Flex in carbon forks
damocles10
Posts: 340
Hi all.
I have recent noticed a potential problem, hopefully it's normal but I would like to check on here before going to the LBS.
I recently changed my wheels and I noticed the left side ( the side with the quick release ) of the forks has quite a lot of flex, with the wheel unlocked I can move the left fork leg quite easily around 1.5 to 2 cm sideways, there seems no resistance when I apply pressure.
They are around 7 years old, could this be a weakening in the forks structural integrity? I was surprised they moved laterally so easily and don't want to be in a face plant situation.
Thanks for your help.
I have recent noticed a potential problem, hopefully it's normal but I would like to check on here before going to the LBS.
I recently changed my wheels and I noticed the left side ( the side with the quick release ) of the forks has quite a lot of flex, with the wheel unlocked I can move the left fork leg quite easily around 1.5 to 2 cm sideways, there seems no resistance when I apply pressure.
They are around 7 years old, could this be a weakening in the forks structural integrity? I was surprised they moved laterally so easily and don't want to be in a face plant situation.
Thanks for your help.
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Comments
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Are they flexing along the length or is the blade loose at the crown? Some more basic forks are a carbon blade bonded to an alloy crown and it's not unknown for galvanic corrosion to occur between the carbon and alloy resulting in a degraded bond - a loose blade would show as a crack around the fork crown like this:
https://lh5.googleusercontent.com/_n-iYAzrwnBk/TUKpvAdyGTI/AAAAAAAAAhc/p_5g3m4Ok2o/s800/IMAG0070.jpgMake mine an Italian, with Campagnolo on the side..0 -
Are they flexing along the length or is the blade loose at the crown? Some more basic forks are a carbon blade bonded to an alloy crown and it's not unknown for galvanic corrosion to occur between the carbon and alloy resulting in a degraded bond - a loose blade would show as a crack around the fork crown like this:
https://lh5.googleusercontent.com/_n-iYAzrwnBk/TUKpvAdyGTI/AAAAAAAAAhc/p_5g3m4Ok2o/s800/IMAG0070.jpg
I have just had a look at the link to your photograph. I do not see that extent of damage, but, on the inside of my forks on the left hand side there is what can describe as a scar across the width of the forks at the same point the flaking occurs in your pic. It looks like there has been some kind of friction contact, a bit weird, I will send over a pic tomorrow as it's late here. I am concerned....is it safe?0 -
I'm following this with interest, as I have a flexy fork (pointed out by my LBS) with similar marks on the shoulders, although I was pretty sure they were caused by the fork scraping on the bike racks at work0
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Just taken a pic, excuse the dirt.
It actually looks worse with a flash on.
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Usually marks like those are caused by stones/debris being trapped between wheel and fork in my experienceFFS! Harden up and grow a pair
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Not sure if its a trick of the light, but about an inch below the scrape (towards the crown) the leg looks to have been squashed/deformed a little. I'd have a close look at that area whilst wiggling the flexy leg to see if anything is moving.Rose Xeon CDX 3100, Ultegra Di2 disc (nice weather)
Ribble Gran Fondo, Campagnolo Centaur (winter bike)
Van Raam 'O' Pair
Land Rover (really nasty weather )0 -
I had a hairline crack appear in the paintwork in exactly the same place on an old bike. It was a crack developing and was replaced under warranty. I would not ride on it full stop.0
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Thanks everyone.
The leg doesn't appear deformed when I inspect it and there doesn't seem to be any movement there when I flex it. The debris theory is possible but I think I would notice if something had enough force to scar the surface - it could happen. It is definitely contact damage - I had a bad crash a few years back ( 25mph in to a heavy cone ), could the wheel/tyre deflect to make contact with the forks and burn a groove? My front 404 Zipps where slightly buckled after the accident. [edit] The Zipp 404's are wider below the braking surface.
For peace of mind I will take it to my LBS, with London roads in such a state I do not want to hit a pot hole/bad surface and snap the forks and eat tarmac.
Unfortunately it's out of warranty.0 -
These are the marks on my fork shoulders. Again the flash makes it look deeper than they are. I can't decide if it's just scrapes from bike racks, or if I need to be worried. Anyone want to pass comment?
I've emailed my LBS who have passed it onto their warranty manager so we'll see what they say
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TBH i wouldn't like to ride that. Fork failure is not something i would ever want to experience and that does look like the carbon has been exposed/damaged.0
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First, it's an all carbon fork, so no worries about corrosion. Looks like the mark is simply due to rubbing e.g. rattling mudguard - the distortion mentioned by previous poster is simply the way that the top-weave coating has been moulded. FWIW the top weave is purely cosmetic - the strength of the fork is due to the underlying UD fibres. From the photos, there's nothing that immediately causes concern. However, I would remove the wheel and flex the fork under a strong light and check for signs of any movement. A DIY dye penetrant test could be to use a coloured spirit marker pen over the area and then wipe if off with a cloth with some light solvent (e.g. meths) - if there's no crack it would wipe clean.Make mine an Italian, with Campagnolo on the side..0
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First, it's an all carbon fork, so no worries about corrosion. Looks like the mark is simply due to rubbing e.g. rattling mudguard - the distortion mentioned by previous poster is simply the way that the top-weave coating has been moulded. FWIW the top weave is purely cosmetic - the strength of the fork is due to the underlying UD fibres. From the photos, there's nothing that immediately causes concern. However, I would remove the wheel and flex the fork under a strong light and check for signs of any movement. A DIY dye penetrant test could be to use a coloured spirit marker pen over the area and then wipe if off with a cloth with some light solvent (e.g. meths) - if there's no crack it would wipe clean.
Ah right. Apologies if my post concerned you OP. Listen to Monty, his insight and advice on carbon issues is always spot on.
Hope you are able to sort it quick.0 -
First, it's an all carbon fork, so no worries about corrosion. Looks like the mark is simply due to rubbing e.g. rattling mudguard - the distortion mentioned by previous poster is simply the way that the top-weave coating has been moulded. FWIW the top weave is purely cosmetic - the strength of the fork is due to the underlying UD fibres. From the photos, there's nothing that immediately causes concern. However, I would remove the wheel and flex the fork under a strong light and check for signs of any movement. A DIY dye penetrant test could be to use a coloured spirit marker pen over the area and then wipe if off with a cloth with some light solvent (e.g. meths) - if there's no crack it would wipe clean.
A 2cm flex in a fork does not sound in any way safe to ride on to me. Especially if it is flexing more than the other fork. I have been on a bike with a fork failure. This was a snapped qr lug on an old Peugeot Alu frame many years ago but the whole coming off at speed cos of fork failure is seriously bad news. I would not ride on it again until I had 100% proof its cosmetic and not broken. The fact that it is so visable means if it were to break no insurance would pay out for the bike or rider. Same as driving an unsafe car would invalidate your insurance if its reasonable to assume you should have checked it over.0 -
What's so visible? There is no serious damage visible. Monty has advised him how to look for a deeper crack. Yes, it's sensible to check for a deeper crack but your point about insurance is irrelevant.
A 2cm flex in a fork does not sound in any way safe to ride on to me. Especially if it is flexing more than the other fork. I have been on a bike with a fork failure. This was a snapped qr lug on an old Peugeot Alu frame many years ago but the whole coming off at speed cos of fork failure is seriously bad news. I would not ride on it again until I had 100% proof its cosmetic and not broken. The fact that it is so visable means if it were to break no insurance would pay out for the bike or rider. Same as driving an unsafe car would invalidate your insurance if its reasonable to assume you should have checked it over.0 -
What's so visible? There is no serious damage visible. Monty has advised him how to look for a deeper crack. Yes, it's sensible to check for a deeper crack but your point about insurance is irrelevant.
A 2cm flex in a fork does not sound in any way safe to ride on to me. Especially if it is flexing more than the other fork. I have been on a bike with a fork failure. This was a snapped qr lug on an old Peugeot Alu frame many years ago but the whole coming off at speed cos of fork failure is seriously bad news. I would not ride on it again until I had 100% proof its cosmetic and not broken. The fact that it is so visable means if it were to break no insurance would pay out for the bike or rider. Same as driving an unsafe car would invalidate your insurance if its reasonable to assume you should have checked it over.
Im not sure if you actually read the original post. Regardless of any pics or interpretation of what looks normal etc the op says he has a 2cm flex in the fork. Regardless of how it looks in a pic that is not normal and was also his primary concern. Carbon can be broken and have no immediate visable signs of damage of fatigue. I would not ride a bike that displayed any out of the ordinary signs of wear or fatigue. And if it were to break at the point of the marks the insurance company would no doubt investigate this. They are not in a business of giving away money for free.0 -
the insurance company would no doubt investigate this. They are not in a business of giving away money for free.
rather depends if the bike is insured for damage ...
I wouldn't base my decision to ride it or not based on what the insurance company may or may not do - I'd be more bothered about the fork failing whilst I was on it - 2cm wobble doesn't sound right.0 -
the insurance company would no doubt investigate this. They are not in a business of giving away money for free.
rather depends if the bike is insured for damage ...
I wouldn't base my decision to ride it or not based on what the insurance company may or may not do - I'd be more bothered about the fork failing whilst I was on it - 2cm wobble doesn't sound right.
Thats what I said in the first place. I have had a fork fail and although it was at relatively slow speed I took a heavy impact. I did say right at the start the bike shoukd not be ridden until the fork is inspected and shown to be safe.0
