Bike Fitment.

This article is also a thread on the forums, you can also visit the forums using the link below to ask questions or see questions asked. Proper Bike Fit (Forums Thread)

Looking for a first bike or new bike or even moving from Brand "X" to Brand "Y", IMO one key fitment procedure is to isolate the TT (top tube) length.

Fitment of the TT is important no matter what style of bike you ride, from road to mountain, from 26" to 29" bikes.

** A lot of conventional thinking was to worry about seat tube height, but that was because in the days of yester most companies used 100% horizontal TT (Top Tubes) which gave less stand over clearance, so by choosing a shorter seat tubed bike, the TT was also mounted lower giving more stand-over clearance.

About TT length:
There are two types of TT lengths, ETT (Effective TopTube) and Standard TT length.
Of the two, the ETT is the most important measurement.

Because of slopping TT's measuring the tube length itself can be decieving when compared to a taking a measurement from a straightline.

How it works:
Measuing up a TT is simply measuring the distance from the center of the ST, to the center of the HT.
That number is your TT size.

But, with many new bikes that have sloping TT's, you need a more accurate measurement to tell you the whole story.

ETT length takes the measure from the center of the ST (seat tube), to the center of the HT (head tube), but is does so using a perfectly level horizontal line. Accurately measuring the straightest distance between the two tubes.

When considering TT lenght, accounting for proper stem length is also important.
This is usually a 100mm stem for most mountian bikes.

Stem length can and will effect how you bike handles. Too long or too short of a stem will slow up or speed up steering as well as add or detract from your weight being centered over certain areas of the bike.

This effects turning, climbing, jumping, descending, and braking.

Example: Your current frame has a 23.5" / 596.9mm / 59.69 CM ETT, and is fitted with a 100mm stem.

If you are using a stem shorter than 100mm, IE a 90mm, consider purchasing a frame with an ETT 10mm less than what you are currently riding. 23.5" / 596.9mm / 59.69 CM ETT - 10mm =23.1" / 586.9mm / 58.69cm

If you are using a stem longer than 100mm, IE a 120mm, consider purchasing a frame with an ETT 10mm more than what you are currently riding. 23.5" / 596.9mm / 59.69 CM ETT + 10mm =23.9" / 606.9mm / 60.69cm

Under normal riding, a stem that is +/- 10mm from the 100mm standard is fine, but if you start moving towards +/- 20mm, you should consider finding a frame or brand closer to your proper size.

Something missed, misinformation, or if you want to add something, feel free to help correct the problem.