i know the carbon rush 2 is but....
what should i change out first to make it even lighter? and how much lighter are the mavic slr rims compared to the mavic 819 thats on my bike now?
The Mavic SLR only comes as a complete wheelset, not available as rim only. The SLR is around 1560g and the 819 I believe is around 1800g so you would save about 240g or 1/2lb weight. The SLR is much stiffer than the 819 rim build due mainly to the 24 spoke configuration. Worth noting the SLR is only meant for tires up to 2.1 diameter due to its narrower size.
I built my own wheels using DT 4.2d rims with DT 240 rear and Lefty front 32 hole 3 cross with Sapim CX Ray spokes and alloy nipples for just under 1500g. I can also run 2.3 tires if I want to on this combination. Another light and cool option would be the Industry Nine wheels using the DT Swiss rims. The Stans ZTR rims are super light, but they are a one season rim around here in the Arizona rocks, I have thought of a set with those rims as a race only wheel.
I saved the most weight running a set of Maxxis Exception tires converted tubeless with Stans. They sealed well at first, but I had problems with sidewall and tread holes due to the thin casings plus the beads must have stretched over time and they developed a permanent slow leak. I will save those for racing where rocks are not a problem.
Other areas of potential upgrade would be the handlebars to a carbon version probably save close to 100g. XT brakes are fairly heavy, switch to some Formula Puro or Magura Marta and save another 200g. Si SL crankset would save another 200+g over the carbon version. A carbon SL Lefty would save another 300g.
It all depends on how much you want to spend. Whether its worth it is up to you, I go through phases when I obsess over the weight of components, and then realize that my fitness not my bike weight is the deciding factor in my racing, but saving grams is fun (but expensive!) thats why I work at a bike shop.......
If you're planning to buy the bike now and brand new, the 2008 Rush Carbon 2 already comes with a good set of wheels, a XTR wheelset, that are pretty light, only 1520g and have wider rims than the SLR with the same weight, so you can hold up to 2.3 tires. Since most parts are XTR, you could complete the whole set by exchanging everything that's XT for XTR parts (shifters, cassette, front derailleur, chain and the crankset) and you'll save some good weight, not to mention you will make it a top model by having a full XTR set.
Originally Posted by david8613
You could also run tube tires, but that will depend on your preferences, since tires and tubes together may weight as much the same as tubeless tires. But there are some good options that may save you good 200-300g with light tire-tube combo. A good example are the Michelin XCR Xtrem 2.0 (575g each) with Michelin Light tubes (145g each). The XCRs grip like hell and the tubes are strong enough to hold lower pressures. But if you don't mind narrow and less grippy tires, you can always go with the Maxxis Ignitor 2.1 eXCeption Series (only 489g each, and are actually 1.9 wide) and run it with light tubes. Depending on your choices, you might get, with gear and tires, a good 500g off.
Anyway, if my choice was between better or lighter, I'd stick with better, so my choices are full XTR gear and the Michelin rolling set. You eventually get some grams more, but those are worthy grams, because you'll have top, highly functional gear and monster-bite-like grip and traction.