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Sloping Frames ... Are there real advantages for the riders ? Or only for the frame builders ...

by Graz_Lag
Tue, Oct 30, 2018 21:08
8

Hi there,

I am new on this forum, 1st - thanks to the road.cc team for validating my account.

I live in France, so pls. excuse for any mistake in the English grammar ...

Also, pls. excuse me if this topic abt. the advantages (if any ...) of the sloping frames has already been covered somewhere else in this forum ...

1st. I bought my very first "serious" bike back in 1999, it was a Scapin KS-Pro based on the Columbus Nemo steel tubes. The bike was available in 14 sizes, ranging from 490mm to 630mm center-center for the vertical tube, with 10mm increase for each size. Custom-size frames were also available upon request. Frames from many other bike builders from Italy, France, Spain, Belgium were available within that size chart concept. For one rider it was SO easy to find out his size ! The custom-frames were left to the PRO ...

2nd. Then, the Taiwanese-US builders come into the market. The tendency put into the business by the MTB frame designers for the sloping frames also played an important role. To the point, that year after year from 2003 on, the road sloping frames have conquered the market.

3rd. In general, as we face in our purchasing processes, these are available in 5 sizes (from XS thru XL) or 7 (from XXS thru XXL) for the premium brands.

4th. As all of us, I have been changing many road bikes over the past 15-20 years, going into the "uncertainty" process of selecting the proper size thru the short size range of sloping frames. Once at home, the stem or the head tube length were too longs or too shorts, the seat tube angle or the one of the head tube were not giving me full satisfaction ...

I have never sold my Scapin, I only keep it updated with modern parts, the frame is still perfectly matching my morphology as it was back in 1999. I use it for quite long rides of 6 to 8 hrs. with no stress, I feel more tired of "being on a bike" when I come home after 3 hrs. of riding my sloping super-light carbon frame ...

Sloping frame bikes are the best invention for the frame builders, 5 sizes in all (or max 7), easier for them to handle the manufacturing and selling processes ... selling not to the end users, they do not care too much of us as customers, what they want is to fill up their primarily customers with standard frame bikes : the retailers and bike shops.

Advantages on the road for the sloping frames ? I do not feel and not discovered any after 15 years yet ... I would much appreciate to hear your ideas and comments  1

Merci !

      

 

If you're new please join in and if you have questions pop them below and the forum regulars will answer as best we can.

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8 comments

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Graz_Lag | 6 years ago
0 likes

Hey thank you for the feedback's !

What bother me the most abt. the sloping frames is the fact that with these we have lost the control of the very basic process of selecting our proper frame size.
The very simple B Hinault method cannot be applied anymore to a frame with sloping top tube.
(Seat Tube H = 0.88 x leg inseam, which is the value that dictates the most efficient pedaling action)
The frame builders decide the sizes for us !
Yes, longer exposed sections of the seat post allows us to increase the pedaling efficiency.
However, to me, from an engineering point of view, the lengthened seat post gives a weaker overall assembly :

#1 - It generates a bending moment in the seat tube section which clamps the seat post
#2 - Because the seat post can flex more, that induces less confidence to the rider
#3 - Where is the point to shorten the seat tube if after the "cut" you are obliged to add - in the form of the seat post, the same length you have cut away in the frame ?

I rather keep my standard frame with horizontal top tube - but and most of all, the freedom to select my size, thus not depending from the sizes the manufacturers have chosen for me.

It's exactly the same when I buy a shirt at Aldi : for the size M the sleeves are too short, for the L are too long ! But in between them, the M and L, there is nothing !

@ madcarew : Cannondale evo
Cannondale, at least for the SuperSix Evo (which I have had, model 2015, sold 4 months ago) is perhaps the only builder who offers up to 8 sizes with small increase of 1.5/2 cm from one size to the next ... So here we slowly go back to my earlier comments ...

@ Jimmy Ray Will : Na... its primarily about manufacturing efficiencies
I totally agree : let's build only few frame sizes, we gain in manufacturing and selling efficiencies. The gaps can be covered with "the other tubes" (seat post, stem, handlebars ...), which are there exactly to add the sections we have cut away from the frames !  

@ simonmb : Oh, and they're (currently) what the pros ride
Ultimately, the pros ride what their teams give them to ride, and the teams get what the manufacturers give them ...

The history repeats itself : sooner or later, in order to force all of us replacing our actual sloping frames, manufacturers will go back to the original bike frames with horizontal top tube.

Because as @ Daveyraveygravey said : and a horizontal top tube makes a proper bike

The bike sellers will tell us the story that with this new frame design one rider can get higher pedaling efficiency   1

Avatar
fukawitribe replied to Graz_Lag | 6 years ago
2 likes

Graz_Lag wrote:

However, to me, from an engineering point of view, the lengthened seat post gives a weaker overall assembly :

Why ? It trades off strength and rigidity in some areas with flexibility in others. That may or may not be a good idea depending on where and how you do it.

 

Graz_Lag wrote:

#1 - It generates a bending moment in the seat tube section which clamps the seat post

Yes - this may be desirable.

Graz_Lag wrote:

#2 - Because the seat post can flex more, that induces less confidence to the rider

Why ? On what is this opinion based ?

Graz_Lag wrote:

#3 - Where is the point to shorten the seat tube if after the "cut" you are obliged to add - in the form of the seat post, the same length you have cut away in the frame ?

For some of the reasons given to you by the people above. 

Graz_Lag wrote:

I rather keep my standard frame with horizontal top tube - but and most of all, the freedom to select my size, thus not depending from the sizes the manufacturers have chosen for me.

You can - the decision by some manufacturers to use compact frame geometries doesn't effect your choice.

Graz_Lag wrote:

The history repeats itself : sooner or later, in order to force all of us replacing our actual sloping frames, manufacturers will go back to the original bike frames with horizontal top tube.

No-one will be forcing anybody to do anything if history is any guide - you can still buy plenty of frames with horizontal top-tubes and have been able to do so in the 20+ years since compact frames on road bikes where made widely available.

Graz_Lag wrote:

Because as @ Daveyraveygravey said : and a horizontal top tube makes a proper bike

That's just personal opinion - about as far away from fact as you're likely to get but obviously very important to the person choosing the bike. If you just want to say you don't like compact frames then do so and been done with it - you'll find plenty of people on here and elsewhere that will agree with you. That has nothing to do with engineering or frame design though.

Graz_Lag wrote:

The bike sellers will tell us the story that with this new frame design one rider can get higher pedaling efficiency   1

Why would they do that ? I've personally never heard anyone make this claim but as you've made this assertion a couple of times now perhaps i've just missed it - could you please let me know where it comes from ? Thanks.

Avatar
madcarew | 6 years ago
1 like

I've ridden racing bikes for 30+ years now. My current Cannondale evo is the most comfortable thing I've ever ridden. It is light years on the handling and stiffness above the hand built italian Columbus SLX and Reynolds 531 frames I rode 'back in the day'. I'm not sure that the sloping top tube has an awful lot to do with my current bike's handling and comfort, but I can't agree with the OP's contention that sloping tube bikes are less comfortable. Sizing, I think, is much easier nowadays, as instead of a 51/53/55/57 each size now (s/m/l) has a larger fitting range. I think OP's point #4 would have been worse in 'the good old days' if he was buying remotely, because with the current system there's a larger range of seat post and handlebar stem lengths that will get an effective fit.

Avatar
Jimmy Ray Will | 6 years ago
1 like

Na... its primarily about manufacturing efficiencies. 

Mike Burrows brought it to fruition on the road, his vision was only three frame sizes, with different seatposts and adjustable stems (which were incredibly flexible) covering the gaps. 

The whole lateral stiffness, vertical compliance angle was the marketing bumph used to get us all to buy in.

That and because frames weighed a lot more 20 years ago than they do now, a sloping frame used less material, which meant ligher bikes... we all liked lighter bikes back in the day. 

 

Avatar
Judge dreadful | 6 years ago
0 likes

It’s primarily about being able to make the frame stronger, as has been mentioned already. The flexibility in terms of minor fit and comfort settings are useful from a riders point of view too.

Avatar
Daveyraveygravey | 6 years ago
4 likes

I agree with Simon, from an engineering point of view, if you reduce the distance between the joints, the frame should be stronger.  Whether you can feel the difference though is another question!  In addition, the lengthened seat post can flex more which can take some of the bumps and vibrations from the road away from your backside.

I'd argue the aesthetics are wrong; in my eyes a sloping top tube looks cack, and a horizontal top tube makes a proper bike.

Avatar
tugglesthegreat replied to Daveyraveygravey | 6 years ago
0 likes

Daveyraveygravey wrote:

I'd argue the aesthetics are wrong; in my eyes a sloping top tube looks cack, and a horizontal top tube makes a proper bike.

I think the opposite regarding the aesthetics but that is subjective, but my background is MTBs and I think disc brakes are great! 

After saying that I am looking for a frame with less slope for CX so I have more room to get it on my shoulder.    

Avatar
simonmb | 6 years ago
0 likes

"pls. excuse for any mistake in the English grammar"

Don't worry. You'll fit in well here. 

A sloping top tube delivers a tighter main triangle which should be marginally stiffer with all other things being equal. Also, because there's a longer seat-post exposed, it's possible to 'tune' the ride to a greater extent by selecting alternate seat post materials. With slightly less material used, there's a small weight saving. 

Largely though, perhaps, it's about aesthetics.

Oh, and they're (currently) what the pros ride. 

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