LARGE frame sizing question 60-66cm

[rodcad]

So I'm curious. Why is it you see so many "smaller" framed bikes that are square such as 57x57 or even bikes with longer top tubes than the seat tubes, BUT, when you get to the larger sizes top tubes are more often than not 59cm, give or take 1cm? It's not uncommon to see a 64x58 or 64x59 bike at all and it seems to be the norm in my mind.

So do peoples torso's tend to be close to the same length in general and for the big guys it's all in the legs?

As a for instance see the MX Leader geo chart:

[Ahneida Ride]

May be I can get Kelly to chime in here ...

My Bedford is a 65/67 ... that is with 2 degree of slope

Top tube is an effective 60 or there about

Hey ... Smiley fit me and it's spot on.

[DRZRM]

Can't answer, but I've always wondered the same thing. I'm happy enough on a 59 or 60 square, but ideally, I'd like a 58 seat tube 60 tt, and they are rare birds. I have a Zanc that does that and it fits like a glove (58 st 59.5 tt) and I liked it so much, when the guy it was built for sold a custom IF SSR, I grabbed that one up too.

[rodcad]

May be I can get Kelly to chime in here ...

My Bedford is a 65/67 ... that is with 2 degree of slope

Top tube is an effective 60 or there about

Hey ... Smiley fit me and it's spot on.

thanks I appreciate that. I just find it curious why for example the Merckx geo above is square at 56x56. Smaller sizes have longer top tubes than seat tubes, larger sizes have shorter top tubes than seat tubes.

[echelon_john]

Smaller sizes often have relatively longer top tubes to minimize toe overlap. Large frames often use relatively shorter top tubes, in part, to reduce/prevent speed wobble which will become more of a risk when you stretch a given tt of the same diameter out by 3-4cm over the 60cm point. I think most of the examples you're using are production bikes; custom obviously frees the builder to use a larger diameter, longer top tube where appropriate.

[rodcad]

Smaller sizes often have relatively longer top tubes to minimize toe overlap. Large frames often use relatively shorter top tubes, in part, to reduce/prevent speed wobble which will become more of a risk when you stretch a given tt of the same diameter out by 3-4cm over the 60cm point. I think most of the examples you're using are production bikes; custom obviously frees the builder to use a larger diameter, longer top tube where appropriate.

That makes sense. I would hope as frames get to the larger sizes then bigger or beefier tubes are used so wobble is minimized. I once had a very large Peugeot PX or something frameset and chickened out from building it up because it was made from Reynolds 531 Pro tubing as I recall, very lightweight stuff. Very beautiful frame though. Still wish I had my '86 Peugeot back that was all Mavic equippped. What an idiot I am for ever selling that one.

[Ahneida Ride]

However ..

if you take a guy like Uncle William ....

I bet he could EASILY fit on a 65 by 62

even easily on a 66 by 64. ...

I think his Zank cross is a 64 by 62 ? But then I am really guessing.

A good builder know how the bike will ride even before he builds it.

[cnighbor1]

Zinn builds bicycle frames for tall riders. There was an article this year by Zinn about sizing a frame correctly for tall riders. It went against normal practice of just increasing frame dimensions for a bigger frame. anyone remember were it was located

Here is one

http://voices.yahoo.com/an-interview-zinn-cycles-859819.html

http://www.sandsmachine.com/bp_zin.htm

http://zinncycles.com/Zinn/index.php/archives/5

[Villgaxx]

on a road racing style frame, wheelbase considerations are important on the larger sizes. too long and you don't have a proper-handling racing bike anymore. custom sizing can be a wicked huge boon for the oversized rider.

[Ahneida Ride]

That makes sense. I would hope as frames get to the larger sizes then bigger or beefier tubes are used so wobble is minimized.

Kelly substituted a beefy down-tube for my seat tube ...

Since the frame is lugged, he had to eviscerate and then custom rebuild the
lugged bottom bracket to accommodate the unusual seat tube.

Of course that also precipitated building a custom sleeve to accept a 27.2
seat-post.

But I do understand that larger frames are easier to design/draft/build
then smaller frames.

[mnoble485]

Along these same lines I have often wondered why a chain stay is about the same length on a 62cm as is on a smaller bike. I ride a 61cm by 60.5 but have often thought I would benifit from something like 62x59.

Mike

[PaulE]

My 23 year old son is 6 ft 7 in and wanted to give road bike riding a try. Since I wasn't sure how he would like it I picked up a 68 cm Miyata One-Ten from the late 70's/early 80's and built it up with an Ultegra 6500 group I had and some new Tektro long reach brakes. He likes riding and so I'm looking for an upgrade for him already.

While the seat tube is 68cm ctc, the top tube is only 58 cm ctc! With a 12 cm Nitto Technomic Deluxe it fits him fine as he likes his bars level with his seat.

The other things I found interesting about the original build of this bike were the 170 mm crank arms and the 38 cm ctc handlebars, not what you would expect on a bike this size.

[jmoore]

But I do understand that larger frames are easier to design/draft/build then smaller frames.

We are about to test out this theory in the not too distant future.

[pakora]

I always thought it was because of this:

http://sixminutes.dlugan.com/wp-content/uploads/2010/02/height-bell-curve.jpg

i.e. there just aren't that many people on bikes that size compared to the most popular sizes (say 53-58cm), while a 62x59 can still conceivably fit a big chunk at the taller end of the curve. Just like the bmi charts which tend to stop at about 6'2" or so, my guess is that the much smaller number of people and their much less proportionate dimensions are beyond the reasonable limits of the shrink/stretch-to-fit off-the-peg geometries.

It's definitely been my experience that most people my height and taller aren't built like me - they usually have much longer legs.

Sure do wish there were more 64 square frames out there though :D

[ultraman6970]

IF a large frame is built using stock columbus (for example) the frames gets too flimsy if built squared, thats why the guys that have those super large frames that are squared the frames generally comes with a top tube coming from another manufacturer or just plain straight gauge tubing that for a tall guy with more than 100kg in weight it wont be that perceptible. I believe the larger frame you can built with columbus is like a 63, anything larger means to swap tubes, with a 66 the guy is better just training to get into the MBA, he will get more money and satisfaction in there than from cycling, specially in the chicks and money depts :D

As for angles in large bikes I think just the opposite of what the tables in many of the manufacturers are doing... just opinions.

[chismog]

Loving this thread. I've got a couple disciples who are 6'4" and I'm always trying to figure out the nuances of fitting them.

A couple observations I have with this limited data set... for guys larger than my friends I'm sure all bets are off. But at this height, neither of these guys needs as much top tube as they do seat tube. In fact I've ruled out frames with TTs longer than 59 or 60 for them, even though they need 62cm frames.

As an interesting corollary, it also appears that many/most frames smaller than 54 have longer top tubes than seat tubes. Seems like one can infer that in general, while torso length increases with height, it is leg length that makes one short or tall.

Seems like you get a whippy frame with conventional tubes. Is Freuler style geometry intended to help with this by decreasing the size of the main triangle?

[rphetteplace]

I've said it many times before "fringe" sized riders (tall or short) are much more likely to be built so much different than average Joes. I was talking to a guy over the weekend who was about my height and his saddle height was 10cm higher than mine! His reach was about 5cm shorter. Us giants are all special I guess.

[JLNK]

If one goes back into Serotta brochures, say from 1998 and 1999, a 62cm CSI and Rapid Tour frame are listed with a 62cm toptube. I have a 63cm CSI and a 65cm Colorado, each bought used, and each with a 62cm toptube. I usually run a 14.5cm stem. For taller riders it is obviously how they fit on a bike that would determine the geo. For me, I want a straight line down from my hands in the drops to fall just behind the front axle, and a straight line from my butt when I am all the way back on the seat to fall just in front of the rear axle. This means a 62cm toptube, a 14.5 stem, 42.5 or 43 cm chainstays, and a front end with a 73.5 degree 43cm rake or a front end with 73 degree and 4.5 rake. This is very close to the stock geo. Serotta used to list for their Rapid Tour frame for a 62cm frame. After experiencing this geo, and liking the fit and handling, I stopped listening to people who said a 62 to 63cm frame had to have no greater than a 60cm toptube otherwise the dimensions fell outside of some formula, but just my opinion.

[Peter P.]

From what I've read, taller men aren't proportionately taller from head to toe but most of the height increase is in the legs.

But your best bet is to pose the question to Lennard Zinn as has already been suggested. He's the man! You can actually e-mail him via the VeloNews website or try here: veloqna@comcast.net

[rodcad]

If one goes back into Serotta brochures, say from 1998 and 1999, a 62cm CSI and Rapid Tour frame are listed with a 62cm toptube. I have a 63cm CSI and a 65cm Colorado, each bought used, and each with a 62cm toptube. I usually run a 14.5cm stem. For taller riders it is obviously how they fit on a bike that would determine the geo. For me, I want a straight line down from my hands in the drops to fall just behind the front axle, and a straight line from my butt when I am all the way back on the seat to fall just in front of the rear axle. This means a 62cm toptube, a 14.5 stem, 42.5 or 43 cm chainstays, and a front end with a 73.5 degree 43cm rake or a front end with 73 degree and 4.5 rake. This is very close to the stock geo. Serotta used to list for their Rapid Tour frame for a 62cm frame. After experiencing this geo, and liking the fit and handling, I stopped listening to people who said a 62 to 63cm frame had to have no greater than a 60cm toptube otherwise the dimensions fell outside of some formula, but just my opinion.

my 2 customs are 64x60 with 12cm Pearl stems which are closer to 12.5cm. Always felt fine but somehow "short", especially when climbing. New frame is 63x62 and I'm really anxious to try it.

Where do you find 14.5cm stems?

[rphetteplace]

From what I've read, taller men aren't proportionately taller from head to toe but most of the height increase is in the legs.

But your best bet is to pose the question to Lennard Zinn as has already been suggested. He's the man! You can actually e-mail him via the VeloNews website or try here: veloqna@comcast.net

I'm 6'6" with about a 34" inseam. So not always.

[stackie]

I'm 6'6" with about a 34" inseam. So not always.

Which is why you go custom with Mike DeSalvo. :). You aren't going to find a long top tube in a stock bike like he's put on your bikes.

Jon

[Llewellyn]

Judging by the bikes that I see in the classifieds I get the impression that most of the people on here are giants!!!!

There hardly ever seem to be bikes in the 50 -53 cm seat tube range, unless I'm not looking hard enough.

[chismog]

Judging by the bikes that I see in the classifieds I get the impression that most of the people on here are giants!!!!

There hardly ever seem to be bikes in the 50 -53 cm seat tube range, unless I'm not looking hard enough.

Giant bike nerds like me. But I only ride a 57. :rolleyes:

[Chance]

So do peoples torso's tend to be close to the same length in general and for the big guys it's all in the legs?


My observation over the years is that very large riders “usually” don’t ride as stretched out as their smaller counterparts (when adjusted for age and body mass). And it doesn't appear to be because they can’t find frames with longer top tubes. Most could have been riding much longer stems if being more stretched out was their goal.

In my opinion some of this difference in top tube length is also driven by other physiological differences between large and small individuals. Two come to mind.

First, very large individuals are “generally” not as strong on a weight basis as smaller people. A very large man is unlikely to do as many pushups or pull ups as a guy a foot shorter. Also explains why large riders can’t climb as fast “on average”. There are exceptions but it’s just simple physics. Hence, on average if very large riders were “fit” on bikes as aggressively as smaller riders they would not enjoy riding as much. My guess is that they would fatigue much sooner. As mentioned above by another poster large riders tend to ride in a little more upright position. Their saddle to bar drop is probably less in proportion to their total height.

And then there is wind drag. Smaller riders are affected pound-for-pound more by wind drag, so there is a tendency to get as low as possible to go faster. This in turn requires a longer reach and thus longer top tube in proportion to their height. Large guys are not affected by wind to the same degree so riding a little more upright isn’t as big an issue for them.

[echelon_john]

Another factor to consider is that folks at the taller end of the height spectrum generally see a much larger saddle-to-bar drop than shorter folks on production frames. This drop effectively increases the cockpit size, so even though the top tube may 'only' be 60cm c-c, when you factor in a 10-12cm drop, you get a longer cockpit than with the same setup with a 6cm drop.

[Brian Smith]

Why is it (snipped) when you get to the larger sizes top tubes are more often than not 59cm, give or take 1cm? It's not uncommon to see a 64x58 or 64x59 bike at all and it seems to be the norm in my mind.


Three word answer:
Historical Market Share

Two word answer:
Human Adaptability

I have two one-word answers, but I can't choose the better, so I'll stop there.

[rodcad]

Two word answer:
Human Adaptability



Tis true, us large animals can scrunch or stretch as needed.

[Chance]

Tis true, us large animals can scrunch or stretch as needed.

In theory yes. In practice only if you had no other choice.

Given a free market that could and would produce a better product for "large animals" it's unlikely that poorly fitting bikes would exist for very long. Someone out there would adjust and offer a better product with much longer top tube if that was the best solution.

[palincss]

Given a free market that could and would produce a better product for "large animals" it's unlikely that poorly fitting bikes would exist for very long. Someone out there would adjust and offer a better product with much longer top tube if that was the best solution.

But there is a free market in bicycle frames; and that market has basically decided there aren't enough "large animals" that buy bicycles, not enough demand to justify producing frames to fit them.

[rodcad]

But there is a free market in bicycle frames; and that market has basically decided there aren't enough "large animals" that buy bicycles, not enough demand to justify producing frames to fit them.

One of the many reasons to buy custom made frames.

[Chance]

But there is a free market in bicycle frames; and that market has basically decided there aren't enough "large animals" that buy bicycles, not enough demand to justify producing frames to fit them.

Yet there is enough volume to produce poorly-fitting frames?:confused:

Disagree completely. A free market would not intentionally produce and market an inferior product for long. Someone would offer a better designed product to capture a larger market share. Besides, what is enough demand anyway? Why would it be different for frames that don't fit them as for frames that do fit properly? These large riders ARE buying frames.

If the question is whether or not large frames should have longer top tubes because that would make them better, then it would cost manufacturers nearly the same to produce large frames in low volume with short top tubes as long top tubes. Don't see how low volume drives a decision to make an inferior product if a better one can be made for nearly the same price.

And for what it's worth, tube lengths isn't the limiting factor as suggested previously by a different poster. Tubes can be made in any length.

[echelon_john]

They CAN be, but again, it's a demand curve situation. If we're talking about steel, very few (if any?) tubing manufacturers make a top tube spec'd over 600mm. So once you miter it, you've got a 60cm c-c top tube, maybe a hair over.

So lots of folks, myself included, substitute other tubes (usually downtubes; sometimes a seat tube) when a longer TT is called for. This usually works well, since, if you're doing a 63cm top tube (for example) you'll want a bit more wall thickness/longer butts, as well, which a downtube can provide.

Again, no problem for custom, but not cost-effective for production.


And for what it's worth, tube lengths isn't the limiting factor as suggested previously by a different poster. Tubes can be made in any length.