XC Racing Rims?

Discuss light weight issues concerning mountain bikes & parts.

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mattr
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by mattr

You "move" the flanges by the offset in your calculation.
Unless they are straightpull, then you'll need to get an approximation from one of the online calculators.

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Lelandjt
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by Lelandjt

Yeah, they're straight pull and Extralite doesn't list flange dimensions, just recommended spoke lengths based on rim ERD. I'm looking for an approximation like, "lose 1mm of spoke length for every 3mm of rim offset."

Really though I'm leaning strongly toward the non-asym Light Bicycle rim cuz 360g is pretty light, $165+ shipping is sweet, and just use the spoke length Extralite recommends.

by Weenie


mattr
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by mattr

Might be easier to do a mock up build on the same rims on a calculator. Then add an offset. Compare the difference.

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Lelandjt
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by Lelandjt

Good thinking.

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LeDuke
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by LeDuke

Perhaps not what you're looking for, but two pre-built wheels that come to mind:

The new Roval Control SLs. 25mm internal, 1330g. DT Swiss hubs.

The Bontrager Kovee XXXs. 29mm internal, 1390 for the set, DT 240s.

Buy the wheels, swap in new hubs and spokes if that suits you.

If you swapped in some Extralite hubs, you'd be looking at 25 or 29mm ID wheels at a sub-1300g weight. That's not too shabby.

KWalker
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by KWalker

I don't see the need to push the ID that wide on an XC racing rim. There are not that many tires beyond 2.3 to where the tire weight does not significantly increase. A few mm wider in the ID will only change the casing by a small amount, esp if you want to believe Enve. Supposedly some of the Trek widers run their casing on the wider side, but for the most part I haven't seen that many people run beyond a 2.2. If you're really so weight conscious that you want to use a very fair-weather hub in the Extralite, then you are not the type of rider that is going to run a tire that is 200g heavier a piece, which many 2.4s are.

I would build to Skylines front and rear. Don't see the need for any extra weight up front unless you're doing a lot of trail riding and want to swap to some 2.4s occasionally. Probably use a lighter tire like a Schwalbe, CX Rays, and a Tune or Carbon-Ti hub with some Ashima rotors and ti bolts. You can build lighter, but you also get some massive risks.
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UpFromOne
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by UpFromOne

Lelandjt wrote:
UpFromOne wrote:Duke Lucky Jack = bang for the buck. Gotta love asymmetric spoke holes.

Extralite lists spoke lengths for their hubs based on rim ERD. How would you modify that length for the 2.5 - 3.5mm offset rims?


In the 2-3mm asymmetric range, that really doesn't affect spoke length enough to add or subtract from the recommended.

mattr
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by mattr

I did a quick mock up last night, added a 3mm offset to an XT hub with a road rim.

Difference was around/slightly under a mm depending on 2x/3x and number of spokes.

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Lelandjt
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by Lelandjt

KWalker wrote:I don't see the need to push the ID that wide on an XC racing rim. There are not that many tires beyond 2.3 to where the tire weight does not significantly increase. A few mm wider in the ID will only change the casing by a small amount, esp if you want to believe Enve. Supposedly some of the Trek widers run their casing on the wider side, but for the most part I haven't seen that many people run beyond a 2.2. If you're really so weight conscious that you want to use a very fair-weather hub in the Extralite, then you are not the type of rider that is going to run a tire that is 200g heavier a piece, which many 2.4s are.

I would build to Skylines front and rear. Don't see the need for any extra weight up front unless you're doing a lot of trail riding and want to swap to some 2.4s occasionally. Probably use a lighter tire like a Schwalbe, CX Rays, and a Tune or Carbon-Ti hub with some Ashima rotors and ti bolts. You can build lighter, but you also get some massive risks.

Yeah, I'm not looking for a rim wider than 23-24mm and would be fine with 21-22mm. What I want is sub 350g. This bike will only have XC tires and they'll always be the limiting factor. If I want to do a gnarlier trail ride or for certain race courses I'll use my 5010 (23-24lb depending on tires). I've been XC racing on trail bikes since 2003 and love the feel of them but I can't even remember what a pure XC bike feels like so I'm building one up.

Now about those hubs. I've exclusively used DT 240s for longer than I can remember so school me on these Euro ultra-light hubs. If ridden by a skilled XC weight rider and cared for by a professional mechanic do I have anything to worry about? I'm not gonna overly tighten the thru-axles and I only ride in the wet during races but I don't want something so delicate that it could break down on me during a road trip or race. Do you prefer Carbon-Ti or Tune over Extralite? If the DT 180s are available in Boost I was gonna go that route cuz I figured they're the same as my 240s, just more money and less grams. No idea when those will be available though. I heard some praise for Extralite and the weight is awesome so right now they're at the top of my list.

KWalker
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by KWalker

I wouldn't trust a generic Asian rim that is sub 350. The only two I would trust in that range are MCFK or Nox.

From every builder I have spoken to Extralite hubs are very fairweather and require more maintenance/cleaning than I would care for. It's a mountain bike, after all. I don't see the reason to spend so much on 180s. Carbon-Ti have a great design, great wheelbuilding geometry, great weight, and are more robust. Even if you don't slop around in the mud, they will get grimey in there.

Man if you can race well on a 5010 I don't see the point in this unless it's a weenie'd out hardtail that's down in the 17lb range. It takes a lot for FS to get sub 20 and even then if your trail bikes are 23 it isn't a massive difference. With that said it's always fun to nerd out on a build and push it's limits!
Don't take me too seriously. The only person that doesn't hate Froome.
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Lelandjt
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by Lelandjt

Yeah, Nox is looking good since it's a little lighter than LB and asymetric doesn't look like it complicates the spoke length selection much. I have to get over the difference in price but they'll give me EP and the rest of this build is so rediculously $$$$ that a couple hundred extra for rims shouldn't be a big deal. Having said that, I've got the 27" version of those LB rims on my 5010 and they've been bombproof even in enduro races. I love racing my 5010 but on certain courses I'm aware that the 27" wheels give up a little speed, it's a couple pounds heavier than my competition, and I just don't need its capabilities. I also just feel like treating myself to my first real XC bike since 2002. It's gonna be Spark RC SL and should be about 20lbs.

I'll take a good look at Carbon-Ti hubs.

KWalker
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by KWalker

PM Ergott. He built up a set of Carbon-Ti hubs for a friend/forum member and he/Fairwheel can give you a really good breakdown of the plusses and minuses of all the current hub options. They have great preload, good bearings, good dimensions, and a robust freehub.

You also can't put a price on QC/Warranty. Nox offers discounted rims especially for rock strikes. Try getting that from a Chinese importer. I would be more skeptical of the rim the smaller the tire diameter. 27" rims have more volume and tire as well as more suspension travel.
Don't take me too seriously. The only person that doesn't hate Froome.
Gramz
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Gullholm
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by Gullholm

I wouldn't say I'm very hard on hubs, being about 72-76kg in the summer and mostly ride in fair weather, so maybe I can get away with more than others. I do however squat between 140-185kg depending on how much I hit the gym so got a bit of power at least to put down (I know, who cares about squats but I ain't got no powermeter haha).

Over the years I've been riding several sets of DT 240/180s, old DT pawl hubs, Bontrager pawl hubs, Tune King/Kongs, Syncros with DT internals, Sram front hubs and now Extralite HyperBoost2.
Broke a DT pawl hub and I've had slips with every other pawl hub including the Tune even though they've all held up. One Tune King front hub developed bearing play quite soon.
Never ever had a slip with DT star ratchet hubs or with the HyperBoost, no trouble with bearings on the DT's and so far so good on the Extralites. And no wear to worry about yet on the Extralite freehub/hubshell.
So this has made me prefer ratchet style hubs and even though I know that many pawl style hubs are really good I'm still hesitant about getting them.

Of course the freewheel system on the Extralite isn't as bombproof as DT when it comes to wear, but one good thing with the current updated version of the Hyperhubs is that if you would however mess up (as in riding tons in bad weather and neglecting service) and notice that the system has been worn you "only" need a new freehub and ratchet and have another chance. On the first version, if you wore them out the hubshell was bust too but now you have two ways of fitting the star ratchet so if one gets worn out you just switch position in the hubshell when installing a new one.

Like I said, I don't usually destroy or wear out hubs and I don't see too many highend hubs in the shop I work at so maybe I'm not the best source of info - still just wanted to share my experience. :beerchug:

A friend is soon getting Carbon-Ti hubs though, and I certainly won't try to stop him because they do most definitely look nice too.

tonytourist
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by tonytourist

One of my riding partners has a set of MCFK 29" rims on Carbon Ti hubs and has been running them since August with 0 issues, I'm running a set of the Carbon Ti hubs on my road bike (as well as my pictured set of MTB wheels) and have 0 complaints so far. While I'm sure they will give up a bit of durability to something like my DT240s on my Enve M50s, from what I have seen they hold up just fine. Most WW gear ends up with a compromise or two, so if I have to service them a little more that is worth it to me for the weight savings.

KWalker
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by KWalker

Ergott builds solid wheels too- if you desire a Nox/Carbon-Ti build he's a good guy to go to.
Don't take me too seriously. The only person that doesn't hate Froome.
Gramz
Failed Custom Bike

by Weenie


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