We all know suspension works. Right? But have you ever questioned HOW you know it works? A quick glance around a World Cup start line will allay most suspension-doubters; these days every professional cross-country rider competes on a bike sporting a permutation of one suspension design or another. However the cynics, and the die-hard rigid fanatics amongst you will be quick to point out that it is the suspension manufacturers who pay the pro’s wages, and it would be tantamount to financial suicide for them to opt for a rigid mountain bike. After all, suspension systems are the number one after-market upgrade, so it would not be a wise move if the sponsored riders were to bite the hand that feeds them.
But logic suggests that, as a result of the evolution of race courses, the days have long since gone when it was possible for a rigid bike to be a force to be reckoned with, as was the case with David Baker in the early 1990’s. Or more bizarrely when the likes of Dave Hemmings could finish on the podium of the Junior Downhill World Championship whilst competing on a rigid Klein. Yet despite these absurdities, how many of you have looked forlornly at the hardtail whipping past you on a climb as your bobbing full-susser sucks the lifeblood out your legs? Or have you ever tried to defend the ‘turning circle of an oil tanker’/comfort trade-off to a rigid enthusiast? Believe me, it’s not easy. Obviously each type of mountain bike design will have its nuances, which in some circles will be regarded as a plus; whilst in others they will be seen as a definite no-no. This diversity is good and is healthy for the sport, but there is arguably a need to sweep this subjectivity aside, especially if we are to answer the question: what type of mountain bike will evoke the best rider-performance?
Human performance in mountain biking is ultimately measured by how quick a rider can complete a designated course in relation to the other competitors. However, this outcome is only the tip of the iceberg; it is the product of many other synergistic components, each of which is capable of bringing you to your knees if ignored. One of the biggest players in the performance equation is the amount of energy you expend in order to propel you and your bike along the course.
Ordinarily a bicycle is about ninety-five percent efficient when transferring the energy from your legs to getting the rear wheel turning. The remaining five percent is lost as heat (due to the resistance of the bearings, chain and other moving parts) and overcoming the rolling resistance of the tyres. This means that in theory, the energy expenditure of cyclists can easily be measured; hook them up to an ergometer (an elaborate turbo-trainer) and measure their energy output. Simple. Whilst this is fine for our road-cycling brethren, it does not take into account the additional energy-sapping complexities that comprise our off-road sport.
Whilst mountain biking, the main consumers of your energy are the terrain (obstacles, mud, loose surfaces, irregularities), an increased rolling resistance due to wider, softer tyres, and the effort required to lift you and your mud-laden bike against gravity when you’re climbing. Therefore in order to get an accurate value for the energy requirements of mountain biking, the information must be gathered whilst riders are cycling off-road.
Fortunately an erogometer is not the only way to measure energy output. It is also possible to calculate the energy expenditure of mountain biking by analysing the proportion of gases the rider breathes out. Up until recently this has meant collecting the rider’s expelled air in a large balloon that was attached to his or her back. These balloons have the aerodynamics of an average house, and are somewhat cumbersome and obtrusive to ride with. Furthermore, as the bags become full they require frequent swapping which involves a lot of faffing around and interferes with the rider’s performance. Fortunately advancement in technology has produced a gismo called the Cosmed K4b2 metabolic analyser. This machine does away with the balloon-method of gas collection and is capable of analysing the rider’s expelled air and carbohydrate usage whilst the individual is exercising. The small, unassuming size of the Cosmed (about as big as a Camalbak Zoid) belies its hefty £25,000 price tag.
A further factor in determining rider performance is muscle damage. Supporters of suspension bikes often report greater comfort and less muscular stress compared to a rigid bike. Over a prolonged ride these muscular stresses can quickly accumulate and adversely affect riding performance. Furthermore, the muscular pain can often spill over into the next day, which can have a negative effect if the rider is involved in an off-road stage race, or an epic multi-day ride.
Up until now there has been very little scientific investigation regarding these factors, and to what extent they affect rider performance. Most of the current information is only anecdotal and subject to wide interpretation. Whilst feedback from professional riders is of extreme importance to the advancement of our sport, the process is not made easy when other factors such as sponsorship may skew the objectivity of the their comments. So without further ado, it’s time to unearth some hard facts about suspension, and examine the effects it has on the performance of the rider.
For our experiment we chose a Cannondale Jekyll 3000 because, due to the remote lockout facility, it was able to be ridden under three conditions: (i) rigid – suspension locked out at all times, (ii) adjustable suspension – the rider chooses when to turn the suspension on or off, and (iii) full suspension – suspension on at all times. Six riders took part in the test, and following a warm-up each rider, reported to the start line and had the metabolic analyser fitted. On the command ‘go’ the rider would set off with the sole aim of completing four laps of a 1.5km off-road course in the fastest possible time. Not surprisingly the spectacle of a mountain biker with a blue rubber octopus on his face, riding a bike with one fork stanchion, and sounding like Darth Vader drew some strange looks and comments from unsuspecting passers by. Unfortunately for the riders they had to perform this unbecoming routine once a week for a further two weeks; once in each of the three suspension conditions.
After the data was collected it was analysed using a statistical software program. The average time-trial performance for all of the tests was 35minutes 15 seconds, but most intriguingly, there wasn’t a significant difference between the times for the three suspension conditions. This means that for rides lasting around half an hour it doesn’t matter whether you’re riding a rigid or a full suspension mountain bike.
However, this is not the full story, because as you know, most mountain bike rides, and certainly the majority of races last longer than half an hour. Next up for inspection was the amount of energy expended during each test. The results showed that whilst riding a full suspension bike, all of the riders expended significantly more energy, and used significantly more carbohydrates, compared to the other two conditions. Carbohydrates are the preferred fuel for mountain biking, yet paradoxically your body can only store a limited amount of them. Therefore the more economical your body is at using these stores the better. The test results show that carbohydrates were being used at a high rate during the full suspension condition. If these results are extrapolated to full race duration, it would suggest that riding a full-susser would significantly increase your chances of running out of carbohydrates and ‘bonking’ prematurely. It was also found that the energy production of the riders was more anaerobic during the full-suspension tests compared to the rigid tests. Producing energy anaerobically results is the formation of lactic acid, which is the dreaded burning sensation in the leg muscles that we are all familiar with. During the tests, the levels of lactic acid did not accumulate sufficiently to adversely affect the time-trial results, however the results suggest that if you are riding a full-susser for longer periods then the lactic acid accumulation may come in to play and curtail your performance.
But before the suspension doubters rejoice, we must examine all of the facts. With regard to muscle damage it was found that a rigid bike results in significantly greater muscle damage when compared with the other two suspension conditions. And what’s more, the pain associated with the muscle trauma was still present up to 24 hours after the test. This suggests that a rigid bike may have a negative effect on rider performance if the race is protracted, such as during an Enduro, or a multi-sage race like the Trans-Alp.
Cruising along in the middle, showing no detrimental effects on performance was the adjustable suspension condition. This type of suspension was found to glean the best of both worlds: it produced less muscle damage than the rigid condition, and used less energy and carbohydrates than the full suspension condition.
If a long ride in the hills is the order of the day and you have an abundance of food and are in no particular hurry, then a full suspension bike will be a better choice than a rigid one. If however, you’re just going for a relatively short hack around your local trials then a rigid bike will do fine, and it will also keep your wallet and your bank manager happy. But, from a human performance angle the best type of mountain bike for a prolonged or multi-stage race is a full suspension rig that allows you to remotely adjust the suspension status in order to match the demands of the trail.
At long last the deliberating is over. You now have all the statistics you need to justify buying three bikes.
John Metcalfe is the author of Mountain Bike Fitness Training and runs the useful Offroad Media wesite which you can link to from here: http://www.offroad-media.co.uk
Last Updated 30-05-2002
You can contact me at James@OffroadAdventures-Online.com
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