i'm in tokyo right now and i've been searching for a keirin frame. i'm 5'10" with a 33" inseam and most fitting guides point me to a 55/56 c-t frame with a tt around 55. i line up perfectly for a 57 c-t frame on dave moulton's table.
i found a nice 56.5c-t araya on e-framebank but it has a 57cm top tube length. this seems like a really long tt for me. the next closest frame to my size is a 54.3c-t, 54tt vivalo. both have seat tube angles of 76* i've scanned the forums and most people recommend a track bike slightly smaller than normal road bike size.
should i go for the smaller bike and compensate with a longer stem or get the bigger bike and hope i'm not too stretched out in the drops?

Go for the 54.

+1

-1...I got a kerin frame that was slighly too small for me (55ish vs normal 56 track size) and immeadatly regretted it. In order to be comfortable for long periods I would have probably had to put risers on it and I just refused to do that(argument was soon ended by a toyota tercel). Too small is no fun.

yeah, but alaska says he's 5'10" and when for him that points to a 55cm,
then a 54cm can be compensated when the seat is set 5mm to the back
and the stem is 5mm longer ...or just a stem with 1cm more. you're right
rvabiker, too small is no fun, but too big isn't as easy to correct.

besides, since when was a track bike with drops designed to be comfortable
for long periods of time?

i'm a little hesitant to go big because the bike i have now is close to being too big for me and it rides like a boat. it seems like too small offers more options and would give me a better possible fit. i will be using it for school commutes, about 3.5 miles, but nothing much longer.

I didn't read he was 5'10"...I rescind my statement. Go with the 54.

The general story about sizing a track frame with a threadless stem is to go a centimeter or so smaller than your road frame. However, this is a theory drafted by road riders. You have to remember that if you want a properly fitted track frame, you are always going to be in the drops, which in effect means you may need a slightly larger frame than on the road, all depending on your flexibility. With a threaded headset and quill stem, you have a higher stack height than for threadless, offset by the option of using a downward sloping track stem. The net plus-or-minus difference for the threaded headset less any downward stem slope depends entirely on the stem. Plus, don't forget that track bars tend to be significantly deeper and have significantly greater reach compared to most road bars. In short, there are probably more things causing you to want to go to a slightly larger frame.

Plus, if you look at keirin riders in Japan, they tend to fit their frames in the sizing styles of the 70's, i.e., with relatively little seat post showing. Again, you get this with a slightly larger frame.

As for top tube length, again you are typically using handlebars with greater reach. And you may want more setback on your saddle for greater comfort and power (this is especially helpful for comfort on a road fixie). However, you probably want to use narrower bars for better maneuverability. To open your diaphragm properly, you need to offset the narrower chest position by raising the rib cage slightly on your torso -- and you accomplish this with a slightly longer stem. All told, your top tube may be fairly close to your road top tube, with saddle setback and longer reach bars extending the effective distance.

All this sound vague? Well, track fitting is just different from road. It isn't a tweaking. Your road position is a good starting point, but don't expect to stay there. Track position tends to push your position a little more to extremes, plus you're always on the drops and some of the hardware (like quill track stems) have different dimensions. Sorry I can't be more definitive. Fitting someone is done quickly on the track or even on a fixie ride, but it is hard to do any way short of that.

EDIT: All this just addresses how the frame geometry fits your own personal body geometry. Next there's handling. If you're on the road, you really want to keep your trail at a reasonably high level or the bike will be quite unstable to ride. But you're not likely to find this kind of geometry on a keirin frame. Keirin geometry (with trail down from perhaps 56-58 mm to 30-36 mm) actually makes them stabler than a road geometry on banked tracks -- a road bike would want to drift away from the pole line, while these frames keep a line very nicely. To adjust for different distributions of body weight on a rider, and to adjust for different bankings and turn radiuses, one can tweak stem length a bit -- a longer stem creates more of a lever to help you force the front end through radical steering maneuvers and creates a slight bit of understeering that means you can steer to and stay on the pole line. When the track gets really steep, a short stem can simply be too twitchy and won't help you control the bike properly. Thus on really short tracks with lots of maneuvering (think European six-day tracks, the ADT track in Los Angeles, Alpenrose in Portland, Montreal, etc.) you want a very short trail combined with a somewhat longer stem. The longer stem may not necessitate a shorter top tube to even things out, because on a steep track you want to be stretched out a tad more so you aren't diving down over your handlebars -- the geometry and handling issues sometimes start looking like those on mountain bikes, oddly enough -- you want to scoot your butt back and be reaching out a bit farther forward if you're having to maneuver. What all this means is simply that once again, if you're picking your frame to ride on the track, you may need to tweak it a bit just to go from one track to another. And to ride it on the road, you may not find the trail you need, which is as important as the fit to your body. Again, apologies for being vague, but there are a lot of variables working here and keirin frames aren't typically built to road dimensions unless someone actually had it built just as a road trainer.

wow, that is a lot. helpful though. yeah i hadn't really thought about the trail but i'll keep that in mind. i am going to be riding a lot on the road with some track, possibly at the Alpenrose since you mentioned it. i'm still looking for a closer fit but i wanted to get an opinion on these two sizes.

<i>You have to remember that if you want a properly fitted track frame, you are always going to be in the drops,</i>

why would you always be in the drops?

<i>And you may want more setback on your saddle for greater comfort and power</i>

then don't buy a track bike.

That is where track riders spend their time

In track racing you are disqualified if you come out of the drops. As 11.4 said. You are going to be doing a lot of tweaking to get the bike fit right for you. Plus, plenty of people use horns on the street, and drops for the track, to adjust for comfort.

warming up, cooling down, training etc. Even if you only ride it on the track chances are you will be spending a fair amount of time on the tops of the bars.
If you get an oversize frame to make it more comfortable in the drops you might as well not have any.

Dutret,

The point is that you need the right geometry for your racing position, not for more casual positions on the bike -- one rides a track frame on a track to race it and not much else. You can be racing in a 40 km points race for about 40 minutes and never have your heart rate below 160 bpm or your speed less than 30 mph. You have to be in the drops the whole time or be disqualified. If you are bent over a shade too far, you lose lung capacity and will quickly fade. And while a kilometer time trial may be a very short event lasting barely more than a minute, if you are just slightly constricted in your breathing, you may only lose by 0.1 or 0.2 seconds but that is often the margin between 1st and 5th.

If you aren't racing, then skip all this. But if someone is buying a keirin frame with racing in mind, they need to consider this. And it's a bit crazy to demand keirin geometries but then to size the frame such that one gives up the whole point of the geometry, and the reason why it's been optimized to where it is.

that makes sense I thought you were suggesting to raise the drops far enough so as to make the position comfortable for normal riding since that is where a track bike is meant to be ridden. Anyway the difference in headtube height will be obliviated by different stems and bars. Even if that wasn't the case fitting systems are only accurate to within a couple of centimeters(if that). If he is buying a frame based purely on that I don't think going 1cm below the reccommended size is a big deal. Ideally he should try out various bikes and figure out what he likes but I guess thats not an option.

I would say go for the larger size. you're right at the toe-clip-overlap line and the larger size will allow you more clearance, especially helpful when commuting and low speed riding. it's also closer to what fits you. and I really doubt you'll ever ride a keirin frame and think to yourself, "this thing feels like a boat."