MRP Bartlett and double crown wisdom

Morning STW. I’ve never ridden a DH bike or any bike with a double crown fork but I’m mulling over a heavy duty more-downey-than-uppey 29er full sus and have spotted the MRP Bartlett (https://www.mrpbike.com/bartlett/), a ‘shorter’ travel DC fork. The frames I’m thinking about are for 160mm forks. The Bartlett is 170mm minimum….
But, the axle to crown height seems to be the same at 573mm. Also, with a 44mm head tube and the 1 1/8 steerer, I could run a semi-integrated rather than external cup and save another 10ish mm. Right?
Seeing as I’m looking for a large error margin rather than suddenly going all Josh Bender, and the a2c is the same as or less than the recommended maximum, what is the risk with the Bartlett? I see some DH frames have bumpers on the top tube, is this in case of a tank slapper with a DC fork? Inform me oh mighty STW brain.

Obvs want it coz it looks awesumz.

I’m confused. You want to build an enduro bike with dual crowns set at 160mm? Like the good old days?

http://ep1.pinkbike.org/p4pb6064381/p4pb6064381.jpg

Yes. Well, at 170mm.

Édit. Looked at your photo, which is a hard tail with its geometry screwed. What is the risk of a dual crown if it DOESN’T change the geometry ?

I’d say go for it, aslong as you don’t mind the extra weight. I’ve been thinking of doing the same after seeing how much single crown’s flex on those pink bike slow mo vids of enduro bikes being hucked to flat.

I like your thinking Eddie!

I’d been thinking about cause last time I was at Bpw I seemed to land every drop to flat rather than hit the transition, iam riding 10 yr old lyrics and that pink bike vid has made me question how much longer my lyrics will last if I keep riding like a donkey

What is the risk of a dual crown if it DOESN’T change the geometry ?

Crashing and ripping the headtube out of the bike when forks spin around.

I’ve seen that happen in a very minor crash, which meant that the frame was fatigued from other crashes and was just waiting to fall apart. So the worst thing is that the frame can fatigue from a series of minor crashes and you don’t realize it, then the headtube falls off when you’re riding. That happened to a friend, although I wasn’t there to see it. He was wearing a full-face helmet luckily, he apparently just face planted straight in, had no idea what had happened.

I hear you Hols2, I hear you. So what do DH bikes have to resist this, just thickened tubes at this point? I don’t see bumpers on all the frames. I am only talking about running a 170mm instead of a 160mm fork, on a bike designed for the latter and with the same axle to crown measurement. What do those 10mm of travel change intrinsically, IF the stanchions aren’t hitting the top tube?

Maverick had the DUC32 (and the prototyped but never released DUC36), and I don’t seem to remember any stories of their bikes losing head tubes. They were (afaik) 150mm travel.

Whatever bike you put them on, check it’s rated for dual crown forks. If the forks don’t flex at the crown, it could cause flex elsewhere, ie, the headtube/rest of your frame junction.

Which video in particular? Anyone care to linky please? ta

Depends on the bike! A big strong carbon or heavily gusseted headtube should be fine, I believe the Nomad, the Firebird and the YT Capra are all rated for dual crowns. Porter has been running dual crows on Nicolais, so they may be up to the task as well. Specialized Enduros can be bought with dual crowns, there was one sold last year with boxxers!

Hmmm, looking at steel full sussers. Cotic said DC is not ok for the Rocket Max. BTR haven’t answered yet for the Pinner (29er on its way apparently). Haven’t asked any others yet.

Video jonesyboy, what video?

Finally, a cheeky pic of the fork, for those wot can’t be @rsed to click the link.

Go back a few years and ‘all’ the Spesh Enduros had dual crown forks, so cant see why it should be an issue as long as your not exceeding recommended a2c.

It’s a nice looking fork, Boxxer World Cups are about the same weight though – and actually shorter for the travel. 580mm A2C for 200mm Vs 575mm A2C for 190mm. You could get some Boxxers cut down.

Give Nicolai, Specialized or YT a call. Might be better off with a 27.5 bike though, if you want something a bit downduro.

Unless you’ve ridden a Fox 36 or a Lyrik and thought ‘this is a bit flexy’ I really can’t see why you’d want to go for dual crown forks on a bike that’s not a full DH one.

Chris Porter may harp on about this sort of stuff, but he’s a fairly big, fairly heavy guy. For people like me, who are around 65kgs, dual crown forks don’t offer any real advantage unless they’re on something with 200mm+ of travel, where the extra stiffness is needed.

As an aside, Pink Bike’s obsession with taking pictures of bikes hucked to flat is very weird.

JP

https://m.pinkbike.com/forum/listcomments/?threadid=162095&pagenum=1571

People are running dual crowns on their 2018 Capra’s, YT have said they are rated for them. There’s someone with a bartlett on theirs in that thread, looks great!

https://forums.mtbr.com/yt/2018-yt-capra-29-a-1068413-10.html

Scroll down, 29er Capra with a Bartlett

@jjprestidge, I know I don’t ‘need’ the fork, like most of my bike stuff! I weigh considerably more than 65kg though, more like 95kg fully kitted (for 1.88m, so not a complete porker) and have another bike for lighter duties. I don’t live near enough to the Alps to warrant a true DH bike but when I’m in the mountains the trails do have some climbing sections, or the lifts aren’t open early season. Cheers, Gaidong

Had a mate with a long XL cannondale and a lefty, the complaints when we hit the tight twisty trails (well only on tight lefthanders)

Kitted up I’m topping the scales a bit more than you, I can’t get the Yarri to feel flexi though I’m not doing stupid hucks to flat on it so that must be the problem.

Plenty of twisty DH tracks where dual crowns still rule the roost, you learn to ride around the turning circle issue. I used to ride them a lot when I was in my teens and never had an issue. These days I should imagine that boost forks have improved the turning circle.

If you’ve never ridden a dual crown with a direct mount stem and then swapped onto a single crown, or haven’t ridden a dual crown in years you won’t get it. They simply stay more supple in rock gardens where the fork is being deflected around and the steering feels loads more solid. It’s not big hucks where they feel great, it’s when laying off the coward levers in rock gardens.

https://www.pinkbike.com/news/intends-new-stem-actually-improves-cockpit-stiffness-review.html

You don’t get the kinds of deflection in the stem seen in those videos with dual crowns. You feel that when you move to them.

I reckon a 29er Capra, setup with 170mm at the rear and 180mm DC fork at the front would be a great UK park bike – the axle to crown length would mean it would still be manageable for climbing as well for if you wanted to go and play around at places like Wharncliffe, Grenoside, Chicksands or Aston Hill. At a push, unlike a DH bike, you could still get it around a trail centre – and you could probably keep the weight of the bike at around 32lb!

Sounds brilliant to me!

Then again, I intend to run a 190/180mm setup with my Supreme SX – so I am biased.

@Raybanwomble, I’m sat at my desk, cold, but absolutely gagging to get out riding after reading that. Cheers!

what raybanwomble says does sound good certainly to experiment with. But it would be a fair chunk of cash to experiment !.
A big benefit of dual crowns is MOR stiffness when running at MOR travel. So using a dual crown at 160mm or 170mm would kind of defeat the purpose in my view. I’d just have a 160mm single crown fork.

I have Dh bike with Boxxers, totally love it, but, weird geometry and weight aside i wouldnt fancy climbing at all with a dual crown fork. if you do do it OP, let me have a go!

I will invent my own class of MTB. GAIDURO. It involves pedalling the heaviest possible bike up a mountain and then riding down it with almost, but not quite, DH-like stiffness and travel.