[Lelandjt]

https://extusa.bike/collections/forks/products/ext-ferro-e-mx-fork
EXT just released this inverted 205mm steel 36mm stantioned fork for Sur-rons, Talarias, Kubergs, Drills, and other e-dirtbikes that use MTB headsets and suspension. I wonder if anyone will try it on a DH bike or long travel e-bike. Maybe they'll do an aluminum stantion, carbon leg DH version.

 

[sethimus]

a bit heavy for bike use

 

[bullcrew]

Yeah a bit heavy...looks ok...

 

[Lelandjt]

Looks like Manitou's hex axle patent has expired. I wonder if Push will use one. Could the axle conundrum* be what killed the Fox USD project and now the hex axle could bring it back?

*20mm round axles have proven much too flexy on USDs. Forks that used proprietary larger axles didn't sell well. DVO's carbon brace/stantion guard seemed like a good solution. If you put that on my hex axle equipped Dorado the combination might eliminate what I consider to be boarderline unexceptable torsional flex.

 

[canadmos]

Looks like Manitou's hex axle patent has expired. I wonder if Push will use one. Could the axle conundrum* be what killed the Fox USD project and now the hex axle could bring it back?

*20mm round axles have proven much too flexy on USDs. Forks that used proprietary larger axles didn't sell well. DVO's carbon brace/stantion guard seemed like a good solution. If you put that on my hex axle equipped Dorado the combination might eliminate what I consider to be boarderline unexceptable torsional flex.

That DVO arch was secured with 8 little bolts, but the upper tube slid on the thing as well.

I wonder how much it actually helped?

 

[Lelandjt]

It does look like it would need to be attached in a more braced way to have an effect but at the time people said with or without made a noticable difference.

 

[iRider]

It does look like it would need to be attached in a more braced way to have an effect but at the time people said with or without made a noticable difference.

People were wrong! One of the German bike mags had the DVO with and w/o brace on the test rigs for for/aft and torsional stiffness. Result: not much difference.

 

[Jm_]

Because its like a 2 foot long piece when you unbend it and look at the attachment points. A 5” wide brace…like you get directly bridging the lowers of non-inverted forks is much…much stiffer. It would need to be like the halson inverson brace to actually do something.

 

[Happymtb.fr]

Looks like Manitou's hex axle patent has expired

A square taper would do the same as an hex axle, don't you think?
That's how my french inverted fork works

 

[mtg]

I’m surprised they didn’t spec more travel, but it’s cool to see the options continue to grow for these bikes.

 

[Lelandjt]

A square taper would do the same as an hex axle, don't you think?
That's how my french inverted fork works

I assumed the patent covered any multisided axles that use straight sides to resist torsion. I haven't seen a square axle before.

 

[Lelandjt]

I’m surprised they didn’t spec more travel, but it’s cool to see the options continue to grow for these bikes.

Yeah, I kind of expected 210-215mm.
P.S. My 10" travel 184lb Ultra Bee should arrive this month. I'm selling my last 2-stroke, a KTM Freeride 250.

 

[Happymtb.fr]

I assumed the patent covered any multisided axles that use straight sides to resist torsion. I haven't seen a square axle before.

These patent people are smarter than me
I also realise that the manitou design is hexagonal on both sided while in my case, the square taper is only on one side.
I can post a picture later.

 

[HardtailHack]

I have a Hexlock and to me it just looks like marketing BS, it fits loose in the fork and the aluminum bolt doesn't feel like it gives great clamping force after a few uses.
How is a hex shape beneficial for axial stiffness?
Why not just use a round axle with the same OD as the largest part of the Hex axle?

 

[Electric_City]

People claim the Lefty was stiff. That's inverted and half assed. How come other inverted forks flex so much?

 

[Jm_]

People claim the Lefty was stiff. That's inverted and half assed. How come other inverted forks flex so much?

Because the lefty had square stanchions

 

[jonKranked]

Forks that used proprietary larger axles didn't sell well.

historically yes. but now that DH forks are basically* the only things that still use a 20x110 axle, maybe its time to revisit that standard? <ducks>

 

[jonKranked]

How is a hex shape beneficial for axial stiffness?
Why not just use a round axle with the same OD as the largest part of the Hex axle?

is this a serious question?

 

[Lelandjt]

I have a Hexlock and to me it just looks like marketing BS, it fits loose in the fork and the aluminum bolt doesn't feel like it gives great clamping force after a few uses.
How is a hex shape beneficial for axial stiffness?
Why not just use a round axle with the same OD as the largest part of the Hex axle?

Agreed that the hex seems like a looser fit than ideal. By having more resistance to the dropouts rotating relative to each other than just friction on a round tube it's supposed to improve torsional stiffness.

 

[lobsterCT]

People were wrong! One of the German bike mags had the DVO with and w/o brace on the test rigs for for/aft and torsional stiffness. Result: not much difference.

That was my experience with the fork. Not much difference. I think that was my most regretted bike purchase.

I did an experiment, and crudely added carbon fiber to the arch/leg guard assembly to try to stiffen it.

I tried just a little at first, and with not much improvement, added a little more. Then a little more... I did about 10 iterations, test riding in between each time, and ultimately added about a pound of carbon fiber.

As Canadamos mentioned the small bolts and their torque spec were terrible. If you overtighten them, it cracks the carbon arch around the bolt head. I considered imbedding aluminum so I could tighten the bolts down harder, but decided, an already heavy fork is 1 pound heavier from my carbon, and headed for more if I addressed the bolt situation.

fuck it, I added it to the wall art collection, and got a 40 instead.

Going forward, I would try any inverted fork in person first before buying. Would not gamble.

 

[Electric_City]

Because the lefty had square stanchions

So why don't inverted forks uses them?

 

[Jm_]

So why don't inverted forks uses them?

Because needle bearings are expensive and complicated, why use exotic engineering when you can make a right side up fork even stiffer?
Most companies making or that made inverted did it because its cheaper and easier than cast lowers. Doing square stanchions erases this cost advantage.

 

[norbar]

a bit heavy for bike use

Lighter than my 2003 DNM USD fork by good 300g. Just put it on a square tube turner dhr and you're golden

 

[slimshady]

Because needle bearings are expensive and complicated, why use exotic engineering when you can make a right side up fork even stiffer?
Most companies making or that made inverted did it because its cheaper and easier than cast lowers. Doing square stanchions erases this cost advantage.

Also I think Cannondale had a patent on the square stanchion/linear bearing combo up until recently. X-Fusion tried keyed stanchions with their 1776 inverted SC, but I think it went nowhere.

BTW, I still @bullcrew should get one of those, it doesn't get any more patriotic than that model name!

 

[Jm_]

I think wren still “makes” (as in they import from China) the fat keyed inverted fork. Damping is craptastic tho.

 

[Happymtb.fr]

Going forward, I would try any inverted fork in person first before buying. Would not gamble.

thanks for the late advice!
I did the gamble and got a inverted trail fork. The open bath cartridge and the coil spring are nice but the lack of torsional stiffness is a bit embarrassing... Strangely, I feel it the most during the techy climbs

 

[Lelandjt]

thanks for the late advice!
I did the gamble and got a inverted trail fork. The open bath cartridge and the coil spring are nice but the lack of torsional stiffness is a bit embarrassing... Strangely, I feel it the most during the techy climbs

What did you get? My coworker just put an Intend on the front of his '23 Tallboy that I'm curious to try.
The Dorado Pro on one of my Surrons is my first MTB inverted fork and while I love the fore/aft stiffness and expect the seals to do a better job than the 40 on my other Surron, torsional flex in low speed tech is noticable. At speed I can't say I feel it.

 

[bullcrew]

What did you get? My coworker just put an Intend on the front of his '23 Tallboy that I'm curious to try.
The Dorado Pro on one of my Surrons is my first MTB inverted fork and while I love the fore/aft stiffness and expect the seals to do a better job than the 40 on my other Surron, torsional flex in low speed tech is noticable. At speed I can't say I feel it.

Had 3 dorados come in that I had to clamp the lowers in vice and extract the stanchion from upper ..bent over 1/4 in middle...all on surrons

 

[Jm_]

Monster T

 

[Happymtb.fr]

What did you get?

A Fore from CRconception, an obscure french company that is now gone.
The guy behind claimed that his fork is as torsionally stiff as a Pike. Holding the front tyre between my knees and twisting the bar tells another story. Nevertheless it seems that it is a wrong way to check torsional stiffness since the lever acting from the wheel is not the radius of the wheel but the trail value.

Glad to read that you also find the slow tech to reveal the lack of stiffness. I lost my balance while climbing and felt that the fork twisting back was to blame.

 

[Sandwich]

Man, I thought we already did this. I love the idea of inverted forks, but they just don't work as well for mtb as they do for moto.

I think the only way they would work is to have a 30+mm axle, like the foes did, to combat independent axle movement. You'd still have to deal with fore/aft stiffness which may not be as good, ever, in a weight/stiffness battle.

The lefty worked well because it was a strut, not a traditional fork. It had 4 roller bearings that rode on carriers in between flat surfaces of the slider and fork itself. This limited travel to about 100mm. To get maximum stiffness, they put the bearings right next to the axle, which is why they had the accordion boot. Later they changed it so the bearings are up higher and there's a lower bushing as well. Now they didn't need the boot but I don't know if it was still stiff. I think the last ones had like 140mm of travel. I had a lefty and loved it, but it was short travel and the damping kind of sucked.

Now I have a linkage fork and all my problems are solved

 

[bullcrew]

Just one of the stanchions the rest were like this or a lot worse.

 

[norbar]

A Fore from CRconception, an obscure french company that is now gone.
The guy behind claimed that his fork is as torsionally stiff as a Pike. Holding the front tyre between my knees and twisting the bar tells another story. Nevertheless it seems that it is a wrong way to check torsional stiffness since the lever acting from the wheel is not the radius of the wheel but the trail value.

Glad to read that you also find the slow tech to reveal the lack of stiffness. I lost my balance while climbing and felt that the fork twisting back was to blame.

Do I remember correctly that the owner had some health issues? I know my father befriended him and he always sang praise for his designs. Not that my father knows what a good design was but I was always curious.

 

[norbar]

Man, I thought we already did this. I love the idea of inverted forks, but they just don't work as well for mtb as they do for moto.

I think the only way they would work is to have a 30+mm axle, like the foes did, to combat independent axle movement. You'd still have to deal with fore/aft stiffness which may not be as good, ever, in a weight/stiffness battle.

The lefty worked well because it was a strut, not a traditional fork. It had 4 roller bearings that rode on carriers in between flat surfaces of the slider and fork itself. This limited travel to about 100mm. To get maximum stiffness, they put the bearings right next to the axle, which is why they had the accordion boot. Later they changed it so the bearings are up higher and there's a lower bushing as well. Now they didn't need the boot but I don't know if it was still stiff. I think the last ones had like 140mm of travel. I had a lefty and loved it, but it was short travel and the damping kind of sucked.

Now I have a linkage fork and all my problems are solved

The 140mm lefty was still plenty stiff. I had no comparison with the older one but I had the 140mm C-dale trailbike around 2006 or 2007 and the fork was stiff AF. Especially compared to anything on the market back then. I do agree the damping sucked. The geo on the C-dale was also trash with short TT and long chainstay the thing really did not want to turn.

 

[HardtailHack]

is this a serious question?

Yes, isn't the hex just going to be better for stopping the fork trying to do some sort of radial stuff that it can't really do....?
Also, wasn't Manitou(years back) the company that had issues with cracked bolt up drop outs?

 

[Happymtb.fr]

Do I remember correctly that the owner had some health issues?

I don't know for sure but the company disappeared very rapidly, he stopped answering questions and deleted his Facebook page...

Richard seems to be a smart guy with quite some knowledge about fork, damping and machining. His open cartridges were really well received in France and even abroad. He was doing a lot by himself and I have to say that the quality / finish is not really up to par with the other small suppliers like Novyparts or Fast Suspension.

 

[Happymtb.fr]

Man, I thought we already did this.

I had been warned about inverted forks before but, in a weak moment, my curiosity outrun my reason...

 

[HardtailHack]

I had been warned about inverted forks before but, in a weak moment, my curiosity outrun my reason...

I have really been battling to not buy a Bos Void 3 shock. I know it's a stupid idea but it's been a while between properly frustrating bike parts/companies, so I think it would be a bit of fun reliving the olden days.
Wonder if I could get my old Stoy serviced still? I was too scared of the possible whole year turnaround time when I was using it.

 

[Lelandjt]

Had 3 dorados come in that I had to clamp the lowers in vice and extract the stanchion from upper ..bent over 1/4 in middle...all on surrons

Damn. Bent backward from front end impacts or bent forward/outward from landing hard? Surron kids are hard on their stuff. They expect parts to have the durability of their 1998 CR250. Manitou rates the alloy legged models for non-throttle ebike use, but not the carbon model I use. Interesting that the stantions are the weak point.

 

[Happymtb.fr]

I have really been battling to not buy a Bos Void 3 shock. I know it's a stupid idea but it's been a while between properly frustrating bike parts/companies, so I think it would be a bit of fun reliving the olden days.
Wonder if I could get my old Stoy serviced still? I was too scared of the possible whole year turnaround time when I was using it.

On the french forum I follow, the Bos-crowd seems fairly happy with the service and the time it takes while dealing with Bos HQ directly. It is not cheap but it's fast and quality from what I can read. I haven't read anything bad about the Stoy so far.
I don't know where you are based ? I would deal with them directly if I had a Bos product.
The old Stoy can also be serviced by Novyparts. Maxime was working for Bos when it was developed. He can even change the stroke and e2e if you want.

I would like to try a Bos fork one day, just out of curiosity!