Road Cycling - Sizing components

Sizing questions....

With this bottom bracket, the website tells you to use 118.5mm, but there is a 68x118.5mm and a 70x118.5mm. How is that first number measured? Which one do I use?

With this crankset, which size would I use... 170/172.5/175mm? I'm 5'8". Is that the length from the screw to screw?

With this rear cassette, it has alot of different sizes... I don't know which one to choose??? I'm putting it on this wheelset.

With this handlebar, I might have to go to my LBS and try one out... how are they measured??

-Dan the Man-

Okie the Bottom bracket length is that number 118.5, his is determined by what crankset you have. Now the first number 68 or 73 (english or italian) is determined by the frame. Some are italian(73) some are english(68) which is the actualy width of the bottom bracket on the frame.

Crankset I feel is largely a personal thing, I am 5'7" and use 175 on my road and mtb bikes, but alot of people my height go for shorter cranks. The 170-175mm is the actual length of the crank arms.


Now the cassette i can't tell you which one to get, since I don't know what kind of gearing you want.

Handlebars can be measured Center to Center or they can be measured by the outside, so it varies manufacture to manufacturer. The width you need is based on your shoulder width, but personal preference plays a roll here to.

Crankset length is of course very personal but I good rule of thumb is that if you're a male under 5'6" (assuming relatively proportional inseam) you probably want to go with 170mm. I prefer as short a crank as I can get away with on a roadbike since shorter cranks help promote faster spinning. Of course the downside is that you can't get as much leverage and torque up hills like you can with a longer crank. This can be taken care of with proper gearing however.

As for gearing the rear cassette, as Kev implies, it all depends on your fitness level, what crankset you're running, the terrain in your area and your style of cycling. I live in a fairly hilly area so I need some pretty low gears. I also run a double (39/53) instead of a triple so my largest rear cog is larger than if I had a granny gear up front. I'm running a 12-27 in the rear. The guys in the TdF on the mountain stages were running up to a 25T as their largest cog and most of them were running doubles. They're however much more fit than I. Were I to run a triple with a 30 up front, I think I could get away with a 23T as my largest cog. As for the other end of the spectrum, I find that if I'm outspinning a 12, then I'm going pretty fast (usually downhill) anyways and because I'm not racing, I'm just better off getting aero by tucking in, coasting and concentrating on a smooth descent instead of wasting my energy trying thrash by keeping up the cadence. I wouldn't mind an 11T but I haven't found a cassette with the range I need that starts with an 11T. I'd rather trade top-speed for lower-gearing. If however you're riding area is really flat, you want that speed and you can manage the cadence, you might consider a cassette with an 11T.

OK, for this bottom bracket...
http://www.nashbar.com/nashbar_photos/medium/SH-BB6500.gif
I'll have to measure the width of the bottom bracket when I get the frame.

For the crankset, I'll go with a 172.5mm for this crankset...
http://www.nashbar.com/nashbar_photos/medium/SH-FC6503.gif
it's the middle size. and what's another 2.5mm, that's really tiny.

For the this rear cassette...
http://www.nashbar.com/nashbar_photos/medium/SH-CS6500.gif
There's no doubt I want a high top speed. I have really strong legs. I started out with a mountain bike, so I don't think the hills would phase me. It comes in all of these sizes: 11x21, 11x23, 12x23, 12x25, or 12x27.

For this handlebar...
http://www.nashbar.com/nashbar_photos/medium/TR-PRBAR.gif
I'll just have to try one out. They come in these sizes: "Width measurement is taken center to center. Specify Width: 40, 42, 44 or 46cm."

-Dan the Man-

Ultegra components are a good choice. As far as 2.5mm not making that big a difference, you might be suprised. However, 172.5mm is probably the right length for you anyways especially if you're more used to MTB crank lengths. I run 175mm on my MTB and when switching back and forth it sometimes take me a few minutes to get used to the "new" length initially... especially if I haven't ridden one or the other for a while.

yeah, I really like the Ultegra 6500 series. They are really good parts for a decent amount of money.

Check this out! (http://www1.coe.neu.edu/~dschilli/bike.html) I made a cool little listing of all the parts for my 2001 Specialized Allez Sport here.

I have still yet to find out how much the frame weighs?? it's a 52cm frame. I tried to email Specialized, but I don't think they'll tell me. You wouldn't happen to know the weigh of a 2001 Specialized Allez Sport Frame is??

-Dan the Man-

Originally posted by ockey53
I have still yet to find out how much the frame weighs?? it's a 52cm frame. I tried to email Specialized, but I don't think they'll tell me. You wouldn't happen to know the weigh of a 2001 Specialized Allez Sport Frame is??

Have you tried weighing it yourself? Do you have a bathroom scale?

[1] Step on the scale and weigh yourself.

[2] Grab the bike and weigh yourself with the bike.

[3] Subtract the weight from step-1 from step-2 and there's your bike's weight.

Of course, if you just want frame weight, you'll have to remove everything from it first such as seatpost, fork and stem.

Originally posted by khuon
Have you tried weighing it yourself? Do you have a bathroom scale?

[1] Step on the scale and weigh yourself.

[2] Grab the bike and weigh yourself with the bike.

[3] Subtract the weight from step-1 from step-2 and there's your bike's weight.

Of course, if you just want frame weight, you'll have to remove everything from it first such as seatpost, fork and stem.

That would work, but I don't have the frame yet. And I would be wondering what the weight would be with the headset, fork, seat and seatpost. But that is a good idea.

-Dan the Man-

Oh, I forgot to add that you'll probably want to remove the headset too if you want just the frame weight. That's not normally a palatable proposition just to get frame weight but since you've said you're concerned with the weight with stuff on it then that's not an issue. I would suggest holding off on weighing it until the bike is fully built. Partially built bike weights don't typically mean that much unless you're component-shopping for a partially built bike based on weight... then again I guess that might be what you're trying to do?

No.... I just wanted to know the total weight of my bike, just as a reference, nothing more than that. Of course, I'd like to get my bike as light as possible.... but I a MTB too, so I'm used to relatively heavy. Just wanted to know so I can take a mental note.

-Dan the Man-

Most sources recomend a 170mm cranks for average male rider (5'8" like me).
You do get smaller ones. 165 is considered small, and is used by smaller riders, and track riders who need more pedal clearance.
The range of cranks from a proper manufacturer (like Specialities-TA) range from 150mm to 190mm.

A"normal" size bar would be 42cm wide. It should be about as wide as your shoulder joints. They do come in different shapes,a nd with different radius drops. Personally I like a small radius, but others prefer a larger radius, which gives a deeper drop.
Check out 3TTT.com for a selection of styles and sizes. Bars also come in different tube diameters, which need different types of stem. Stems are also available in sizes from 6-14cm. Normal size male would generally have a 10cm but you can go +- 2cm for a good fit.