Objective: The purpose of this post is to explain whether it is better to have an effective top tube that’s too long than needed or too short.
First, it’s necessary to specify what the effective top tube (ETT) is.
The effective top tube is a line horizontal to the ground that connects the middle of the head tube and another line extended out of the seat tube.
The distance between the middle of the head tube and the intersection point is the length of the effective top tube (image below).
FAQ: What does the effective top tube indicate?
The effective top tube indicates how far the seat tube is from the head tube. This data is critical for determining how the bike will feel when pedaling in a seated position.
If the rider gets out of the saddle, the importance of the effective top tube diminishes and the so-called reach comes into play.
What Happens When The Effective Top Tube Is Too Long?
An excessively long ETT will have the following negative consequences:
- The rider will have to lean forward more to reach the handlebars. The lean will make the position more aerodynamic but will stress the back. Long days could result in persistent back pain.
- More of the rider’s weight will be shifted towards the rear wheel and climbing will be more difficult due to the reduced front wheel traction and the extra mass on the rear end.
- If the length of the top tube is extreme and the seat tube angle is too slack, in some cases, the rider’s knees may get too close to the chest when pedaling.
What Happens When The Effective Top Tube Is Too Short?
If the ETT is too short, we observe the following issues:
- The rider’s legs are too close to the handlebars when pedaling in a seated position. In extreme cases, the knees of the rider may come in contact with the handlebars during slow tight turns.
- The rider’s torso feels somewhat restricted and “cramped”. The position could cause repetitive stress to tender points of the back and cause pain.
- The rider’s back angle is too upright.
- The upright back angle involves more of the quads at the expense of the powerful hip extensors (the glutes). Sometimes the position may result in knee pain due to the increased stress on the quadriceps.
- The rider does not feel comfortable pedaling for long distances.
So, what’s better – an effective top tube that’s too short or too long?
If we’re talking about the ends of the spectrum then neither is acceptable and a new frame should be obtained.
If the size difference between the needed effective top tube and the one available is fairly small, a compromise can be made in either direction.
Why? The stem length and the saddle position affect the effective top tube.
Short stem + sliding the saddle forward = shorter effective top tube
Longer stem + sliding the saddle towards the rear wheel = longer effective top tube
As long as the new stem is not extremely short or long, the adjustments can work.
Keep in mind that MTBs use a short stem because it makes it easier to cover technical terrain and minimizes the lag between the rider’s input and the bars. However, a shorter stem is twitchy when descending at high speeds.
For that reason, road bikes have longer stems. A longer stem makes the handlebars less sensitive to the rider’s input. Thus, a longer stem is safer when going downhill fast.
In other words, if you have a road bike with a very long ETT that requires an extremely short stem, the combination is not recommended because you will lose stability during high-speed descents.
Meanwhile, if you have an MTB with a short ETT and want to elongate it via a very long stem, you will lose some of the bike’s technical abilities.
Most People Prefer Smaller Frames
Most people consider undersizing safer than oversizing. In other words, it’s preferred to have a frame that’s too small for you (within reason) than one that’s obviously too big.
It’s easier to control a smaller bike than a large one. If your bicycle is too big for you, you may experience back, elbow, wrist, and shoulder pain.
It’s also worth mentioning that many pro cyclists are now riding frames that are classified as too small by standard manuals. This is 100% intentional. The goal is to keep the bike agile and aggressive. A comfortable fit is achieved by playing with the position of the saddle and the stem’s length.
Don’t Choose a Bike Without Testing It
If you have the opportunity, avoid buying a bike without sitting on it. It does not matter what the number of the ETT is when you feel uncomfortable on the bike. There are also many other factors that come into play (e.g., reach, seat tube angle, head tube angle…etc.)
The Reach Is Often More Important
Currently, many people choose a bike by first getting a frame with the right reach and then achieving comfort via saddle and stem adjustments. (It’s also possible to get different handlebars if your discipline permits it).
Ultimately, the reach cannot be changed. It comes with the frame and isn’t affected by the saddle position or the stem. If the number is wrong, there isn’t a fix other than getting a new frame.
If you want to learn the differences between the reach and the effective top tube, consider reading the dedicated post on the subject.
Summary: What You Need To Know
- If the effective top tube is extremely short or long for your needs, it’s better to get a new frame/bike.
- If the discrepancy is small in either direction, a different stem and saddle position will help to a certain extent.
- When playing with the stem keep in mind the bike’s purpose. A road bike needs a longer stem; an MTB needs a medium or short stem.
- Ideally, test the bike that you want to purchase or at least ask about it.
- The reach is currently the new measurement used for sizing a frame, although the effective top tube is still important as it reveals how the bike feels during seated pedaling.