I am surprised about the lefty....
It is only a 120grams less than my Reba(1658 inc. axle and starnut)
If you weigh just the fork leftys seems light, but
Cannondale 2012 Lefty OPI Alloy XLR 29er 90mm 1,523g
Hose Guides 15g
Cannondale Lefty-4-All 11/8" Steerer KH075 212g
= 1750g
However, worth it for looking so cool
Also, are you pretty happy with the Formula R1's?
What year are yours? Older ones seem to be tight clearance.
XT's have been popular here so interested in how your R1 install went?
They're 2012 R1s, they definitely work but unfortunately on a week long bike packing trip they decided not to stop working and the front brake was dragging for most of the trip, but given I'd already snapped the rear mech off so was riding a field modified single speed that was the least of my concerns. I do sometimes get a bit of vibration through the front brake, not sure if it's a warped or too lightweight a rotor or just a terribly built front wheel (it was my first attempt).
I'm no sciencetician but I'm pretty sure this isn't right
This picture was at about 9pm just after I checked my tool bag and discovered I'd left the spare mech hanger at home. Pushed it to the top of a 600m climb and freewheeled as far as I could in the aerobars then my mates pushed me to a campsite.