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Geometry experts : a kind of amorphic question?

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Geometry experts : a kind of amorphic question?

Old 12-31-10, 11:10 AM
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Bike geometry experts : a kind of amorphic question?

My wife's 5 yr old Marin Kentfield has been stolen, and we're looking for a bike that would be good for her to commute on and for us to tour on.

She's 168 cm tall - that's 5''6?

The Marin was a 15cm frame, which she loved. Now we're looking for a better suited frame for touring as well, so no front suspension and no women's cruising bikes. No drop bars, because she doesn't like STI.


We tried a size M KHS UrbanX - she said it was too stretched out.
https://www.khsbicycles.com/Images/Ge...-geo-urban.jpg
----

Tried a size M KHS Urban Xpress(really great bike) - she said it feels weirdly cramped and hurts her back.


And the kicker - a size 17(the old one was 15) Marin San Rafael, which she absulutely loved from the first moment she got on it. Although, I couldn't help thinking that it looked way too small for her, and her knees were awfully close to the handlebar every time she had to turn around. I believe it has the same geometry as the Kentfield model

https://www.marinbikes.com/2011/bike_...serialnum=1700



So, how can that be?

Fitting the couples-who-bike-together stereotype fairly well, I'm the one who knows more about bikes than her, and who does all the fitting and fixing and researching, etc.

So I need an answer - How can I compare bikes if there seems to be no basis for comparison? She loves a 17cm bike when she used to ride a 15cm, even though it LOOKS smaller than it should. She feels a bike with a 570mm TT is too stretched out, I understand that, but a bike, from the same manufacturer, with a 565mm TT feels cramped?

How is that possible?

I would like to order a Jamis Coda, but no one imports them on a regular basis, so I'd have to pay up front. I thought I could do it based on her height and proportions, but now I see that I can't.

What kind of sizing and fitting tips can you give, dear experts?
Hope I didn't wear you guys out with this long post.

Last edited by FidelCastrovich; 12-31-10 at 11:46 AM.
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Old 12-31-10, 07:30 PM
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I was perplexed by an adult on a 15cm bike. Tiny. Looked up the brand, and see it's 15in, which closer to an adult size, but a pretty small one.

Likely, your wife hasn't been stretched out enough to have an efficient riding position, so when she tries a bike that's the right size, it feel uncomfortable to her. Is there a place where you can rent a bike that fits her better to ride for a day or so? There are lots of models with straight bars and more upright sitting position. Trek makes a bunch. If she rides for a while, she will get comfortable on the right sized bike and appreciate how much more efficient it is.
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Old 01-01-11, 02:27 PM
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By generic height indicators, she should be on a 19-21" bike, so 17 is pretty small. Her knees will be crashing into her chin. Can you have her sit on a bike and see if her leg is slightly bent when her foot is at the bottom of the cycle?
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Old 01-01-11, 02:38 PM
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consider a Bike Friday, 406 20" wheels are 2nd behind MTB 559 26" in common
world wide tire spares.
custom sizing and drive train options..
Knocks down to go in suitcase for Air Travel, so you omit bike surcharge..
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Old 01-02-11, 09:57 AM
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Radumas - There are places here to rent bikes, but they're mostly mountain bikes or road bikes. We're looking for a hybrid/tourer, and the geometry is different, I believe. But I'm trying to figure out a way to rent that KHS Xpress with a committment to buy it, if it fits.

BTW, how do you figure she's should ride a19-20 inch bike?Looking at charts and my limited common knowledge leads me to think that that's way too big. I ride a 19 inch bike, and while that may be small for me, it's definitely too big for her. That's was she rides to school now in the meantime, and she's stretched way out. Also, the saddle is all the way down. Maybe you're talking about a different type of bike?
Oh, why are you asking about her leg extension? That's just a function of saddle height, no? Can't you achieve proper leg extension on almost any bike?How is that an indication of anything?

I wonder how she rode a 15in bike for so long without ever feeling that it was wrong for her. And to think that I bought it without even measuring her or having her test ride it. I just took the LBS' word.

Maybe I should do that again, now. Just have her adjust to it?

Fietsbob - I doubt anybody imports BikeFridays to Israel, but thanks for suggesting that. Looks interesting.
I knew this was too difficult a question and that hoping for a quick fix answer was too much...
Thanks to those who tried :-)
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Old 01-02-11, 10:23 AM
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I'd suggest going with a bigger frame and using riser bars or bars with rearward sweep for a better fit. It's OK to be upright when riding a bike.... roadies will tell you otherwise.... but check out Grant Peterson. For every roadie who hates Riv Bikes, there is a very happy women riding his style of fit/cycling style.

Go slow and think about things, try things, get the right bike/fit. Your are very lucky... you are a couple who cycles together!
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Old 01-05-11, 12:26 PM
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Update - the LBS that sells the KHS Urban Xpress has agreed to loan it out to us for a couple of days so we can see what's what.
We took it for a relatively short spin and she immediately started complaining about upper back pain. Nothing I did helped.

It's a size M bike, 565mm TT. Everything looks okay to me: the leg is almost fully extended, the saddle all the way aft, the handlebar about two inches higher than the saddle and not at the maximum height.

What can be a possible cause for pain in the shoulder blade area? What can be so wrong that she feels it so sharply and immediately?
To me, she doesn't look cramped, or hunched over. Very much upright, in fact, and spread out just right.

She's going to take it on her regular commute tomorrow, and I would like to make the last adjustments. It's just such a great bike, I really want her to like it.

Could it be her weak upper body/abs?

Thanks again, everybody.
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Old 01-05-11, 01:46 PM
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Yea M, 565 is the top tube common to a 56cm road frame for men.
could be too long
typical womans torso is a shorter% of their height.

try a 5cm stem... short , since TT is long.

you pushed saddle back try pushing it forward to shorten reach.
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Old 01-05-11, 06:41 PM
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What does the LBS say about the fit? Do they have any ideas to fix it? It's still their bike, make them work on fixing it for a sale. It's why your LBS is there.

I'd guess more sweep on the bars, getting the bars closer to the saddle and getting the wrists more North/South (like a road bike, less MTB)
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