Introduction
Rocky Mountain Bicycles (RMB) will be resurrecting a venerable name from history when they release the Altitude in 2009. A marked departure from the racing-light steel hardtails that formerly bore the name Altitude, this new Altitude is described as a trail bike that keeps its wheels on the ground for "epic cross country".
RMB provided me with a prototype Altitude aluminium 50 frame for review. The Altitude is slated to replace the ETS-X in the category which RMB calls XC Marathon and what other manufacturers loosely refer to as "all-mountain". It will be produced in an aluminium version and in a (lighter, higher-end spec and more expensive) carbon version. As the Altitude is further refined to a production frame with a production spec, some details of this review may be redundant (I'll highlight those details further in the review) so I urge the readers to also check the RMB website which should be considered to be authoritative.
I'll note at the outset that I am reviewing the frame and NOT the components. My bike was built with a heavier-then-stock package for riding the Downieville downhill course. Although it is difficult to separate the bike from its parts, I will do my level best to confine my remarks to the performance of the frame. Because there is currently a paucity of information about the Altitude, I will be excerpting from a RMB presentation about this bike in lieu of my standard practise of directing readers to a website. I'll then present my general impressions about this frame's performance.
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Whistler Alpine
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South Chilcotin ~ photo Mark Rowe
Reviewer's biases
I am 155 lbs and 5' 10" and have had over 15 years experience riding bikes in North Vancouver, Squamish, Whistler, the Chilcotins and many other areas in B.C. and Alberta. I've also made many bike trips to other places such as Utah, Washington, Oregon, California and Ontario (for example) so have had some experience biking in a variety of terrain. My bias is towards pedalling up and unlike many people who learned to ride bikes on North Shore trails, I actually enjoy riding (and sometimes bushwhacking) uphill.
I rode this bike over a period of two weeks in a 4 day trip in the South Chilcotin and a few day rides in North Vancouver, Whistler and Squamish. As a frame of reference I have enjoyed riding and have owned and/or tested the following bikes listed below (links to previous reviews I have written are provided:
![]()
Gun Creek Ranch, South Chilcotin
![]()
North Vancouver ~ photo Sharon Bader
Frame highlights
As previously mentioned, the Altitude will replace the ETS-X. Design highlights of the Altitude include; SMOOTHLINK™ suspension; STRAIGHT UP™ geometry, swooping top tubes on the front end for low centre-of-gravity and increased standover, swooping down tubes for shock piggy back and water bottle clearance, 7005 aluminium frames utilizing RMB's FORM™ design and on higher-end lighter framesets - C12 carbon monocoque frames (rocker links, front end main frame and seat stays).
I'll expand more on these above concepts further in the review. Note that the carbon frame is outside the scope of this review so that is all I will mention in this matter. Please check the RMB site for more information on the RSL (Racing Super Light) carbon framed Altitude 70 and 90
![]()
South Chilcotin
Frame material
As expected, the Altitude's welds are clean. The paintjob on my prototype bike is a nice eggshell white that seems to shed mud very well. The production bike colours will be more of a bright white colour as depicted in the pictures at the end of this review. The aluminium tubes are designed in a process that RMB calls FORM™. All tubing on the Altitude is custom-made, drawn from 7005 alloy then cold-worked. Every tube is fully butted.
The Altitude incorporates a large hollow head tube area in an effort to increase stiffness. Also of note is the incorporation of aerodynamic leading edges - not to decrease wind resistance but to aid in deflecting rocks. Unfortunately in many of these pictures I put a mud splash guard on the down-tube to help forestall rock damage.
![]()
Front End - noting the large head tube and the elliptical leading edge of the down tube with stylish zip-tied mud guard
The Altitude's seat tube is butted and hydroformed. Note in the pictures below that the centre section of the tube is bulged. By bulging the centre section, RMB eliminated the need to weld on a rocker mount, opting instead for a stronger piercing for the oversized rocker link pivots. The rectangular bias in the seat tube is an effort to also increase stiffness.
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Rear linkage - non-drive side
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Rear linkage - drive side
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Rear drive-side - note the assymetric chain stays
The swooping bends in the seat tube and down-tube are apparently not motivated purely by fashion. According to RMB, the down tube shape was necessary in order to keep the shock (and centre-of-gravity) as low as possible in the frame, and also in order to create enough room for a water bottle in all frame sizes. The down tube shape also allows the rider to run a shock with a reservoir.
Since the Altitude frameset is so well thought-out it was with some relief that I felt I could do my "job" as a reviewer and point out some possible negatives. The water bottle placement mounts do not allow a shock with a piggyback reservoir to be run as the reservoir would impact the water bottle. I am told that RMB will be correcting this in production frames.
![]()
Water bottle mount placements will be moved forward in production frames
Under certain circumstances, when approaching technical obstacles (the up and over log-pile in the picture below being a perfect example), the downtube kink on the frame could potentially impact the obstacle well before the large chainring hits the obstacle. This won't be a huge problem with something nice and soft like a log but could be a tad more damaging if the obstacle is a rock ramp or ledge. Of note, the carbon frame's downtube will not have such a pronounced kink so RMB is aware of the possibility of damage. This isn't so much a flaw in the design but a note to the rider to be conscious of using technique when going up and over obstacles at the risk of some inadvertent downtube contact and/or damage.
![]()
Curved downtube may impact objects - rider beware! Carbon frame's downtube will be less radically kinked
RMB designed a pocket in the rear of the seat tube to allow for tire clearance at full rear shock compression, giving the frame set a full 10mm of clearance with a 2.3" WTB from the seat tube. There is also that much clearance in the chain stays with the same tire. I am told (but did not independently verify this claim) that a 2.5" WTB would fit. Numbers are all very fine. The true test was on my Chilcotin trip when I encountered some very muddy trails. I can state with some relief that there is plenty of clearance with a 2.3" WTB tire even with the presence of copious amounts of mud. I further note that production frames will have even more tire clearance then the prototype frame as depicted in the picture below.
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Deceptive amount of rear tire clearance
![]()
This tire ran just fine despite a lot of mud on the frame
Suspension
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.
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.
![]()
Chaingrowth
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.
Performance - xc and uphill
Enough with the numbers, on to the ride. My test bike as built with a mix of heavier and lighter parts (XTR, Fox Talas upfront, DHX Air in rear) weighed about 30lbs - not a featherweight but a good balance of light yet strong for my purposes. The xc trail riding test component took place in the South Chilcotin, an area of rugged sub-alpine and alpine beauty with a variety of trails ranging from smooth-and-fast to technical rooty singletrack to faint tracks through scree.
The Altitude incorporates RMB's STRAIGHT UP™ geometry. This geometry incorporates a radically steeper seat tube angle of 76°. Head tubes are more conventional at 69°. When the rider sits on the bike, the seat tube angle is designed to sag to 74.5°. The theory is that this riding position allows someone climbing to stay on the middle of the saddle (as opposed to sitting on the nose) thus allowing the rider to maintain comfort while continuing to harness max legpower.
Bottom line - this bike is a terrific climber. I was able to literally crawl up climbs and maintain traction in many situations where I was hoping that the rear tires would cut loose thereby giving me an excuse to walk and take a break. Perhaps it was the tires but this happened a lot of times on many sections of trail. I couldn't say that the seat tube angle played a part in this; I tried climbing steep, loose trail sections seated mid-saddle and on the nose but this did not alter the superior traction characteristics. The frame has that intangible quality of confident climbing.
Fire-road climbing is .... fire road climbing. The Altitude as I had it built is not particularly light so one sits down and grinds away. I didn't particularly feel the need to engage ProPedal on the Fox DHX Air rear shock as I had set the shock with fairly stiff setting in any event so the bike didn't bob much. It's a competent doubletrack or fire-road climber.
Rocky Mountain's have long been known to be fast, capable singletrack bikes - a trait common to bikes designed in British Columbia. The Altitude is no exception to this rule. Generous standover lends itself to manoeverability; dancing in and out of cambered loamy corners, this bike felt right at home. I expected the bike to give up a bit of comfort in rooty sections given that I had set suspension up fairly stiff but this wasn't the case. Instead I was able to charge rooty sections. The superior rear-wheel traction combined with the expected agility of the bike gave me the ability to attack technical singletrack with confidence.
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South Chilcotin ~photo Iori Kokatalio
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Squamish ~ photo Sharon Bader
Performance - downhill
As one might expect from my praise of this bike's ability in technical xc singletrack applications, the Altitude is an extremely capable bike on downhills. Its geometry (exceptional standover, relatively slack head angle) is suited for technical downhills of the more moderate xc, all-mountain variety. Some bikes that excel in tight, twisty singletrack sacrifice high-speed stability. The Altitude was not one of those bikes and could rail corners and handle long-straightaways at high speed with aplomb and without trouble. I note that the Altitude's wheelbase is approximately 2.2" longer then the comparable ETS-X which it replaces in the size 19 frame; perhaps this and the lower centre-of-gravity design helps with high-speed manners?
I wasn't quite as confident on the bike when it was used in steeper terrain in free-ride type applications or in the air, for example in steep rock rolls, ladder bridges or skinnies (see pictures of the Altitude in Action at the end of the article in North Vancouver for guidance). Acknowledging that it's even more difficult to separate the frame from its parts when reviewing downhill performance, I felt that the Altitude as I had it spec'ed (conventional front air fork, 100mm stem, light front wheels) approached its limits in those free-ride situations. Having said that, RMB does not bill the Altitude as a free-ride bike. A rider is perfectly within his/her rights to customize the Altitude's spec and make it more heavy-duty and bias it to free-ride applications but it isn't within the scope of my review to change components to assess that aspect of the Altitude's performance envelope.
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Whistler ~ photo Sharon Bader
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Whistler ~ photo Tyler Wilkes
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South Chilcotin ~ photo Mark Rowe
Rocky Mountain Altitude 50 frameset - summary
The Altitude delivers on its promise as a bike for epics. It is a multi-faceted platform, a comfortable ride yet a capable tool that can be used to slice and dice singletrack. In its test build, it is a balanced bike but, based on its potential specifications, this reviewer suspects that it will be spec'ed in a way that is biased more towards climbing then descending. It's going to be a worthy addition to the RMB franchise.
Pros:
- Quality finish on the frame
- Bike handles beautifully in tight technical trails
- Well-thought out with lots of room for customization
- Light
Cons:
- Downtube kink rides low; prone to hitting frame on objects
- Clearance for a tire bigger then 2.35 is doubtful on the prototype frame. Production frame to be tweaked so a 2.5" tire can fit
- Prototype frame water bottle mounts too far back so a shock with a piggyback reservoir would not work with a waterbottle cage. Production frame to be changed so waterbottle mounts are moved forward.
Specs: N/A
Price: N/A
Ride: 4.5
Overall: 4.5
Rating Guide:
5.0 Outstanding
4.0 Very Good
3.0 Above Average
2.0 Fair
1.0 Poor
By the numbers; weights, geometry, draft specifications.
Weights below are approximations (all with a RP23 rear shock):
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Rocky Mountain Altitude 50 (aluminium frame)
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Rocky Mountain Altitude 70 (aluminium frame)
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Rocky Mountain Altitude 90 (carbon frame)
In the geometry table below, RMB uses a BB drop measurement (distance between BB and rear axle) rather then a BB height measurement.to remove the variability of wheel size. I measured the Altitude's BB height as äpproximately 13.4" (340mm) with 2.3" WTB tires.
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Geometry
Please note that specifications are not finalized as of September 15, 2008. Prices are also not yet finalized. Draft specifications are as follows but may be subject to change. Please watch the RMB site for updates on specifications and pricing details as and when they are released:
The Altitude in action
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North Vancouver ~ photo Sharon Bader
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South Chilcotin ~ photo Iori Kokatalio
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South Chilcotin ~ photo Kevin Foote
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Whistler ~ photo Sharon Bader
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South Chilcotin ~ photo Rob McLachlan
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South Chilcotin ~ photo Rob McLachlan
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North Vancouver ~ photo Sharon Bader
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South Chilcotin ~ photo Rob McLachlan
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Rocky Mountain Bicycles (RMB) will be resurrecting a venerable name from history when they release the Altitude in 2009. A marked departure from the racing-light steel hardtails that formerly bore the name Altitude, this new Altitude is described as a trail bike that keeps its wheels on the ground for "epic cross country".
RMB provided me with a prototype Altitude aluminium 50 frame for review. The Altitude is slated to replace the ETS-X in the category which RMB calls XC Marathon and what other manufacturers loosely refer to as "all-mountain". It will be produced in an aluminium version and in a (lighter, higher-end spec and more expensive) carbon version. As the Altitude is further refined to a production frame with a production spec, some details of this review may be redundant (I'll highlight those details further in the review) so I urge the readers to also check the RMB website which should be considered to be authoritative.
I'll note at the outset that I am reviewing the frame and NOT the components. My bike was built with a heavier-then-stock package for riding the Downieville downhill course. Although it is difficult to separate the bike from its parts, I will do my level best to confine my remarks to the performance of the frame. Because there is currently a paucity of information about the Altitude, I will be excerpting from a RMB presentation about this bike in lieu of my standard practise of directing readers to a website. I'll then present my general impressions about this frame's performance.
Whistler Alpine
South Chilcotin ~ photo Mark Rowe
Reviewer's biases
I am 155 lbs and 5' 10" and have had over 15 years experience riding bikes in North Vancouver, Squamish, Whistler, the Chilcotins and many other areas in B.C. and Alberta. I've also made many bike trips to other places such as Utah, Washington, Oregon, California and Ontario (for example) so have had some experience biking in a variety of terrain. My bias is towards pedalling up and unlike many people who learned to ride bikes on North Shore trails, I actually enjoy riding (and sometimes bushwhacking) uphill.
I rode this bike over a period of two weeks in a 4 day trip in the South Chilcotin and a few day rides in North Vancouver, Whistler and Squamish. As a frame of reference I have enjoyed riding and have owned and/or tested the following bikes listed below (links to previous reviews I have written are provided:
- Dean Titanium hardtail (light racing hardtail)
- Rocky Mountain Element 70 (light dual suspension)
- Norco Fluid (2006, 2007 vintage) and Fluid LT One (2008) - (all-mountain dual suspension)
- Norco Six 2007 vintage (freeride dual suspension
- Very old-school Norco Rampage (1996 vintage steel hardtail built with heavier parts)
Gun Creek Ranch, South Chilcotin
North Vancouver ~ photo Sharon Bader
Frame highlights
As previously mentioned, the Altitude will replace the ETS-X. Design highlights of the Altitude include; SMOOTHLINK™ suspension; STRAIGHT UP™ geometry, swooping top tubes on the front end for low centre-of-gravity and increased standover, swooping down tubes for shock piggy back and water bottle clearance, 7005 aluminium frames utilizing RMB's FORM™ design and on higher-end lighter framesets - C12 carbon monocoque frames (rocker links, front end main frame and seat stays).
I'll expand more on these above concepts further in the review. Note that the carbon frame is outside the scope of this review so that is all I will mention in this matter. Please check the RMB site for more information on the RSL (Racing Super Light) carbon framed Altitude 70 and 90
South Chilcotin
Frame material
As expected, the Altitude's welds are clean. The paintjob on my prototype bike is a nice eggshell white that seems to shed mud very well. The production bike colours will be more of a bright white colour as depicted in the pictures at the end of this review. The aluminium tubes are designed in a process that RMB calls FORM™. All tubing on the Altitude is custom-made, drawn from 7005 alloy then cold-worked. Every tube is fully butted.
The Altitude incorporates a large hollow head tube area in an effort to increase stiffness. Also of note is the incorporation of aerodynamic leading edges - not to decrease wind resistance but to aid in deflecting rocks. Unfortunately in many of these pictures I put a mud splash guard on the down-tube to help forestall rock damage.
Front End - noting the large head tube and the elliptical leading edge of the down tube with stylish zip-tied mud guard
The Altitude's seat tube is butted and hydroformed. Note in the pictures below that the centre section of the tube is bulged. By bulging the centre section, RMB eliminated the need to weld on a rocker mount, opting instead for a stronger piercing for the oversized rocker link pivots. The rectangular bias in the seat tube is an effort to also increase stiffness.
Rear linkage - non-drive side
Rear linkage - drive side
Rear drive-side - note the assymetric chain stays
The swooping bends in the seat tube and down-tube are apparently not motivated purely by fashion. According to RMB, the down tube shape was necessary in order to keep the shock (and centre-of-gravity) as low as possible in the frame, and also in order to create enough room for a water bottle in all frame sizes. The down tube shape also allows the rider to run a shock with a reservoir.
Since the Altitude frameset is so well thought-out it was with some relief that I felt I could do my "job" as a reviewer and point out some possible negatives. The water bottle placement mounts do not allow a shock with a piggyback reservoir to be run as the reservoir would impact the water bottle. I am told that RMB will be correcting this in production frames.
Water bottle mount placements will be moved forward in production frames
Under certain circumstances, when approaching technical obstacles (the up and over log-pile in the picture below being a perfect example), the downtube kink on the frame could potentially impact the obstacle well before the large chainring hits the obstacle. This won't be a huge problem with something nice and soft like a log but could be a tad more damaging if the obstacle is a rock ramp or ledge. Of note, the carbon frame's downtube will not have such a pronounced kink so RMB is aware of the possibility of damage. This isn't so much a flaw in the design but a note to the rider to be conscious of using technique when going up and over obstacles at the risk of some inadvertent downtube contact and/or damage.
Curved downtube may impact objects - rider beware! Carbon frame's downtube will be less radically kinked
RMB designed a pocket in the rear of the seat tube to allow for tire clearance at full rear shock compression, giving the frame set a full 10mm of clearance with a 2.3" WTB from the seat tube. There is also that much clearance in the chain stays with the same tire. I am told (but did not independently verify this claim) that a 2.5" WTB would fit. Numbers are all very fine. The true test was on my Chilcotin trip when I encountered some very muddy trails. I can state with some relief that there is plenty of clearance with a 2.3" WTB tire even with the presence of copious amounts of mud. I further note that production frames will have even more tire clearance then the prototype frame as depicted in the picture below.
Deceptive amount of rear tire clearance
This tire ran just fine despite a lot of mud on the frame
Suspension
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.
Chaingrowth
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.
Performance - xc and uphill
Enough with the numbers, on to the ride. My test bike as built with a mix of heavier and lighter parts (XTR, Fox Talas upfront, DHX Air in rear) weighed about 30lbs - not a featherweight but a good balance of light yet strong for my purposes. The xc trail riding test component took place in the South Chilcotin, an area of rugged sub-alpine and alpine beauty with a variety of trails ranging from smooth-and-fast to technical rooty singletrack to faint tracks through scree.
The Altitude incorporates RMB's STRAIGHT UP™ geometry. This geometry incorporates a radically steeper seat tube angle of 76°. Head tubes are more conventional at 69°. When the rider sits on the bike, the seat tube angle is designed to sag to 74.5°. The theory is that this riding position allows someone climbing to stay on the middle of the saddle (as opposed to sitting on the nose) thus allowing the rider to maintain comfort while continuing to harness max legpower.
Bottom line - this bike is a terrific climber. I was able to literally crawl up climbs and maintain traction in many situations where I was hoping that the rear tires would cut loose thereby giving me an excuse to walk and take a break. Perhaps it was the tires but this happened a lot of times on many sections of trail. I couldn't say that the seat tube angle played a part in this; I tried climbing steep, loose trail sections seated mid-saddle and on the nose but this did not alter the superior traction characteristics. The frame has that intangible quality of confident climbing.
Fire-road climbing is .... fire road climbing. The Altitude as I had it built is not particularly light so one sits down and grinds away. I didn't particularly feel the need to engage ProPedal on the Fox DHX Air rear shock as I had set the shock with fairly stiff setting in any event so the bike didn't bob much. It's a competent doubletrack or fire-road climber.
Rocky Mountain's have long been known to be fast, capable singletrack bikes - a trait common to bikes designed in British Columbia. The Altitude is no exception to this rule. Generous standover lends itself to manoeverability; dancing in and out of cambered loamy corners, this bike felt right at home. I expected the bike to give up a bit of comfort in rooty sections given that I had set suspension up fairly stiff but this wasn't the case. Instead I was able to charge rooty sections. The superior rear-wheel traction combined with the expected agility of the bike gave me the ability to attack technical singletrack with confidence.
South Chilcotin ~photo Iori Kokatalio
Squamish ~ photo Sharon Bader
Performance - downhill
As one might expect from my praise of this bike's ability in technical xc singletrack applications, the Altitude is an extremely capable bike on downhills. Its geometry (exceptional standover, relatively slack head angle) is suited for technical downhills of the more moderate xc, all-mountain variety. Some bikes that excel in tight, twisty singletrack sacrifice high-speed stability. The Altitude was not one of those bikes and could rail corners and handle long-straightaways at high speed with aplomb and without trouble. I note that the Altitude's wheelbase is approximately 2.2" longer then the comparable ETS-X which it replaces in the size 19 frame; perhaps this and the lower centre-of-gravity design helps with high-speed manners?
I wasn't quite as confident on the bike when it was used in steeper terrain in free-ride type applications or in the air, for example in steep rock rolls, ladder bridges or skinnies (see pictures of the Altitude in Action at the end of the article in North Vancouver for guidance). Acknowledging that it's even more difficult to separate the frame from its parts when reviewing downhill performance, I felt that the Altitude as I had it spec'ed (conventional front air fork, 100mm stem, light front wheels) approached its limits in those free-ride situations. Having said that, RMB does not bill the Altitude as a free-ride bike. A rider is perfectly within his/her rights to customize the Altitude's spec and make it more heavy-duty and bias it to free-ride applications but it isn't within the scope of my review to change components to assess that aspect of the Altitude's performance envelope.
Whistler ~ photo Sharon Bader
Whistler ~ photo Tyler Wilkes
South Chilcotin ~ photo Mark Rowe
Rocky Mountain Altitude 50 frameset - summary
The Altitude delivers on its promise as a bike for epics. It is a multi-faceted platform, a comfortable ride yet a capable tool that can be used to slice and dice singletrack. In its test build, it is a balanced bike but, based on its potential specifications, this reviewer suspects that it will be spec'ed in a way that is biased more towards climbing then descending. It's going to be a worthy addition to the RMB franchise.
Pros:
- Quality finish on the frame
- Bike handles beautifully in tight technical trails
- Well-thought out with lots of room for customization
- Light
Cons:
- Downtube kink rides low; prone to hitting frame on objects
- Clearance for a tire bigger then 2.35 is doubtful on the prototype frame. Production frame to be tweaked so a 2.5" tire can fit
- Prototype frame water bottle mounts too far back so a shock with a piggyback reservoir would not work with a waterbottle cage. Production frame to be changed so waterbottle mounts are moved forward.
Specs: N/A
Price: N/A
Ride: 4.5
Overall: 4.5
Rating Guide:
5.0 Outstanding
4.0 Very Good
3.0 Above Average
2.0 Fair
1.0 Poor
By the numbers; weights, geometry, draft specifications.
Weights below are approximations (all with a RP23 rear shock):
- The RSL (Racing Super Light - ie carbon frame) Altitude 90 and 70 Frame with shock (18") is 5.7Lbs
- The Altitude Alloy Frame with shock (18") is 6.6Lbs
- The Altitude 90 RSL, 19" fully built, with pedals is 25.9Lbs. The 18" frame should weigh about 25.5Lbs.
Rocky Mountain Altitude 50 (aluminium frame)
Rocky Mountain Altitude 70 (aluminium frame)
Rocky Mountain Altitude 90 (carbon frame)
In the geometry table below, RMB uses a BB drop measurement (distance between BB and rear axle) rather then a BB height measurement.to remove the variability of wheel size. I measured the Altitude's BB height as äpproximately 13.4" (340mm) with 2.3" WTB tires.
Geometry
Please note that specifications are not finalized as of September 15, 2008. Prices are also not yet finalized. Draft specifications are as follows but may be subject to change. Please watch the RMB site for updates on specifications and pricing details as and when they are released:
| Altitude 30 FORK Fox 32Float R SHOCK Fox Float RP2 Custom Valved WHEELS Deore / WTB Speed Disk XC CRANK Race Face Ride XC GEARS Shimano Deore / XT BRAKES Shimano M575 | Altitude LO FORK Fox 32Float RL 15mm E-Thru SHOCK Fox Float RP23 Custom Valved WHEELS Wheeltech / M525 / Mavic XM317 CRANK Race Face Evolve XC GEARS Shimano SLX / XT BRAKES Formula ORO K24 | Altitude 70 FORK Fox 32Float RL 15mm E-Thru SHOCK Fox Float RP23 Custom Valved WHEELS Shimano XT 15mm / Mavic XC717 CRANK Race Face Deus XC GEARS Shimano XT / XTR BRAKES Shimano XT |
| Altitude 70 RSL FORK Fox 32Float RL 15mm E-Thru SHOCK Fox Float RP23 Custom Valved WHEELS Shimano XT 15mm / Mavic XC717 CRANK Race Face Deus XC GEARS Shimano XT / XTR BRAKES Shimano XT | Altitude 90 RSL FORK Fox 32Float RLC 15mm E-Thru SHOCK Fox Float RP23 Custom Valved WHEELS Mavic Crossmax SLR 15mm CRANK Race Face Next SL XC GEARS Shimano XTR / XTR BRAKES Formula R1 |
The Altitude in action
North Vancouver ~ photo Sharon Bader
South Chilcotin ~ photo Iori Kokatalio
South Chilcotin ~ photo Kevin Foote
Whistler ~ photo Sharon Bader
South Chilcotin ~ photo Rob McLachlan
South Chilcotin ~ photo Rob McLachlan
North Vancouver ~ photo Sharon Bader
South Chilcotin ~ photo Rob McLachlan
