Spark Plus is a cool bike- But it is not the best tool for a 100 mile non-technical race with long climbs.
However, if you got the 700 Plus Tuned you could run 29er wheels on it and make it a lot faster- because it is a fairly light bike with high end parts.
That said, the OP was talking about a fat bike as an option- not a plus bike. A fat bike would be even slower yet.

1% up a 20 minute climb is only 12 seconds. I bet a bike with 2.8 Maxxis Rekon tires is more than 12 seconds slower than a race 29er.

I agree with most on here. I would choose the fs bike especially if you can lock it out. For me the suspension was just easier on my body over the long haul. Coming down columbine was not very technical but liked having the fs because a few places were pretty rocky in ruts and you don't really have an option to change lines because of people comming up. Not that you cant easily handle it with a hard tail but gave me more confidence to not get bumped over and hit somebody. I also liked it coming down powerline, It was really rutted last time I did it and was able to take much straighter line then a lot of others.

The problem isn't with the cranks but with the chainring. They "flip" the chainring to clear fat tires and I think you're limited to a 32t.

Actually, you can test the crr of MTB tires! http://www.bicyclerollingresistance.com/mtb-reviews

I think one of the reasons why people aren't running 650b+ tires in serious races is that, in order to make those tires have a somewhat reasonable weight, their build ends up making them somewhat fragile a prone to puncture.

sorry for the 3 month delay on this post... (my first post in nearly 2 years).

I've done this race 2x (2014, 2015) and doing it again this year (2017). First 2 times I did it on a Specialized Epic Expert FS 29er. Great bike for it. Considering an HT for this year. The race is hard. Shaving weight/rolling resistance is of marginal value. Sure it helps, but the reality is, can you ride 7-12 hrs up and down hills at 10k+ ft of altitude. That's the killer. The extra rolling resistance won't make a difference as you get light headed and dizzy climbing for 90 minutes to 12,500 feet at the turnaround.

In 2014, I went with the sworks tires. Got 3 flats. This is not a race to "go light" because a fast race tire, can be the end of your day (limped home in 10:19...).

Go as light and fast as you can but focus on you.

It's not highly technical, but the powerline descent (in the first 1/3 of the race) is pretty sketch. Otherwise it's all manageable. Now, while not technical, descending down Columbine on fireroad at 20-30mph for 7 miles isn't exactly easy. It's not single track DH hard, but it's tough to carry speed.

Leadville is all about altitude, climbing, and miles. I've done many tris, IM (once), and leadville is still the toughest day I've ever had.

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MyGearGarage - Track all your gear!

Thanks for input. Thoughts on 1x vs 2x for Leadville? 1x would be 1x12 Eagle. Looking at something with a little slacker head tube and longer wheelbase compared to my current true XC bike, as I am finding I don't enjoy it much riding everyday front rage stuff.

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Colorado Triathlon Company, CO2UT 2021, Crooked Gravel 2022, Steamboat Gravel 2022

I've never ridden a 1x at all, so I can't comment. But plenty of people do even at Leadville.

I'd compare the gearing ratios. There are some tough climbs out there when you are tired and having at least one very easy gear is useful.

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MyGearGarage - Track all your gear!

I rode this past year with a 2014 Cannondale Scalpel. Sram X0 drivetrain is 1x11. Enve m50 wheels.
I would recommend a 1x setup for simplicity.

I ran sram eagle last year at Leadville, and will do it again this year. Bike is s works epic. Great race.. you'll love it

I'd go with the lightest hardtail you can go with, this race IS about endurance & climbing (at altitude)

i grabbed a used 2012 Sworks (http://www.bikeradar.com/...er-29er-us-11-44799/)
article on the one Todd Wells used - http://www.cyclingnews.com/...ks-stumpjumper-29er/

can find these on ebay for a bargain, get one with the carbon rovals, bike weighs 19lbs.
get a pair of schwalbe racing ralphs, there is a lot of paved & dirt road riding on this course and they have the bite you need to grab the little rough stuff there is.

the actualy mileage you;d want FS for is around 9, small amount and you;ll be fine without it.

did the race last year, I was toasted early as I did it 3 weeks after IMLP..

get out early and acclimate if you can..

Fortunately I live in CO so acclimating won't be a problem, and will be going up to higher altitude to ride at least once a week. I love the idea of a hardtail for THIS race but as an all around bike in the front range its not ideal. Looking at as light as I can get for FS that is an XC/trail blend, maybe Orbea Occam or Scott Spark RC or Spark. Excited to get a new ride!

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Colorado Triathlon Company, CO2UT 2021, Crooked Gravel 2022, Steamboat Gravel 2022

I hear you on the front range stuff.. not sure what your budget is, I have 2 MTBs, my 29er hardtail for LV and any western XC riding I may get to do and then a nice 27.5er FS for technical trail riding.

the Sworks i mentioned above can be found for < $2500 if you poke around... can probably buy it, if LV is a one and done race and then flip it for close to what you are paying... If you want the lighest weight FS.. look at the Scott's I forget the model name, but they are stoopid light and have a handlebar mounted lock out for the front fork and I think you can reach down and hit the one on the Rear Suspension on the fly... can be handy for LV, unlock the rear for powerline... lock it back up when you hit the roads after that, unlock it when you stop at the aid station at the top of columbine, re-lock at twin lakes...

enjoy the race, truly an epic experience!

Thanks! Yes looking at the new Scott Sparks (RC version is sub 23lbs for not even the top model)... Leaning that way, budget not a huge issue. Looking forward to it, plus doing it with 4 good friends will make it all the more enjoyable of a weekend, while suffering at the same time!

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Colorado Triathlon Company, CO2UT 2021, Crooked Gravel 2022, Steamboat Gravel 2022

It's 65 miles of paved and unpaved time trial and 35 miles of climbing/descending on fire road, and a few short miles of singletrack. With that in mind, my set up is a 2x hardtail carbon 29er.

Crankset
Cadence matters on the long flats and steady climbs, and I've found the 2x to be well worth the marginal weight penalty.

Frame: hardtrail 29er
It's not a technical course so the extra weight of full-suspension is unnecessary. You should spend a majority of the race with the front locked out, too. the most technical descent is Powerline, and full-suspension wont save you if you get in trouble on that descent.

Tires: 29 x 2.0-2.2
Something tubleless, slightly over-inflated, with low rolling resistance. Specialized Fast Tracks or Schwalbe Racing Ralphs. 2.0 if you're going to recover time on the flats or climbs, 2.2 for better control on the descents if that's where you can recover time.

The guy ahead of me finished on a 1x fatbike, so obviously it's a matter of rider style and preference.

My set-up:
Frame: Niner Air RDO
Wheels: Stan's Crest
Tires: Schwalbe Racing Ralphs 29 x 2.0 tubeless
Front travel: 110mm
Crankset: 39-26t
Cassette: 11-36t

I ended up on a Yeti Turq ASR 2017 (full-suspension), with 1x12 SRAM (32T front), carbon Specialized wheels, and Schwalbe 29x2.25 front and 2.1 rear tires. Weighed in at 24.5#, size L. Bike never held me back, just starting in the very last wave did! Saw a few fat bikes out there too, and one of my friends did it on a fat bike running plus tires. Good times, thanks for your input!

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Colorado Triathlon Company, CO2UT 2021, Crooked Gravel 2022, Steamboat Gravel 2022

Hardtail carbon 29er with remote front lockout. I’d say tubeless is a must either way. If you have a hair up your hind end, drop bar 29er with flared drops.