Rear air shock on x57 style strut bike

[Colin]

an interesting shock conversion on this Beast........... for discussion.............



Col.

[orange]

mmm - how have they made that cone I wonder?

[shovelon]

I wonder if the shock end was replaced altogether with a new end with a cone?

[fyrstormer]

It looks like it's just a hollow cone that's press-fit onto the endpiece of the shock. Simple enough. If it were me I'd fill the cone with epoxy to make sure pressure is distributed equally along the entire surface of the endpiece of the shock.

[whisperdancer]

Well, I just asked the seller. I hope to get a reply from him.

[w2zero]

It appears as if there is a fastener going through the shock eye just below the break in the cylindrical part.

[whisperdancer]

Apparently the seller has no idea about the adapter.

Taking a second look, the adapter looks like a sleeve going into the shock body, with a bolt passing through the shock eye.

[whisperdancer]

Anyone thought about using a Magura MX190 rear shock for the conversion?
It almost looks the perfect shock to do this:

- easy access to the valve and adjuster
- no seals, no oil, no stiction - just air



An adapter doesn't seem difficult to do...

[fyrstormer]

That rubber bladder has to flex as the shock compresses and extends. It is just as susceptible to failure as sliding shock seals are -- possibly more so, since it has to change shape as the shock operates. If sliding seals didn't work as well as they do, I'd say the Magura/AirShok design would be worth considering, but sliding seals DO work well. Might as well go with the technology that's had the most R&D work done with it.

[w2zero]

large trucks have bazillions of miles on very similar rolling bag suspensions

[whisperdancer]

As for reliability, I don't have a single doubt it will work. As said, trucks and buses use this, and the extremely reliable BMW bikes also use these shocks (also made by magura).
The problem is I think the shaft won't rotate by 90º, as it would also rotate the rubber, unless the rubber sits on a groove...

[fyrstormer]

Yes, big trucks and buses use that kind of suspension, but they have regular service intervals and steel mesh inside the bags to strengthen them. This being a bike shock, it's expected to be much lighter weight; Kevlar might provide sufficient strength without being heavy, but I don't know for sure.

Anyway, just because the technology is well-developed for large heavy vehicles, that doesn't mean it's similarly well-developed for bikes. Pretty much every single things that's been carried over from MX to mountain bikes has taken years of industry-wide development before it's worked well. The first hydraulic disc brakes were either enormous and heavy because they were basically MX brakes with smaller levers and discs, or they were light and weak because the reverse-engineers hadn't figured out yet where it was safe to shave off unnecessary material. It took about 7 years before disc brakes for mountain bikes hit on the right mix of characteristics, and that was with every major player working on it. Magura is alone in making this design for bike shocks, as far as I know.

Why risk using a non-standard design? There's no meaningful benefit over sliding-seal shocks, because even inside that rolling bag there still has to be sliding seals for the oil damper. It seems like a gimmick to me, nothing more.

Then again, I've been burned by non-standard suspension designs before, so maybe I'm once bitten twice shy.

[w2zero]

From the Magura site

<<Absolutely mainteance free | No oil, no seals exposed to pressure.
The regular yearly service is a thing of the past. Pure riding pleasure instead
of costly service intervals that prevent you from riding your bike.
Super simple | Easiest setup, automatic adjustment to individual rider weights.
Setup nightmares are a thing of the past with the MAGURA MX.
Lightweight | The version with a length of 165 mm (38 mm travel) just weighs
195 g/0,43 lbs. Also available in lengthes of 190 and 200 mm (50 mm travel).>>

Soooo, and I quote you fyrstormer "Why risk using a non-standard design? There's no meaningful benefit over sliding-seal shocks, because even inside that rolling bag there still has to be sliding seals for the oil damper. It seems like a gimmick to me, nothing more.

Then again, I've been burned by non-standard suspension designs before, so maybe I'm once bitten twice shy."

And yet, you ride a proflex...

[whisperdancer]

It seems the shaft can be rotated by 90º, so it's a plus, as being extremely sensible to small bumps more like a spring shock than an air shock.

However, it doesn't seem to fit (here in my spare K2 1000 frame - highlighted tops for better view):




Or maybe it does, like all the aftermarket adapted shocks. I'm still considering if it's worth the try (around 160€ shipped plus customs)...

PS: that NR4 is busted. Maybe sending it to Noleen J6 is a better option... But then again, oil and maintenance... 

[fyrstormer]

From the Magura site

<<Absolutely mainteance free | No oil, no seals exposed to pressure.
The regular yearly service is a thing of the past. Pure riding pleasure instead
of costly service intervals that prevent you from riding your bike.
Super simple | Easiest setup, automatic adjustment to individual rider weights.
Setup nightmares are a thing of the past with the MAGURA MX.
Lightweight | The version with a length of 165 mm (38 mm travel) just weighs
195 g/0,43 lbs. Also available in lengthes of 190 and 200 mm (50 mm travel).>>

Soooo, and I quote you fyrstormer "Why risk using a non-standard design? There's no meaningful benefit over sliding-seal shocks, because even inside that rolling bag there still has to be sliding seals for the oil damper. It seems like a gimmick to me, nothing more.

Then again, I've been burned by non-standard suspension designs before, so maybe I'm once bitten twice shy."

And yet, you ride a proflex...

The only non-standard thing about *my* Pro-Flex is that the lower shock boss bolts to a strut instead of a pivot, which is of minimal significance. I tossed the Girvin fork as soon as I had the money to get a Manitou SX-R (and later, a Black Super) fitted in its place. I also got rid of the rubber-spring rear shock in favor of a coilover, which was such an urgently-needed upgrade that I bought a $300 Noleen NR-2 back when I was earning next-to-nothing bagging groceries in high school.

There's no oil in that Magura shock? Then what provides the damping? If there isn't fluid damping, there must be either air damping a-la Cane Creek (which doesn't work well since air is a compressible fluid) or friction damping, which will wear out eventually.

I like Magura's brakes, but any time a company claims something requires no service, you can be assured they're BSing you. EVERYTHING requires service for optimal performance, even if not for bare-minimum performance.

- - -

I wanted to quote some reviews to back up my PoV, but I can't find any. All I could find was this: http://forums.mtbr.com/shocks-suspension/magura-mx-air-damped-shock-what-happened-581722.html

Everything else I found was dated 2007-2008 and was just previews of the then-upcoming product. The last update stated the MX would be OEM-only, which usually means the product has been determined to be inferior quality and can't compete with existing aftermarket products.