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tandem fork builder

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tandem fork builder

Old 10-28-20, 11:07 AM
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Serenity5
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tandem fork builder

I am looking for a custom build fork rated for tandems, I don't want carbon just a good quality steel would be great. Thanks
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Old 10-28-20, 12:52 PM
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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.
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Old 10-28-20, 01:15 PM
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joeruge
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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
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Old 10-28-20, 09:14 PM
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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.
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Old 10-28-20, 10:02 PM
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jim_pridx
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Originally Posted by joeruge View Post
I second R+E cycles. At least give their article on tandem forks a read: https://www.rodbikes.com/articles/ta...dem-forks.html
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.
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Old 10-28-20, 10:42 PM
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Originally Posted by jim_pridx View Post
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.
Funny you should ask! I just happened to discuss this issue in regards to the Chloe' Dygert's World Championships TT crash. I argued the bike was poorly designed, whereas others blamed the rider, or a flat tire, neither of which are true in my opinion. A world-class professional TT rider suddenly forgets how to corner on a TT bike? Sorry, that doesn't fly with me.

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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Old 10-28-20, 11:13 PM
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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!)
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Old 10-29-20, 11:37 AM
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Originally Posted by LV2TNDM View Post
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.
Yeah, if I were to make an "uneducated guess" myself, I would probably come up with a similar assessment. There's obviously something inherently awry with this particular fork, for we've had both of our other tandems above 50mph with no problems whatsoever. Also, we're a fairly heavy team at around 335 lbs., so I would imagine that carrying that kind of weight adds a little more stress to the fork as well. To be on the safe side, it's probably a good idea for me to seek out another fork at some point in the near future.
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Old 11-05-20, 08:40 AM
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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.
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Old 12-01-20, 06:45 AM
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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
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