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Fitting Your Bike Are you confused about how you should fit a bike to your particular body dimensions? Have you been reading, found the terms Merxx or French Fit, and don’t know what you need? Every style of riding is different- in how you fit the bike to you, and the sizing of the bike itself. It’s more than just measuring your height, reach and inseam. With the help of Bike Fitting, you’ll be able to find the right fit for your frame size, style of riding, and your particular dimensions. Here ya’ go…..the location for everything fit related.

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Old 03-08-15, 07:56 PM   #1
Babe Ruthless
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Road bike, short legs, weird frame sizes

Hi folks.

I recently bought a new frame online but it hasn't shipped yet because I'm having a hard time deciding between two suggested sizes.

My current road bike is a 52 (c-c seat tube; c-t is 55cm approx.). With 55cm c-t and a horizontal top tube, I kind of "seat" on the top tube on the clearance test (very little clearance, 1cm tops, TT actually touches my soft parts if I'm not careful). I slammed the seatpost right down to make it easier for me to climb and start pedalling (I've been riding in the city mostly with frequent stops), but once I'm on the bike I feel the saddle's too low. I guess I've short legs but not THAT short.

I'm also quite lacking in flexibility (I can currently touch my legs about 2-3cm below the kneecaps).

Anyway here are my measurements, taken by someone at a Y's Road bike store in Japan (with a bit of a language barrier between me and the bike fit specialist), all in mm:

Shoulder: 425
Arms: 625 (both)
Height: 1733 (173.3cm)
Inseam: 810 (I measured 800 myself, but I was more careful with said soft bits than the Y's Road gentleman)
Torso: 613

They didn't take my "sternal notch" height. :-(

Anyway, here are the specs for two sizes I'm considering for this new frame, please advise which will fit better considering I have 90 and 100mm stems available here and could always get a different size at the LBS, from which, BTW, I won't buy a frame under any circumstances (that's final, I'm having this shipped :-).

[TABLE="width: 300"]
[TR]
[TD][/TD]
[TD]"Size 52" Frame[/TD]
[TD]"Size 54" frame[/TD]
[/TR]
[TR]
[TD]Seat tube length c-t[/TD]
[TD]490[/TD]
[TD]510[/TD]
[/TR]
[TR]
[TD]Effective top tube length[/TD]
[TD]537[/TD]
[TD]548[/TD]
[/TR]
[TR]
[TD]Reach[/TD]
[TD]386[/TD]
[TD]387.1[/TD]
[/TR]
[TR]
[TD]Stack[/TD]
[TD]526.5[/TD]
[TD]543.1[/TD]
[/TR]
[TR]
[TD]Head tube length[/TD]
[TD]120[/TD]
[TD]140[/TD]
[/TR]
[TR]
[TD]Seat tube angle[/TD]
[TD]74º[/TD]
[TD]73.5º[/TD]
[/TR]
[TR]
[TD]Head angle[/TD]
[TD]73[/TD]
[TD]73[/TD]
[/TR]
[TR]
[TD]Wheelbase[/TD]
[TD]970[/TD]
[TD]976.1[/TD]
[/TR]
[/TABLE]

I find these seat tube lengths strange (49cm on a "52" frame and 51cm on a "54"). Both apparently fit me, maybe top tube length is the real question. I don't know. Please help.

Last edited by Babe Ruthless; 03-08-15 at 07:58 PM. Reason: Table width
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Old 03-09-15, 01:57 AM   #2
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Based on your lack of flexibility I would recommend the 54cm frame. It has a more relaxed seat tube angle by half a degree and a taller "stack" or head tube length. The higher stack means you don't have to reach down as low for the handlebars.

The 52cm frame isn't really that much smaller than the 54cm frame. The biggest difference is the steeper seat tube angle which is a fudge really. The 54cm frame is more honest.

The discrepancy between the actual seat post length and the nominal frame size comes down to the sloping top tube (compact) design. The frame is sized as if the top tube was level. This is actually the right way to do it otherwise the sizing would be misleading Don't be concerned about stand over clearance. Its nice if you have it but its not the right way to size a frame.

Anthony
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Old 03-09-15, 05:32 AM   #3
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Thank you, Anthony. I had a notion the two frames would be similar based on reach (38.6 vs. 38.7 cm) but I didn't realize seat tube angle, for instance, would have such an effect from such a small difference (.5 degree).

What worried me about "54" was the effective top tube length, it was at the very end of the range that different bike fitting sites would give me. Then again, "french fit" at competitive cyclist gave me roughly that number (548). Please bear in mind my seatpost has a 2 cm offset.

Won't I be too stretched out on the bike because of that length? Should I get maybe an 80mm stem for this build?

Also, about "52": can I get a similar fit to "54" with a higher handlebar position (using spacers)? I ask because most bike fit programs tell me I should get something with 53.5-54 cm top tube, but maybe that's for a more aggressive position and I'm looking to ride more relaxed right now as I ease myself into road bikes. I just don't know much about this!

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Based on your lack of flexibility I would recommend the 54cm frame. It has a more relaxed seat tube angle by half a degree and a taller "stack" or head tube length. The higher stack means you don't have to reach down as low for the handlebars.

The 52cm frame isn't really that much smaller than the 54cm frame. The biggest difference is the steeper seat tube angle which is a fudge really. The 54cm frame is more honest.

The discrepancy between the actual seat post length and the nominal frame size comes down to the sloping top tube (compact) design. The frame is sized as if the top tube was level. This is actually the right way to do it otherwise the sizing would be misleading Don't be concerned about stand over clearance. Its nice if you have it but its not the right way to size a frame.

Anthony

Last edited by Babe Ruthless; 10-02-15 at 02:13 PM. Reason: Typos
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Old 03-09-15, 02:04 PM   #4
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When it comes to top tube length and reach there are two ends of the tube that can be adjusted. The front end of the tub, which is where it SHOULD be adjusted, or the back end of the tube (seat tube angle) where the bike manufacturers usually adjust it because its easier to do. The trouble with moving the seat forwards to reduce the reach is that it places more weight on your hands and shoulders which is uncomfortable. See my replies on the thread, Road bike size for short woman with long arms.

By the time a good bike fitter moves your saddle back to compensate for the steep seat tube angle on the 52cm frame you end up with a bike that has an almost identical top tube length to the 54cm frame. If you need a 80cm stem then use one. Also check the crank lengths on the bikes. I suggest that based on your inseam that 165mm cranks would be ideal for you. 170mm is a little stretch but don't go longer than that.

Anthony
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Old 03-09-15, 03:16 PM   #5
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Just realized that my phone's autocorrection feature changed "seatpost" to "septets". What I meant was my seatpost has a 2cm offset. If that changes something, that is. ��
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Old 03-10-15, 01:16 AM   #6
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Originally Posted by Babe Ruthless View Post
Just realized that my phone's autocorrection feature changed "seatpost" to "septets". What I meant was my seatpost has a 2cm offset. If that changes something, that is. ��
A 2cm rearwards offset in a seatpost is pretty much standard. You can get zero offset seatpost's or seatpost's with 4 to 5cm offsets in order to fine tune your fit.

If you bought a bike with a seat tube angle thats too steep you can always fit a seatpost with a 4 to 5cm offset to correct it yet this just lengthens the effective top tube length back to what it would be if the bike manufacturer hadn't built the frame with an excessively steep seat tube angle in the first place. Why do they do it?

Simply so they can put a short top tube length on a specification sheet.

Anthony
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Old 03-10-15, 04:51 PM   #7
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Thank you for all the replies, Anthony. I finally ordered the 54cm version, it'll take a while longer to ship (about 30 days more) than "52" but I reckoned my back will thank me later.
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Old 03-11-15, 09:40 AM   #8
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Sorry this doesn't have anything to do with the original question, but may I know why you plan to never buy from Y's Road? (I know they don't have the best reputation online, but is it your personal experience as well)?

I'm asking because I'm really tempted to buy a bike from them as they're the nearest LBS stocking the model I want, but I hesitate. Too bad my favorite LBS only stocks Trek when I want a Pinarello!
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Old 03-11-15, 01:13 PM   #9
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Sorry this doesn't have anything to do with the original question, but may I know why you plan to never buy from Y's Road? (I know they don't have the best reputation online, but is it your personal experience as well)?

I'm asking because I'm really tempted to buy a bike from them as they're the nearest LBS stocking the model I want, but I hesitate. Too bad my favorite LBS only stocks Trek when I want a Pinarello!
Hi marimorimo, I think my original post was a bit misleading - just realized it after reading it again. I went to Y's Road to buy components and took advantage of their Bioracer bike fit programme (which costs 1000 yen, refundable if you buy a complete bike from them) to find out roughly what frame size I needed. That was back in October and they were really great - the bike fit guy was very thorough despite a complete language barrier (I don't speak Japanese and he didn't speak English) and the guy who sold me the bike's drivetrain and brakes was nice - and patient. I was in Tokyo and went to different Y's Road branches (eventually buying everything in Shinjuku).

I never planned to buy a complete bike from them because I already had a local (Brazilian) supplier for an aluminium frame. I ended up with a slightly different frame than the one I had in mind, and I've since learned from sore experience that its geometry doesn't really suit me. So I'm now replacing it.

I only mentioned that I'd never buy from a LBS to avoid the inevitable "try a few bikes at the LBS" replies, since I'd already purchased the frame online and was just asking for advice on the best-fitting size .

About Y's Road: I visited a few of their stores in the Tokyo area and they almost feel like different businesses (at least for me), so maybe bear that in mind. Each store has different items in stock and specialize in just a few types or brands.
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Old 03-11-15, 04:24 PM   #10
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Oh, OK. Thanks for your reply! It seems Y's Road stories run the gamut from "they're the worst" to "the staff were pretty good and helpful."
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Old 03-11-15, 05:47 PM   #11
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One Difference Trek, like Big Importer wit dealer networks has a Dealer credit plan , they can be stocked then sold, then paying the credit account at season end.

Pinarello and a lot of boutique brands the shop pays for them Up Front.
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Old 03-11-15, 08:31 PM   #12
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Oh, OK. Thanks for your reply! It seems Y's Road stories run the gamut from "they're the worst" to "the staff were pretty good and helpful."
Yes, like I said, to me it seemed that each branch is run like a completely different business. I can recommend their Shinjuku road bike parts store, they were excellent. The other Shinjuku road bike branch was also very good. The Shinjuku crossbikekan wasn't so helpful. :/
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