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Front Fork Clearance?

Old 11-02-15, 07:37 PM
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Front Fork Clearance?

I just had a custom frame built and the clearance on the front fork seems unreasonably huge. I have 32mm tires, and have 1.5" clear vertically and .75" clear to the left and right. Thoughts?

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Old 11-03-15, 07:23 AM
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How much clearance at at the seatstays and chainstays?
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Old 11-03-15, 09:07 AM
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I'm running tires that measure just over 1.25" wide when mounted, and have almost exactly 1/2" clearance on each side, and 1" above the tire. This measurement is almost exactly the same in the rear, 1/2" between the chainstays, and 1" from the seattube. So you have 50% more clearance, which I wouldn't mind on mine, really. Just means you can throw some 2.25" tires on there and go mash.
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Old 11-03-15, 10:11 AM
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As a point of comparison, this is a pic of my fork with 700x33 tires:



I think you're good.
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Old 11-03-15, 10:25 AM
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fork: 3/4"
seatstays: 7/8"
chainstays: 1/4"

That chainstay clearance seems to throw off the theory of throwing on some wide tires and mashing, no?
I will add that this is my first non-road or track bike, so any "unnecessary" clearances look incredibly strange to me.
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Old 11-03-15, 10:30 AM
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Originally Posted by Andy_K View Post
As a point of comparison, this is a pic of my fork with 700x33 tires: I think you're good.
I'd tend to agree on a canti bike, where all that muck gets picked up and builds up at the fork area, but that's much less of an issue on a disc bike.
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Old 11-03-15, 10:35 AM
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After this year's Dirty Kanza 200, I don't think you can have too much tire+mud clearance. And my bike is a disc brake bike.

I rode 38mm tires on a fork with 50mm between the fork legs. The mud was so sticky that it would jam the front wheel in the time it took the contact patch to rotate around to the fork legs -- about 1/3 of a wheel revolution.
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Old 11-03-15, 10:58 AM
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Originally Posted by bowermb View Post
I'd tend to agree on a canti bike, where all that muck gets picked up and builds up at the fork area, but that's much less of an issue on a disc bike.
Obviously cantis make it much worse, but with the right mud the tire alone will pack on a lot of mud.

You clearly have a very generous amount of clearance, but that's probably not a bad thing. The main downside would seem to be the appearance with skinnier tires. The upside is mud clearance and the ability to use wider tires.
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Old 11-03-15, 12:52 PM
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Looks like plenty of room for a 40mm tire in front. Too bad the builder didn't give you similar clearance at the chainstays. Did you discuss tire clearance with the builder before the build and did he deliver what you asked for?
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Old 11-03-15, 01:04 PM
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Originally Posted by BluesDawg View Post
Looks like plenty of room for a 40mm tire in front. Too bad the builder didn't give you similar clearance at the chainstays. Did you discuss tire clearance with the builder before the build and did he deliver what you asked for?
Yep, I said I'd be using 32mm tires, so he could set that as the max for clearance. Doesn't seem like he paid any attention to that.
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Old 11-03-15, 01:54 PM
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Originally Posted by bowermb View Post
Yep, I said I'd be using 32mm tires, so he could set that as the max for clearance. Doesn't seem like he paid any attention to that.
I'd be pissed too. That's too big for a 32 max, especially since there's so much top clearance but not really that much side clearance.
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Old 11-03-15, 02:06 PM
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Originally Posted by bowermb View Post
I just had a custom frame built and the clearance on the front fork seems unreasonably huge. I have 32mm tires, and have 1.5" clear vertically and .75" clear to the left and right. Thoughts?

There's an appearance thing going on with the pic. The shot. with bottom bracket resting on the ground, doesn't really give the visual reference that the bike would were both wheels mounted and you shot the image again standing in the front.
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Old 11-03-15, 02:11 PM
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Originally Posted by cale View Post
There's an appearance thing going on with the pic. The shot. with bottom bracket resting on the ground, doesn't really give the visual reference that the bike would were both wheels mounted and you shot the image again standing in the front.
not sure what you're asking for, but the shot was taken with both wheels installed. there's some kind of optical illusion going on.
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Old 11-03-15, 02:13 PM
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Originally Posted by bowermb View Post
not sure what you're asking for, but the shot was taken with both wheels installed. there's some kind of optical illusion going on.
Okay, it looks like the front wheel is installed in a bare frame without rear wheel. I couldn't/can't see the rear wheel.
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Old 11-03-15, 02:20 PM
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you can see the shiny freehub at the top of the frame
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Old 11-03-15, 02:22 PM
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What he gave you was versitility and you will thank him later when you want to put some 43mm Rock&Roads in there (and you will). The only cost for the additional clearance is asthetics.
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Old 11-03-15, 02:24 PM
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Originally Posted by bowermb View Post
you can see the shiny freehub at the top of the frame
You see a freehub, I see a bright spot, could be a freehub, bikes is in the midst of a build... didn't see any tire. I was just pointing out that the perspective, appearance of abnormally large gap can change depending on how close you stand to the bike. I couldn't get a reference to go by from your shot. That's all.
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Old 11-03-15, 02:25 PM
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Ya versitility to run a 43mm tire in the front and a 32mm tire in the back. That's great.

: /
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Old 11-03-15, 02:48 PM
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Front clearance appears to be dictated by the decision to use a lugged crown on the fork. Builder used on the of the commercially available crowns (because casting a custom one would be prohibitively expensive) The vertical clearance could be related to having an axle-to-crown that works with the rest of the geometry. Or to have the same axle-to-crown as "common" cyclocross forks so the owner can replace it if they want to.

As a side note, 32mm max strikes me as a rather odd size limitation. 33mm I could understand if the OP wants to stick to cyclocross tires -which mostly come in 33mm or less because UCI. Not that a millimeter will make a huge difference, is just an odd tire size limit to me.
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Old 11-03-15, 02:51 PM
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Originally Posted by Spoonrobot View Post
Ya versitility to run a 43mm tire in the front and a 32mm tire in the back. That's great.

: /
Since the frame is unpainted a simple crimping of the chainstays will correct that.


Also, when building forks for cross, there are not that many fork crowns to choose from. Currently, most have around 50mm between the blades. Looks like he used this crown for straight blade. NOVA CYCLO-X FORK CROWN FULL SLOPE 28.6 7 OFFSET :: FORK CROWNS :: Nova Cycles Supply Inc.

hopefully he used the right blades for disk brakes.
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Old 11-03-15, 02:57 PM
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Originally Posted by Cynikal View Post
Since the frame is unpainted a simple crimping of the chainstays will correct that.


Also, when building forks for cross, there are not that many fork crowns to choose from. Currently, most have around 50mm between the blades. Looks like he used this crown for straight blade. NOVA CYCLO-X FORK CROWN FULL SLOPE 28.6 7 OFFSET :: FORK CROWNS :: Nova Cycles Supply Inc.

hopefully he used the right blades for disk brakes.
You can see the mount in the lower right corner. Haha
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Old 11-03-15, 11:30 PM
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Originally Posted by cale View Post
You can see the mount in the lower right corner. Haha
I meant the actual fork blades. Blades for disk brakes are thicker to fight the forces the brakes put on the forks. You won't be able to see that in the photo.
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Old 11-04-15, 12:10 AM
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Originally Posted by Cynikal View Post
I meant the actual fork blades. Blades for disk brakes are thicker to fight the forces the brakes put on the forks. You won't be able to see that in the photo.
How much stronger do sturdy steel forks have to get? Those look amply capable. Just my opinion.
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Old 11-04-15, 05:18 AM
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Originally Posted by Cynikal View Post
Also, when building forks for cross, there are not that many fork crowns to choose from. Currently, most have around 50mm between the blades.
+1

Less than 33c is essentially CX racing spec. Very few race bikes run steel forks, so demand for lugged crowns in those sizes is pretty near zero. My builder does unicrown forks to keep control of the spacing for people like me that still want a steel fork, but most buyers just opt for carbon forks even on steel frames.
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Old 11-04-15, 09:39 AM
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Originally Posted by cale View Post
How much stronger do sturdy steel forks have to get? Those look amply capable. Just my opinion.
Standard fork blades taper from around .9mm to .6mm where the disk blades are around 1.1mm wall thickness. Disk brakes shift the forces from the top of the crown to the blades so the thicker blades compensate for this.
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