# Modern bicycle construction



## saus (Oct 22, 2006)

In response to a friend's request to join in the Tour de Cure, I actually bought a brand new bike, tight shorts, funny shoes, and clothes with colors even a golfer would be embarrassed to wear. Then of course I have had my ins and outs with "clipless" pedals etc etc and have been learning that there's a lot to learn about modern biking.

Almost all (if not all) of you bikers have more experience and knowledge of biking than I - and so I appeal to you for your insights, hoping this will be a lively, ongoing and informative thread.

What are the different characteristics of materials used for frame construction? If one has a metal bike, why would one want a carbon fork - or "bottom bracket" (what's that?). If you could chose to have a bike custom built in any configuration you chose, what materials would you specify and why?

That's enough to get started. I'll ask about components and geometry in other threads later. 

This thread is intended to address only road bikes.


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## cbcbd (Oct 23, 2006)

The bottom bracket is what your pedal crank spins on.
http://www.bikewebsite.com/bikeopedia.htm


Frame building is a complex science, but in the simplest form it's a balance of weight and rigidity (needed for better handling).  
Carbon fiber is used in for weight savings (like in performance cars) and for shock absorption.  The more parts you can replace with lighter materials the lighter your bike will be, the less energy you'll use, the faster and longer you'll go.  
Usually the forks, chain and seat stays (and other odd and ends like seat post, handlebars, bottle cage) are replaced with carbon fiber to give a smoother ride - carbon fiber has more give and will absorb some of the bumps (very little, but it makes a difference).  But because carbon fiber has a lot of give it's usually not used for the entire frame or the bike will feel too mushy and not as responsive.
But, there are different constructions of carbon fiber that address that problem (the resin in CF is the weak link, so by making CF with smaller strands of fiber will give you less space that is filled by resin - so you have stronger CF), so one could go on forever about where else you could put carbon fiber on a bike. 

I'll stop here since I could go on forever and I don't even make frames - meaning, there is a lot to consider and to know if you are to tinker with the specifics of frame building - that is why most who want to build their own bike choose a frame and then build the bike around that frame.


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## andyzee (Oct 23, 2006)

Potential for a good informativ thread, may be better at the beggining of bike season though  But here's my input on frame materials.

_Disclaimer: I'm no expert; these are just some things I learned through experience. Also, the following are general guidelines. Innovative construction techniques and the combination of materials will make a difference. That said here you go._

With regards to bike materials:

Chrome Molly: 

Pros - Inexpensive, good at absorbing shock.
Cons - Not very stiff, this results in loss of power in pedaling

Comments - Chrome Molly is a good inexpensive material, but is not very stiff. A chrome molly frame can bend as much as 1/2" with each pedal stroke. As an exaggeration, imagine riding a bike made from rubber, what happens to power transfer when the frame bends.


Aluminum:

Pros - Very stiff, great for transferring power, lightweight. Not overly expensive.
Cons - Not a good shock absorber.

Comments - As stated, aluminum frames bend very little and as a result are great for power transfer. However, they do not absorb shock. A bike that does not absorb shock very well will transfer all shock to the rider resulting in early fatigue. After 30-50 miles you will start feeling in in your arms and legs.


Carbon Fiber:

Pros - Stiff, lightweight, shock absorbing material
Cons - Expensive, frame susceptible to cracks from being hit.

Comments - Love my carbon fiber frame! 

Titanium:

Pros - Stiff, lightweight, shock absorbing material, more resistant to cracks as compared to carbon fiber.
Cons - Expensive.

Comments - I'd love to have one of these.


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## saus (Oct 23, 2006)

Thanks, folks! Keep 'em comin' now, so that when the season begins, I'll be ready to spend more money!


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## Marc (Oct 23, 2006)

A bottom bracket is a prepackaged bearing system for your cranks.  It threads into the frame on either side and the crank arms attach onto either side.  The method of attachement varies, the old style is square tapered.  To keep the crank arms tight and without slop, each spindle that the crank arms sit on are tapered with threads into which the crank bolts attach.  As you turn the crank bolts it pushes the crank arm towards the thicker part of the taper to tighten them.

Square taper is undesirable as the surface area onto which torque is applied is relatively small.  They are susceptible to wear and eventually your cranks may not tighten completely and there will be slop.

To correct this, Shimano came out with their proprietary spline, which they call Octa-link.  There is a standard spline used by other manufacturers known as ISIS.  Both are far superior, and not much more expensive to manufacture, than square taper.  Obviously, your crank arms must be compatible with the particular bottom bracket spindle.


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## saus (Oct 23, 2006)

Wow! Great detail! MORE! MORE!! :-D   I'm lovin' this education!


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## Charlie Schuessler (Oct 23, 2006)

Spinning components such as wheels and cranksets are also available in aluminum or carbon fiber, lightweight and strong...


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## andyzee (Oct 23, 2006)

Charlie Schuessler said:


> Spinning components such as wheels and cranksets are also available in aluminum or carbon fiber, lightweight and strong...


 
At a definate premium


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## saus (Oct 23, 2006)

andyzee said:


> At a definate premium




Of course. We get what we pay for. 

My question: If you had to choose aluminum or carbon fiber for those kinds of components, and if cost were not a factor, which would it be?


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## Charlie Schuessler (Oct 25, 2006)

saus said:


> ...If you had to choose aluminum or carbon fiber for those kinds of components, and if cost were not a factor, which would it be?


If I were an average size person and money no option, carbon fiber frame, fork and components create a feeling on the bicycle that seems like floating on a feather, which is why professional racers set their equipment that way...

However being a big guy and still prefer to spend my fun money on skiing so I ride aluminum frame bicycles and components...


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## Marc (Oct 25, 2006)

Charlie Schuessler said:


> If I were an average size person and money no option, carbon fiber frame, fork and components create a feeling on the bicycle that seems like floating on a feather, which is why professional racers set their equipment that way...
> 
> However being a big guy and still prefer to spend my fun money on skiing so I ride aluminum frame bicycles and components...



Of the three, since I'm not a racer but just a casual rider, I'd still rather have a titanium frame.  Just personal preference though.


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## AHM (Oct 25, 2006)

*20 years of bike building experience................*

I have about 20 years experience building bikes: From high tech steel to carbon to Ti.  Next, I do not buy large brand bikes:  Trek, Cannondale, Giant, Specialized etc.  I use smaller custom frame manufactures because of a life long dedication to cycling.  I have ridden the large company bikes, and they are excellent.  If you get into the sport big, you may find you want a custom frame manufacturer.

Here are my thoughts.  There is some misinformation in AndyZee's very detailed info most of which is pretty good.


FRAME MATERIALS
Steel (CrMo):  Good steel rocks and is not cheap.  CrMo is a steel alloy as are most bikes (Ti included).  Ti and Carbon try to mimic the steel ride.  A good steel bike is made of Reynolds 853 and can cost 1000 - 2000 for an Independent Fabrications, Serrotta or Seven.  Don't overlook steel, the ride is fabulous both on and off road.  Recall, Ti and Carbon try to mimic the steel ride.  I have had 3 top end steel bikes and they all rode great.  Steel can rust and needs to be treated carefully.  Spray any steel frame with JP Weigles (sp) corrosion resistant spray.  Seven uses this on all their steel frames.  Good inexpensive steel frames can be found from Salsa.

Ti:  I also own a Ti frame (Moots YBB).  Ti is a fabulous material, lasts forever and if you look at the Lightspeed website you will see them drive over tubing that is Ti, Alu, and Carbon.  You can guess that the Alu crushes, the Carbon breaks, and the Ti is fine.  If longevity is your deal it is Ti.  The Ti ride is second to none.  For you carbon guys, there is no comparison.  A long rough road will show that Carbon doesn't really absorb that much shock.

I have rode my Moots for 7 seasons with 0 problems.  Not the case with most other frame materials.  Note:  I ride 1500 off road miles a year (single track) and have for 18 years.

Carbon:  common due to weight.  A carbon frame can go 2 lbs or so.  A ti frame can go 2 lbs, but the cost will be bigger unless you go with good carbon:  ie Look, Time, Colnago,Oribea(sp), Cervelo.

Frame Material and how to choose.

It all comes down to how you ride and how much you ride.  If you ride a ton (1500 off road miles or 2 - 3 k on the road) then buy the right bike and get a good bike--you obviously spend a lot of time on it.  I would go Ti for road.  I would go with an AL mt bike-- if you want some rear travel or if you want the ultimate singletrack racing rig, I would go with a Ti softtail (Moots YBB).

Also, look at where you ride.  If you are a century rider/tourer, then you want a little more comfy frame (ie Ti).  If you are a rec racer, then the stiffness of Alu or Carbon may be your thing.

Components:

Carbon:  This is a handlebar, seat post material primarily.  Carbon forks are a separate issue.  The bike industry thinks that 175 lbs is a big rider.  From that, choose carbon parts carefully.  Carbon parts are expensive:  road bar:  200 $ plus.  MTB:  100$ plus.  I use a Moots Ti bar.  A bit heavier, but much stronger.  Can you use a carbon bar.  Yep:  if it breaks, so will your colarbone, and maybe jaw (happend to a friend).  My Ti bar is about 160 g.  A good alu bar is 148 g and a good carbon bar is about 100 - 125 g.

Seat post:  in an off road application the post takes a great deal of shock.  I would never use carbon here.  Road bikes:  carbon is fine, not a lot of stress given a very consistent riding surface.

Cranks:  Carbon cranks are quite expensive and not really necessary, especially in an off road application.  Lots of rock damage may blow up your 400.00 $ carbon crank.

Forks:  Carbon forks are very good and quite common anymore.  Breakage has not been an issue and the weight savings/rider comfort makes these great.  However, stay away from integrated headsets.

Groupo or separate components:  Go with a groupo for your bike to start (ie Shimano Ultegra, 105, Dura-ace, LX, XT, XTR).  In reality, the second from top of the line is just fine if you are a serious rider, you do not need Dura ace, Record, or XTR.

Upgrade time:  when you buy a big brand bike they will cut some corners on components.  They typically use house brand seat post, stems, cranks (Specialized), etc.  These are great places to upgrade and lose weight.  House brand seat posts, HB, stems are heavy and cheap.  These let them use a high quality rear derailleur and then there own parts to keep the price down.

Good upgrades are as follows:

Handlebars:  MTB:  Easton Alu, Ti, or if you are comfy with it Carbon.  I would never ever use a carbon bar.  Road:  carbon here, but boy is that expensive.

Seatposts:  Thompson for the Alu crowd and Easton or FSA for the carbon crowd.

Wheels:  These are typically cheap on most bikes.  Cheap rims and cheap hubs.  Specialized will use a house brand front hub and many that show you Ultegra/Dura ace/XTR will use a very low brand hub.  

Once you get into riding a lot a custom set of wheels will be a huge performance boost and a weight savings.  For Road, it is typically pre built:  ie Mavic, Shimano, Campy.

Off road has prebuilt but I would just have custom built.  I use King hubs with Mavic rims. The king hub is the best made and will run forever.  They have 10 yr warranty.

Headsets:  Key item here.  Upgrade to a King if you ride off road.  King is lifetime, easy to maintain etc.

BB:  I'll leave this to Marc, but a square taper can still work just fine as long as you torque the crank bolts to the spec and check your spindle.  For off road, I buy an XT BB and replace it every year.................and I use square taper on my Moots--why> I have a custom crank (Race Face LP turbine) and when I bought it, ISIS was not around.  The upgrade cost would be huge (300 - 400) and not worth it in my opinon.  For the next bike, it'll be ISIS.........hopefully from King when the make the BB.  And when it comes time to clean and maintain my bikes..............there's a basement shop complete with an ultrasound machine to clean chains, derailleurs, rings, etc........a whole lot more maintenance than skiing!

Anything else, just PM me.


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## saus (Oct 25, 2006)

AHM, _*THANK YOU!!*_

That is quite a post and very informative. I won't react at this time to your suggestions, but I have a feeling I know where I'm headed (the poor house).;-)


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## bruno (Oct 28, 2006)

i have 3 bikes. all of different materials.

an aluminum fixed gear i use for everyday commuting and errands. great in the rain as i have fenders on it and it's rustproof. kind of a harsh ride though.

a steel fixed gear custom from IF that is my sunnyday bike. rides like a dream! very comfortable ride. and folks trip out over it.

a new custom IF titanium club racer geared bike. i've yet to ride it (i pick it up tuesday), but i've ridden ti bikes and they ride as well as (or better) than steel, are very lightweight and strong and are rustproof. but very expensive.:flag:   

havin' fun on whatever ya ride is more important than material i think. they're all bikes!!!:flag: :lol: :beer: :beer:


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## saus (Oct 28, 2006)

So far, except for expense, I haven't read or heard a single bad thing about titanium, and a lot of good stuff, including strong and rust proof.


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## bruno (Oct 28, 2006)

steel for beauty. ti for everything else!:-D ;-) :wink:  :roll: 

(ti can be ugly though, but i prefer to think of 'em as "businesslike")


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## saus (Oct 28, 2006)

Beauty is as beauty does, I say.


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## andyzee (Oct 28, 2006)

bruno said:


> steel for beauty. ti for everything else!:-D ;-) :wink:  :roll:
> 
> (ti can be ugly though, but i prefer to think of 'em as "businesslike")


 
I've never seen a ti bike that didn't look appealing. Then again, it could just be the fact that it's ti.


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## saus (Oct 28, 2006)

Gotta get into my Tour de Cure bike duds for a costume party. It's not the duds that are the costume - it's what will be on top of that. More later. TTFN and AMF


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