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For the Noobs: Dual Crown forks on Hardtails.

Jun 13, 2021 at 17:56
by Rosemary  
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I have never written much in the way of educational papers or anything fancy so if it looks like $#!t, that's because it is. Think of my blog posts as mind barfing from yours truly, about things I like and know about/think I know about . I should also put a disclaimer on here: I am a huge fan of old DH anything and have read quite a bit about this sort of thing, but I am neither an engineer or rich, so if you insist on putting a massive fork on a spindly little frame thinking it won't be a problem, and end up breaking your bike and hurting yourself that is on you. I am merely collecting information about this topic into one place for educational/entertainment purposes.



I found this old thread about putting Dual Crowns on Hardtails and it's pretty much a choatic mix of people who like them and the people who don't shouting at each other. That thread can be found here: https://www.pinkbike.com/forum/listcomments/?threadid=9440 So I am going to try to sort through it and add some things I have learned and hopefully give a decent representation of why you could/shouldn't/how to's on adding a Dual Crown to your hardtail Bike. So here goes...


Some people want to slap one of the forks from the Right of this picture on their hardtail:

Many suspensions

(Picture by @Shiny-side-up)



...Even if the ride would be better with one from the Left:

Many forks

(Picture by @ Shiny-side-up)



Whether or not this turns out okay will be based on a couple different factors.

1): What is the intended use for your Noble Steed?

2): Is the frame strong enough in the right places?

2): Do you mind having weird possiblly dangerous geometry?

And for older frames,

4): Do you have the right headset?


Before we get into the frame and fork options lets talk about above problems first. Some of the reasons you may want to put a ridiculously awesome DC fork on a hardtail are:

It looks awesome! (Some may not agree with this...), You want a steeper headtube angle as most hardtails aren't very slack, you are going down some very gnarly potholey,Rooty/Rocky DH trails and could use some endless suspension and.... You just want to.

Whatever the reason, you should definetly pick the right frame. While most frames won't die right on the spot after having a dual crown put on, the extra leverage and stiffness of a dual crown will eventually tear your headtube off of the front of your bike and that is one of the last things you want to happen when riding down your favorite steep chute or drop. Not only can you get seriously hurt, you just broke your lovely bike. So be choosy, and check the integrity of the frame before building up your new favorite steed.
The only reasons I would want to build a DH hardtail with a dual crown (besides as a retro art piece) is for downhill trails. Not XC, or Enduro, or Dirtjumping*

*Don't even try it

So you want to build a dh hardtail? as said above, make sure you have the right frame. To put it in the simplist terms, "The right frame" should involve a gusseted headtube, like the examples shown below. This adds more material and space for more weld, thus making it stronger. That being said, I wouldn't put a dual crown on something like a Transition Trail or Park (T.o.P.)* or the later versions of the 24Bikes Letoy. Even though the t.o.p. has a gusset below the bottom tube the t.o.p. is a more DJ oriented frame and the LeToy... well, just look at the last picture and tell me if you think that counts as a 'gusset'

*The first generation of Trail or Park yes... but not the DJ version.


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(Picture by @sssuper1Cool

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(Picture by @rosemarywheel)

Headtube Gusset on a .243 Racing hardtail
(Picture by @Atom631)

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(Picture by @stinkyc)

Headtube Gusset. I prefer the earlier versions but who cares
(Picture by @rosemarywheel)

So yeah... please get something with gussets.

As for the 'dangerous geometry' you may hear about, that is because a frame is built with a specific length of fork in mind. If you poke around on manufactures websites you will usually find that they allow a slight change in fork travel of plus or minus ten millimeters. There are reasons for this. If you put a fork that is much shorter on a frame designed for a longer travel option, it will turn whatever you have into a dirt jumper with a ridiculously low bottom bracket height. If you go the other way, the headtube angle will increase (Not always a bad thing) and the reach (The distance from the center of your BB to the middle of the top of the headtube/center of handlebars) will decrease basically making the bike too small for you, and the only way that willl\ change is either you are going down a near-vertical face or you get close to bottoming out your suspension and the chance of you going Over The bars is greatly increased. I personally like my suspension kind of firm anyway, so if you can find a firmer spring that will help to avoid an unpleasent dive into your suspension thus creating a much steeper head angle and causing a crash that would be embarassing and traumatic, that would be great.

What we are trying to avoid is making something like this:

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And the last thing you may need to look into is what kind of headset will you need? A lot of the old Freeride/Downhill bikes had straight 1.5" headtubes. You will need a headset that matches this. You can buy old Chris King headsets that last virtually forever (I put these on all of my bikes) but be careful, you must make sure to buy the adaptor headset that fits a straight 1.5" Headtube but is made for a 1.125 (or in fractional form: 1- 1/8 ) headtube as all dual crowns I have ever seen have 1.125" steerer tubes. These Chris King's are kind of rare, but can be found with a bit of patience on the PinkBike Buy/Sell and on eBay for slightly more but almost always in better cosmetic condition. So long as the bearings are smooth and the color is to your liking, I wouldn't worry about scrapes or scuffs. You are building a Downhill Monster, remember? Monsters have scars.

Cane Creek also made headsets for the 1.5" headtube but I cannot find anything on their website that suggests they still do. It looks like they only make 1.5's for tapered fork steerers now. FSA I am sure made them as well but I really would just find a Chris King and forget about replacing it until the next ten years have passed, these headsets are rare enough without having to replace your crappy one within a couple of years.

Here is a great article by Cane Creek on headsets:

https://canecreek.com/everything-you-need-to-know-about-headsets/


A Straight 1.5" Chris King headset complete, and the second picture showing that both the top and bottom are 1.5":

photo

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A Straight 1.5" to 1.125 (1- 1/8") Chris King adaptor for dual crowns:

(also known as the Devolution headset)

Chris King Devolution headset. Made to fit a straight 1.125 1-1 8 straight steerer into a 1.5 headset. Basically for dual crown forks.


So there you have it. Make sure the frame is strong enough with the proper gussets in the proper areas, make sure this is actually the kind of bike you want for the kind of riding you want to do, and get the proper headset for it.

And of course, have fun and don't let the haters get you down. DH hardtails are fun!



Here is a short list of older freeride hardtails That can/I believe can take the abuse of a dual crown, in order below:

Transition Vagrant. The V1 came with a 1.125 headtube and the V2 came with a 1.5.

Soul Cycles Sluggo. Pretty damn rare.

Mythic/Banshee Morphine. This came in Red, Yellow, White and Black.

.243 Racing hardtail.

Clincat Tankass (also very rare)

And of course if you you have an Evil Imperial (Sluggo and Duncon Cock are basically the same thing) You can probably do whatever you want with it without worry, at least to the integrety of the frame Smile

photo
(Picture by @Infiltrator)

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(Picture by @Ridenow)

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(Picture copied and uploaded from PinkBike to my own PinkBike album by @rosemarywheel)

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(Picture by @Atom631)

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(Picture by @Banshee-ripper)

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(Picture by @filip1989)

A bonus! A fantastic looking 2009 Norco Manik by @BrandonZamp with a 2002 Marzocchi Monster and a Mavic Deemax wheelset. A fantastic build.

photo
(Picture by @BrandonZamp)

Beer Rosemarywheel

Author Info:
rosemarywheel avatar

Member since Oct 5, 2019
2 articles

6 Comments
  • 1 0
 Advise , Do not use CK headset with dual crowns on a hardtail ,i cracked my lower cup all around with monster Ts on my hardtail headtube is fine , CK not so much though
  • 1 0
 Eek and here I am buying extras! lol Good to know. What do you use?
  • 2 0
 Brilliant and fun article !
  • 2 0
 Thank you! I am so happy you like it! I hope to write more about all the old stuff I stay up way to late reading and researching about Smile
  • 1 0
 Well done. Keep up the good work.
  • 1 0
 Thanks! Will do...







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