[Closed] Cracked Chinese carbon 29er frame (sob / what to do thread)

If no warranty, then I’d get another 29er frame to try.

Worth looking at the German sites for Cube frames on the cheap as they sometimes sell them ridiculously cheap.

Other than that I’d look for an aluminium frame personally - something like a Nukeproof scout 290 appeals - someone I know has one and it looks a lot of fun.

I'd sand it down and look to see how bad it was then decide to fix it. (though I have the stuff to do that already). Can you fix it locally? It really doesn't need much materials to fix.

I have bought a cheep planet x carbon frame that broke at the seat clamp from not enough seat post inserted. I ended up wrapping the whole clamp area an having the seat clamp face the other way.

Have you the funds to have a go your self regardless? The frames broke anyway so you wont make it worse and as said earlier you don't need much cloth (I bet postage will be biggest cost

I wouldnt say that was due to seat post. The post was way past the top tube junction.

I suspect there is a joint around that area in that area as they will layup the frame in sections and then splice them together. Very easy to have messed it up.

Should be easy enough to do a DIY fix but what else is wrong on the frame that you can't see? If you had been riding it for a while and then something broke I would be happier fixing it but first ride sets of alarm bells I am afraid.

That said you could just be unlucky in this one location. The repair needs to be sanded back for quite a way either side and then multiple layers of carbon at different orientations applied with lengths staggered to reduce the stress concentration of each ply drop off. There should be some good guides out there and with a few layers it should be pretty strong and not affect the feel of the frame that close to a junction. It will need compressing down with some shrink tape to push out all the air.

@joebristol - thanks, I checked bikediscount and they only have big and small frames at silly discounts.  Will keep an eye out though.

@bigdean - I hadn't considered DIY repair but have nothing to lose if no warranty.  Could be interesting to learn about.  Any kit you'd recommend?  I can see kits with epoxy and fibre material from £10-£25.  Do you reckon a "small" kit like below would be enough?

1,One piece of A4 Size (approx) carbon fibre fabric cloth (12k 300g Unidirectional Carbon Fibre Fabric, 198x300mm approx.)
2, 16g epoxy resin and 4.8g hardener
3, One pair of gloves
4, A roll of PVC tape
5, One user instruction of epoxy resin
6, Two piece of sand papers

Thanks.

Bear in mind that the cube frames often come up small, so you could size up and use an on trend super short stem

@andyl - Yes I was clutching at straws with the seat post theory as I like there to be a "reason" for things!

Thanks for adding the detail / encouragement on DIY repair.  Agreed that I don't know what else is wrong with the frame but if a £10 epoxy / fibre material kit would be sufficient I'd consider it a cheap evening's entertainment to have a go (even if I bin the frame afterwards).

4) Alloy frame from trusted brand for now.

This.

Something like the starter kit in the link

http://www.easycomposites.co.uk/#!/starter-kits/carbon-fibre-laminating-starter-kit.html

I would sand down to carbon (take the paint off a good 2-3" either side of the crack).

Sand the crack all the way around, ideally stopthe crack going further by sand a v along it untill you reach undamaged carbon tube.

Clean and mask off parts of the frame you dont want resin on, bin liner and selotape for this.

Cut the cloth to give multiple layers save the long strands that fall out the cloth to use as wraps.

Mix resin and initally brush some on the frame

Place the cloth over the crack and stipple the cloth with resin and make sure its fully wetted out

Repeat for subsequent layers (alternated fiber direction if you can but i wouldn't worry if you dont

Use the carbon strand saved earlier to tie the cloth around the frame untill you can compct it

Cover with release coth (you can avoid this step)

To compact the fiber and reduce the resin content you can wrap shrink tape around the tube and uuse a heat gun to shrink it using a pin to add some hole for excess resin to escape from, an alternative is to use selotape sticky side out and just wrap as tightly as you can. Try to avoid folds and voids, i tend to lay and wrap fiber all in the same direction.

Admire the mess you have made

Have a beer while it dries (leave it a day)

Unwrap all the tape then leave another day to fully cure

Sand to desired finish and cover resin again to seal

Paint

It wont be pretty but should be more than strong enough if done right.

Not meaning to be overly direct, but throw it in the bin and buy something that's been subjected to some kind of testing and regulation that won't just let go randomly.

There's absolutely no point in even trying to roll that turd in glitter.

As above its broken on its first ride. I wouldn't be bothering fixing that, what about when the head tube fails next? 

The important thing is that you have not been injured.

This frame was brand new, having never been built up nor ridden, the only thing done to it was fitting the bottom bracket, I may have photos of the BB showing the totally clean threads prior to fitting.

Minimum seatpost insertion is usually 100 mm so I do not believe that is the cause.

I sold this frame is because I found a ktm myroon 29 frame and built that up.

I have never sold nor would ever sell damaged goods. I don't believe this damage was already present.

Like it or not, the clue may be *cheap Chinese unbranded carbon*, frames like this sell for £200, for comparison my ktm frame cost £1500, there has to be a reason for that.

When I was looking at buying this frame, I read that many of these have been bought and ridden without problems and I honestly think you have been unlucky.

As I already responded, I will help you out as much as I can to see if I can find out the seller but from memory, I cannot remember what was the warranty period, if any.

The frame can be repaired but I personally would not trust it.

a clock mechanism in the bb a couple of spokes to use as hands and you have a bike themed clock for the man cave

a clock mechanism in the bb a couple of spokes to use as hands and you have a bike themed clock for the man cave

Chinese carbon spokes?

IF you do the repair you want to stagger the lengths like a scarf joint:

The ugliest way to do it is first layer longest and then get shorter and shorter but the neater way is to do the first layer shortest and then get longer and longer with each layer sealing down onto the frame.

A proper scarf joint involved machining away each layer of material in a staggered pattern and then inserting a staggered patch but this is not what you want to be attempting for this, it's what we would do on say a fuselage section.

The number of layers you want depends on the thickness/weight (gsm) of the fabric but most top tubes are pretty thin. the woven fabric you will get is essentially 0/90 fibres so ideally you want to alternate 0/90 and then +/-45 orientation. The 45's will help the joint take any torsion loading, probably more critical in a BB area due to pedalling loads but you still want to get some 45's.

May as well have fun and try it. Just wear some body armour and a full face when you next ride it 😉

actually, what could be even more fun is give it to someone who could cut it up and take a look inside for more poor manufacturing. I could see if there is any interest in work for using it as a learning tool for some of the graduates. We dont normally get stuff like this to cut up.

@bigdean - thanks for the detailed reply (which makes it sound easy).  I will probably have a bash but only as a curiosity.

@02gf74 - thanks for your reply here (hadn't realised you're on STW) and to my email.  I am sorry my post hints you may have known about any damage or that you weren't co-operative regarding investigating warranty and want to emphasise here that wasn't the case .  Also you gave me plenty of opportunity to look at the frame and clearly it had not been built up.

I of course agree with your all your points and I think we even joked about it when I picked up the frame.  I certainly had doubts in my mind!

@andyl - thanks for layering tips and I will let you know if I'm binning it!

Just go build the Mount Vision up and ride.

Steel 29er! Old Skool 👍🏼

What size frame are you after? Bikediscount.de have 16” and 18” 29er frames for under €150

Sanded it down.  Not bothering trying to repair for now.  Will rebuild old bike.

@funkmasterp - I want something light and vaguely race (fun/mtb marathon) oriented.

@NorthCountryBoy - looking at 18"-19" (~say 610 tt).

Update: I had a bash at repair.  Copy-pasted report below (after using htmltidy.net because the STW forum software is completely useless at dealing with formatted content).

I bought a kit containing the essentials including carbon fibre material, epoxy (resign and hardener), shrink wrap with release coating from eBay.

The main time consuming part was frame preparation. I started by sanding the area around the crack by hand. After I revealed more of the crack it seemed the frame had cracked along a bonded joint because the fissure was basically straight across.

Sanding by hand got boring quickly so I used a sanding attachment on an electric drill and finished the trickier parts around the seat post by hand. I did it outside and used my Respro cycling pollution mask as a lot more dust was generated.

The accepted wisdom seemed to be completely remove the damaged part round the crack. It was much bigger than I expected. It seemed the area didn't have enough epoxy generally as the broken part was quite flakey.

I used polystyrene to fill the gap so the original shape of the tube would be retained . I must admit it took two attempts to get something I was willing to proceed with.

Then I made a template for cutting out the carbon fibre material (actually to be honest I started this after the first polystyrene filler thing that I discarded, then I made a better template).

Then I made my first bad mistake- I jumped straight to mixing the epoxy rather than preparing all the pieces of carbon. As soon as the hardener and resin are mixed you are against the clock. The carbon took longer to cut than I imagined. The strands at the edges came loose. After the first layer I was convinced this project was a stupid waste of time and money. I compacted the layers down with plastering gauze tape, which also kept the edges of the carbon material from lifting. I alternated layers at 0 and +\- 30 degrees (approximately). By the third layer I felt more confident. By the fifth (final) layer I thought maybe building my own carbon frame would be a fun project!

I took no photos of the layering because I was wearing epoxy-covered nitrile gloves (came in the kit) and felt under time pressure.

After layering I wound the shrink wrap tape with what I hoped was the release-agent coated side against the fibre (another mistake- should have checked beforehand). I poked lots of little holes in the tape to set the excess epoxy escape.

At this point I was feeling pleased with progress and granted myself the pleasure of admiring the mess I'd made.

I had a quick tidy and moved back into the shed. It was time for a another big mistake. I didn't check what temperature to use with the shrink wrap tape. The lowest temperature on the heat gun (50) didn't seem to do much so I just whacked it up to 400. The tape quickly contracted and glue oozed out as expected. However, parts of the tape just melted away to nothing before I realised what was happening. Also one part of the polystyrene got compressed down so there is now a narrow part in the tube. More worryingly the epoxy curing process may have been compromised by the heat (parts already seemed rigid after the heat gun treatment).

After a day (~demould time) I peeled off what tape I could and then sanded off the melted parts. The surface is more uneven than I hoped for (especially where the polystyrene got squashed) but overall it looks reasonable as far as ghetto repairs go.

I waited patiently for the rest of the day pondering whether to spray the frame luminous green or orange while it was completely stripped. Then, suddenly I couldn't wait to rebuild. I figured gently bolting on a few components wouldn't stress the repair. This was a silly thing to do, not least because there was then overwhelming temptation to take it for a quick spin, which I later did! So there are now two potential flaws in the curing- application of excessive heat and premature stress. I henceforth will refer to the bike as DeathTrap.

Thats great, 5 layers should be strong enough. I'd just cover the bare carbon with either lacker or a layer of epoxy just to seal it.

You do get through nitrile gloves though..

Ps not been able to get to the garage to send that stuff. If you still want some let me know.

Go buy a full face helmet please and make sure to report back, god willing, after ride no1

@bigdean cheers!

Don't worry about sending thanks.

I think 5 layers is ok too (no obvious flex or anything when I went for a quick ride) but I still have enough carbon and epoxy for another 3 layers, which I'm tempted to do.

I am planning to use Autotek Clear Lacquer.  It claims to have UV protection (otherwise I don't really know if it's suitable)

Crikey! Rather you than me.

If I felt as lucky as you clearly do, I'd buy a lottery ticket.

Bonkers!

Nice write up, made me chuckle. Good luck.

Don't paint it, leave it as it is with a clear coat, that way it's easier to check for damage.

I want pictures! 😁

@damascus thanks!  I was mostly doing it for fun and learning so glad to share 🙂  Agreed regarding clear coat.

@Poopscoop not sure what happened to the photos but they're at https://peter.windridge.org.uk/home/carbon-bicycle-frame-repair

All other warnings have been duly noted, thanks, I will surely remember them when I'm lying in hospital 🙂

**** that. Throw it in the bin.

Hmm, don't think i'd risk riding that it was mine.

I thought it was a crack, not been eating by rats!

Maybe keep this on the road and avoid kerbs

Probably stronger now than it was before the crack.

Sadly i can't see the pics at work, but cracking write up...

I wouldn't ride it either.... esepcially after reading your write up.... but it's still cool.

You should start a go-fund-me page so we can all throw in a Fiver so you don't end up wearing your stem and bars as face furniture 🙂

Probably stronger now than it was before the crack.

MAybe in that area... but there's another 300 areas of weakness and shit manufacturing 🙂

An update.

Credit card company aren't interested as it was a PayPal transaction.

PayPal say open ebay dispute.

Ebay, too much time has passed to open dispute plus I can't find it in purchase history.

I did find payment transaction and sent email to seller. 2 weeks and no response.

Ill throw a few quid your way as potentially the frame could (would) have failed when I was riding it so a lucky escape

As I mentioned before, its not worth the risk.  We know the design and material are sound, but in this instance, lack of quality control.

Quick update:

First kudos to @02gf74 who generously insisted on refunding some money, which covered the repair materials.

I coated the repair with Autotek Professional Clear Lacquer (with UV protection).

Frame weight with the final repair is still <1.1kg.

I noted the warnings here but have done 250km of ~easy trail, bridleway etc for research purposes 🙂

No probs with anything else on the frame (yet!).  Still need to do the internal routing for rear brake (but this is because I can't be bothered to bleed the brake rather than a problem with the frame insides).  The XC421 rims I built have been great.

Overall I'm pleased with 29er hardail experiment for winter now even if I bin this particular frame. It's definitely quicker on climbs compared to my old 26" full sus (at least the non-technical ones within riding distance from London).  Surprisingly on flat-ish trails it feels only marginally quicker.  The front end with tapered steerer and 15mm axle feels sturdier than straight/qr despite the bigger wheels.  The biggest advantage I'm hoping for is mid-rear mud-handling but I haven't tested this much yet.

@ChunkyMTB @weeksy - the repaired part certainly feels chunkier than the rest of the TT!

To 02gf74:

I somehow did a claim through paypal after the time limit (90 days I think?) on ebay had expired. Bought a brand new telephone, had it about 4 months then it just refused to switch on. Contacted seller who told me to jog on, put a claim in through paypal, took about a fortnight and some form filling but the funds came back. Can't remember how I did it but I do remember it took a bit of finding, it's in there somewhere. This was a UK based business seller though if that makes any difference.

PS - Good effort Twowheels, top bodging.

Cool repair but I wouldn't ride that.

Carbon isn't like steel. If it goes it will just go. U might end up face planting the dirt at 30 mph.

Good job that man and good write-up. 👍

Did exactly the same thing with my smashed seat stay on my Cube. It's done hundreds of abusive miles of proper off road and racing since then and hasn't missed a beat or shown any signs of failing. Good work!

If anyone has any broken composite frames that they want relieved of for some beer money / fair price, I'll happily take them as they're useful for my little experiments / projects. Let me know (DM), cheers.

"Carbon isn’t like steel."

your right - im more likely to ride an amateurly repaired carbon frame than i am with someones home mig repaired steel frame.....