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Discussion Starter · #1 ·
I took my giant tcr adanced for a loop Saturday. Near the end of the ride I heard a banging from crank. At 1st I thought I was just hitting the cadence sensor. The road was busy and it was a while before I stopped. The magnet in the end of the pedal of the crank scratched the heck out of my giant tcr advanced. Any suggestions. Bikes usually break near top tube. But I am concerned for cosmetic and safety issues.
 

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What the what???
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I'm not a carbon guy, but posting a pic of the damage might help those who are.
 

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Discussion Starter · #3 ·
Opus51569 said:
I'm not a carbon guy, but posting a pic of the damage might help those who are.
i have 2 carbon road bikes and 2 mtbs not carbon

here's the bike in question from earlier this year, you can see the cadence sensor albeit its on the far side of pic



i posted my dismay on mtbr about getting a carbon mtb, and people posted that i'm nuts as today planes are made of the stuff

i was thinking about putting a couple of drops of krazy glue on the damaged spot as i did fix a wood banjo once this way. carbon is different so i am more apt to let it be. i'll try and post a pic of the damage at some point thank you

be that as it may i try and baby this bike and the trek 5600 post office bike in my avatar is my training bike and has some paint scratches but nothing significant like the magnet damage as far as i can see
 

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Frog Whisperer
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if the magnet was installed properly it would not have hit the frame. So my advice is, get it checked out and repaired if necessary, I can't see how it was the computer's fault.
 

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All I wanted was a Pepsi!
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How did the magnet get that close to the stay? I have a sensor mounted on the crank arm on all of my bikes and they're not even close. If I bump the sensor hard enough the magnet may hit the sensor, but never the stay. I think you've got your sensor mounted wrong.

As to your question, I would have someone look at it before riding it further. If it's repairable, repair it. I wouldn't personally mess around with crazy glue or whatever, but I'm no expert in composite repair. YMMV.
 

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I've seen a fair number of chainstay and BB failures - not just head tubes. Depending on the extent of the damage, your frame may be unsafe to continue riding.

Carbon fiber is fine for planes because planes don't get used around crank arm magnets, rocks and sticks. The leading edges of carbon aircraft are usually not carbon. AND, if you ding a 20 foot wing it is more repairable than a 3/4" chainstay.

Carbon bicycles take advantage of carbon's structural strengths, but have little to no protection against mechanical damage, as the OP discovered.

Super glue isn't going to do anything - it is neither structurally strong nor particularly absorbant. If you want to half-ass a CF repair at home use sandpaper, epoxy and fiberglass cloth. Calfee does CF frame repairs that they'll stand by, but Giant may not want anything to do with this bike.
 

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Discussion Starter · #7 ·


Magnet was inside end of pedal came out while I was riding. My other bike is strapped on arm of crank and some tomes slides up the old school shimano 600. The magnet came out of a campy record crank
 

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That looks deep. I'd have it repaired. Or don't - up to you.

That magnet must have been pretty sharp to carve up the plastic sender, too.
 

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I don't know if it's that critical. I've dropped a chain before on a carbon frame and did similar damage but on a wider area. Some might argue that the bb area is not the same as the chain stay and that the stresses are different - maybe so.
However I believe that the final lay up of carbon is more aesthetic than structural and that gouge doesn't look too deep. But if your concerned about it send the picture to Calfee and see what they say.
 

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I have a Alpha Q GS-10 fork and I ride 25mm tires. I have noticed the underside of the fork had scraps from rocks/debris sticking to the tire and damaging the underside of the fork due to the close clearances. I figure as long as the carbon fibers are not damaged, I just use automotive clearcoat ( 3-4 dollar at auto store) to add additional layers for protection. Not sure if I would use superglue, as I wouldn't know how it would react to the carbon. Clearcoat is basically a paint and is what is used to protect the fork in the first place.
 

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Discussion Starter · #12 ·
PSC said:
I have a Alpha Q GS-10 fork and I ride 25mm tires. I have noticed the underside of the fork had scraps from rocks/debris sticking to the tire and damaging the underside of the fork due to the close clearances. I figure as long as the carbon fibers are not damaged, I just use automotive clearcoat ( 3-4 dollar at auto store) to add additional layers for protection. Not sure if I would use superglue, as I wouldn't know how it would react to the carbon. Clearcoat is basically a paint and is what is used to protect the fork in the first place.
it happened so fast but i think the magnet had a scew at the end. i think some how while i was pedalling the screw part flipped around and scraped the frame. at first i thought it was just hitting the cadence sensor. i'm definately get the frame looked at before I ride it again:


this might be all i need?

 

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After you get the frame repaired and if your pedals have steel spindles, you may want to try using a rare earth magnet attached to the NDS pedal spindle instead of the factory magnet that came with your computer. These magnets are very strong and no problem in sending the signal to the sensor. However, you need to be sure that the cadence sensor can be a little further back on the chainstay and still have the signal picked up by the head unit. I use this setup on all my bikes and it works great. You can find these magnets at most hardware stores and they usually cost less than $5 for a package of 4-5.
 

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Discussion Starter · #14 ·
cdhbrad said:
After you get the frame repaired and if your pedals have steel spindles, you may want to try using a rare earth magnet attached to the NDS pedal spindle instead of the factory magnet that came with your computer. These magnets are very strong and no problem in sending the signal to the sensor. However, you need to be sure that the cadence sensor can be a little further back on the chainstay and still have the signal picked up by the head unit. I use this setup on all my bikes and it works great. You can find these magnets at most hardware stores and they usually cost less than $5 for a package of 4-5.
thanks, but from here forward I am taking the cadence sensor, magnet and ram mount off my giant tcr advanced.

it's been some time since i used my edge 305 nearly dead and my foreunner 405 wrist strap broke. i been using the droid for road and my delorme for the woods. i will leave the sensor on the old trek 5600, although is not as pretty as the tcr, is imho, a better design frame. on the 5600 the fork inside of head tube tapered and if it busts it will be hard to replace

this is me on my other road bike, the trek 5600 post office edition. you can nearly see the strap holding the madnet on the old school shimano 600 crank, the rest of the bike has ultegra i picked up second hand this year but new dura ace brakes, this is my main training bike that i use most of the time, but some how my 'sunday bike' got damaged last saturday
 

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that doesn't look too deep. generally, the top layer or 2 of 'woven' carbon fibre you see on your frame (in your case, a 3k weave) is not structural, but a protective, cosmetic layer. it looks like you've gone thru the clearcoat, and maybe into that layer. have your shop check it out, but it looks like it isn't too bad. those carbon protective patches you posted will do nothing to "repair" the damage, you don't really need to do anything to that scratch. maybe some clear finger nail polish to cover it. keep an eye on it to make sure no cracks form. i'd check it after every ride.
 

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n00bsauce
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Send that photo to Calfee. They'll give you an opinion and a quote. I had damage on a carbon fiber seat tube from shipping. Sent a pic to Calfee and they got back to me right away. They're opinion was slap some nail polish on it and call it good. They would be happy to repair it for me but didn't think it was necessary. Of course, your damage and mine are different. Different area and type of damage (mine was more of an abrasion and probably not as deep). However, send them the pic and they'll let you know. I'd take several pics from different angles with different lighting and send them all.
 

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Discussion Starter · #17 ·
here's another pic of the area in question



keeping an eye on it is probably best practice since a patch could just hide a worsening crack:thumbsup:
 

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cdhbrad said:
After you get the frame repaired and if your pedals have steel spindles, you may want to try using a rare earth magnet attached to the NDS pedal spindle instead of the factory magnet that came with your computer. These magnets are very strong and no problem in sending the signal to the sensor. However, you need to be sure that the cadence sensor can be a little further back on the chainstay and still have the signal picked up by the head unit. I use this setup on all my bikes and it works great. You can find these magnets at most hardware stores and they usually cost less than $5 for a package of 4-5.
better yet, ditch the cadence sensor altogether- cadence is a useless thing to keep track of...unless you have a powermeter and care about quadrant analysis.
 

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Discussion Starter · #19 ·
dito on ditching the cadence sensor. i like to think about it now and again when i ride if I'm conscious of cadence i'm pretty sure to be in triple digits range. i don't use power meter but maybe some where down the road the garmin 500 can log power but i think you may need a special crank.
 
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