The impact of body mass on riding DH

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The impact of body mass on riding DH
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flag losidan
Posted: May 27, 2020 at 3:32 Quote
Hi

What is the impact of bodyweight when riding a DH track on a DH bike? Accepting a rider has a specfic level of skill and fitness (which we know are their own influence on ability to navigate a DH track at speed) what does it change?

Lets say for instance a rider weights 95 kilos (210 pounds) versus the same ridrer at 85 kilos (185 pounds) on the same track, same conditions, level of skill, same bike (all be it set up accordingly to new body weight) and fitness.

What is the positive or negative impact on how the rider gets through the run?
flag muddytreker
Posted: May 27, 2020 at 4:27 Quote
truffle shuffle : )
flag Loki87
Posted: May 27, 2020 at 11:04 Quote
May i ask why you´re asking this question?
Imho this is something that cannot be answered, although it may be an interesting question if we can isolate why you wanna know this.
The problem is that with the premises you give, they do not work out in the reral world.
The two riders cannot have identical levels of fitness etc. while differing that much in weight. Like, the heavier guy obviously needs to be stronger to move his body at the same speed etc as the lighter guy. This increase in strength will affect certain riding situations where excess strength comes in handy. Also them being exactly equal except for weight doesn´t work as one has to either be fatter, have more muscle or be taller to have that added weight. So identical fitness levels aren´t possible. You get where i´m coming from with this?
It´s a nice hypothetical but pretty quickly runs into problems as the human body is an extremely complex system that cannot be broken down to such a fundamental level.

That said, what i think can be said is that there are certain body types and a certain weight range that in theory are beneficial to riding downhill. Big lanky dudes can have an advantage on tracks that require the rider to carry a lot of speed and their long limbs with the added "suspension travel" come in handy, whereas shortish guys like Danny Hart or Sam Hill seem to favour tracks with rapid direction changes and more tech. This is however also highly theoretical and we´ve been proven wrong often enough by guys like Greg Minnaar or Troy Brosnan.

Another thing i think i noticed over the years is that bigger/taller guys (maybe also heavier?) tend to wreck less spectacularly in techy terrain. I´m not sure whether this is down to their riding style (more controled) or simply the fact that their mass carries more momentum and their long limbs allow them to compensate more for certain errors. It just seems to me the smaller guys get thrown off the bike easier, whereas the bigger dudes tend to stay attached to the bike more often and sometimes can ride stuff out. On the other hand this may simply be a necessity for them, as they cannot just bail as quickly as the smaller guys and of course most of those bigger dh riders are pretty strong guys as well, so this may also be a factor.
This however shows again how difficult it is to isolate a single factor. There´s just so many confounding variables that play into how the system of bike and rider interact.
flag losidan
Posted: May 28, 2020 at 0:10 Quote
Loki87 wrote:
May i ask why you´re asking this question?
Imho this is something that cannot be answered, although it may be an interesting question if we can isolate why you wanna know this.
The problem is that with the premises you give, they do not work out in the reral world.
The two riders cannot have identical levels of fitness etc. while differing that much in weight. Like, the heavier guy obviously needs to be stronger to move his body at the same speed etc as the lighter guy. This increase in strength will affect certain riding situations where excess strength comes in handy. Also them being exactly equal except for weight doesn´t work as one has to either be fatter, have more muscle or be taller to have that added weight. So identical fitness levels aren´t possible. You get where i´m coming from with this?
It´s a nice hypothetical but pretty quickly runs into problems as the human body is an extremely complex system that cannot be broken down to such a fundamental level.

That said, what i think can be said is that there are certain body types and a certain weight range that in theory are beneficial to riding downhill. Big lanky dudes can have an advantage on tracks that require the rider to carry a lot of speed and their long limbs with the added "suspension travel" come in handy, whereas shortish guys like Danny Hart or Sam Hill seem to favour tracks with rapid direction changes and more tech. This is however also highly theoretical and we´ve been proven wrong often enough by guys like Greg Minnaar or Troy Brosnan.

Another thing i think i noticed over the years is that bigger/taller guys (maybe also heavier?) tend to wreck less spectacularly in techy terrain. I´m not sure whether this is down to their riding style (more controled) or simply the fact that their mass carries more momentum and their long limbs allow them to compensate more for certain errors. It just seems to me the smaller guys get thrown off the bike easier, whereas the bigger dudes tend to stay attached to the bike more often and sometimes can ride stuff out. On the other hand this may simply be a necessity for them, as they cannot just bail as quickly as the smaller guys and of course most of those bigger dh riders are pretty strong guys as well, so this may also be a factor.
This however shows again how difficult it is to isolate a single factor. There´s just so many confounding variables that play into how the system of bike and rider interact.

Thanks for your reply and some interesting notes. To answer your question my original post was to get a feel for the time I am effectively costing myself by being "on the larger side". While I understand there are definite benefits to not having an extra xx kilos of weight to carry up a hill and more importantly down a race track I wanted to know what in effect those loses were.
flag R-M-R
Posted: May 28, 2020 at 0:34 Quote
Imagine riding while wearing a heavy backpack. Not a hydration pack, but a multi-day camping backpack. Pretty clumsy and tiring, right? Now imagine you could remove that backpack from your body. That's the difference.

The biggest limitations will be your agility, your "load multiplier", your stamina, and risk of injury.

• Agility: You'll be able to "hop and pop" all over the trail in ways not currently possible.
• Load multiplier: The ratio of your static load (body weight) to the maximum force you can sustain. A light, fit rider can support a few times his body weight before he collapses; a rider carrying considerable non-lean mass cannot.
• Stamina: It's a lot less tiring to not be wearing that big backpack, especially in hot weather, which I'm sure you experience at least once every year or two. Wink
• Injury risk: Having less mass makes it less likely you'll crash for the three reasons mentioned, plus you won't hit as hard when you do.

It's difficult to quantify these factors.
flag Loki87
Posted: May 28, 2020 at 4:41 Quote
As R-M-R stated, your riding will improve with every kilogram lost. And since you will most likely need to do some exercise to lose the weight, there will be other benefits as well.
All these things will definitely make you a better, faster and safer rider. As he said it's hard to quantify but definitely not hard to notice.
Improved core strength paired with less weight for example will reduce the amount of crashes you have and also improve your cornering and general bike control. Stronger legs and a stronger back, paired with reduced weight will let you maintain a good posture for longer, which IMHO is a huge problem for many people who tend to crouch up in stressful and technical situations to fully engage all their muscle groups while it would be better to stay more relaxed and upright. This does however require the before mentioned strong core and legs.
In the end it's all about functional strength and how your body is tailored towards the sport. A bodybuilder will be relatively strong and heavy, yet this strength likely won't benefit him much for downhill. A crossfitter body type will be much more suited to the requirements of downhill riding. And without trying to be mean, being overweight will never give you any benefits Wink

A good analogy IMHO are MMA fighters. They require stamina, power and quickness and the ability to dig deep for at least five minutes at a time which is pretty similar to a downhill run. The lighter weight classes are noticeably better suited to the task of fighting compared to heavyweights where many contestants show fatigue and a drastic decline in movement and speed after the first minutes. Getting slower means your reaction to attacks (terrain) get worse (as well as your reaction time in the event of a crash). Your less able to do the task at hand and also to protect yourself.
If you really wanna see the difference between the different body types in action, go watch some UFC fights and you'll soon notice what I'm getting at.
So in essence, being heavier won't give you any noticeable benefits, but getting fit and loosing weight will absolutely improve your on bike experience.
flag splayleg
FL
Posted: May 28, 2020 at 5:24 Quote
Plus think of the aerodynamic gains from riding in those little mma shorts alone
flag Loki87
Posted: May 28, 2020 at 6:49 Quote
splayleg wrote:
Plus think of the aerodynamic gains from riding in those little mma shorts alone

You´d have to pull a roadie and shave your legs though for that to have a noticeable effect!
flag bigburd
Posted: Jun 3, 2020 at 2:35 Quote
Not only weight but height comes into play too, I'm quite tall at 6'3" but light at 165lbs, and I get so much wind drag compared to my shorter riding mates who weigh roughly the same as me when at high speeds, if it's a straight line like a fireroad I can see them starting to pull away from me, I seem to get affected in the air quite badly by wind too, while I'm not broad/thick I still have a big windsock effect when getting hit by side winds.
flag nj82tj
Posted: Jun 11, 2020 at 20:44 Quote
I had a 20 pound difference between two riding seasons. My biggest issue was my quads would fatigue. 20 pounds later and I’m not sitting my ass down on the flat sections or slowing down in the berms. 20 pounds lighter makes a huge difference in a positive way.
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