Road Cycling - Which way to compromise on frame size?

Hi all,

Say you were in the situation where you had to pick between two frames. Using one meant a really short stem, but the seat tube is the right size. Using the other meant a regular stem length, but the seat tube would be 2 CM too short.

Of course the best bet is to get one that measures right both ways, but that doesn't make for a good poll.

I own one of these combo's and have a chance to change to the other way for not much $$, so am curious what people think.

thanks,

Steve

EDIT: I wanted to remove which combination I already have so the results aren't skewed based on the "go with what ya got" ethic.

Wow,

the results are evenly split so far, I was expecting a runaway for one of them.

Anyone care to share their logic why they picked one option over the other?

thanks,

Steve

This is actually not enough information about the frame, because if the seat tube is too short there's the possibility of not being able to get the saddle far enough back behind the BB without resorting to weird seatposts.

But I wouldn't want a bike with too long a top tube, because I can foresee the possibility of wanting to move to a more upright position, either temporarily because of injury, or permanently because of a change in bike setup (flat bars, say).

So if I absolutely had to make this choice, I'd go with the the shorter seat tube assuming I could get proper fit with an appropritate seatpost. Otherwise, just forget the whole thing.

Just goes to show why the right size is the only rational choice. And why walking away from the wrong frame is still a bargain, no matter how cheap it seems.

RichC

I agree with Rich that more information about the frame would be helpful. Here's a situation I ran into when I purchased my first road bike (compact frame). Perhaps you've already taken this into account...

The LBS told me I measured in-between the medium and large size frames. They suggested that it was easier to compensate for a slightly too-small frame via stem and seatpost adjustments. I (regretably) went with the smaller frame.

Sure, I was able to get a tall seatpost and a long stem. But what I didn't take into account was this: In order to acheive a comfortable vertical distance between the tip of the saddle to the top of the bar I needed a stem with a lot of rise. The more rise a stem has, the shorter its effective length. I could either have an uncomfortably low position in the drops or compromise my reach. I finally tried out a very long quilled stem which did allow for the correct height and reach, handling was compromised and it looked, uh, very in-elegant. Eventually sold the bike.

Originally posted by Rich Clark

But I wouldn't want a bike with too long a top tube, because I can foresee the possibility of wanting to move to a more upright position, either temporarily because of injury, or permanently because of a change in bike setup (flat bars, say).


Hmm, so you would say that having a 90mm stem sounds like too long a top tube?

My reach measures out to be somewhere between 66.5 and 67 CM. My c-c seat tube shoud be 56, 58 c-t according to the formulas.

The frame I have has a 57.5 top tube. So a 90 cm stem gets me to 66.5, 100mm gets me to 67.5 which is what I have on my current bike and feels a tad too long. The top tube on the smaller one seems ideal at 56 CM. (110 stem seems like a good size, I guess maybe a 112 would be better? any ideas?)

The seat tube on the frame I have is 57 c-c (59 c-t)which is also 1 cm too big, the smaller size measures 55 c-c (57 c-t) which is 1 cm too small, but that probably isn't a biggy.

I hate bike sizing, too damn difficult for a perfectionist like me. This thread helped me make my mind up that the frame I bought is most likely too big though and should be thrown back to the sharks on e-barf or ???

thanks for all the o-pinions so far.

take care,

Jester

Ooops. I voted wrong (misread). When the results are done, take one from "right size seat tube" and move it to "seat tube 2cm short"...

Neither stem is way out: "really short" stems, IMO, are those <80mm & really long >120mm (that's forward reach, accounting for rise angle). 90-110mm has minimam difference, in my experience (I've played around with stem lengths quite a lot to tune my bikes). I've not voted because I reckon either ought to be OK.

I don't think seat tube length is particularly important: reach is the key. You can fix seat tube length with seat post & bar rise - reach can only really be "trimmed" with stem (+/- 1cm or so). The options you've posted, by this thinking, are equivalent.

Agree with other posters, though, more info on the frames would be useful.

A 9cm stem is OK. I ride a 54.5TT with an 8cm stem. Even 6cm is OK if you happen to be a very small person!!

Back to the main Q, If the length of the bike is good, then having an extra few inches of exposed seatpost, instead of seat-tube makes NO difference at all.
It does not affect the fore-aft position of the saddle. This is set by the angle of the seat-tube. and the seat-post adopts that same angle. Modern seatposts come in such a variety of laybacks that we no longer have to pick the seat-tube angle to gert a good fit.

A low top tube can affect the placement of the bars. On the + side, it will permit a lower bar position for aerodynamic riding. On the -ve side, it will have a shorter head-tube, so a more highly stressed headset. If the rider wants a higher bar position, then it will need some form of rider stem, but modern stems are very stiff, so its not a really big deal.
If the bike is very low AND the TT is too short, then you would need an excessively long stem, which affects handling, but the dilemma posed has a bike with the CORRECT TT length.
This style of bike (correct length, but low TT), is pretty much the concept behind Giant TCR and other compact bikes.

You did'nt give any info about how you were going to use the bike. IMO the smaller frame plays better at racing, while the larger frame with a short stem will obviously be understeering and more stable.......In the past , I've bought both sizes.

well, i voted for the correct seat tube..


I am assuming that this frame has the right seat tube angle for you, so the positioning of the saddle wont be so hard...

There are lots of stem sizes ranging from 40mm up to 130mm. So you can play more here (just in case)..

In racing, a longer top tube may be an advantage in racing.. Although may not be as comfortable, but since there is a wide range of stems you can choose from this can be fixed..

However, a too steep, or vise versa, seat tube angle might not be as easy to adjust with the saddle alone.. So you might end up getting one of those "unique" looking seat posts...

Anyway, its just my opinion... There are lots of things that has to be looked into...

PS:i'm a short person, 5'6", and am a fan of the classic geometry, i can relate

Well,

Sounds like I am probably between the two sizes a bit and whichever one I pick i'll be okay, which is good.

As far as the requests for more frame info, I guess i'm not sure what else I could offer?

here is the geometry of the smaller size, I can't find the geo. of the biogger size on the web (BTW the link is to an out of stock product, in case you like the price, heh.)

univega modo volare (http://www.pricepoint.com/product494.html)

take care,

Jester

Jester,

I'm not sure I get what you're asking, so let me pose
a question to you.
Does your frame feel too big? Are you too stretched out?
what isn't right for you?
Ok, 3 questions.
I keep getting hooked by stem lenght and seat tube,
the more important length should be Top Tube.
For what its worth, I'd say go to your LBS
and get a fitting done. If you're that concerned by this
its the only way you will ever feel satisfied. Take your
current ride with you.

Let us know how this turns out.
Marty