Rigid MTB fork sizing?

[Red Tornado]

Looking to swap a worn-out 80mm suspension fork for a rigid on my #2 dirt ride. 2011 Specialized Hardrock (15.5"). This bike has 26" wheels. Going back to my roots with this one.
I'm seeing a lot of "suspension corrected" forks with 453cm axle-crown measurement, but most refer to this as corrected for 100mm travel forks. Mine is 80mm.
I measured A-C on the existing 80mm fork, subtracted sag and came up with about 450cm. A 453 would be fine for riding in a straight line, but do I need to account for suspension movement when turning or riding over obstacles? I've seen a few rigid forks with a 431 A-C, would that be closer to a suspension corrected fork for 80mm?
Seems like a lot to have to account for: A-C minus sag AND ALSO minus a portion of travel. I guess tire size could even come into play, as I will be swapping a 2.1 for a 2.25 or 2.3 or 2.4 so increasing the tire sidewall height a little, too. Most likely will go with shorter knobs as I ride 90% of the time in dry conditions.
Am I over-analyzing this?
Do I need to consider some or all of the the above?
Would like to keep this simple, but on the flip side, don't want to get a rigid fork and have the bike's angles thrown off, either.
Advice/comments appreciated.

[Peter P.]

I'm wondering whether the forks you're looking at are for 29" wheels.

Vicious Cycles (http://viciouscycles.com/forks.php3) lists forks (presumably for suspension corrected frames) in the 425-438mm range for 26" wheels, which your bike has.

Salsa's Cromoto 26" fork (http://salsacycles.com/components/category/forks/cromoto_26_disc) measures 445mm and is a substitute for 100mm suspension forks. So I figure for substituting for an 80mm fork, subtract 20mm more. Therefore, a 425mm rigid fork would be a best fit replacement. If all you can get is the 431mm, then get that.

For comparison, my custom 26" rigid ATB frame has a 100mm suspension corrected fork and it's 440mm long which is still shorter than the 450mm you measure on your 80mm suspension fork.

[p nut]

Peter P - Susp. corrected 29er rigid forks are typically 470-490mm A/C. What he's looking at is right.

Red T - For something cheap, you can just go with a Surly fork. I've used a 1x1 fork in the past. Last year, I switched out a clapped out 80mm fork on my 99 Gary Fisher for a Surly Troll fork. It's 453mm A/C, 40mm offset. I wasn't sure how it would work with the Genesis geo, but it's been just fine. It slackened up the angles a little bit, so steerering is a tiiiiiny bit slower. If that bothers you, looks for something 425-440mm.

The great thing about the Troll fork: It has bottle mounts on the legs, and it can fit 26x3" tires, and 29er front wheel.

[PacNW2Ford]

My Independent Fabrication build sheet for a 26" wheel 80mm equivalent rigid fork says "430mm"

[Red Tornado]

Thanks all for the feedback. Did a little more research and looks like A-C being 430'ish is the way to go for 80mm susp-corrected rigid, as you said. I've found a few forks with this that I'm interested in.
It will replace a worn-out, very heavy SR Suntour fork that tops out very harsh & loud, plus is showing a lot of play between inner/outer legs. Guys at the shop say it is a 5+lb fork, so will be glad to get rid of it. Bike is a hand-me-down from my son who worked it pretty hard, but with a new fork, new disc brake pads and chain/cassette/rings will make a nice backup ride.

[kingpin75s]

Vicious Cycles (http://viciouscycles.com/forks.php3) lists forks (presumably for suspension corrected frames) in the 425-438mm range for 26" wheels, which your bike has.



I have a mint condition Vicious 26" 80mm suspension corrected fork with an a-c of 438mm for V-brakes if you are interested. Seems to be about what you are looking for. PM if interested.

[weisan]

Red pal, you doing this?
http://forums.thepaceline.net/showthread.php?t=162284

[Red Tornado]

Red pal, you doing this?
http://forums.thepaceline.net/showthread.php?t=162284

Not planning to do that ride. Believe I'm busy that weekend, and also just in the process of coming back from 6-months off the bike so form's nowhere as good as I'd like right now. Prob won't do a tour until May or thereabouts.

[Tin Turtle]

I used the Surly 1x1 on my Giant Roam to replace the crappy Suntour suspension fork and it worked VERY well. But that's a 700c bike. I measured axle to crown and just rolled the dice. Doing it again I would use a Troll fork because it has more mounts to hang stuff off of.

[unterhausen]

whatever the sagged a-c would be for your suspension fork is what you should use for a rigid fork. On an 80, you would subtract 20 from the un-sagged A-C measurement. That's what most framebuilders do.