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Fork curvature battle!

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Fork curvature battle!

Old 04-05-22, 01:14 PM
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styggno1
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Fork curvature battle!

I hereby claim this 1978 Masi Prestige front fork curvature as being the most beautiful ever bent by man (or woman).

Tell me I am wrong! Or prove me wrong...

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Old 04-05-22, 02:10 PM
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I think you're right.

My 1986 Paramount had a similar graceful curve which I always liked. A lot of bikes have a mostly straight fork, until the final third or quarter, where they curve more abruptly.
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Old 04-05-22, 03:26 PM
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That's an interesting topic for discussion! For me, it raises the question of what makes for an attractive fork curve. I suspect that the graceful transition from the straight segment to the curve is an essential factor, making it difficult to identify exactly where the curve begins.

While this isn't a bad criteria, I'm not sure I've seen a lot of forks where there really is a distinct point where the curve starts. My bikes are largely similar to the OP's Masi... not a ton of rake, and the curve is distributed over the bottom half.

my '74 Raleigh International:


my '87 Hetchins. I gotta admit that the photo doesn't really show off the fork... it's the best shot I've got, though.


I'd be interested in hearing whether anyone has actually classified fork bends or styles of bends. Is there a French style? An Italian style? Maybe a style unique to the NW USA?

Steve in Peoria
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Old 04-05-22, 05:30 PM
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You may be right.

Although, the topic brings to mind some of the forks I've seen on older French bikes where the curve begins lower on the blade and is sharper. Sort of like this one:

Photo taken from this listing: https://www.ebay.fr/itm/265625720397...wAAOSwiY1gerIa
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Old 04-05-22, 06:20 PM
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I'm more of a "French flick" guy myself, but I can appreciate graceful curves of all kinds.
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Old 04-05-22, 06:52 PM
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Originally Posted by BFisher View Post
You may be right.

Although, the topic brings to mind some of the forks I've seen on older French bikes where the curve begins lower on the blade and is sharper. Sort of like this one:

Photo taken from this listing: https://www.ebay.fr/itm/265625720397...wAAOSwiY1gerIa
I wonder if that is a French thing, or if it was just that era.
There was a Jo Routens and a Rene Herse that a fellow displayed at the 2018 Classic Rendezvous gathering. Beautiful bikes!! The fork looks much like what you show. Quite lovely, and I don't know if I can say whether it is more or less attractive than the Masi.



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Old 04-05-22, 07:43 PM
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How about the complete lack of curvature?


Source: https://cycling-obsession.com/how-to...-total-spiral/

Always thought they looked neat, can't speak for how they ride.
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Old 04-05-22, 08:01 PM
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Old 04-05-22, 08:04 PM
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I thought we were talking about real bent forks:
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Old 04-05-22, 08:12 PM
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Originally Posted by tricky View Post
How about the complete lack of curvature?
The most beautiful curve doesn't curve at all.

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Old 04-05-22, 08:36 PM
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The Zen bench is out of alignment.
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Old 04-05-22, 09:00 PM
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Originally Posted by thinktubes View Post
I don't see too many Bates with the Diadrant fork! Distinctive, but visually, it might be an acquired taste.

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Old 04-05-22, 10:18 PM
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One thing I've noticed is that I must have a particular fondness for a particular curvature as almost all my bikes share a distinctly similar bend across most of the length of the blade:









Except for the this one - and truth be told, it was one reason I never really took to it:



A subtle curvature across most of the length just looks "right", I suppose. To my eye, for sure

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Old 04-05-22, 10:35 PM
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Originally Posted by nlerner View Post
I thought we were talking about real bent forks:
After my last cold-setting job, the wheel didn't clear the down tube. What I get for adjusting trail in the field.
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Old 04-05-22, 10:54 PM
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Originally Posted by nlerner View Post
I thought we were talking about real bent forks:
Dali Design
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Old 04-05-22, 10:57 PM
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Originally Posted by styggno1 View Post
I hereby claim this 1978 Masi Prestige front fork curvature as being the most beautiful ever bent by man (or woman).

Tell me I am wrong! Or prove me wrong...

Masi really did sweat the details- the forks are constructed straight and the rake is introduced after. This Prestige is different than the GC period. If I have time I will snap some images tomorrow.
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Old 04-05-22, 11:01 PM
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Fork curvature BITD gave away the country of origin, I believe.


French constructeur
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Old 04-06-22, 12:05 AM
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There’s a great scene in “Fire in the Frame” when Giuseppe Marinoni is subtly tweaking fork curvature of one he’s completing by gently tapping the dropout with a small hammer. Here’s mine, and everything on this 1987 frame is beautifully aligned.

This thread wouldn’t be complete without an example of a fork featuring Gugificazione! This is the reraked Miyata 912 fork after his adjustments added 8mm of rake (and a few other features) for front loading that works fabulously well!

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Old 04-06-22, 01:50 AM
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Originally Posted by ThermionicScott View Post
I'm more of a "French flick" guy myself, but I can appreciate graceful curves of all kinds.
I have to agree with this. Variety is very good. Personally, I like the look of a long bend. This one is courtesy of @gugie's Babe Ruth of fork re-rakers.



This one, as far as I know, is the factory bend on a slightly earlier Motobacon. It gets to about the same place, but with a much more pronounced dogleg.



At the other end of the spectrum, is the very slight bend of my 3Rensho-built Allez, which gets a fair bit of its fork offset with an offset crown.



And, of course, the Colnago, which I personally love.

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Old 04-06-22, 01:53 AM
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Fork Blade Rake

Something rarely considered is the types of roads used for bike races BITD. Much of the infrastructure of Europe was destroyed during WWII. Most of the western European economies didn't fully recover until the early 1970's! Nice smooth road surfaces were not a high priority plus many early season races like the Paris-Roubaix and other events in northwest Europe were held on cobblestone roads.

During the US Bike Boom Fad, "10 Speed Racing Bike" was the buzzword. Most of the lower priced European bikes copied the frame geometry that was popular on the "racing bikes" used during the 1960's that were made for rough road surfaces. That meant relaxed head and seat tube angles, long wheelbases, especially the rear triangle and a long fork rake with most of the bend in the lower 1/3rd of the blade.

Here's an extreme example one type of fork blades offered by Reynolds. Fork blades act as springs for the front of a bike!



I used 2 1/2" rake fork blades on my long wheelbase touring frame that I build for myself in 1975 using 1950's geometry. It can go over a speed bump and I hardly feel it!



Reynolds offered 8 different fork blade designs in a 1950's tubing catalog. Note, Rake No. 3--2" and Rake No. 6--1 1/4" with the graceful slow taper bends were probably intended for use on track or time trial bikes - mostly with round blades.



Most pre-bent fork blades were shaped by hand like in this photo taken at Reynolds in the 1970's. This probably made for lots of variances depending on how many pints were consumed at lunch!


Columbus, Super Vitus and the Japanese brand tube sets came with straight blades. When I was first starting to build frames in 1975 I tried using one of these Rigid electrical conduit benders. I scrapped a number of blades before we had someone build us a jig that we could bend both blades in a brazed fork at the same time.


Some folks used something like this crude home made fixture frequently with a wooden form instead of this bent angle iron.



This is a very sophisticated commercial fork bender made by Anvil that bends both blades at the same time.



My late 60's early 70's Galmozzi built Lazzaretti with classic road bike geometry from the era: long wheel base and rake with 73 angles.



By the end of the bike boom in 1973 a lot of Italian frame makers were building frames with geometry that had previously been used for track bikes only: short wheelbases and fork rakes with 74 angles. Top Italian builders like Masi an DeRosa were putting out forks with a beautiful, graceful bend that started at the fork ends and went all the way to the crown. Ron Cooper in the UK was a proponent of that style too.

1970's Masi Gran Criterium.



Creating those bends takes a lot more effort than just starting 2/3rds of the way down the blade. Slow taper fork blades became De rigueur on better bikes and frames into the mid-late 80's but not many took the bend all the way to the top. There is a slight trade off with those style blades in that they are going to be less shock absorbing than blades with a rake lower down in an area with a smaller diameter.

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Old 04-06-22, 03:33 AM
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Originally Posted by verktyg View Post
Some folks used something like this crude home made fixture frequently with a wooden form instead of this bent angle iron.
From Rob Roberson's Masi clone project:

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Old 04-06-22, 04:19 AM
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Originally Posted by tricky View Post
How about the complete lack of curvature?


Source: https://cycling-obsession.com/how-to...-total-spiral/

Always thought they looked neat, can't speak for how they ride.
Originally Posted by Andy_K View Post
I have to agree with this. Variety is very good. Personally, I like the look of a long bend. This one is courtesy of @gugie's Babe Ruth of fork re-rakers.


And, of course, the Colnago, which I personally love.






Colnago lost me when they started with these straight forks. I remember seeing one for the first time and I thought "what a smart idea for cost cutting but the looks... the horror, the horror" ;-)

I bought this Master Piu frame new and it would have been a deal breaker if it would have come with a straight fork.

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Old 04-06-22, 05:49 AM
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The bend in the fork always has indicated suspension for me. The variations have caused me some hesitation as to how well they work in terms of spring rate.

When I first saw the Colnago prescia fork, I was really confused. It looks like the fork failed QC! Instead of the "bent fork" it is the bent crown!

From an esthetic perspective it is confusing too, for at least C&V designs as nearly every tube on the frame is straight. The bent fork does not match; however, it does blend with the other curves of the handlebar and the saddle, not to mention the radii of all the circular parts. I am not an artist but do have mechanical engineering thought processes which may bias me to liking the curve and accepting the discontinuous line of the prescia.

To @verktyg point, the departed 72 Le Champion is a prime example of wheelbase and fork curvature. Thanks for the encyclopedic information on forks! Really enjoyed it. Do you do a blog?
1972 Motobecane Le Champion 24" on Flickr

There is a contrast with the also mentioned De Rosa, this from the late 80's.
P1050321 on Flickr

Then there is the mid '80s Trek where the curve is between straight sections.
1983 Trek 610 60 cm (24") on Flickr
Its not bent out of spec, its been checked.
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Old 04-06-22, 06:07 AM
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Y'all got it backwards.
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Old 04-06-22, 06:30 AM
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Originally Posted by styggno1 View Post
Colnago lost me when they started with these straight forks. I remember seeing one for the first time and I thought "what a smart idea for cost cutting but the looks... the horror, the horror"
Agreed. Nothing aesthetic about that.
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