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Discussion Starter · #1 ·
I am looking at a 57 opal. it has the tt length i want but it's head tube is huge. I would have to run a neg stem angle to get the drop i want( only approx. 3 inches)
I want zero spacers, but it limits my drop in the future. I don't think i will need more than that but over the last year I went to 3 inches from zero and it is more ballanced and more comfortable. --just wondering about your progression of position over time.
 

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more details...

A negative stem angle, if you mean negative relative to the steering tube, is far moe common than a positive angle on road bikes.

It's not often that head tubes and TTs get very far out of proportion. Most people complain about the opposite problem. In short, if the head tube is "huge" then it indicates that you may have chosen the wrogn frame size. The Orbea Opal is a good example of a model that has too few sizes, so compromises were made on the HT to TT proportion.

It's not hard to calculate the stem angle and spacrs required to produce a particular handlebar height, as measured from the ground to the top of the bars. Do yu have a specific handlebar height and saddle height?

http://www.brittonbikes.com/bikes-2006/orbea/opal/06-opal-geo.htm

I'd also like to know the stem length that you plan to use with this perfect TT length.

There is also the chance that there is a difference in the seat tube angle that affects the comparison of TT length between this frame and your current frame.

What is the size and model of your current frame?
 

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Discussion Starter · #3 ·
2005 trek 1500

I am just overlaying measurements onto the trek frame. I cant find geometry info on my bike. only 2006 treks. It looks like I need a 54. the motivation is there is a 57 for cheep.
 

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Trek's haven't changed...

It's rare for Trek to make much of a change in their geometry. If you post the year and model, it can probably be figured out.

The worst thing to do when looking for a new bike is to buy the wrong size, just because it's a bargain.
 

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Huge head tubes! I purchased a Mitis on ebay 54cm. Orbea specs 148mm. I received the frame, and the head tube is 170mm. Maybe 148 between bearings. My Cannondale specs 146mm, this is the actual bottom of headset to top. I was very dissapointed.
 

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head tube length...

The standard method of measuring the head tube length is just as it would imply, the bare head tube, not including the headset. Integrated headsets may add as little as 5mm to this length, or as much as 20mm, depending on the top section provided. Tall top sections can be replaced with short ones to reduce the height by 7-15mm.

If the frames uses a conventional headset, then add 25-30mm to get the total minimum length.
 

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Orbeas do have slightly taller than average head tubes; I just picked up a 59 (or is it 60? the biggest) opal frame, and the top of the head tube is about 1.5 cm higher than my c-50 (same top tube length and pretty damn close for the rest of the geometry). I personally like this as it allows me to run fewer spacers, stiffening up the front end a bit.
 
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