Issues with - K-Tech Razor-R Rear Shock

[clint]

I hate to write a review like this, but it truly is deserved. After reviewing the merits of rear shocks, I chose to buy the K-Tech Razr-R and it has promptly been returned without even mounting it! 
 
Here's a picture of what I was expecting. 

This is what I got!

 
That's right, due to the length of the shock body and their decision to use a 6" spring, preload adjustment is maxed out AS-IS! +- 3mm is what you get according to them....REALLY!?!?! Pretty much NO WAY to set a proper sag. Seriously gentlemen, throw this one back to the engineers and tell them to pull their heads out of their arses!!

[Brick]

Oops!

[bruceintucson]

+ or - 3mm of adjustment?! Wow, someone sure had their head up their A$%.

[betoney]

Have you already contacted them to allow them to try and make it right? or to give you an explanation?

[clint]

Have you already contacted them to allow them to try and make it right? or to give you an explanation?

Absolutely! I've been working with @pattonme throughout this whole process and he's been my liaison to the K-tech representative. BTW - working with @pattonme has been amazing! I've seen the emails he's exchanged with the Rep, and he's extremely knowledgable with all things "suspension". If I choose to purchase ANY of the shocks that he is a vendor for, I wouldn't hesitate to use him again. Exceptional knowledge, service and price. BTW - there are even more issues with this shock than just the lack of preload that I just won't go into. But rest assured, pattonme has called them out on all of them.

[xlxr]

Is the problem is they sent you a spring that is too short? Replacing the spring should be easy enough.

[clint]

Is the problem is they sent you a spring that is too short? Replacing the spring should be easy enough.

It's a bit of a long story, but yes, they were given that opportunity. The choices they made in several areas in the build of this shock were just wrong (lack of torrington bearing, etc). Even if the spring were longer, pretty much all of the adjustment would have to be made on the TOP base ring which is inaccessible when mounted. I believe they took an existing shock from their catalog and turned it upside down for use on the FJ-09 which provided for only 3mm of adjustment.

[betoney]

Clint
Sorry to hear of all of your troubles with the shock. Glad to hear that Matt is helping you out as a liaison. There is nothing worse than getting your hopes built up and then being let down once you get the product in hand. Traxxion Dynamics is currently building me a Penske and I feel like a kid anxiously waiting for Christmas morning.

[pattonme]

I'm coming off 23hr straight hours at my day job so I won't make this too long.
 
I want to preface this by saying I reached out directly to K-Tech in UK and have exchanged a couple rounds of emails. The last note was a little terse and I hope the language ("you're 100% right. I'm forwarding everything you wrote to the design department") was not just to make me go away. But it would seem I'm not the first to raise issues with the design and FWIW a remote preload adjuster is in the offing, as well as other unspecified improvements. Timeline to be determined.
 
"Do not buy" is a bit over the top, IMO but @clint is well within his rights to declare it unsuitable for his purposes. I hadn't seen a FZ09 application in the flesh (just FZ07) and the website is just stock photography so until he sent the unit back to me I didn't realize the extent of the design shortcomings. I think I've sold something like 6 K-Tech shocks to date and folks have been happy with the damping performance so at least that team appears to be on the ball.
 
Some background.
(12/20 Edit: Apparently I had some incorrect information. The DDS/lite series is a 36mm twin-tube configuration.)
 
AFAIK, K-Tech is unique in taking the small diameter (36mm piston) shock body from their 'twin' series and using it as a 'single' in applications like the FZ07 and FZ09, R3(?), and Ninja 300. By twin, think Harley, ZRX, other UJM standards, classic-look Triumphs, Guzzi classics and so forth. Everybody else uses a 46mm piston shock with it's larger body and "industry standard" 2.25 inch main spring combination.
 
Twin shocks use smaller springs for obvious reasons and by virtue of there being 2 units working together spring rates are around 30-60N/mm on each side. Said springs actually tend to be pretty long (7-9"). But for FZ07 duty the spring needs to be in the 110-140N/mm range and for the FZ09 95-125. This means a much beefier coil and limited length. K-Tech elected to have the high rate units wound in 6" length across the board. Ohlins just so happens to have the full spectrum of rates for the FZ09 in 7" length but nothing in the FZ07's range at any length (caveat my spring catalog is a couple years old).
 
So to answer the question posed: no, there are no longer springs available from K-tech.
 
I'll address the matter of preload range a little bit later and deal with the simpler topic of adjustment difficulties and poor follow-thru in design.
 
As a 'twin' the shocks sit fully outside the bodywork and frame members and getting access to the lower or upper rings is really quite trivial. When that same arrangement is put centerline, then tommy bars and general access is significantly/severely hampered. K-Tech supplies a pair of 4mm diameter tommy bars, what others called a pin punch and that's a perfectly accurate characterization. Punches are hit from above and so their spindly nature isn't in issue. One would NOT, however, try to use a pin-punch to induce torque into a ring and clearly not if the 4mm diameter shaft is a full 40mm long! I know of at least 2 if not 3 cases where people have broken the tool and I very nearly did so myself! If one were to use a tommy bar then clearly the correct solution is to make the narrow shaft portion only as long as needed to get good purchase in the hole; in this case 7mm. One can also take out an easy inch from the 4" long 'handle' to make things easier in tighter quarters.
 
Their choice of tommy bars aside, if you're trying to spin a preload ring and there's a lot of spring pressure on it (more so if the bike has no center-stand and thus resting vehicle weight is compounding the problem) one would use some kind of hook/pin wrench like we're all familiar with. The diameter of the rings are smack in the range of common industry tools: 55-63mm but in pin guise the "standard" is a 5mm pin, not a 4mm. All they had to do was make the primary ring 7mm thick instead of 5 and the hole would have fit. I guess they were going for "thin is sexy".
 
Furtherance to the choice of ring size and design, the OD is again perfect for an ER40 collet wrench which comes in 3-tang or single. Now an ER wrench is pretty damn long but they do make sideways versions and shorties which would be the kind needed for a center-line shock. Having 3 points of contact on a ring would be HUGE. I don't know about you but I've royally skinned my share of knuckles. Also most other shocks the rings are ~same diameter as the OD of the spring for most surface area. Theirs are smaller by 3mm on each side, or 6mm total. Why? Probably because they wanted to machine it from 2.5" round bar instead of having to go up to 3".
 
They make Torrington's for 1.8" ID springs (what this is) but the OD is likely to be the full diameter so K-Tech's ring would be only covering half of the roller length. To this "I stayed at a Motel 6" engineer it seems patently obvious that the main ring should have been made to full OD, and about 10mm thick in the vein of Nitron and in particular Penske where they employ a "bent rod" of ~6mm diameter to swing the ring around. A flat-tip set screw would have made sure it stayed put.
 

[Brick]

pattonme I'm glad your reply was short. ?? Thanks!

[bruceintucson]

Clint, et al. Just went and looked at my Penske on Mary's FJ-09. It also has a 6" spring and probably only + or - 5mm of preload adjustment at the bottom of the shock. The big difference (on top of the fact as Matt mentioned that it is the correct larger diameter normally used in a single shock application) is that the [em]entire[/em] shock body is threaded and with the preload rings Penske uses (and the tool they send), it is pretty easy to get to the top spring adjuster ring and turn it. In fact, although the preload from Traxxion/Penske was pretty spot on, the lower preload adjuster (with the Torrington bearing supplied) was wound up to maybe 80% of it's available preload. So I backed the lower adjuster off 3 turns & added 3 turns to the upper adjuster ring; putting the lower adjuster ring more on the soft end of it's adjustment scale. This permitted still being able to go slightly softer and considerably harder for luggage or a passenger (though she never rides two up). I consider the lower adjuster the fine-tuning adjuster and the upper adjuster the course-tuning adjuster.

[pattonme]

Now I'll address the preload range. I believe it's reasonably accurate to say shocks are commonly shipped with 8-10mm of preload in the system. From there, a person light for the spring rate might take 2mm out, and heavy for the rate could add another 5 maybe even 10mm once you add the bags and pillion.
 
This is a contrived example that assumes a linear relationship. I think I'm doing it right, but take with skepticism. Let's say 90Kg rider + 205kg bike, 60% rear weight bias = 295 * .6 = 177kg weight applied to the rear axle. Let's say the 10mm of factory preload yielded 30mm rider sag. I now add 70kg most of which by virtue of where the passenger is in relation to the rider (let's say 1.5x as far from the fulcrum) applied to the rear and becomes 105Kg equivalent. I would need 10mm more preload to get back to 'zero'. Or more practically we'll suck up say 5mm in shaft displacement (total sag is now 30+5*2.5=43mm) and add the other 5 to preload.
 
The point being it's not unreasonable to want to add at least 5 and maybe 8mm+ of preload to a shock from baseline.
 
The lower threaded portion of the shock is 24mm long. With the upper ring at it's lowest most bound, the first (we'll ignore the 2nd lock ring) silver ring sits just flush at the bottom of it's section and provides ZERO preload. Basically all we've done is take up the slack. QED *all* of the 10mm of desired factory preload now has to come out of the 24mm section. But since the ring itself is 5mm tall (plus 4mm for the spring centering lip but doesn't count), our 24mm section is effectively only <19mm long.
 
So in other words, having cranked in 10mm to achieve baseline there really is 8mm more available and even at negative 5mm still lets you fit the lock ring on behind the primary. Does it look right? No it does not. It just screams 'wrong'. Now if you were to use a Penske-like 8-10mm thick single ring you would start off with some threads hanging off the bottom at zero slack but no biggie.
 
IMO K-Tech should replace the lower silver ring pair with a 1-piece that lends itself to EASY rotation by combining a torrington with a meatier and more sensible tool. In fact, I would just re-use the upper ring, flip it over for lower duty with the proviso to lose the scallops and instead use 5mm pin wrench(meh), slots for an ER40(+), or maybe better the 6mm 'bent rod'.
 
For the sake of "doesn't look wrong" and not needing to add 7" springs to the SKU just for the Fx09 series or other 320-330+mm long shock applications, I might machine a 20mm long spacer that nests into the lip and spring. A slip-fit over the upper body threads would keep the tool paths simple.

[fj09chris]

This sure makes adjusting spring preload easy...
 

 

[oxracing]

I would like to correct a few misconceptions that have been discussed regarding the Razor R shock.
 
Unless modified or adjusted after leaving the factory the Razor R shock does allow up to 10mm of preload adjustment.For access to the adjusters on the FZ/FJ09 models the adjusters are located at the lower end of the shock. The Razor R shocks are by design purposely fitted with the shock body chassis mounted and not a retrofit of some other design. Likewise the 35mm body when properly designed is more than adequate at premium performance (Ohlin's top shock the TTX36 as an example). 6" springs are also a commonly used spring length for this application and K-Tech does offer a wide range of rates for specific fitment. Regarding 35mm shocks suitability, K-tech's 35DDS Pro series shock has years of proven success's under extreme conditions at the highest level of professional racing.
 
The Razor R has been widely accepted as a great shock with no other shock I am aware of offering the same features anywhere near this price range. Recently did address the earlier style adjusters and recently began supplying the Razor R shocks with a more robust preload adjuster and tool.

[clint]

I just received a very cordial personal message from Oxracing regarding the issues I had with my purchase. Great guys who seem to be willing to make things right with their recent modifications to the shock preload adjusters. Unfortunately, I'd already chosen to go with a different product. Hopefully someone else will buy and confirm that K-tech's new setup on this shock remediates the issues.