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extended head tubes?(12 posts)

extended head tubes?jaybird
Mar 13, 2002 6:24 AM
what is accomplished by an extended head tube other than reducing stack height or increasing the height of the handlebars? Given that you can still get the correct top tube length Does it allow you fudge the standover height guideline of 1 inch a little more? Is that even the guideline anymore? I am most interested in input on traditional style frames not the compact geometry.

Grassyass,
J.
Zinn is the expert on this matter,,,Pedal Jockey
Mar 13, 2002 6:34 AM
I believe he developed the idea of extending the headtube to allow, especially taller riders, a more upright position on the bike. It makes a sense, because the head tube provides more structural support for the steerer tube of the fork, which is somewhat compromised when spacers are used.

Check out Zinn's website for more information, but this is what he says about it in his "Project Big" description:

"On road frames, the seat tube is shortened, and the top tube is lowered to stiffen the main triangle. The reinforced head tube has extra extension above the top tube to maintain sufficient handlebar stem height. An oversized (29.8mm) seatpost delivers abundant rigidity with the shorter seat tube."

http://www.zinncycles.com/

PJ
re: extended head tubes?madstork
Mar 13, 2002 6:44 AM
I think you've covered the reasons. My custom frame has a level top tube that is dropped 3cm from a "normal" position, similar to what Colnago does on its largest frames. So I basically have an extended head tube and seat tube. I ride a big frame and I think the extension is a good idea for getting the bars high enough if that is what the rider needs. Better than spacers or riser stems? I don't know about that.

I like the lower top tube for the extra standover height, as well as the feel of having a smaller frame beneath me on corners and descents.
re: extended head tubes?bianchi
Mar 13, 2002 6:53 AM
One of the main benefits from extended head tubes results from the use of threadless stems/forks on most new bikes. With threadless systems, the only ways to raise the handlebars are to use lots of spacers and/or a riser stem. An extended headtube allows you to raise your bars higher without all the spacers -- which can be a real issue with all-carbon forks. Some might also prefer the appearance. With threaded (or quill) stems, all you had to do was raise them up or down to adjust handlebar height. If your prefer higher bars, it still has a nice clean appearance with a quill stem. With a threadless system, if you prefer higher bars, you have no choice but to add a bunch of spacers and a riser stem -- which many of the style Nazis frown upon. That's what I had to do on my bike and I've gotten used to it now. But it still doesn't look as nice as a classic threaded stem, in my view.
you cannot livedjg
Mar 14, 2002 6:12 AM
for the style nazis. My 41 year old lower back doesn't bend like it used to, so I've got the Zepp flipped for a bit of rise (at least the writing goes both ways, so maybe they'll let me live). The older system was certainly more flexible (viz. height adjustment with a given stem), but I don't think the rise looks bad per se. Maybe I just don't get the whole stem fetish thing.
re: extended head tubes?jtolleson
Mar 13, 2002 8:28 AM
Obviously, all geometry intersects. A head tube extension (which looks best aesthetically as no more than 2 cm) does give that extra height to the bars, which can be an issue with riders who need a smaller frame for standover clearance but don't want a big saddle-to-bar drop, and don't want to go to a compact geometry. From the other posts here, I guess it is also a possible issue for really tall riders.

On a traditional geometry road bike, your head tube is going to be the same height as the top of your seat tube. If you are like me, and prefer a decent about of standover (say, 1 1/2 inches or more) yet don't want the huge drop to the bars, you have basically three choices: 1) spacers/riser stem; 2) a head tube extension or 3) a sloping top tube.
standoverjaybird
Mar 13, 2002 9:03 AM
so it is common to have more than an inch of clearance? My real dilema is that I am looking at a LS Tuscany the I have 1.5 inches of standover on the 59 and <1 inch on the 61. I like the tt length of the 59 better but I was a little worried about the standover.
Why?Ray Sachs
Mar 13, 2002 10:06 AM
You were worried about too much standover clearance on the 59? What for. If you otherwise fit the 61 better but you didn't have enough clearance, that's a concern. But if the other angles and contact points on the 59 work right for you, there's no harm in having a little more standover clearance than you absolutely need.

-Ray
Exactlyjtolleson
Mar 13, 2002 10:48 AM
Too much standover is not a per se problem. Only when it is a proxy for a bike that is overall too small (ie., can't get seat high enough without exceeding maximum seatpost extension, can't get bars high enough, or wind up with too small a TT). Certain the 1 1/2 inch standover should be no obstacle to you, so look as the other issues (bar height and TT length) are good.
Exactlyjaybird
Mar 13, 2002 11:14 AM
That was my main concern with the 59. I was just wondering since that is the only fit factor that was questionable. My current frame is an old Trek 770 with a 60cm (c-t)seat tube and a 57.2 (c-c) top tube. I have just about a fistful of seatpost and a 110 stem that makes its bend about an inch above the headset. I have had several people check the fit on the Trek and I like the way it feels. The Tuscany has a 59cm (c-t) seat tube and a 57.5 (c-c) top tube. I think with the extended headtube on the LS and the 25+/-mm of stack height I can get almost identical handlebar and seat positions. Right?

Thanks for all of the help.

J.
re: extended head tubes?Pjkad
Mar 13, 2002 4:42 PM
I'm one of those tall folks who needed a long head tube to get the upright position I wanted. I normally would be fit with a 64cm with level top tube. But my custom Seven has a slight slope in the top tube (3 degrees), a resulting 62 cm seat tube length, and a long 28cm head tube, and plenty of standover. I got a somewhat compact frame with a very comfortable position. I only wanted a few centimeter drop from seat to handlebar. That's the advantage of custom. I do have the longest head tube I've seen, which is always a topic of conversation on group rides!
I bet a lot of this stuff is accomplished, but if I had to pin..Leisure
Mar 14, 2002 5:02 AM
it down, I'd say it's most fundamentally the style police.