Bottom Bracket on Legend Ti

[Satellite]

Browsing fleeBay when I stumbled on this Legend Ti with an interesting bottom bracket. What is with the machined bottom bracket? I have never seen one and couldn't find any info on Serotta's website.

http://cgi.ebay.com/56cm-Serotta-Legend-Ti-Moots-Litespeed-Titanium-/330563133384?pt=Road_Bikes&hash=item4cf7191fc8

I am NOT affiliated in any way with this auction.

Satellite

[dave thompson]

Looks like it was done post production by someone with a lot of time on their hands.

[Satellite]

I guess someone took his drain hole seriously.

Wouldn’t this kind of machining cause the bottom bracket to lose stiffness?

Satellite

[bicycletricycle]

that would be a real Pain in the a** to set up on the bridgeport

[David Kirk]

That is an odd one. I'd be interested to know when/how that was done. It would be a real challenge to mill that after the fact and seriously doubt it was done that way. It look more like someone did a one-off for a build.

I suppose it could flex more in an academic sense but that area is under very low stress so I doubt one could really measure the difference let alone feel it. I think someone want to drop a very few grams and had some fun.

Dave

[Satellite]

I think someone want to drop a very few grams and had some fun.


And void the life time warranty!

[Black Dog]

That is a target rich environment for stress risers. Weakening the most critical part of the frame to save a few grams is nuts!

[Ken Robb]

Isn't SPAMJOSHUA one of us?

[Dekonick]

Think so :)

[David Kirk]

That is a target rich environment for stress risers. Weakening the most critical part of the frame to save a few grams is nuts!

while I agree it's a silly way to drop very few grams I seriously doubt it will affect the lifespan of the bike at all. The bottom side of the shell does little work which is why so many old school steel bikes had HUGE cut out on the bottom of the shell........without issue as time has proven. If you look at FEA work on the BB you'll see it's one of the least stressed area on the bike. Seems odd I know.

I wouldn't worry about it on this bike but it would be interesting to hear the story about how it was built this way.

Dave

[Dekonick]

Good buy at 1k for 1 1/8 HT with F3 fork, King HS.

Wonder what the geometry is... the SN shows it is a custom...

[Satellite]

Isn't SPAMJOSHUA one of us?
I hope that SPAMJOSHUA will chime in; I was surprised nothing was mentioned in the auction description. There are many photos so the buyer shouldn’t be caught off guard but it still needs to be disclosed. This bike actually fits me, but I would be leery of a home job on the bottom bracket.

Satellite

[rugbysecondrow]

I hope that SPAMJOSHUA will chime in; I was surprised nothing was mentioned in the auction description. There are many photos so the buyer shouldn’t be caught off guard but it still needs to be disclosed. This bike actually fits me, but I would be leery of a home job on the bottom bracket.

Satellite


I am the furthest thing from a machinist, but from what have read on here from Kirk and others, machining titanium is not only hard to do, but requires special tooling etc. It seems this would be a hard home job to accomplish, again, from the sidelines as a layperson

[biker72]

that would be a real Pain in the a** to set up on the bridgeport
I'd really like to see how this was set up on a milling machine.
Why go to all the trouble???

[David Kirk]

I hope that SPAMJOSHUA will chime in; I was surprised nothing was mentioned in the auction description. There are many photos so the buyer shouldn’t be caught off guard but it still needs to be disclosed. This bike actually fits me, but I would be leery of a home job on the bottom bracket.

Satellite

That BB milling wasn't done at home and wasn't done after the frame was built. The BB shell was made that way from the beginning. I could be wrong but I'd be very surprised - very surprised.

dave

[DRZRM]

If you look closely at the 10th image (I'll try to link but I think that ebay images don't link, right?)

http://cgi.ebay.com/ws/eBayISAPI.dll?VISuperSize&item=330563133384 Right.

It looks to me like the weld "bead" (slag?) actually pooled into the machined "slot." So it looks to me (I'm no expert, but I do know how to Mig and Tig an ugly bead) like that was milled before it was welded. Thus it must have come from the builder like that, or the milling would have cut into the bead.

Thoughts? Am I reading that picture wrong?

Edit: Dave Kirk beat me to it, which seems like a good outcome, but no way could that have been done after welding.

[Satellite]

That BB milling wasn't done at home and wasn't done after the frame was built. The BB shell was made that way from the beginning. I could be wrong but I'd be very surprised - very surprised.

daveDave,

I wasn't necessary meaning this was a Home job like done in the Garage with a dremal. Just NOT done in house at the Serotta Factory. Even if this was done at home, it looks like it was executed professionally. But I now see your point-s, I was hung-up on Dave Thompson reply “Looks like it was done post production by someone with a lot of time on their hands.” This was my first logical thought as well.

I am also sure you are right about the bottom bracket flex, especially for my meager power output, I would never notice the difference. I had no intentions of bidding on this rig but with all the interest in this thread, I have now become intrigued and would like to ride it.

Satellite

[David Kirk]

Yeah - setting a frame up to do this milling would require a 5 axis CNC machine and some serious skill. Doing it before it went into the frame is a few key strokes and let the machine run.

I would be surprised if it was a one off in some way (employee bike?) and that's how it was made. I made a lot of odd bikes when I was there because I could.

Dave

[11.4]

Interesting. I got a Legend frame a few years back in that same serial number range and it came from the factory -- without any special requests -- with the same machining.

[David Kirk]

Interesting. I got a Legend frame a few years back in that same serial number range and it came from the factory -- without any special requests -- with the same machining.

I'd say that answers that. I'll bet it was a running change that wasn't kept over time.

dave

[DRZRM]

11.4, always bringing the knowledge.

Thanks man!

[Ahneida Ride]

while I agree it's a silly way to drop very few grams I seriously doubt it will affect the lifespan of the bike at all. The bottom side of the shell does little work which is why so many old school steel bikes had HUGE cut out on the bottom of the shell........without issue as time has proven. If you look at FEA work on the BB you'll see it's one of the least stressed area on the bike. Seems odd I know.

I wouldn't worry about it on this bike but it would be interesting to hear the story about how it was built this way.

Dave

Ah yes FEA ... how about FVA ?

[David Kirk]

Ah yes FEA ... how about FVA ?

Flavorful Vinegar Analysis?

I'm a balsamic man.

Dave

[spamjoshua]

I am the second owner, by way of KGB.

I always assumed this was done by Serotta.

More machining, less weight, certainly a much stiffer, much preferred BB feel than my concours. :)

Joshua

[fogrider]

I have a legend ti that is a little older. 1" headtube, straight chainstays with the same dropouts and the bb has no cutaway. I have always found the bike to be stiff and great handling.