Rigid fork upgrade
12-20-24 | 10:18 AM
#1
Thread Starter
Newbie
Joined: Jan 2021
Posts: 25
Likes: 1
From: Ohio
Bikes: Cannondale r500, Mongoose Hybrid
Rigid fork upgrade
I have a sun tour xct 100mm 27.5” suspension fork that I would like to upgrade to a rigid fork. Says my axle to crown for the suspension fork is 497mm. Finding a straight steer fork in that length is challenging. I have found several forks with axle to crown of 470mm. I’m primarily going to gravel ride. Will 470mm allow for comfortable riding? Thank you
12-20-24 | 10:54 AM
#3
Thread Starter
Newbie
Joined: Jan 2021
Posts: 25
Likes: 1
From: Ohio
Bikes: Cannondale r500, Mongoose Hybrid
12-20-24 | 11:35 AM
#4
Senior Member
Joined: Apr 2009
Posts: 39,897
Likes: 3,865
From: New Rochelle, NY
Bikes: too many bikes from 1967 10s (5x2)Frejus to a Sumitomo Ti/Chorus aluminum 10s (10x2), plus one non-susp mtn bike I use as my commuter
Before sweating details, get the correct axle to crown measurement.
Measure the fork yourself with the bike leaning on the wall.
Next account for sag by wrapping a pipe cleaner, cable tie, or similar around the stanchion, then sitting on the bike. Sag will push the wrap up and it will stay there. Get off, measure how far it moved, and subtract that from the unloaded length to get the sagged length.
Once you know the sagged length, you can make smart decisions regarding the replacement. IMO dropping an inch or less probably won't cause issues, especially if the rake is increased. However, combining drop with reduced rake may cause some handling issues. On the bright side, gravel riding is less sensitive to steering issues than on the road.
Measure the fork yourself with the bike leaning on the wall.
Next account for sag by wrapping a pipe cleaner, cable tie, or similar around the stanchion, then sitting on the bike. Sag will push the wrap up and it will stay there. Get off, measure how far it moved, and subtract that from the unloaded length to get the sagged length.
Once you know the sagged length, you can make smart decisions regarding the replacement. IMO dropping an inch or less probably won't cause issues, especially if the rake is increased. However, combining drop with reduced rake may cause some handling issues. On the bright side, gravel riding is less sensitive to steering issues than on the road.
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Chain-L site
An ounce of diagnosis is worth a pound of cure.
Just because I'm tired of arguing, doesn't mean you're right.
“One accurate measurement is worth a thousand expert opinions” - Adm Grace Murray Hopper - USN
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FB
Chain-L site
An ounce of diagnosis is worth a pound of cure.
Just because I'm tired of arguing, doesn't mean you're right.
“One accurate measurement is worth a thousand expert opinions” - Adm Grace Murray Hopper - USN
WARNING, I'm from New York. Thin skinned people should maintain safe distance.
12-20-24 | 11:48 AM
#5
Senior Member
Joined: Jul 2015
Posts: 7,381
Likes: 3,223
From: NW Oregon
Bikes: 1982 Trek 930R Custom, '91 Diamondback Ascent w/ XT, XTR updates, Fuji Team Pro CF road flyer, Specialized Sirrus Gravel Convert, '09 Comencal Meta 5.5 XC, '02 Marin MBX500, '84 Gitane Criterium bike
a 470mm fork will fit fine... i've done a few such conversions... 27mm is a bit over an inch. and that approximates the fork when it compresses as you sit on the bike, if it was set up with the correct preload, or "sag".
your bike will be two to three pounds lighter, and you will waste less energy on fork bouncing when you pedal.
your bike will be two to three pounds lighter, and you will waste less energy on fork bouncing when you pedal.
Last edited by maddog34; 12-21-24 at 03:56 PM.
