Results 1 to 7 of 7
  1. #1
    RoadBikeReview Member
    Reputation: donkey's Avatar
    Join Date
    Jun 2005
    Posts
    20

    How to determine top tube length?

    Does anybody know how to determine what your top tube and stem length should be? and, does anyone have an opinion on lemond bikes, I'm thinking of buying a tourmalet. thanks, n.

  2. #2
    Non non normal
    Reputation: bigrider's Avatar
    Join Date
    Jun 2002
    Posts
    9,222
    Best way to find out what you need is to be fitted by a competent bike shop.
    Ask some seasoned road cyclists in your area where to get fitted.

    There are a million bike choices out there and Lemond is a good brand. Just make sure the bike you buy is made for what you want to do, ie. touring, racing, crits, group rides, or riding to the donut shop.
    "There are only two ways to live your life. One is as though nothing is a miracle. The other is as though everything is a miracle." --A. Einstein

  3. #3
    RoadBikeReview Member
    Reputation:
    Join Date
    Jun 2002
    Posts
    54
    www.wrenchscience.com

    This will get you started

  4. #4
    RoadBikeReview Member
    Reputation: Nessism's Avatar
    Join Date
    Feb 2004
    Posts
    1,366
    I think the key to fitting a bike is to assess how a person fits on their current bike and then make appropriate adjustments from there. For example, current bike requires a 90 mm stem, new frame should have a longer top tube; current frame requires too many steerer tube spacers, new frame should have a taller head tube; current frame requires seat to be slammed back on the rails, new frame should have more setback; etc.

    Regarding the origional question, make sure the saddle is properly adjusted relative to the bottom bracket before attempting to judge top tube length. Knee over pedal is a good place to start. After that, see if your knees can hit your elbows when riding in the drops with a medium agressive position (not an all out position where you are trying to get as low as possible).

    Hope this helps.
    Last edited by Nessism; 07-17-2005 at 12:48 PM.

  5. #5
    RoadBikeReview Member
    Reputation: Fredrico's Avatar
    Join Date
    Jun 2002
    Posts
    12,869

    Agree with all Nessism says.

    And, if you get a LeMond, it'll have a long top tube proportionate to size, for plenty of room in the cockpit. LeMond brought back this classic road bike design after years of bikes with short top tubes, short wheelbases, low handlebars, choosing "the smallest frame possible" for zooming around the tight corners in parking lot courses of US criteriums, the market the bike builders sought to address. These bikes were fast and cornered well, but not very comfortable for normal road riding.

    Top tubes on standard diamond frames are about the same as the seat tubes. A 54cm. seat tube would have a 54cm. top tube. That positions the rider's weight about 60% over the rear wheel and 40% over the front, for good fore-aft balance, which is essential to handle the bike well. A sloping top tube bike will obviously have a shorter seat tube, and a slightly longer top tube for the same dimensions, the same seat-handlebar-crank triangle. The above example might be a 52 or 53cm. seat tube and maybe a 54 or 55cm. top tube.

    As a starting point, a standard diamond road frame with horizontal top tube will fit, if it is .65 or .66 of your inseam measurement, crotch to floor distance standing barefoot. The larger number will place the handlebars slightly higher and provide a longer top tube. Handlebar reach can then be fine tuned with stem length, which is conditional on how often you ride, relative fitness and flexibility, and is likely to change over time.

    Typically, overweight newbies start out with an upright position and a short reach. As fitness improves and guts disappear, increases in reach with longer stems becomes desirable: this flattens the back for comfort and less air resistance, and expands the rib cage for more room to breathe. For this reason, my opinion is, better to err on the large size when selecting a frame, if positioning isn't dialed in yet. If the frame is too small, the handlebars will be too low, and a long stem will be required to acheive a comfortable reach, putting too much weight over the front wheel. Overloading the front end makes the bike handle squirrely, especially on descents, and will cause wheel wobble. A large frame is more comfortable, and reach can be dialed in with a shorter stem. We're talking centimeters, though. You should still be able to stand over the top tube.

    Lots of happy LeMond riders around these parts (N.VA). The Tourmalet sounds like a good choice.

  6. #6
    RoadBikeReview Member
    Reputation: donkey's Avatar
    Join Date
    Jun 2005
    Posts
    20
    Thank you for your great advice. As far as my current bike goes, its a mountain bike, and now that I'm shopping for a road bike I'm learning alot about fit and I'm realizing that my moutain bike has never fit like it should; I think its too small. Lower back and hand pain has always plagued me. no matter what angle my seat is at I feel like I'm always slipping foward. I'm not sure how much faith I have in my LBS as far as fitting goes, so I want to learn as much on this subject as poss. Thanks, N.

  7. #7
    RoadBikeReview Member
    Reputation: Fredrico's Avatar
    Join Date
    Jun 2002
    Posts
    12,869

    Great fit program.

    Quote Originally Posted by mondo
    www.wrenchscience.com

    This will get you started
    That's a great way to get some quick answers! Measurements hastily taken with a tape measure inputted to their program, gave my saddle height, frame size and reach spot on, allowing for a small margin of error in my measuring, to what took me about 5 years to dial in through trial and error and lots of research.

    They stick with bar width equal to shoulder width, while many like the bars slightly wider, for enhanced control and a slight gain in comfort around the chest area.

    They also compute frame size on inseam, then dial in reach based on floor to sternum (chest bone) measurement and arm length. I end up with a pretty long reach, which would require either a top tube about 1 cm. longer than standard, or a long stem. I'm actually riding a bike in their recommended size, but have a long stem on it to accomodate my long upper body, and have to scoot back on the saddle when descending sometimes, to take weight off the front wheel. They give a total reach figure, stem plus top tube. So it would be easy to figure what top tube length would leave a reasonable stem length, somewhere between 10 and 12 cm.

    This program will give you a great starting point at any rate, a frame big enough to place the bars high enough for good weight distribution and all day comfort, as well as being within the right dimensions from which you can fine tune.

Similar Threads

  1. Felt Internal routed top tube brake cable???
    By CoachRob in forum Components, Wrenching
    Replies: 6
    Last Post: 12-30-2004, 09:32 AM
  2. Frame height vs. top tube length -- which is more important?
    By wilburpan in forum General Cycling Discussion
    Replies: 18
    Last Post: 07-22-2004, 08:04 AM
  3. Frame stiffness?
    By JAM66 in forum General Cycling Discussion
    Replies: 42
    Last Post: 06-09-2004, 10:13 PM
  4. campy cable housing with top tube routing
    By jnichols959 in forum Cyclocross
    Replies: 3
    Last Post: 05-01-2004, 05:12 PM
  5. relation between top tube length vs. stem length
    By NoMSG in forum General Cycling Discussion
    Replies: 1
    Last Post: 03-20-2004, 04:29 PM

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •  

Sea Otter Classic

Hot Deals

Contest


Latest RoadBike Articles


Latest Videos

RoadbikeReview on Facebook