any of the bikes I have. I tend to like a bigger bike as I'm older, don't race, and like a more comfortable upright posistion. But as the others have said thats just me. Find a shop or frame builder with a sizing cycle. For a fee you can have them move everything and you can find what works and what does not. Much better then any fomula.
re: Frame Size......is it a fine art?tr
Dec 30, 2001 7:54 AM
My legs are short for my torso also. Effectively i have always looked for relatively long top tube without too much seat tube length. You don't want to have too much length in seat tube to the point of having your seat just above the top tube (which would be the case with a frame way too big). And with a smaller frame you don't want way too much seat post showing and a long stem that doesn't quite give you enough top tube length. Like was said above, if you are aggressive racer it might be better to error on small size and if you want comfort for long rides (and ride with hands on shifters usually)it would be better to error on the big size. The bigger bike would possibly be more comfortable as far as the distance from seat to bar would not be as much. This is easier on the back.
.67 or .65?colker
Dec 30, 2001 8:10 AM
??????
and yes, i think it's a fine art. buy a one size bigger road frame will never hurt.
.67 or .65?gtx
Dec 30, 2001 10:16 AM
.67 is for bikes measured c-t and .65 is for c-c.
how does a long stem aid climbing?collinsc
Dec 30, 2001 9:23 AM
thanks,
Chad
Stem length and climbing...Cima Coppi
Dec 30, 2001 11:47 AM
An advantage to using a longer stem for climbing is that it puts your center of gravity more towards the front of the bike, aiding in the battle against gravity. It's much more difficult to climb when your upper body is way back over the rear wheel.

CC
???CT1
Dec 30, 2001 2:16 PM
Can you explain why this is so??? BTW: I don't "buy it".

JohnG
Stem lenght ??noupi
Dec 30, 2001 9:27 AM
I am 5' 7 1/2" ,my inseam is 32". I ride a 56cm Trek 2200
the standover hight is fine but the 56.1 cm top tube is a little long for me. I am 50 years old and with little flexability,so i do not bend over the bars.
I have a 90 mm stem on the bike now and I have found a 60mm
stem (made by Salsa)I think this would resolve my problems.
Is there a negative side to having a 60mm stem ??
Are there other manufact. that make short stems out there ?
thanks,
Stem lenght ??gtx
Dec 30, 2001 10:14 AM
your bike soundsl ike it's too big for you. Such a short stem will make the handling on the twitchy side. I'd get a new bike that fits, perhaps custom.
need some specificsgtx
Dec 30, 2001 10:12 AM
it's kind of hard to generalize.

how tall are you? what is your inseam? what are the dimensions (seat tube, seat tube angle and top tube) of your current bike? what do you like/dislike about your current bike?

Ignore KOP and go with what feels good. But many people with shorter legs will prefer bikes with steeper seat tube angles (check out Klein, Gios, etc.). Generally, in terms of stems, you should fit well on a bike with a 10-12 cm stem--shorter or longer will effect the handling. Top of the saddle to the top of the bars depends on the person--generally how flexible and in shape you are.

And if you have short legs, maybe consider a "compact" style road frame--this will take standover out of the equation. And test riding specific bikes will often clear up stuff that seems confusing on paper.
need some specificsnoupi
Dec 30, 2001 10:56 AM
I am 5 ft 7 1/2 inches tall ,32inch inseam
My bike is a Trek 2200, 56cm c to top of TT, top tube is 56 cm long, 73.5 degree seat tube angle.
My problem is Iam not that flexible (50 years old) and when riding I am always pushing myself back on the back of the saddle
I also have my saddle way forward so my only option is to shorten the stem, but if you say it will make the bike hard to handle then I am screwed.
stem height & lengthC-40
Dec 30, 2001 3:54 PM
Your proportions are about right for a good fit on most road bikes. I'm about an inch shorter than you (with longer legs) but I would still use a 100mm stem on this frame (at age 48). If you have a back problem that can't be solved with stretching & strengthening exercises, a higher bar position may be of more benefit than a shorter reach. You should consider getting a stem with more rise. Flipping an 80 degree stem will change the angle to 100 degrees, raise the bars over 3cm, and shorten the reach by about 1cm.

Moving the saddle to correct a reach problem is a big mistake. The saddle adjustment is for the purpose of placing the knee in the correct relationship to the crank. See the fit info at coloradocyclist.com for an explanation on how to adjust the knee-over-pedal (KOP) position.

Reducing the stem length by 30mm is kind of drastic. A 60mm stem could create knee/elbow interference when you ride in the drop section of the bars. A 60mm stem will make the steering a bit quicker, but it's something that you should be able to adapt to. Don't believe that baloney about making the bike unrideable.

The Trek frame does have a little longer top tube than many others, but you won't find any stock frames that are more than 1cm shorter.

If your lack of flexibility is just a matter of not stretching, you should consider exercises that strengthen the abdominals and increase flexibility. Riding a bike alone will not produce the strength and flexibilty needed to be comfortable on a racing bike. I regularly use a $10 "ab wheel" that strenthens the abs and stretches the shoulders. I also do hanging knee raises and simple toe-touching stretches. Eventually, you should be able to place you hands flat on the floor.
need some specificsCT1
Dec 30, 2001 4:06 PM
I'm 5' 8" with a close to 32" inseam. I ride 54cm CT sized frames and find that size to be the most appropriate. I usually try to setup up my bikes with around 3" on saddle to bar drop.

I don't know the exact dimensions of the 56cm 2200 but I would guess that this frame has a long top tube for you. Your comment about setting the saddle forward also implies the TT is too long. What length stem are you using???

Good rides
JohnG
need some specificsnoupi
Dec 30, 2001 5:13 PM
CT1, I am using a 90 mm stem now.
I think C-40 is right,my problem is flexibility,If I bend down to reach my toes, my finger tips are 16 inches to the ground !!!
Ive been stiff has a board all my life.
I started riding last july and really enjoy it, 2500 Kms,
Now I have a reason to start streching exercises.
But right now,for me to touch the ground with my fingers
is an impossible dream :-(
need some specificsCT1
Dec 30, 2001 5:30 PM
Ah, I see.

Make sure you don't buy another bike at the shop that sold you the 56cm. ;-(

It sounds like you can possibly make the 56cm work but don't discount the idea of trading for a 54cm and or a frame with a shorter TT.

I've got a TCR that has a longish TT (for me) and I can say without a doubt that the fit does impact the riding enjoyment of the bike. I'm using a 10cm stem on that bike and even with a near "identical" geometric setup as my other bike the dang thing just doesn't "feel" as "right". :(

good luck with the stretching and good rides to ya.
JohnG
agree nmgtx
Dec 30, 2001 5:34 PM
Thanks for all the inputnoupi
Dec 30, 2001 6:19 PM
I really like this site
stick around long enough.....andCT1
Dec 30, 2001 7:14 PM
You'll get flamed by someone. ;-)

When it happens don't respond ...... better for you and worse for the jerk doing the flaming.

good rides
JohnG
Use some dataKerry Irons
Dec 30, 2001 7:09 PM
Here's some sizing calculators:

http://www.bsn.com/cycling/ergobike.html
http://www.coloradocyclist.com/BikeFit/index.cfm
http://www.sheldonbrown.com/harart-frames.html
http://www.electriciti.com/~bikelane/sizing.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 only starting points, and you can size a frame and get a reasonable position with them. After that, it is dependent on your flexibility, your proportions, and your preference.
re: long torso, short legsguido
Dec 31, 2001 1:06 AM
67 x inseam, is this measurement carved in stone?

No, but its the best place to start.

I have short legs compared with my body size.

So do I, so I round off my frame size calculation to the highest centimeter and ride with a long stem on a bike with a long top tube: 54cm frame (C-C), 55cm top tube with 12cm stem.

If your size works out to be say 54cm. and you were riding a 56cm. or a 52cm. would this cause a problem?

Since I have a long torso, the 56cm frame I once had was really comfortable. The long top tube held its line nicely. The big frame soaked up vibrations well. A 53.5cm frame I now have requires a really long stem, 13.5cm, which puts alot of weight over the front wheel. The bike will sometimes unexpectedly shimmy on a descent unless I scoot back on the saddle.

Would it be better to fit the smaller size?

Not for anything but flat out racing. The top tube would be too short for your back, and the handlebars would be too low and too far over the front wheel.

Would the larger size be more comfortable?

Absolutely, not only because it provides a roomier cockpit for your back and arms, but because the longer frame tubes will soak up road vibrations more completely.

I know the top tube will vary in length depending on the frame size.

Generally, top tubes come the same length as seat tubes, except on slant top tube "compact" frames. Small frames typically have longer top tubes and steeper seat tube angles, because short Europeans and American males typically have proportionally longer torsos. I think perusing specs will bear this out.

KOP, having short legs will force you to have a more forward seat.

Small frames, 53, 52cm. put the seatpost furthur forward, 74, sometimes 75 degrees. That's good, because it enables you to work up a good spin, and also put some body weight over the crank and put some power into the stroke. Sprinters slide forward on the saddle for this reason. Larger frames come with 74 degree seat tube angles, though. Most riders (!?) prefer 73 degrees, saying it gets more of the rider's weight over the rear wheel, and gives a bit more leverage, sitting back furthur behind the crank.

What about the stem? Is a longer stem better?

If there's not too much rider body weight over the front wheel, a longer stem provides a longer steering lever, and puts your hands furthur out over the front wheel. This gives a nice degree of directional control, and seems to dampen road shocks coming through the front wheel.

A long stem aids in climbing, but what about comfort on a long ride?

Well, that isn't an unqualified yes, because comfort on a long ride is determined by overall positioning on the bike, fore-aft balance over the two wheels, enough room along the top tube to expand the rib cage and breathe, and move around on the bike.

The last thing is the difference in the top of the saddle and the top of the bars.

The bars don't have to be much lower than the saddle if the reach is far enough so your upper body can easily rotate from the tops to the hoods to the drops without scrunching up. If you want to go fast, get on the drops. Your arms can be bent 45 degrees at the elbows and your back can be horizontal but still flat. If you want to sit up, you can with your back still straight.

I know this is all been said and done before, but I need to hear it again.(Sheldon Brown just dosen't do it for me).

Err on the large side, because the way you're doing it will get you very close to right on.

So let me hear it from the best!

Flattery will get you way more than you asked for!
re: long torso, short legsWild Bill
Dec 31, 2001 4:37 AM
Thanks to all who answered my questions.
I hope my post has helped others.
Wild Bill
excellent advice! ..nmSharky
Dec 31, 2001 6:15 AM
more like trial and errorDog
Dec 31, 2001 7:20 AM
You ever sight in a rifle? Fit is a bit like that. You just can't run some numbers and dial in the scope. You gotta shoot the thing and see what happens, then make adjustments.

I think many people make way too much out of "fit," as if it must be dialed in by the nanometer, and you'll make twice as much power and suddenly be floating on feathers when it gets perfect. I think, based upon my own fiddling around for years, and you get is pretty close, experiment a little, and sooner or later you'll find something that works for you.

Sure, it helps to get the advice of an experienced observer, like a coach or good bike shop employee. They can get you close, but they will have their own biases and won't know that it feels like *for you* on that setup at the end of a century. Only you can try to pay attention, experiment, and slowly dial it in.

The fact that there are a good dozen or so methods to get the fit right, and they all give various results, ought to tell us something. There is no one way to do it, and likely most methods are either wrong for you or either many could work for you. They all can't be perfect.

Going with a slightly small frame will give you more room to adjust things, like seatpost, stem, and saddle position. That's my basic theory. I like a "cab forward" and low handlebar position, so a smaller frame works better for me. YMMV.

Try something and then don't be afraid to change. A good shop will swap out stems, which is especially easy with threadless/open faced (front plate comes off) stems. If not, buy some cheap ones for size, then get a good one in the size that fits.

Remember the whole system works together. You can't really generalize that one adjustment will "make it climb better" and the like. For example, a longer stem alone will move you forward, and you may need to move your saddle forward, too, unless it was too far rear to begin. Being further forward over the crank may or may not work for you for better climbing, depending upon your pedaling style and fitness.

Which brings up something else, things likely will change for you over time, and different things may work for you for different conditions. My setup for a 50 mile road race is not the same as for a 500 mile race. I don't use the same setup now that I had 5 years ago. Lots of stuff like that -- fit is dynamic, in other words.

Don't sweat it too much. Just try some things and see what happens.

Dog