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  #1  
Old 04-13-2023, 11:46 PM
Shane4XC Shane4XC is offline
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Sizing Help

I’m looking to purchase a bike for my partner and she’s around 5’7. Looking at a particular bike, the store page recommends 5’8-5’10. However, it lists the attached geometry.

Since the top tube is listed as 520mm, this would actually be a 52cm frame correct? Which I imagine could be closer to her fit.

Are there any measurements we should take of her to see if they line up with the geometry of the bike?
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  #2  
Old 04-14-2023, 06:56 AM
Peter P. Peter P. is offline
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A 52cm top tube for a 5'7" rider? The bike's too small.

Frames are not specified by top tube length. They are typically spec'd by seat tube length. Because many bikes now have sloping top tubes, the length of the seat tube spec'd is a "virtual" size, meaning if the top tube were parallel to the ground, where it would attach to the "virtually" extended seat tube would be the frame size.

Your 5'7" friend would fit a bike with a 54-56cm "virtual" or "effective" top tube length. Try bikes with that spec.

By the way, if you have to ask this question I'll assume you don't have a lot of experience sizing bikes. In that case, if you're thinking of buying the bike on-line, DON'T. She should try bikes in person to see which bike fits best. Bring some allen wrenches with you to adjust the seat height, etc. during road tests to get the best feel of bike fit.
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  #3  
Old 04-14-2023, 01:09 PM
Shane4XC Shane4XC is offline
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Quote:
Originally Posted by Peter P. View Post
A 52cm top tube for a 5'7" rider? The bike's too small.

Frames are not specified by top tube length. They are typically spec'd by seat tube length. Because many bikes now have sloping top tubes, the length of the seat tube spec'd is a "virtual" size, meaning if the top tube were parallel to the ground, where it would attach to the "virtually" extended seat tube would be the frame size.

Your 5'7" friend would fit a bike with a 54-56cm "virtual" or "effective" top tube length. Try bikes with that spec.

By the way, if you have to ask this question I'll assume you don't have a lot of experience sizing bikes. In that case, if you're thinking of buying the bike on-line, DON'T. She should try bikes in person to see which bike fits best. Bring some allen wrenches with you to adjust the seat height, etc. during road tests to get the best feel of bike fit.
Thank you! I thought their recommended was way off, trying to avoid the whole trial and error of bike fit which I went through

Unfortunately I traded in a bike frame for store credit with the pros closet, so I am locked into their online bikes. But I’ll target a 540mm top tube, and hope for the best.
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  #4  
Old 04-17-2023, 12:35 AM
giordana93 giordana93 is offline
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I agree with Peter that a 52cm top tube is probably too short, but I also think anything more than 53.5-54 might be a little long. Here's why. I ride a classic 52 even though I'm 5' 9" because I have short legs. Typically a classic 52 has about a 53.5cm top tube and a seat tube angle around 73.5. This works pretty well for most people who fit a 52 and that would normally include folks around 5'7". It even works for me, and remember, I have a long torso to go with those short legs, and I have a pretty aggressive position. Now I do have a slightly long stem at 110, but there is no way I would ride a 56cm top tube. Since we are dealing with a female rider, she has a good chance of having more legs than torso, suggesting a shorter top tube, not longer, than the norm. If you are stuck with pro's closet stock, I would aim for a "size" 52 or 53 (that would be the virtual SEAT tube #, typically a "small" for many manufacturers), probably Endurance geometry (which is closer to a "womens specific design" based on longer leg to torso ratio than average male, as well as generally less "aggressive," meaning taller headtube, shorter top tubes). Before starting confirm that she does not have outside the norm numbers for arm/leg/torso lengths, and why not just do an inseam measurement to get you in the right ballpark. The old Lemond formula of frame size = 2/3 of cycling inseam (not jeans inseam) is still useful for getting within a couple cm. Also consider intended user: fitness type looking to get fast(er) or someone who wants a quicker road bike but more laid back/touristy bike fit. It makes a difference. Unless she has crazy long legs, I would not get a seat tube angle less than 73.5, unless there is a zero setback seatpost, but that's starting to get technical for an internet fit.....

Last edited by giordana93; 04-17-2023 at 12:39 AM. Reason: typos
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  #5  
Old 04-17-2023, 10:02 AM
Alistair Alistair is offline
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I'm 5'7" and typically ride a "52cm" road frame with reach in 370-379 range and ETT in the 530-540 range. A 54cm frame might work, but might be a hair large, depending on actual dimensions and flexibility.

And you have to be careful looking at frame sizes - they're mostly meaningless (for comparing across brands). My All-City is a 49, but with geo that's closer to most 52cm frames. And my Checkpoint is a 52, but with a 55.5 ETT and reach is 39.9, but it's designed for a shorter stem and short reach bars.

Last edited by Alistair; 04-17-2023 at 10:04 AM.
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  #6  
Old 04-18-2023, 05:42 AM
Ramshackle Ramshackle is offline
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I'm 5'7" and ride a 49cm Roubaix with a 25 deg offset seat post and a 100mm stem. I've owned 54cm, 53cm, 52cm and 51cm bikes, all of which had a reach a little too long for me. It all depends on the physiology--long arms, short arms, short legs, etc. I put stock on the bike feeling right rather than on bike sizes. I also prefer starting with a smaller frame and making it larger in the ways that matter for me.
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  #7  
Old 04-18-2023, 10:56 AM
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fourflys fourflys is offline
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Quote:
Originally Posted by Peter P. View Post
Your 5'7" friend would fit a bike with a 54-56cm "virtual" or "effective" top tube length. Try bikes with that spec.
.
wow, I 100% disagree with that as someone who rides a 54cmish TT bike and I'm 5'9".. it depends on leg vs torso proportions, flexability, arm length, etc..

the rider in question needs to ride the bike for 20min or so and see if they feel like they are reaching.. unless they have unusally long arms for their height, my bet is they will.. esp at the 56 end.. and then there is the leg length concern for someone who is 5'7".. again, unless they have long legs for height (which would mean short torso), then they will have a tough time getting over the bike and the seat will so low as to negate any built-in seat post tolerance, etc that might be there.. (basically what Giordana said above)

The only reason someone who is that height would ride a 54/56 is if they needed the bar height and there would have to be a LOT of concessions on the other bits like stem, etc.. at least IMHO as someone who has do a LOT of research on this and trial and error..
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Last edited by fourflys; 04-18-2023 at 11:45 AM.
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  #8  
Old 06-08-2023, 03:41 PM
PortlyPuncheur PortlyPuncheur is offline
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I second Fourflys. I am also 5'9. I ride effective top tubes in the 540mm to 545mm range.

If anything I would suggest 520mm MIGHT be too long. Many female riders struggle with legs being much longer than torso (and arm) length, so sometimes a smaller reach:stack ratio is needed. But we're all individuals, not averages, so all you can do is measure and/or get a fit.
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  #9  
Old 06-09-2023, 06:39 PM
Upcountry Upcountry is offline
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Quote:
Originally Posted by Peter P. View Post
A 52cm top tube for a 5'7" rider? The bike's too small.
I'll third the sentiment that I couldn't disagree more... Especially given its a woman. Women tend to have shorter torsos and arm length. Unless you're a fan of the 80mm or shorter stem on a road bike, or she has significantly longer arms than most, I wouldn't even consider anything longer that 520mm in the top tube.
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  #10  
Old 06-09-2023, 09:51 PM
htwoopup htwoopup is offline
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As others have said…doing this totally online is a recipe for not getting it right. But I will throw in my experience. Male. 5’ 6”. Wear long sleeve dress shirts with sleeves in a 32”. A Trek Crockett with a 52 top tube was a full size too big for me. It had a 379 “reach” and was supposedly right for my height and inseam etc according to their “fit guide”. But it was too big.

I have 4 custom bikes where I was measured by the builder…including a carbon bike made in Texas and a trip out to The Barn in Pa. Just throwing that out to put that these were expert fits (for me not your friend).

Every bike that has been made to measure for me has a “reach” of 361-364.

So, I am going to guess that the 52 you are looking at may not be too small. It might even be a little big.

Maybe try a cheapish quick fit (nothing over the top) and pay for the shop’s time so you aren’t stiffing them and get some contact points. Then work with Pro’s C on the phone (they are ok with that) to find something that would work.

I am going to say this and say that I do not mean the double entendre and I am just trying to explain cycling purchases with friends. In my experience with girlfriends and then a practice wife and a final wife….if the fit isn’t right she won’t ride with you…in cycling too. But in cycling sometimes a bike that is too small is better than one too big if you want to have your partner enjoy the ride and want to keep doing the sport together.
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Last edited by htwoopup; 06-09-2023 at 10:06 PM.
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  #11  
Old 07-09-2023, 10:20 AM
vtsnowplow vtsnowplow is offline
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Not an expert, but I an 5'7" and have been riding a 52cm frame. most 54cm frames that i have ridden feel a bit too stretched out, even when using a shorter stem.
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  #12  
Old 07-25-2023, 05:45 AM
wackyjack wackyjack is offline
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Out of my experience, I wish I had a proper bike fit on a Retul before buying anything. Lucky me, I got the size of my bike just about right, so that changes could be achieved by cheap items like stems and posts.
I second opinions of members above: it all depends on body proportions and overall flexibility/mobility of your partner.
If I'd be choosing the bike for my partner, I'd go with something quite upright and the smallest size that would fit her. Over time you can ditch spacers under the stem to stretch her on the bike, if that's needed.
Last thing: couples usually ride slower than solo, so I'd prioritise the comfort over the flat out speed.
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  #13  
Old 07-25-2023, 10:53 AM
Alistair Alistair is offline
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LOL.

I'm 5'7", male, short torso, and usually ride a 52cm frame, which generally means an ETT in the 53.5-54cm range and reach in the 37.5-38cm range. Usually with a 90mm stem.

This despite many size guides (from manufacturers) putting me on a 54cm frame.

Anyways, I'd guess this frame is a hair too short, unless she's all legs or has terrible flexibility. But it's hard to tell without knowing her previous bike sizes.
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