Carbon rims – are they all they're cracked up to be?

I like mine, but that’s probably because I’m gullible, curious about kit and not a particularly aggressive rider. I also bought into hyped-up stuff like disc bakes, tubeless tyres set-ups, dropper posts etc though not alternative wheel sizes. I don’t think carbon rims give as significant a gain as any of those, especially if you get into stuff like Enve with high prices, but I think they do have a distinctive feel which I quite like. Anyway…

Single most honest paragraph about new kit ever written on STW, should be the reference answer to every new kit thread…

I recently cracked a Nextie fatbike rim with a pretty mild knock off a rock. That’s the real problem with carbon imo. It’s massively strong and stiff, but a knock in the wrong place can trash it alarmingly easily. My old Rolling darryl ally rims soaked up loads of harder hits, they were ful of dents and flat spots but are still working perfectly fine.

I’m not the only one.[/url]

Tubeless set up on the Nextie is fantastic though, really easy and secure.
The other rim on the front has just done a week of rocky hammering in Spain with no issues, but I feel I’m always waiting for that next hit at just the wrong angle which will take it out…

Why do you need a 40mm wide rim? I still remain to be convinced it in real terms makes any difference whatsoever. I can show a picture of the same tyre, one mounted to a 23.4mm internal width rim and one mounted to a 30mm rim & they look exactly the same.

Regarding the lower pressure thing – again if you don’t ride hard. Otherwise it feels like a nasty, squirming flat tyre that’s more likely to pinch flat & crack the rim. So, in reality, lots of issues.

I like the feel of them, so far in the 6 months I have been riding them I have had zero burps, compared to one every couple of weeks on flows. I can show you a picture of a tyre, one mounted to a 23.4mm internal rim and another mounted to a 30mm rim and they look completely different – all it points to is tyre selection becomes important when you go to wider rims.

Low pressure on flows feels like a flat just as you described, but on a wider rim it doesn’t the squirm is gone – and its for those reasons I like them. For others you might not lend importance to these factors, so justification becomes even harder.

They will not revolutionise riding in anyway, but they make small marginal improvements FOR ME (not measured in seconds but feel) and I can, so I will – simple really.

Riding my old bike with flows etc now feels like a lumbering beast. Did I think it felt like that at the time, of course not it felt great. But on that level my first car felt like it was amazing at the time, going back to an E reg fiesta nowadays doesn’t feel so great – doesn’t mean it doesn’t work as a car, but my reference points have changed

Last year we were at Afan & found a mashed up rider at the end of one of the trails (can’t remember which one). His carbon rimmed front wheel had disintergrated on the descent. It put me off ever trying them anyway, at least ali bends!

Northwind – Member

P-Jay – Member

I don’t get it then? They cost a fortune, the advantage not being lightness, because they’re not, they’re stiffer – but that makes for a harsh ride so you lower tyre pressure to make them more compliant which negates the stiffness.

You don’t think they’re lighter than an equivalent metal rim? Your post is a bit hard to read but that seems to be what you’re saying

I was referring to Deviant’s post above – the claim being that for an equivalent built (AM/Endruo/DH anyway) that they’re actually heavier than an Alu rim – I suspect especially if you’re talking the same price because they’re really expensive.

My question was this, if they’re no lighter, and the stiffness they offer can be a drawback that requires lower tyres pressure to over-come, and they by reducing tyre pressure you lose the stiff feel – what exactly is the point other than ‘bling’?

You can have light 40mm rims in alloy too.
syntace w40

I’ve been very impressed with these.

andywill – Member

Last year we were at Afan & found a mashed up rider at the end of one of the trails (can’t remember which one). His carbon rimmed front wheel had disintergrated on the descent. It put me off ever trying them anyway, at least ali bends!

I agree with the sentiment, but whilst I’ve dinged a few rims in my time and knocked a few out of true – if you suffer the ‘full taco’ which I have once or twice you’re going to crash hard.

I Like my lb 35mm dh rims.

Done a lot on them and they’re sound.

Will be buying a second set soon I reckon.

I’m light and ride very aggressively, coming off a flow ex that I cracked in 3 places and was flat spotted everywhere.

Think I’m gonna run flows in whistler next year though.

Definitely lighter than an equivalent alu rim, dunno if it’s the lighter weight or the stiffness but they feel like they accelerate quicker

I’m trying to break my cracked rear lb rim and it just won’t die !

Those syntace are light but still 100g heavier than carbon equivalents for the same price, strongr? I don’t know

The disintegration factor is really a question of design rather than a C/F problem, but obviously there’s plenty C/F rims that simply are too lightweight for the job.

Rims need to be both stiff and impact resistant.

I’m trying to break my cracked rear lb rim and it just won’t die !

Please stop riding your cracked rim.

Have a read of this,
LINK

The full story emerges in the comment section

P-Jay – Member

I was referring to Deviant’s post above – the claim being that for an equivalent built (AM/Endruo/DH anyway) that they’re actually heavier than an Alu rim

OK, I’ve no idea what Deviant was talking about tbf. Personally, I wouldn’t put carbon rims on a dh bike any more than I’d fit an XTR mech, everything on my dh bike was picked to be strong enough to work and cheap enough to not worry about when I throw it in a cattle truck or ride it into a tree, or ride off the hill on a flat- my carbon wheels fit the former but not the latter 😆 The light weight just isn’t worth it for that job, for me.

Isn’t it funny how people argue so vehemently about carbon rims, but generally, the MTB community is falling over itself to get hold of the newest and greatest carbon vunder-bike frame, and doesn’t bat an eyelid about carbon forks or bars?

Not a fan of the bars either to be honest.

I snapped a Pro-taper carbon bar in a feeble crash. A mate of mine got ejected into the woods at high speed when his Burgtec let go on a DH track.

Nah, you can keep them.

To be fair though, those bits aren’t really impact parts whereas in normal use (and not just crashes) rims will sometimes get thumped. So I can see why people have a different attitude.

And to make it realistic for most folks it means “cheap carbon” which understandably people shy away from. Whereas a top end carbon bar isn’t thousands of quid.

I’ve broken a couple of alu bars and a bunch of alu rims so it’s not like I think carbon is indestructible, I just don’t kid myself that alu is either. And I don’t put anything on a mountain bike that I can’t deal with breaking. But then, my old easton monkey dhs proved way stronger than the answer alu dh bars they replaced.

Isn’t it funny how people argue so vehemently about carbon rims, but generally, the MTB community is falling over itself to get hold of the newest and greatest carbon vunder-bike frame, and doesn’t bat an eyelid about carbon forks or bars?

Nope nope and nope again….Renthal Alu bars on my bike (proven in the Motorcycle industry), Giant Alu frame (admittedly worrying light to pick up but i reckon it wont suffer a catastrophic failure)….it may bend, dent etc but should give me some warning….metal crank arms too, really really get nervous and twitchy about my ankles and carbon cranks just make me feel nauseous thinking about them letting go on a descent….maybe i’m old fashioned but i think if i’m chucking it down the side of a hill at 40-60kph i want total faith in the components and carbon isnt quite there for me yet….its still in the new/beta phase for MTBing in my opinion….i’d go out of my way to avoid a carbon frame, i did just that with the Trance i bought…could’ve got the ‘advanced’ version (carbon) instead chose the metal one….i just dont see the carbon one sitting in my shed in 5 years time ready to be ridden like i assume the metal one will be.

I’m even more of a luddite with HTs where i want the least amount of maintenance possible and that usually means steel!

I disagree, frames are bounced off rocks routinely and bars are prone to digging into the ground on virtually every stack. Theres some high point load impacts and twisting moment right there, just like a rim.

deviant – Member

Renthal Alu bars on my bike (proven in the Motorcycle industry)

Different product made to a different design with a different process in (I think) a different country. So is it the company you trust? But then they also make carbon bars. And other people make bad alu bars.

So presumably it’s the brand you trust? But they also make carbon bars.

Indeed, i dont think they’d ruin their carefully built reputation for tough bars by putting crap out there for MTBers….you only have to see how few crop up second hand on ebay to appreciate that owners buy them and keep hold of them….if i was going to try carbon bars it’d probably be theirs.

Carbon Fibre has a better strength to weight ratio than alu.

So as long as the likes of Enve, LB can do a descent job of turning this material into a rim then you should be able to run lighter carbon wheels without sacrificing strength.

So this us where the real advantages kick in from having a lighter wheel. 100g lost from a wheel has more of an impact than 100g lost from the frame.