Lefty and 650B for new build

[SpeedyChix]

If I was looking at 100 travel on a new build 650B frame, should I use a Lefty XLR 100 for 26" or 29" wheel?
Thanks.

[boots2000]

Speedy- what kind of frame?
Ask your builder?
FWIW- I would use one of the new Fox forks for 650b-

[Mads Kock]

From what I have seen a lefty for 26" will hit the front wheel fully compressed with a 650B wheel so you will have to use some kind of spacer to reduce the travel - not a big operation but needed! Don't think it will be the same with a 29" fork.

[SpeedyChix]

From what I have seen a lefty for 26" will hit the front wheel fully compressed with a 650B wheel so you will have to use some kind of spacer to reduce the travel - not a big operation but needed! Don't think it will be the same with a 29" fork.

Thanks!

[SpeedyChix]

Speedy- what kind of frame?
Ask your builder?
FWIW- I would use one of the new Fox forks for 650b-

singlspeed frame, will do but don't recall them doing much with the lefty (diff. than my usual mo)
Was leaning heavily toward the Fox fork as I have been happy with the one on the geared KE 27.5 (although that's a 26 fork)
Had read bad things re last year's CTD feature, enough that folks were sending in their forks for updated internals in the new forks.
Leaning toward Lefty as it knocks an easy pound off. Though I know you're not a Lefty fan.

[ricerocket]

All the 26" ones clear.

[SpeedyChix]

All the 26" ones clear.

If the 2013 100 travel 26" fork clears that's going to be the one.

Did they change the ability to add/remove spacers in the redesign?

[ricerocket]

Yes and no, from what I've read, you need the "full travel" to take advantage of the automatic bearing reset. Maybe you can put the spacer underneath the reset spacer?

I'd call Craig and MendonCycleSmith if you really want to run a spacer, he knows Leftys inside and out.

I haven't been very active on the 650b forums after I built mine, but iirc, everything up to the largest 650b x 2.35" Nobby Nic has cleared up since when I stopped reading 6 months ago. It "gets close", but since it's not like a fork arch like all other forks, it doesn't trap leaves/rocks/etc.

[Anders]

If you want to be safe do ad I did and buy the 29" which is the same as the Ultra with 120mm travel. You can always space it down to the same axel-crown height as the 100mm travel version and limit the travel to not hit the tyre.

[ricerocket]

Yeah, but that raises your BB, slackens your HTA, without giving you extra travel.

The 2013 Leftys also have different bearings on the 26 and 29 versions, I'm not sure it's as simple as spacing it down anymore.

[SpeedyChix]

Humm, this all has me leaning toward the new 27.5 Fox. After looking at weights, etc. there just isn't the huge difference their used to be.
edit: also found an interview with Cannondale tech, they say 29" fork to safely clear all 27.5 tires,

from the bikerumor interview

If you’re curious as to whether you could put a 650B wheel on this, Murray says you could put it on the 29er Lefty. On the 26″ model, you’d be cutting clearance really tight and it’s not recommended. They build in 20mm of clearance for a 26×2.3 tire at the top of the tire to the bottom of the lower fork clamp. That’s under full compression and deflection, so you’d have to hit something really hard, really fast and at an aggressive angle to get the tire that close, but on a 650B wheelset with a similarly fat tire, you’d risk hitting the tire on the “crown”.