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Which paramater matters more in deciding road bike size; total length or inseam?

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Which paramater matters more in deciding road bike size; total length or inseam?

Old 12-01-15, 09:47 AM
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Akram
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Which paramater matters more in deciding road bike size; total length or inseam?

I have an inseam of 80 cm and my height is 178 cm. According to most online charts, I would need a 54 cm based on my inseam and a 56-57 cm based on my height. So which road bike size should I be looking for? What's the difference between riding a 54 and a 56? Thanks.
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Old 12-01-15, 09:50 AM
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Originally Posted by Akram View Post
I have an inseam of 80 cm and my height is 178 cm. According to most online charts, I would need a 54 cm based on my inseam and a 56-57 cm based on my height. So which road bike size should I be looking for? What's the difference between riding a 54 and a 56? Thanks.
Why not try riding the bike and see what actually fits best? A size chart is good for getting you in the ballpark, but it's just a starting point.
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Old 12-01-15, 10:13 AM
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Well you want to have enough standover clearance so you don't crush your nuts, it really depends on the geometry. If the frame has a sloping top tube you could probably get away with a large. If it has classic geometry you may want a 54 with a longer stem, it depends on the top tube length. But FWIW my inseam is longer than yours (84) and we're the same height and I can fit anything from a 54-57.

This is my 54 and I use a 120mm stem. I do set my saddle about 2cm lower than "recommended".

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Old 12-01-15, 10:23 AM
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I would say that reach (to the bars) and your weight balance on the bike are far more important guides to fit than height or leg length. BSY's suggestion to try out sizes is best, but if you want to learn about fit, roll up your sleeves and jump in. It's not super hard or arcane, bit does take a more sophisticated view than inseam and height.
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Old 12-01-15, 10:23 AM
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Originally Posted by Akram View Post
I have an inseam of 80 cm and my height is 178 cm. According to most online charts, I would need a 54 cm based on my inseam and a 56-57 cm based on my height. So which road bike size should I be looking for? What's the difference between riding a 54 and a 56? Thanks.
My advice is to stop looking for easy answers and go to your local bike shop and see what fits.
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Old 12-01-15, 10:34 AM
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Effective top tube length is more important than standover height.
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Old 12-01-15, 10:37 AM
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Originally Posted by wphamilton View Post
Effective top tube length is more important than standover height.
Tell that to your nuts.
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Old 12-01-15, 10:39 AM
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Originally Posted by Lazyass View Post
Tell that to your nuts.
I ride with my feet on the pedals, stand with one foo on the ground. Standover is almost irrelevant, completely irrelevant when you're talking 2 cm clearance vs 1 cm
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Old 12-01-15, 10:50 AM
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Originally Posted by wphamilton View Post
I ride with my feet on the pedals, stand with one foo on the ground.
That's fine for you, but most people probably put both feet on the ground at some point. It's not very relevant with compact geometry. The way you used to get sized for a bike was to stand over one. The one that gave you an inch or two of clearance was what you got. May have had to swap stem lengths by a 10-20mm, no big deal. Bars were set a couple of inches below the saddle at most. About a fistfull of seatpost showing. Simple and it worked. And you didn't hear too many riders complaining about neck, foot, hand pain or any other kind of pain like you see today.
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Old 12-01-15, 10:58 AM
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Originally Posted by Lazyass View Post
That's fine for you, but most people probably put both feet on the ground at some point. It's not very relevant with compact geometry. The way you used to get sized for a bike was to stand over one. The one that gave you an inch or two of clearance was what you got. May have had to swap stem lengths by a 10-20mm, no big deal. Bars were set a couple of inches below the saddle at most. About a fistfull of seatpost showing. Simple and it worked. And you didn't hear too many riders complaining about neck, foot, hand pain or any other kind of pain like you see today.
So it's not very important to be precise on standover, and your adjustments are relative to the top tube length.

Your "one or two inches" leeway in the top tube height is more variable than the difference in the frames that OP is looking at.
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Old 12-01-15, 11:09 AM
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Originally Posted by BoSoxYacht View Post
Why not try riding the bike and see what actually fits best? A size chart is good for getting you in the ballpark, but it's just a starting point.
Originally Posted by dr_lha View Post
My advice is to stop looking for easy answers and go to your local bike shop and see what fits.
Exactly.

I've read numerous posts here about people with two bikes with "the exact same specs" yet one feels better than the other.

The numbers don't lie, they just don't tell you everything...
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Old 12-01-15, 11:18 AM
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I go by reach. Other "experts" might disagree.
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Old 12-01-15, 11:29 AM
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I'm agreeing with those that are saying top tube/reach is the most important number. I'm 5'9ish with a 33" inseam and most people and charts and calculators try to put me on a 54. But since my torso is short, the reach was always longer than I want. I'm a noob, and my first bike was a 54, I had to shorten the stem to the point where the handling was getting twitchy. My second bike was/is a 52, and it's PERFECT, and I knew it the first time I sat on it.

(tl;dr: IMO, it all depends on the length of your torso, but you won't really have a good sense of that until you go ride various sizes and geometries.)
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Old 12-01-15, 11:32 AM
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Originally Posted by rmfnla View Post
I've read numerous posts here about people with two bikes with "the exact same specs" yet one feels better than the other.
And most are probably newbs who can't tell you why one feels better. If the specs are the exact same then they're the exact same. Bike fitting isn't rocket science, but it's bizarre how complicated everyone has made it become today. These ridiculous geometries, compact frames, comfort bikes, two foot tall headtubes, ect sure haven't helped.
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Old 12-01-15, 12:15 PM
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Originally Posted by Lazyass View Post
The way you used to get sized for a bike was to stand over one. Simple and it worked. And you didn't hear too many riders complaining about neck, foot, hand pain or any other kind of pain like you see today.
Yes, that's how it used to be 30-40 years ago, but even if it is true there were few complaints about discomfort, which may or may not be true for a variety of reasons, there are more cyclists riding further, so the likelihood of both complaints being created and complaints being heard, is necessarily higher.
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Old 12-01-15, 12:40 PM
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Originally Posted by chaadster View Post
there are more cyclists riding further
There is?


Originally Posted by chaadster View Post
so the likelihood of both complaints being created and complaints being heard, is necessarily higher.
Seems the complaints have risen as the bar heights have got lower, and as people have gone to smaller frame sizes.
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Old 12-01-15, 12:54 PM
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Originally Posted by Lazyass View Post
There is?




Seems the complaints have risen as the bar heights have got lower, and as people have gone to smaller frame sizes.
Yes, trips are WAY up in the USA.

I can understand how to you it may seem bar heights are down and frames smaller, and why you might assign those factors causation for complaints, but I would challenge the veracity of all those assumptions. Are bar heights generally lower? Are people generally riding smaller frames? Do smaller frames cause discomfort? I just don't know if any of that is true, and to the extent we do see lower bars amongst the roadie set, whether it's statistically meaningful.

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Old 12-01-15, 02:04 PM
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I'm the same height at the OP but with shorter legs. I could fit a 56cm but usually prefer a 54 with a longer stem. YMMV. (Go to a bike shop and test ride a bike, or better yet, get fitted)
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Old 12-01-15, 04:44 PM
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Originally Posted by chaadster View Post
I would say that reach (to the bars) and your weight balance on the bike are far more important guides to fit than height or leg length. BSY's suggestion to try out sizes is best, but if you want to learn about fit, roll up your sleeves and jump in. It's not super hard or arcane, bit does take a more sophisticated view than inseam and height.
I agree that reach is going to be the most important factor here. But height and inseam are relevant to reach, i.e. short legs, for your height means long torso, and indicates that you might want to favor a bike with a longer top top tube, i.e. more reach.

OP's inseam of 31" (assuming that's a cycling inseam) for a height of 5'10" makes me think he's likely to want to go with the larger frame.

But again its a guess based on limited information, which needs to be tested by actually trying the bikes.
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Old 12-01-15, 05:06 PM
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Originally Posted by Akram View Post
I have an inseam of 80 cm and my height is 178 cm. According to most online charts, I would need a 54 cm based on my inseam and a 56-57 cm based on my height. So which road bike size should I be looking for? What's the difference between riding a 54 and a 56? Thanks.
How do different sized bikes feel when you ride them at the LBS?
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Old 12-02-15, 02:47 PM
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Thanks everyone for in the invaluable feedback. I tried a 54 and a 56 and didn't notice much of a difference. I am new to riding a road bike and wanted to get feedback from experienced cyclists.
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Old 12-02-15, 03:37 PM
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Originally Posted by Akram View Post
Thanks everyone for in the invaluable feedback. I tried a 54 and a 56 and didn't notice much of a difference. I am new to riding a road bike and wanted to get feedback from experienced cyclists.
If you're not telling a difference between a 54 and a 56, you might want to ride them some more. One should fit you far better than the other.
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Old 12-02-15, 04:22 PM
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Originally Posted by bbbean View Post
If you're not telling a difference between a 54 and a 56, you might want to ride them some more. One should fit you far better than the other.
I'm not sure about this. I can easily get comfortable on a range of sizes depending on the manufacturer's.

I Share a second bike with my 13 year old who is a bit shorter than me. It's a Trek Madone 2.1 56cm. I could easily ride a 58 and he could easily be on a 54cm. We chose a 56 because he is growing and it works well for me with a few minor adjustments. The 56 has more seat post showing where the 58cm would have less. But with a quick change of stem and spacers I can make either size work.
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Old 12-02-15, 04:26 PM
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Originally Posted by bbbean View Post
If you're not telling a difference between a 54 and a 56, you might want to ride them some more. One should fit you far better than the other.
I don't think it's uncommon for a new rider to not notice much of a difference in a 2cm variation.
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Old 12-02-15, 04:28 PM
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Me? Top Tube Length ..
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