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I would like to convert a MTB frame to an XC bike for riding on former railroad tracks that have been converted to trails that present a mix of surfaces: fine gravel, dirt road with crushed stone, grass, poorly maintained broken and eroded concrete pavement, and long stretches of well-maintained macadam.

To that end, is there a 27.5" tapered-steerer suspension fork (disc mounts) with very short travel, perhaps only 25mm-50mm?

A rigid chromoly fork would probably do but I cannot find one that fits the frame without using a tapered-to-straight headtube adapter.

P.S. I'd prefer to avoid carbon, if possible.

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  • Similar forks are used on suspension hybrids so they should exist. The ones I've seen and rejected have had 60mm travel and little or no adjustment/lockout. I take all my bikes over such surfaces. In order of decreasing comfort they're: hardtail; steel tourer; aluminium hybrid, but even the latter is fine, so you might be able to get away with aluminium with no suspension
    – Chris H
    Dec 9 '20 at 15:15
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    Don’t rule out carbon. Especially forks are usually way over-engineered. I think pretty much the only failures have been with carbon steerer tubes and that’s more likely due to incorrect stem installation (too much torque on the screws).
    – Michael
    Dec 9 '20 at 18:00
  • Is there a fork already on the frame and if so does it have a lockout? On some suspension forks, the locked out position actually has a small amount of travel. You’re carrying a lot of extra weight (relative to rigid) that you don’t need, but it saves buying a new fork
    – Andrew
    Dec 10 '20 at 12:04
  • Lauf Grit is an unconventional design for gravel applications that has 30 mm of travel provided by glass fiber springs and requires no service. It costs about the same as other premium short travel forks mentioned in the answers and comments. Dec 10 '20 at 15:34
  • @Andrew: I have only the bare frame.
    – Tim
    Dec 10 '20 at 20:17
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It sounds like you don't really need a suspension fork. The surfaces and conditions you describe are what gravel bikes are designed for - those don't have suspension forks, they just rely on larger tire volume and lower pressure (compared to road bikes).

Short travel suspension forks do exist, but if your frame is designed for a longer travel fork the required axle-crown length will very likely be longer than that available on a short travel fork. (Obviously the for longer travel the frame head tube needs to be higher to give the wheel somewhere to go when the fork compresses.)

Short travel forks will also be lower end and therefore lack adjustment and will be heavy.

I'd go with a rigid fork if you can find one the correct length. Of course another option is selling the MTB and buying a (used possibly) gravel bike.

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    Not all short travel forks are low end now that the likes of Niner are making high-spec full suspension gravel bikes. Here's a 40 mm fork with a Fit4 damper (second best in Fox's range): ridefox.com/content.php?c=openproject
    – Paul H
    Dec 9 '20 at 16:18
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As I understand it the GVX is 27.5" compatible

https://www.srsuntour.us/products/gvx-700c?variant=32147701989470

It's 40mm/50mm/60mm with 45mm/46mm/47mm offset, which should be fine for 27.5"

I believe the NCX-E is 44mm offset with 50mm travel (NCX-D has steel stanchions for a bit more weight, as well as a cheaper coil option - the E is air)

https://www.srsuntour.com/products/fork/NCX-E-6268.html

Also fairly nice as such things go - air spring, alloy chassis.

If you hate money then you can spend more of it with an MRP Baxter

https://mrpbike.com/products/baxter

or a Fox AX

https://www.ridefox.com/family.php?m=bike&family=32ax

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  • Thanks for the suggestions. I hate to admit it, but I do love money. I'd love to be able to hate it.
    – Tim
    Dec 10 '20 at 20:14
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Essentially what you are after is a bike with good small bump compliance with no need for travel associated with MTBing. As the frame has a tapered steerer, you have a MTB designed for a fork of 100mm or more travel. The replacement fork will also need to maintain the headset height to maintain bike geometry.

MTB Plus size up to 3" would be ideal as this gives very good small bump compliance and completely adjustable for comfort and performance and have no amount of long travel. 3" tires are equivalent of about a 50mm fork. Put the fattest tire that will fit in the rear triangle. A rigid fork that can handle 3" tires allows you flexibilty with tire sizes. The rear probably won't fit the same width tire, so might as well make the bike a mullet with a 29er on the front (probably easier to find a fork that maintains original geometry.

Another option would be install spacers in the fork (in the existing fork if possible, otherwise anew fork) to give a more progressive spring. This means you can run pressures that give good small bump compliance, without traveling too much. It would give a better bike for the trails you discuss.

Gravel bike forks - such as the Lauf Grit Fork (not a recommendation) provide an alternate to a traditionally fork, combining more traditional tire sizes with low travel suspension. These options are all expensive - you would probably be better buying a gravel bike and selling the existing bike.

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  • I’m not so sure about a few of these suggestions. 1: Tapered steerers are commonplace on unsuspended road bikes too. 2: MTB plus size tires roll extremely slowly (likely unacceptable for a gravel build), and I’m not sure if you can get road tires in 3” sizes.
    – MaplePanda
    Dec 10 '20 at 1:16
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    OP said he is converting a MTB to XC. His question make no mention of Gravel bikes. Fast rolling 3" tires designed for hard pack are readily available, and while they may be a bit slower then a Gravel bike, are arguably more suitable to the intended task than gravel tires with suspension fork, especially given a fork will cost north of $1000.
    – mattnz
    Dec 10 '20 at 3:25
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    As far as rolling resistance - you may be interested in bicyclerollingresistance.com/mtb-reviews - Gravel tires seem to be between 20 and 33W where as 2.2-2.3" MTB sit between 13W and 40W. 3" will probably be a bit more than 2.3", but if the OP wants to change tire size, it cheap and easy (within limits of the rim size).
    – mattnz
    Dec 10 '20 at 3:35

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