Fork travel ties back to the frame design right? On modern bikes front center (fork to bottom bracket) on a 170mm will be longer than a 140/150mm forked bike. This give you the buffer to run a larger tire without hitting the downtube when compressed.
So you saying I can run a 29x3 on a 100mm XC bike if the fork allows clearance? We know it will not work. Frame likely has more upright headtube which gives a smaller front/center. Even if you slap on a 150mm fork on the XC bike, you still have a the same problem.
See below. E is the key. Why a bike designed around 160, 170, 180mm likely be OK because it has a longer front/center and YMMV on 150mm. And ive tried 29x3 on my 130mm (overforked to 140mm) and was hitting the downtube.
Respectfully, I find this misguided at best. Certainly misleading.
I have a 100mm fork on a 69.5deg head angle bike with a 450mm reach (size XL) -- in other words, a very short front center by contemporary standards -- and a 29x3 tire doesn't come within 2cm of the downtube when fork bottoms out. The tire
will hit the crown of that fork, however. I also have a Salsa Timberjack (68deg head angle, 471mm reach) with a 120mm fork (the rare '17 Fox 29/27.5+ model with wide stanchion spacing) which has plenty of clearance to the downtube and I can run virtually any 29x3 tire with zero issues for frame or fork.
Does frame design matter? Yes, the shape and orientation of downtubes can certainly create more or less clearance. But generalizing those shape/placement factors solely to frames intended for 160mm+ forks and their associated front center figures is grossly misleading.
On the same frame, a 140mm Lyrik will produce a different front-center value than a 180mm Lyrik (due to slight decrease in wheelbase as a result of reduced head angle). But the clearance to downtube on that frame at bottom-out will be
identical for both forks.
Fork manufacturers sometimes publish maximum tire size, and when they do, there is NO asterisk regarding the frame. None. Its typically a clearance-to-underside-of-crown issue, though sometimes its a clearance-to-side-of-arch issue. Industry standard min clearance is 4mm I think.
I'm not sure what was happening with your 130mm bike, but I'd bet the downtube position/shape is an outlier.
If RS doesn't publish tire size for Lyriks, my suggestion to
@noapathy would be to measure the gap to crown with his current tires and fork bottomed out. Then decide if you can tolerate that gap shrinking by the amount your tire outer diameter will grow. Given the variation in tire specs vs realworld size, you may not get a definitive answer, but it will surely get you a yes/no/maybe.
