The Great Weight Debate: Minimum Weights To Be Reduced Soon In MotoGP

The news that 340mm carbon brake discs are to be allowed once again in MotoGP has rekindled a debate that has been going on behind the scenes for some time. The move to allow the discs at all tracks, and not just Motegi where they are already compulsory, has come as both power and weight of the MotoGP machines has grown over the past three years. But the real solution lies in reducing minimum weight.

There was a certain irony in the moment chosen by the Grand Prix Commission to ban carbon discs larger than 320mm. The move – made for reason of cost savings and rationalization – came just as MotoGP was to return to 1000cc, meaning the bikes were about to reach higher top speeds. Compounding the problem, the minimum weight was also increased. The initial proposal was to raise the minimum from 150kg, the weight of the old 800cc machines, to 153kg. However, to make life easier for the CRT machines, the weight limit was raised even further, in two steps, to 157kg in 2012 and 160kg in 2013.

In the space of two years, engine capacity had been increased by 25%, leading to a power increase of around 10%, while weight had also been increased by nearly 7%. It was a recipe for brake problems, and that is precisely what occurred. Ben Spies lost his brakes at Motegi in 2012 – and spurred making them compulsory at Motegi for 2013. All of the Yamaha riders spent 2013 complaining of a lack of braking power, and Cal Crutchlow is still struggling to deal with braking on the Ducati Desmosedici GP14. Allowing 340mm brake discs is the quickest and most immediate fixes, but for the long term, minimum weight needs to be reduced once again.

Such a move is likely to come sooner rather than later, with weight reductions a racing certainty for 2016 when the new set of MotoGP regulations comes into force. With the production-based CRT machines now gone from the scene, a more generous minimum weight is no longer necessary. The new generation of Open class machines are much closer to the factory prototypes than the bikes they replaced, meaning that weight reduction would be relatively straightforward. Even the production-based Open class machines – the Avintia Kawasaki and the ART and PBM machines, using the Aprilia RSV4 engine – are much closer to prototypes after a couple of years of development.

How much will the minimum weight be reduced by? At Jerez, Race Director Mike Webb told us that they were examining proposals to reduce the weight to either 155kg, or perhaps even 150kg, though the former was much more likely than the latter. Both weights are achievable, as is even less. Asked for his opinion on what was manageable at a reasonable cost, former FTR chassis guru Mark Taylor told us that any decent engineer worth his salt should be able to design a MotoGP machine that came in at 150kg. Less than that was more difficult: when asked if 140kg would be feasible with resorting to extremely expensive materials and techniques, Taylor said that it would be possible, but expensive.

The main reason behind the looking weight reduction is not just about braking, however. There is an even more pressing concern than that. As both speeds and weights have increased, so has the distance which bikes travel after they crash. A MotoGP machine traveling at high speed is a massive store of kinetic energy. Accelerating it to 350+ km/h takes an enormous amount of energy. Slowing it down requires the same amount, but applied in reverse. Current run off technology – hard standing, then gravel traps, and then air fences – has reached its limits, with air fences only serving as a catchment of last resort. Ideally, the bike and rider should already have come to a halt before they reach the end of the gravel trap, and not have to use the air fence.

In the past, the barriers where air fences are placed have been moved further and further back, but that process is extremely expensive, bad for spectators (who are further away from the action) and at some tracks, becoming increasingly difficult. Some tracks are simply running out of space to move the barriers further back: Sachsenring's Turn 1 already closely abuts the section between turns 10 and 11; the Ramshoek at Assen has already had the runoff extended almost into the paddock; San Donato at Mugello, at the end of the straight, sits underneath a massive hill, necessitating major excavation work to try to create more run off. If speeds continue to increase – both corner speeds and top speeds – then MotoGP will simply run out of tracks where it can race safely.

There are two solutions to this problem. As kinetic energy is defined as ½mv², the most effective way of decreasing the distance a crashed bike will slide is by reducing the speed at which it crashes. As velocity is an exponential component of kinetic energy, reductions in speed have huge consequences. However, limiting speed is difficult: Dorna are keen to impose a rev limit to cut down on top speeds, but that solution may end up driving up corner speeds once again, as the capacity reduction to 800cc did. Any reduction in top speed would require a similar reduction in corner speed, and that can only be achieved by reducing grip, both by reducing complexity of electronics, and by reducing the performance of the tires. The arrival of Michelin, who come to the series after a period of absence, should give the series a short respite. However, at some point, the French tire manufacturer will start to match the performance of the current generation of Bridgestone tires, and then the series is back at square 1.

Reducing weight has a much smaller effect – the relationship between weight and kinetic energy is arithmetic, not exponential – but it is much easier to implement and to police. All three manufacturers are adding ballast to reach the minimum weight, in some cases switching from titanium and other exotic materials to stainless steel for some components to add weight. Removing ballast would require a lot of set up work and some minor redesigns, but it would not present a major engineering challenge. With a new tire supplier coming in 2016, along with new, standardized and more limited electronics, that season would seem to be a good point to start reducing minimum weights. It is just a question of time.

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How ironic that in such an elite moto sport the wheel just keeps going round and round!

Reducing the mass of an object at a given speed reduces its kinetic energy. But reducing the mass of an object will also increase its acceleration with the same force applied to it. So reducing the weight of a MotoGP bike will increase its power to weight ratio and its velocity at the end of the straight, which would offset the effect of the weight reduction somewhat. A reduction in weight by 10 kg reduces weight by 6.25% which will decrease in the kinetic energy directly proportionally. Let's say that also increases speed at the end of the Mugello straight by an average of 5 - 10kmph, not unreasonable given corner speed onto the straight will also increase with less mass, that's an average velocity increase of 1.4% to 2.9% given a top speed of 340kmph. Given Ke is proportional to the square of velocity the weight decrease would only acheive a net decrease of kinetic energy of the bike minus rider of 3.5% to 0.65% rather than 6.25%. Adding the rider weight to the equation further reduces the overall effect of the weight reduction. And when you consider corner speeds would increase you have to wonder whether the weight reduction is a worthwhile safety initiative. I'd still like to see it happen though as IMO when you increase the power to weight ratio you also increase the skill required to ride the bike at the limit, which would be a good thing in the world's premier motorcycle racing category.

Don't aerodynamics have a much greater effect on top speed than weight? Admittedly they will get to their top speed sooner if they are lighter, so I suppose the run off area at some of the tracks with shorter straights may become more of an issue than it currently is, but they would still have more effective braking.

How big or small you are shouldn't be the determining factor in any class.

Back when the AMA was running US Superbikes, the big twins (Ducati 916/996/999 & Honda RC51) had a minimum weight vs the I-4 750's (Suzuki GSX-R & Kawasaki ZX-7R). Miguel DuHammel said that it took some work to place the extra weight, but when they got it sorted, it actually improved the handling of the bike.

Rules like this are sure to help guys like Scott Redding & Rossi and might have helped other bigger guys if it were implemented when the MotoGP era kicked in.

If they actually do it, it will be interesting to see how or if it has any impact.

But this article isn't about combined weight of rider and machine, it's bike only.

I personally agree that there should be a minumum combined weight, as used in Moto2.

But there lays a huge debate....

The physical aspects of weight in relation to racing is that less of it is a good thing. A lighter bike brakes shorter, accelerates quicker and corners faster. It makes sense to set the minimum weight for bikes at a level that will challenge the engineers to meet it. This will move the technology of bike construction forward which is the goal of prototype racing.
This doesn't address the issue of combined rider/bike race weight which is more of a sporting concern.

I do take your point about being prototype racing, and agree.

HRC have the biggest clout and will get the best materials. You can't just go into Kobe Steel and buy Ti as you want, unless you have clout.

There is also the limiting returns. Everyone gets so worked up about Ti (which is usually alloyed half with Al), when a Steel exhaust just does fine for a fraction of the cost. F1 even used 0.7mm Monel exhausts! Same with Cr-Mo tube. Factional gains at the expense of, well expense and manufacturing difficulties.

The proof should be in the transference of technology to road bikes. We don't see carbon fibre wheels, discs or fairings, nor magnesium wheels commonplace. Ti valves for a Katana are $150 ea compared to $30 for steel.

Our production bikes, on the whole are cast and forged aluminium, steel and plastic, which is a good thing from longevity, cost and maintenance.
I still can't use 100% throttle for more than a few % of the time!

I wish someone would explain to me their logic behind addressing minimum bike weights but not addressing combined bike/rider weights. I've heard all the arguments to why Pedrosa for example does NOT have an advantage (eg weight offset by less strength, can't move weight around as effectively, etc), but there seemed to be a wide range of opinions on that.

What's the real deal? Some of these riders are looking a bit unhealthy in their scrawniness as it is, and I am sure that is driven by weight management. Would only get worse with lighter bikes wouldn't it?

It seems that a combined rider/bike weight would make more sense. Lowering the bike will only really help guys on the edge of weight, those guys that are heavier still will have brake issues.

Combined mass and blah. Hearken back to the days when any rider and self fancied GP racer supreme felt the awakening and calling to compete. The first thing most wanted was a universally accepted piece of tackle with which to compete on a level playing field. I really do not recall at any stage Kenny Roberts, Barry Sheene and Wil Hartog back in the day comparing extremities and demanding FIM(GPC current) compromises.
The last time MGP was truly 'open' was actually pre-season testing 2007. Tyre war, rev limits and sundry bunkum was not an issue. Right now GP is an absolute mess of note. I have no solution and could not be bothered anyway. Once the 500 2-stroke era had run its 25 year course, the writing was on the wall. Corporates and their lackey's tow the corporate line.
I'm not about to reverse the clock. The situation is what it is. M3 is fine, M2 descending and MGP, WELL !!!
Hindsight being 20/20 vision, there was actually nothing wrong with 800 in the first place, was there? The 4-stroke era lost its grip as early as 2008 when the rubberside down issue was breached within the ambit of compettitivenes viz a viz rubberside down. Would that MGP could employ M3 baseline rules sans a single tyre manufacturer.
2016, 2017, whatever. I will smash another screen come Sunday should I see another 4th bike parc ferme whatever bike in the ring.
What are the GPC exactly conveying to the casual viewer?
The bloke and bike that came 10th actually beat the 6 ahead of him or what?
Spurious signals.
Anyway. Too big and fat and old refers to topic. Get on a trike and ride shotgun for MGP upstarts. This game desperately needs fresh blood, young blood and a system that does NOT embrace the bottleneck/rider plughole at the top of the bottle.
A great observation you scribed viz a viz Dani and Suz potential. He may as well collect 3 mil Euro is about the target I'd suggest as a compromise and get out of HRC. With Marc intact and riding so comfortably, he may as well. Dani is on the same level of track as Loris. The pair set the world alight in junior classes. Both came ever so close to achieving the big one at various stages of their careers, especially Loris in 2006, Dani 2012.
David, enjoy the ride and Mugello.
They call Assen, the Cathedral of Speed. Thats a romantic notion.
Mugello is IT! The absolute highlight for me season in season out.
Are you running 340mm or 320mm rotors on the GS?
Safe weekend and enjoy.

I wasnt into the sport during the 800 era, but it seems to me like the reduction in power made things a lot easier. Heck, for a long time the qualifying lap records were from that era. I think capping power and enabling more balance rather than making everything revolve around managing tires saddled with the burden of 250HP makes more sense. Hopefully 2016 will come with rev limits.

Kenny Roberts, Barry Sheene and Wil Hartog never had to deal with these fuel rules. If you are going to limit the fuel (frugal limits) then a combined rider/bike weight should be the standard. At 24 liters, it doesn't matteras much, but it sure does matter right now. The mites have an advantage. It exists in the smaller classes so it should in MotoGP as well.

>>The mites have an advantage.

There's been research on this topic on this website and there is no statistical correlation between rider weight and number of wins. Especially this year, Rossi is one of the larger riders and one of the most competitive. None of the factory entries have run out of gas and the Yamaha open bikes with 24l are doing nothing special with lap times or top speeds. Fuel and weight are nice distractions to discuss but with any given set of rules the results would look the same.

>> It exists in the smaller classes so it should in MotoGP as well.

I club race without combined bike and rider limits so MotoGP shouldn't either. Both statements have little to nothing going for them as far as relevance to rule writing.


Fuel limits are sh*t.

The era we are just wrapping up of less fuel, fewer engines and GOBS of electronics has nearly driven me mad.

GAAAAAAARRRRRGH! I can hardly see reference to fuel limits in print anymore w/o fouling my trousers.

Carry on. Weight limits: sweet spot is lighter than now, powers that be please make it so. AND GIVE EVERYONE 24L for the sake of all that is good. Holy crap, is it THAT hard to see this and just put pen to paper?

I can promise you each rider and each mfg is as light as they can be within reason and the rules. Any mfg would make their bike lighter if the rules allowed. Most all of the riders are quite serious about their fitness and weight including some pretty scary diet "aids". A combined weight would be fair.

If one argues that more weight is better, the rules don't have a maximum.....(I don't think).....add weight Dani!

The 990cc MotoGP era was an incredible high that shouldn't have ended abruptly in 2007; however, it's nearly impossible to argue that the 21st century reboot of GP and SBK created net-positive long-term effects on the motorcycling industry.

If overwrought, high-tech behemoths are responsible for the decline of the production market and the racing industry, I'm open to any proposal that appears to chart a different course. Less grip and less weight seem reasonable. Now they need to figure out how to regulate the engines without so much restriction and uniformity.

Once the rider comes off the bike, the KE of the rider is not affected by the bike. The bike may not slide as far if it's lighter, but the rider is sliding separately and will slide just as far as he would have before the bike lost 10kg. Reducing bike weight and increasing brake disk diameter may improve braking, but won't help if a failure puts the rider down at the start of braking which is the worst case scenario we need to plan for.
Easiest way to reduce straight speeds is to reduce the corner speed, because the rider slows sooner to make it around the corner. Given that we will be switching tire suppliers, why not reduce tire width at the same time? Less width means a smaller contact patch, which means less grip, which means slower corner speeds. Of course the riders won't like less grip, but it's an easy fix.

If the bike is lighter but has the same horsepower, why won't speeds increase? Isn't this like cutting off your head and standing on it to be taller? Maybe we just need more chicanes ...

No, not the power required goes up with the cube of the velocity.
This is why Bonneville cars have lots and lots of power and this is their main goal for performance increase.

Some great ideas, but why not attack the real problem with real physics.

MotoGP has some very strict "shape" laws (after dustbin era), easy to mandate a set Aerodynamic Frontal Section "Big Boy Bikes", as velocity is raised to the cube in proportion to power. Make the bikes a bit porker, also a higher front screen. Cheap to do and police. Aero IS the great limiting factor to top speed.

Why not reduce the gears from 6 speed to 5 speed? ...maybe even a specified final drive ratio. Easy. More focus on torque (which is tyre limited anyway) and provides scope for variation between bikes in their balance. Better for racing.

I'm also perplexed why WSBK bikes, that have similar lap times (all be it, slightly lower top speeds) than MotoGP successfully use Steel discs...on similar circuits (Philip Is, Donnington etc.). CF allow light mass and short/sharp stopping distance. Wouldn't increasing the stopping distance (you still stop) and putting less load on the front tyre be beneficial to racing and the step up from lower classes?
[I'll interject that at the Philip Island classic, an 80's Katana with good old rider can do a 1:37 with 2 pot AP's, compared to Moto2 1:33 and MotoGP 1:28/1:29]

And finally, riders, on the whole, crash on corners. Most changes to regs have led to higher corner speeds. That said, corner speeds (from sector times only) are not that vastly different from the lower classes (it would be good to see some proper data).

..oh, and ,Hermann Tilke. He's the one for these stop & go (F1) circuits, not the sweeping curve circuits of old.

I believe all of those proposals were pitched at the end of the 990cc era, but the MSMA (Honda) were not interested.

Loris Capirossi, MotoGP´s Safety Advisor- Anyone know if he has had any direct affect towards implementing any real changes for the better, or mostly a PR face?
I wish they would go through the whole book and maybe, perhaps, revise or slacken up a few parameters both ways in regards to improving safety whilst not directly increasing overall performance relative to everyone else (not outright cheating).
This season has been fun so far :)

If there was one pain-free control item this might be it. Dorna should supply free fuel. Nominal 97 octane max., street fuel, ethanol included.
Use as much as you like. Not a great expense.Power and speed will come down. Race weight might go up.
Let F1 do the fuel R&D.
Sponsors shouldn't mind too much - the lubricants seem to be their main area of interest.

If you must lay law only to have a continues change of it, then it looks to me like the ones laying it down are not very good at their job, or are not telling the truth. Keep it simple!

For safety, how far the bike slides is less important than how far the rider slides. Almost always they come apart at the beginning of a crash. I don't really care if the bike itself hits the air fence hard. Cutting bike weight by 5 or 10 kg will boost acceleration and delay braking points, both of which tend to increase the speed at which a crash occurs. That is bad for rider safety.

On the combined bike + rider weight, I favor it because I dislike the way the sport tends to select tiny guys, and dislike that it forces near-anorexic behavior. When your example of an exceptionally big guy who is successful is Valentino Rossi at 65 kg (143 lbs), well I think that is a problem. I'd rather build in 75 kg for rider (including leathers, boots, helmet, etc).

The normal size guys (most if not all) drop too much weight IMO, compared to the below average height guys and the mini-me's.
I think being fit, able, and having a very high level of physical endurance/stamina is great, if not an absolute must! But, getting down to weights just for the sake of "making an extremely idealistic weight target" are just silly if not also unhealthy. I'm 6' 1.5" tall & about 180-185lbs. and I've always had full boost turbo metabolism lol...
Bottom line... Them boys need to all hit the buffets they can find! lol :)

At building a tire which can last. Lost in all the squares and roots above is the tires must put that stopping power to the ground. A weight change will also help with lesser stiff side walls. Bridgestone problems only really started in the last years with added weight and big bikes. Michelin do not want the same problem the others are walking away from.

The first class in GP motorcycle racing with a combined weight (bike + rider) was the 125 class. The Moto2 class also has a combined weight limit, as does Moto3. And I believe (care to correct me) that F1 auto racing also has a car + driver weight limit. So if the MotoGP rule makers are leaning towards a 150kg weight limit for the bike, perhaps they should factor in 75kg for the rider (helmeted, booted, gloved and leathered) and come up with a combined 225kg weight minimum. That way, teams with riders lighter than 75kg would have to add ballast to their bikes and those with riders of more than 75kg could reduce the weight of their bikes. By the way, is the current weight limit with, or without, fuel?