road vs. mtn geometry

based on a comment that Kathi made about buying a mtn bike based on how a road bike fit, I was very curious and asked a pal of mine who is a custom frame builder about this.

Quote:

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That's why I was looking at Titus. Their smaller frame geometry is similiar to my road bike frame

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anyway, I asked Mark Hickey of Habanero Cycles
">
> if you have a road bike that fits you, can that be translated at all into
> mountain bike fit?"

his reply is,
There is no absolute way to correlate the two positions, since
there is a wide variation between what different people consider
"proper positions" on a bike.

That said, I've had very good success fitting roadies on MTBs and
MTBers on road bikes by using typical road/MTB fit relationships
(based on experienced riders who go both ways). I factor in the
type of riding they'll be doing (lower, longer if it's all fire
roads on the MTB, for example), their experience level, and any
physiological issues (back problems, flexibility, etc.). Then I
sacrifice a chicken...


I just thought this was interesting.

Irulan

Maybe this is marketing hype but if you check the geometries of the smallest Hard tail Trek (WSD), Cannondale (Femine, sp?) Kona, Wylder, Titus, Airborne, Specialized they all have seat tube angles of 74 degrees and head tube angles of 70 degrees. Even if they don't market these bikes specfically to women they still have the steeper seat tubes and slacker head tubes.

By comparasion my road bike frame has a seat tube angle of 75 degrees and a head tube of 72 degrees.

Now, if you look at my mtn bike the seat tube angles are 72.5 degrees and 71 degrees for the head tube angle.

I don't know what the answer is, I just know that my old mtn bike frame doesn't have the right feel anymore.

one possiblity is that your mountain riding style and needs have changed too! I'm not trying to tell you what to do, not at all...it's just good to educate oneself to as many possibilites as you can. My first mountain bike, I loved but I outgrew the geometry by increasing my ability as a rider. For me, a much more agressive geometry was the answer. When you say that the bike doesn't free right anymore, that's what I think of.

I am a curious person, I like to explore the possibilites. I tend to take all marketing material with a grain of salt, and ask a lot (too many <g>) questions. I also tend to think aloud here at TE.
One should make the final choice on what feels right, and not what some promotional literature or magazine says will work. Sure, trust the experts... to a point.

Anyway, time to fo pack for NORBA.

Irulan

Irulan,

Thanks, I think you've hit the nail on the head! When I bought this bike I probably didn't ride more than 500 mi a year, mtn and road combined. Now I'm riding 2,000 + miles per year. I'm a much stronger, more aggressive rider and I'm not happy on the bike unless I'm in an "aggressive position". The frame doesn't get me there naturally and so I had to do it myself.

Guess if I decide to keep this bike I'd better do a lot of core conditioning!

Quote:

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Originally posted by Kathi
Irulan,

Thanks, I think you've hit the nail on the head! When I bought this bike I probably didn't ride more than 500 mi a year, mtn and road combined. Now I'm riding 2,000 + miles per year. I'm a much stronger, more aggressive rider and I'm not happy on the bike unless I'm in an "aggressive position". The frame doesn't get me there naturally and so I had to do it myself.

Guess if I decide to keep this bike I'd better do a lot of core conditioning!

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I know when I moved from a recreational mtn bike to a race type (XC) bike, the differences were huge. First, it felt really different. Then every technical "error" in my riding was exagerrated. (endo city for 6 weeks) Now, you can't rip my bike out of my cold, dead hands....

I answered my own question! There is a significant difference in the feel of a bike with a steeper seat tube angle vs. a slack seat tube angle.
I finally picked up my Titus Racer-X. The shop did a complete fitting for me. The bike was declared a perfect fit except for the seat post which needed to be changed to a zero degree post and some spacers on the stem.
Apparently I have a very short femur and the zero degree seatpost gave me a better alignment over the center of the bike.
I've already put 43 miles on the bike and everything feels better. I don't hunch my shoulders, curve my lower back, have pain in my hands and I'm definitely centered over the pedals like I am on my road bike. I even have a better position on the saddle. The bike handles so well its almost scary, it absolutely turns on a dime.
The bottom line is, if you're a small rider with a short femur looking for a mtn bike (or a road bike) a prime consideration is how steep the seat tube angle is. For comparison, my road bike is 75 degrees and the new mtn bike is 74.5. The Voodoo (old mtn bike) was 72.5 degrees, way to much for a small rider.
I checked many companies before I made the decision to buy my Racer-x and along with tt length I checked seat tube angles and head tube angles. Even though many made small frames the seat tube and head tube angles did not change to accomodate small riders. It seems they were still being designed for average men.
Because of this, my options for a high end bike mtn bike were limited, unless I wanted to go custom.
Anyway, I now have 2 wonderful bikes, but my goal of this post was not to brag about my bikes but to help small riders in their decision making process.
Anyway, I won't be riding much for a while, I'm headed out tomorrow for 2 weeks of spring skiing.