Headshok reborn? RST suspension forks...

[Rick Johnson]

Now that most of the Cannondale Headshok patents have expired I suppose this was just a matter of time...

http://www.rst.com.tw/en/ProductInfo.aspx?PID=44

http://www.cyclingdeal.com.au/buy/bike-suspension-fork-700c-v-or-disc-brake/12530503

http://www.bikerumor.com/2016/03/08/tpe16-rst-carbon-fork-takes-grind-gravel-ride-plus-rebel-inverted-fork-elev8-dropper-updates/

https://www.rosebikes.co.uk/article/rst-m-7-single-shock-28700-c-suspension-fork/aid:399514

http://www.rst.com.tw/en/product.aspx?CateID=72

Rick Johnson
Bend, Oregon

Every revolutionary idea seems to evoke three stages of reaction...
One, it's completely impossible. 
Two, it's possible, but it's not worth doing. 
Three, I said it was a good idea all along.

Arthur C. Clarke

[Jeffrey Kane]

Rick,

I love how you dug this out in light of the other thread that touched on the old Cannondale Silk Roads ... that said: am I reading this right that the clearance is spec'd for just 28 ?

And no -- I have no horse in the game having switched to road-geo 650b x 42 bikes years ago -- and being solidly stuck in the middle of NYC don't find myself needing / wanting 48 (+) multi-sized disc wheel thru-axle options too often --- but I've enjoyed watching all the road plus developments (and arguments)1

[Scott Henry]

Here is the link to all the single shock (headshock) forks from RST
http://www.rst.com.tw/en/product.aspx?CateID=72
You will find some with wider clearances.

I've never ridden one of these SunTour forks, but they have always seemed interesting to me.    Plus you can sometimes find them super cheap on eBay
http://www.srsuntour-cycling.com/bike/forks/SwingShock-Swing-Shock-700-4982.html

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[satanas]

Some of the forks look interesting, though a dedicated frame would be needed due to the length. Where did you guys find tyre clearance info? (I couldn't see any.)

Thanks,
Stephen

[Rick Johnson]

Jeffrey,

It was the recent thread that got me motivated to do a little more digging in Silk Road history. That is how I stumbled across the RST products. The very last link I included (the one Scott resent) takes you to the RST catalog. Unfortunately there is a frustrating lack of information on the tire widths the forks are intended for.

Using some quick-and-dirty scaling it looks like the SS-A7 is about 58mm wide at the point indicated below:



For more a "gravel riding" focus (and presumably more tire clearance) the Bikerumor post includes this teaser about what to expect for next year:
"The carbon A7 Gravel fork (above) stands far out past their other single-shock forks being that it’s carbon, uses the light and increasingly popular 12mm thru axle, will be available with a tapered (or straight) steerer, and will boast a sizable 50mm of travel. The target weight they’re shooting for is around a kilo (1000g/2.2lbs). It has a simple pre-load adjust and is oil dampened. There is no lockout but I suppose cranking it down will be a simple and effective way to hold it still."
"Disc brake only; I noticed some unusual mounts on the back of the non-brake side fork blade. Turns out, like on their trekking forks, the mounts are designed to run a wire for a dynamo hub to your lights. Without even having to ask why, I thought this was a nice addition for just a few gram trade-off. No information on price, availability, or final axle-to-crown measurement as this was their very first functional prototype."
http://www.bikerumor.com/2016/03/08/tpe16-rst-carbon-fork-takes-grind-gravel-ride-plus-rebel-inverted-fork-elev8-dropper-updates/

One significant seller of these RST forks seems to be an eBay store called "Mr Ride Bicycle". Many items appear to be warehoused in Hillsboro Oregon. I may explore the possibility of tracking down the seller the next occasion I am over that direct to see if there's a possibility of examining these forks in person.

Rick

Rick Johnson
Bend, Oregon

[Stephen Poole]

One of the links posted is for an Oz seller I've dealt with before and the fork they have is relatively cheap; I'm tempted to order one to have a look. The CF one weighs nearly 600g less though, assuming it ever becomes available.

I might shoot off a message to the Oz guys and ask them to check what size tyre will fit the fork they have.

Later,
Stephen

[William Lindsay]

It's kind of a tangent, but there's also this Lauf-Grit fork:  http://www.laufforks.com/lauf-grit/

It's about $1000 for the fork, it's all-carbon, and it has 30mm of travel with zero moving parts.  It weighs 900g.  I would LOVE to test one out.  It's obviously disc only.  

[Alex Wetmore]

No rebound dampening of any sort.  The online reviews seem pretty mixed as a result.

alex

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From: 65...@googlegroups.com <65...@googlegroups.com> on behalf of William Lindsay <tape...@gmail.com>
Sent: Friday, May 6, 2016 11:09:49 AM
To: 650b
Subject: Re: [650B] Re: Headshok reborn? RST suspension forks...

 

[William Lindsay]

Yes, but think about it.  Tires don't have any rebound damping either, and we like the many benefits of wider tires, including the suspension enhancement.  A rigid fork has no rebound damping either, and we like the many benefits of nice compliant skinny fork blades, don't we?

I suspect the less positive reviews are from people who want that fork to behave like a mountain bike suspension fork.  That's why I want to ride it.  I want it to behave like a super compliant road fork.  

I'm not ready to pay $1000 for the test ride, though.  

Bill Lindsay

El Cerrito, CA

[Alex Wetmore]

No rebound dampening with 50mm of travel is very different than no rebound dampening with <5mm of travel.  

I have also found very wide (RTP wide) tires to be prone to bouncing, and it takes careful adjustment of the tire pressure to keep them feeling good.  

I think we can get away with no rebound dampening on small travel suspension, but there are limits to what works.  This design would probably be more interesting to me if it were for a 10mm travel fork.

alex

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From: 65...@googlegroups.com <65...@googlegroups.com> on behalf of William Lindsay <tape...@gmail.com>

Sent: Friday, May 6, 2016 11:49:04 AM
To: 650b
Cc: tape...@gmail.com

Subject: Re: [650B] Re: Headshok reborn? RST suspension forks...

[eric moss]

I wonder if a Moulton "Flexitor" fork could be made for 650b.  They are pretty great for the 20" wheels.

[William Lindsay]

I don't know exactly how we got onto a 50mm fork.  The Lauf-Grit that I linked has 30mm, but whatever.  

I think you are absolutely right that there is probably a limit.  The mechanical system that I have experienced with a LOT of travel and practically zero damping is called a trampoline.  :-)  If that fork acts like a trampoline, that probably would not be good.  

Again, I'd like to ride one, because I don't know whether I would like it or not.  Are you saying that you already know that you don't like how it rides?  Like, your mind is made up, and you wouldn't even want to try one?  Or are you just saying that you probably wouldn't like it?  I'm not being contentious, I just really respect your opinion, and if you say that you know for a fact that it's lame, then that's a strong vote in my book.

Bill Lindsay

El Cerrito, CA

[Fred Blasdel]

On Fri, May 6, 2016 at 11:49 AM, William Lindsay <tape...@gmail.com> wrote:

Yes, but think about it.  Tires don't have any rebound damping either, and we like the many benefits of wider tires, including the suspension enhancement.

This is where Jan's theorizing starts to get off into the weeds

Tires *do* have rebound damping, adjusted mostly through the compounding of the rubber. Softer durometers generally have slower rebound, but there's a lot of mysterious tuning that can be done. They have compression damping too, adjusted through the structure of the casing.

That's all well known in the world of aggressive mountain biking, where stiffer sidewalls and slower rubber are sought after for their advantage in control, letting you ride much faster.

[William Lindsay]

Fred

Do you have any numbers to share?  Whats the damping coefficient of a "stiff sidewall soft rubber" mountain bike tire?  and how does that compare to the damping coefficient of a supple tire, like the Rat Trap Pass that Alex reported can be too bouncy?  I remember the units of the damping coefficient is newton seconds per meter.  Do you have any values?  It's super interesting

Bill Lindsay

El Cerrito, CA

[Steven Frederick]

I'd try it. And I just might! They have a 4-week satisfied or return
policy. Not available til August, tho, according to their online
store...

I put a set of standard casing Switchback Hill tires on my
Quiring--set up tubeless on Pacenti rims--last week and rode it all
weekend. Not much more compliance at 28/30psi, really-may try lower
pressure, but better traction and a lot faster than I expected on both
dirt and paved roads. Rough gravel roads made me think a bit of
suspension a'la the C-dale Slate or this Lauf thingy, might not be
such a bad idea.

Steve