Rocky Mountain Altitude 50 (2009) – Review

Pro Reviews


This next section describes RMB’s SMOOTHLINK™ Suspension, a design based on RMB’s ETS patent. Useful links are referenced below. I am not, and have never pretended to be an expert on suspension design so this next section is almost entirely based on materials provided by RMB and from discussions with RMB’s engineers. I’ve decided to include this lengthy, technical exposition because there appears to be interest about the Altitude’s design and some speculation about whether or not RMB has successfully produced a design that does not infringe the Horst Link and ICT patents.

  • Horst Link Patent (Horst Leitner – US 5,509,679 – now owned by Specialized Bicycles)
  • ICT patent (Tony Ellsworth – US 6,378,885 – owned by Ellsworth)
  • ETS patent (Duhane Lam – US 6,843,494 – owned by RMB)
  • Some speculation by Feed the Habit is contained in the article (“Horst Link or Not“).

I asked RMB’s engineer to put some thoughts together on this topic and asked for, and received permission to put some technical notes in this article.  The engineer’s thoughts are as follows:

The Patent number is US6,843,494. This is the patent for the ETSX bicycle, issued in Jan 2005. In short, the ETSX patent places the lower pivot above the rear axle at all points of travel, whereas the Horst Patent places the lower pivot below the rear axle at all points of travel. It is my assumption that the original Horst patent was written as such because Mr.Horst did not think that a pivot point could be placed above the axle, since the chain is in this position when in Cog 1. With our placement of the lower link, it is now parallel to the tension side of the chain, and thus follows the Instantaneous Center of Rotation (ICR – VPP, whatever you call it) more closely, than the Horst design (which is at an acute angle to the tension side of the chain).

All pictures below are excerpted from RMB’s presentation entitled “Altitude and Vertex Media – NA” and reproduced with permission. Italicized text is from the RMB presentation. My subjective comments about the suspension’s performance will be contained in the section of this review where I discuss the performance of the bike.

Extension of Energy Transfer System (ETS™) patent.

This new suspension configuration is defined by the ETSX patent (US 6,843,494). As well, there are additional patents pending which pertain to the manipulation of the rearward pivot, which utilizes a novel step-down drive-side clevis: it allows the lower drive-side stay member to avoid contact with the chain at all times. The ETS patent stipulates that a line drawn through the main pivot and the rearward clevis pivot is always above the rear axle at all points of travel. See Figure 1.

Smoothlink Detail

Tuned linkage follows chain force vector, eliminating pedal bob.

The lower linkage member is almost parallel to the Average Chain Torque Line (ACTL), at all points of travel. This allows the Instantaneous Center of Rotation (ICR) to follow very closely to the ACTL, thus practically eliminating pedal induced suspension bob. See Figure 2. NOTE: the ICR never crosses the ACTL at any point in travel, as this would be considered “tracking” as defined by a competing patent. (US6,378,885)

Instantaneous Centre of Rotation (“ICR”) and Average Chain Torque Line (“ACTL”)

Minimal chaingrowth creates fully active system.

The chaingrowth has been reduced by half (now only 8mm through 140mm of travel) in order to create a more active suspension feel, while still maintaining the traction and forward drive created by the ETS™ effect. It is ideal to have the rear wheel trajectory shape be as closeto a circle as possible, as any deviation from a perfectly circular path will introduce an irregular rate of change between the bottom bracket and the rear axle as the rear wheel compresses. Should the Chain Stay Length (CSL) grow at such an irregular rate, the bike would be more difficult to control when the rear wheel is weighted. See Figure 3.


Flatter suspension rate creates bottomless feel, low air pressure system.

The Altitude has a more level Instantaneous Suspension Rate Curve than its predecessor. This flatter curve, in combination with a 6.5mm longer stroke shock, will allow the suspension a greater degree of movement through the travel than the ETS-X, thus producing a more “bottomless” feel. Also, less air pressure will be required in the Altitude shock absorber than the ETS-X because of the higher initial rate value. See Figure 4.

Suspension Rate

Caliper mounting position reduces Brake Jack.

By removing the braking forces from the lower linkage, they are isolated and do not act on the suspension system, thereby greatly reducing “brake jack”, or the stiffening of the suspension under braking. The slight change in the angle between the caliper and the lower link creates a “floating disk brake” effect.

About the author: Lee Lau

Lee Lau calls North Vancouver and Whistler BC home. He's had over 15 years experience riding bikes mainly in western North America and in Europe. Unlike many people who learned to ride bikes on North Shore trails, he actually enjoys riding (and sometimes bushwhacking) uphill.

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  • leel says:

    FYI – I’m in the process of trying to get some approximate pricing for the bikes as built for the North American market and will edit when I have this information. I didn’t know if I could get pricing so thought it best to publish this article and update with pricing for later.

    This is pricing from the feedthehabit article linked to in the review. I’m trying to confirm the pricing

    2009 Rocky Mountain Altitude Specs

    Frame, Trim Levels and MSRP (USD)
    Altitude 30 – $2849
    Altitude 50 – $3499
    Altitude 70 – $3999
    Altitude 70RSL Carbon – $4899
    Altitude 90RSL Carbon – $6499
    Altitude 29er – $1599 (single-speed) or $1999 (geared)
    Altitude Ladies 50 – $3499

    Here is Canadian pricing from Rocky Mountain

    Altitude 30

    Altitude 50

    Altitude LO

    Altitude 70

    Altitude 70 RSL

    Altitude 90 RSL

  • Yo… cool to see some rider feedback on the new Altitude platform. I’m looking forward to riding one at Interbike next week! The pricing you show (quoted from my article on was given to me directly from Rocky Mountain, so it should be fairly accurate. Of course, like anything, prices are subject to change.

  • yeahboyeee says:

    The bottom of the downtube looks ridiculous and the tire clearance inadequate. Saving my money for now and hoping they look after these in rev. 2

    Pretty sweet to see them develop a nice 4-bar and essentially throw up a middle finger toward the big red “S”!

  • EGF168 says:

    Thanks, you told us exactly what we wanted to know and that’s one of the best thought out reviews I’ve read in a long time, oh and the pics were very helpful too, it looks a lot nicer in the pics than I thought it would.

  • leel says:


    - Prototype frame’s egg-shell white colour is a one-off. The production frame will be the brighter white depicted at the end of the review.

    - Production frame to be changed to have more tire clearance so a 2.5″ will definitely fit

  • taprider says:

    I like the effort to put the waterbottle inside the main triangle – very important for epic rides to have both camelbak and bottles, and for races like BC bike race it is way faster to use bottles than bladder.

    I like low bottom bracket for better handling and more stability. Striking pedals is not a big deal if you have some skill. 1 cm lower makes a big difference for feel, handling and stability, but makes negigible difference as to whether you strike a pedal or not if you are skilled.

    I like Rockies forward facing seat tube clamp, since it is easier to drop saddle while riding, and the seatpost can be marked in the keyhole cutout and remain visible (marking seattube above clamp weakens post)

    Don’t like bent top tube. Clearance is over rated. I’d rather have long flat surface for long portages. I like the classic look of original Rockies and in the case of Elements I like the ability to have two water bottles.

    Really don’t like bent down tube and the possibility of crushing it.

  • islander says:

    Quality review Lee. Glad to see you took it up on a few epics. For me, the shore-worthiness of a bike like this is a bit of a moot point. I say RMB should focus on the bottle mount(s) and as taprider suggests – stuff like ease to shoulder it etc (I agree standover is overrated in this category). No doubt, this is an improvement over the busy ETS platform. Would be great if RMB would issue a Special Edition with some more traditional paint we’ve long liked from Rocky.

  • Cory says:

    I spent a few hours on the Altitude this past weekend and posted up my thoughts in the Rocky Mountain forum.

    The Altitude is definitely a nice-riding platform.

  • G RANT says:

    Sure is neat, unless I skimmed it, that rear wheel travel is not mentioned. Is it me, or is that something that is important?

    Maybe I’ll check out pinkbike. They can tell me I’m sure.

  • leel says:

    You know, I can’t believe I forgot to mention the rear travel. D’oh! It’s 5.5″ Thanks for catching that.

  • Lee Lau says:

    Interesting post by Johnny Rockall of RMB about the Straight Up Geometry

  • Radam says:

    Great review! I’m in the market for a 140mm epic bike and I’m adding this to my short list.

  • SingleTrak says:

    I’m a proud owner of the retired ETSX-50. Why? Altitude? Bottom is awfull. Adjustement on the front fork is lost. Makes no sense…

  • Rocky Rider says:

    Great report! Thank you very much. What frame size was your test-bike? Would you (your size is 5′ 10″, right?) choose 18 oder 19,5 frame?

  • LeeL says:

    Sorry for the late response Rocky Rider. I was on an 18″ bike. I am 5′ 10″

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