advantages the sloping toptube

stabu

I wanted to pose a question to people who have ridden straight and sloping top tube bicycles.

I myself, have not been an MTB fan (where sloping top tubes are common) and have always ridden a straight top tube. I always thought (somehow) that sloping toptube would be slower.

But is that really true? Are they really only for MTBs?

My impression was that they allow your field of vision to include more of the terrain (and so improve control), at the expense of a less (speed) aggressive posture.

But does it honestly make all that much of a difference?

Morgan

How does the top tube affect your field of vision?

You can have the exact same position on the bike (saddle, bars, pedals) with a flat or sloping top-tube. Makes no difference.

One reason for sloping it to reduce weight - the frame might have a bit less metal in it. It may also be stiffer if the seatstays are shorter - all down to the particular design of course? Aesthetics come into it too.

The reason mtbs have sloping top tubes is to give greater standover clearance.

Morgan

Morgan wrote: »

How does the top tube affect your field of vision?

Oh, I think I get what you're saying. Sloping top tube = higher front end?

That's not really how it works though - the front of the bike is the same height - the top tube is just lower at the back (seat tube).

Lumen

I sought the answer to this question when buying my bike.

A triathlete friend of mine told me "sloping top tubes are for girls and look sh*te".

In search of more profound answers, I consulted the interweb...

Since the "sloping or not" consideration is just one factor in the complete bike geometry, a mfr may achieve a given design goal using either top tube configuration. So it's not safe to assume that a sloping tt may give a particular type of ride.

Apparently mfrs like them because they can produce fewer frame sizes, particularly important for carbon frames.

stabu

"sloping top tubes are for girls and look sh*te".

there were no guys with sloping toptube bikes around when he said that, I guess. Or there were, and everybody was in slagging off mood.

It's kind of the ballet-dancing-is-girly argument. Nevertheless, there is some truth to it. The sloping toptube shape does recall the traditional female bicycle geometry. That's the psychological, asthetic side to it, which I'm not so interested in.

I'm wanted to think functionally about it. Morgan, as I never owned a sloping toptube bike, I was just guessing at some of the possible functional advantages. I'm quite uninformed about that field of vision feature.

Cheers.

Itsfixed

The fact that sloping top tubes are more common is a reflection of the huge influence that mountain bikes have had on general road bike design.

I think among the advantages are that they make the bike feel more agile (because the frame is essentially smaller), and more comfortable, because more seat post that is showing, the more 'give' it has, which means better shock absorption. I think.

But the other truism is that it allows manufacturers to make fewer frame sizes as one frame size can fit a wide range of people because the seatposts are much longer, plus you can also shorten or lengthen the stem. Therefore reducing their design and manufacturing costs.

I have both a sloping and a level top tube bike and there is quite a difference. I couldn't really say why though.

blorg

Most of my bikes now have sloping top-tubes, ranging from very slightly to reasonably pronounced. But I also had two Trek road bikes before that had flat top tubes. I can't say that I would have thought it makes much of a difference to the bike fit or performance, the contact points are all in the same place relative to each other whether sloping or flat. There are too many other variations between the bikes to make any analysis based on the top tube angle.

My view- don't let it effect your decision either way.

BostonB

Level looks better IMO.