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Singlespeed & Fixed Gear "I still feel that variable gears are only for people over forty-five. Isn't it better to triumph by the strength of your muscles than by the artifice of a derailer? We are getting soft...As for me, give me a fixed gear!"-- Henri Desgrange (31 January 1865 - 16 August 1940)

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Old 03-15-09, 05:40 PM   #1
supercub
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Yet another fork rake question

I'm in the market for a carbon fork. Stock fork has a 40mm rake, and I pretty much like the handling.

I'm looking at the Alpha Q CS10. It's decently priced and looks to be durable. It's kind of ugly, but i like kind of ugly stuff. The problem is that it has a 44mm rake. Will this significantly change handling properties. I've heard a few mm doesn't have much affect, but 4 mm might be pushing it. Will my bike loose its crisp handling?

Along the same lines, does anyone have a recommendation for a carbon fork with alloy or steel steerer in the $200 range. Around 40mm rake and 1 1/8.

Thanks!
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Old 03-15-09, 05:50 PM   #2
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If you like the handling your bike has now, I'd try to get something closer to being identical to your current setup. That said, 4mm of difference isn't a HUGE different.

Also, an essential measurement to take into consideration is the axle-to-crown length, as it will also change the handling. For instance, take a fork with a rake of 40 and an axle-to-crown length of 175cm. If you change to a fork with a rake of 44 and an axle-to-crown length of 168, it actually might feel around the same because the trail might be similar (I am of course just pulling numbers out of the air, so this won't be precise at all). You could do a simple geometry calculation if you have the head tube angle, as well. I have been told that an alright rule of thumb regarding forks indicates that for every 10mm of axle-to-crown length, the head tube angle changes by about a degree.
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Old 03-15-09, 08:21 PM   #3
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if you plan to spend 200usd and have some patience, you can likely score a new full carbon fork on ebay with the specs you want. look at reynolds ouzo pros, eastons, and columbus.

that said, adding 4mm to rake will slightly decrease your trail, making your bike less stable. it's arguable whether that makes it 'twitchy' or 'agile'.
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Old 03-15-09, 08:48 PM   #4
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***anectdotal evidence warning***
Assuming the same axle to crown height, you won't notice a 4mm change in rake.
I used to wonder about these things, so awhile back I made four fixed frames with minor geometry changes in each one and four forks with 30- 60 mm rakes. Among other things, I found that a 10mm rake change was noticeable, but anything less wasn't.
FWIW, I found the forks with higher rakes to be preferable for fixed riding.

Good luck in your search.
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Old 03-15-09, 09:49 PM   #5
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Thanks for everyone's input. Figuring out trail is kind of interesting. I had no idea that a fork is so integral to the handling of the bike.

Regarding the axle to crown length; the stock fork is about 381mm (with 40mm rake) and the Alpha-Q is 371mm (with 44mm rake). Assuming I'm getting this right, the difference in rake is somewhat offset (no pun intended) by the shorter length of the Alpha-Q blades. Is that right?
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Old 03-16-09, 06:36 AM   #6
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Originally Posted by supercub View Post
Thanks for everyone's input. Figuring out trail is kind of interesting. I had no idea that a fork is so integral to the handling of the bike.

Regarding the axle to crown length; the stock fork is about 381mm (with 40mm rake) and the Alpha-Q is 371mm (with 44mm rake). Assuming I'm getting this right, the difference in rake is somewhat offset (no pun intended) by the shorter length of the Alpha-Q blades. Is that right?

Actually, that would be enough of a change to notice a difference. The shorter fork combined with more rake would steepn the head angle and lower the trail making the bike more sensitive to steering input.
Whether that change is god or bad is up to you.
Personally, I think it's good for a fixed gear as you'll never be going all that fast on it.
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Old 03-16-09, 08:18 AM   #7
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Quote:
Originally Posted by supercub View Post
Regarding the axle to crown length; the stock fork is about 381mm (with 40mm rake) and the Alpha-Q is 371mm (with 44mm rake). Assuming I'm getting this right, the difference in rake is somewhat offset (no pun intended) by the shorter length of the Alpha-Q blades. Is that right?
The shorter fork with more rake will MULTIPLY the magnitude of the change, not offset it. More rake makes the steering quicker, and the shorter fork increases the head tube angle, which also makes the steering quicker.
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Old 03-16-09, 11:28 AM   #8
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Ah, I see. Thanks for the correction.

One more thing. All else being equal, will a fork with a steel steerer be potentially stronger and more durable than an all carbon fork? I realize it will be heavier.
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