Educate me on sloping top tubes - or is it just marketing hype?

[veggieburger]

All of my bikes are traditional horizontal top tubes, except one. It has quite a dramatic slope from steerer to seat tube, and that seems to be the norm nowadays. Consequently, I run a longer seatpost to achieve the same sizing as my other bikes. Go into a bike shop and you'll be told about the greater stand-over, reduced weight, added stiffness and so on and so forth. But is this real? Are there advantages to compact frame geometry? My suspicion is it has more to do with reducing the number of sizes that have to be manufactured, but maybe I'm wrong.

[FlashUNC]

Totally reducing the number of sizes at manufacture.

[duff_duffy]

I personally like the way sloping tube looks and as I get older don’t mind that it’s a bit easier to get leg over top tube. How it rides depends on so many other factors (tubing, tires, post, saddle) that I don’t think it matters in this department. I think it is also easier to have fewer frame sizes thus making easier to sell. Add all those factors up and sloping top tubes are a win win in my book.

[mcteague]

Many custom frames employ a sloping TT to get the bars where they need to be and still allow good stand over clearance.

Tim

[Bentley]

I kind of like the shorter seat tube, gives me space to mount a rear camera, rear flashing light that is more difficult on a level top tube bike.

Honestly, I first saw them on the Giants and I was not a fan, now it seems much more common.

Ray

[sparky33]

Agreed. I like that the sloping tt exposes enough seatpost so I can fit a blinky under my saddle pack. Can't do that on a level tt with my saddle height.

[paredown]

Thre's lots of folks around here that know way more than me, but I have a story.

I was skeptical of non-level top tubes--didn't look right, manufacturers just trying to save money etc, etc--until I was in Roberts (UK--as in Chas) helping a friend get fitted for a custom frame.

Sloping top tubes came up; I expressed my geezer-motivated disdain for things new--and then had a good conversation with the young frame-maker doing the fitting.

The short paraphrase--when lugs ruled, tubes had to connect in certain ways, unless you filet brazed. so it turns out that the level top tube was kind of a historical accident, not a natural kind.

Tig then gave you the option to do things differently. Once that is one the table, then you can really think about what you want the bike to do, or be best at, or to fit in a certain way-- What he appreciated was that he could now build frames with taller head tubes (tourists, old gents etc), drop the top tube to give good standover--and end up with a wonderful frame.

I own only one frame with a sloping top tube--but I have dropped my prejudice--or perhaps to say it better, I realize that my prejudice is mainly an aesthetic judgement and in this (as in most things) de gustibus non est disputandum.

[pdmtong]

anyone who mountain bikes doesn't see a sloping TT, they see a bike.

slope is an aesthetic but also reduces mfg inventory and to some extent material

[gary_a_gooner]

I personally like the way sloping tube looks and as I get older don’t mind that it’s a bit easier to get leg over top tube.

Wait...when do you have to get your leg over your TT? Isn't getting your leg over the saddle the highest you have to go? You can also mount going over the handlebars, too, I guess.

[oldpotatoe]

All of my bikes are traditional horizontal top tubes, except one. It has quite a dramatic slope from steerer to seat tube, and that seems to be the norm nowadays. Consequently, I run a longer seatpost to achieve the same sizing as my other bikes. Go into a bike shop and you'll be told about the greater stand-over, reduced weight, added stiffness and so on and so forth. But is this real? Are there advantages to compact frame geometry? My suspicion is it has more to do with reducing the number of sizes that have to be manufactured, but maybe I'm wrong.

If, for fitting issues, you need a certain length head tube and when compared to standover requirements, the result 'may' be a sloping top tube..but for performance, no advantage. Also Giant(I think) started the slopping top tube gig in order to make fewer sizes(S/M/L/XL tye gig) saying that a 'size fit more people so every cm/2cm not required but like threadeless, initilly a way to save $.

[FlashUNC]

http://inrng.com/2012/05/the-ancestor-of-your-bike/

[duff_duffy]

I’m crazy when I ride:). That’s me posting a few of my old freestyle bikes, I still do some tricks on my road bike and lower top tube helps:)

Wait...when do you have to get your leg over your TT? Isn't getting your leg over the saddle the highest you have to go? You can also mount going over the handlebars, too, I guess.

[juanj]

Another element to consider with the sloping top tube is that by requiring a longer seat post, the design adds compliance to the frame. When I was having a custom bike built for me some years ago, the two builders I was considering explained that that they preferred sloping top tube (at least in my size frame) so there is room for a longer seat post and added comfort.

[Mikej]

Paging 1999, your thread is back...just kidding. Heck back then even mtb bikes had level top tubes. Now it’s just the norm. I prefer a sloper- the frames started getting pretty stiff and I appreciate the extra seat post suspension. I think giant pioneered the S M L sloper size plan to reduce the amount of sizes. Realistically it has contributed immensely to the popularity of cycling today, giving less agile persons more stability and safety over a level top tube. I remember wondering why Kent had a 1.5 degrees slope on a 98 moots vamoots- now I know - Cuz it’s sexy baby, yeah!

[tommyrod74]

Totally reducing the number of sizes at manufacture.

This, but I also think (on some frames) more exposed seatpost (especially if 27.2 or 25.4 diameter) smooths the ride a bit.

ETA: next time I'll read all the replies before chiming in ;)

[93KgBike]

All the relevant truths are already in this thread. Well done PL!

[tv_vt]

Read this blog entry by Tom Kellogg for another data point...

https://www.spectrum-cycles.com/geometry.php#compact

[sparky33]

anyone who mountain bikes doesn't see a sloping TT, they see a bike.




Form follows function.

[Mikej]

All the relevant truths are already in this thread. Well done PL!

Ill show you how to beat a dead horse...20 years later

[wallymann]

how does this work?

for me, top-tube height is irrelevant within "normal" limits. i swing my leg over the saddle from the back or handlebars from the front, both are much higher than any top-tube will ever be...so you actually step over the top-tube?

...it’s a bit easier to get leg over top tube...

[kingpin75s]

All of my bikes are traditional horizontal top tubes, except one. It has quite a dramatic slope from steerer to seat tube, and that seems to be the norm nowadays. Consequently, I run a longer seatpost to achieve the same sizing as my other bikes. Go into a bike shop and you'll be told about the greater stand-over, reduced weight, added stiffness and so on and so forth. But is this real? Are there advantages to compact frame geometry? My suspicion is it has more to do with reducing the number of sizes that have to be manufactured, but maybe I'm wrong.

IMHO you were spot on with reduced weight and added stiffness. At least for why the concept was originally developed. That said, ideas do propagate for many reasons.

It is my understanding the sloping TT goes back to Charlie Cuningham's CC Proto in 78/79':

"with a dramatically sloping top tube to save weight and add stiffness"

https://www.pinkbike.com/news/charlie-now-that-was-a-bike-charlie-cunninghams-prophetic-cc-proto.html

Always a big CC fanboy, so sloping TT and straight posts have always looked right to me.

[DfCas]

Also in a sloping frame the seatstays are less vertical which allows for more compliance.

I like the longer seatpost to clamp the seatpost in a repair stand, compliance of a longer post also.

[ntkt10]

All of my bikes are traditional horizontal top tubes, except one. It has quite a dramatic slope from steerer to seat tube, and that seems to be the norm nowadays. Consequently, I run a longer seatpost to achieve the same sizing as my other bikes. Go into a bike shop and you'll be told about the greater stand-over, reduced weight, added stiffness and so on and so forth. But is this real? Are there advantages to compact frame geometry? My suspicion is it has more to do with reducing the number of sizes that have to be manufactured, but maybe I'm wrong.

You're correct. Some people like to see 12 inches of seatpost sticking out of the frame instead of 3 inches.

[Bonesbrigade]

Sloping toptubes are way more aero and comfy for super tucks! :D

[macaroon]

Nothing looks worse than a level top tube without a -17 stem; it's sacrilege.

I like the look of the super compact frames English build.

[palincss]

I personally like the way sloping tube looks and as I get older don’t mind that it’s a bit easier to get leg over top tube.

Maybe we get on and off very differently, but I really don't see where the typical sloper top tube helps you get on and off at all. You still have to swing your leg over the saddle and the back wheel, not over the top tube at all. It takes a very very low top tube -- like on a mixte or an Alex Moulton, much lower than the typical sloping top tube -- to be able to raise your foot straight up and step through the frame.

[Jaybee]

I have a friend, not a serious rider, who mounts the bike by standing on the NDS pedal, scooter style push starting, and then swinging his leg over. Every dismount is cyclocross style.

[Butch]

When threadless headsets came out steer tubes were steel or ti so you could stack the same as a quill stem with a threaded headset. With carbon steerers the max stack height is limited. Headtube lengths have gotten pretty long in the past few years in order to fit most riders better. When we designed stock bikes with sloping top tubes it allows a customer to be more likely to dial in top tube length without having to go to custom in order to have standover. This is assuming there are many stock sizes to chose from. Balancing aesthetics and function is always a challenge, it is handy people are used to seeing long seatposts.

[Tickdoc]

I like the look of level top tubes, I only have one bike now with a sloping top tube and come to think about it, I don't ride that one;~)

It's purely aesthetic for me....total agreement on the -17 stems too:)

[dancinkozmo]

sloping toptubes on roadbikes (and those damn stickers on all our fruit) are the work of Al Qaeda .

https://us-east-1.tchyn.io/snopes-production/uploads/2015/10/fruit-stickers-edible.png?resize=675,441

[gary_a_gooner]

You're correct. Some people like to see 12 inches of seatpost sticking out of the frame instead of 3 inches.

I prefer the average amount of seatpost--about 6 inches. :rolleyes:

[Mark McM]

how does this work?

for me, top-tube height is irrelevant within "normal" limits. i swing my leg over the saddle from the back or handlebars from the front, both are much higher than any top-tube will ever be...so you actually step over the top-tube?

For most of the people here, top tube slope has no affect on the ability to mount/dismount a bike*. But if you look at less experienced and/or more casual cyclists, you'll see that a common way to mount is to first swing their leg over the saddle and straddle the top tube with both feet flat on the ground, and then step on a pedal and push off, before rising up to sit on the saddle. A little extra room to play with while straddling the bike can make this mounting style easier.

*The exception is cyclocross racers, who generally prefer a more "traditional" horizontal top tube, which makes it easier to pickup and shoulder a bike while running.

[Mark McM]

Also in a sloping frame the seatstays are less vertical which allows for more compliance.

While that is true, it is not because the rear triangle flexes more. The frame and rear triangle is essentially a truss, and has very little vertical flex. Even making the rear seat stays less vertical won't add any significant compliance. In contrast, the seat post is a cantilevered bending beam, and can have significant amount of flex. Lowering the seat stay/seat tube junction makes the seat post longer, increasing the flex even more (cantilever beam flex increases with the cube of length).

[OtayBW]

Read this blog entry by Tom Kellogg for another data point...

https://www.spectrum-cycles.com/geometry.php#compact
Yep.

With that now off my chest, I'll follow up by saying that I like the traditional (level TT) look best...

[pobrien]

And I will pay more attention to the classifieds to scoop up orphan Colnagos with a horizontal top tube. Size 59 particularly.

[pdmtong]

When threadless headsets came out steer tubes were steel or ti so you could stack the same as a quill stem with a threaded headset. With carbon steerers the max stack height is limited. Headtube lengths have gotten pretty long in the past few years in order to fit most riders better. When we designed stock bikes with sloping top tubes it allows a customer to be more likely to dial in top tube length without having to go to custom in order to have standover. This is assuming there are many stock sizes to chose from. Balancing aesthetics and function is always a challenge, it is handy people are used to seeing long seatposts.

this is very insightful and obvious once considered.

you can also see the benefit of slope when it comes to the smaller frame sizes.

slope allowed my then 10yo daughter to be on a 44cm specialized dolce with 700c wheels

[Ken Robb]

I have a friend, not a serious rider, who mounts the bike by standing on the NDS pedal, scooter style push starting, and then swinging his leg over. Every dismount is cyclocross style.
When I was a kid we all used this technique because we were all riding full-size bikes with 26" balloon tires and none of us had any clearance at the top tube. In fact we didn't push off, we got the pedal at the 11 o'clock position, stepped on it to get the bike moving and swung our other leg over the saddle and rode off. To dismount we stood on one pedal as we slowed and swung the other leg over the saddle to the same side BEFORE we stopped to prevent banging our privates on the top tube. I had a Schwinn Traveler with caliper brakes which was better for this than a bike with just a coaster brake for obvious reasons. :-)

[oldpotatoe]

I prefer the average amount of seatpost--about 6 inches. :rolleyes:

a 'fist'...any less and the frames too big(paging weisan-'pal'...)..:eek:

[SPOKE]

Sloping yet on a road bike is ok as long as it’s less than 4 degrees. Any more than that just ruins the look IMO.