I am building up a 2013 Trek Stache frame (HT) and looking at suspension forks. The bike came from the factory with 120mm of travel. I can get a 120mm for 470 or a 140mm fork for 400. Since the frame was designed with a 120mm fork. If I go with the 140mm fork, how much of an effect in steering should I expect?

Thanks

EDIT: I understand increasing travel with increase head angle. But is increasing the travel 20mm going to make a substantial change? I’m really new to building frames and aftermarket part so I am hoping to get advice from someone with experience on the matter.

It depends on the axle to crown length difference of the new fork. The longer it is the slacker the head angle, so all the changes that brings. I’ve always worked on 10mm = roughly 1 degree, rightly or wrongly.

What are you trying to achieve?