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Hello,

I'm about to buy a 2006 Fuji Roubaix Pro. It has carbon forks and an aluminum frame. The owner seems to have put a lot of miles on the bike. I'm worried, judging by its age it won't have the same stiffness it once had. How stiff will the bike be?
 

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Magically Delicious
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I have to ask where did that question come from? No, older carbon or aluminum will not loose it's original stiffness.
 

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Aluminum frames do fatigue over time and lose stiffness but it takes a lot of cycles before it becomes any sort of issue. Carbon does not fatigue in the same way and as long as it's undamaged it should remain as strong as new. In theory.
 

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Elitest thrill junkie
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FS bikes do, especially a lot of the mass-produced ones that use poor bearing systems. The bearings wear, the interfaces wear, they end up sloppy. New bearings usually helps, but they often won't be as stiff as on the show-room floor. This is partially due to ball bearings being a fairly poor choice for limited-rotation applications like bicycle suspension (bearings never get close to making a full rotation, so lube doesn't travel around the bearing and the races/balls wear unevenly). Better designs can significantly limit these issues, but a lot of the larger companies don't really care about 2-3 years down the road.
 

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FS bikes do, especially a lot of the mass-produced ones that use poor bearing systems. The bearings wear, the interfaces wear, they end up sloppy. New bearings usually helps, but they often won't be as stiff as on the show-room floor. This is partially due to ball bearings being a fairly poor choice for limited-rotation applications like bicycle suspension (bearings never get close to making a full rotation, so lube doesn't travel around the bearing and the races/balls wear unevenly). Better designs can significantly limit these issues, but a lot of the larger companies don't really care about 2-3 years down the road.
What would be a better choice than bearings? Bushings? Or another design? Seems there would be an opportunity if there really is something better than bearings, because most/all FS bikes use bearings, as far as I can tell.
 

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Possibly really strong electro magnets to to allow the pivots to hover within the space a bearing normally would be, might even take wear and tear down and create a softer feel with less drag. With ebikes, a good strong battery could potentially accomplish this.

In reality bearings work fine and distribute load well with minimal drag, some better than others. Maintain them yearly (more if needed) and just rotate them in the bore if you're worried about it. Or just replace them as needed.
 

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Self Appointed Judge&Jury
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Maybe go on an aircraft manufacturer forum for more in depth knowledge of said question.
 

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Elitest thrill junkie
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What would be a better choice than bearings? Bushings? Or another design? Seems there would be an opportunity if there really is something better than bearings, because most/all FS bikes use bearings, as far as I can tell.
Yes, but they are more expensive due to higher tolerances required in the frame. There are bearing systems that can work better, but again, more expensive. Most of what comes on a bicycle is pretty poor, leading to the excessive wear and sloppy frame.
 

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Out spokin'
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I currently ride a 2018 aluminum frame (FS).
Long time ago I owned a 2001 aluminum frame (also FS).
It took me 3 years to break the 2001 frame.
Back then I didn’t jump, didn’t do drops, was strictly an XC rider. But I rode a lot; over half a million feet vert every year.
A couple years, ~twice that.
I ride the heck out of my current aluminum frame. Drops, jumps, hectic rock gardens often at speed.
I don’t know how aluminum ages but one thing I can tell you for sure — late model aluminum frames are designed and built to be much stronger and more rigid than truly old ones.
Improved computer-aided design, shaped, larger diameter tubes, gussets wherever appropriate... aluminum frames have improved dramatically throughout the past 20 years.
Not saying the 2006 frame you’re considering buying has any flaws, other than it was designed and built 15 years ago and that both design & construction have made leaps since then.
=sParty
 

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CEO Product Failure
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For me this conversation starts with the warranty: http://www.pgwbike.com/docs/warranties/PGW_Fuji_Warranty_U.S.A.pdf

Then condition of the bike: mileage, weight of rider (stress put on frame/components), exposure to UV (a bike in AZ is different than a bike in Seattle), and any scratches/chips in clear coat or painted finish. Regarding mileage--this related both to the amount of wear & tear, as well as, the amount of sweat. Sweat corrodes a lot of components.

The fact that the manufacturer only offers a limited warranty to the original owner is a red flag for me.
 

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Theoretically aluminum eventually fatigues after so many cycles, and carbon does not if within limits of its design.
there are other considerations tho. The number of cycles for aluminum depending in the alloy and amount of stress can be so ridiculously high it wouldnt be a concern.
There is a possibility of uv and chemical damage to the resins in carbon.
Warranties i take with a grain of salt. Theres lots of products backed with great warranties but arent that great. They just have the resources to just replace whatever.
 

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Lol, i didnt even realize the original question. I dont think it will have appreciably lost any stiffness. If it did, that means the material is yielding and failing.
Examine with a fine tooth comb. Test ride if can and listen for any creaks.
 

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Self Appointed Judge&Jury
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Because we have so many people on this site that know everything about everything. This is the place to go to ask technical material fatigue qualities.
 

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Because we have so many people on this site that know everything about everything. This is the place to go to ask technical material fatigue qualities.
There are a lot of engineers who are into bikes. I'm sure some even post on mtbr...
 

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Self Appointed Judge&Jury
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There are a lot of engineers who are into bikes. I'm sure some even post on mtbr...
And a lot of “want to be” engineers who just post whatever pops into their minds. Lol
I’ve been here long enough to see it day in and day out. There’s some topics that just shouldn’t make the airwaves on this site.
 
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