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Trek OCLV Headtube length (54-56cm)(10 posts)

Trek OCLV Headtube length (54-56cm)Coot72
Nov 14, 2002 9:35 PM
Could someone tell me the headtube lengths of the trek OCLV frames? They aren't listed on the trek website, and I have read in the archives that Trek makes short headtubes for a given size. This matters, since I don't want my bars 4 inches below my saddle. Thanks!

Coot
re: Trek OCLV Headtube length (54-56cm)mja
Nov 15, 2002 4:46 AM
You could probably estimate it from the Fausto bike pic above.
I'll get back to you this eveningTrekFurthur
Nov 15, 2002 6:56 AM
I'll measure my 54cm 5900 HT, but I can say that my Merlin Agilis takes 5mm spacers, while my 5900 takes, I think, 17mm; the positions are the same. So, yes, Trek's HT's are shorter.
Sorry it took so longTrekFurthur
Nov 17, 2002 9:06 AM
Okay, HT (minus headset cups) on my 54cm 5900 measures 10.25 cm. I use 32mm of spacers to achieve my ~2.5-3" of drop, and I could care less what the stem police have to say about it; also, as a comparison, my Merlin takes 10mm of spacers to achieve the indentical drop.

To djg, I see where you were going now, but as I use top tube measurements to size my bikes, the HT size as regards saddle drop is immaterial to how/where the top tube is in relation to the rest of the tubeset; when you couple of that with my disregard of what anyone else thinks about how many spacers I need or don't need, maybe you can see why I was confused. Thanks for clarifying, though.
You were confused because I was confusing.djg
Nov 19, 2002 11:36 AM
I'll take the blame on this one.
You should take into account not just the headtube butdjg
Nov 15, 2002 7:09 AM
the overall geometry of the bike (or at least the way they size them). That is, at least as of a year ago, the top tube on a nominal "56" was not 56 cm from the bottom bracket (the top of the seat tube collar was 56 cm from the center of the bb). So however long the head tube, and however far it runs above the top tube, keep in mind where it is that you start to measure.

Sorry I don't have the ht numbers for you.
Do what?TrekFurthur
Nov 15, 2002 11:10 AM
First, the top tube could NEVER be measured from the BB--it doesn't go there. Trek measures the SEATtube from the center of BB shell to top of seattube collar. Secondly, the nominal geometry of my Merlin Agilis is identical to my 5900 (it is, I'll grant, a compact frame--thus, "nominal"), but the headtube is much longer on the Agilis. Finally, there is only one measurement for the headtube, from the bottom race cup to the top race cup.
I don't think the post was that mysterious, but I'll try again.djg
Nov 15, 2002 2:22 PM
I wasn't talking about the length of the top tube somehow measured--circuitously, no doubt--from the bb, but its relative location (or distance from the bb, measured along a particular axis; that is, the seat tube). Perhaps Trek has changed the way they measure, but when I had an OCLV (sold it last year), the nominal size was measured from the center of the bb, along the seat tube, to the top of the seat tube collar. So a "56" had a seat tube that was about 54 cm on the usual c-t measurement, as well as a top tube that was 56 cm long on the usual c-c measurement. Thus far we seem to be in agreement.

So: I said that the top tube itself (measured along the seat tube) is relatively low (given the bb height) for a bike of its nominal size--that's just another way of saying that the seat tube is a bit shorter than you might think, given the number on the size sticker. Who cares? Well, he wants to know about the length of the head tube--which, you are quite correct, is measured from the bottom race cup to the top race cup--not because he's just curious, but because he wants to know if he can get the bars at a certain height without what are--in his view--too many spacers. A longish head tube measurement might do the trick for him, but it might not, because the drop to the top race from the saddle--wherever he puts it is determined not just by the measurement of the head tube but by it's relative location. Start low and see where you end up. Low. Maybe this makes less of a difference than I'm guessing, but I think the basic point makes sense.
Or not.djg
Nov 15, 2002 2:42 PM
I suppose you could measure the other way and ignore the question of seat tube length or standover. If you know the orientation and length of the down tube, you can start at the bottom of the head tube and use the head tube length (and head angle) to figure out what you want to know, ignoring the question where the top tube is (or joins the head tube).
I have no idea what I was thinking. Nothing, probably. Ignore the posts above.djg
Nov 16, 2002 7:41 PM
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