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Fork swap - good or bad idea for 27 -> 700 conversion..

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Fork swap - good or bad idea for 27 -> 700 conversion..

Old 06-28-08, 02:11 PM
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Fork swap - good or bad idea for 27 -> 700 conversion..

Hey all -

I know the 27" --> 700c wheel conversion issue has been hashed out a million times...

drop bolt, file down slots, find longer reaching brakes, etc, etc


But one thing that I am curious about that I haven't seen anywhere is what changing the fork out to a proper 700c fork on a frame designed for 27" wheels would do. For now, let's disregard the fact it is hard as hell to find a 700c fork with a 1" threaded post....


What issues do you see with this idea?
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Old 06-28-08, 02:13 PM
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Normally, the 27" brakes and fork will work just fine with 700c wheels
all the bikes I have ever owned have had the extra 4mm of clearance
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Old 06-28-08, 03:02 PM
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All other things being average I don't see any issues with it. Theoretically it'd mean the front of the bike dropping 4 mm with the accompanying change in steering geometry - which is probably in the same order of magnitude as running a bit low on pressure or differen makes/sizes of tires front and rear.

But MAYBE there's a real squirrelly frame out there where this change would make it cross the line from nervous and into unmanageable...
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Old 06-28-08, 03:05 PM
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Wouldn't running the rear 700c also mean the rear dips 4mm, so the geometry would be the same?
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Old 06-28-08, 03:46 PM
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If it's a touring or cyclocross fork it'll be just fine. But a 700c road fork with the minimal clearance would drop the front a little. over the old style forks that accepted 27 inch tires.

I'm sure you'll find a touring or cyclocross 700c fork with 1 inch steerer. There's still tons of 1 inch bikes out there.
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Old 06-28-08, 07:55 PM
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700c forks are sold in various rake offsets, and the effective length varies some between brands. So changing forks could make a significant difference in steering performance.

Al
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Old 06-29-08, 07:32 AM
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Originally Posted by DLoMatic View Post
Hey all -

drop bolt, file down slots, find longer reaching brakes, etc, etc
Drop bolt? File down slots? I don't understand what you are talking about. What are you referring to?

I have both a set of 27 inch touring wheels and a set of 700c commuter wheels for my old, 27 inch tourer/commuter bike. I simply lower the brake pads 4mm and hand spread the rear, steel dropouts from 126mm to 130mm, when I want to use the 700c wheels.
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Old 06-29-08, 07:54 AM
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Originally Posted by Skewer View Post
Drop bolt? File down slots? I don't understand what you are talking about. What are you referring to?

II simply lower the brake pads 4mm ,,,,,,
The maximum brake reach on many bikes do not permit lowering them the required 4mm - hence the need for alternate solutions such as drop bolts.
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Old 06-29-08, 08:37 AM
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Originally Posted by DLoMatic View Post
Hey all -

I know the 27" --> 700c wheel conversion issue has been hashed out a million times...

drop bolt, file down slots, find longer reaching brakes, etc, etc
Non-issue. Tektro makes quality dual pivot brakes at least down to 69mm reach. Far more than is necessary for almost any 700c on 27" frame 'conversion. They are plentiful, widely available, cheap and light.
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Old 06-29-08, 01:16 PM
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Originally Posted by Skewer View Post
Drop bolt? File down slots? I don't understand what you are talking about. What are you referring to?
This is a drop bolt: http://sheldonbrown.com/home-drop.html

Filing refers to removing a bit of metal to make the hole in the brake arm longer to--in this case--allow the pad to move further down.

But, like operator said, if you need the extra reach, go for the Tektro R556 (55-73mm reach, the longest reach calipers I'm aware of): http://www.ebikestop.com/tektro_r556...3mm-BR7303.php but they may be too long if you need less than 55mm.
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Old 06-29-08, 02:48 PM
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Originally Posted by hxzero View Post
Wouldn't running the rear 700c also mean the rear dips 4mm, so the geometry would be the same?
That would be the case if was about only replacing the wheels, but this question is about ALSO replacing the fork.
Assuming that the 27" fork and the 700C fork both have the same clearance between rim and fork crown, then the 700C fork would be 4 mm shorter between dropout and fork crown than the 27" fork.
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Old 06-29-08, 04:22 PM
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If you use a 700c fork and switch both wheels to 700c, you can get into a situation where you need a short reach brake in the front and a long reach brake in the rear. I just ran into that with an old Raleigh I'm rebuilding. Weinmann and Dia Compe used to make brakesets that would solve the problem, but I don't think anybody does now. Please prove me wrong if you can. I really don't want to buy another fork.
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Old 06-29-08, 06:53 PM
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Did just what you're proposing on a Raleigh Technium frame. 700c front fork never gave me a issue, and I made my own "drop bolt" for the rear, probably even cheaper than Sheldon. I used two tie straps and a nylon insert I cut to length that I bought at H*** Depot for less than $3. I did use the hacksaw, though, so you can add the cost of my time .
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Old 06-29-08, 09:22 PM
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Originally Posted by JiveTurkey View Post
This is a drop bolt: http://sheldonbrown.com/home-drop.html

Filing refers to removing a bit of metal to make the hole in the brake arm longer to--in this case--allow the pad to move further down.

But, like operator said, if you need the extra reach, go for the Tektro R556 (55-73mm reach, the longest reach calipers I'm aware of): http://www.ebikestop.com/tektro_r556...3mm-BR7303.php but they may be too long if you need less than 55mm.
Ok, thanks. I had read that at Sheldon Brown once and forgot about it. I replaced my Dia Compe 500 sidepulls with Tektro R736 dual pivot calipers, 47-57mm reach, and they work on my old 531 steel frame for both 27 inch or 700c wheels. The original Dia Compes were also 47-57mm reach and worked with both size wheels as well, but are not as efficient as the Tektro dual pivots.

Last edited by Skewer; 06-29-08 at 09:28 PM.
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Old 06-29-08, 09:26 PM
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Originally Posted by Dirtdrop View Post
If you use a 700c fork and switch both wheels to 700c, you can get into a situation where you need a short reach brake in the front and a long reach brake in the rear. I just ran into that with an old Raleigh I'm rebuilding. Weinmann and Dia Compe used to make brakesets that would solve the problem, but I don't think anybody does now. Please prove me wrong if you can. I really don't want to buy another fork.
If you don't want to make a drop bolt, Yellow Jersey may be willing to sell you individual calipers---not in a set.
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