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Why wouldn’t this suspension fork work?

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Why wouldn’t this suspension fork work?

Old 10-31-19, 06:25 PM
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digger
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Why wouldn’t this suspension fork work?

I’ve been kicking around the internet trying to find a suspension fork for a 9mm QR front wheel.
I found one here, but they say that for tires over 4.5 inches, it may not fit; depends on the tire.
https://boltonebikes.com/collections...uspension-fork

I have a Rocky Mountain Blizzard -20. Maxxis Minnion 4.8” tires on 100mm rims, it’s a 9mm QR thus a 135mm hub.
I measured the tire width at 8psi to be 120mm (4.72”). I placed the wheel in the floor and measured from the floor to the top of the tire (a straight edge laying on top of the tire).

What I don’t understand is, if the tire is 120mm wide and the hub is 135mm, thus the dropouts and the fork sliders are 135mm wide, then why wouldn’t those tires work in that fork? That’s 7-8mm between the fork slider and the side of the tire.
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Old 10-31-19, 08:30 PM
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Originally Posted by digger View Post
I’ve been kicking around the internet trying to find a suspension fork for a 9mm QR front wheel.
I found one here, but they say that for tires over 4.5 inches, it may not fit; depends on the tire.
https://boltonebikes.com/collections...uspension-fork

I have a Rocky Mountain Blizzard -20. Maxxis Minnion 4.8” tires on 100mm rims, it’s a 9mm QR thus a 135mm hub.
I measured the tire width at 8psi to be 120mm (4.72”). I placed the wheel in the floor and measured from the floor to the top of the tire (a straight edge laying on top of the tire).

What I don’t understand is, if the tire is 120mm wide and the hub is 135mm, thus the dropouts and the fork sliders are 135mm wide, then why wouldn’t those tires work in that fork? That’s 7-8mm between the fork slider and the side of the tire.
Do the legs of the fork taper inward as they approach the top of the fork?

Cheers
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Old 11-01-19, 03:23 AM
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Originally Posted by Miele Man View Post
Do the legs of the fork taper inward as they approach the top of the fork?

Cheers
Taper, no. But MAYBE the slider increases in diameter right at the top where the fork arch begins.
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Old 11-01-19, 06:27 AM
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Most of the fatbike forks are 150 thru axle. Which hub do you have? It may be convertible to 150, which would give you a lot more fork options. As for the tire, it might clear the sides but what about the bridge when compressed? For riding in snow, you're going to want some more clearance to clear the snow packed on your tire.
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Old 11-01-19, 07:15 AM
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Originally Posted by qclabrat View Post
Most of the fatbike forks are 150 thru axle. Which hub do you have? It may be convertible to 150, which would give you a lot more fork options. As for the tire, it might clear the sides but what about the bridge when compressed? For riding in snow, you're going to want some more clearance to clear the snow packed on your tire.
As mentioned I have 135mm hubs using 9mm QR. When you say "convertible" you mean switching out the 135mm hub for a 150mm thru-axle, correct? That's in the back of my mind also.

Snow pack is something I did not consider, thank you. When the fork compresses the wheel doesn't get closer to the bridge, the bridge is attached to the sliders and thus moves with the sliders.
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Old 11-08-19, 06:27 PM
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Couple things:

First, the dropout width is not indicative of the distance between the legs of the lowers, or of the width of the opening at the arch where the tire is. Take a look at this pic of a QR fork (this is not a fat fork, but the point is the same):




The QR dropouts are ~100mm apart. But the distance between the legs is slightly less. But more importantly, up at the top where the tire is, it is about 80mm wide. The arch is shaped the way ot is in order to make it stiffer.

Second, the issue is often not the width of the tire, but the height of it. Too big and it hits the top of the arch.
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Old 11-12-19, 12:05 PM
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Originally Posted by digger View Post
As mentioned I have 135mm hubs using 9mm QR. When you say "convertible" you mean switching out the 135mm hub for a 150mm thru-axle, correct? That's in the back of my mind also.

Snow pack is something I did not consider, thank you. When the fork compresses the wheel doesn't get closer to the bridge, the bridge is attached to the sliders and thus moves with the sliders.
yes, some better range hubs are convertible. It's not cheap $50-100 but will open up options
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