Friday, February 6, 2009

What to Buy?

I was reading an old Bicycling Magazine last night, the annual buyer's guide from last year. I looked at the cover to find the month of issue - April. I resolved to get busy and write something in my bicycle blog about purchasing a new bike. Better me, having just gone through the process 10 months ago, than an industry rag hawking the wares whose advertisers pay the most.

First and foremost you must buy the frame. I'm not suggesting you have to literally buy a bare frame and build the bike up using all hand-selected parts, although that is exactly what I will do next time, but be aware that you can replace every other part on the bike except the frame, so you must consider the frame first and foremost. A good frame is like a savings account, it will continue to pay dividends over time as you upgrade worn out parts and slowly grow into the bike as your conditioning and preferences in rides change.

A good frame should do a lot of things well and not be overly prone to damage, but above all, IT MUST BE THE CORRECT SIZE. Moulton's system is the best one I have ever found. It correctly explained why at 5'9" I should be riding a size 54 frame, and not a size 48 or 49 based on my inseam. I have the feet and torso of a guy 6', and the inseam of someone 5'5". The frame and stem are fit to your torso in this case, not your inseam. I therefore ride a 54mm frame and a 120mm stem with my seat slid forward. It works beautifully. If you are riding a bike with a stem shorter than 90mm or longer than 130mm, you almost certainly have the wrong frame size. Please study this chart thoroughly before you venture into a LBS. The difference between ignorant and arrogant bike salesmen is often 15 minutes.

The 2nd biggest decision in buying a bike with a good frame is the material the frame is made out of. The choices are really steel, aluminum, titanium and carbon fiber. Steel is the classic frame material, and the material has one huge advantage, it has a fatigue limit. Aluminum does not. All aluminum components, including, and especially the frame, will fatigue to zero strength after some number of fatigue cycles. Steel is also the strongest material by volume, and unfortunately for bike frames, it is too strong.

This because as you make frame tubing larger and larger in diameter the strength of any such tube increases with the cube of the diameter. Two inch tubing isn't twice as strong as 1" tubing, its 8 times as strong. It didn't take tubing mfgs long to figure out they could double the tubing diameter, make the tube walls half as thick, and still end up with a tube 4 times as strong. If you continue with this process long enough you will make the tubing walls so thin you can crush them with your bare hands. This is called the "beer can" effect, and forces steel tubes to be made with walls a lot thicker than is required for the strength of the frame. However, steel will only fatigue down to about 80-60% of its original strength and then fatigue no more no matter how many fatigue cycles it is subjected to - we are talking billions of cycles here. The Eiffel Tower, if properly maintained, could easily last 10,000 years, not the month it was designed for.

So, why not use a material that is less dense, like aluminum? You can make large diameter tubes that have thick walls that won't "beer can" and they will still be light. Yup, and they will fatigue to failure in short order leaving the rider in a bloody mess in the street, and eventually, sobbing in front of a sympathetic jury. So why not add in some extra strength reserve so by the time the fatigue factor is getting critical the bike has been melted down into a TV dinner tray?

Well, this is what is done, but the result is very stiff tubing and very stiff frames, and unfortunately, aluminum transmits road vibration like a super-conductor. These frames will eventually fail, but not for many years of normal use. In addition aluminum doesn't rust, in part because only metals with iron in them rust. This does NOT mean aluminum doesn't corrode more or less in the same way as steel. It does, but this is almost never the failure mode for aluminum - fatigue life is. Keep in mind that "mega scale" stiffness, the stiffness that resists frame flex, and a material's propensity to transmit rather than attenuate high frequency road vibration have little to do with each other. Friends don't let friends ride aluminum.

So if steel is too dense and strong. and aluminum isn't dense enough and is too weak, how about we pick something in the middle - like titanium? Titanium is a great choice, and makes beautiful, corrosion resistant tubes. It makes for expensive bikes though, as it is an expensive material, must be welded in an oxygen-free environment, and is very abrasive for machine tools to fabricate. It also doesn't have the fatigue resistance that steel has, but it's a lot better there than aluminum, so the tubes can be made fairly small and thin for a very nice ride.

Almost every bike you buy today will have a carbon fiber fork. It's not because CF is the easiest material to make forks out of, it's because CF has this amazing ability to kill the high-frequency road vibration that numbs your hands, wrists, butt and feet. For the most part this is because in tension CF is a string, and in compression it is a reinforced piece of plastic tubing made up of epoxy and thread. Plastic doesn't transmit vibration very well at all, and very happily so. (I suspect vibration transmission, or lack thereof, is closely related to a material's efficiency in transmitting sound, but at this point that is just conjecture, not researched fact) My particular bike adds still more vibration damping by adding silicone inserts into the fork, seat-stays and seat post. I also bought a CF handlebar stem and when funds permit, I will be riding a CF handlebar, and perhaps, a CF aerobar.

I knew most of this information when I was looking for my bike courtesy of a neighbor who has been a bike mechanic on and off for 30 years. We went to a LBS because they had a killer deal on a LiteSpeed Ti bike, and he just insisted I look at it. Unfortunately, it was not even close to my size. I noticed the CF forks on all the aluminum and steel bikes and started looking at all CF bikes. I had ridden the Trek Madone 5.2 and it was a revelation, so I asked the salesman to show me the cheapest full CF bike they had knowing I would eventually customize the bike and replace most of the parts. He put me on a Specialized Roubaix and I was hooked.

I ended up buying my Roubaix from an online ad, but had to drive a couple of hundred miles to pick it up, as Specialized, like most of the high-end makers, doesn't want to undercut their dealer network so they are not allowed to sell their bikes online. I had narrowed my search down to the Roubaix or a Felt. I got a great deal on my Roubaix because though it was a NIB bike, it was an '06 model and had a 9-speed gear train. With metal prices so high Specialized had put much cheaper components on the '08 Roubaix of the same model, so I saved almost a grand over a comparable '08 model two levels up. I also knew I'd use the savings to customize the bike with the components I wanted, instead of being stuck with choices Specialized made. Finally, I wanted a triple and not a compact gearing system because we have lots of mountains in California. It was a good fit.

My friend has a custom built Pegoretti, he loves it, and it is a very nice bike, climbs extremely well, and has almost zero flex, but I would not buy another steel bike because metal just beats me up too badly. In fact, I used CF spacers between the top bearing on my headset and the bottom of my CF stem to eliminate any metal to metal vibration pathway. The CF stem, a Ritchey, has an aluminum core, which they really use as a mold, but since it is impractical to remove it after the CF is baked they make you a present of it. With the combination of both aluminum and CF the stem is 3X the strength of an aluminum stem and you don't have to worry the stem will fail from fatigue in the future. It's just ridiculously stiff mounted right down on the headset, and I love it. The wheels are now the weak point in climbing out of the saddle.

This is all well and good, but aluminum is horrible for vibration transmission so before the vibration can migrate from the bottom metal bearing race through the top tube into the top race, and then into the stem, I block it with a 3mm CF spacer. My fork has a CF steering tube, so that vibration path is well damped. An all CF stem and CF handlebars would provide still more damping, but I'm on a budget, so I have to take my hands off the bars occasionally and "thaw them out". You do what you can and live with the rest.

Since I am fighting carpal tunnel I also ride with Fi:zik gel tape and use the excellent Torelli Moda Chunky handlebar tape over that. The Fi:zik handlebar tape is junk, but the gel tape is excellent and can be reused time and time again, although with the Torelli tape, that might be a few years unless you crash.

My next surprise was that bikes no longer come with pedals, and while they come with seats, they shouldn't bother, because all the places where you interface with the bike require very tailored solutions. It took me 4 seats to find one that worked well with me, the chamois in my shorts, and the seat post. As for the pedals, I ditched a perfectly good pair of beautiful old Shimano SPDs in favor of the new wider SPDs that are really a LOOK clone. LOOK had it right, Shimano had it wrong, so Shimano caved and copied.

The old Shimano SPDs have a very small area that contacts the shoe, and after a few hours they tend to create "hot spots" under the balls of your feet. It got bad enough that after a 5 hr ride I was limping, so I shelled out the money for new pedals - Ultegra PD 6620s. Problem solved. The important thing is to get a pedal that has steel on top or you will be buying new pedals every year instead of new plastic cleats.

I also replaced the stock 12-25 cassette gearing in the back, and not for any obvious reason. Shimano cassettes are really just a pile of parts, except that on the higher end cassettes, Ultegra and DuraAce, there are aluminum spiders or carriers that steel gear rings are pinned to. This saves weight, but that is not very important. What is important is the aluminum carriers span the width of 3 gears and 3 spacers so that the contact area between the gears and the splines on the wheel hub is 9 times as great. After one very steep climb I was shocked to find that my large back cassette gears almost tore through their splines and started spinning, ruining the wheel. I replaced that cheap POS with an Ultegra 12-27 cassette and it has performed beautifully ever since.

I have replaced tires, front chainrings, brakes, handlebar tape twice, the chain, the seatbag twice, lights, reflectors and cut 15mm off my steering tube to get my head down in the wind. The Ritchey stem is a 120mm, up from the 100mm stock stem, and I pitched the 20mm tapered headset collar/spacer. All in all I have dropped the handlebar position about 30mm. What I have not done is run out of frame. I still love the frame. It does everything well, and nothing superbly. That makes it very versatile.

My Roubaix still has its plush bike DNA, but it has come a long way in the Tarmac direction since I rolled it out of the bike shop smiling ear to ear. With 31.8mm handlebars low and forward, a stem 3X as strong as normal, and the stem a mere 3mm from the top headset bearing, I ride one of the stiffest front ends on the road - and yet am well protected against vibration. Everything on the bike is aerodynamically clean and while I am not a slave to weight, I pay attention to what I carry - especially in my seat bag. Go small. (The bigger the bag the more junk you'll stick in it) I ride for efficiency and really sweat the details to use my limited physical resources to optimal results.

I rock the hills with the best of them, but the long chainstays and compact frame don't make it as easy as a Cervelo R3-SL would. My triple crank is now sporting 46/38/24 gearing and I can ride straight up 8-25% grade all afternoon in the saddle. I run out of gears over 30mph but the wind drag will eat you alive above those speeds, so it's a trade-off I am happy to live with. I still hit 55 in a tuck going down a half-dozen grades around Sacramento, and love the sure and brutal stopping power of the new SRAM Force brakes. The point is, a bike is a trade-off that is very personal, and most of those trade-offs can be changed so long as you have a good foundation - the frame.

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