Why carbon frame damage needn't mean the scrapheap for your bike
Why carbon frame damage needn't mean the scrapheap for your bike
Inside Australian composites repair facility Paint My Bike
We recently visited Paint My Bike, a carbon repair and painting specialist, to learn more about how carbon repairs are done. Flick through the gallery to see what we learned
We recently visited Paint My Bike, a carbon repair and painting specialist, to learn more about how carbon repairs are done. Flick through the gallery to see what we learned - Colin Levitch / Immediate Media
A cracked frame doesn't necessarily mean it needs to be replaced – quite a lot of damage can fixed - Colin Levitch / Immediate Media
First the paint is sanded back to determine the extent of the damage - Colin Levitch / Immediate Media
With the paint removed we can see the size of the crack - Colin Levitch / Immediate Media
The repairers at Paint My Bike like to use 'pre-preg' carbon fiber sheets. Pre-preg means the carbon matrix is already 'pre-impregnated' with the correct amount of epoxy resin - Colin Levitch / Immediate Media
The first layer of the repaired layup is twill weave carbon which is used to strengthen the area - Colin Levitch / Immediate Media
To insure the repair is strong another layer of twill forms the next layer of the layup - Colin Levitch / Immediate Media
Finally the repair is finished with unidirectional carbon in an attempt to match the the original layup - Colin Levitch / Immediate Media
Pre preg carbon needs to be refrigerated as even at room temperature the resin begins to cure - Colin Levitch / Immediate Media
While the team at Paint My Bike prefers to use pre-preg carbon, if need be they can do it the old fashioned way - Colin Levitch / Immediate Media
In an effort to make their repairs completely invisible Paint My Bike will even make moulds that will match dimpling and other patterns on frames and wheels - Colin Levitch / Immediate Media
For larger tube section repairs, they'll fabricate moulds to match tube shapes - Colin Levitch / Immediate Media
Here's the repair from the mould we just showed you - Colin Levitch / Immediate Media
This Madone came in with damage from a roof rack. Although there was damage on both sides, it did not require a full section of the tubing to be removed - Colin Levitch / Immediate Media
Here you can see the repair in progress from the inside, but also the joint where the frame sections were bonded together during manufacturing - Colin Levitch / Immediate Media
For a repair like this one, Paint My Bike fabricates custom air bladders to support the inside wall of the repair and squeeze out any extra resin - Colin Levitch / Immediate Media
The carbon curing oven is even equipped with a compressor, which is attached to the bladders to keep them inflated through the curing process - Colin Levitch / Immediate Media
There's a few additional tricks of the trade Paint My Bike does from here, which we can’t show you - Colin Levitch / Immediate Media
With the repair fully prepped the bike is put into a large oven so the resin can cure - Colin Levitch / Immediate Media
It's hard to see but this is a resin curing schedule. It's possible to crank the oven up and cure a repair in an hour, but it may ruin the paintwork and decals on the bike. Paint My Bike usually opts to bake repairs overnight - Colin Levitch / Immediate Media
We spotted a few hidden gems around the Paint My Bike workshop - Colin Levitch / Immediate Media
Some carbon repair outfits don't like to do paint and will only apply a clear coat to protect the resin from UV degradation - Colin Levitch / Immediate Media
One of the more common repairs that comes in are chewed up dropouts - Colin Levitch / Immediate Media
So Paint My Bike had the machine shop next door make up some alloy dropout protectors - Colin Levitch / Immediate Media
There's a fair few discarded 'franken frames', which Paint My Bike will borrow hard to mould sections of tubing and test paint colours - Colin Levitch / Immediate Media
For repairs where a section of tubing is removed, Paint My Bike uses a frame building jig to ensure there are no changes in geometry - Colin Levitch / Immediate Media
The shop also gets a lot of crushed steerer tubes in for repair. As a standard repair would be extremely difficult, Paint My Bike had the engineering shop next door machine these alloy supports, which are bonded into the top of the steerer where the stem clamps the tube - Colin Levitch / Immediate Media
This frame came in for a Di2 conversion. If you look really close you can see where Paint My Bike knocked off the cable guides - Colin Levitch / Immediate Media
With the Cannondale we saw earlier set aside because it needed hours in the oven to cure, we headed over to the spray booth to see some frames being finished - Colin Levitch / Immediate Media
This is what the repaired section of carbon looks like fresh out of the curing oven - Colin Levitch / Immediate Media
Before the bikes are painted they're sanded and then masked - Colin Levitch / Immediate Media
Instead of masking tough areas like bottom brackets and dropouts, custom-cut vinyl dots are used - Colin Levitch / Immediate Media
Looks like there's a The Walking Dead fan at Paint My Bike who's pretty good with an airbrush - Colin Levitch / Immediate Media
Paint My Bike uses ceramicclear coats to finish off all its jobs, which need to be applied in a clean environment and then baked off. The team also do touchups on cars occasionally - Colin Levitch / Immediate Media
First a clear sealer is applied to the repair - Colin Levitch / Immediate Media
Then the bike goes back in the oven to cure the sealer - Colin Levitch / Immediate Media
When Paint My Bike told us it could match any paint colour we were dubious – then they showed us their paint mixing room - Colin Levitch / Immediate Media
While the sealer is curing, vinyl decals are printed, which will be used when painting logos on the frame - Colin Levitch / Immediate Media
All the decals are printed in-house, and they’ve got pretty much every logo and font on file - Colin Levitch / Immediate Media
Somebody wanted Mighty Mouse on their bike - Colin Levitch / Immediate Media
The team always print a couple of extra logo decals just incase one gets put on crooked - Colin Levitch / Immediate Media
While we were waiting for the paint cure we went to the bike graveyard – 10 points if you can guess what this frame use to be - Colin Levitch / Immediate Media
When frames come in the damage can be assessed under an electronic microscope - Colin Levitch / Immediate Media
Here you can see the trouble spot - Colin Levitch / Immediate Media
The Focus is out of the curing oven and ready for its next coat of paint - Colin Levitch / Immediate Media
Remember those vinyl dots? - Colin Levitch / Immediate Media
To perfectly match the other seatstay, two different black plaints are applied - Colin Levitch / Immediate Media
Next the logo decal is applied - Colin Levitch / Immediate Media
And then airbrushed - Colin Levitch / Immediate Media
Unfortunately the logo that Paint My Bike had on file hadn’t been updated in awhile and didn’t match the one on the other side, so it needed to be repainted - Colin Levitch / Immediate Media
The aerospace approved tool for determining if the carbon components on a airplane are damaged. They work pretty well on bikes too - Colin Levitch / Immediate Media
Carbon fibre is a bit of a wonder material in the cycling world. It’s lightweight, and depending on the layup can be tuned to be stiff on one axis, and noodly on another. It can also be moulded into radical shapes to cheat the wind.
Unfortunately for such a cycling industry mainstay, the high-modulus carbon used in bike frames and components is quite brittle, despite its high tensile strength. Designed to handle forces on a certain axis, a sharp impact from a different direction, say from a crash, has the potential to cause serious damage.
Take a look through any secondhand bike site and you’ll find pages of late model carbon frames with cracks, broken seatstays, and crushed carbon parts. Fortunately though, if you’ve got a broken bike all may not be lost – because quite a lot of damaged carbon fibre can be repaired.
Here you can see the repair in progress from the inside, but also the joint when the frame sections were bonded together during manufacturing:
You can see the spot where this frame was bonded together at the factory. You can also see the extra filler material used in the joint
Keen to find out more, we were pleased when Australian repair shop Paint My Bike invited BikeRadar behind the scenes to see how its team breath life back into beaten and battered rides.
"When you think about it, most frames are moulded in pieces and then bonded together. We do essentially the same thing when we're repairing a frame," explains Gary McDonald from Australian repair shop Paint My Bike.
"You’d be surprised how many integrated seatposts cut too short we get from bike shops. We’ve even had quite a few frames come in for repair, and as we sand the paint off we find repairs that look like they’ve been done before the bike ever left the factory."
Fixing a carbon frame is, in fact, considerably easier and more effective than trying to mend a broken alloy one, and the repair will be as strong or stronger than the surrounding material. Yes, there is a slight weight gain, but we’re talking less than the difference between an aluminium and titanium bottle cage bolt.
Even better, composite repair specialists that fix up your injured steed can also seamlessly match paintwork and decals, leaving even the most scrutinising eyes none the wiser.
Seamless repairs
Housed in a rather industrial looking area, and hidden inside an unassuming blue building, Paint My Bike has a fully outfitted composite repair facility as well as – likeits name suggests – a high-end spray booth.
"Every repair we do, we want to be seamless both in paint but also in tube shape and thickness," McDonald tells BikeRadar. "Not only do we want to avoid that big black ball of carbon at the repair site because it’s ugly, but the mass of material creates a weak point on either side of the repair."
There isn’t a whole lot on a bike that cannot be repaired, and a quick look around the workshop reveals everything from classic frames from the early days of carbon fibre, to bikes that couldn’t be more than a week old. Damage ranges from crushed steerer tubes to broken forks and sheared seatstays. Plenty of bikes have sustained damage from roof racks.
With the paint removed we can see the size of the crack:
Your broken frame can probably be fixed
For each repair as the paint is sanded back to determine the extent of the damage, the layup is also visually assessed and will be matched where possible. That said, concessions in creating an identical layup will be made to ensure a strong repair, and McDonald explained that cross woven twill carbon is sometimes used in place of unidirectional, "so there are fibres in more directions with less layers"
As the layup plays a major factor in the ride quality of a carbon frame, you’d think removing or replacing a piece would make a noticeable difference. Paint My Bike worked extensively with now defunct Aussie pro team Budget Forklifts, fixing all manner of damage on team bikes, and McDonald and crew would quiz the riders to see if they could pick up any difference.
“Not a single rider could feel a difference in ride quality, even after sizable repairs,” McDonald says.
Your bike isn’t a plane
When you research carbon repair, often you’ll find outfits using ultrasound machines for ‘ultimate accuracy’ in diagnosing the extent of the damage to your frame. This method is used in the aerospace industry, when the failure of a few fibres could mean the deaths of hundreds of people. There’s a few repairers use this method, and even Canyon says it puts bikes through a scanner when they come back for warranties, but according to McDonald that’s not necessarily the best method for determining the damage to carbon bikes.
"With ultrasound it's very difficult to pick up cracks – it mostly finds voids and delamination. From our experience it also can’t tell the difference between filler and a void,” he says. “Almost every bike manufacturer uses filler between joins and over imperfections in the frame, and these show up as voids on ultrasound. Many brand new frames will fail an ultrasound test, a bike is not a plane and they are not manufactured to the same standards."
The aerospace approved tool for determining if the carbon components a plane is damaged. they work pretty well on bikes too:
This is the aerospace approved tool for finding damage to carbon fibre
“The aerospace approved method for finding damage to carbon fibre is an acoustic tap hammer. If you go down to the airport right now you’ll find engineers tapping around looking for damage.” McDonald says.
If we learned one thing from the day, it’s that there’s no sense crying over frayed fibres and cracked tubing – find out how to get them fixed. Check out the mega gallery above to find out more about carbon repair.
*This is not a ‘How to’ article, nor is it comprehensive in the techniques used as each repairer has their own method, and there were a few things that the staff at Paint My Bike wanted to keep under wraps.