Changing Fork offset

So I have a Trek pro-caliber with some 100mm RockShox Recon on it with a 42mm Offset.

Merlin have these at a bargain price: https://www.merlincycles.com/fox-32-rhythm-float-grip-boost-mtb-forks-29-280579.html

However offset is the more standard 51mm…….

Will it ruin the handling?  Is my frame specifically set up for the shorter offset? I can’t believe it is…..

frames can’t be set up for one or the other, but offset interacts with wheel size and head angle to provide a certain feel. it’ll marignally improve handling at higher speeds and marginally worsen handling at lower speeds

Your new fork will move the axle 9mm further forward so 9mm longer wheel base but weight distribution will shift slightly backwards. I doubt it will make much difference on a XC bike.

it’ll marignally improve handling at higher speeds and marginally worsen handling at lower speeds

How does longer offset, which is to say shorter trail, make that so? I think it is opposite, in theory.

Not mtb but my gravel bike has flip chip in front forks to adjust offset by 5mm.

I have longer, open gravel routes near me as opposed to tight, twisty stuff so run the fork in longer Offset mode. It’s barely perceptible but the bike does feel slightly more stable at high speeds compared to the reduced Offset setting. There really isn’t much in it though.

How does longer offset, which is to say shorter trail, make that so? I think it is opposite, in theory.

ah you’re right i got things backwards

Erm I’m confusedederer now – a longer offset gives a shorter trail?  I thought a longer offset would give a longer wheelbase? Or is trail different to wheelbase?

https://bikeinsights.com/cyclopedia/trail

I put that exact fork on my Xcaliber which came with a 42mm offset fork. It made the handling rather twitchy, as the increase in offset reduces the trail so much it feels like a 1.5 degree steeping of the head angle (according to this link https://www.fanatikbike.com/blogs/engage/who-the-heck-cares-about-fork-offset-and-what-the-heck-is-trail).

Great fun when using the bike on easier trails and if you are using the caliber for more gravel oriented stuff, but it exacerbates the already steep head angle compared to modern XC MTBs.

Yeah well in that case I’ll pass – thanks that’s really useful. I already feel its a bit twitchy.

You probably won’t notice the difference.