MTB to Tourer Fork Geometry

Hi there,

Currently building a new tourer from orphaned bike parts since getting my previous one nicked. I'm starting with an old Raleigh Summit which came with some early 1992 Rockshox forks, which I plan to swap for rigid touring forks.

When the Rockshox are fully extended they measure axle-to-cown 400mm, so currently I'm looking at the Surly Long Haul Truckers which measure 376mm and the Thorn Mt Turas which measure 430mm.

My understanding is that when ridden on flats, those Rockshox would probably have been compressed to somewhere closer to the LHT's measurement, but I'm wary of shortening the fork length because touchier handling and a crank closer to the ground and / or panniers wouldn't be ideal.

Conversely I'm worried that adding 50mm or so of length (if I'm correct about the compression) to the geometry by using the Thorn Tura's could be quite drastic and alter the ride.

What is the thinking here? Is it better to decrease the head tube angle than risk increasing it?

Look for a 400mm fork!

My understanding is that when ridden on flats, those Rockshox would probably have been compressed to somewhere closer to the LHT's measurement, but I'm wary of shortening the fork length because touchier handling and a crank closer to the ground and / or panniers wouldn't be ideal.

You're referring to sag which would mean that yes, while being ridden the a2c of the rockshox fork would be <400mm.

I'd not be entirely convinced that the bike's design would have considered sag though, ie headtube angle etc was probably set for a2c of 400mm so you should probably - as Skully suggests - look for a 400mm fork.