Fastback seat stays - Why?

[Moosedryvr]

I recently purchased an older, lugged, Serotta that has fastback seat stays (attached at the seat post bolt). I know of very few other bikes that still use this design (I know that Dave Kirk does on his Terraplanes for one example). Is there an advantage/disadvantage from a design/framebuilding perspective with this design vs. the more traditional "seat tube wrap" design? I guess that the fastback style would make a slightly steeper seat stay angle than other designs. Is there a purpose to this, or is it simply a by-product of the design? Many thanks in advance for any insight on this rather esoteric subject.

Shawn G

[dave thompson]

I recently purchased an older, lugged, Serotta that has fastback seat stays (attached at the seat post bolt). I know of very few other bikes that still use this design (I know that Dave Kirk does on his Terraplanes for one example). Is there an advantage/disadvantage from a design/framebuilding perspective with this design vs. the more traditional "seat tube wrap" design? I guess that the fastback style would make a slightly steeper seat stay angle than other designs. Is there a purpose to this, or is it simply a by-product of the design? Many thanks in advance for any insight on this rather esoteric subject.

Shawn G
Looking at my Atlanta with the fastback style of seat stays. it appears to me just to be either an aesthic consideration or an ease of manufacture consideration. I don't see another pupose.

[Bill Bove]

It looks cool.

[David Kirk]

I've always liked the fastback because the joint between the stays and the lug is in compression and not it shear like a side tack set up.

That and it looks cool.

Dave

[Samster]

and why is it called "fastback" i wonder...

[dave thompson]

I've always liked the fastback because the joint between the stays and the lug is in compression and not it shear like a side tack set up.

That and it looks cool.

Dave
Mmmmm, compression! Drool..........

[avalonracing]

and why is it called "fastback" i wonder...

Cause it sounds cooler than "seat pinchy thing"

[michael white]

I've had, I don't know, a few bikes with fastback clusters. Cino Cinelli is credited with inventing it, back in the 50's I believe. The Cinelli SC seat cluster is a cast lug with a rather overcomplicated seatbolt. It was once touted as an "aero" advantage, because it narrowed the bike's frontal profile, a claim which seems rather quaint now. Other famous fastback clusters with integrated seatbolts were made by Americans such as Eisentraut, Ritchey, Stout, match bicycle, and obviously, Kirk. All are slightly different and personal interpretations. If it's done right, it's elegant, very strong, and perhaps a few grams lighter. There was a tiime when lugged bikes were all anyone rode, so these minor differences in a cluster or fork crown seemed like a huge deal. Now, not so much. Sidetack clusters have made a comeback, it seems, probably on aesthetic grounds. I remember when the fastbacks were cool and the sidetacks were old hat. Whatever; it works for you or it doesn't.

[michael white]

oh, and "fastback" is an aero thing. Plymouth Barracuda! Can't you just feel those sidetack stays slowing you down??????

[jthurow]

Ok, this is a perfect time to ask something that I've wondered about for a while. I've seen two different types of seat stay joint labled as fastback.
Would you call this a fastback?
http://www.torelli.com/images/Mondonico/Foco_sm.jpg
How 'bout this?
http://www.torelli.com/images/Mondonico/diamond-sm.jpg
I'd say no to the red one and yeah to the orange but according to Mondonico, I'd be wrong. What say you kids?

jimi

[michael white]

both fastback, lower one with integrated binder.

[Moosedryvr]

My sincere thanks to all who replied!

Shawn G

[cpg]

both fastback, lower one with integrated binder.

I agree both are fastback but I wouldn't call the lower one an integrated bider though. The integrated style is where the seat stays attach to the seat tube and the binder goes through the seat stays. In the lower picture the seat stays attach to the binder and the bolt goes through the binder not the stays. Probably just sounds like semantics but they really are a different beast.

Curt

[Vancouverdave]

Looks good, is practical on bikes that aren't being designed for max tire clearance, may be stronger (re Dave Kirk, above) and lighter (seatstay top plugs aren't made of air.) And Serotta's execution, especially on the last few years' worth of CSI looks dang cool!

[musgravecycles]

Looks good, is practical on bikes that aren't being designed for max tire clearance, may be stronger (re Dave Kirk, above) and lighter (seatstay top plugs aren't made of air.) And Serotta's execution, especially on the last few years' worth of CSI looks dang cool!

It's not stronger, it's actually the 'weakest' way to attach 'em. When destructive tests have been done this method always fails first. However none of the methods should fail under normal circumstances if done properly.

Personally I dig it, and have built a bunch of frames that way, though as of late I've been doing semi-wrap with my own flutes (top-eyes are for wimps)...

:banana:

[Ti Designs]

The fastback with the added bib on the seat lug is known as the Brampton fastback - not that I know beans about frame history... The more modern fastback design of joining the seat stays to the binder is along the lines of many modern dropouts which solve the problems of needing different angles for different sized bikes. If you're attaching to the side of the tube you need to miter the end to match the angle. If you're attaching to the radious of a circle you miter the tube to match the radious and you're done. Small frames attach near the back, large frames attach lower on the radius. Bolt-in carbon seat stays use the same trick at the other end...

[michael white]

I agree both are fastback but I wouldn't call the lower one an integrated bider though. The integrated style is where the seat stays attach to the seat tube and the binder goes through the seat stays. In the lower picture the seat stays attach to the binder and the bolt goes through the binder not the stays. Probably just sounds like semantics but they really are a different beast.

Curt

yeah, I have one like that, the bolt thru the stays, on my Paramount which you probably made, so you can call it whatever the **** you want. :)