Isn't frame size a little bit related to the purpose intended for the bike - Comfort/long distance vs race/crit? Thanks for any advice?

Jim

Yes this is true; the frame I recommend on my sizing chart is for a racing position. If your riding style is more leisurely then you can go with a frame a centimeter bigger so there is less handlebar seat height difference. A tall person over six feet could go as much as two centimeters bigger.

I also want to remind you that I measured my frames center of bottom bracket to the top of the seat lug. This was standard for English framebuilders. Italian frames and most others are measured center to center. It becomes important when sizing or buying a frame or bike; if the bike dealer is talking center to center and the customer is thinking center to top; there is two centimeters difference. Watch for this if you are buying a bike on eBay; make sure that buyer and seller are on the same page on this one.

Also some people are confused over inseam; this is not your pant size. To be more accurate it is your inside leg measurement from crotch to floor without shoes. You can’t do this accurately yourself also when getting measured pull your pants up tight into your crotch and measure from the part that rests on the saddle. (In non medical terms, the little island between your equipment and the back door.)

Dave,
First off, it's a treat to have someone of your expertise on this board. I remember seeing one of your bikes in Bicycling Magazine. Small wheels, huge chainrings; at least I think that was your bike...

I like you theory. However, you adjust seat tube height for shoe size. If I understand proper pedaling technique, i.e., ankling, all feet should be level to toes up position at the bottom of the stroke which would obviate the need for a taller ST for longer feet. What am I missing?

regards,

It bites a big one. the formula says 60 c-t, and I ride 58, or 57 c-c preferably with a 56.6 to 57 TT.

More proof you can't get closer that close with a formula. Your height and maybe a bit more inseam on a 57 c-c. I've been on 59 and 60 and even they don't fly.

Thanks for the kind words at the start of your post, and for the record the small wheel Moulton bikes are built by Alex Moulton in England and we are not related.

I thought “Ankling” went out in the fifties. The problem is people write books on cycling and they know nothing they just keep repeating what has been written in other books. There is even a drawing I still see from time to time in cycling books which shows the ankling technique. The drawing shows a cyclists leg and foot clad in dress shoes and bicycle clips on the trousers and no toe clips of course; this drawing must have originated in the 1930s

Sorry about the confusion. Then was Fuso your brand name? I'm guessing here, I remember your name from somewhere...


Then are you advocating a toes pointed pedaling style? This conflicts with everything I have ever read, both old and modern. In fact, the only person I can think of that ever used that style successfully was that French guy whose name slips me at the moment (prolly couldn't spell it anyway)

Yes, Fuso was the production frame I made.

And for the second part of your question I am not an expert coach so I feel I should ask for someone else’s input on this one.

I'm 5'11" so going by your chart I'd need either a 56 (if dividing by 3.2) or a 58(dividing by 3.1). As always, I'd fall between a "medium" or "large". :(


I wear size 10.5 and inseam is 31"-32"

Interesting. Are you measureing c-t or c-c? Do you prefer a steep head tube and relaxed seat tube? Long stem?

Well, I am 5'11.5 inches

My pants inseam is 29" Don't know my "bicycle" inseam, but it is short.

So, most of me is trunk and head.

My shoe size is 9.5 to 10 depending on shoe. I wear about a 33" shirt sleeve length.

I ride a 55 cm Lemond BA (1999) - with about 0-1/2" standover height. Fits me great, and I was fitted by an experienced fitter. Tough job fitting me!

Does this fit with your formula and theories?

Half an inch under six foot with about a 30" inseam? Yes I would say that was a very difficult fit and looks like whoever did it for you did a great job. And no, this new theory I have posted here would not work for you.

Fitting someone like you, if the person doing the fitting went by your inseam alone it would indicate about a 51cm. frame. Now common sense should tell anyone that you can't put a person almost six feet tall on a frame that small. Your height would indicate about a 57 of 58cm. so yes I would say the size you arived at is a very good compromise, and the fact that you are happy with it proves it works.

Yes, that is what I get by using the "standard" formulas, and it obviously would never work for me! One reason I am never too anxious to refer folks to those "crank in the numbers" fitting pages on the web!

We decided that the least important measurement on a roadie was standover height, and it has never bothered me a bit. Also why we chose the Lemond with a bit longer TT.

Thanks so much for your feedback.

Maybe someday I will get a custom fit.

Interesting annecdotal stats Dave. I think they're interesting in terms of getting newbies on roughly the right size frame, but appart from that I think we have to be a bit careful here for a couple of reasons.

Firstly, I think 'frame size' is slowly becoming an irrelevent measurement. It was quite relevant when lugs were the only option, but now with bikes having sloping top tubes more often than not, we're getting into this realm of 'theoretical size' where things become even worse than the 'good old days' when all you had to contend with was 'Do you measure ctr-to-ctr or ctr-to-top'! It's got to the point where I prefer to know what the head tube length is/should be, because this is a great number when it comes to setting handlebar height - which is one of the 3 key contact points that we're ultimately interested in.

Secondly, I find top tube length pretty important. Even though I've probably only had a tenth of the road bike experience you have, I do realise that the relationship between the seat and the bars are critical, and this is largely based on top tube. However this observation comes with a couple of caveats -

1) The 'reach' figures ( top tube + stem length ) are variable because you can design 2 bikes that have identical reach figures, yet the numbers are all over the shop. For example, when designing my personal bike, I had the option of a 605mm top tube and a 120mm stem, or a 615 top tube and a 110 stem. Both would net the same result, but I had to allow for CG-Wheelbase as well, and knew that the shorter top tube and slightly longer stem would mate well with my chosen rake/trail/HA figures.

2) Flexibility is also a key component to top tube or 'reach' figures, and this cannot be established through averages. For example, I went with a shorter top tube, and a slacker HA/longer rake fork with a 120mm stem on my personal bike, knowing that my flexibility would increase as I got fitter. This would allow me to go with a longer stem or bars as I got fitter and increased my core stability, without adversely affecting handling.

I guess the bottom line here is this all illustrates the value of true custom bikes! Many consumers only delve into geometry as far as asking questions like "What's the head/seat angles? What's the frame size/top tube length?" without realising that it's a bit more complicated than that. This is exacerbated of course by many bike companies now only offering 5 'compact' ( I despise that term ) sizes, and not even bothering most times to inform consumers what fork rake they have spec'd.

Kudos on sharing your stats, Dave.

Lugs have never been the only option. Denver would have been an excellent candidate for a fillet brazed frame with a long, sloping top tube to better accomodate his short inseam and long upper body. Actually, he is one of the arguments for a compact frame design. In addition, lugs can be fabricated to custom angles if desired.



Wasn't the first road bike your fabricator ever built for you the one you had built for yourself this year? Congrats! :)

Yes Don, Thylacine Cycles is a new company. Find a way to deal with it, okay? :rolleyes:

Anyway, anything constructive to add to the discussion, or....?

Also watch out how the size is measured. A Cannondale is measured c-t, but from center BB till top of head tube (not till absolut top!) so a 60 cm. becomes a 63 cm than. De Rosa is another example, they measure c-t on top of the BB (where the seat tube begins) untill top.

Well, I'm long-leg/short-torso and this formula comes out just a bit smaller than I like to ride. I am 174cm tall with an inseam of 85cm. The formula "says" I should be on a 54 or 55 but I ride a bike that is 56.5 c-t (55 c-c). If I went smaller, I'd have to use even more spacers to get the handlebars high enough and I'd probably also run into issues with hitting my knees on the back of the handlebars when standing.

I don't believe there wer many of those around in 1998-99?? At least I didn't see them. Interesting thought, though.

Fillet brazing has been around forever. It's just brazing without lugs. It allows the builder to use what might be non-standard angles and geometry that standard lug configurations might prohibit. A sloping top tube used to be considered non-standard at one time. :)

Welding could be and is used to accomplish the same thing as fillet brazing. However, it used to be somewhat stigmatized because of it's association with cheap, heavier bikes, so was rarely seen on high quality bikes. But even standard cro moly tubing can be welded.

The use of sloping top tubes to accomodate a shorter inseam has also been around forever, but usually it is used to get standover height for very short people, mostly women.

The sloping top tube/compact frame with longer top tube combination is really ideally suited to someone like you.

An example of a fillet brazed frame:

http://www.classicrendezvous.com/Bri...r_Martinez.htm

It might also depend on what you were looking for. Investment cast lugs and fillet brazing are very labor intensive and, I think, considered the highest form of a framebuilder's art. So you don't generally see this on any true production bicycles.

Fillet brazing is a skill that requires a lot of practice; it is a balancing act with liquid molten brass. Done right surface tension will allow the brass to hang in the corner of the joint while at the same time all flowing together. The end result is a joint that requires only a minimum of clean up after.

Get the joint just a little too hot and the brass will just keep running inside the tube; or it will drip off onto the floor; or worse still land on your feet and burn holes through your sneakers and your foot. Get the joint not hot enough and the brass just lays there like heaps of dog poop, and after hours of filing you are left with a joint that is full of pin-holes and craters. And the only thing you can do is start all over again.

A response to Thylacine Post # 40

Thank you for an interesting and enlightening post. It seems to me that everything has changed and yet nothing has changed. You still have two wheels spaced roughly the same distance apart; what has changed now is that a frame builder/designer has more scope as where they can place the rider. Where you place the rider affects the rider’s comfort, the efficiency of the rider getting power to the pedals, and the way the bike handles. This is no different than it’s ever been. I can see opportunities for framebuilders who know what they are doing, and I can see the potential for a lot of mistakes by engineer designers who know little about bikes.

And what does anyone use as a point of reference anymore? It’s easy for the framebuilder who can see the whole picture, but what about the average rider and even the bike store owner fitting that rider, it must be as confusing as hell. There has always been more to frame design than seat tube, top tube, and “What angles is it?” But when a rider bought a new frame if the size and angles were about the same, s/he knew what they were getting. Now as you point out two frames that appear to be the same can be totally different.

I agree, it must be very confusing for the newbie or the shop owner who is trying to juggle the customers needs as well as his/her own needs to move stock, economic reality and all that.

Personally, I've had a road bike in my stable every year for the past 15 years, and although I'm really a mountain biker pretending to be a roadie, I can see some big holes in the current road design/geometry paradigm. There's a shift starting to happen now though, and you can see it with the new Specialized Roubaix models - longer stays, more rake, higher bar position - many of which I've experimented with on this big orange bike of mine.

For someone like me, many of these changes are changes that the MTB scene went through in the past 5 years or so. For people of your experience though Dave, it's probably deja vu - this 'new' emerging geometry is not much different to the classic bikes ( I'm guessing ) of the 70's or something.

Do you know where this obsession with short, low and steep came from? Was it just people's obsession with 'percieved' 'quickness'?

I never followed fashion and that policy worked for me over the years; if I designed bikes today I would do the same. Fashion should only dictate the overall look; a sloping top tube is an example; choice of different tube diameters would be another. When you start changing geometry for the sake of fashion; what are you achieving apart from a temporary marketing ploy? And you are not doing anything that hasn't been done before.

So to answer your question about short, low, and steep. (We are talking road bikes?)

Short: Shorter is stiffer, but should never be taken to extremes. Lengthening the chainstays is only making the drive section less stiff. You may add marginally to the comfort, which for recreational riders would be a plus.

Low: By this I take it you mean low handlebars in relation to the seat height. An efficient riding position is one where the arms are in direct opposition to the legs. When making a maximum effort legs are thrusting downwards with more power than your body weight. The only thing holding you down is your arms; power is transmitted from the arms through the shoulder and back muscles to the legs. When you need extra power you get out of the saddle; this is a natural reaction, even a child will do it even though no one has taught them to do it. You are doing this to not only get your body weight over the pedals but also to get your body closer to your arms so you can get a direct pull on the bars. Like lifting a heavy weight you need your arms close to your body, and if you hold the weight at arms length it will put a strain on your back. So too if your arms are stretched out too far ahead; the result will be back ache on a long ride. Arms need to be low and as near to the body as is practical; taking into consideration comfort and the rider’s ability to handle the bike.

Steep: I never believed in steep head angles; steeper seat angles in the case of smaller frames to achieve a riders position as outlined above. It has been established for many years that the ideal head angle for a road bike is 73 degrees. You can go to 74 degrees for criterium bike (with a shorter fork rake) and 72 degrees for a touring bike or an extremely small frame where you need to make the front end longer. But if you go steeper than this you make a bike that is squirrelly and twitchy in it’s handling; especially when you get out if the saddle to sprint. Any shallower on the head angle and the bike will feel sluggish or like a wheelbarrow when you sprint.

My advice to any framebuilder, or even a large manufacturer; find out what works and stick with it. If it goes against fashion then only give your customers as much information as they need; I wouldn’t advertise the fact that I was against fashion. Customers will flock to you when the word gets around that your bike handles and rides better that anything else.