Cracked carbon around BB shell. Salvageable? Can I ride it?

Questions about bike hire abroad and everything light bike related. No off-topic chat please

Moderator: Moderator Team

User avatar
Devon
Posts: 775
Joined: Fri Apr 12, 2013 1:19 pm
Location: Oxford, England

by Devon

So today I noticed a rather nasty crack around my BB shell. I think it may have been there for some time undetected. I raced on it today with no issues (bar a few creaks) and have two races booked next weekend. I'm desperate not to miss them and won't be able to sort out a replacement frame in time. Am I safe to ride it? Also is something like this legitimately fixable, or is it just a case of bodging as a temporary measure?

Image
Image
Campagnolo; because it's a bicycle, not a fishing rod.

KH
Posts: 206
Joined: Fri Feb 27, 2004 3:56 pm

by KH

I had something very similar with my Cannondale Supersix. In all probability it had been there a while and was raced/ridden for quite a while before it properly broke (it was an eBay purchase so no chance of a refund). The carbon repair specialist I took it to had a good look and declared it unfixable. It is still sitting in my shed...

The most annoying thing was that the weekend before it properly broke I finished a close 2nd in a road race not realising I was riding a cracked frame...

User avatar
bikerjulio
Posts: 1901
Joined: Fri Dec 11, 2009 10:38 pm
Location: Welland, Ontario

by bikerjulio

It's a high stress area where the alloy BB insert bonds into the frame.

When it breaks, you'll probably experience a wobbly crank. So, I don't see a failure as life threatening but could be noticeable.
There's sometimes a buggy.
How many drivers does a buggy have?

One.

So let's just say I'm drivin' this buggy...
and if you fix your attitude you can ride along with me.

http://www.youtube.com/watch?v=GekiIMh4ZkM

User avatar
Devon
Posts: 775
Joined: Fri Apr 12, 2013 1:19 pm
Location: Oxford, England

by Devon

I'm pretty ready to call it a day with this frame so have no issue running it into the ground while a replacement arrives (BMC is calling me...) As long as it lasts me until this then I don't mind too much; providing failure doesn't risk crank touching tarmac and testicles touching top tube...
Campagnolo; because it's a bicycle, not a fishing rod.

BikeAnon
Posts: 399
Joined: Sun Mar 02, 2014 6:36 pm
Location: NY USA

by BikeAnon

I'm not an expert on this, and don't know if it would work....

Since the frame is destined for the scrap-bin, if you MUST ride it in the meantime... I'd try:

- Sand the CF all along the crack area
- Use a two-part epoxy, force the epoxy into the crack as best you can.

The sanding was to give the excess epoxy something to grab.

Work FAST with the epoxy. It heats as you mix it, the hotter it is, the easier it will be to flow it deeper into the crack.

Butcher
Shop Owner
Posts: 838
Joined: Sun Jan 03, 2010 4:58 am

by Butcher

If you had to use epoxy, try putting the frame in a vacuum [inside the tubes] then apply the epoxy. It will for certain, suck into the crack. Still, I would not think it would last long. Check to find out though.

User avatar
bikerjulio
Posts: 1901
Joined: Fri Dec 11, 2009 10:38 pm
Location: Welland, Ontario

by bikerjulio

I had a similar situation.

Buy this epoxy.

Image

Drill small holes at about 1/4" increments around the crack. just through the carbon - not the alloy sleeve.

Pump in the epoxy.
There's sometimes a buggy.
How many drivers does a buggy have?

One.

So let's just say I'm drivin' this buggy...
and if you fix your attitude you can ride along with me.

http://www.youtube.com/watch?v=GekiIMh4ZkM

User avatar
Devon
Posts: 775
Joined: Fri Apr 12, 2013 1:19 pm
Location: Oxford, England

by Devon

Epoxy was the plan; I have a friend with GRP experience who's offered to patch it for me. Would it be wise to add some external fibreglass sheets too? I'm not bothered about how it looks, besides, battle scars are cool 8)
Campagnolo; because it's a bicycle, not a fishing rod.

Butcher
Shop Owner
Posts: 838
Joined: Sun Jan 03, 2010 4:58 am

by Butcher

The problem is on the inside. Adding material to the outside would do nothing but add 'battle scars'. Suck the epoxy on the inside and put the battle scar material on the outside and you will have exactly what you are looking for.

Start shopping for a frame too.

User avatar
Devon
Posts: 775
Joined: Fri Apr 12, 2013 1:19 pm
Location: Oxford, England

by Devon

By putting material on the outside would it not aid in preventing the crack from pulling out further?
Campagnolo; because it's a bicycle, not a fishing rod.

User avatar
bikerjulio
Posts: 1901
Joined: Fri Dec 11, 2009 10:38 pm
Location: Welland, Ontario

by bikerjulio

If you get enough epoxy on the inside, between the alloy insert and the carbon shell, all the way around, then some will bear against the uncracked inner side too, and help support the insert. It will be a lot more effective than a patch on the outside.

Regardless, it's toast.
There's sometimes a buggy.
How many drivers does a buggy have?

One.

So let's just say I'm drivin' this buggy...
and if you fix your attitude you can ride along with me.

http://www.youtube.com/watch?v=GekiIMh4ZkM

User avatar
Devon
Posts: 775
Joined: Fri Apr 12, 2013 1:19 pm
Location: Oxford, England

by Devon

Oh, I meant do both! Use a GRP patch on the outside to help support the epoxy in the centre. Literally just want it to last the weekend. Am ordering a new frame today/tomorrow...
Campagnolo; because it's a bicycle, not a fishing rod.

Monkeyboy3333
Posts: 632
Joined: Tue Apr 05, 2011 7:41 pm

by Monkeyboy3333

if it fails in the race and you take down a load of people as result, you ain't gonna be popular. Why risk an injury to you or others?

User avatar
euan
Posts: 1494
Joined: Sat Sep 05, 2009 11:20 am

by euan

Yeah thats my view point as well.
"Step forward the climber and all those who worship at the altar of lightness" - R. Millar

Butcher
Shop Owner
Posts: 838
Joined: Sun Jan 03, 2010 4:58 am

by Butcher

If you race like I do, it won't be a problem. It's lonely at the rear.

Post Reply
  • Similar Topics
    Replies
    Views
    Last post