Monday, 04 July 2011 15:28
Pinarello FV4 Hard Tail and FV5 Full Suspension bike review
Finally suspension systems explained graphically
by Chris Brand
(Chris Brand is a multiple SA motocross & enduro champion, multiple SA Masters MTB champion and renowned suspension setup expert & critic.)
ASG Sport Solutions Pty (Ltd) kindly gave me one each of their new Pinarello MTB bikes to race and evaluate for the 2011 MTB season. I have now had these bikes for over six months and have really put both the FV4 Hard Tail and FV5 Full Suspension through rigorous testing. They are both manufactured from the strongest carbon fibre currently used in the biking industry, Carbon 50HM1K. The FV4 frame weighs in at 1.320 kg and the FV5 with shock at 2,228 kg. It was the first time that I had ridden a carbon MTB bike as I had always been nervous about the durability of carbon in MTB type conditions. I was especially concerned about how carbon would hold up if you fell on rocky ground and the frame sustained a sudden impact. I have ridden both bikes extensively in severe XC type conditions and have crashed and dropped the bikes on numerous occasions and other than chips on the paint surface, to my surprise, the bikes have stood up perfectly.
Pinarello has exclusive use of Japanese carbon-fibre supplier Toray's 50HM1K. Additionally, the new material has what Toray calls "nano-alloy" which, the company says, disperses nanoscale elastomers between the carbon fibres. These elastomers absorb impacts and prevent the propagation of cracks as they occur. With the FV5/FV4, Pinarello introduces its Asymmetrical Frame System concept: A rider's pedalling inputs are fairly symmetrical, but a bicycle's single-sided drivetrain turns those symmetrical inputs into asymmetrical loads on the frame, says Pinarello.
A combination of shaping and layup balances the bike, says Pinarello, for a more stable frame under severe loads such as climbing and sprinting. The FV5 and FV4 offers a phenomenal ride, with a balance of the drivetrain stiffness and efficiency that racers demand. Pinarello claims this particular carbon has a 59% better impact strength than standard carbon. 50HM means a rigidity of 50 tons/cm and the 1K means 1,000 fibers per yarn. Typically, the higher the HM number, the more brittle the carbon, which in theory would make the frame lighter but also more susceptible to impact fractures and breaking. To prevent this from becoming an issue, the Toray nano-alloy is a nanoscale elastomer that’s embedded between the carbon fibers that cushions impacts and prevents cracks from spreading. Pinarello has an exclusive use rights agreement for this carbon from Toray for cycling applications.
Being a hardtail I chose and raced the FV4 on courses that were smoother and found its lightweight a pleasure on long climbs and found it great on smooth XC courses where it went exactly where you pointed it with very little effort. It has a 71 degree head angle which is pretty much the standard on XC/Marathon type bikes, so nothing out of the ordinary here. The frame was very stiff and the direct response to pedaling inputs was great. The FV5 really comes into its own on rough rocky and rutted downhill and technical climbs. Being a full suspension with perhaps the best suspension technology, I have found it handled like an absolute dream both when climbing and on long descents. The “Fully Active” suspension making it a pleasure braking into corners in all types of conditions that a Marathon nowadays throws at you. I say that because what I have noticed over the last five years is that as more singletrack gets added to the Marathon events so the Marathons are becoming more and more like very long XC courses.
I think for me the single most attractive thing that stood out about the FV5 was its stability and ease of riding down long rocky descents, the head angle on the FV5 being 70 degrees which is probably the reason for this. The bike however, handles extremely well through corners and once again is a pleasure to ride on fast flowing single track.
I would like at this point to elaborate and explain the suspension design that the FV5 uses and why it is undoubtedly the best! If you refer to Diag.1, this is the oldest MTB suspension design, single pivot with the pivot located just above and behind the seat tube. The only way that this design could get the radius of 516mm to remain the same throughout the 100mm of travel would be for this chain stay arm to pivot around the bottom bracket. This has been tried but never been successful as it added too much weight and maintenance was too complicated.
If you now refer to Diag.2, you will see that throughout the 100mm arc that the wheel axle travels the radius gets longer. I have taken the trouble to actually measure some examples of each design and this single pivot design changes by as much as 19mm. This means that you, the rider, are trying to pedal the cranks clockwise but every time you hit bumps on the trail it is pulling the chain backwards by up to 19mm counterclockwise! This obviously causes a loss of power and makes your pedaling action feel unsmooth or erratic. Another huge issue with this design is that under braking into corners the suspension can’t remain fully active as you need to have your disc rotor rotating with the axle on the seat stay to not get “suspension lock up”.
A German fellow named Horst solved this and the suspension design has a world patent. Sadly, very few manufacturers use it as I am sure they don’t want to pay the royalties and believe that their system works as well or better.
If you look now at Diagrams 4 and 5, the 4 Bar Horst Link Design sometimes referred to as FSR or ICT, which are in fact one and the same in that they have 4 pivots, the MOST important being that they have pivot no.2 on and slightly below the axle on the chain stay arm. By doing this it allows your suspension to act like a parallelogram. As the chain stay now travels through its arc of 100mm you can see that the angle made by this pivot reduces from 165 degrees to 157 degrees. This enables the radius to remain almost constant with the Pinarello only changing by 5mm. This is 280% better than the first single pivot design I rode five years back. Does it make a difference? Sure it does. On a flat ride out and back with a Horst Link that had 6mm difference in radius (20% worse than the Pina) I did 98km six minutes quicker at eight watts less power!!!
If one now refers to Diag.5, where some designs have the pivot on the seat stay arm, one can now clearly see from the diagrams that there is no way here of changing the length of the chain stay arm through its arc of travel and no way of keeping the suspension fully active. It in fact behaves in exactly the same way as a single pivot. When one studies the diagrams carefully you do not have to be a rocket scientist to see that the ONLY design that will give you smooth pedaling action and the least loss of power, as well as keeping the suspension fully active under braking is the Horst design, of which luckily for me the Pinarello tests out the best! Once you have read this please go home and measure yours. It is extremely easy! You just have to loosen one end of your shock and then measure the distance from the centre of your BB to centre of your rear axle and then repeat once you have moved your wheel through 100mm of travel. Now you be the judge!
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