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Old 01-13-10, 09:14 AM   #1
daven1986
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Changing a fork

Hi all,

I want to put a front disk brake on my road bike. Can I just buy a new fork, shove it in, cut it and boom I am away? Or is there more to it than that?

What effect does rake have?

Would this work http://www.chainreactioncycles.com/M...?ModelID=15675 ?

What does "non suspension corrected" mean?

My bike is a Giant SCR1.

Many thanks

Daven
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Old 01-13-10, 09:25 AM   #2
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Rake effects the steering response and consequently the handling of the bike. It's best to match the rake of the original fork.
Suspension corrected means the fork is designed so a rigid fork can replace a suspension fork without altering the bikes' original geometry.
The other consideration you have is the steerer diameter and headset style of the forks. By far the easiest approach here would be to get a replacement fork that has the same diameter and uses the same style of headset.
If you get a new fork to match these parameters of the original then it is pretty straightforward.
Then you get to select your new wheel, brakes and possibly levers.

The fork you have linked is intended for a MTB with 26" wheels, not a good choice for a road bike.

Last edited by Steev; 01-13-10 at 09:34 AM.
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Old 01-13-10, 09:26 AM   #3
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Well, I assume you also plan on getting a wheel that accomodates disks and a brake to put on the fork. Also, I think disks (even mechanical) require a different brake lever, and I'm not sure if they make a drop bar version.

Non suspension corrected means the angle is not correct if you're replacing one of those tall suspension forks. Rake has an effect on steering response.

What it boils down to if this: Are you having a problem you think a disk brake will solve? You're going through quite an ordeal and risking other problems for what shouldn't be that important.
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Old 01-13-10, 09:45 AM   #4
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Quote:
Originally Posted by daven1986 View Post
Can I just buy a new fork, shove it in, cut it and boom I am away? Or is there more to it than that?
The steps are as follows:
1
Quote:
just buy a new fork,
2
Quote:
shove it in,
3
Quote:
cut it,
5
Quote:
and boom I am away:
6 ... to the shop for a 700c wheel with a disk hub
7 ... then to find a mechanical disc that will work with road levers
8 ... then to the liquor cabinet
9 ... then to bed

Note: the best result can be had by skipping 1 through 7 and proceeding to step 8
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Old 01-13-10, 03:21 PM   #5
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I have 6, will get an avid bb7 for 7! Thanks for the help, I will look around and see what forks there are! Urbanknight - basically I am unhappy with my braking performance I have kool stop salmon pads too. I have another bike with disc brakes and much prefer the stopping power on them. I don't want to go to too much trouble but I will only be replacing the fork and brake (hopefully!) everything else will be transferred and I already have a wheel.
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Old 01-13-10, 03:40 PM   #6
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also- you will have to remove the crown race off of your old fork and install it on your new fork. It is best to have the new fork's crown race "shoulder" faced by the shop with a cutting tool as well
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Old 01-13-10, 04:19 PM   #7
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Wouldn't mind taking it to a shop to get it done I guess

Is there anything wrong with putting a steel fork on a aluminium frame?

Last edited by daven1986; 01-13-10 at 04:41 PM.
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Old 01-13-10, 04:51 PM   #8
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Wouldn't mind taking it to a shop to get it done I guess
Good call.

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Is there anything wrong with putting a steel fork on a aluminium frame?
No. Many aluminum frames originally came with steel front forks, since steel offers a better ride than aluminum. Some of these may be built for cross / offroad, so they may be a little heavier / stiffer, but they should be fine.

If I were you, I'd leave the bike as is, and then work on aligning / tightening the brake pads to maximize the stopping power of your existing brakes.

If you want to do it, the steps will include the following:

Remove front wheel
Remove front brake / undo front brake cable.
Remove stem / handlebars (you can leave everything on the bars for now.
Remove fork (save spacers, bolts etc.)
Remove crown race from old fork
Install crown race on new fork (facing / seating crown race requires special tools, but can be jury-rigged)
Install new fork in headset
Insert stem / spacers to establish proper stem / bar height
Remove stem / spacers / fork and cut steerer tube to the proper length (read up on what constitutes proper length, and use a saw guide to make a properly horizontal cut)
Reinstall fork, replace stem and spacers and install for real this time (you'll need a new star nut)
Align everything
Install disk brake
Install cable and housing to connect your brake lever to the brake (make sure your lever works OK with disc brakes, or plan to do this again with a new lever / cable / housing or an adapter.
Reinstall wheel
Align disc and brake and set proper cable tension
Inspect everything

And Boom, you are away on a test ride.
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Old 01-13-10, 04:58 PM   #9
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If you have a common fork length of 368-374mm, that 395mm fork will decrease the head tube angle by about 1.2 degrees and make a major change to the steering trail. Rake or more properly, offset also makes a difference and I don't even see it listed.

Last edited by DaveSSS; 01-13-10 at 05:13 PM.
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Old 01-13-10, 05:03 PM   #10
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Thanks I will double check fork length etc.

bigvegan: another reason to change to disc brakes is that I have a dynohub wheel with a disc brake rotor on it, and this is used on my other bike. Wouldn't mind being able to switch it between both bikes.
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Old 01-14-10, 07:16 AM   #11
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I doing this modification, even adding a SRAM disc/dyno. I bought a Dimension disc cyclocross fork:
http://www.universalcycles.com/shopp...5&category=704
I'm running upright bars so the lever issue is taken care of.

The key dimensions on a replacement fork (besides correct steer tube diameter/length) is axle-to-crown length and rake. My frames stock fork has 400mm axle-to-crown and 50mm rake. The Dimension fork is 400mm and 45mm. I find the bike handles smoother with the shorter rake, esp at slow speeds.
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Old 01-15-10, 01:52 PM   #12
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It is best to have the new fork's crown race "shoulder" faced by the shop with a cutting tool as well
never knew this. can someone explain why?
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Old 01-15-10, 02:56 PM   #13
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Urbanknight - basically I am unhappy with my braking performance I have kool stop salmon pads too. I have another bike with disc brakes and much prefer the stopping power on them. I don't want to go to too much trouble but I will only be replacing the fork and brake (hopefully!) everything else will be transferred and I already have a wheel.
In my experience, the poor stopping power on a road bike is due to the skinny, low rolling resistence tires. If you can lock the wheel into a skid on your current brakes, the brakes aren't the weak link. If you can't, your project sounds like an adventure worth exploring.
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Old 01-15-10, 03:10 PM   #14
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.......It is best to have the new fork's crown race "shoulder" faced by the shop with a cutting tool as well
never knew this. can someone explain why?
For the same reason why it is a good idea to face the ends of the head tube. By facing these surfaces you ensure that the headset bearings align correctly so they provide the silkiest smooth steering feel.

I've never done this to the fork myself but I've had to correct a couple of frame head tubes to square things up.
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Old 01-15-10, 03:58 PM   #15
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For the same reason why it is a good idea to face the ends of the head tube. By facing these surfaces you ensure that the headset bearings align correctly so they provide the silkiest smooth steering feel.

I've never done this to the fork myself but I've had to correct a couple of frame head tubes to square things up.
It was necessary to face the crown extension on my Colnago fork before the King lower race would go on.
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