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Old 06-19-12, 12:04 AM   #1
jsdavis
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How do I size a road bike or cyclocross bike?

I am currently riding a Marin Muirwoods 29er with a 19" frame. How do I find the size I need for a bike with drop bars? Do I go by the top tube length or is it different on road sizing? My effective top tube is 605mm on my current bike but this puts me somewhere around 60cm for frame size which is the biggest frame from many manufacturers so this is not right. I am 68" tall.

I am using it for the street and commuting so there is no racing involved. The attraction of a cyclocross bike is that it looks like they accept 32mm, and maybe larger, tires so the ride should be more cushy. Even though many of them only have two chainrings and sometimes 48 as the largest, I think that might be ok since I'm stopping every few hundred feet anyway. That and San Francisco isn't flat.
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Old 06-19-12, 12:15 AM   #2
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If you want fat tires and drop bars, cyclocross might be the right bike for you. Or a drop bar commuter or touring bike. Salsa Vaya has very fat tires. CX bikes, though, come with a pretty steep price tag. If you are in SF, you can probably find something on Craigslist that would work. I would be worried about a new bike if you are going to lock it outside in SF. What's your budget?
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Old 06-19-12, 12:26 AM   #3
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Right now I'm thinking 32, maybe 35mm, tires which as far as I can find does not go well on a road bike.

Most of the low-end cyclocross bikes are around $1k, which is more than I thought so I guess that would be my limit. I think I'll probably be fine with Sora or Tiagra (I think that's the Deore equivalent) as far as components go. Edit: I am starting to realize $1k doesn't give me a lot of options...

One thing I am concerned about buying used is how do I differentiate a cyclocross bike or touring bike from a road bike? Is there anything that makes a them immediately obvious? The only road bike I've ever ridden I hated because it felt very impractical for riding in an urban area, but that very well could have been because it was a $20k racing bike.

Oh 8, 9, or 10 speed I do not care as long as it's not 7-speed freewheel.

Last edited by jsdavis; 06-19-12 at 01:35 AM.
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Old 06-19-12, 05:55 AM   #4
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Do I go by the top tube length or is it different on road sizing?
Drop bar bikes generally have shorter top tubes than straight bar bikes. Riding on the brake hoods is very common and that is several cm out past the end of the stem. So the top tube is shorter to bring the hoods into comfortable reach.

Touring bikes make great commuters. You could look at the Surly Long Haul Trucker which is pretty much a benchmark bike these days. Not sure the fattest tires it takes but it's gotta be at least 35 mm... with or without fenders is always an important detail.

But yeah if you have to park it on the street in a big city... some kind of beater hybrid might be more suitable. Something you can afford to lose!
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Old 06-19-12, 06:30 AM   #5
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Not 58 or 60 cm if you are 5' 8" tall. If you have a short torso, you'd be on a 54cm with a longer stem. If you have a long torso, you'd be on a 56cm with an appropriate stem.

My wife and daughter are both 5'8", with the wife having the long legs and the daughter having the longer torso. Their proper fit is as described above.

Try some road bikes at your local bike shop. Explain to them what you'd like to do - how you'll carry your commuting gear, whether you'll ride at night, how to mount fenders, etc. They'll steer you to what they have that can meet your needs.

Many folks like cyclocross bikes because of the braze-on mounts, wider tire clearance, cantilever brakes (room for fenders), but road feel. I've not ridden one, myself, though.

A touring bike will have wider ranged gearing, and will be very strong. The geometry will be more oriented to stability when loaded. Typically, gear shifters are on the bar ends. I have a tourer and it is very, very comfortable to ride. It's not nimble, though.

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Old 06-19-12, 10:05 AM   #6
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I am currently riding a Marin Muirwoods 29er with a 19" frame. How do I find the size I need for a bike with drop bars? Do I go by the top tube length or is it different on road sizing? My effective top tube is 605mm on my current bike but this puts me somewhere around 60cm for frame size which is the biggest frame from many manufacturers so this is not right. I am 68" tall.

I am using it for the street and commuting so there is no racing involved. The attraction of a cyclocross bike is that it looks like they accept 32mm, and maybe larger, tires so the ride should be more cushy. Even though many of them only have two chainrings and sometimes 48 as the largest, I think that might be ok since I'm stopping every few hundred feet anyway. That and San Francisco isn't flat.
My fiance's hybrid is a 19" and she's almost as tall as me (I'm 5'10" with shoes on, 30" inseam), and I ride a 53cm cross bike (Bianchi Volpe) and it fits perfect with the stock stem/rise. I also have a 54cm road bike that stretches me out a bit, but is still comfortable. If you're 5'8", I'd think you should start looking in the 52cm range, but anything from like 51 to about 54 may end up feeling okay.

**Edit** As an aside, I absolutely love commuting on my cross bike. Not as fast as my road bike, but it's a much smoother ride and I don't have to worry about my teeth rattling out of my head on rough patches. It's also a good climber/hauler, with a 50/39/30 triple paired with a 12-30 10spd.

Last edited by MattFoley; 06-19-12 at 10:08 AM.
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Old 06-19-12, 12:18 PM   #7
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I'm about your size and ride a 54" frame in both my "real" road bike and my cross/commuter bike. Both have an effective/horizontal top tube length of about 54.5 cm, with the cross bike having a little slacker seat tube resulting in a little shorter (1/2-1 cm) effective reach to the steer tube. I can easily make that up with either a little longer stem or (in my case) a handlebar with a little longer reach. But the bottom line is my guess would be a typical 54 cm frame. Try some though.

Go by the top tube length, not "frame size". Cyclocross bikes have a higher bottom bracket than road bikes, fwiw, which means for a given seat tube length, the top tube will be a little higher off the ground. But "standover" is not very important at all on a road or commuter bike, so as long as you can straddle it with maybe the crotch just brushing the TT, you'll be fine. An inch clearance is more than adequate, and looking for several inches like on a mountain bike is not what is done or needed with a road bike. I'm talking about clearance wearing your cycling shoes and bike shorts (which reduce dangling if you know what I mean).

Some differences between cross bike and typical road bike - just talking about the frames and forks.

Cross bike will usually (not always) have higher bottom bracket
cross bikes will be set up with clearance for larger tires. 32's and 35's are easy to fit.... road bikes are usually limited to 25's, MAYBE 28's for some frames
cross bikes often (not always) have eyelets that can be used for fenders or rear rack. Some road bikes do, but it's more uncommon these days, except for touring frames.
cross bikes are set up for cantilever or linear pull (AKA "V") brakes to accomodate the larger tires.
Cross bikes front forks are beefier
cross bikes front forks have longer legs (to accomodate the larger tires). Therefore, they tend to bring the front end up higher than a road bike with an identical head tube length. This is a factor if you're looking at head tube length as important.

Usually the rear dropout spacing is the same as a road bike - 130mm.

Usually fully built cross bikes come with a double crank with relatively small large ring (~44-48) because for actual cross use, you don't need the high end speed that you'd want on a road bike. They also might have a large range cassette and a MTB rear derailleur (or not). They use the same shift/brake levers as any road bike. If you are building up a cross frame, you can use any typical road components on it.

Built cross bikes usually come with somewhat heavier duty wheel sets - a little wider rim, maybe higher spoke count, although you can use any set of road rims you want on it, and can mount 32's (and maybe even 35's) on almost any road rim.

My Jamis cross frame (Nova Pro) is built up with a straight-on Ultegra road triple group that I had on hand, with the exception of the V brakes (which I use a Travel Agent for... if I had canti brakes, I wouldn't need them, my road levers would work fine). I have 32 summer and 35 winter tires on a set of Mavic Aksium rims I also had on hand, and they not only work fine, but they look "normal" too. I can install fenders and a rear rack to round off the commuter.

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Old 06-19-12, 12:25 PM   #8
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Stand over it, flat footed, and lift it straight up by the handlebars and the seat.

Some one else will see how far you can lift the bike off the ground,
to judge what the stand over height is, and whether it is sufficient..

Touring 2 " , off road , more..

the shop you are buying the bike from will help on that.
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Old 06-19-12, 12:31 PM   #9
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One thing I am concerned about buying used is how do I differentiate a cyclocross bike or touring bike from a road bike? Is there anything that makes a them immediately obvious?
The most obvious visual difference is that touring and cyclocross bikes generally have cantilever brakes instead of calipers, so the necessary posts will be found on the frame and forks. Typically, they'll also be built to take wider tires than racing-style road bikes, so you'll notice more clearance between the stays and tire/rim. Touring bikes will often have longer chainstays for pannier (bag) heel clearance and will have wider/lower gearing than road bikes. I'm not sure if this is a generality, but my cyclocross bike has slightly lower gearing than typically found on road bikes. Cyclocross bikes may also have more higher bottom brackets than road bikes, giving them a little more ground clearance.

MattFoley mentioned the Bianchi Volpe, which I think would be a fantastic fit for you. It's not really a pure cyclocross racer or a pure touring bike, but it's kinda like what you'd get if you cross-bred them. It's nimble, comfortable, and can comfortably carry a load if you mount racks on it. It also has a triple crankset, giving you low gears to tackle some of those San Francisco hills.
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Old 06-19-12, 12:55 PM   #10
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MattFoley mentioned the Bianchi Volpe, which I think would be a fantastic fit for you. It's not really a pure cyclocross racer or a pure touring bike, but it's kinda like what you'd get if you cross-bred them. It's nimble, comfortable, and can comfortably carry a load if you mount racks on it. It also has a triple crankset, giving you low gears to tackle some of those San Francisco hills.
And with that, I will show off

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Old 06-19-12, 09:12 PM   #11
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Stand over it, flat footed, and lift it straight up by the handlebars and the seat.

Some one else will see how far you can lift the bike off the ground,
to judge what the stand over height is, and whether it is sufficient..

Touring 2 " , off road , more..

the shop you are buying the bike from will help on that.
This is totally wrong. Standover is not a good way to fit a bike. It tells you very little about how the bike will feel when you are on the saddle.

Go to a real bike shop - there are a lot of good ones in SF. Freewheel and Valencia Cyclery on Valencia Street are good places to start. I think REI is carrying Surly now (check out the Crosscheck) and some of the Novara (REI in house brand) models might fit your criteria and budget.
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Old 06-19-12, 10:44 PM   #12
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This is totally wrong. Standover is not a good way to fit a bike. It tells you very little about how the bike will feel when you are on the saddle.
Based on what? Bikes that are designed for a certain height of rider have a pretty narrow range of top tube lengths. It's also easier to judge if a bike is close to the proper size based on standover height then on top tube length. If you can't stand over the bike, there's no sense in looking further into the bike because it's probably the wrong size. Also standover and 'size' are good places to start to separate the wheat from the chaff.

For some people, standover is particularly critical...even more so than top tube length. If you are 5' tall, finding a bike that you can stand over is often next to impossible.

jsdavis: I'd say that your 19" 29er is on the tall side for a 5'8" rider. I'm 5'11" and I ride a 19" 26er in a mountain bike. The larger wheels of the 29er must not give you much bail-off room for off-road riding. I'm not a fan of 29ers so I've not sized one but I'd suspect that a 19" 29er would be a tad tall for me.

I'd also suspect that the top tube is way too long for your frame...again,that's in the range of what I ride. I would suspect that a 15" to a 17" mountain bike (26er) would be closer to the proper size. That translates to a 54cm to 56cm road bike frame (19" to 21").
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Old 06-20-12, 10:03 PM   #13
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jsdavis: I'd say that your 19" 29er is on the tall side for a 5'8" rider. I'm 5'11" and I ride a 19" 26er in a mountain bike. The larger wheels of the 29er must not give you much bail-off room for off-road riding. I'm not a fan of 29ers so I've not sized one but I'd suspect that a 19" 29er would be a tad tall for me.
I don't actually ride my bike off-road. It has 29er in the name, but the tires that came with it are 700x42 and they are smooth rather than knobbies so "29er" is really only for marketing to differentiate it from the model with 26x1.4 tires. Also there is no suspension. As my bike is set up, the saddle is just about even with the bars. I tried the 17" inch model before I bought the 19" and the saddle ended being quite a bit above the bars. Pretty sure I had the 35cm seatpost extended to the maximum or maybe a bit beyond it too.
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Old 06-20-12, 10:36 PM   #14
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I don't actually ride my bike off-road. It has 29er in the name, but the tires that came with it are 700x42 and they are smooth rather than knobbies so "29er" is really only for marketing to differentiate it from the model with 26x1.4 tires. Also there is no suspension. As my bike is set up, the saddle is just about even with the bars. I tried the 17" inch model before I bought the 19" and the saddle ended being quite a bit above the bars. Pretty sure I had the 35cm seatpost extended to the maximum or maybe a bit beyond it too.
I think you are misunderstanding bicycle sizing. It matters little if the saddle and the handlebars are at the same height. If you want to ride that way, you can adjust it with changes in components. Having a lot of seatpost showing is normal for mountain bikes. I, personally, use 400 mm posts because a 350 mm is probably going to be too short. This, for example, is a properly sized mountain bike



The frame is meant to be small so that you have plenty of room to protect the dangly bits if you have to bail off. Notice that the handlebars and the saddle are relatively the same height, too. But this bike has proportionally longer top tube for a frame that has a 19" seat tube (actually virtual seat tube) than a road bike would because the 19" frame is designed for a larger person with longer arms and longer torso. In a road bike, I ride a 58 cm (23") bike to get a bike with a similar geometry. The 29er exacerbates the problem because the wheels are taller than a 26er so the frame should be even smaller to get the proper standover clearance.

Going on your 29er size of 19", you should be riding a 58 cm road bike but that is going to be way too big for you.
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Old 06-21-12, 01:07 AM   #15
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Been helping fit peeps on bikes for decades by having them try them on ..

rather than web data obsessing. good luck with your alternatives,,
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Old 06-22-12, 10:04 PM   #16
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Thing is I'd rather not drive all over the place to see if the bike fits especially those on Craigslist and I feel kinda bad when I go to the shop with no intention of buying.
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Old 06-23-12, 11:55 AM   #17
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Thing is I'd rather not drive all over the place to see if the bike fits especially those on Craigslist and I feel kinda bad when I go to the shop with no intention of buying.
Hate to break it to ya, but the only way to see if a bike fits is by actually riding it. I'm close to your height and it still took me a while to find the right bike, even after I figured out the correct frame size for myself before test riding. One company's 54cm size may be another company's 52cm size, for example.
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Old 06-23-12, 01:21 PM   #18
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Yeah, I was hoping that by using my top tube and stem measurement I could figure out what size I needed, but it does not seem to work that way since apparently the bike I'm riding is somehow too large for me anyway.
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Old 06-23-12, 05:54 PM   #19
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This is totally wrong. Standover is not a good way to fit a bike. It tells you very little about how the bike will feel when you are on the saddle.

Go to a real bike shop - there are a lot of good ones in SF. Freewheel and Valencia Cyclery on Valencia Street are good places to start. I think REI is carrying Surly now (check out the Crosscheck) and some of the Novara (REI in house brand) models might fit your criteria and budget.
You've got me scratching my head! I checked out fietsbob's response and can't for the life of me find anything wrong with it - let alone anything 'totally wrong'. You have to start somewhere and standover height is just about the only dimension on any bicycle that ISN'T adjustable. Saddle height and position and stem length and height all are.

So standover height is where I'd normally start myself and I work in a professional bike shop thats completely equipped for evaluating and fitting cyclists for touring, recreational cycling or competion. We're using a JUTEAU CANTIN® fitting system. Just curious - what do you use?
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