New Bike questions about the frame size

Can you normally trust the guys at your local (auto repair, dry cleaner, car dealership, investment services, etc. just pick one)? Like any other business, there are good LBSs, there are bad LBSs, there are compentent, caring salesmen and there are those out for their own agendas. Sounds like you got one of the latter. I tell everyone that asks that if the salesman puts you on a bike based solely on your inseam or standover clearance, to run like hell, as that's one of the least relevant measures to consider.

Sounds like your bike may be too small, but how does it feel? Have you been on any reasonably long rides?

I'm 6 foot even with a similar inseam; I ride a 56cm that is a tad long in the cockpit. I compensated by moving the aerobars back a tad.

You may indeed be fit correctly depending on how you measured your inseam. Check out bikefitting.com and measure your inseam as suggested on the website. You can then use their calculator to ESTIMATE your frame size.

If you could somehow post a video frame of yourself, captured with your crank arm nearest to the video camera lined up with your seat tube, I could do a quick analysis for you. This is best done while your bike is on a stationary trainer.

B-One

A 56cm frame for a 6'1 person with a 34" inseams seems much too small to me.  Unless you have an abnormally short torso for your height, you are going to have back problems even if you put a longer stem on it.  You can always adjust your seat post to fit your legs but there is a limit to the length of stem you can attach to your frame.  I am 6' with a short 31.5" inseam; my torso is rather long, so I have to ride a 58cm bike with a 130mm stem. 

A 56cm frame for a 6'1 person with a 34" inseams seems much too small to me.  Unless you have an abnormally short torso for your height, you are going to have back problems even if you put a longer stem on it.  You can always adjust your seat post to fit your legs but there is a limit to the length of stem you can attach to your frame.  I am 6' with a short 31.5" inseam; my torso is rather long, so I have to ride a 58cm bike with a 130mm stem. 

A photo would clear things up.

actually I remember the sales guy telling me that I was right between a 56 and 58 and that he suggested going with the smaller frame. He said you should try to get the smallest frame that you would fit. Is this good advice? I'll post I pic once I get one, I would love to see if the bike is sized right, how should I take the Pic?

The pic is best captured from a video of you riding your bike on a trainer; this ensures a true representation of your pedal stroke and is easy to photograph because you are stationary.

What I need is a still of you pedaling with the crank arm closest to the camera lined up with the seat tube. I will post an example or two here tonight. I do not have a photo available here while I am typing on company time.

I have been doing fit analyses for local cyclists and triathletes this spring. It has been an education for all involved.

B-One

How long is the top tube? This varies a ton on bikes. I'm 5'8 and ride a 56, though would probably prefer a 54 in most bikes. Maybe your dealer is trying to set you up in a radical tight, compact, super fast set-up... I have a MTB that is only a 16" frame and is super compact for tight terrain, but I spec'd it that way. I'm guessing your dude don't know nothing.

Attached is an image of an individual riding a bike that is too small.

The seat is too high and the knee is not extended far enough. The knee angle should be between 145 and 155. The shoulder angle is also too acute and should be closer to 90. This young fellow simply out grew his bike.





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BTUpload.JPG (27KB - 37 downloads)

I just purchased a specialized allez sport. I'm 5' 10" with a 34" inseam...I'm I'll legs, short torso. But I am on a 58" frame and it is very comfortable. The 56 made me feel too low to the ground for me.
I would recommend going back and at least test riding the larger frames to feel the difference. But based on my experience I would definitely say the 56" frame is too small.

Just some info I found out while bike shopping...specialized frames seem to run smaller than other brands. I was a 56 on cannondale, felt and giant...but was a more comfortable on the 58" specialized. Test ride a lot. After I rode the various sizes and models, my bike shop stuck me on a trainer to double check the fit. A good bike shop will let you take them out for a spin and spend time to help you determine the right size-- if they don't...go somewhere else.

I have learned very quickly that a bike is not just a purchase...its an investment.

Edited by sulis 2005-05-04 10:18 AM

Different manufacturers measure frame size differently. Complicating matters further: top tube lengths vary in relation to seat tube lengths. To simply judge what our Outcast has been sold based upon the information we have is mere conjecture.

The fellow pictured is similar in proportion to sulis and purchased a 56cm bike online (against my recommendation). I have not had a chance to analyze his position on his new bike, but he MAY have found a bike that fits him properly. I have heard from some reliable sources that he has become scary fast on his new bike. He is an excellent athlete. I will see him at a tri this weekend.

Outcast,
Do you need any more instruction on getting a video still captured or do you just need more time?

Sulis,
If you would like an analysis, I can do one for you also if you can get me a photo.

Just need more time i'll post try to post the video tomorrow.

Cool! Standing by.

Thanks for the offer B-One. Very generous of you. I am fairly confident I'm good as my bike shop spent a lot of time with me making adjustments and such. Thanks though. I Love how generous everyone on BT is!!!

i would suggest a different shop. experience is the #1 thing to look for in a sales rep. I wish you guys had some idea of how good my LBS is. There not pushy, most are former pros, and if I'm in a pinch they'll give me any where between a 10 and 30% discount just cause they like me.

about that picture. Wouldn't shortening the seta height, decrease the leg angle thus making it farther from the ideal, rather than closer? if the seat were a bit higher, and farther forward, he could just move the armrests forward (or get longer bars) and he'd be okay? Of course if he's trying for the slam position he needs to go the other way.

I wonder if it might be cool to run a forum where we all upload pics like this, and ALL give our input on whether the position is good or not. Put our collective heads together as it were.

Well I now feel like I can trust the guys at my LBS. I went back last night, really just looking for them to fit me right for the bike to make up for the small frame and they almost insisted on me swaping it out for a 58. Of course I jumped at the chance and I must say the 58 fells much better, feel a lot better about my bike purchase now. I still would like to post some pics to get some feedback on my fit. I think Dovecom's idea to start a post where we can post pics and share advice on our fits would be great. Of ourse I would be looking for more advice than I would be sharing seeing that I'm a complete newb at this.

If you are referring to the photo I have posted lowering the seat would be a horrible choice. His seat is at it's max height and can't go any higher. This indicates that he is on too small a frame.

The thread you suggest would be great.

Good to hear! Post something here when the new thread is started. I look forward to learning more.

First of all, Dan Emfield has MUCH more experience than I. There are others with more experience than me also that differ slightly from Mr. Emfield as well. In either case, the resulting differences are minor (1-4 degrees). I think what is important is that you choose what you are comfortable with after you have done your research.

Dan's text is below. He allows for some varaibility in the selection of the point chosen at the distal end of the leg. I like to use the greater trochanter - lateral epicondyle measurement for the following two reasons: I have found that if one chooses the pedal axle as the distal point of measurement, the actual hip angle remains a bit too acute. Also, the hip angle may vary if one chooses the pedal axle depending on cleat placement.

Quote from Dan's website:

"That hip-to-the-foot line is a little tough to nail down. Ought it to be from the hip to the bottom bracket? Or to the maleolus (bony protrusion of the ankle)? Or to the pedal axle? If so, where? At the bottom of the pedal stroke? With the crank in line with the seat angle (or relative seat angle)? If it's the hip angle you're measuring, why measure the angle in its most obtuse configuration? Why not at its most acute, when your foot is at the top of the pedal stroke?

All these are valid observations, but it doesn't much matter. If the proper bike fit is in fact proper, it doesn't matter where you measure, but each of these lines formed by the proximal point (hip) and the terminus at the line's distal point (ankle, BB, pedal axle, whatever) is going to change depending on which distal point you choose. I personally favor the pedal axle at the bottom of the pedal stroke, and my definition of "bottom" (for the purposes of measuring this angle) is not at 6 o'clock, but at the point where the axle is in line with the seat angle." (http://www.slowtwitch.com/mainheadings/techctr/bikefit.html)