Frame Size, Oh My!

[ThorSonic]

I hope I'm not opening Pandora's box, but I'm a little confused about frame sizing for road bikes (Heck, I'm confused about frame sizing on mountain bikes as well.) So, with a 30" inseam measured using the book against the twig and berries method (can I take the book out now?), it would seem that I would be looking at a 51 to 52cm frame. Does that make sense? I'm 5'10 (5'10 and a half if I hold my breath.) Now, that is without adding any of the subtle nuiances that various peoples out there propound on their websites. It just seems small, but what do I know?

Thanks,

Rich

[waitabit]

I hope I'm not opening Pandora's box, but I'm a little confused about frame sizing for road bikes (Heck, I'm confused about frame sizing on mountain bikes as well.) So, with a 30" inseam measured using the book against the twig and berries method (can I take the book out now?), it would seem that I would be looking at a 51 to 52cm frame. Does that make sense? I'm 5'10 (5'10 and a half if I hold my breath.) Now, that is without adding any of the subtle nuiances that various peoples out there propound on their websites. It just seems small, but what do I know?

Thanks,

RichI'm 5'10" also and I ride a 52cm.I hope that help's.

[nigel]

Sizing can be an odd thing for many people. Like im 5' 11" and ride a 54-56cm depending on top tube length. Every brand has different measures which do not help things.

For a mtn bike the best rule of thumb is 2.5" is room when your standing over the top tube. So with my 32.5" inseam i ideally have a 30" standover (i really ride a 28" standover with a 23.5" top tube tho). Then you run into the arm length as well. This can be adjusted with stem length and rise. However if you go too long with a stem your fornt end will repsond slower than if you ride a short stem. Thats why i run a long top tube, so i can run a short stem and have spot on steering.

For a road bike, if its a traditional frame you can get away with about an 1" or more of standover then figure you length the same as you would for a mtn bike. If its a compact frame your a medium and leave it at that and just figure your stem length (more than likely its going to be a 100-100mm)

All that said, id recommend you try something in the 53-55cm range. Also do not be afraid to have them put different stems on for you to try. It takes only about 1 minute to change em if they have a front plate. And most shops are more than willing to do this if it will help fit you and get you to buy. Also get your knee postion correct with the saddle height and fore and aft otherwise the length could be way off.

Oh yeah and the length of the top tube and bend of the arms. Sure there are "by the book" ways to figure this, but i always told customers its what feels the best for you. not eveyone wants to be "race fitted" and just want and need to be comfortable. No sense in getting a bike in a size that you wont ride very much due to not feeling right.

Douglas

[tedsti]

Take a look at www.wrenchscience.com (http://www.wrenchscience.com) I have heard good things about the results.

[ThorSonic]

Thanks for the info. After spending the last years only riding motorized high performance two wheeled vehicles, I have a good understanding of ergonomics, suspension, weight distribution; but when you take the engine power out of the scheme things do change. I'm glad that the changes aren't as great as I was afraid they were. Science is science and comfort is comfort, and the special mojo dance is always necessary. What is frustrating is trying to understand all the manufacturers. On motorcycles, you will end up looking at 4 or 5 bikes for a specific application. With bicycles (because the profit is freakin' HUGE) every Tom, Dick, and Hairless tatooed punk has a bike company. And with the freakier ones holding the most attraction to me, it is tough to even get a starting point other than how much money to spend.

If only all our problems could involve such glorious suffering!

Richard

[funky-funky-chicken]

I think sizing of a bicycle involves a bit of black magic. It takes a rider's opinion (that is very subjective) to know what feels good. I think that it can unfortunately take a tremendous amount of experience to find just the right fit. There are lots of different ways to look at the geometry of a bicycle and one measurement isn't necessary all inclusive. There have been lots of "systems" that take into account lots of measurements of various body parts, compare them to some version of a table to come up with a recommendation based on a whole bunch of averages.

I find it interesting that if you read down through the posts in this thread, there are a few people that are right about in the same size. 5' 10" give or take an inch. The size recommendations have been anywhere between 52-56cm. I am just a hair over 5' 11" and I used to think that I rode a 56cm frame... had several of them. It's been a very expensive process, but the size of my frames has "grown" to be mostly 58 and 59cm now and I have never been more comfortable. What's more, I just changed to a wider bar and different stem on a bike that I honestly have at least 15k miles on. Rode it yesterday and it's like a completely different bike. Maybe it is the fact that I've gotten older... My most recent custom frame is a 60cm. I'd always thought of myself as pretty average sized person.

Richard, while I appreciate the humor and suggestion that there are so many choices with bicycles is the profit margin. I think it has a lot more to do with the fact that there are so many subtle changes in materials and geometry that can be made that can affect comfort and performance. Everyone thinks that they can build a better design. Without much of a way to objectively compare bicycles, the "lighter=better" and "smaller=more aerodynamic" mentality prevails. I'm more of the "bigger=more comfortable" kind of guy.

[bigwheel]

I agree with "bigger is better". I finally got out on my road bike on Saturday, and remembered how comfortable it is.

My road bike has a 27" (68cm) steel frame, and is great for long rides. (I'm 6'3") If you are a racer, you probably want a super-light bike with a smaller frame, but if you want to go on all-day or weekend rides, go for a bigger frame with some flex.

My prediction: It won't be long before we start seeing full-suspension touring bikes.

[LightWeight]

Take a look at www.wrenchscience.com (http://www.wrenchscience.com) I have heard good things about the results.

I used their fit guide with good success. I was mostly concerned with how long of stem to put on my bike and their recommendation seems spot on.

[redBeard]

Personally, I think fitting road bikes takes a professional (e.g., 'don't try this at home'). I've been road (bike) riding for 25+ years and the bikes with the best fit were professionally fitted. Every body is different and (most) everybody's riding style is different......

It is true I race more than a little bit so my road bikes are set up for that.....

Size? I'm 5'9". My bikes? One (European frame) is a 53.5cm seat tube but a 56cm top tube. One (a Cannondale) is a 56cm seat and top tube.

These may seem strange dimensions but I put many 1000s of miles on them training annually, including many centuries (and longer). They are very comfortable for me.

I like the longer top tube as it lengthens me out for racing -- this is a very European style. The only reason the Cannondale is a 56cm down tube is that most mass produced U.S.-made bikes are 'square' -- same length for seat and top tube and I wanted/needed the 56cm top tube. Soooo, I'm stuck with a tall bike (and the handlebar stem is 140mm!)......

And once you get the correct frame, then there's appropriate crank arm length, h'bar stem length, h'bar width, seat setback, h'bar height, etc.....

[Spike]

Height might not be the best measurement to go by when figuring frame size though it may give some very general idea of approximately what might work for you (particularly if you're a guy). As an example, I'm 5'5" tall but my inseam is 31 1/4 and I take a 53cm road bike. If my bike size was based on my height, I'd be on a toy bike and my knees would be hitting my chin. My mountain bikes are 16" and 16.5" and though that might sound like a large frame for someone my height, the fit is spot-on.

Traditionally, the frame size is calculated by taking a percentage of the inseam (e.g., 67% if using the LeMond method), though some people advocate that it's better to base frame size on torso length (and hence, the length of the top tube) rather than the seat tube. Both methods should get you into roughly the same frame size unless your body measurements are way out of proportion in which case you might be better off with a custom frame that fits your particular body. Mountain bikes should generally be 10-12 cm smaller than your road bike for proper fit.

You can choose to go strictly by the formulas or just use them as guides to get you in the ballpark. There are many variables involved in fitting a bike -- body proportions, flexibility issues, knee problems, etc. -- and IMHO, it's best to let a professional handle it, at least for your first bike. You can use the "fitted" bike as a guide to set up your other ones but it's best to read up on fitting so you have some idea of what you're doing. It's also worth noting that an improperly fitted bike may cause problems later on (particularly knee problems) so getting the proper fit now might save you some pain and suffering in the years to come.

As for my own personal experiences with fitting, I was Fit Kitted on my first good bike and on all bikes purchased since then. We have had to make small adjustments over the years for a knee problem and, more recently, a shoulder injury so I now have to deviate from the standard "fit" a bit (lower saddle, higher stem) but I still swear by Fit Kitting. Which brings us to another point. If the stock fit from the formula doesn't feel right for you, make sure you let that be known during the session. Some "fitters" don't like to deviate from the formula but if it doesn't work for you, speak up and tell them what's not working. You may have to be forceful on this point but there's no sense riding an ill-fitting bike, especially if you just paid for a fitting session. As an example, I purchased a bike last spring, unfortunately from a different shop than my "normal" one, and the person there wanted to go strictly by the Fit Kit formula even though I had told him that we would have to make adjustments because of my injuries. The bike shop had asked me to bring in a bike that fit me well so I had brought my other MTB for them to use as a guide to set up the new bike. The guy fitting me REALLY didn't want to do that and he wanted to stick to the standard formula and not deviate from it one iota. He tried to raise my saddle 1" and when I told him that wouldn't work for because of my knee, he argued with me about it and didn't want to lower it. (FWIW, my saddle height, purely by accident, happens to exactly fit LeMond's formula for saddle height so it's not like I'm way out in left field on that one.) I kept pointing at the MTB I had brought and telling him to use that as a guide but it took a lot of insistence on my part before he finally threw in the towel and actually went over to it and took some measurements. It was really a pain and I shouldn't have had to go through that just to get a proper fit. So beware: just because a bike shop offers the Fit Kit, it doesn't mean they know how a fit a bike. If you're going to get a fit session, you might want to ask around and find out which shops do a good job of Fit Kitting and which don't. That can save you a lot of hassle later on.


HTH

[dave t]

Hollywood has a frame sizing machine at his shop. He can tweak everything around until it is just how you like it then measure everything and there you go.

You can't ride it around but you would know everything is where you want it.

hwoodcycles.com

[redBeard]

I didn't want to mention names but....

<shameless promotion>

I'll even go one step further and say that I think Hollywood is the best fitter in the Cities.....

I was racing in the Ice Crit series earlier this year and after the race he walked up to me and mentioned, "We need to get you a new handlebar stem..." He was watching me race and could tell my bike was not properly adjusted (and I could tell....).

</shameless promotion>