Sloping Top Tube - WSD

[Missy24]

Lets talk sloping tob tube's...

When I went shopping for the Cannondale to replace the scott I did look at a lot of WSD bikes but I started to notice that all the WSD bikes out there have a sloping top tube and I'm not sure why.

Yes Colnago does it with a lot of their bikes as does Bianchi but I'm wondering why and does it have any other benefit other than looking pretty?

Cheers
Row

[Kalgrm]

Lets talk slopping tob tube's...

I really hope you mean "sloping top tubes". Otherwise, things might get uncomfortable in this thread.

[Mulger bill]

Ignoring Graemes attempt at humour... (mainly 'cos he got in first...)

I get the feeling the sloped top tube is an attempt to make a frame with standard 700c wheels fit the standover needs of the shorter rider. Shame most ladies legs are proportionally longer than an equal height males.

Giant was pretty much the first to introduce compact frames on a wide scale and their claim at the time was it led to shorter seatstays for more efficient power transfer, methinks there's a lot of marketing involved but I do like the way they look.

Shaun

[Kalgrm]

A sloping top tube will allow a longer seat post section to project outside the seat tube. In marketing terms, this "provides the benefit of a vertically compliant ride whilst maintaining lateral stiffness".

There is that stand-over height too. A sloping top tube allows shorter people to ride a bike with 700c wheels (regardless of their gender).

Cheers,
Graeme

[Missy24]

Ok

I don't like sloping top tubes ( I will go change this in the subject heading in a mo... bro ) which is why I stopped looking at WSD bikes in the first place, I like straight lines... anyhooooty who... OT

Graeme when you say vertically compliant do you mean a bike with a more relaxed geo that would see the rider sit up more?

Shaun is the shorter seat stay the bar above the chain stay? As in the part that runs from the top tube to the chain stay?

[trailgumby]

Vertically compliant = absorbs road shocks more.

[Missy24]

Vertically compliant = absorbs road shocks more.

oh ok

[Mulger bill]

Seatstay is the tube running from the rear dropout (the hooky things that hold the wheely things in ) to the seattube. The seattube is the bit that runs from the top tube to the chain stay.

Just so's we're all reading the same book...

[Missy24]

Seatstay is the tube running from the rear dropout (the hooky things that hold the wheely things in ) to the seattube. The seattube is the bit that runs from the top tube to the chain stay.

Just so's we're all reading the same book...

Thanks Shaun, I now no all the parts of the frame

[drubie]

I always thought the side benefit was the manufacturer made 3 frame sizes instead of 7 and relied on the seat tube/stem to fill in the differences.

I kinda like the look though - very BMX.

[Kalgrm]

Graeme when you say vertically compliant do you mean a bike with a more relaxed geo that would see the rider sit up more?

I don't say it - that's "marketing speak". You'll see the terms "vertically complaint" and "laterally stiff" in their ads: I was having a dig at them. (I know, call me a cynic if you will ... )

With compact frames (ie those with a sloping top tube) you need to find out the "effective top tube length" to get the right sized frame. Because the top tube slopes, it needs to be a different length to that on a "normal" frame to provide the same rider geometry. The term "effective top tube length" indicates a virtual length for the top tube which brings it into line with a normal frame's measurements. The length of the top tube determines the correct frame size for the rider, rather than the length of the seat tube (which is how frame sizes are indicated. Very confusing ... ).

Cheers,
Graeme

[Nobody]

I once read on the Sheldon site about a frame stiffness test for lateral stiffness. I believe it showed that the frame size has more to do with stiffness than the frame material. But then you could also argue that wheels and tyres play a big part in lateral stiffness.

It is a bit of a stretch to say this, but maybe a compact frame could be laterally stiffer because of its shape in comparison with a horizontal top tube frame.

[Kalgrm]

It is a bit of a stretch to say this, but maybe a compact frame could be laterally stiffer because of its shape in comparison with a horizontal top tube frame.

I don't think that's a stretch at all. I think that's the main "benefit" of compact frames. The frame is effectively a smaller unit so it will be stiffer than the equivalent sized conventional frame, all other things being equal.

It may also be a few grams lighter, but maybe you lose that with the longer seat stem.

Cheers,
Graeme

[ghettro]

Im long torso'd and I have short legs for my height (30" inseam and 5'8") so I nominally ride a 52-54cm top tube sized bike. I have very little clearance on a standard 54cm bike, compacts let me have decent standover height. One downside is that on the smaller comapact frames you typically can't fit a full size water bottle on the seat tube position because the top tube gets in the way.

[toolonglegs]

I always thought the side benefit was the manufacturer made 3 frame sizes instead of 7 and relied on the seat tube/stem to fill in the differences.

I think this is the main reason full stop...fair enough too.
Frame size IMO means little...you have 5 contact points and if they stay the same then the rest makes little difference (with in reason).
Brett Lancaster just rode the TOC on a bike made for Hausler...big difference in height there.Longer post and stem was all that was needed.
I can ride a 57 to a 63 quite happily.

[Nobody]

I always thought the side benefit was the manufacturer made 3 frame sizes instead of 7 and relied on the seat tube/stem to fill in the differences.

I think this is the main reason full stop...fair enough too.
Frame size IMO means little...you have 5 contact points and if they stay the same then the rest makes little difference (with in reason).
Brett Lancaster just rode the TOC on a bike made for Hausler...big difference in height there.Longer post and stem was all that was needed.
I can ride a 57 to a 63 quite happily.

Maybe for racing, but some of the fits you see on racing bikes like the one below would make emergency braking difficult.

http://www.bicycles.net.au/forums/viewt ... 31&t=27283

[toolonglegs]

Nah just a crap photo taken on a too wide a lense...makes it look wrong which it's not.
Yes I am playing devil's advocate a bit...but I do get tired of all these "I test rode it for 10 minutes and just knew it was the right fit for me" posts.
Although this is coming from someone who hasn't test ridden a bike since 1997 .

[mikesbytes]

I just went and looked at all 5 of my bikes and the top tube varies from zero slop to steeply sloping. While the frames look quite different, I don't feel any significant difference that can be related to the top tube slope.

See how the bike feels when you ride and buy the one you like without getting hung up about top tube slope.