Carbon frames - easily damaged?

[Lambchop]

Hi,

I have just purchased my first carbon framed road bike (a 2010 Bianchi Infinito Ultegra). On reading the manual it mentions using a torque wrench to tighten the seat post, brake mounting points and other bolt on bits.

Its something i've never even considered using on my alloy framed bikes, is it really that critical? I will obviously be very cautious not to overtighten.. just curious as to what other carbon framed riders did?

BTW I am over the moon with my new Bianchi - the ride is sublime! The only area I think could be improved are the wheels -Fulcrum racing 7's.

Thanks for any advice.

 

[TheDoctor]

I didn't use a torque wrench, but I've built a fair few bikes and I'm confident of the difference between too loose and crunched!
It's certainly more critical with carbon, but it's not rocket science...

 

[andyhunter]

i have a full carbon mtb bike a trek 9.8 with easton carbon bars, steam, seatpost, rock shock sid world cup forks, and it is extremly light and strong. any 1 that says carbon fiber aint strong needs to sit down and study, carbon fiber depending on the type used as the cheap stuff sh*t and the dear stuff class and way it is made threw the woving pattern techniques such as horizontal and vertical and diagonal in all different ways at the same time etc is far stronger than metal have never had a problem with anything carbon, not even bent a carbon hanger bracket but i have bent a magnesium hanger braket though and i treated my bike like it was a dh bike in certain technical areas of mtb racing. i have came off my bike few times threw mistakes, only thing i have broken on the bike is my saddle thus going over the handle bars which was a very light stelle italia saddle well the rails were in tack jus the seat came off but i still won the race many moons ago. i have a torque wrench to tighten but i dnt bother with one i jus use my instints as i dnt under/over tighten but enough to have it locked into place and then regularly give check to each part/component and tighten up if neccessary at least one a month or else before each race. i have a look 386i road frame which is all carbon but i have other carbon bits on it such as carbon bars, stem, seatpost, pedals, wheels etc etc and its easy to tighten each of them as i find its the same as securing the wheels to your bike you know with feel if too loose or too tight, well i do anyways .

 

[Lambchop]

Cheers Doc, perhaps it's something I'll get the shop to demonstrate to me when it's due first service.

Andy - you may have opened a whole can of worms there with your statement about carbon being stronger than metal -oooooh controversial!

 

[andyhunter]

Cheers Doc, perhaps it's something I'll get the shop to demonstrate to me when it's due first service.

Andy - you may have opened a whole can of worms there with your statement about carbon being stronger than metal -oooooh controversial!

but seriously if it wernt strong and stronger than other materials then most aircrafts wouldnt use them as i have seen in person plans for different bombardiers aircrafts when i was at school doing alevels and it showed how much stress carbon fiber wings and different structures of the plane could take and how much flex they could be pushed to and it was awsome, so if carbon was no good they would stick to metal for the majority of structure and certain components, same applys for other products such as bikes or f1 cars etc . but it really applies to how much your willing to spend and who you choose to get your carbon from such as bike maker as some are better than others from research and development as there all different grades of carbon and ways it can be made for lightness and strength

 

[TheDoctor]

*takes bait*
It's not quite as simple as that.
You can't really say 'carbon is stronger than metal' without qualifying it a little. So much depends on how much carbon, mono- or multi-directional fibers, what metal and how much of it, and so on and so forth. Certainly you won't bend carbon - but you might break it.
As you rightly say, though, it can take an amazing amount of stress and still work perfectly. My carbon frame is *lovely*. But so are my steel ones. And my alloy one.It's all good.
Anyway, we're getting off the topic here. A torque wrench isn't necessary if you're confident you know what you're doing. If you're not sure, using one is probably a good idea, at least till you are sure.

 

[Lambchop]

How about QR wheel skewers? Can they damage the forks/rear drop outs if overtightened?

 

[GrasB]

With carbon fibre basically you have to do things tight enough to grip firmly but not absolutely roger it tight. Same with quick release, iirc the way to tighten the quick release is to get it to gently bite the surface then lock, it's surprising how little force you need to apply to adequately lock a wheel with QR.

 

[TheDoctor]

How about QR wheel skewers? Can they damage the forks/rear drop outs if overtightened?

Most bikes don't have carbon dropouts - they'll be aluminium and bonded (ie glued) in. Making hard points in carbon composite is tricky. Not impossible, but only really worth doing for top-end stuff.