Chainstay philosophy?

[mso]

Originally Posted by davids

I've got nothing to add from a technical perspective, but wanted to throw out my experience riding Sevens, Serottas, and a Pegoretti.

Every Serotta I've ridden (Fierte Ti, Legend, Legend ST, Concours, and Nove) climbs better than every Seven I've ridden (Steel Axiom and Alaris.) Sevens are softer/deader. Serottas are responsive and react nearly instantly to the pedal. The Pegoretti Love #3 is a bit better in this regard than the Nove.

These designs all include round stays, but with very different designs. And the Serotta and Peg dropouts seem much more substantial than the Seven dropouts.

Totally opposite experience for me between the Seven Ti Axiom and Ottott. I believe A LOT has to do with ridder weight and riding style.

[atmo]

Originally Posted by Ray

ATMO contends that you'd never feel a difference of 1 cm and I can't argue with him. But my old RB-1 and my '97 Riv were just about identical bikes except the Riv had stays that were about 25 mm longer and I could damn-straight feel the difference there.

-Ray

how?

[RPS]

There is a lot of good information here, but there is also some that IMHO can be misleading. In fairness to Serotta, Moots, Litespeed, and all others who make titanium frames, a technical perspective from a different point of view may be helpful to a few.

Regarding what was implied in the original post, we can’t really “see” how beefy (in a stiffness sense) a chainstay is by observation alone. Diameter is a major part of it, but the wall thickness is also important; and that can’t be observed. A wimpy-looking stay can be stiffer than a larger one – which is the case in some designs – in order to make them stronger or to allow for greater tire clearance. Larger stays are probably stiffer, but there is no guarantee that they actually are.

As stated above by others, titanium is indeed more flexible than steel, but aluminum is even more so and few complain about aluminum chainstays being too flexible. If designers can work with aluminum, they can do the same with titanium. Other than added weight, a titanium tube can be made as stiff as a steel one without increasing diameter. Judging by looks alone can lead to wrong assumptions.

Also as correctly stated by others above, drivetrain loads on the chainstays caused by chain tension are indeed limited to the area between the BBKT and rear axle, so downtube size can’t help the chainstays resist bending due to chain loads. However, many of us lean a bicycle from side to side (some riders more than others) when sprinting and/or climbing, and that action not only places additional loads on the chainstays, but also places the downtube in bending and torsion. That is why a larger and/or ovalized downtube can better resist frame flex under heavy pedaling out of the saddle, which can limit front derailleur rub.

When the wall thickness is held constant, an oval stay can be considerably stiffer in bending even when the minor dimension is equal to that of a round tube. Think of a 2X4 which is a lot more flexible in one direction that the other. Even so, it doesn’t change the fact that it is still twice as stiff in its weakest direction as a 2X2 (albeit at a higher weight). The same kind of logic applies to oval versus round stays (again, when WT is held constant). I don’t have a preference in oval versus round stays; I’m just stating a fact.

Slight bends in stays can affect the stiffness appreciably in tension or compression, but have insignificant affect in bending or torsion. Unless a buyer actually knows which way a stay is loaded, speculating on its effect is pointless. Just ride the bike and see if you like it.

Just a slightly different point of view.

[RPS]

Originally Posted by Tom Kellogg

So ... if you want compliance, actual vertical movement, you need stays that allow the rear dropouts to move vertically. Seat stays which curve to some degree and are made out of a resilient material are the best way to do this, this side of a suspension rear end. This can be done with composite stays, but the degree of flex is quite difficult to control.

Hope I have not thrown too much up on the board.

Great point.

Additionally, significant vertical compliance provided by seatstays or fork is inherently limited by ability to control the wheels in roll.

[Ray]

Originally Posted by atmo

how?

As always, difficult to describe. But under hard pedaling loads, seated or standing, the RB-1 felt a bit more fidgety, a bit more lively, like it had more 'jump'. The Riv, under similar loads, felt more planted, like all of the movement was straight ahead and the bike wasn't wandering as much. The Riv is a tough bike for me to describe because the front end felt very quick and it reacted to steering input very quickly - seemingly as quickly as the RB-1. But the rear felt extremely stable, like it was holding the whole enterprise in line and didn't react to pedaling inputs as noticeably. I was always every bit as fast on the Riv as on the RB-1, but it was a very different feel. Both bikes are gone now, but the combination was always interesting to me because they were so similar except for chainstay length - as close to 'all else being equal' as I could find. the front centers, angles, rake/trail, etc, were basically identical. The BB was slighly lower on the Riv and I know that has some impact on chainstay length, but not 25mm worth.

Just more ramblings of a lunatic,

-Ray

[Too Tall]

Originally Posted by Archibald

gradient butted, optimized shaping, tire clearance, heel clearance, and stiffness. You can have it all.

That's a spicey meatahball Just a word. Wow.

[atmo]

Originally Posted by Ray

As always, difficult to describe. But under hard pedaling loads, seated or standing, the RB-1 felt a bit more fidgety, a bit more lively, like it had more 'jump'. The Riv, under similar loads, felt more planted, like all of the movement was straight ahead and the bike wasn't wandering as much. The Riv is a tough bike for me to describe because the front end felt very quick and it reacted to steering input very quickly - seemingly as quickly as the RB-1. But the rear felt extremely stable, like it was holding the whole enterprise in line and didn't react to pedaling inputs as noticeably. I was always every bit as fast on the Riv as on the RB-1, but it was a very different feel. Both bikes are gone now, but the combination was always interesting to me because they were so similar except for chainstay length - as close to 'all else being equal' as I could find. the front centers, angles, rake/trail, etc, were basically identical. The BB was slighly lower on the Riv and I know that has some impact on chainstay length, but not 25mm worth.

Just more ramblings of a lunatic,

-Ray

it's all good atmo, especially the killer initials. i'm just more
pragmatic i guess. i can't feel shape or guage, or even if the
pipe is heat treated. no matter - it's just me.

[vaxn8r]

Originally Posted by RPS

...Just ride the bike and see if you like it.

Just a slightly different point of view.

That's hard to do with a Serotta or a Seven but....yeah....+1

Knowing nothing about engineering, but just having ridden a bunch of bikes over the last 4 decades, the bike needs to feel balanced and it needs to fit. I also think you can overdesign stiffness resulting in a harsh ride which is fun for a while but not for long.

Originally Posted by mso

Totally opposite experience for me between the Seven Ti Axiom and Ottott. I believe A LOT has to do with ridder weight and riding style.

ditto that. but the thing on custom bikes is that they are all spiced to flavor. it's a bit like going for chinese takeout and asking for spicy at one place and mild at nother and then stating as fact online that the mild place can't make a spicy dish.
kind of drives me crazy.

[Ray]

Originally Posted by atmo

i can't feel shape or guage, or even if the
pipe is heat treated. no matter - it's just me.

I don't believe I could either, but I've always at least imagined that I could feel differences in length to some degree (OK, lets keep it clean here Cuz ). In a lot of cases, the bikes with longer stays were different in so many respects it was hard to know how much of a role the chainstays played in the different feel. But on those two, it was the primary difference (unless I actually WAS feeling changes in shape or guage, which could have also been different) and I could feel a definite difference. Not better or worse, just different.

-RS

[atmo]

Originally Posted by swoop

ditto that. but the thing on custom bikes is that they are all spiced to flavor. it's a bit like going for chinese takeout and asking for spicy at one place and mild at nother and then stating as fact online that the mild place can't make a spicy dish.
kind of drives me crazy.

well if you're crazy, what's that make us atmo?

[atmo]

Originally Posted by Ray

I don't believe I could either, but I've always at least imagined that I could feel differences in length to some degree (OK, lets keep it clean here Cuz ). In a lot of cases, the bikes with longer stays were different in so many respects it was hard to know how much of a role the chainstays played in the different feel. But on those two, it was the primary difference (unless I actually WAS feeling changes in shape or guage, which could have also been different) and I could feel a definite difference. Not better or worse, just different.

-RS

cool atmo.
i think i can tell when i have a spoked-from-a-wheelbuilder
wheel in my bicycle versus a factory (eurus, etc) wheel, and
can feel clinchers versus handmade tubs. when i replace the
chain and cassette, my drivetrain makes leads me to believe
that i have a near-new bicycle. thes examples are the extent
to which i can sense anything rear of the seat tube. if i re-wrap
the 'bars with new tape, get outa' my way atmo.

[edouard]

Originally Posted by atmo

well if you're crazy, what's that make us atmo?

lunatic fringe

[Grant McLean]

Originally Posted by atmo

. these examples are the extent
to which i can sense anything rear of the seat tube. if i re-wrap
the 'bars with new tape, get outa' my way atmo.

http://www.personalitypage.com/INFJ.html


g

[atmo]

Originally Posted by Grant McLean

http://www.personalitypage.com/INFJ.html


g

isfp atmo