Wednesday, September 17, 2008

Exogrid: someday you'll be mine


Beauty is More Than Skin Deep.
The patented Exogrid Technology adds another dimension to the already proven performance of the Racer X. The multi-material makeup of the frame’s down tube works to absorb the small washboard bumps encountered at high speed that the suspension can’t respond to. When you combine the lightweight downtube with the most efficient rear suspension platform in cross country today, the end result is a thing of beauty.

Rider-centric custom geometry is available on all Exogrid and titanium frames. Hand-crafted in Tempe, Arizona all of our Exogrid and titanium frames are available with custom geometry. The perfect fit of man and machine is easily achieved through our extremely simple Custom Fit Program.

  • Seamless 3Al/2.5V titanium front triangle featuring a patented, Exogrid downtube
  • Hand-crafted in Tempe, Arizona
  • Custom tuned Fox RP23 provides100mm of rear wheel travel
  • Precision machined 6Al/4V titanium shock tabs
  • Triple, oversize, sealed-bearing main pivot
  • Compression molded, multi-direction carbon fiber X-Link
  • Hydro-formed chain-stay
  • Clevis Style Horst Link pivots captures each dropout eliminating independent dropout flex
  • Carbon seat-stay
  • Sizes: XS, S, M, L, XL, Custom


Next Generation Full Suspension

Just like any cutting edge industry, the top players eventually reach a point where the products in the market place that the customers can choose from are all generally good. It happens with cars, motorcycles, computers, and now full suspension mountain bikes. Sure, there's still plenty of basic single pivot bikes and a few other generally outdated designs out there, but the top performers in the suspension world have basically adopted three types of designs. Please keep in mind that not all bikes are created equal. As with almost anything you can buy, just because a company touts a cutting edge design does not mean they are automatically cutting edge or high quality for that matter. A Hyundai may use a similar suspension design to a BMW, but that does not make them a top performer (sorry Hyundai). We believe that there are plenty of "good" bikes out there, but there are only a few truly great ones. So how do you know what the best suspension design out there is? How do you know what to buy? Read on and I'll tell you at the end.

Floating Bottom Bracket shell designs were developed by GT Bicycles for use in their I-Drive system. This design as well as similar ones used by Maverick and Klein, place the entire bottom bracket and crank assembly as a floating pivot between the front and rear triangle of the bike. This differs from most full suspension bike designs, where the bottom bracket is part of the bikes front triangle, or in the case of a unified rear triangle design, the bottom bracket is part of the rear triangle assembly. Floating bottom bracket designs can exhibit most of the great characteristics attributed to full-active 4-bar link style designs in that they can be designed to resist pedal bob and the suspension can remain active under braking (i.e.: it does not lock the suspension out, stiffen it up, or raise the rear end of the bike as the rear brake is applied) Overall, this suspension system has always had potential. However, current designs on the market are not perfect. The current I-drive configuration, although lighter then the previous generation, is still fairly complex and has not changed enough to take true advantage of stable platform shock technology. The Maverick/Klein style floating bottom bracket design is straight forward, and relatively simple. However, the design is tied to a special front derailleur and a very custom rear shock which cannot be switched out for different brands of shocks as technology moves forward. Also, the design's very slack seat tube angle makes it difficult for some riders to attain the correct positioning over the pedals and there are some front derailleur shifting issues that seem to plague the current design.

Bottom Line
Floating Bottom Bracket designs have potential but still need some additional fine tuning to achieve the level of refinement available from some of the other fully active suspension designs on the market today.

Companies that feature these designs
I-drive: GT, Schwinn, Mongoose. Other Variations: Maverick, Klein, Seven

Bikes referred to as Virtual Pivot Designs feature a double linkage that connects the front and rear triangle of the frame. This differs from a fully-active 4-bar link style bikes which use one pivot between the front triangle and lower swing arm with a single linkage up top to activate the shock. With virtual pivot designs, the attachment points of the two separate linkages from the front and rear triangle plus the length of each linkage will decide the overall path that the rear triangle moves through space. This path is infinitely tunable and is not restricted to a specific straight line or arc. The rear end of the bike can pivot in virtually any path determined by the designer. Because the main pivot point is always moving depending on where the rear suspension sits in its travel, an exact main pivot location does not actually exist, hence the name "Virtual Pivot".

When most people think "Virtual Pivot", they think of the VPP bikes by Santa Cruz and Intense. These bikes use a specific type of Virtual Pivot design that was originally developed and patented by Outland Bicycles about 10 years ago. The patents cover a specific linkage configuration and rear wheel travel path that is designed to aid the pedaling performance of a rear suspension bike without negatively affecting the overall bump absorption capabilities of the suspension. VPP bikes feature an "S" shaped rear wheel path. As the suspension moves through its travel, it does not swing a standard arc or move in a vertical wheel travel path. The path is similar to a stretched out or elongated "S". In addition, as the two linkages guide the rear wheel through this path, they reach a point about 25-30% into the suspensions travel where the two linkages oppose each other and form what can be best described as a very light lock-out or stopping point in the suspension travel. This point typically coincides with the amount of sag (the amount the suspension settles from your body weight) that you would run on a rear suspension bike. It takes very little bump force to move the linkages past their opposing point. The result is a bike that pedals well at the "sag" point yet is still relatively free to pick up bumps. So what's the downside? The double link design on any virtual pivot design adds a lot of complexity to the frame, and small linkages are forced to handle the majority of the frame loads, so frame stiffness and durability suffer in order to keep the weight down, or in the case of down hill designs, the frames become very heavy. Also, having a link behind the cranks severely restricts tire clearance making lighter, cross-country based virtual pivot designs with short chain stays almost un-rideable in muddy conditions. From a ride standpoint, the bikes pedal well when at the sag point but will still oscillate or bob on fire road type climbs or under hard sprinting. VPP designs still benefit heavily from stable platform shock technology to aid pedaling at other points in the suspension travel. Some riders contend that the bikes lack the lively accelerative feel of some other designs and don't maintain traction as well on climbs as some of the designs on the market. Finally, like single pivot bikes, VPP bikes suffer from brake jack, which is a stiffening of the suspension as the rear brake is applied, resulting in reduced bump absorption or potentially locked out suspension under hard braking. This is a problem that does not plague fully-active 4-bar designs.

What about other "Virtual Pivot" designs? Because the designer is free to send the rear wheel in whatever path, he/she desires, the possibilities are endless. However, there is no getting around the amount of moving parts, and overall complexity of any virtual pivot type design.

Bottom Line
"Virtual Pivot" designs are generally good 3rd generation suspension designs. Pedaling performance is an improvement over most single pivot designs. However, the complexity, frame stiffness vs. weight, tire clearance and overall chassis feel still leave them a step behind some of the more cutting edge fully active designs today.

Companies that feature virtual pivot designs
Santa Cruz, Iron Horse, Ibis, and Giant

There's never been a more hotly contested suspension design on the market than the 4-Bar linkage design with the Horst Link. This design has been around only slightly longer then the original Outland VPP, but its instant success and many attributes have made it the most valued and fought over suspension design in the world. The original design was developed by Horst Leitner at AMP research. The driving goal behind the design was to isolate braking forces from affecting the suspension performance. The first generation Horst bikes did not stiffen up or lift (brake jack) under hard braking. They were and still are to this day "fully active". The icing on the cake was that the original bikes pedaled better than anything else at the time.

The original Horst patents were purchased by Specialized Bicycles and are selectively licensed to only a few companies in the USA. In Europe and Canada where the US patents don't apply, Horst Link style bikes are the dominant suspension design. Just like with virtual pivots, and floating bottom bracket designs, many of today's 4 bar designs are at least 3 generations beyond the original. Everything has been changed to make the already great pedaling design even better without affecting the bike's excellent performance under braking. Four bar bikes, are light, strong and can be built extremely stiff without the complexity and issues associated with other suspension designs, plus they don't stiffen up under braking. If you own a suspension bike, you want the suspension to work. One of the worst traits a suspension bike can exhibit is to have the shock get progressively more locked out as you are braking hard into a bump filled corner. This is when you need the suspension most and this is just one of the areas where the 4 bar delivers and others can't.

So what's the downside? There is almost nothing bad that can be said about a well made 4-bar design. However, nothing is perfect. Because of the way the suspension works, long travel 4 bar bikes frequently need to have an interrupted seat tube design to the front triangle. Although there is no performance or handling downside to this, some riders prefer the traditional look of a standard front triangle and/or like to have the wider range of seat post adjustment of non-interrupted seat tube bikes.

Bottom Line
Current 4-bar designs from high end companies have the edge over anything else on the market. The ability to build light, class leading bikes at any travel range with ample tire clearance, great pedaling feel, in a fully active chassis with the highest level of durability is a combination that cannot currently be matched by any of the competing designs on the market.

So, are we a little biased? Of course we are, but that's ok because it's our article and there's no real need to be politically correct. The reality is that all the above designs are excellent. If you read closely, all references to the downsides of any particular design said "currently". That's not to say that any of these and maybe some new ones will be better. Maybe they will tackle the short comings of the current designs. With every generation, every model year, etc., we all continue to get better. Our competitors are working just as hard as we are to make sure their latest performs better then the last and we continue to develop products to stay ahead of our competitors. It's a game that never ends. But right now, I can say with the utmost confidence, that the ride, performance, durability, and just about any other measurable aspect of a Titus bike is better then our competition because it is not just the suspension design, and it is certainly not the marketing or the hype. It's about the details, and Titus does the details better then anyone. It's not just a pretty paint job, but a perfectly designed main pivot, the right size tubing to optimize lateral stiffness, and a partnership with the shock manufacturers to give us what we want and to not just accept what they have to offer. These are just some of the details that make a Titus a Titus. Yes, we just happen to build the most kick ass 4 bar, Horst link bikes, in the world, but it wouldn't matter if we were building virtual pivot or floating BB designs either. They would still be great and they would still be better because we sweat the details to make it the best bikes in the world and being better is what makes a Titus the bike to have in the past, present and well into the future. So, if you don't already own a Titus, you have no idea what you're missing and if you do, tell them what they are missing. In the mean time, keep on riding and we hope to see you out on the trail.


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