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Discussion Starter #1
As I'm becoming more and more into aggresive XC / Light freeride, I'm currently changing my 5.5 wheels&tires setup. My current setup is:
Front: WTB Dual duty XC + MOTOraptor 2.24 + eclipse
Rear: Salsa Semi + Pana. Fire XC + eclipse

The rear is easy, I'm just replacing the tire to my the moto 2.24 (which is almost new)
For the front, I've decided to get the Schwable Fat Albert 2.35 and build a new Mavic UST wheel.
My trail conditions are dry rocky, dry hard-pack, dry loose and everything in between - no mud (did I mention it's dry here?)
I weigh about 180lbs and somtimes take up to 6 feet drops...

Question is, which rim to take, the XM819 UST or the EX823 UST (asuming I'll find one).
 

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Brass Nipples!
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Decisions, decisions!

The 819 is a very stiff rim. It would be fine for your weight for general trailbiking. The 6 foot drops have me a little worried. If you land well, you'll probably be OK.

Consider the tire size you'll run in the future. The 819's are only recommended for up to 2.3 inch tires. The 823's are good for 2.1 (minimum) to 3.0 inchers. If you value strength over all and you will be getting more aggressive, you'd probably be best off with the 823's. You should consider 2.0/1.8 mm spokes with brass nipples for your build either way. Make sure whoever builds the wheels follows Mavic's recommendations.
 

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Bob the Wheelbuilder said:
...Consider the tire size you'll run in the future. The 819's are only recommended for up to 2.3 inch tires. The 823's are good for 2.1 (minimum) to 3.0 inchers...
Mavic is VERY conservative with their size recommendations. It is reasonable to run most any size tires on either rim. I use 2.6 tires on rims narrower than the 819 and have used 1.5s on rims wider than the 823. And I use everything on my 819s. If you are doing a big drops/air with big tires you are better off with the wider rims.
 

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I was in exactly the same boat as you last month. I didn't get any definitive answers either. I'm about 150 lbs on the bike and ride a Santa Cruz Heckler with 5.5" rear travel set fairly plush. I was also riding the Panaracer FireXC Pro 2.1 on the rear with a tube; however, my weight-weenie's Mavic X317 (XC717 nowadays) couldn't hack it. I definitely abused the rim with the rocky riding in the Canadian shield and probably ran rear tire pressures too low. It was definitely somewhere between 20 - 30 psi. It eventually accumulated too many rim dents and flat spots. When it finally gave up the ghost, I bought a Mavic XM819 disc and a Weirwolf 2.1 UST rear tire. Wheel building is also critical. Make sure you get a hand-built wheel.

I took it downhilling for two days at Bromont as an acid test, which is very rocky and rooty with lots of jumps loose chunky debris. I mostly rode extreme double-diamonds so it saw a lot of abuse. The rim worked fine. No dents or flat spots. Still true. I think I felt it bottom once . . . whereupon I promptly re-adjusted the tire pressure to avoid further occurances. The Weirwolf 2.1 UST tire didn't work so well. I think it is better for rolling resistance but on wet XC rides, I slipped quite a bit more than the Panaracer FireXC Pro clincher tire with a tube. It was also pretty bad at Bromont in the wet. I prefer a safe 30 psi but I had to reduce tire pressures to around 25 psi to get by on the slippery DH. Of course, that increased the likelihood of rim damage but the rim survived nonetheless. The bike also handled kinda funny with a clincher / tube Weirwolf 2.5 up front and a tubeless Weirwolf 2.1 on the rear. I had to lower my front tire pressure to prevent understeer (which eventually pinch flatted so it was also too low) and even then this combo wasn't as good as my Weirwolf 2.5 up front and FireXC Pro / tube on the rear. I hoped the greater traction from a UST tire would allow me to increase my rear tire pressure while maintaining good traction but that was not the case with this Weirwolf 2.1 UST rear tire.

I'm gonna try a clincher Kenda Kinetics 2.35" tire perhaps with some of that Stan's No-Tube stuff. I like the lower rolling resistance from tubeless but the limited skinny tire selection is getting me down. I asked WTB if they would consider a Weirwolf 2.3 or 2.5 UST but they couldn't justify the business case for now. That's a shame because I think their Weirwolf tire might have worked better if it was wider.

I wish I could have given you a direct comparison against the XM823 but I've only tried the XM819. The rim survived a two-day torture test despite extremely low rear tire pressures - far worse than anybody with an eye on reliability would recommend. I had no choice at the time. Ultimately, I think tire selection and wheel build-quality will be critical to long-term rim survival. UST also seems worthwhile for lower rolling resistance - but only if you can find the right tire.

Good luck.

Dave.
 

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TheNewOriginal said:
As I'm becoming more and more into aggresive XC / Light freeride, I'm currently changing my 5.5 wheels&tires setup. My current setup is:
Front: WTB Dual duty XC + MOTOraptor 2.24 + eclipse
Rear: Salsa Semi + Pana. Fire XC + eclipse

The rear is easy, I'm just replacing the tire to my the moto 2.24 (which is almost new)
For the front, I've decided to get the Schwable Fat Albert 2.35 and build a new Mavic UST wheel.
My trail conditions are dry rocky, dry hard-pack, dry loose and everything in between - no mud (did I mention it's dry here?)
I weigh about 180lbs and somtimes take up to 6 feet drops...

Question is, which rim to take, the XM819 UST or the EX823 UST (asuming I'll find one).
Go with the 823. It is a stronger and wider rim. All things being equal, it should also give you a wider tire contact patch and less tire roll over with bigger tires. It's always better to err on the side of caution especially if your going to be doing drops. Just my $0.02

Good luck getting the 823s. I've been waiting a while and so have others. Apparently they have been discontinued and will be replaced by an 05 model which won't be out until Sep. or Oct. at the earliest.

Duc
 

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Discussion Starter #6
Thanks for all the responses

Thanks for the input guys,
I took a ride on my buddy's Epic, which is equipped with XM819,
The ride was nice but I don't think the XM819 will give me much confidence when jumping around (it's a lot skinnier than my current WTB dual duty XC...)

So, I've ordered the EX823, hope the guys at startbike.com still have some.

Oh, and my XC friends just love the idea that I'll have some extra spinning weight...
thanks again,
Ilan.
 
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