RH Clark

My old Marlin 29er has had a non-working suspension fork for a couple years now. I don't need suspension for how I ride it and wish to drop as much weight as possible. It's disc brakes and a straight 1-1/8 steer tube. What dimensions and specs do I need to be able to buy a replacement fork? Aluminum or steel is fine. I'm OK with carbon but don't necessarily trust a cheap carbon as much as a cheap aluminum. Any suggestions or links would be greatly appreciated. Thanks.

curbtender

Search "29er suspension corrected rigid fork"

hokiefyd 

Your two primary specs are the steer tube size and configuration, which you already have locked in...and your axle-to-crown distance, or the distance from the centerline of the front hub axle to the crown race. This will allow you to choose a fork accordingly. You can size a fork to the full, uncompressed A-C length, you can size a fork to the compressed A-C length, or you can size a fork for anywhere in between.

My recommendation: because the A-C length of the new fork has the potential to change the geometry of the bike, try different lengths. You can do this by removing the springs from your current fork (I presume it's a simple coil spring fork) and replace them with hard dowel rods you can get from the hardware store. Cut them as desired to create different A-C lengths. You can then go out and ride and see how the different geometry feels to you. Changing the A-C length can/will change seat tube angle, effective top tube length, head tube angle, and trail, so plan this out and don't rush it. Figure out what A-C length you like best with your dowel rod experiment and then go searching for a matching fork.

Surly and Soma usually have a pretty good selection of steel forks and are available at a reasonable cost. I put a Surly ECR fork on a Redline MTB I have that came with a cheap spring fork and it rides great. I intentionally bought this fork as its A-C length was about midway between my spring fork's uncompressed length and compressed length.

Paul_P

Kona , Carver and Ritchey also sell forks.

I imagine a 29er suspension corrected fork must be a really long fork, around 500mm ATC or more ?
I just read somewhere about a frame builder that refused to warrant their frame if such of fork was installed.
Even a 26" suspension corrected is long.

maddog34

quit imagining.
the extra length required sets the steering angle to the same angle as if the fork was about 2/3 compressed, and the actual angle change from extended to compressed with a suspension fork is very small, a matter of a couple degrees for a 100mm travel fork.

i just did a similar swap two days ago... it changed the steering angle from 67(unloaded) to 69 degrees, which is great for a street stomper..
i removed a 120mm travel Marzocchi Bomber fork, and put in a standard rigid 26" fork.
road bikes typically have a 70 to 72 degree head angle... suspended MTBs have from 66 to 68, unloaded

Paul_P

Just today I received a Carver 26" suspension corrected fork, ATC 440mm, to replace a 100mm suspension fork with an ATC of 480mm. Had about 35mm of sag which brought me to 445mm. So the new fork is pretty close and shouldnt do anything to the geometry. To me, the fork 'looks' really long because the crown is so far away from the wheel. Not a problem, just a bit weird.

I just read that "a 100mm 29er fork has a 510mm ATC". Si if your 120mm Bomber was with a 29er, then it would be around 530mm ATC ? And would sag down to just below 500 ? Since the rigid fork is just replacing the suspended fork at about the same overall length, there shouldn't be any difference to the frame and I agree with you.

But I read earlier today at on the Soulcraft site :

"Note: Since 2010 we have not offered 29r suspension adjusted rigid forks, nor do we recommend using one on any new 29r frames we build. Doing so could void the warranty on the front triangle of your frame."

I wonder what could be different in forces on the frame between the two. Maybe because the suspension gives a bit instead of transferring all the force ? A long rigid fork must act as a pretty long lever on the short head tube area.

Darth Lefty 

Surly website still shows one version of Krampus fork for QR.

RH Clark

The Fork has been locked out for a while. I should be able to get an A-C length. Then I just make sure I get a 1-1/8 straight tube with enough tube above the headset for the height I have now?

maddog34

the "Soulcraft" statement is lawyer BS.

swapping ANY part could void ANY warranty.
putting KoolStop pads on your brakes would void the warranty, but would improve braking significantly, etc...
i've seen car companies try that with even Oil Filters... until someone mentioned the fact that that company's oil filters were made by Wix, and were not the higher end Wix filters.... oopys, huh?
turned out that following factory recs for oil change intervals and weights was what mattered the most... and using "thicker oil for more protection" is a bad idea... flow across critical bearing surfaces is reduced, increasing operating surface temps beyond the safe range for most oils....... burnt oil turns to a bi-product called "coke"... it's a form of rock.

maddog34

i'd look for a rigid fork with ample clearance for a big tire..... and, of course, ample steerer length

and 29" wheels are also 700c wheels, in Bead diameter terms... just in case you didn't already know that fact.