Out of the Box: Specialized Stumpjumper Carbon 29 SS- by Grannygear
Ok, let’s get this carbon fiber cat out of the bag, shall we? Taking stock of the Specialized Stumpjumper Carbon 29 SS frame, the first thing that struck me was the form of it and the shapes that carbon can be wrought into. The massive top tube at the head tube, the gentle curves of the seat tube and top tube, the bottom bracket area and the small seat stays…it all looks great, something that can not always be said about some carbon frame shapes. Even the graphics are reasonably understated by today’s standards, although I would have left off the white graphics and stayed with silver only, muting the look just a bit. Kudos to the full length cut to shape protector under the down tube that keeps rocks from chipping away at the precious composite construction…razzies to the person who decided to put BIG Specialized lettering in white on the protector. It does not blend with the down tube decal and looks like a mirrored image but not quite. Please…maybe just a clear protector would be fine.
Beginning at the main triangle, the tapered head tube stands out as does the PF30BB shell. Small patches of metal are glued to the frame in places that may see a chain drop-and-chew. The front end looks absolutely stout. The slightly bent seat tube is nice and together with the slightly arched top tube looks racy. Moving to the back section, the seat stays are very slender and it looks like some thought was given to compliance. There seems to be plenty of tire clearance at the bottom bracket/chain stay junction and the chain stays look substantial regardless, tall and not crimped or yoked like a metal frame might have to be. Carbon gives you options in shapes and layups that a butted metal tube can not touch. Finally, there are a gorgeous set of tidy sliders at the dropouts, allowing for chain tensioning. This is a step away from the split shell EBB that is on the Carve SS and the older Rockhopper SS frames. Most sliding and swinging dropouts look like warts on the Prom Queen but these are barely even noticeable. The rear brake post mount is set for a 140mm rotor, so if you are running the more typical 160mm rotor, you will need a +20mm adapter.
The 140mm rear brake mount gives you an insight into the intent of this frame. Stumpjumper hard tails are tipped a bit towards raciness and the Stumpy SS frame is shorter and steeper than the Carve Pro SS frame this will replace. The top tube is 10mm shorter, the chain stays are 12mm shorter (varies of course depending on set-up), and the seat tube angle is 1/2 degree steeper. The S Works geared version I rode earlier this year was a very different feel over the Carve. It felt shorter and smoother and was quite a treat on a tight, rooty and rocky trail. We shall see if the SS version in the less than S Works construction carries that along.
I weighed the XL/21″ version with the seat post clamp at 1600g/3.5lbs. That is pretty much one pound of weight savings over the aluminum Carve Pro SS frame. The frame also includes a Campy type headset and a very swank S Works seat post in a 27.2mm size.
My intent is to build it with most of the parts the Carve was running so I can get a good feel for the differences in ride and performance. I have some sweet FSA carbon bits that will find their way on there too so it should be a very nice, but not ‘ultimate’ build.
Stay tuned as we get the wrenches turning and hit the trails. Carbon…it’s what’s for dinner. In the meantime we asked some questions to Specialized about carbon and the Stumpy SS we have. Let’s cut away to that shall we? Introducing Brad Paquin, a composites engineer that works on developing bikes like this and Sam Benedict, Specialized’s marketing person to the entire universe and beyond…or something like that.
First of all, let’s talk in some general terms then narrow in to the specific bike we are riding now, the Stumpjumper Carbon 29 SS. Carbon is a bit of a black box of mystery in that there is so much controversy in the merit of it, the durability, the construction used, quality control, etc. So, let’s begin here by peeking into that black box just a bit by challenging some of the ‘truths’ about composites as used in a bike frame.
- Carbon is fragile. It is not a long term bike choice like steel or Ti is.
Brad Paquin – Steel, titanium, and carbon fiber are some of the only materials which can be designed to survive infinite load cycles. The engineering term is the materials ‘Endurance Limit’. If you design your frame and carbon laminate to have a stress lower than the materials endurance limit – it will literally last forever.
If a carbon frame is designed and manufactured properly, it will last a lifetime. We routinely run carbon frames in fatigue for hundreds of thousands of load cycles (multiple times more than industry standards) – which correlates to a lifetime of use.
The thought that carbon is fragile comes from its damage tolerance – not normal riding loads. If a carbon bike is damaged by impact severely enough, it can lead to frame failure – no denying it. The misconception is the severity of impact it takes to cause such a failure. Some people think that a small crash will damage a frame – which is simply not the case. Our carbon mountain bikes are designed to withstand normal rock strikes, and crashes. The amount of damage it takes to cause in impact failure on a mountain bike is very high – if the same impact happened on an alloy/steel/ti frame – it would be severely dented and should be replaced. Bottom line: if you take a look at your current metal bike and don’t see any large dents – your carbon mountain bike would have survived the same amount of abuse.
- Carbon is pretty much all the same. My ‘China Direct’ frame is a third of the cost and is the same thing.
Brad Paquin – Every frame material has no-name suppliers and quality suppliers. If you buy a cheap steel frame, it is not the same as a bike made with a high end Reynolds tube set. With carbon the differences between no-name frames and reputable brands is even larger – as it is often a safety issue. The manufacturing process of carbon frames is very involved and requires dedicated tooling for layup, molding, machining, and bonding – not to mention the quality of materials used to get the best ride characteristics.
I could talk all day about the manufacturing process, QC procedures, and the resulting repeatability we have in our product. Specialized engineers have the best tools in the industry from powerful CAD software, high end FEA (Finite Element Analysis) for structural analysis, and CFD (Computational Fluid Dynamics) for virtual wind tunnel testing to produce designs that are structurally sound, and good looking.
After the design process, materials and laminate schedules are specified based on measured loads in tubes. Prototypes are produced – and lab testing begins. We test frames in fatigue and ultimate strength scenarios using industry standards and our internally developed tests which are typically far more stringent than industry standards.
Once in production the QC team monitors production using high tech tools such as ultrasonic non-destructive testing in critical areas (a technique commonly used in the aerospace industry) which checks for any voids or manufacturing defects.
- Carbon costs too much. Is there a cost vs. performance issue here? Is it ‘worth it’?
Brad Paquin – The answer to this question comes down to the rider. The performance of carbon is impossible to deny. Carbon mountain bikes are lighter and stiffer than any other frame material. If you have the means and want the highest performance, carbon is the best option.
- Let’s get to the FACT(s). Tell me about the FACT IS 11m vs 8m and what all that means to the end user (me) other than one costs more?
Sam Benedict – the FACT system is pretty straight forward system (though not always perfect) that is built to be ranking system of frames. A higher number indicates a nicer frame. In this case, the materials in the frame are a stiffer material so the engineers can build a lighter frame. These materials cost more and yield a lighter, stiffer (read faster) bike.
- Was there a targeted goal or goals for this frame (and the geared versions too)? Some CF frames are almost brutally stiff and others are designed to be compliant like the BMC TE01. What were you guys shooting for and how do you know you hit the marks?
Sam Benedict – the Stumpy has always been a delicate balance of weight, stiffness, and, while not important to everyone, hot looks! So we want a light bike that can handle having the pedals stomped on for fast acceleration. We also know the riders like the whole hardtail experience so no rear suspension but taking the sting out of bumps is a massive boon. The seat stays are shaped and constructed to be more compliant. It all adds up to a great riding bike!
- CF seems to be the darling of the weight weenie set and with obvious reasons. But there has to be, as with any material, a point of diminishing returns as you cut grams. Are we there yet, that point where we have flirted with the bottom, learned the lesson, and have gotten to a good place? Or will we see a 2.5lb 29er CF frame that is viable?
Sam Benedict – We are around the 1150g range for a large, that’s pretty crazy! We will always try to make a frame “better” so we will see!
- Now this may be for the marketing guys, so feel free to hand this off. Why is Specialized paying any attention at all to single speeds? You have two or three, including the Carve based models, and this Stumpy frame is a premium product. Trek dropped the Superfly SS for 2013 and Giant does not seem to know SS riders exist (just to call out the other ‘Big Guys’). Why is this frame even in your line-up?
Sam Benedict – It sounds corny but we have always been a brand of riders for riders. Singlespeeders are people too and they often ride the hell out of bikes… there is a solid SS crew wearing the red S around here. But just because it is a smaller niche doesn’t mean these riders don’t deserve great bikes; simple as that. We love to make rad bikes and do our best to connect with the riders, any and all.
Note: Specialized sent over the Stumpjumper Carbon 29 SS for test/review at no charge to Twenty Nine Inches. We are not being bribed, nor paid for this review. We will strive to give or honest thoughts and opinions throughout