Considerations when buying a new fork?

Hey all - wondering if some of the tech minded folks can help me out here?

For various reasons, I want to buy a new fork for my gravel bike … the main reason is I want to go from a 15x100 thru-axle in front to a 12x100. Other than the thru-axle size … I love the fit/feel of my bike.

What considerations do I need to make?
Is there any sort of an angle consideration?
Head tube/steerer tube compatibility?
If my current bike has post-mount brakes, is it ok if I buy a fork with a flat mount set up?

Is this a simple thing to do, and am I over-complicating it? Or is this a pain?

Thanks in advance for any thoughts.

Two key measurements are the Crown-to-Axle length and the fork rake (sometimes called offset). You’ll want to know what your current forks dimensions are and then compare to whatever forks youa re considering. Obviously you want them to match, unless you want to change how the bike handles. For example, you could go with a shorter rake, which would increase your trail and therefore increase the bike’s stability.

Also make sure you are buying the same steerer tube diameter…is your current bike a straight 1 1/8" or does it taper from 1 1/4" at the fork crown down to 1 1/8’ at the headset, etc.

There are adapters to adapt post-mount brakes to flat mounts, so you should have no problem there.


Oh, man … I knew this was going to be more complicated than I wanted it to be.

I’m good at buying bikes.
I’m good at riding bikes.
I can change a tire, but not as quickly as most.
I can swap pedals pretty well.

Everything else is a FAIL. Damn.

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Nah, it isn’t that hard…and people here will be more than happy to help if you have questions.

Your first step is to figure out the specs of your current fork. What bike are your riding now and what is the model name / year?

Here it is:

One thing you will notice on the specs is that it lists the front hub at 12x100. That is an error, it is 15x100.

Sorry, forgot to ask what size it is, too…

ETA - all the forks on that bike have the same Axle-to-Crown measurement: 385mm (very common). However, they do not list the rake / offset measurement on the geometry chart…and that usually does change by frame size. I would send an e-mail to Norco and just ask them what the rake / offset is for the size bike you have.

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Sounds like it might be worth a trip to your local bike shop and get their input on it. They should be able to identify the right fork for you, and possibly save you some expensive mistakes.

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