When is it time to retire a Frame/fork ?!

jon1981

Hi,

This is kind of prompted from another thread. I have an aluminium bike (with carbon forks) which is now about 6 yrs old. I probably do about 4k km on it a year with some winter long cycles. I guess you could call it my winter/commute bike.

Are there signs I should be looking out for that would indicate the frame is near end of life? How long should you get out of frame if you wash and clean it regularly or are they too many variables involved to say?

J

Lumen

12 High-End Frames in the EFBe Fatigue Test
http://www.sheldonbrown.com/rinard/frame_fatigue_test.htm


Thousands of load cycles

Lumen

...although at one load cycle (pedal revolution) per second, 60,000 load cycles is only 17 hours!

So I'm not sure how useful the chart is, though the article may be interesting.

jon1981

Thanks, the article is interesting, not sure the tests indicates much to me though. I don't know why but I've suddenly developed this paranoia of sudden frame failures on my Carbon and Alu bikes. Though getting a smack of a car is probably statistically more likely

magicbastarder

my understanding was - and someone please disabuse me of this notion - that carbon is stronger and does not fatigue, but if it does go, it goes much more abruptly than aluminium?

or in other words, will aluminium show signs like stress fractures, etc., before a complete failure?

Lumen

jon1981 wrote: »

Thanks, the article is interesting, not sure the tests indicates much to me though. I don't know why but I've suddenly developed this paranoia of sudden frame failures on my Carbon and Alu bikes. Though getting a smack of a car is probably statistically more likely

IMO it's more likely that your stem, handlebars, cranks, or pedals snap. You can mitigate this risk by replacing them every couple of years (well, maybe not the cranks).

The only frame failure I've had gave me a bit of notice via speed wobble. I did a few kilometres with a massive crack in the headtube. If the BB goes you'll get creaking before it fails. And for many other reasons!

Just make sure you do a bit of hands-free descending every ride.

jon1981

magicbastarder wrote: »

my understanding was - and someone please disabuse me of this notion - that carbon is stronger and does not fatigue, but if it does go, it goes much more abruptly than aluminium?

or in other words, will aluminium show signs like stress fractures, etc., before a complete failure?

My googling on the subject of carbon failures leads me to think it would be sudden, no warning signs.

On Alu, I'm not sure but given the forks are nearly always carbon they would be sudden failure.

Lumen

jon1981 wrote: »

On Alu, I'm not sure but given the forks are nearly always carbon they would be sudden failure.

Forks are incredibly strong. When they do fail it's usually because the bicycle has been ridden into something very hard, i.e. it is the result of a crash rather than a cause.

jon1981

I guess I should stop googling lightweight steel frames and put the credit card away so

NeedMoreGears

Looking at the DIN fatigue tests above, the loads are quite high 1200N is about 120kg - quite a bit more than the typical pedal force (maybe 25kg). I imagine/guess the impact of increased load is not linear and they use the relatively heavy load to allow them carry out the test in a reasonable timeframe.

ednwireland

Only 2 frames I've broken were steel . admittedly one cos I shoved a 7 speed into a 5 speed frame and the second went at the bottom of the seatube. 25 year old alu mtb an 7 year old carbon still going.

Lumen

NeedMoreGears wrote: »

Looking at the DIN fatigue tests above, the loads are quite high 1200N is about 120kg - quite a bit more than the typical pedal force (maybe 25kg). I imagine/guess the impact of increased load is not linear and they use the relatively heavy load to allow them carry out the test in a reasonable timeframe.

Indeed. 400N would be more likely (~2-2.5x average force).

NeedMoreGears

Looking at the fatigue life table for 6061-T6 aluminum (as you do)

A fatigue life of 100,000 cycles is reported for a max load of 47MPa. The life increases to a billion cycles at a load of 20MPa - the closest number I could get to 1/3 the load (i.e. the 400/1200 above).

So it would appear that if the frame can hang in there for 100,000 cycles at 1200N, it can last more than 10,000 times longer at 400N load - even Wishbone Ash couldn't wear out the frame! Obviously damage will reduce life considerably (if not immediately!).


MPa - is a the unit of the load/area ; basically pressure due to the pedal forces

Wishbone Ash

Lumen wrote: »

IMO it's more likely that your stem, handlebars, cranks, or pedals snap....

Please stop! :eek: I've 40,000kms on one of my bikes on the same bars and stem. The descent down Glenmacnass will never feel the same.

Lumen

Wishbone Ash wrote: »

Please stop! :eek: I've 40,000kms on one of my bikes on the same bars and stem. The descent down Glenmacnass will never feel the same.

It's OK, NeedMoreGears can feed you grapes and an apology when you're recovering in hospital from the results of his/her miscalculations. :pac:

benneca1

Have a 20 year old alu treck mtb done about a million miles all off road not a bother Only reason to worry about frame failure is to justify new bike

secman

My weekend Steed is a 24 year old Raparee colombus slx tubing. It was in storage for 10 years . It will be 25 next April and 5 years back on the road. Original cinelli stem , original bars... it does spring to mind on descents... and I block it out . A steel frame did snap on me previously.. well more like it didn't feel right and when I got off to examine it... noticed a joint had come away. Cycled back to house and swapped bike, stripped old frame and binned it.
My midweek bike is a cannondale caad 9.. about 6 years old.

The Ging and I

I took my 4th spin on a 48year old steel frame with most of its original components

com1

When is it time to retire a frame / forks? Very shortly after this happens...

https://us.v-cdn.net/6034073/uploads/attachments/93176/400411.jpeg

jon1981

com1 wrote: »

When is it time to retire a frame / forks? Very shortly after this happens...

https://us.v-cdn.net/6034073/uploads/attachments/93176/400411.jpeg

:eek::eek: your bike has a crumple zone!

magicbastarder

so does the front of the helmet, thankfully.

com1

jon1981 wrote: »

:eek::eek: your bike has a crumple zone!

Magic's picture (I robbed it - sorry Magic!) Though something similar happened to me back in the 80's - my Raleigh Scorpio (loved that bike) and a big rock had an abrupt coming together. I learned that while flying is great fun landing is a bi**h. I bent the frame back as straight as I could and continued for just under 1000 miles on it (over a couple of weeks) before things started to go badly askew... it is now rebar in the floor of a garage extension

magicbastarder

i was wondering when - if a frame is going to let go on you - in what context it'd be most likely to, outside of a collision or hitting a pothole.
would it be near the front when you're pulling hard on the bars on a climb, or nearer the bottom bracket when you're putting the power on, for example?