How do I figure out if this fork will work on my current bike?
Define “fit”…as long as the steerer tube is the right diameter, it will technically “fit”.
I think the question you are really asking is “will it impact the geometry / handling of the bike”, in which case you need to compare the offset and axle-to-crown measurements of both forks.
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Yes, you are correct. I am trying to understand how much the geometry and handling will change. My current fork has a rake of 55mm and axle-to-crown of 395. The Lauf has a rake of 47 mm and axle-to-crown of 419 including 6 mm sag (fork has 30 mm of travel). According to Lauf: “Grit 3rd gen maintains the steering characteristics of a rigid fork with 45mm rake and 405mm axle to crown.”
I don’t need new geometry to be exact, just not too far off. Thanks
So the increased axle-to-crown length will slacken your head tube angle slightly. I lack the geometric skills to tell you what the new HTA angle would be, but I’m sure someone can figure that out (or find a tool online).
Once you have the new HTA, use the below calculator to determine what your new trail will be.
http://yojimg.net/bike/web_tools/trailcalc.php
After you have the new HTA and revised trail numbers, you’ll have a better idea of how the fork change will impact the handling of your bike.
Taller fork will slacken both HTA and STA by about a degree. This would mean you’ll need to move your saddle forward on its rails 1-1.5cm to maintain the same saddle setback relative to BB, depending on your saddle height. You would obviously also need to drop your stem 20mm or so to maintain your current saddle-bar drop, if you want to do that.
You also need to check that the lower headset bearing for the Lauf is compatible with your frame, or else get a compatible bearing. I believe Lauf provides a bearing with the fork, but you need to check diameter and race angle will fit your frame.
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Good point re: the bearings.
Still considering this option and I greatly appreciate the information. I think my main concern is how much my bottom bracket height will increase with a longer fork and bigger wheels. My descending skills are not that great
Most of the increase in BB height will probably come from the larger tires you’ll be running. Because the BB is closer to the rear dropout than the front, the fork change would probably only raise your BB ~5-6mm if tires are the same.
Going from 38mm slicks to 57mm fatties on my Lauf I definitely notice the increased overall height of the bike. However, I find that I get used to this quickly, and the drastically more forgiving and smooth ride provided by the larger tires totally outweighs any effects of geometry in terms of confidence and grip at speed.
As someone well-known for advocating for lower BB heights in gravel bikes, I wouldn’t worry too much about it. Any gain in BB height will be more than offset by the control you’ll gain form the larger tires and suspension. You will still get a better descending bike, IMO.