spectastic

i'd like to look at this a little more in depth. the cost of carbon frames is falling. it's a capable material for touring. I'd like to address the advantages and disadvantages of touring on carbon, as well as potential mitigations for the weak points on carbon.. I got my chinese carbon cx frameset from a reputable seller with 2 yr warranty for around 500, which is pretty close to what one would pay for a surly, soma, and the like.

pros:
lightweight (on avg you save maybe 1 kg)
stiffer yet comfortable
costs are coming down, especially if you look at the open mold models from a reputable seller

cons:

1. no eyelets (need p clamps or something for the rack)
2. can't weld it like steel
3. low impact resistance
4. more theft prone
5. generally not designed for touring punishment

now to address the cons..

1. can p clamps provide enough support for a 30-40 lb loaded rack? furthermore, can a typical well built carbon seat stay handle the extra weight at the lower seat stay joints? (the answer varies with the build, so let's just make a sensible assumption that the frame is more a cx frame, and not a tarmac, cervelo, cannondale evo, or any of the race style bikes)
2. how common are frame damage in a given tour? where are the failures most common? (if it's bb, head tube, or dropouts, it's probably game over)
3. carbon fiber frames can be protected. people have used inner tubes, or other polymeric material that disperses the force. are these generally adequate to protect the carbon frame for a long tour?
4. I'm sure there are ways to make a carbon bike look ugly (eg. wrap it in inner tube)
5. I get it, Murphy's Law.. carbon fiber isn't designed to handle forces equally in all directions. but again, assume that it's a well built cx frame, not a superlight giant propel advanced sl... what are some specific touring scenarios where a carbon fiber frame would be at risk?

azza_333

I have built a carbon touring bike https://www.bikeforums.net/touring/10...ike-story.html using the following frame with eyelets AC059 Carbon cyclocross frame disc brake - Shenzhen ICAN Sports Equipment Co., Ltd.
so I am all for carbon touring, I will say this though, if you are planning on taking 30-40lbs of gear on your rear rack, is it worth saving the extra 2lbs over steel.

You should not use P clamps or any other clamps on carbon.

chasm54

But the obvious question is, why? I can see touring on a carbon bike if you were going ultralight - I've toured on a sub-20lb road bike myself. So a carbon bike with a frame bag or modest saddlebag would be fine. But you're talking 30-40lbs of baggage. In that context, saving three or four pounds on the weight of the bike makes little sense. Plus, the chainstays are unlikely to be long enough for you to avoid heelstrike if you have heavily-laden panniers on the back.

Personally I would not use P-clamps to secure a heavily loaded rack to carbon stays. The stays aren't built for it, and there's a reason one uses a torque wrench on carbon fibre - I'd hesitate to guess at how hard to torque the clamps to provide security without damaging the material. Others who are more expert might have different views.

Frame damage is not common on tour, in my experience.

Whar exactly are you trying to protect the bike from by wrapping it in inner tubes or whatever? And if you do that, aren't you negating the weight loss you've gone to all this trouble to protect?

If you want to do loaded touring, the obvious thing to do is use a bike that can readily carry loads.

gerryl

Over the years my bike has suffered a lot. The frame has been dented, the rear stays bent and the front fork pushed in. Every time I've been able to sort fix it enough to get me somewhere where a more permanent fix could be made. I don't think a carbon fibre frame would have served me well in those situations. Having said that if you are planning to ride only on paved roads, have no accidents and not let anyone else handle your bike, a carbon fibre bike would do just fine.
As I get older, slower and more risk averse (aka boring) I could see myself going for lighter bike.

staehpj1

My ideal touring bike would probably be carbon fiber, but I doubt that I would choose it for the usage you propose. I would think of ways to reduce your proposed gear weight long before even considering a CF bike unless maybe you will be pulling a trailer.

1. P clamps on carbon are probably a bad idea. There are other answers including using the brake bridge bolt and skewers. Also canti brake bosses work if you have them. Then there are the various rackless solutions.
2. Probably not a problem until you start carrying too much and/or start using p clamps. BTW, repairs can be done with epoxy and cloth so doing a roadside repair may actually be easier than with a metal frame. I think the notion of repairing frames on tour is kind of a stretch any way, since for short tours the tour is probably over and for a long one getting another whole bike or a frame sent from home may be a more likely option.
3. I wouldn't bother. Just use reasonable care. Their fragility is often overstated.
4. Again I wouldn't bother. Use reasonable care in where you leave the bike and don't worry. If you really must put a few splotches of primer here and there.
5. I really don't think the risk is any big deal. You do want to avoid sharp stress points like p clamps. You also want to take some care to minimize impacts with sharp objects.

The big question is why would you bother to go carbon and then carry 30-40 pounds of stuff? It is pretty easy to camp and cook with 20 pounds of gear. It seems like you would start by leaving a lot of that 30-40 pounds of stuff home before going to CF for the frame.

spectastic

I carry 20 lbs. I put in 30-40 lbs as a conservative range for a much longer tour, where you may have to carry extra food/water.

what about skewer adapters for the racks?

fietsbob

Old man Mountain builds racks around that Idea.

nun

Once you get your luggage so that you have no need for racks at all then every bike becomes a potential touring bike. Look at bikepacking bags, handlebar bags and seat post mounted saddlebags.

Tim_Iowa

You could mount a rack with skewer adapters and a seatpost clamp with mounts. That would be a secure setup and save the carbon from getting crushed in a clamp.

However, your frame may not handle well with that extra weight. The layup of the carbon fibers is very important for the end stiffness of the piece (and that stiffness is very directional). Your frame was not laid up with the stresses of an added load in mind. It could be totally fine, it could be a noodle, or it could crack.

I believe a rackless setup would be better.

I recently bought a carbon cross bike, a '13 Foundry Auger. It actually has fender bosses (never seen that on any carbon bike besides Calfee) but I still wouldn't trust those to support a rack.

I use a Revelate Tangle half-frame bag, a Revelate Sweet Roll handlebar bag with an added pocket, and I can add a big saddlebag for a longer trip.
If I can't carry my load in that setup, I'm carrying too much and should use my steel touring bike with racks and panniers.

I would have grave concerns with overloading your Chinese carbon frame. I understand that you bought it from a seller that gave you a guarantee, but did that guarantee include insurance for you, or just frame replacement? Would you void that guarantee if you add a rack?

I had trepidation buying my first carbon frame, but as it was made in Taiwan by a major manufacturer, I felt more secure than with an open-mold Chinese frame. Big difference, in my mind.

saddlesores

i just don't know where to start............

nun

The new "adventure/gravel" bikes have big tire clearances, slack angles and long chainstays. They look like they will make excellent touring bikes for people that don't need racks, or just go out and get a carbon CX bike. The Raleigh Roker has some nice specs for $2.5k

Raleigh Bicycles - Roker Sport

robow

I have a friend that tours on carbon and uses the Old Man Mountain rack noted above along with the seat post clamp that has the braze ons for attachment. I've also seen him use a seat post attaching rear rack with a rear trunk bag and the mini panniers that fold out and downward. He does quite well with it but he limits his loads significantly and uses it mostly for credit card touring.

staehpj1

I have not found that for me longer tours actually mean more weight carried assuming road tours in first world countries. I pretty much never need to carry more than 24 hours of food or water at a time. I always have clothing and sleeping gear to get me by in subfreezing temps any time I am in the mountains (my standard clothes and sleeping bag were fine when the overnight low dipped into the teens on my ST tour).

I don't count water or food in gear weight because they are variable throughout the day. I typically carry a couple bottles of water at the start of the day. Those occasions where I need to carry a gallon of water are pretty few and far between. When going ultralight, if I do need to carry much extra water it is usually carried in either jersey pockets or a small backpack. That has never been a big hardship since it doesn't happen that often and the load decreases through the day. If you were to tour somewhere that you needed to go several days between water sources the load would go up, but even on the ST I never found that to be the case.

spectastic

so tubus makes these overpriced QR adapters that conveniently has 3 holes in them. https://www.google.com/search?q=tubu...w=1280&bih=620

what if I did something like this

it will distribute the forces a lot better than just p clamp or qr skewer alone... most of the compression is on the skewer. the p clamp on the seat stay serves the primary purpose of keeping the rack in place when you remove the rear wheel. It will experience much less pulling force than the skewer. the only trick is how to get around the disc brake.. perhaps another p clamp on the rack.. what say ye?

Rowan

If you are going to go that lightweight, just dispense with the rack and get something like a Carradice Camper bag with the SQR support, or look up some of the other threads started by nun or others to see the large seat bags that are being used.

You've already had issues with the dropouts on a CF frame. I am wondering why you would want to push the envelope in this case, too.

BigAura

The material carbon fiber is plenty strong to build a touring bike that'll be comparable to any steel tourer. The situation is carbon bicycles are primarily designed for racing and not specified for touring loads.

A carbon tourer for me means: carrying 202 lbs (me & 37 lbs gear & supplies) on all mixed terrain without worrying about a frame failure. Tour length needs to be measured in months not days. It should easily be counted on to do a full-on world tour

When I see a carbon frame that meets my criteria, I'm onboard. For now I'm not sure the 3-4 pounds of weight savings is worth the worry.

BTW: It's seems that there are 3d-printers spitting out carbon parts, so the day when we can order an affordable custom carbon touring frame is probably not too far off.

Happy Feet

How much stress does you and a fully loaded carradice put on a carbon seat post bouncing on a washboard gravel road? I'm not being facetious, I really wonder about the stresses produced. At least on a normal rack the stress is transmitted straight down into the frame without trying to flex an unsupported tube end.

spectastic

the seatpost is usually overbuilt for strength. it has to support the entire person, so I doubt an extra 30 lbs hanging off the back is a real issue. nevertheless, I'd still like to have a rear rack for convenience of using ortliebs, and having a platform to carry other stuff.. like PIZZA.

spectastic

turns out the serrated non rotation washers on the alfine 8 wasn't the best choice for a carbon frame.. quick release, with a metal washer jb welded onto the dropout, should be much better..

and I don't see it as pushing the envelope. more like digging past the preconceived bias people tend to have against carbon frames as touring rigs.

Rowan

I don't have a bias against carbon framed bikes for touring. But if you select a frame without braze-ons and want to put on racks, you might have made the wrong choice. Aren't CX bikes equipped with braze-ons or eyelets?

As a by the by, if you wanted to persist with the idea of putting a rack on the back of CF frame, look at actually using epoxy and make up the required braze-ons/eyelets. You may need to have the courage to do it, and undertake some research so you can get it reasonably right, but done properly, the set-up would spread the load along the seat or chainstay.

BigAura

Carbon seatposts are designed for downward compression, NOT for a lever to be clamped on and torsional pressures.

spectastic

take your weight multiplied by cos(73 deg) or however much your seat tube angle is. that's how much torsional pressure is being exerted on your seat post. there's also a multiple factor in there that accounts for the setback of the saddle's center of gravity with respect to the seat post's axis of alignment. c'mon, it's an overbuilt tube, not rocket science.

spectastic

what's the advantage of having the braze-ons? is it because it's located near the dropout, and puts the least stress on the tubes?

MassiveD

Obviously BOs are engineered so you know the parts in question can take the loads suggested (well you hope). At one point only custom bikes had all the BOs we now take for granted, which means you could buy a perfectly good touring specific bike like my Peugeot from the 70s, and it had all the gear (save front racks), but fenders, rear racks, lighting system, pump pegs and generators, and it was all banded onto the frame. So it isn't the end of the world to have clips, but carbon does not do well with compression. The cleaver way to attach stuff to carbon if it isn't designed for it is to lash it in place, or use tow and epoxy. Fittings like BOs are neat and all that but not a good way to engineer stuff only carbon tubes, but they are what people are expecting to find.



If you look at the end of the boom on this highly sophisticated maxi-cat, you will notice the load take off is a loop of white webbing. Before carbon booms became the rage that would have been a metal fitting like a BO on a bike. But two things changed, they had to adapt to what carbon likes, and when sailing non-stop around the world in 80 days or less, cordage is king. The other thing is that modern day cordage is cheap and stronger than steel, so you have a toofer. Cordage would have been crazy and worn through from chaffe in the old days, but it is the new normal on boats. You can get a difuse load transfer without any significant preload on your tubes.

MassiveD

I think the stiffer and comfortable stuff is largely hype, one feature carbon does have is generally really inconsistant construction. This is because while the surface is really nice the inside is inconsistent endings of the fabric, so you are really unlikely to have anything repeatable that one could claim behaves one way or another.

Carbon is getting cheaper, though it varies hugely. I was all set to do a carbon spar when the material costs were lower than wood, then 9/11 and the airbus blew the market up for about 10 years.


None of these are for real IF the market demanded touring bikes in carbon.

Eyelets are available on some units like the Tusk fork. But if your rig didn't come with them then it wasn't intended for this use. If you look at compound bows with carbon risers, or Olympic bows, they have all the regular screw-in fittings, and some of them, like the ones that hold on the limbs are heavily loaded.

Can't weld is a nothing, since the better option even for steel is bonding repairs.

Carbon has high impact resistance when properly modelled think arrows.

I don't think it will be stolen more if it is actually cheap. The cheap idea is based on boutique suppliers who are selling low, I don't think there is much evidence real carbon frames will actually be cheap.

Carbon always starts out breaking and being disappointing but if the demand is high enough it eventually becomes rugged, as in the youtube video I shared in a similar thread where they are driving a jeep over the carbon riser of a strung bow.

The real problem with carbon are the alloy fittings, and the lack of custom frame sizes.




Basically these are concerns about your CX frame as a touring frame. These are issues that are made more difficult for being made out of carbon because there is no way of assessing the structure of the bike. Metal bikes are hardly immune to these issues, but to take the high road a properly designed carbon bike is engineered to align fiber with the expected loads. CX load paths are worlds different from touring load paths.

When someone says they like the Surly CX bike for their touring rather than the Surly touring bike(s) they are either making a sophisticated, or more likely ignorant guess about geometry. But the tubing could very well be identical, so you are not going out on a structural limb. The carbon bike should be equally reliable but there is no way of knowing what they did so there is a roll of dice involved.