Vikeonabike
CC Neighbourhood Police Constable
I know one slopes and the other doesn't. But what is the difference..is it just to do with stand over hight? Does one handle better than the other? Or is it purely for looks?
"Gerard Vroomen of Cervelo said:The differences are actually very easy to measure and understand, unfortunately few people in the industry are interested in the actual differences or in testing and rather just make up stuff for their brochure.
The differences between sloping and horizontal are small, but if you use the same tubeset for both frames, the following differences will occur:
1) slightly higher bottom bracker stiffness for the sloping frame
2) slightly higher torsional stiffness for the horizontal toptube frame
3) slightly lighter frame with the sloping toptube
4) slightly lighter seatpost wit the horizontal toptube frame
5) slightly more seatpost compliance with the sloping frame.
issues 3 and 4 are a wash, and for us at Cervelo the choice between sloping and horizontal depends on whatcombination we are looking for out of 1, 2 and 5. For our Alu bikes, which have plenty of bb and torsional stiffness anyway, we go with a sloping toptube (or a dropped toptube on the tri bikes which has the same effect) to get a bit more seatpost compliance.
For the steel frames, this is not necessary and so we can increase the torsional stiffness by keeping the toptube horizontal, especially nice for the twisting and turning on rough roads.
For the new carbon frame, the seatpost compliance wasn't an issue but we did want to get the highest possible bb stiffness, so we opted for a sloping frame.
porkypete said:Interesting .... I even understand most of it but what the <bleep> is "seat post compliance" ????
Certainly on very stiff & harsh aluminium frames the extra give you get from a sloping seat tube is noticeable & for someone like me who can generate a lot of force at the pedal does that by making the BB area stiffer (though this I don't notice)fossyant said:Fashion............