Frame Materials for Big Riders

YO UNC:  In no way am I asking which bike model to purchase! Your warning against that scared me straight. But I’d like to know about frame materials: steel, titanium, carbon, aluminum. I'm not small. I’m 6-foot-1 and will never see 185 pounds again. I need a material that will last if I'm going to drop a big chunk-o-change. I'll worry about price later. What are some guidelines for choosing a frame material other than what is newest, hi-tech and expensive? -- Patrick G.

UNCLE AL FIRES BACK:  First, don't go for the lightest stuff, whatever it is. It doesn't make sense for us big dudes to shave grams at the cost of reliability.

I have three road bikes and each is steel. Two are Reynolds 853 with carbon forks, the other is some old Vitus steel frame and fork. It’s my winter bike.

I can't prove it by my experience, but it’s said that the light aluminum frames have a fairly short lifespan. I know plenty of riders on old aluminum bikes -- Cannondales, Kleins, Treks -- that show no signs of ever giving up. But those are not the new scary-light framesets that have some people concerned.

Carbon intrigues me, and guys I know who ride it say it’s great. The problem is, you and I outweigh these guys by 50 pounds. I had a carbon frame years ago, but it was noodle-like under my (if I do say so) smooth pedal stroke. From what I understand, though, the new carbon stuff is really strong and stiff even while transmitting very little road shock. It's the material I’ll most likely be on next. I know carbon doesn't like crashes. Well, neither do I.

Titanium, the hottest buzz in frame materials, is excellent, albeit expensive. It used to be horrible, before the smart guys figured out how to make it stiff in the right places and reliable. When it’s unpainted, it’s boring to me. I like paint because it demands attention to keep it nice. It doesn't let us slip into the "I don't need to clean it" stupor.

I've seen as many broken Ti frames (all at the welds) as with any other frame material. You need to clean your bike so you can see if something is cracked or otherwise screwed up. The pros ride clean stuff so it looks nice, but their mechanics are protecting them from injury as well. Every kind of frame material can, and does, break. Make sure you know what condition your equipment is in.

One point for folks who are heavy but not tall: Look into getting a custom-made frame. Production frames typically use heavier tubesets for the larger sizes, and lighter tubesets for smaller sizes. A 225-pound, 5-foot-5 bodybuilder needs a much stronger frame than a petite 5-foot-5 woman, even if they ride the same size.

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Lifespan of a Carbon Fork

DEAR UNCLE AL:  How does one gauge the life expectancy of a carbon fork? In miles? In conditions of use? I'm a club rider who does around 5,000 miles a year. --Tim A.

UNCLE AL FIRES BACK:  There's no hard-and-fast answer, Tim. A good rule is that when you hear little voices of doubt in your head, take heed and replace the fork.

That's what Fred Matheny had me do to his Litespeed Vortex this year. He regularly bombs down twisty, 50-mph descents in the Rockies and didn't like thinking that the bike's 7-year-old carbon fork might be ready to give up the ghost. Or turn him into one.

On the other hand, RBR's Ed Pavelka has the same-year Vortex and it still has the original Kestrel EMS fork. Ed rides in a pretty flat area on mostly smooth roads, so he isn't as concerned as Fred about sudden fork failure. But he's starting to think about it now that the bike has some 30,000 miles.

I don't know of a published life span of carbon. I do know that Trek, for instance, gives a lifetime warrantee on its bikes with carbon forks.

If you've piled into a pothole at speed and now you wonder, take your bike to your favorite mechanic and ask him politely to check out the fork and give an opinion.
 

FEEDBACK FROM ALEX S.:  Carbon composites, without special detection equipment, don't tell you when they are hurting (damaged). They only tell you when they are broken (critical failure).

A well-designed and properly manufactured composite part will last a very long time when used within the intended loading envelope. Crashes are generally not part of the intended loading. Take your bike to a mechanic for an inspection if you've had a crash. However, no mechanic can reliably detect delaminations and cracks below the surface. Keep the voices in your head in mind.

Profile has a $130 crash replacement policy. I replaced a fork that I crashed on, even though the only visible damage was a nick in the back of one leg. Was the nick big enough to compromise the fork? Maybe, maybe not. But $130 is pretty cheap insurance.

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High-Speed Shimmy

BIG AL:  I have a 56-cm Trek 5200 with Ksyrium wheels. I've ridden it for a few years without problems, but in the last few months the bike has developed a shimmy, wobble wiggle (whatever) at speeds of 40+ mph.

Here's the kicker: I haven't changed anything on the bike, nor is my body or riding style different. The shop has pulled the bike apart and can't find anything that could cause this problem. Am I crazy? -- Lorri Lee L.

UNCLE AL FIRES BACK:  Assuming everything is adjusted properly (no loose headset or head cups or brinelled cups) and your frame is not misaligned from a crash, and your tire pressure is normal, and your hubs are not loose and you are indeed not crazy and descending with no hands at 45 mph, I have no idea.

Shimmy usually happens because a frame lacks lateral stiffness. Oscillation occurs between the two gyros (the wheels), most often at speed. Clamping your knees against the top tube with your crankarms horizontal will usually stop it.

Normally, this problem occurs when coasting, but it's been known to happen while pedaling, too. Weird crosswinds can cause a lightweight frame to shimmy on occasion. But if it's happening every time the bike goes over 40, take it to a framebuilder to get his or her very expert opinion.

A severe shimmy struck to my wife's bike during a windy time trial last spring. It scared her to death. But it hasn't happened again, even at higher speeds. Go figger.
 

INSIGHT FROM  AUSTRALIA:  I've cured shimmy on a road bike by slightly tightening the headset bearings. Slight, not overtight! -- Tozer
 

FEEDBACK FROM RON R.:  I experienced three severe episodes of high-speed wobble and then found the solution. To explain, here's a little background.

I ride a 60-cm Trek 5200. The size is a compromise because I'm 6 feet tall with a 35-inch inseam. I could have taken a 63-cm frame in terms of  leg length, but the top tube would have been too long. So I went with the smaller frame. The guy who fitted me also put on a shorter stem, feeling that my reach was a bit too long.

The three severe wobbles came at different fast speeds while descending. Dave, the shop owner noticed that my weight looked a bit too far to the rear. He suggested that I move forward when descending, keeping weight over the handlebar, and get a slightly longer stem. He also suggested putting at least one knee against the top tube as a damper, especially at speed.

This all made sense to me, as I recalled that in all three wobbles, I had pushed back on the seat, getting my head low and just over the bar. And in each case, I was going into a headwind, too.

My education was further enhanced by reading an article by Jobst Brandt. He suggested getting off the seat if a wobble developed, as the fulcrum of the oscillation is typically around the seatpost.

Armed with this new approach to body positioning, I have never again experienced a wobble. This includes a trip to Europe this summer, where I descended Mont Ventoux (took me a lot longer than Lance to get up the beast!) and numerous other Alpine passes without incident.

I hadn't realized that body position could be so significant, or that just a few inches change in position could have such a stabilizing -- or de-stabilizing -- effect. Obviously, this info isn't going to help anyone who has a damaged headset, cracked frame, badly out-of-round wheel, and so on. But for those who encounter the "mystery" wobble, which seems to occur for no obvious mechanical reason, consider your own contribution as the possible cause.

AL'S RETURN FIRE:  Ron's experience proves that shimmy is unpredictable and can't be laid to one cause for all cases. Jobst Brandt, an engineer and real smart guy about bikes, even says that a crooked frame might be less prone to shimmy than a straight one.

Watch what happens as superbikes decelerate on Speed Vision TV when they use onboard cameras. Same wobble, only those guys just hit the throttle to come right out of it. Those factory bikes have the finest design standards there are for two-wheeled, high-speed travel.

So I don't think shimmy is so much a design problem as it is dictated by bizarre conditions we encounter. No one has really come up with a definitive explanation so far. Maybe it's just a problem with two wheels?

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