vpr80

I tried to check the spec sheets to figure out what size frame I need, but I don't seem to fit and apparently I have short legs. So I am 5'9" with a 30.5" inseam (flat on floor, no shoes), what size frame do I need? More importantly, since I seem to be taller on top than on bottom, what length top tube will work for me?

Thanks

urbanknight

Try this, but don't do it alone. Have someone take the measurements or you will get some really odd results.
https://www.competitivecyclist.com/za...LCULATOR_INTRO

Although sizing based on inseam and height alone is not accurate, you will probably fit somewhere around a 53/54cm frame depending on its geometry.

vpr80

i figured that since my legs are a bit short for my torso, i should get the 54cm (vs 52cm which i size upto) to get the correct distance reach to the bars

urbanknight

You are most likely correct. I am 5'11" with a 30" inseam (and you though you had it bad) and I ride a 55. But there are other factors in there. I have long thighs and short shins, so I also look for a relaxed seat tube angle and not necessarily a long top tube. That fit calculator really does give you a good idea on where you stand since it takes many factors into account.

vpr80

ohhh wow and i thought i was funny looking

thanks a lot for the link, I will try it tonight....my wife will think i am out of my mind

urbanknight

Welcome to the club. Hopefully you don't need to buy and sell 2 frames to get it right like I did. Now my wife thinks I'm crazy and stupid.

Tunnelrat81

I'm about 5'8.5" with a 30 in. inseam...and I ride a 54 Trek 2300. I recently went to a pro fitter for his services and ended up with a a 120 mm stem, up from the stock 100 mm stem. Was an eye opener. I'd wondered if I should be on a smaller 52cm frame before, but realize now that although that size would fit my legs great, the TT might require a stem longer than a 120, which is crazy. Good luck, and as a side note, if you have the time and an extra bit of money, ask your LBS for referral to a Pro fitter who can measure you and size you up BEFORE you get a bike....then you'll have hard numbers to work with while frame/bike shopping. My basic fit by a highly experienced fitter cost me 65 dollars. Well worth the experience and changes.

-Jeremy

stapfam

5'6" with a 30" inseam. I ride Giants with the compact frame. (And a Boreas Aluminium conventioanl frame in 51)

The XS is up to the equivalent of a 47 to 51 and the S is equivalnt of a 51 to 54 I fall right between the sizes as the XS and I have the seat tube way up high- even for a compact- and the S seems more suitable sizing except I fitted a shorter bar stem. The S is also ridden by my son in law (5'10") with the only set up being to raise the saddle a bit and push it right back on the rails.

So look at compact frame bikes. Not everyones choice for us shorter persons (Or those with short legs) they work.

And top tube length is down to preference. It can be adjusted on fit by bringing the saddle rearwards or lengthening the bar stem -- but not by much.

urbanknight

^ The only advantage to having a compact frame for someone with short legs/long torso is to get more standover height. It won't have any affect on the RIDING fit of the bike, which is the crucial fit.

Also, when you start going outside the normal proportions (I'd say 5'6" with a 30" inseam is normal) things like top tube length and seat tube angle become more crucial and less preferential. I, for example, have to have a seat tube angle of 73.5 degrees or less, or I won't be able to get the seat far enough back, even with a 25mm setback seatpost!

alanbikehouston

The best way to fit a bike is with a test ride, not an internet forum. Select a bike. Stand over it flat footed with your belt buckle an inch behind the stem. Ideally, the top tube should lightly brush against your jeans. If the top tube is PRESSING into your crotch, the frame is too tall.


Then put the saddle at your preferred height, and raise the bars so the highest portion of the bars is one inch or two inches lower than the top of the saddle. Take the bike for a test ride..you need to ride at least fifteen minutes to get the feel of the bike. If that bike does not feel "right", try a frame that is one size smaller.

artifice

+1

And, there's also probably more than one answer to the "perfect" size, which can be achieved by a proper fit- proper adjustment of seat height, stem, etc.

AnthonyG

Getting a good fit for you won't be an easy process. To start with I think that you need to fit your legs first and then your reach.

I'm inclined to say buy a smaller frame to fit your legs properly and then fit a longer stem to accommodate your reach although its NEVER this simple.

OK, I think you need to use cranks no longer than 165mm based on your inseam of 30.5" or 775mm. I think you could even use shorter cranks than this (down to 155mm) but 165mm will do and they are available easily. Now most smaller size frames have steep seat tube angles which WILL be too steep so by the time you fit a rear set seatpost to compensate you will have effectively stretched out the top tube length so infact it may be right. If you still need more length fit a longer stem. Its not a big issue.

Now there is a place for a larger frame. If you want or need a taller head tube. The smaller frame will have a shorter head tube although if your trying to stretch out you can stretch further forward or further down. Still with me?

Its complicated. Getting a custom frame built for you using 165mm cranks would be ideal but more expensive. To get an off the shelf frame to work for you is possible but will take some fussing around.

Anthony

vpr80

yes i definitely follow, but being a new rider and not wanting to spend a ton of money on my first bike, i pretty much need to figure out approx what size i need and get a factory bike. however, i will definitely keep the crank advice in mind and might swap it out because most 54cm bikes seem to have 172.5 cranks. also, no matter what bike i get, i was going to go to my local LBS to get me fitted properly

DirtPedalerB

I'd try a compact frame, less standover worries and you can get the reach you want

AnthonyG

What brand are you looking at?

I remembered looking at the geometry of Trek bikes for someone else and what I noticed was that the 52cm frame WASN'T really 2 cm smaller than the 54cm. The true differences in size was minimal and I thought that the 54cm was by far the best option. The 52cm was simply modified to look smaller with a steeper seat tube angle but was pretty much the same. The 52cm may have more standover clearance but honestly, in my book if you can stand over the tube, even if its touching thats enough.

Post the geometry of the bikes your looking at and I will see what differences between them I can find.

Anthony

scirocco

The best way to fit a bike is to visit the internet and find out the issues with fit and the things to consider (as the OP is doing). What types of geometry and sizing might suit the riding style, intended use and rider flexibility. Understand the constraints on saddle-bar drop that come from relationships between head tube and top tube lengths in the bikes manufactured nowadays.

THEN select a bike from a position of understanding, not based on some bike shop employee's sales target.

THEN take a test ride.

vpr80

I am looking at a LOOK 555 today in size Medium (53cm). I can't seem to find the geometry of it anywhere though, but I will post it as soon as I find it.

vpr80

Alright found it....see attached...

AnthonyG

What I can tell from this geometry is that the 51cm frame is pretty much the same as the 53cm frame but with a steeper seat tube angle which is useless and only done to make the top tube look shorter on paper and a shorter head tube which is the only real difference. The seat tube angle on the 53cm AND 55 cm seems a fraction steep at 73 3/4 º but only a fitting will tell if this works for you or not. This steep seat tube angles seems to be a modern trend however and most bikes will be the same. Some will be worse.

As I said I think you will be better off using 165mm cranks and with these cranks you will want a more relaxed seat tube angle than if your fitted for say 172.5mm cranks. We can compare the fitting differences between one frame and another based on the geometry but somewhere we will need to know what your actual fit requirements are.

Anthony

vpr80

two questions:
1) can I just swap out the crank arms or do I need to change the whole assembly with the ring and BB?
2) would a cannondale synapse carbon 5 be a better fit?

CdCf

It seems to me that all these fitting methods, even the ones that take your full body measurements, assume that men have an inseam/height ratio of 0.46-0.47. That's likely the reason for the extremely poor fit I got when I built a road bike last year. I'm extremely stretched out, and I suspect it's because I have long legs relative to my height, which means a short torso. And it's really torso length that decides what frame size you need.

My inseam/height ratio is over 0.49 (~88/178 cm). The non-legs part of my body is thus 90 cm, and using a ratio of 0.465, I get a corresponding inseam of ~78 cm, and that makes an inseam-based fit calculator suggest a frame size of around 52-53 cm. Which is the size I now have ordered.

AnthonyG

When it comes to crank interchangeability if its the same brand it should just swap easily but a different brand will need the BB changed as well. This isn't that hard to do though.

As to whether the Cannondale is a better fit I don't know because I don't know what your actual fit requirements are. What I can say is that the Cannondale has a slightly steeper seat tube angle which my opinion is is a backward step. Based on the numbers it may be a fraction longer in the TT but then again the head tube angle on the Cannondale is slightly more relaxed which stretches out the front-centre distance which is what I'm trying to assess. The Look is closer to classic geometry.

Anthony

AnthonyG

I've just noticed that your looking at a Giant TRC C1. I have to say that I think the Giants geometry is better. Classic 73º/73º geometry and its a fraction longer in the top tube which is what you think you need although some of this is because of the more relaxed seat tube angle but thats all good.

Anthony

roccobike

I'm 5'9" with a 29.5" inseam. Actually 30.5" is normal for our height. I've really got the short leg problem. I ride a medium frame Giant OCR-C and a 54cm, Medium Specialized Allez. I ride 52-56 cm framed 1980's older road type frames.
I ride a 17" mountain bike frame, Specialized mtb frames fit me perfectly.
I would think you would ride the same sizes, possibly a little larger.

BHBiker

54cm