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Discussion Starter · #1 ·
I have decided I'm going to get an Anthem x2 but the bike shop only has a large in stock for me to ride. I am 5'10" with a 32.5" inseem with tennis shoes on and currently ride a medium Giant XTC2. I am right on the line for medium and large. I know I can shorten the stem length if it seams to large but not sure if thats the right thing to do for my height.

The guy at the store said that I have long arms and a large would work well. The thing I am not sure about is that on my medium my seat is slightly higher than my handle bars. On the large anthem with a proper seat height, the seat and bars are about even which makes me feel like I am sitting up straighter.

So, I'm looking for some guidance on what I should get or how to tell what I need. I know everyone says just get what feels right but I am still a new rider and what feels right may because I don't know what correct feels like. I may be used to my medium bike even though its to small. I will say that on the medium I feel like the steering is a little twitchy like I am over steering, if that makes sense.

Any help is appreciated.

David
 

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Discussion Starter · #2 ·
My wife measured me up using the info on this website http://www.sierratradingpost.com/lp2/bike-fit-guide.html and my measurements were

inseem 31
torso 24
arm 26.5

Based on there algorithm my top tube length should be 19.25 which means all the anthems are too big! It also says my stand over should be 26-29 inches! My XTC medium is 29.5 which is in the ball park but the Anthem is 31.0 for medium and 32.1 for large.

Remember when we were kids and buying a bike meant going to wall mart and finding one with pretty colors?

David
 

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Okay, I'll bite.

This is a tough call and every clown on this site will have an opinion. This bozo say the biggest problem is that we are not in the same room with you and seeing these bikes. It is all theory and gestimation. Seat tube is nearly irrelevant to fit.

You sound like you have a long torso, have adapted your medium bike to your proportions, and become accustomed to it. Anything else will feel strange but that doesn't mean it is wrong.

Relative seat height/bar height is not so much an indication. Stem height can be limited by steering tube length. Barring that spacers and stem angles can expand bar height greatly. Seats can go as high or low as needed. This is largely independent of bike size.

Seat Fore and Aft are very adjustable as rails allow for adapting and Set-back seatposts expand that. Stems come in all sorts of lengths. This is also independent of frame size.

Seat position is GENERALLY set by placing the knee over the pedal (KOP). The pedal spindle runs across the midpoint between the ball at the base of the great toe and the ball just below the little toe. That set, the seat height is coarsely set high enough to get extension on the leg but low enough to avoid rocking your hips. (There are formulae and knee angles but this is a good thumbnail.) Seat fore/aft is set by placing your fixed foot on the pedal, placing the pedal at 3 o'clock and moving the seat forward until your patella (knee cap) just overt the pedal spindle. Subsequent fine tuning of height and fore/aft are needed.

ALL THIS IS INDEPEDENT OF BIKE SIZE!

The key point specific to bike size and your body is the twitchiness of the steering. Climb on a Small bike and you will see what I mean.

My call is that your torso overwhelms the TT on the medium and would be better suited to a bike for a taller man. The large is 2 cm longer in the wheelbase and TT and handling will relax under you.

That said, do not decide without riding both the medium and the large. Other models of the Giant line are not substantially different in the critical dimensions so try them. Bring your Giant in to the shop and compare them side-by-side. As we are not with you this is the best index I can offer. I use it every time I can when I change bikes for myself or friends and teen racers on my team.
 

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Discussion Starter · #4 · (Edited)
I just did the fit calulator at http://www.competitivecyclist.com and tried to do everything exactly as they explained it. My numbers were...

Inseam 33.5 in
Trunk 24.5 in
Forearm 13.5 in
Arm 25.5 in
Thigh 24.5 in
Lower Leg 22.25 in
Sternal Notch 57 in
Total Body Height 69.75 in

That evidently works out to me potentially needing the following...
Standover Height Range 31.8 - 32.5 inches
Virtual Top Tube Length 23.1 - 23.5 inches
Stem Length 9.7 - 11.3 cm
BB-Saddle Position 74.8 - 76.3cm
Saddle-Handlebar 53.4 - 55.0 cm

What that looks like it boils down to is that as far as stand over goes I am in the large category but as far as top tube length I am in the medium category. I think that left me in the same place as before.
 

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Discussion Starter · #6 ·
I figured I'd add some closure to this.

I bought the medium back in July and it has been perfect for me. I am really glad I waited and special ordered the medium and didn't get the large just because it was in-stock.

David
 
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