why go with sloped top tubes on roadbikes?
 

Hi,

I'm looking at getting a new frame built (first one since I got my Fuso 18 years ago..)

I'm curious as the the value of a sloped TT? I see a lot of quality builders offer it. To me, they look somewhat awkward. I know the standover height issue, and some supposed weight saving, but are they worthwhile. How much weight are you actually saving? A few grams?

Just curious what people think. Those who have sloped TT's, why and would you do it again?

thanks,
Francis
Riding again after 12 years off; in Portland.

Francis

I'm using a Giant TCR Advanced Team, other the the standover height, I find the smaller rear triangle on the compact frame stffer than my previous full size frame. I think the biggest advantage is for the manufacturer as they can get away with less sizes by changing seatposts and stems etc.

+1

Lots of hype but little real world benefits. My dad always used to say "those fancy colored lures catch more fishermen than fish." Those fancy carbon and Ti bikes catch a lot of riders. Unfortunatley, they don't make them better riders.

Tim

no idea what benefits they bring to a ride...what id do know is i dislike the look of a sloping top tube on a road bike.

sloping TT's were functionally introduced to allow crotch clearance on utility bikes and mountain bikes. that's clearly not an issue with a road bike so why have it?

also, logically, wouldn't a sloping top tube add flex to your ride due to the more isolated seat position?

Why? Current fashion.

The sloping top tube makes for a lighter frame, but you will lose most, if not all, of that weight savings with the longer seatpost that is required.

I think that there are two quite different answers to this question. One sounds to me like one has bought into the bike maker's marketing a little too much, the other sounds a bit too cynical for me.

I don't think there is any advantage to a sloped top tube. Some like them and some don't. Personal preference and fit should be the deciding factor.

Better ride maybe
 

One bike fitter says that the sloping tube with the longer seatpost can absorb a lot more road shock/vibration if it is made of Carbon. I guess it is way to make a stiffer and harsher riding frame smoother without compromising performance.

Why use a horizontal top tube?

Sloping top tube frames fit me really awkwardly, due to my proportionally long legs for my overall body height. A lot of the frames I've tried have required seatpost swaps because I need them up so high. Traditional geometry frames (ie. horizontal top tube) fit just fine though, so unless I go custom I'll just stick with them.

I have proportionally shorter legs, so the sloping top tube is perfect for me. I get a safe standover height, yet a long enough cockpit. Isn't choice wonderful?

Great if you have short legs and long body

In a totally non-practical application - I took my horizontal road bike to the skateboard park ... ouch.



Beyond that non-sense, I believe its an economic tactic. 5 frame sizes vs. 8 in traditional sizing to cover for 95% of the population in a normal bell curve = lower manufacturing costs for the same target market.

Here's something, all else being equal (heh, whatever that means!) a sloping top tube bike will tend to be stiffer when out of the saddle but will have more seat post flex when on the saddle.

Standover clearance for riders with short legs/long torsos is one of the best reasons I can think of to have a sloping toptube.

You secretly want to dress up in women's clothes but are too scared to be seen in public so you test the waters by riding something that resembles a girl's bike. If you are already an out of the closet transvestite or a manly-man confident and secure in your heterosexuality then you shouldn't go with half measures and go with a full on mixte like this sweet ride. http://www.rivbike.com/html/bikes_mixte.html

I prefer a sloping TT for one very simple reason that has nothing to do with performance, ride or weight. A sloping TT allows me to clamp my bike in a workstand without moving the seatpost up and changing the saddle height.

I need two things to achieve a decent fit - a 570mm+ TT and a 150-160mmHT. Many bikes using traditional designs use 580-600mm (to top of collar) in order to make those two things work together. Assuming 190mm from the top of the saddle to the top of the clamp, and 760mm from the center of the BB to the top of the saddle, that leaves 570mm of seattube before I run into a problem. While standover in this case is not a problem, it leaves me with about 9cm exposed post. Typical Park shop clamp is 10cm. Adding a slight slope to the design renders the problem moot and I don't have to screw around with setting my saddle height every time I work on the bike.

Whenever I spec a custom, I always spec a small amount of slope. For rack bikes, I simply don't buy one if it's more than 57 CTT.

Aside from this triviality though, I don't see any advantage from the design whatsoever. And, I do think a bit of slope is pretty cool looking. Extreme compacts - no.

I'm not a fan of the sloping top tube. I'm a purist I guess and much prefer the look of a more traditional road bike. I see no advantage to the rider by chosing a bike with a sloping top tube over a bike with traditional geometry.

I can see only two advantages for bike manufacturers and those are a) fewer sizes offered and b) they can claim a lighter frame weight (even though that weight savings on the frame alone will be offset by the longer seatpost on the bike).

That's another thing, I find it increasingly difficult to find a seatpost that is under 300mm in length so now I'm stuck carrying the weight of a longer seat post on my traditional geometry bike.

Here's what Tom Kellogg has to say on the topic:

http://spectrum-cycles.com/616.htm

Have neither, but I do have a straight TT Cannondale Criterium frame that I ride everyday (commuter), and my sloping TT Scott S20. Both bikes fit me fine and I enjoy riding them both!

Fewer sizes fit more riders, more seat post out is more comfortable ride, and they rocket up hills.

interesting:
"Although we were able to measure a slight increase in stiffness, it was too slight to feel. The big change came when I stood to accelerate or climb. As I stood up, the bike appeared to loose three pounds. The inertia of the bike as I rocked it back and fourth was reduced so much that I felt as though I was on a twelve-pound bike. Interestingly, when seated, a compact frame feels exactly like a traditional design. The compact design has no effect on handling beyond the increases responsiveness during climbing and accelerating..."

this alone would make compacts a decided advantage for anyone spending large amounts of time on the upslope. A lot of what happens during climbing is the psyche.
i.e. despite no real weight differences between a few of my bikes, some are decidely better 'climbers' and than others, even though I'm 'positioned' identically and wheels are the same. I've gone so far as to ride the same sections and transfer wheels from one bike to the other, to eliminate as many variables.
... so itz all in my head...:rolleyes:

I'm gonna have to get some serious uphill time on a compact design and see if Tom's comments are obvious.
Personally I have no issues with the 'look', my big concern is always getting proper fit/position. The other consideration is having enough space to fit 2 full size water bottles without running into cramped space. Don;t wanna be fumblin with a bottle in the middle of a pack.

I'll trust Richard Sachs' opinion on this one: There are no performance or weight advantages, so go with what you like to look at.

I seem to recall there was a debate in the framebuilding forum about this. Do a search if you wish.

+1 I'm 5'3" and had a hard time finding road bikes that fit properly. I ended up with the Ruby Pro which has a sloping top tube and the geometry fits really well. I love the bike. Most of what I tried were frames with more traditinal ge0ometry and those also seemed to have to long a TT. With the frame I have now, the sloping TT allows for a shorter reach without having to go to a stubby stem.