Ask the experts

[Falcon3]

Does this look like a fake chain? KMCx11.it wasn’t the cheapest on eBay and the seller had good feedback.

But the pins look funky to me. A couple of them seem to stick out past the plates as well.

[XXX-er]

sez KMC , I've run a KMC and it was ok, not any better or worse than Shimano or Sram of the correct spec

just like the other brands they have different qualities of product

[XXX-er]

Riding with shop bro last weekend, shop bro knows a thing or 2 about destroying equipment so while tightening a loose spoke on this Norco sight with aluminium rims before the ride

he said the thing about carbon rims is you never have to tighten the spokes ever period in his experiance BUT they often aren't any lighter

so I countered they sound like a waste of money for me cuz i havent had to tighten the spokes on the aluminium DT swiss on my Yeti

yeah probably not

[jamal]

My carbon wheels and an xo1 cassette dropped a full pound from my bike, so about 350g with the wheelset alone. They're listed at 1544 so I guess the stock ones (dt370 to i27 light) were like 1900. They feel really nice pedaling hard and make whole bike more agile. Downside is I worry about hitting rocks too hard and the ride is harsher and they were expensive. In my chart of components and their weights and costs it wasn't a good $/g value. But it was a lot of grams. And during my last race I felt they were worth it.

[rideit]

so I countered they sound like a waste of money for me cuz i havent had to tighten the spokes on the aluminium DT swiss on my Yeti

Sounds like you’re not givin’er properly, ya hoser

[XXX-er]

Sounds like you’re not givin’er properly, ya hoser

well I can only do so much with all this soil but i do try to hit as many rocks as I can

and Shop bro is happy to sell you dentists all the carbon you can afford

i think he was talking about 2000 grams being the reasonable build

[Falcon3]

sez KMC , I've run a KMC and it was ok, not any better or worse than Shimano or Sram of the correct spec

just like the other brands they have different qualities of product

Thanks I found on their website a fake identifier. Looks like mine is legit, but I’m not impressed by the quality. Shifts fine for now

[XXX-er]

might be older product ?

Should be fine

[jamal]

I've gone through a number of X11SLs and found them to be pretty nice, although that one's not an SL. And longer lasting than shimano and some sram chains (xx1 eagle seems pretty durable).

[detrusor]

Thoughts on best way to increase high speed compression on my fox float Dps I’m running on a ripley v4? Going to add a spacer and I turned the black thingy up from1 to 3….


Sent from my iPhone using TGR Forums

[climberevan]

Before switching to a DVO Topaz I had increased to the next size spacer in the Fox on my Ripley. It helped to keep it from blowing through the travel, but the Topaz solves the problem completely. Especially on the kind of downhills people would think need a bigger bike, the Topaz & Diamond fork really just deal with the hits.

[stuckathuntermtn]

When you guys say harsher ride, is it that bag a deal on a full squish? BTLOS asymmetrical 29 is way lighter than 30 symmetrical. No idea why.
Why do I still think my original idea was the best? I can pick up a couple extra spokes if they tell me the length, and I honestly doubt I'd break them anyway.

[J. Barron DeJong]

When you guys say harsher ride, is it that bag a deal on a full squish? BTLOS asymmetrical 29 is way lighter than 30 symmetrical. No idea why.
Why do I still think my original idea was the best? I can pick up a couple extra spokes if they tell me the length, and I honestly doubt I'd break them anyway.

The rim I’ve been considering is the M-i30AS (30mm internal, asymmetric, shallow). It’s only about 25g more than the M-i29A.

No idea how much difference the shallow rim makes in ride quality, just seems like that’s the direction the market has been headed.

[climberevan]

I went with the shallow on our 2 latest BTLOS sets (27 & 30mm) for the claimed better impact resistance. I doubt anyone could notice the ride difference even on a rigid bike. Wheels don't flex vertically, at least not enough to be detected with tires at 20-30psi. 2psi would make a bigger difference than going from the stiffest to the most flexible rim. It's like the old wiring and soldering spokes thing--there are lots of myths regarding wheels still floating around out there.

[toast2266]

I went with the shallow on our 2 latest BTLOS sets (27 & 30mm) for the claimed better impact resistance. I doubt anyone could notice the ride difference even on a rigid bike. Wheels don't flex vertically, at least not enough to be detected with tires at 20-30psi. 2psi would make a bigger difference than going from the stiffest to the most flexible rim. It's like the old wiring and soldering spokes thing--there are lots of myths regarding wheels still floating around out there.

I must be surrounded by delicate flowers, because I and pretty much everyone I know can definitely feel a difference in the vertical compliance of different rims.

[toast2266]

Wheelie mags:

I’m having a hell of a time learning to wheelie. I have a pretty good grasp of the fore and aft balance; elbows locked, head up, brake modulation but I keep falling to the side. I’ve tried turning the wheel. What is the hip motion? Any drills to practice?

Lower your seat a little bit. Side to side balance is done with your knees. If your seat is too high, your legs are straighter and it's harder to swing your knees out to the sides.

[volklpowdermaniac]

Wheelie mags:

I’m having a hell of a time learning to wheelie. I have a pretty good grasp of the fore and aft balance; elbows locked, head up, brake modulation but I keep falling to the side. I’ve tried turning the wheel. What is the hip motion? Any drills to practice?

Vision vision vision.

Keep your head and eyes up and looking straight ahead. It’s amazing how much that has helped me, our eyes are powerful, we look up and ski to spaces not to trees , same concept. But all the other advise is sound as well.

[climberevan]

I must be surrounded by delicate flowers, because I and pretty much everyone I know can definitely feel a difference in the vertical compliance of different rims.

I'd bet a carbon wheelset that the results would be inconclusive at best if a blind test using the same bike, tires, and tire pressure could be carried out.

Nox has this to say on the question:

"It should be clear now that not only can no rider can discern the difference in vertical compliance between any two wheels, but rather these perceived differences must be coming from changes in tire volume, air pressure changes (even a few psi makes a big difference), tire casing, or even frame/fork/stem/handlebar flex."

Full quote:


"Vertical Compliance and Carbon Rims

Let’s talk a bit about vertical compliance. We often get questions like “are carbon wheels too harsh?” or “I heard carbon wheels make the bike really uncomfortable, is that true?" The short answer is no, you will not be able to tell any difference in vertical compliance between a carbon wheel and an aluminum wheel. In short, changes in vertical compliance between two wheel setups can be contributed to other factors like tire volume, tire casing, tire pressure, frame flex, handlebar flex etc., not the wheel setups. No spoked bicycle wheel, even super-light alloy wheels with thin gauge spokes, have enough vertical compliance for you to feel a difference. If you are interested in proof of this, keep reading.

First, let’s be clear that in terms of vertical compliance we are talking about displacement due to low radial stiffness. Stiffness (k) is defined below, where F = force (mass x acceleration) and δ = displacement. So given the same radial forces, for a rim to have a "high" level of vertical compliance (displacement) it would need to have low radial stiffness.


From Gavin’s elastic frame analysis*, it has been shown that for a typical bicycle wheel, the radial stiffness (k) is on the order of 2500-4500 N/mm depending on the spoke gauge, lacing pattern, the elastic modulus of the rim and moment of inertia of the rim. Gavin’s work was based on typical aluminum rims, so he used a value of 69 GPa for the elastic modulus and he analyzed over a range of bending moments of inertia from 500-1500mm^4. Carbon fiber has a higher elastic modulus, about 181 GPa. The rim's bending moment of inertia depends of the thickness of material and shape of the rim, which will be close between the two materials, so let’s just keep it simple and assume that the bending moment of inertia is the same between a given aluminum rim and carbon rim.

So the point of all this is to compare vertical compliance between an aluminum rim and a carbon rim, so let’s run some numbers and see what we get. Let’s first assume a 165lb rider on a 30lb bike, so about 90kg. Let’s also assume that the weight is distributed 60/40 between the two wheels, so we’ll say 54kg of mass is loading the rear wheel. And the final assumption is that we’re using the same 1.8mm spokes with both wheels. So, from Gavin’s* paper (Figure 5) we see stiffness values of about 3500 N/mm for an aluminum rim with a middle of the road bending moment of inertia (1000mm^4). So just sitting on the bike, with the acceleration of the wheel due only to gravity, (1G or 9.8 m/s^2), we get:



So obviously there is VERY little vertical displacement at only 6 thousandths of an inch! But let’s make things more complicated and say you are ripping along a trail and hitting some 2” roots at high speed. This seems to be a typical scenario people describe when they say they feel a wheel has low vertical compliance. A 2” root hit at 15mph would introduce about ~3Gs into the wheel system (based on an a simplified calculation, an accelerometer mounted on the wheel would be ideal to get real-world numbers, but this is close). So running the numbers again for 3Gs of acceleration we get





Now, not surprisingly, a carbon rim has a higher elastic modulus than an aluminum rim, that is, it is more resistive to elastic deformation with a given force applied to it. Let’s be generous and assume the increase in the rim modulus equates to a wheel with a radial stiffness twice as high as our sample aluminum rim. So the aluminum rim was 3500 N/mm, let's say our carbon rim is 7000 N/mm. Calculating the deflections values we get:



And again hitting that same 2” log at 15mph (3Gs acceleration) would result in a deflection of:





Rim Type

Acceleration (165lb rider)

Vertical Deflection

Aluminum

Static Deflection (1G)

0.006 inches

Aluminum

High Speed Impact (3Gs)

0.018 inches

Carbon

Static Deflection (1G)

0.003 inches

Carbon

High Speed Impact (3Gs)

0.009 inches



From the table above, you can see that the difference in deflection between an aluminum rim and a carbon rim is (at maximum) 0.009 inches. That's about the thickness of 9 human hairs! In short, it's just not possible for a rider to discern that small of a change. So why do people swear they feel these differences?

Let's consider the vertical compliance due to your tires. A typical 29x2.25” tire is about 50mm tall. Even if we leave all the calculations aside (which are surprisingly complicated), most of us run pressures off-road of about 20-30psi, which generally results in ~20% tire drop (0.39 inches) when you are sitting on the bike. With correct tire pressure for your weight, a direct impact with a 2” diameter log at 15 mph will result in a ~50% (0.98 inches) collapse of the tire casing as it absorbs the impact. So the tire deformation provides more than 100 TIMES the vertical compliance than that of the wheel, whether it is aluminum or carbon. It should be clear now that not only can no rider can discern the difference in vertical compliance between any two wheels, but rather these perceived differences must be coming from changes in tire volume, air pressure changes (even a few psi makes a big difference), tire casing, or even frame/fork/stem/handlebar flex. Keep in mind that wide rims increase the volume of the tire, so if you are coming from narrow aluminum rims to our wider carbon rims, not only should you not be worried about less vertical compliance, you should actually expect an increase in vertical compliance (comfort) due to higher tire volume!



*References:
Brandt, Jobst. The Bicycle Wheel, Avocet, 1993.
Rinard, Damon. Damon Rinard's Wheel Stiffness Test, url: http://sheldonbrown.com/rinard/wheel/index.htm, last accessed 09/2013.
Gavin, Henri, Bicycle Wheel Spoke Patterns and Spoke Fatigue, url: http://people.duke.edu/~hpgavin/pape...heel-Paper.pdf. last accessed 09/2013"

[toast2266]

I'd bet a carbon wheelset that the results would be inconclusive at best if a blind test using the same bike, tires, and tire pressure could be carried out.

Nox has this to say on the question:
...

Yeah, I've read that before. I think they're wrong.

Here's a video of a carbon rim impact test. The impact doesn't bottom out on the rim, so it's not a particularly hard hit. If I'm riding a rough downhill, I'd guess I encounter an impact like this every 100 feet or so. And that rim is flexing quite a bit. Certainly more than the tiny fraction of an inch that Nox is saying happens. And this video is for an older rim, which I'd bet is stiffer than some of the newer rims that have more vertical compliance built into them.



I've ridden a lot of different carbon rims. Same bikes, same tires, same tire pressures. Differences in flex (both vertical and lateral) are most definitely noticeable.

[stradissimo]

I’m with Toast. Nox is doing marketing, not engineering. 3G impact... laughable.

Jobst Brandt used to argue on usenet forums that it was physically impossible for a motorcycle to lean more than 45 degrees in a turn without falling over. Clearly, he’s someone for whom ideas take precedence over evidence. He had a magical ability to ignore pictures of people like Wayne Rainey and Mick Doohan leaning more than his theoretical limit.

[JPaul]

^ My wallet makes sure I don't have a dog in this race, but that rim failed on the first hit.

Can't do that every 100 feet or so, but I'd be curious what kind of load they were using to get that result.

[toast2266]

^ My wallet makes sure I don't have a dog in this race, but that rim failed on the first hit.

Can't do that every 100 feet or so, but I'd be curious what kind of load they were using to get that result.

Yeah, per the comments, they had the spokes strung up extra tight and it was still in prototyping stages. But the fact remains that their impact didn't bottom out on the rim. So not it wasn't an enormous load.

[climberevan]

Yeah, I've read that before. I think they're wrong.

Here's a video of a carbon rim impact test. The impact doesn't bottom out on the rim, so it's not a particularly hard hit. If I'm riding a rough downhill, I'd guess I encounter an impact like this every 100 feet or so. And that rim is flexing quite a bit. Certainly more than the tiny fraction of an inch that Nox is saying happens. And this video is for an older rim, which I'd bet is stiffer than some of the newer rims that have more vertical compliance built into them.



I've ridden a lot of different carbon rims. Same bikes, same tires, same tire pressures. Differences in flex (both vertical and lateral) are most definitely noticeable.

What? That ram is absolutely compressing the tire completely and hitting the rim. If you're doing that every 100 feet or so you are running too little tire pressure, and you're buying a lot of new rims. Obviously if the rim is being directly hit by something it will flex/break. My argument assumes that you have enough tire pressure to keep the rims themselves from hitting stuff. Anyway, I won't continue to argue with your anecdata. Science is useless against that.

[toast2266]

What? That ram is absolutely compressing the tire completely and hitting the rim. If you're doing that every 100 feet or so you are running too little tire pressure, and you're buying a lot of new rims. Obviously if the rim is being directly hit by something it will flex/break. My argument assumes that you have enough tire pressure to keep the rims themselves from hitting stuff. Anyway, I won't continue to argue with your anecdata. Science is useless against that.

What rim impact?




There are two kinds of engineers. There are those that do a bunch of calculations and then try to tell everyone that they're not feeling what they're feeling because it doesn't agree with the calculations. And there are those engineers that take what everyone is feeling and try to engineer their products around it. Which is why almost every successful carbon rim manufacturer has pushed to add more vertical compliance into their rims, because it was pretty much universally agreed that most of the early carbon rims were too stiff. And then there's Nox, who I haven't really heard anything about in a few years.

[stuckathuntermtn]

So, I don't expect the weight to be super accurate on BTLOS's or Light Bicycle's websites, but similar wheel builds (30mm internal, 28 straight-pull bladed spokes, dt swiss hubs, brass nipples) are different by 100g.
So, at least 1 of these is wrong.
Or maybe I was doing the shallow one. Those seem fragile. Seriously, if I am on a full suspension with 150mm and 130mm travel, do I really need that much compliance? Pike and Deluxe Ultimates.
Edit: nope, not shallow. Standard 30mm internal, matte, UD. Not premium, not enduro.