How can I tell if the size of a bike is right for me?

Question

Today I disassembled my current fixed-gear, and reassembled all the parts in another frame, which I am considering to purchase.

The current owner of the frame warned me that it might be too big for me, and I agree with him. Even though, I think it has good cost-benefit, so I decided to do a test-ride.

I noticed the final geometry and rideability was pretty good, and since the frame has a long headtube (which I desire) I guess the inseam problem might not be so important considering the main goal is randonneuring, where "riding" characteristics are much more important than "mounting and dismounting" characteristics. Most probably the bike will receive a drop handlebar, even though I like flat bars a lot.

Below is a photo of the current set. There are 6cm of seatpost visible, and I might want to lower an aditional 1cm. The main reason I want to somewhat stubbornly keep the frame is that I liked riding it, didn't see any major problem except for a slight touch of the upper seatstays between the thighs, but that tends to disappear since I felt the need to put the saddle a bit more forewards.

What I am asking is:

Even considering the frameset is ridiculously larger than I would typically choose, if I like riding the bike, is there any problem that I'm not considering, a reason NOT to keep the frameset?

I'm 1,88cm (6'3") tall, and have used 56cm bikes, this one is 64cm (seat tube, bbc to top).

Thanks for any insight!

Answer 1

Frame fit

Primarily, a bike fits if you can position pedals, saddle and handlebars relative to each other so that they match your body's proportions. Secondarily, when these contact have been set, other frame parameters should fall into place so that the riding characteristics are as desired. That includes e.g. toe clip overlap, stand over height, bottom bracket height, heel/panniers clearance, steering geometry, or that an extremely short or long stem gives a weird steering balance. Depending on what you use the bike for, the importance of these parameters varies.

Does "frame size" equal "seat tube length"?

If you consider frame fit as putting the contact points in the right spots, the length and angle of the seat tube is one of the less important dimensions. By choosing the right seat post length and setback, it is possible to put the saddle in the right position relative to the pedals (or, simplified, the bottom bracket). Generally, on most frames, most riders can put the saddle in the right position relative to the bottom bracket.

Depending on the use of the bike stand over height (or clearance) is more (MTB) or less (road) important. If you want a certain stand over clearance, of course this limits the frame size to a certain amount. This is easy to determine: With the correct tires and wheels, the height of the top tube should be lower than the length of your inseam.

How to determine "frame size" instead

The critical point is often if you can put your handlebars of choice in the right spot, too. One thing to consider here is that drop handlebars have a significantly longer reach than straight ones. This is because the normal hand position is on or behind the brake lever hoods with a drop bar, and not on the straight section next to the stem eye. If one does not want to resort to extremely short or long stems, a frame usually only allows for a good fit with either drop or straight bars.

Working backwards from the hand position through handlebars and a normal sized stem (ca. 8-12cm on a classic frame like this), one ends up at a certain position where the top of the head tube should be.

Stack and reach

The corresponding frame dimensions are the vertical and horizontal distances of the head tube upper end from the bottom bracket, called stack and reach. Unfortunately especially frame reach is quite difficult to measure on a frame without complicated measurement setups (or a good picture exactly from the side without perspective distortions). Therefore many tend to use top tube length as an alternative to reach, and ("virtual") seat tube length instead of stack. One should be careful though: The position of the top of the head tube not only depends on seat tube and top tube lengths, but also on the seat tube angle (which can be even harder to measure than reach).

The easiest way to find out your needs regarding stack and reach is to measure a bike which fits you well and has the relevant handlebars setup. One way to do this is to take a photo exactly from the side and from quite far away, and measure in the picture.

What does this mean for you?

As you say, stand over clearance does not bother you with this frame, so the seat tube length is very likely ok. On the picture there is also plenty of room to move the saddle forwards, in the worst case with a zero setback seat post. So the saddle probably position fits you. Good.

I am more concerned about whether the frame reach is too long, when changing to a drop bar. But as far as I know, the classic Raleigh road geometries do not have overly long reach, and the stem shown on your picture is way longer than what I would consider aesthetically pleasing on a frame like this (especially with quite little seat post to be seen).

Without knowing more about the frame and your fit preferences it is very hard to advise if it will fit you in this regard. The fact that the frame was built with a classic quill stem in mind, but has a threadless fork today, does not make it easier: It may be that you can't rise the bars enough with an ahead stem (and the fork already being cut).

The easiest thing would be to just try putting a drop bar on the frame (ideally with an adjustable stem temporarily). With a fixed gear that should be easy to do. Ride and adjust, and you will feel if it fits.

What else?

Apart from all that I think that the average 56cm frame is quite a bit too small for the average 1.88m male (horizontal top tube, or "virtual seat tube length" assumed). I am 1.83m myself and usually start looking around what is labelled as 58cm.

I'm pretty sure that the fork is not original. Ask the seller if the original still exists. It probably is a threaded fork, which allows for higher building quill stems. And it probably looks nicer, too.

Finally: I have never heard about problems with the thighs rubbing on the seat stays before...

Answer 2

Since Bhell posted an excelent answer that deserves feedback, I am posting this "answer" of mine with some observations. I think it could help people with the same doubts, in the future.

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First of all, I enjoyed the pragmatic approach to bike fitting, instead of a somewhat questionable numerology I've been seeing around lately. Also, the rationale starts from the problem up, and not from a canned solution down. Now let's go piece by piece, considering this one frameset:

Primarily, a bike fits if you can position pedals, saddle and handlebars relative to each other so that they match your body's proportions. (...) That includes e.g. toe clip overlap, stand over height, bottom bracket height, heel/panniers clearance, steering geometry, or that an extremely short or long stem gives a weird steering balance.

You got it right from the start: when I went over the bike to ride, and after some minor adjustments (none of them at the extreme of adjustment range), I felt the bike almost exactely like the previous one, except for a slightly long reach, which I still don't know is due to too much saddle setback or too long stem. Nothing to be too much concerned, since I rode at most 2km and the immediate feeling was very soothing and familiar compared to the previous 56cm bike.

About other characteristics you mentioned, there is no overlap (plenty of clearance, actually, which is good for randonneuring with fenders), BB height was fine (quite nice fixed-gear cornering), pannier clearance is yet better (44cm chainstays instead of the vanilla 42cm of my other utility bikes, good for fenders in the rear, too), and the steering balance is stable without being too slow or hard to quick-dodge.

The critical point is often if you can put your handlebars of choice in the right spot, too. (...) normal hand position is on or behind the brake lever hoods with a drop bar, and not on the straight section next to the stem eye [like a flat bar]. If one does not want to resort to extremely short or long stems, a frame usually only allows for a good fit with either drop or straight bars.

I've been thinking about this, too. The stem on the photo is 135mm horizontally (center to center), and although it has helped me along the years with smaller bikes, specially when mounted pointing up, I think this bike should have a smaller stem if I put a flat bar, and a yet smaller one if I put drops. Since the current stem is long and I feel the bike only slightly longer than needed, I think there is room for adjustment without resorting to extreme stem dimensions.

(...) the classic Raleigh road geometries do not have overly long reach, and the stem shown on your picture is way longer than what I would consider aesthetically pleasing on a frame like this (especially with quite little seat post to be seen).

I haven't looked at it from this angle, but this sounds compelling. I have to admit that I plan to inflict some "oldschool-performance" upon my fellow riders, since the tend to look down at "old big steel stuff" from their aeroplastics bikes. For a better effect, the classic non-slope lugged kit can be complete with corresponding short stem and short post...

I'm pretty sure that the fork is not original. Ask the seller if the original still exists. It probably is a threaded fork, which allows for higher building quill stems. And it probably looks nicer, too. (...) The fact that the frame was built with a classic quill stem in mind, but has a threadless fork today, does not make it easier: It may be that you can't rise the bars enough with an ahead stem (and the fork already being cut).

Gotcha! The fork is the original threaded one, and the ahead stem is mounted to a threadless-to-quill adapter. The end result is very firm and has quite acceptable looks. By the way, the fork is PERFECT because it is curved, sturdy, has fender eyelets and gives the frameset a very nice handling (not to mention the fact that frame and fork were designed for one another by a reputable manufacturer).

I think that the average 56cm frame is quite a bit too small for the average 1.88m male (horizontal top tube, or "virtual seat tube length" assumed).

I can live with my other 56cm frame becaused I mounted it fixed-gear for training, so a more sportive position is fine if I go with good speed and not too long. For touring, randonneuring or even commuting with more gear in the winter, I have had serious problems with sore hands and feeling too cramped over the bike "in the long run", so that's why I looked for a larger frame, although I didn't have something THAT large in mind.

In the end, I decided to keep the frame, and here goes the summary of the story, which includes the insights provided in Bhell's answer:

Why I wanted a new frame:

• To have a more relaxed geometry than I currently have with bikes that are relatively small for me;
• To have a bike faster than a city bike but not so stripped down as a fixie, allowing to achieve relatively high cruise speeds for long times and some comfort.

What interests me in this frame:

• It has good design (a classic road frame from a reputable manufacturer), good construction (4130 lugged chromoly tubing, fender brazeons) and good value (relatively low price due to usage signs which don't interfere with function).
• It's high head tube brings the upper headset cup much closer to what I have been trying to get lately (I've been replacing my other bikes' stems and handlebars because with age coming I starter to feel they were too low).

What was potentially problematic with this frame (and prompted me to write the question):

• "Ride feel" could be cumbersome because some unexpected effect of larger geometry and size;
• Its reach might be too long (although I already wanted longer reach);
• Its inseam might be too high;
• The correct seat height might expose too little seatpost, thus making it hard to put some taller saddles like sprung Brooks and the like (not really a plan, but one never knows).

Why I KEPT the frame after all:

• The Bottom-Bracked contact point (the only fixed-position one) has a good height from the ground, not so low as to hit the pedals neither so high as to make it hard to put the foot on the ground;
• The Seat contact point position could be naturally found with a good range of adjustment in every direction (both horizontally and vertically);
• The Handlebar position got almost right (perhaps a bit too long) with a flat handlebar and a relatively long stem, which makes me think I could either shorten the stem a bit and keep the flat bar or shorten the stem even more and put a drop;
• If I decide to put a drop, I'll get a good upright position in the flats, a nice cruising position in the hoods, and a usable (not too low) position in the drops. Although the bike begs for this, I am particularly fond of flat bars because I have always ridden mountain bikes, and the brake levers being always at hand is a thing I value very much, specially while riding in a fast tight pack.
• The interference problems (top tube against crotch, inner thighs rubbing the upper seatstays a bit) didn't bother me after I quickly got used to them. Actually, it is cozy to have a bike so much "closer" to me (I'm not trying to be vulgar here, you know...).

As a bottom line, it was fundamental to have the points of view of everyone who answered or commented. I suspected that here in StackExchange people would be more traditional and classically oriented, and the vast majority supported the idea that big is not a problem if you don't make it into a problem. That also, reinforced a perception I have, that all this hype about smaller-frame-size-possible due to weight or responsiveness or center of gravity or whatever is way too much exagerated.

Thanks for the help, and if I have some useful additional feedback I'll post it.

Answer 3

Some say that if you can't have less than a "fist-full" of seatpost visible (>10 cm), the bike is probably too small. This is probably not a bad rule of thumb to start with.

If you would post pictures of you sitting on the bike, with the drive-side pedal at 12 o'clock, 3 o'clock, and 6 o'clock, that would be the best. It will be clear, then, if this is too big for you. Alternatively you can get a verdict from this fit computer. Even if you've never tried it, and you're a seasoned rider, the output is worth seeing. They give you three different fits: a competitive fit, an "Eddy" fit, and a "French" fit. In my experience, it's a great guide.

However I have seen folks who ride bikes that are "too big" for them, and it can be done. Personally, I ride a bike which some would say is too big, but it works for me, and to-date I have about 1400 miles on that bike. When I am on the saddle, my toes just touch the ground. It all depends on how your geometry meshes with the bike.

Answer 4

I am no expert too, having doing personal bike fits after reading hundreds of website make me more confused than better.

Anyway, after two years of adjustment I do finally come close to a best personal fit at this moment. Bike's fit that works now may change as we age, a year is long enough for that change. Blessed are those who believe on so call bike fits formulae or calculation. Here my two cents worth of ideas and experiences. For a start, you can take some reference from competitive.com fit calculation but please do not trust it 100% as I personally wrote to them after having pains where the guy in the company says the calculation do goes hair wire with certain data input. Seat height: you can use inseam formulae , seat height = inseam x 0.883 but that is 2cm too low for me. I used my shoes' heel to have the most extension when my crank arm is inline with seat tube. Again you need to try that out till you feel like you have no resistance in throwing your foot on every smooth paddling circle, that the point of sweet spot of correct seat height.

Seat forward/ backward: you may use kops concept but it not a fix rule. Again you have to get a relative point where every stroke of cycling is smooth and effortless, relatively. If you like fast cadence, push the seat more forward vice versa.

Total reach; again lots of crabs on the calculation too. My method is, adjust your seat forward/ backward till you feels at home both on the hood and drops. If you can ride on the drops for half an hour without going for the top bar, most properly you got the correct reach.

Handlebar height ; same as above and good luck.

This website is the only place where I hear someone posting correctly that the handlebar reach is measured from saddle centre to the hood tip and not the stem/ handlebar centre as handlebar comes with different shape and reach too. That is 100% correct where most so called bike fitter miss the point.

Once you got your total reach than adjust your seat to your original position and buy a new stem.

Summary: 1. Seat height. 2. Seat forward/ backward position. 3. Marked the seat position at the saddle rail and the seat post height. 4. Reposition the seat forward/ backward position to get your comfortable total reach. 5. Record your total reach fig. 6. Do the same for your handlebar height adjustment. 7. Now, set your seat height & forward/ backward position to your marked points. 8. Measure the total reach now and the seat top vs handlebar top, record the two readings. 9. Compare to your first readings, you will now know what stem length to buy and how many stem spacer to use. 10. Don't do any bike fit when you are tired or weak from days of cycling, a tired body is not flexible and will leads to very confusing bike fits.