The Chainlink

Slopey top tubes

I don't like how slopey top tubes look.  But, I see them everywhere these days.  Why do they exist?  Does anyone actually think they look cool? (I KNOW THATS PROBABLY NOT THE POINT, I'm guessing they have some practical value)  It seems they were not used on the top tubes of the eighties and nineties.  I have four frames of the eighties and all top tubes are parallel to the floor.  So what's the deal with these things yall? 

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Permalink Reply by Vilda on March 28, 2014 at 11:36am

Ryan, great find! That is a pretty bike! And now i can follow Rivendell on Tumblr!

Permalink Reply by Legacy Frameworks on March 28, 2014 at 11:43am

Ahh, gotta love the power of a custom design and hand built frame. I had similar considerations  when building my extra small. 

FYI that frame doesn't have a horizontal top tube (look at the slats in the door). And interestingly (to me), all Riv's bikes have some slope to the top tube.


Ryan Stahlman said:

I am also a fan of the nearly horizontal top tube, hence I ride an 80's era touring bike. Rivendell just posted about a new custom frame they built for a short customer. I really enjoy the creativity and care they put into the frame design that allowed the top tube to remain horizontal.

http://rivbike.tumblr.com/post/80720787036/heres-the-story-of-our-l...

Permalink Reply by Kevin Mulcky on March 28, 2014 at 12:29pm

Riv calls their designs "expanded" geometry vs the industry standard "compact." They're always careful to cater to their rider's needs to jack up the handlebars way past the saddle height. 

Permalink Reply by Tony Adams on March 28, 2014 at 12:54pm

Note that this picture conceals how goofy the jacked up bars look by tossing a scarf or something over it.

That said, I think non-horizontal top tubes (except on mixtes) are an abomination. While the many bumps and scars on the top of my head might suggest otherwise, I am (usually) grateful that I am tall.


Kelvin Mulcky said:

Riv calls their designs "expanded" geometry vs the industry standard "compact." They're always careful to cater to their rider's needs to jack up the handlebars way past the saddle height. 

Permalink Reply by Martin Hazard on March 29, 2014 at 12:43am

I think a major reason for shift here has not been mentioned. While it does pertain to hybrids, but not road bikes directly, the advent of the suspension fork was the biggest reason for the shift to the slopping top tube. Throughout the 80's and early 90's many MB's had a traditional geometry. Once suspension forks began raising the fork height, manufacturers had to slope the top tube to get stand over clearance. Since most mainstream manufacturers were selling almost solely MB's by the late 80's, when they had to go to compact geometry they realized that compact frame idea would allow them to also limit the number of sizes on the road bikes. This was particularly attractive in a shrinking (road bike) market, so of course they went with it. It is still with us today. This particularly sucks for some people like me that are right at the cutoff point for the split between sizes for most compact frames, from almost all large manufacturers. I could bitch-on more, but I will leave the history lesson here.

Permalink Reply by Robert Underwood on March 31, 2014 at 9:30am

ok, so the more I read here, seems like the only real reason is... for companies to save money.  Except for a few exceptions like fork height and people with short legs who need higher handlebar height and don't want to have really long section of stem exposed... and increased frame stiffness.  So, basically, its better to have level, horizontal tubes if you can get a frame sized and built specifically for you... except for the purpose of racing (according to some it seems.  I'm still not sure if that's based on science or just opinion at this point).

Permalink Reply by Gecko on March 31, 2014 at 9:47am

Honestly I could care less if my top tube is horizontal or not.  I ride BMX and mountain bikes in addition to my cyclocross-frame long-distance and commuter bikes and I actually prefer a sloped top tube for a few reasons:

1. better standover clearance

2. less overall weight

3. lower center of gravity

For me, more compact frames have more stable yet also more maneuverable handling characteristics, regardless of the height of the seatpost.  Seatposts are strong and light enough these days that it doesn't really matter how much is sticking out of the frame, as long as you don't go past the minimum insertion point.

Permalink Reply by Skip Montanaro 0mi on March 31, 2014 at 10:20am

No doubt there are valid engineering reasons for sloping top tubes. In bike disciplines like BMX and mountain biking, I'm sure the extra standover height is useful if your foot needs to touch to the ground without injury to other parts of your anatomy, no matter your position on the bike. On the road, it clearly helps specialty framebuilders fit bikes to shorter people.

I think for the majority of the bike marketplace (people in the 52cm-64cm seat tube crowd, riding road or hybrid bikes on the road, regardless of ability or purpose), the overriding reason for a sloping top tube is reduced manufacturing cost and inventory management (and perhaps legal issues). A properly fit road or hybrid bike (that is, you're not a 54cm person trying to ride a 62cm frame) is not going to have standover height problems. I suspect bike fitting is going to be done right at your LBS, but much less likely at Wally World and other cheap bike outlets. The weight savings of a slightly shorter seat tube is going to be minimal, and might evaporate completely when you consider that the top tube is slightly longer, and longer seat posts necessary to provide a wider range of adjustment are going to be heavier. They might even need to be thicker (and thus heavier still), as they are going to be more stressed with all that extra exposed length.

Permalink Reply by Adam Z on March 31, 2014 at 11:26pm

"Mansplain" is my vote for word of the 10's.

Permalink Reply by Zidaane on April 1, 2014 at 12:24am

I just got this on Ebay for a Spring project. 2004 and no slope. I have an Allez from a year later with a crazy angle for a 62CM bike. Front looks like a Mac truck. You can see in the side by side that the Allez has a large forehead. I also have nice 94 Cannondale Crit at 58cm that rides great but feels like I'm on a pony. I do think that with the high bars and with a wide handlebar you do get a ton of upper body leverage on the compact frames when sprinting. They are just slightly awkward for normal riding as they fit longer.

Permalink Reply by Robert Underwood on April 1, 2014 at 10:16am

Here's a bit of info on frame stiffness from the Sheldon Brown site...

http://www.sheldonbrown.com/rinard/rinard_frametest.html

actually has nothing to do with slopey tubes, but rather the other dynamics of a frame that add to or subtract from frame stiffness.  I wanted to see if he would mention slopey tubes but only talks about tube diameter, and diffrences between aluminum, steel and titanium.  the stiffest frame in his testing was an oversized tube aluminum track frame. 

I'm still looking for evidence that slopey tubes add stiffness.  Then and only then will I grant a small amount of validity for their existence.  

Permalink Reply by Kevin Mulcky on April 1, 2014 at 10:25am

Smaller triangles are stronger triangles. Boom. Science. 

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