top tube length for short people
 

hi guys,

i've posted on here before. i'm looking for a new ride--a cross bike that i can use for commuting, group rides, maybe a little bit of light touring, etc--yes, the dreaded "all-around" bike. i don't have much room in my apartment or my wallet for multiple bikes. i've been riding track bikes for years now (my knees are begging me to stop), so this will be my first real geared bike in a long, long time (since before i stopped growing!).

my question is about top tube length. i'm very short (5'4") and female (so i have a short torso), and i've recently realized that, despite having worked in a shop for years and fitted many other people on many other frames, i've never really been able to find the perfect top tube length for myself. mainly because every track frame i've ever owned has been just-barely-small-enough-for-me so i've never had much of a choice. i'm always ridden with 80 mm stems and my seat all the way forward, you know? and even then sometimes it's been too long.

now that i'm looking at cross bikes, though, i seem to have a lot more options. top tube lengths seem to really vary on 47-49 cm bikes, depending on manufacturer, and i find myself unsure of just how long of a top tube i need. obviously much of this depends on preference, but i thought i would conduct a little informal poll.

so, a) for you 5'4"-ish people out there, what size TT do you ride comfortably? b) anyone have any tips for really finding the ideal TT length for yourself?

thanks in advance--

I'm a 5'4" male and I also was on a tight budget looking for an all around bike. I ended up getting the Mobobecane Fantom CX 49cm and I'm happy with it. Low priced, does what I need it to, thicker tires for off road but not too thick to give up road riding, the ability to throw on a rear and front rack(s), and lightweight and strong. I looked all around and some other brands that I considered was:
Darn, I just remembered I deleted the excel file after I bought my bike.

Jamis has some 48cm Cyclocross bikes that you might want to look into.

-Adam

Surly Cross-check is another one to look into.

Surly's tend to have really long top tubes last time I looked.

Ridley's tend to be shorter.

surly (and most other modern manufacturers) tend to make their top tubes long in comparison to the seat tube. one effect of this is to lower standover height on a traditional geometry frame, but maybe they're going off some average of human dimensions, i dunno.

my theory is that they do this because we (the short torsoed) can ride surlys with riser stems and long seatposts (aesthetics aside) but the short legged could or would not ride frames designed for people like us, as they'd have no seatpost showing and no standover.

due to the fact that i work in a shop (great deal on crosschecks) i bit the bullet and got a 54cm, and threw on a high rise stem and a longish seatpost. fits perfect, feels perfect, rides perfect, doesn't fit the mainstream standard of aesthetic beauty but hey, neither do i.

if the idea of a high stem and lots of seatpost is just unbearable, then your frame options are somewhat limited. i'd take a look at older road and touring frames, rivendell, and custom builders. ridleys have shorter top tubes as well, but tend to be more race oriented than all rounders.

+1. 48cm Jamis Nova Pro. 46cm Jamis Aurora Elite would be cool too if you wanted to do some light touring. I test rode the Jamis myself but I'm 5'6" and all torso. The top tubes on their cross frames that gave me some standover were just too short to fit me.

I just looked and the cross check and it goes down to 42cm then 46cm, 50cm, 52cm, etc.

I've only owned one "real" bike so I may not be as experienced as other but I know I'm short and it wasn't fun trying to find something that half way fitted!

-GadgetAdam

When the frame gets below a certain size, it doesn't make sense to use 700c wheels.

Desalvo, for example, uses smaller wheels for the frames that are smaller than 50cm. Terry does the same.

Tsk tsk. Do a ground-up fitting for yourself, and find your ideal frame dims. I assume your shop has something like bikefitting.com or equivalent?

thanks so much, guys. the bikes i've been looking at:

specialized tricross comp
soma double cross
kona jake the snake
surly crosscheck
jamis nova

i have noticed that the top tubes are longest on the soma (42 cm - 52.3 TT) and the surly (42 cm - 52.2 TT)...unfortunately, those are also the bikes with the lowest standover heights. the tricross has a shorter top tube (51.5) but a higher standover. you just can't win!

i am definitely a proponent of 650 wheels on smaller frames--i don't know why more manufacturers haven't caught onto that yet.

unfortunately, i don't work at a shop anymore - haven't in a long time. but i am thinking i will go into a shop next week and get measured.

i wouldn't worry too much about standover. i was just bringing it up as it seems to influence a lot of people's decisions but standover itself doesn't affect the ride at all. i really only factor it in when fitting a bike for someone who's really not comfortable riding.

http://zinncycles.com/fitsystems/DimensionPage.aspx
http://zinncycles.com/fitsystems/default_ie.aspx

When I was shopping for a bike, the recommendations that came from measuring myself and using the Zinn widget were almost exactly the same as the recommendations that came from the bikefitting.com work-up I got at the bike shop.

For CX and general purpose use, an MTB wheel makes more sense than 650c. I havent seen any sporty 26" CX bikes but someone must make them.
TT is only one component of reach, you also have to factor in the seat-tube angle which is usually steep so small riders can reach long cranks.

I'm stuck with short legs but I agree that for most this is an overrated measurement. Concentrate on the cockpit length and the most influential item on that is effective top tube length. A 9cm stem and a 535mm top tube of my Soma Double Cross is my ideal road setup at 5'6". It's a little long for cross but I make it work. After all, I only do a few cross races in the fall but log 2000 annual commuting miles with it.

Seat tube angle matters, but so does head tube angle, and more importantly, IMHO, is head tube LENGTH and fork length!!!

What worked for me was a Performance Scattante XRL Cross. It took forever to find, but for the first time in my life I found a cross frame that lets me use a 110mm length stem. I got the 54, which has a 54 cm effective top tube and a 52 cm C-T seat tube. It's awesome.

Yes. They do matter. Sometimes it feels like much more but head tube angle typically changes cockpit length by a few mm per degree, seat tube angle typically changes cockpit length by a few mm per degree, head tube and fork length typically change the cockpit length by a few mm per 20mm.

The effective top tube and choice of stem change the cockpit length in much larger increments.

I'm a mathematician. I've done the calculations.

Let's assume a 73deg head angle. Given the same effective top tube, fork, and stem setup, a unit reduction in head tube length moves the handlebars cos(73)=.3 units away from the saddle in the horizontal, and almost an entire unit (sin(73)=.95) away from the saddle in the vertical dimension. That drop of the bars is subjectively felt as lengthening the reach, because you have to bend over more.

Yes you can kluge together a stem setup that makes up for this, but when you get really far away from the original setup, the handling of the bike changes.

In other words, the vertical size of the bike influences reach, as well as the horizontal size of the bike.

I agree that head angle and seat angle don't make much difference, especially since they are very similar across different bikes.

I'm going to go out on limb here and suggest looking at a Rawland 650B frame. 700c wheels have a ton of overlap in the 52cm frame that I ride, and I suspect it will be much worse for you.

Seat tube angle and head tube angle together do make a difference in the measured top tube length, but your butt doesn't know anything about what angle the seat tube is. If you get a new bike that has a steeper seat tube (as many smaller frames do), you don't gain anything, because once you position the saddle where you need it, the seat tube itself becomes irrelevant. So it's not really top tube length that matters, but what overall cockpit length you end up with once you have positioned your saddle and your handlebar.

By the way, there's absolutely nothing wrong with an 80 cm stem on a small frame of say 50 cm or less. If you stop to think about it, it's very proportional to the size of the frame. Of course, if the 80 cm length angles up, then you actually have an effective stem length that is shorter than 80 cm (in that case, you might need a 90 cm stem).

yes, 26" would be better suited in some ways - but my reason for preferring 650c over 26" is that i do a lot of road riding, too (thinking of doing a sprint tri in the fall, actually--though i'm definitely not a triathlete) and so i'm not really interested in a beefier rim.

what top tube length? personally, i would suggest a top tube length equal to that of you roadbike...maybe a smidge shorter if you want.

done.