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New BOS usd fork.

kidwoo

Artisanal Tweet Curator
Facts from 2014 (caution, metric units):
Told you there's a reason I'm holding onto my 2013 40.

I will NOT be Ruxxed up.


edit: translations are fun

Trophy or hospital - a winged word among downhillers. And it is also a good fit: our test track in the Bikepark Bad Wildbad is a nightmare.

I need to go to more bikeparks named Bad Wildbad.
 
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Kanye West

220# bag of hacktastic
Aug 31, 2006
3,740
470
Ahhh I love me some actual data in the early morning.

So, the twisting stiffness of a Dorado is half that of a 40 or whatever else. It is also 25-30% stiffer in pure bending fore/aft. Let's assume for the time being there's a similar margin for bending left/right.

Which of these represents the on-trail behavior of the front end of the bike in a corner? And...once you choose, explain HOW. Explain where the leverage and load path come from.

UDI, this should give you a Godzilla-sized boner right now. I bet that keyboard is going to be piping hot once you're done.
 

Sandwich

Pig my fish!
Staff member
May 23, 2002
21,030
5,918
borcester rhymes
I remember reading once that a USD fork would get stiffer through its travel due to increased bushing overlap as it compresses. I was never really confident how the physics would play out in such an instance.

is there any reason a USD fork couldn't be made to work well and be adequately stiff? I like my 40, but I can comfortably say I don't need MOAR stiffness in a downhill fork. Less would be acceptable at times. Instead of a carbon Fork Arch to Resist Torsion (FART), could you simply do a bigger axle and externally braced upper tubes?
 

Kanye West

220# bag of hacktastic
Aug 31, 2006
3,740
470
I remember reading once that a USD fork would get stiffer through its travel due to increased bushing overlap as it compresses. I was never really confident how the physics would play out in such an instance.
That's only if you have a bushing attached to the stanchion that telescopes inside the upper tube. No such system in mtb forks at this time.
 

kidwoo

Artisanal Tweet Curator
USD forks wander like a mother fucker when your front wheel catches the sides of things and when grabbing or breaking traction and moving laterally. Any idiot who's ridden one knows this and you don't need hoffdata™ to justify trying to ignore that fact by pretending all impacts are 100% head on.

Might buy another one if it has a 100mm diameter axle.
 
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djjohnr

Turbo Monkey
Apr 21, 2002
3,001
1,693
Northern California
I had a recent Dorado set to 180mm that never gave me a serious problem with wandering. On the other hand I remember demoing a single crown Shiver that was like having a random direction generator strapped to the front of the bike.
 

Jm_

sled dog's bollocks
Jan 14, 2002
18,850
9,556
AK
This is a cool picture of me from a long long time ago. The best part was almost crashing when I landed because the fork went whatever way it wanted to in the rough. Dangerous as fuck.

1929552_515561688478_1145_n.jpg
 

Udi

RM Chief Ornithologist
Mar 14, 2005
4,915
1,200
is there any reason a USD fork couldn't be made to work well and be adequately stiff? I like my 40, but I can comfortably say I don't need MOAR stiffness in a downhill fork.
Sure, if you want to take what you're happy with and make it heavier, flexier, and inferior. :)
 

Happymtb.fr

Turbo Monkey
Feb 9, 2016
1,907
1,252
SWE
Sorry for an on topic break but Probikeshop who is selling spare parts for Bos just messages on a French forum that there is some press material to be released regarding how Bos has been working on improving customer support, availability of spares and communication.

It sounds like a well needed improvement and let's hope they do it right.
 

konastab01

Turbo Monkey
Dec 7, 2004
1,203
208
Dont care how flexy these are I really want them or maybe the ohlins ones if they actually come out.
 

William42

fork ways
Jul 31, 2007
3,908
634
Whats harder on a fork? A ~200lb ish dude like Brook McDonald shralping a rock garden, or a 120 lb girl like Mannon shorting a 40 foot double and casing the shit out of it? Which one do you need your fork to be uber stiff for?
 

norbar

KESSLER PROBLEM. Just cause
Jun 7, 2007
11,346
1,587
Warsaw :/
Sorry for an on topic break but Probikeshop who is selling spare parts for Bos just messages on a French forum that there is some press material to be released regarding how Bos has been working on improving customer support, availability of spares and communication.

It sounds like a well needed improvement and let's hope they do it right.
Impossible. I've heard they still use the guillotine in France for people who offer good customer support
 

Happymtb.fr

Turbo Monkey
Feb 9, 2016
1,907
1,252
SWE

Udi

RM Chief Ornithologist
Mar 14, 2005
4,915
1,200
@slimshady
@Happymtb.fr
I meant to say this (forget if I did or not since maybe it's super obvious?), but square/keyed bushings are a bad idea, because it means that the reaction force against torsional flexure force (i.e. the cause of any stiffness benefit) is ALSO the normal force in the friction equation.

This means each time you have torsional forces going through the fork (which is most of the time in MTB), you're driving sliding friction through the roof. You also get some nasty localised loadings at the stanchion/bushing interface, so premature wear is likely. It's not a good idea for performance in the short term, or durability in the long term.

Of course you get a much smaller version of this scenario in any circular-bushing fork too but the effect is much less (and less localised) because the parts are free to rotate against each other. It's always best to increase stiffness via non-sliding interfaces which is why the arch of a normal fork's casting works very well (as would a huge 35-40mm axle if we were OK with heavier hubs and nonstandard parts).
 

slimshady

¡Mira, una ardilla!
Yeah, I know the leverage against the bushings would mean the stanchions could basically lock out momentarily if the tolerances aren't tight enough. I think the main reason some brands resort to this solution is to keep the weight tolerable for a given stiffness goal.
 

Jm_

sled dog's bollocks
Jan 14, 2002
18,850
9,556
AK
I think the main reason some brands resort to this solution is to keep the weight tolerable for a given stiffness goal.
No, it's because they are Cannondale and they will find some way to f*ck up simple shit.


However, the left is about the perfect solution for fatbikes IMO. I saw that new manitou fork and it has the largest brake arch on earth, ever, 6+lb fork.
 

Happymtb.fr

Turbo Monkey
Feb 9, 2016
1,907
1,252
SWE
forget if I did or not since maybe it's super obvious?
Sometimes it is good to say some obvious things! :D

It is a tuff call for small producers willing to enter the fork market: either you invest a lot of money into expensive casting tools multiple times because there are several hub, tires and wheel sizes or you go the USD-way which give you plenty of flexibility, a much smaller investment and some other technical drawback do deal with...
 

toodles

ridiculously corgi proportioned
Aug 24, 2004
5,479
4,719
Australia
News outlets seem pretty excited about Formula's new DH offering as well. Plus Formula have set up a Canadian distributor based in Whistler so looks like they're ready to make some moves into North American market.