Originally Posted by
Wilfred Laurier
As above, look up the calculation of the dimension 'trail'. If the 'trail' is changed significantly, the handling will change significantly. For this calculation you need to know the head angle of your bike and the length and 'rake' of the fork.
Generally speaking, a shorter fork will make the head tube angle steeper and this will reduce trail, making the bike quicker handling/less stable. If the shorter fork has less rake then this will lessen the effect of the steeper head angle.
My gut feeling is that a 20mm shorter fork with similar rake will noticeably change the handling of the bike. It might be perfectly acceptable, or it might not.
You don’t need to look at the trail numbers to realize that dropping your front end by 2 cm will make your bike feel different. Doesn’t matter if the trail is exactly the same. You’re really changing the relationship of your body position to the behavior of the bike at this point. That’s not necessarily bad, maybe you’d prefer how it feels with the shorter fork.. If you’re happy with the fit and handling as-is and want them to remain the same, go with the fork that’s closer in length to the current one. If you want some surprise and excitement, go for the shorter fork.