Road Bike, Cycling Forums banner
1 - 12 of 12 Posts

·
Registered
Joined
·
289 Posts
Discussion Starter · #1 ·
How do I figure what size top tube I need. Can somebody please give me a simple way of doing this.:mad2:
 

·
Banned forever.....or not
Joined
·
24,427 Posts
Experience.
The longer you ride, the more flexible you get. The more flexible you get, the lower you are able to ride. The lower you can ride, the longer your top tube needs to be.
 

·
Registered
Joined
·
398 Posts
The more experience you get, the more knowledge you have about your riding style and needs. The more knowledge you have, the more obsessed you get with finding the "just right" fit, which can lead to going to a full custom set up! There's more to a bike than just a top tube...
 

·
Sharkey
Joined
·
68 Posts
grumpy is right

Grumpy is right, there is no exact formula . . . and in fact, it is a sliding scale depending on your flexibility and how long you've been riding.

For whatever it's worth: I personally like a fairly long top tube and a somewhat stretched out position. Therefore, when I set up the reach on my bike(s), I rest my hands on the top of the hoods, then lower my body until my forearms are parallel to the ground. My back is somewhat flat in this position. When my tt/stem length is right, my knees fall about 2 cm behind my elbows at their closest contact point.
 

·
Registered
Joined
·
2,633 Posts
MR_GRUMPY said:
Experience.
The longer you ride, the more flexible you get. The more flexible you get, the lower you are able to ride. The lower you can ride, the longer your top tube needs to be.
Until aging takes over. Then you gradually get less flexible, can't ride low for as long as you used to, and have to buy shorter stems or move your brake hoods closer.

I trust experience and comfort more than formulas for bike measurements. The formulas should get you close enough to adjust by changing a stem, so figure on a medium length stem, plug your measurements into a few formulas, and see what comes out.
 

·
Registered
Joined
·
5,830 Posts
On-line calculators should get you in the ballpark, but a fitting is your best option. Even then, you will probably need to do some tweaking over time. A few things to keep in mind:

- Steeper seat tube angles (eg, higher than 73) effectively lengthen your top tube.
- Slacker seat tube angles (eg, less than 73) effectively shorten your top tube.
- Raising your handlebars will shorten your reach, or effective top tube length.
- Lowering your handlebars will lengthen your reach, or effective top tube.
- Reach can be tweaked, within reason, with longer or shorter stems (or handlebars).

To give you a real-life example, my Eddy Merckx with a 57 cm top tube and 72.5 seat tube angle fits nearly identical across the top as my De Bernardi with a 56 cm top tube and 74 seat tube angle, with both bikes using the same handlebar and stem length.

Not sure if I agree with Grumpy about cyclists going for longer top tubes as they ride more. That may be true for younger cyclists, but many older cyclists (50 and up) have the opposite experience as their bodies get less flexible with age.
 

·
Banned forever.....or not
Joined
·
24,427 Posts
"Until aging takes over. Then you gradually get less flexible, can't ride low for as long as you used to, and have to buy shorter stems or move your brake hoods closer."

Ha!
You mean if you allow aging to take over. As you get older, the old saying "use it or lose it" applies even more. I'm more flexable now, than I was when I started riding, 27 years ago. (and I can honestly say that I am now older than dirt)
 

·
Registered
Joined
·
301 Posts
I'm an older rider and have found that since I lost 40+ lbs that I prefer a longer top tube and lower position than before. I got that old tummy outa the way.
 

·
Registered
Joined
·
2,633 Posts
MR_GRUMPY said:
"Until aging takes over. Then you gradually get less flexible, can't ride low for as long as you used to, and have to buy shorter stems or move your brake hoods closer."

Ha!
You mean if you allow aging to take over. As you get older, the old saying "use it or lose it" applies even more. I'm more flexable now, than I was when I started riding, 27 years ago. (and I can honestly say that I am now older than dirt)
Fair enough. At 60 I still got the big plates on the bar in the gym, run at least one marathon every year, and do lots of riding. Takes enough time and effort that I've kinda slacked on the flexibility stuff that I find deadly boring and unfulfilling. Guess I named my own poison.
 
1 - 12 of 12 Posts
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top