Denizen

I am looking at a bike for sale online. It is made from round tube Ti and is listed as a 58cm bike. But the dimensions provided are:

Seat tube is 22 1/2 inches or 57 cm from the center of the Bottom bracket to the top of the seat tube. The top tube is 21 1/2 inches or 55 cm.

Stand over height is 31 1/2 inches or 80cm.

So what is the size of this bike?

Thanks!

Denizen

Lots of looks but no guesses?

chaadster

What do you need to know? What's wrong with just considering it the 58 as listed? What does 'true size' even mean? What's the true size of a Large? What's the true size of a 22.5" ctt seat tube?

Denizen

I measured it against my 58cm Klein and it was a full inch longer in the top tube than the one for sale listed as a 58cm. The Klein is a mid 1980s crit bike, the Ti bike is a classic frame, could that be the diff?.

Blue Belly

Top tube & seat tube make no real difference. The seat tube angle & bb location change all of that. Example... I have a Pinarello which has a 56.5tt & a 57st. I also have a Merckx with a 58.2tt & a 60seattube. The head tube & fork are the same. However the Merckx is considered a smaller frame because the bottom bracket is closer to the head tube(or hub), on a horizontal plane. So, the determination of frame size really comes down to how far from the bottom bracket to the front hub. Because, regardless of any tube dimension or geometry you will set your saddle up in relation to the bottom bracket & ideally the handle bars should be in the visual plane of the front hub, when in the hoods. I don't know why it's standard practice to measure the tube lengths. Especially since they are no longer just straight bars

Denizen

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• It's a Merlin Atreus from 2005 or 2006, the TT does seem to slope down. Here is a new reply from the seller, so what does this mean?:
  
  I remeasured the seat tube - it is 57cm
  
  and I remeasured the top tube - it is 56cm

  
  

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cyclezen

what it's called really doesn't matter, it's what those measurements (and others) mean to you?
and what level of confidence have you in the accuracy of any of the measurements given, and whether they mean anything anyway?
Can you get a Merlin geometry chart for this bike and see where this frame fits in (if you need numbers)?
Or is it handgrenade close on the numbers you know to assume that it'll be workable?
knowing what 'size' it's labeled is mostly a trivia factoid.
one can't be obsessive about 'crap-shoots' - the only thing you can be certain of, is that there is very little to be certain about...
crapshoot = cereal box surprise ( am I dating myself ???)

chaadster

Oh, I think I understand what's going on now...

The seller doesn't know what size the frame is, and the OP doesn't understand the geometry numbers, and only knows about what size frame he/she should ride.

In that case, I think you're looking at Merlin size 57cm. The numbers cited sound awfully close to a 57, and too far off for a 59; I don't think Merlin designated any size 58cm frames in that period, but I could be wrong.

HTH