Fork Replacement - What measurements do I need?
12-07-15, 01:43 PM
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Fork Replacement - What measurements do I need?
I need to replace a cracked fork on an unbranded, used bike. What I do know:
1" threaded
700c
chromoly
Is there a reliable way to measure rake with just a tape measure?
What do I measure to make sure my tire choice will fit? Currently 700 x 35 on a "track" bike.
Do I need the neck length? Anything else?
Any suggested U.S. online stores with a big selection?
1" threaded
700c
chromoly
Is there a reliable way to measure rake with just a tape measure?
What do I measure to make sure my tire choice will fit? Currently 700 x 35 on a "track" bike.
Do I need the neck length? Anything else?
Any suggested U.S. online stores with a big selection?
12-07-15, 09:19 PM
#2
Lapped 3x
To measure rake, remove the fork and lay it on a table. Set it up so that the steerer is parallel to the table surface. Measure the center line of the steerer from the table surface. Measure how far the center of the dropouts are from the table. The difference between the two is the rake.
Sometimes the axle to crown race length is a good measurement to have, but this is usually standard. Axle to inside crown distance is also good to know as this may affect tire clearance as well, although most forks will list what tire sizes they can accomodate.
Sometimes the axle to crown race length is a good measurement to have, but this is usually standard. Axle to inside crown distance is also good to know as this may affect tire clearance as well, although most forks will list what tire sizes they can accomodate.
12-08-15, 02:27 PM
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You need to know steerer length for your frame.
Soma
Surley
Nashbar
Google "Bicyce Fork"
Soma
Surley
Nashbar
Google "Bicyce Fork"
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12-08-15, 04:08 PM
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You also need to know steer tube length, and how much stack height your headset needs. It's ok to get a fork with more steer tube than the headset needs because you can always either trim it or use spacers to make up the difference, but if it's too short, you're SOL.
12-10-15, 09:42 AM
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To measure rake, remove the fork and lay it on a table. Set it up so that the steerer is parallel to the table surface. Measure the center line of the steerer from the table surface. Measure how far the center of the dropouts are from the table. The difference between the two is the rake.
Sometimes the axle to crown race length is a good measurement to have, but this is usually standard. Axle to inside crown distance is also good to know as this may affect tire clearance as well, although most forks will list what tire sizes they can accomodate.
Sometimes the axle to crown race length is a good measurement to have, but this is usually standard. Axle to inside crown distance is also good to know as this may affect tire clearance as well, although most forks will list what tire sizes they can accomodate.
Tire clearance and/or axle to inside crown is what I'm not seeing with most fork listings I've come across.
You also need to know steer tube length, and how much stack height your headset needs. It's ok to get a fork with more steer tube than the headset needs because you can always either trim it or use spacers to make up the difference, but if it's too short, you're SOL.
Maybe I'm looking in the wrong online stores. Listings are very ambiguous. I'll check where SJX426 listed.
12-10-15, 10:01 AM
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@BexO - Yes, especially threaded forks!
It is challenging if you are looking for 1" threaded forks. You may have to resort to threading the tube further down a steerer that is too long. As JDT stated, you need to know your stack height to know the steerer length. School yourself on the complexities by doing some reading on the subject to the point you understand and can explain the dependencies of the assembled system.
I am in the Advanced editing mode so can't read earlier posts, but don't forget that you don't want to thread too far down the Steerer tube because of the possibility of failure from using a quill stem with a wedge that causes the steerer to fail in the threaded portion of the steerer tube.
There is a lot to consider but not enough to give up!
It is challenging if you are looking for 1" threaded forks. You may have to resort to threading the tube further down a steerer that is too long. As JDT stated, you need to know your stack height to know the steerer length. School yourself on the complexities by doing some reading on the subject to the point you understand and can explain the dependencies of the assembled system.
I am in the Advanced editing mode so can't read earlier posts, but don't forget that you don't want to thread too far down the Steerer tube because of the possibility of failure from using a quill stem with a wedge that causes the steerer to fail in the threaded portion of the steerer tube.
There is a lot to consider but not enough to give up!
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12-10-15, 10:32 AM
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12-10-15, 11:47 AM
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maybe it has already been mentioned (EDIT: i see that it has), but i would want to know the distance from the brake hole to the dropouts. why? because the geometry of forks for bikes using various rim sizes (MTB, 650c, 27.5, 700c, 27", etc) can be, but are not necessarily, mutually exclusive. the intended tire size WRT height (20mm, 23mm, 25mm, 28mm, 32mm, etc.) can also be a factor.
as mentioned, the fork crown to dropout distance is not always available. so i usually rely on the description. like "road fork" "26" MTB fork", or "27" road fork", or "track fork" "650c fork". some digging to understand the ramifications of these phrases may be necessary.
as mentioned, the fork crown to dropout distance is not always available. so i usually rely on the description. like "road fork" "26" MTB fork", or "27" road fork", or "track fork" "650c fork". some digging to understand the ramifications of these phrases may be necessary.
Last edited by hueyhoolihan; 12-10-15 at 12:05 PM.
12-10-15, 12:42 PM
#10
Calamari Marionette Ph.D
A post above states that the axle-to-crown measurement is "usually standard." This is not true. The measurement can and does vary widely. Some forks are designed to accommodate BIG tires and fenders with room to spare, while others are designed for the tightest fit possible using a 23mm tire. A longer or shorter fork than you frame was designed for will also result in your headtube angle changing.
Just sayin. Be aware of your needs and of what you are buying. Good luck.
Just sayin. Be aware of your needs and of what you are buying. Good luck.
12-10-15, 12:54 PM
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@SquidPuppet,
Yeah, my biggest concern is tire clearance. I currently run 700x35 and can fit a 700x37. Very important for the new fork to have the same spacing.
I don't want to change the headtube angle either.
Common sense tells me that axle to crown can be measured straight, with no regard for rake. Am I correct in that thinkinig?
I'll completely remove the fork and get everything meassured, then start my search again. I'd hate to rely on a shop for this.
Yeah, my biggest concern is tire clearance. I currently run 700x35 and can fit a 700x37. Very important for the new fork to have the same spacing.
I don't want to change the headtube angle either.
Common sense tells me that axle to crown can be measured straight, with no regard for rake. Am I correct in that thinkinig?
I'll completely remove the fork and get everything meassured, then start my search again. I'd hate to rely on a shop for this.
12-10-15, 01:07 PM
#12
Calamari Marionette Ph.D
@SquidPuppet,
Yeah, my biggest concern is tire clearance. I currently run 700x35 and can fit a 700x37. Very important for the new fork to have the same spacing.
I don't want to change the headtube angle either.
Common sense tells me that axle to crown can be measured straight, with no regard for rake. Am I correct in that thinkinig?
I'll completely remove the fork and get everything meassured, then start my search again. I'd hate to rely on a shop for this.
Yeah, my biggest concern is tire clearance. I currently run 700x35 and can fit a 700x37. Very important for the new fork to have the same spacing.
I don't want to change the headtube angle either.
Common sense tells me that axle to crown can be measured straight, with no regard for rake. Am I correct in that thinkinig?
I'll completely remove the fork and get everything meassured, then start my search again. I'd hate to rely on a shop for this.
The best thing to do is to buy a fork that matches your measured needs, or alters things in a direction that your desire. Aint always easy as you are discovering.
If you have the time and/or desire here is a free (and excellent) CAD program for custom bike building. Very fun, entertaining, and educating. You can design ANYTHING. After that you can see how tiny tweaks affect an existing bike.
www.bikecad.ca | Bicycle Design Software
12-11-15, 12:18 AM
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I bought one of these and quite happy with it. Lots of steerer height so you have plenty of room to use your favorite headset and chop the rest off.
It definitely has more room too. I'm running 28mm and it's fine. Do you have the exact width of 35mm tires? I know some can measure a bit thinner/fatter. Don't worry about tire height. It's definitely not a true track fork with paper thin lower crown/tire clearance. With 28mm tires, I have around 1/2-3/4" above the tire and the crown.
It has around a 40 degree trail which was a huge improvement to my Pista's 28mm. Just so much more lively.
It paid a little less on ebay but it's still a great price for a lugged threaded fork that's surprisingly light. Mine took about 4-5 days to arrive at my house.
RH O FOK 932 Full CR MO 4130 Silver 1" Lugged Curved Threaded Front Fork Chrome | eBay
It definitely has more room too. I'm running 28mm and it's fine. Do you have the exact width of 35mm tires? I know some can measure a bit thinner/fatter. Don't worry about tire height. It's definitely not a true track fork with paper thin lower crown/tire clearance. With 28mm tires, I have around 1/2-3/4" above the tire and the crown.
It has around a 40 degree trail which was a huge improvement to my Pista's 28mm. Just so much more lively.
It paid a little less on ebay but it's still a great price for a lugged threaded fork that's surprisingly light. Mine took about 4-5 days to arrive at my house.
RH O FOK 932 Full CR MO 4130 Silver 1" Lugged Curved Threaded Front Fork Chrome | eBay
Last edited by Regulatori; 12-11-15 at 12:21 AM.
12-11-15, 12:15 PM
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@SquidPuppet, thanks again. And this CAD program is fun! Dream bike coming up.
@Regulatori, thanks. I will definitley take a closer look at that fork once I've done my measuring.
I remember my tires being a little less than 35mm wide, but I don't remember exactly. I'll check tonight.
I have less than 1/2" between tire & crown now.
@Regulatori, thanks. I will definitley take a closer look at that fork once I've done my measuring.
I remember my tires being a little less than 35mm wide, but I don't remember exactly. I'll check tonight.
I have less than 1/2" between tire & crown now.
12-11-15, 01:11 PM
#15
Calamari Marionette Ph.D
12-11-15, 01:14 PM
#16
Calamari Marionette Ph.D
@SquidPuppet, thanks again. And this CAD program is fun! Dream bike coming up.
.
.
Yeah a couple years ago I got pretty snowed in and I spent days on that thing. Custom angled handlebars, custom curved forks, custom welds, colors....... Too fun.
