tandem fork builder
#2
Senior Member
I've used R+E Cycles for a steel tandem fork and Cycles Chinook for a titanium tandem fork. Both are exactly what I wanted.
#3
I second R+E cycles. At least give their article on tandem forks a read: https://www.rodbikes.com/articles/ta...dem-forks.html
#4
Thanks for the article I had been on R+E site but never read that paper. I seem like he has a good head on his shoulders and very practical about the safety of tandem design. This is also one area I don't want having a catastrophic failure.
#5
Full Member
Join Date: May 2009
Location: WI
Posts: 262
Bikes: 2010 Bob Brown Cycles tandem, 2019 Co-Mo Carrera tandem, 1980 Richardson tandem, 2014 Cervelo R3, 2018 Specialized Roubaix, 1985 Bianchi Campione, 1983 Trek 720, 2020 Trek Fuel EX8, 2021 Salsa Mukluk
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I second R+E cycles. At least give their article on tandem forks a read: https://www.rodbikes.com/articles/ta...dem-forks.html
#6
Senior Member
Join Date: Apr 2005
Location: Northern CA
Posts: 751
Bikes: Cannondale tandems: '92 Road, '97 Mtn. Mongoose 10.9 Ti, Kelly Deluxe, Tommaso Chorus, Cdale MT2000, Schwinn Deluxe Cruiser, Torker Unicycle, among others.
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131 Posts
Yeah, thanks for posting this article! I have a fork on one of our tandems that I've been a little suspicious about for quite some time now. The bike goes into a front-end shimmy mode when descending while going above 40mph, and I've never been able to track down the cause. When comparing that particular fork profile to our other two tandems, though, it appears to be built much lighter in comparison. It actually appears to be more in line with my old steel racing bikes in many respects. It generally feels to be a safe bike with the exception of hitting that 40mph mark, but I have been entertaining the idea of purchasing a new fork for that bike as well.
Anyway, front end shimmy is called Hopf Bifurcation and ALL bicycles will suffer this phenomenon, given a high enough velocity. The speed at which it happens to most production bikes is way above the intended speed, so it doesn't affect riders. However, your bike suffers from a design flaw that's causing it to happen too soon; it's probably incorrect fork offset for the given head tube angle and wheel size, resulting in the wrong trail. But that's an uneducated guess on my part; I don't know much more about it, other than that.
For a full explanation, see the following response to Lennard Zinn's discussion of incorrectly-referred to as "resonance:"
https://www.velonews.com/gear/techni...-speed-shimmy/
My two college roommates are now math and material science professors and it was BRUTAL trying to follow some of their conversations over beers, post-ride. Professor Bollt was one of 'em! Total brains!
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#7
Senior Member
Join Date: Apr 2005
Location: Northern CA
Posts: 751
Bikes: Cannondale tandems: '92 Road, '97 Mtn. Mongoose 10.9 Ti, Kelly Deluxe, Tommaso Chorus, Cdale MT2000, Schwinn Deluxe Cruiser, Torker Unicycle, among others.
Liked 210 Times
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131 Posts
Speaking of non-tandem fork usage...
After building up my Cannondale mountain tandem, I realized the Pepperoni fork had to go. But at the time, I didn't have a whole lot of choice in forks. I don't think anyone was offering tandem suspension forks, other than a few boutique makers and I didn't have the cash for one.
Working at the LBS, I happen across a used Specialized Future Shock. Basically a Mag 21. I look it over and think, "Hey, this COULD work!" I'd just run the pressures WAY higher than recommended by the "manufacturer" and hope for the best! (Dodge the exploding top caps!) But wait, there's a complication: steerer tube is too short. That didn't stop me! Nothing that a little ingenuity, spare tubing and a little LocTite won't fix! Long story short, I press-fit on a section of extra 1 1/8" steer tube with said LocTite with a little thermal expansion/contraction as an aid. Worked like a charm. We rode that fork for about ten years without incident. That steerer tube was SOLID! Even folded a front wheel in half during a race when I made an ill-advised sharp steering input/change of direction on a stair-step drop-off. Fork survived unscathed.
Stupid? Most certainly! But what's life, if not an experiment! Happily I'm riding a Fox fork now that's worlds better (still not recommended by the manufacturer though!). That said, I'm VERY conservative when it comes to working on other people's bikes. Like for example when a friend asked me to install his tubulars a few months ago. Nope. No way. That's on YOU, buddy! (And I've installed and raced on enough tubulars to know how to install them properly and safely. But the liability simply is NOT worth it.)
I just read the supplied article and I cannot imagine why you wouldn't go that route. Better safe than sorry! (Coming from me? Hilarious!)
After building up my Cannondale mountain tandem, I realized the Pepperoni fork had to go. But at the time, I didn't have a whole lot of choice in forks. I don't think anyone was offering tandem suspension forks, other than a few boutique makers and I didn't have the cash for one.
Working at the LBS, I happen across a used Specialized Future Shock. Basically a Mag 21. I look it over and think, "Hey, this COULD work!" I'd just run the pressures WAY higher than recommended by the "manufacturer" and hope for the best! (Dodge the exploding top caps!) But wait, there's a complication: steerer tube is too short. That didn't stop me! Nothing that a little ingenuity, spare tubing and a little LocTite won't fix! Long story short, I press-fit on a section of extra 1 1/8" steer tube with said LocTite with a little thermal expansion/contraction as an aid. Worked like a charm. We rode that fork for about ten years without incident. That steerer tube was SOLID! Even folded a front wheel in half during a race when I made an ill-advised sharp steering input/change of direction on a stair-step drop-off. Fork survived unscathed.
Stupid? Most certainly! But what's life, if not an experiment! Happily I'm riding a Fox fork now that's worlds better (still not recommended by the manufacturer though!). That said, I'm VERY conservative when it comes to working on other people's bikes. Like for example when a friend asked me to install his tubulars a few months ago. Nope. No way. That's on YOU, buddy! (And I've installed and raced on enough tubulars to know how to install them properly and safely. But the liability simply is NOT worth it.)
I just read the supplied article and I cannot imagine why you wouldn't go that route. Better safe than sorry! (Coming from me? Hilarious!)
#8
Full Member
Join Date: May 2009
Location: WI
Posts: 262
Bikes: 2010 Bob Brown Cycles tandem, 2019 Co-Mo Carrera tandem, 1980 Richardson tandem, 2014 Cervelo R3, 2018 Specialized Roubaix, 1985 Bianchi Campione, 1983 Trek 720, 2020 Trek Fuel EX8, 2021 Salsa Mukluk
Liked 116 Times
in
70 Posts
Anyway, front end shimmy is called Hopf Bifurcation and ALL bicycles will suffer this phenomenon, given a high enough velocity. The speed at which it happens to most production bikes is way above the intended speed, so it doesn't affect riders. However, your bike suffers from a design flaw that's causing it to happen too soon; it's probably incorrect fork offset for the given head tube angle and wheel size, resulting in the wrong trail. But that's an uneducated guess on my part; I don't know much more about it, other than that.
#9
Junior Member
You could also call up DaVinci Tandems in CO. I don't know if Todd makes his own forks or sources them. But, he will likely point you in the right direction.
Bottom line is that any custom tandem builder would likely tell you who can make steel tandem forks or a good place to source a 'standard' steel fork if you are looking for something within normal size ranges.
Bottom line is that any custom tandem builder would likely tell you who can make steel tandem forks or a good place to source a 'standard' steel fork if you are looking for something within normal size ranges.
#10
Senior Member
I know you said you don't want a carbon fork but you might at least look at the CoLab Cross fork. I have one on our tandem and it is an absolute beast. It is tandem rated.
https://www.cyclemonkey.com/forks/colab-cross-fork
https://www.cyclemonkey.com/forks/colab-cross-fork