nicolaim

I have a '97 Trek 8000 with Rock Shox Indy SL (elastomer, 63 mm travel.) The bike is still doing great, but I'd like to upgrade to a more sophisticated (but still lightweight) suspension fork (for XC riding.) I'm hoping someone can give me some idea of which fork models (likely older ones) would fit this bike without greatly altering the geometry/handling. Most forks have dropouts forward of the midline and fork legs forward of the steerer midline, whereas mine are all close to in-line, so I'm worried that alone will mess things up.

LarDasse74

I have no advice to offer as to specific models of fork. You should know that the manufacturers do not really offer replacement parts for forks more than a couple years old - for this reason I would avoid buying a fork older than last years model (except for a rigid fork, which is always an option, and still likely an improvement over an indy*)

You concern about the geometry of the fork (placement of the dropout relative to the fork legs) is unnecessary. The "rake" measurement is the distance between the axle and an imaginary line drawn down the steeing axis of the frame (the head tube angle). On many older forks (like the indys) the rake is accomplished by having the legs leave the crown at an angle ahead of the stering axis, and the droputs are at the bottom of the legs. Most newer forks have the legs running paralell to the steering axis and accomplish rake by placing the dropouts forward of the lower part of the legs. If the distance in front of the steering axis is the same, it does not matter which of these methods is used - the fork will work without any major change to handling.

Luckily, the rake on most mtb forks is within a very narrow range, so just about any fork of roughly similar length will work on just about any bike without a major change in handling. So if you get a modern fork designed for 80mm of travel (only 17mm more than your current fork) it will work fine.

*An anecdote about RS Indy forks:

Back in the mid/late '90s I was riding with a friend in Whistler BC. I had been working in a bike shop in Ontario and was thinking about buying a new GT bike with an Indy XC fork. I saw a young woman on a mid level bike with an indy fork riding out of one trail that emptied out into a ~2 foot deep ditch on the side of the road. As I watched her approach the ditch I remember noticing how spindly and puny the Indy fork looked, and though to myself that she might have trouble making it through the ditch. Lo and behold, she got to the ditch and the skinny little legs on the fork visibly twisted and catapaulted her over the ditch onto the road.
I still bought the GT, but I replaced the Indy with a different fork before I ever rode it.

nicolaim

I always knew the Indy was the bike's weakest part, but since the bike was already over my budget, swapping out the fork at the beginning wasn't an option. A few years later I was going to buy a SID, but the seller disappeared. Perhaps that was for the best because I didn't ride the bike much for some time. I'm actually surprised how well the fork is doing considering how old the elastomers are. I wish I hadn't missed out on the Englund Total Air cartridges, which would have been a relatively inexpensive way to upgrade the fork, but I now have my eye on a cheap SID from a local buyer, as well as a possible Fox on eBay. The rake/offset on my fork is definitely less than other models, even with the angled fork legs, but the slightly increased height of a new fork should partly compensate for the additional offset.

LarDasse74

I googled "Rockshox Indy Rake" and found a few sites reporting 1.6" (40.6mm).
Then I looked at the Trek website and found the geometry for the current Trek 8000, and the RS Reba SL is listed as having a rake of 4.0 cm (40mm).

A bike on the felt website listed a fox fork as having a rake of 39mm.

It is very very unlikely you will notice a small difference like that.