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Momentum and inertia on an older bike
#1
I've got an old Bianchi Strada that's getting just plain hard to pedal. A real grind. Every crank. Wheels are trued. Nothing rubbing. Just nasty.

A sales guy at a bike store says old aluminum frames get that way. True? Or a riding technique issue?
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#2
"old frames get that way"? I have no idea what that guy meant unless he is trying to claim that the metal of the frame fatigued and is now more flexible and absorbs energy. I think what he was really saying was "you should buy a new bike from me as I'm on commission and sales are down..."

Unless the frame cracked somewhere, they don't really change.

Sounds like your bearings are worn. Gummed up or damaged wheel and bottom bracket bearings will add a significant amount of resistance to the bike. Try taking off your wheels and turning the axles by hand. They should be smooth with almost no resistance. Same thing if you turn the pedals with the chain off the chainrings.

A worn or excessively dirty chain will also add a lot of friction.
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#3
Thanks for the insights. I just had this tuned up, and for fifty miles or so it was rolling really well. Now it's like I say -- a grind. I go about 240, so I'm not expecting to go real fast, but it would be nice if I could go with a little less effort. New bearings might help. How much would you expect to pay for a set (assuming I put them in myself)? Any other thoughts?

Thanks again
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#4
Hm. I'd say, open the hubs and take a look at the bearings (assuming you have cup and cone bearings). Look at http://sheldonbrown.com/cone-adjustment.html

If you see any pitting (most probably on the cones), the hubs are shot. You could try to find replacement cones (good luck with that), or replace the wheel with a new hub (how good are the rims?) or buy a new wheelset. Hubs range from 10€ (dunno, 13USD) for simple front hubs and 15€ for entry level rear hubs to about infinity. Rims are also in that range (<20€ for a simple, box rim, ~30€ for a Mavic CXP). Wheelsets (nice, entry level, robust) start in the 100€ (130 USD) range. I think it is difficult to build a wheelset yourself for this price, since decent hubs + rims + spokes are not much cheaper, I like doing it, though.

Concerning the bottom bracket, look at http://bicycletutor.com/check-bearing-wear/
it is a nice method. Bottom brackets start also around 10€. Removing them (well, the fixed cup on the left) can be a hassle, be warned.

Also check whether the chain is gummed up, depending on how you treat your chain (lubricants etc.), gunk will collect on it. Removing it helps quite a lot (as Dave mentioned).
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#5
Thanks. All good. Most helpful.

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#6
Go through all the bearings including the pedals. Clean them out and inspect as advised above. Check that everything spins freely with-out being loose. Make sure the tires are inflated properly. Check the saddle height is right for you?

You say that after 50 miles the bike feels sluggish. That's not unusual if you are not feeding and hydrating during the ride.

Also has your fitness gone down recently or have you had an illness lately? A cold or virus will really affect your performance.

Regarding the frame, (speculative) if it has hardened, then it will take it out of you because of the pounding your body gets during a ride. Aluminum is prone to giving a harsh ride.
[font=Trebuchet MS]Ride hard or ride home alone![/font]
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#7
"Regarding the frame, (speculative) if it has hardened" -cyclerUK

Just wanted to ask if you are aware of frames actually changing their properties over time as bigmanlittlebike says the shop guy claimed. I know metal can fatigue over time and get weaker. But I've never heard of a frame getting stiffer. Wondering if there is anything to back this up or just urban legend. I know a lot of aluminum frames are considered stiff and do not damp vibration well so are considered a rough ride. But we're talking about the properties of the frame actually changing.
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#8
Hi DaveM,

No! nothing to back this up (purely speculative?). Certain aluminum does harden though and fatigue over time when subjected to work forces.

I have not heard of "old frames get that way" and may just be , as you say, "salesman" talk? Generally though "work hardening" does make metal less flexible and in the end will fail.
[font=Trebuchet MS]Ride hard or ride home alone![/font]
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#9
I found this: http://sheldonbrown.com/brandt/frame-soft.html

He is speaking more specifically to the idea that steel frames "get soft" over time, which I have heard before. I suspect the "aluminum frames get stiff" is a variation on the same theory.

Everything I could find in my (brief) search indicates that frames do fatigue from use and are more prone to break. But that the ride quality will not change at all. It does appears that this is a general old wives tale that gets passed down from cyclist to cyclist. It may have started out as an excuse to talk people into buying new bikes. But bikemanlittlebike's sales guy was probably repeating "wisdom" he got from some guy and not purposely scamming you.

I remain convinced frames do not get stiff or soft over time unless someone can show me some evidence or a valid metallurgical argument.
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