According to my mate, and it’s starting to get on my nerves (let’s call him Stan). He’s barely ridden in few months and is chronically unfit but he’s signed up to race the Redbull Foxhunt so he’s been getting out on the bike a bit and I’ve been heading out with him to give him some “friendly” encouragement.

He’s not the fat one though. In fact I don’t think he’s 10 stone. He has another riding friend who is maybe 6’2 and just shy of 20 stone and has a similarly chronic lack of fitness (let’s call him Ollie). When they go out together, apparently big Lou leaves him for dead on single track if there’s even a slight downhill gradient.

I’ve argued that he’s maybe just a slightly better rider, off the brakes a bit more and knows how to carry speed but no. It won’t sit with Stan at all .

He concedes that in actual DH racing skill and stamina play a bigger factor than rider weight, but is insistent that on singletrack where (at least in his mind) skill is less of a factor, the big rider will always have an advantage.

I thought I would throw this one out to the STW collective and see what gems are unearthed.

Can we not call your big mate Ollie?

We can. Edited.

Sounds like bull shit to me.

If they both pretty new to it, they’re not going to be railing the turns or hitting doubles etc so 90% of the ‘action’ is going to be on the straits.

I’m 16st one of my riding mates is 12st, given a straight line with a bit of gravity I just pull away, of course when the bends come he can brake later and expend less energy doing so and puts less load on the tyres around the bends.

well Ollie would have more mass and hence potential energy at the top of a slope but I’d imagine that all the other factors, wind resistance, skill, tyre pressure, rolling resistance etc make the picture so complicated that it makes next to no difference in reality.

I reckon just get Tracey Moseley to give him a schooling and tell him to shut up.

I’ve known them both for at least 7 years or so they’re not new to it. But I wouldn’t say they are “railing”.

thestabiliser – Member

well Ollie would have more mass and hence potential energy at the top of a slope but I’d imagine that all the other factors, wind resistance, skill, tyre pressure, rolling resistance etc make the picture so complicated that it makes next to no difference in reality.

That’s my take on it too, along with parasitic drag from the drive train and god knows how many other factors.

thestabiliser –

I reckon just get Tracey Moseley to give him a schooling and tell him to shut up.

I’ve tried demonstrating this myself by pulling away from him without pedaling but this just adds fuel to his fire because I’m 12 stone and change.

Would that be Stan and Ollie from England? I know them. Say ‘hi’ for me.

I ride with a bloke who’s about 3 stone lighter than me. If we sit on a DH fireroad, he pulls away. I put it down to the tyres and hubs (rightly or wrongly).
On singletrack I’m gone in no time (he’s a fairly new rider).

The bigger rider only has an advantage if he stays of the brakes and carries speed better, shirley?

Even on simple singletrack the more skilled rider will pull away. Fire roads he may win if no one touches their brakes and gravity does the job.

The skinny guy would catch the fatty on the way up most likely if they have similar biking fitness levels.

I find that I freewheel faster than lighter friends when I have similar tyres on.

This may be partly due to having to run higher pressures to avoid punctures.

When I run slower tyres, I’m slower though.

The tyres will certainly make a difference on singletrack even where it mostly comes down to skill/commitment, just that bit easier to accelerate/roll on the straights adds up over the course of a trail.

Does your lighter mate have particularly burly tyres fitted?

Imagine setting a bowling ball rolling from the top of a hill. Thats me, that is 😀

I remember riding a few of the marathon events in Wales a few years back. The same XC race whippets that come flying past you on the climbs, wouldn’t half get in the way when gravity had switched alleigences

I’d bet that even if you ignored friction, over 200m even falling vertically, a difference in mass of 63kg wouldn’t result in a huge difference in acceleration.
Haven’t time to do the calc though, sorry.

philjunior

Does your lighter mate have particularly burly tyres fitted?

He’s got 2.3 Bontrangers that came on his Trek Slash. Ollie generally runs bigger tyres too, usually 2.5 Maxxis from memory.

warpcow
The bigger rider only has an advantage if he stays of the brakes and carries speed better, shirley?

Think of sports cars. If the car is twice the weight it takes a lot more braking power to slow down and a lot more power to get back up to speed.

Who’s Lou in this and what are his vital stats?

lobby_dosser – Member

Who’s Lou in this and what are his vital stats?

Sorry ignore that. That’s Ollie too. I decided with prompting to edited their names for more comedic effect but Lou/Ollie are the same person. Lou is the first syllable of Ollies real name.

He’s a big guy, at a guess I’d say he’d be a pretty lean 15 stone, last I saw him he was a slighty overweight 18ish. Now he’s apparently a wheezing, puking 20 stone.

Yeah I tend to run big tyres (2.2-2.5in, from various manufacturers which are all roughly the same size in the real world), but the individual tyre will make a difference.

I have some dual ply DH supertacky tyres, these roll very slowly.

I also have some lightish (still full knobbly) Shwalbes that are running tubeless, and roll very well.

Even my semi slicks at 2.15 and 2.3 (they come out very big for the size) roll noticeably differently primarily because the 2.3 has reinforced (but still not DH dual ply) sidewalls.

So whilst the rider weight will make a difference, your 10st mate can probably make himself go faster by fitting faster rolling tyres (which he won’t wreck or puncture all the time on due to his low weight).

Of course he might just be a massive mincer as you imply.

why has no one asked what wheel sizes Ollie and Stan are on.

Assuming they’re pedaling, fatboy can probably put down more watts.

On a fire road descent, just rollin, I am faster than my 4 stone lighter riding buddy, i just start to pull away due to gravity.

But he is faster than me up hills because he is fitter and faster than me on singletrack because he rides every week a few times a week, whereas I ride mtb every now and again nowadays. If i rode as much as him we’d be about the same level on single track.

Stevet1 – Member

why has no one asked what wheel sizes Ollie and Stan are on.

Both 26″. Stan’s on a trek slash, Ollie’s on a Spesh hardtail setup single speed.

[video]https://youtu.be/UGiZH-eqM14[/video]

Bigger riders being faster downhill makes sense to me. Slightly higher area but much greater mass. (That’s my small animals use a much higher proportion of their calories keeping warm)

I’d seen it to be particularly evident on the road where the higher speeds obviously have a bigger effect of wind resitance to momentum.

Having said that, it should only have a small effect on initial acceleration as wind resistance is tiny.

Does anyone know if the higher mass at the top of a slope overcomes the inertia of the bike and rider’s mass and the wheels?

Well if stickman can’t go faster down a hill on a slash than someone on a hardtail (SS!) he’s just going to have to face it that he’s crap.

thestabiliser

Well if stickman can’t go faster down a hill on a slash than someone on a hardtail (SS!) he’s just going to have to face it that he’s crap.

I made this point too. FWIW I’d say they are roughly similar in skill but Ollie is braver imo. He’s one of those guys, a bit of a kamikaze pilot I suppose. Crashes a lot.

Stan cannot abide the idea that Ollie might be faster than him ( Ollie has started showing him lines etc much to his annoyance) and I think he’s clutching at straws to explain his lack of pace. Instead of say, getting out on his bike more.

It’s like dropping a rock and a feather of a cliff!

warpcow
The bigger rider only has an advantage if he stays of the brakes and carries speed better, shirley?
Think of sports cars. If the car is twice the weight it takes a lot more braking power to slow down and a lot more power to get back up to speed.

I think I’m agreeing with you, but am mostly just tired and confused and haven’t had any coffe yet.

warpcow

I think I’m agreeing with you, but am mostly just tired and confused and haven’t had any coffe yet.

Yes, sorry. Me too.

It’s why the top pro’s DH bikes are made out of lead made to look like carbon fibre.

I don’t buy the heavy=fast logic.
Yes it would be true if both were rolling down a smooth incline, but who rides down smooth inclines?

The lighter guy can hit rocks at more speed without pinching or buckling a rim. He’s better equipped to float over stuff so will carry the speed better.

My riding buddy is much quicker than me nearly everywhere and he’s a good 2 stone lighter, he just a much better rider. Sometimes I can freewheel down a road hill and he’s pedalling to keep up but mostly he’s just way faster than me 🙂

I agree fully with the skill being a massive advantage when in twisty skill testing singletrack.

Just thinking of a bit of singletrack near me that I know very well and is only on the very slightest of gradients and twisty enough to require braking. I can freewheel down it and easily drop a fairly novice rider who can pedal all they want. In fact they could have the pedalling power of a chemically enhanced Lance Armstrong but if they can’t take the speed through the tight corners there’s not enough opportunity for them to make up the time in-between. This can equally apply to DH stuff and anything technical.

So perhaps your mate’s large mate is actually a very skilful rider.

But other than carrying a bit of extra potential energy, I can only see his extra bulk as a hindrance.

A fit heavy rider will generate a lot more power than a fit light rider, generally. So as soon as gravity is out of the picture size helps a lot.

The fat guy is just better at the trail, or they are both crap if the only difference is down to weight of the rider. IF it was down a straight trarmac road weight would matter but on a technical trail if your weight or lack of weigh is holding you back its really a sign of skill level, or lack of skill level.