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Fork length for custom frame?

Old 08-12-20, 05:30 AM
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deepakvrao
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Fork length for custom frame?

Hi Guys,Question regarding forks.

I see that rim brake forks are usually 370mm, and disc brake forks start at 370 and go upto 400mm, from axle to crown. Am I correct? At least my rim bike fork is 370, and my Canyon Endurace fork is 390.

So, I suppose you need to know what fork you are planning to use beforehand if one is doing a custom frame?

Suggestions for a disc brake fork that is 390mm?

Last edited by deepakvrao; 08-12-20 at 05:51 AM.
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Old 08-12-20, 06:01 AM
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Originally Posted by deepakvrao View Post
So, I suppose you need to know what fork you are planning to use beforehand if one is doing a custom frame?
Yes, the frame needs to be designed around a particular fork length, +/- a few mm, because changing ATC affects head tube and seat tube angles, stack height, etc. A rule of thumb is that every 10mm change in ATC, you affect seat and head tube angles by a half-degree. If you take a bike designed around an ATC of 370 and put a 395 fork in it, the steering will likely get noticeably more floppy and slow. This probably would be a bad thing.

Design around an ATC that befits the type of fork you want to use. You are correct about road forks for rim brakes being around 370-ish. It seems to me that a lot of cross disc forks are around 395, although I have seen some as high as 410 (but those are atypical). Not sure about endurance road disc - maybe they are a little shorter, say 390 like you mentioned. I have only shopped for cross disc brake and road rim brake forks in recent years.
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Old 08-12-20, 08:01 AM
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Originally Posted by Steamer View Post
Yes, the frame needs to be designed around a particular fork length, +/- a few mm, because changing ATC affects head tube and seat tube angles, stack height, etc. A rule of thumb is that every 10mm change in ATC, you affect seat and head tube angles by a half-degree. If you take a bike designed around an ATC of 370 and put a 395 fork in it, the steering will likely get noticeably more floppy and slow. This probably would be a bad thing.

Design around an ATC that befits the type of fork you want to use. You are correct about road forks for rim brakes being around 370-ish. It seems to me that a lot of cross disc forks are around 395, although I have seen some as high as 410 (but those are atypical). Not sure about endurance road disc - maybe they are a little shorter, say 390 like you mentioned. I have only shopped for cross disc brake and road rim brake forks in recent years.

Thanks. Any suggestions for a 390 fork which will accommodate say 32mm tyres? My frame builder gets columbus forks, but I dont think they have a concealed routing for the disc hose.
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Old 08-12-20, 10:25 AM
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Originally Posted by deepakvrao View Post
Thanks. Any suggestions for a 390 fork which will accommodate say 32mm tyres? My frame builder gets columbus forks, but I dont think they have a concealed routing for the disc hose.
Nope. As I said, I've never shopped for a fork that length.
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Old 08-12-20, 07:09 PM
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Thanks guys. My frame builder says he gets Columbus, and though the pics did not show it, they do have the internal routing on the left leg.
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Old 08-12-20, 08:46 PM
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Curious who is building this. Not trying to be critical, but I'd figure this is something the builder would know and address.
But really, I'm curious because you are a bit of a world traveler so it'd be neat to see where/who you chose.
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Old 08-12-20, 09:38 PM
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Originally Posted by mstateglfr View Post
Curious who is building this. Not trying to be critical, but I'd figure this is something the builder would know and address.
But really, I'm curious because you are a bit of a world traveler so it'd be neat to see where/who you chose.
Well, no travel in the foreseeable future :-( , so, looking at a local builder in India. He has done a few steel bikes for friends, and has done a really good job. Yes, he did address the issue, but I had posted this before I had spoken to him. He said he would supply the fork, headset and the frame. Of course, he would charge extra for that, but said that he would design the bike after we had decided on the fork.

This is what I have selected.

https://ciclicorsa.com/shop/columbus...vel-disc-fork/
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Old 08-12-20, 10:02 PM
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Originally Posted by deepakvrao View Post
Well, no travel in the foreseeable future :-( , so, looking at a local builder in India. He has done a few steel bikes for friends, and has done a really good job. Yes, he did address the issue, but I had posted this before I had spoken to him. He said he would supply the fork, headset and the frame. Of course, he would charge extra for that, but said that he would design the bike after we had decided on the fork.

This is what I have selected.

https://ciclicorsa.com/shop/columbus...vel-disc-fork/
Very neat- this is something you have to post about once complete as a handmade bike from India isn't exactly commonly shown.

The Columbua Futura fork is what All City is currently using for some of their drop bar CX and gravel bikes. This past year, for some reason they went away from using a sister company's carbon fork and chose the Futura.
its a neat blade design from the side profile.
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