My physics reasoning is failing me on this.

If two riders of 70kg and 105kg (so 50% heavier) set up their bikes of equal travel, appropriately for their identical riding style and preferences, will the heavy rider’s bike be less comfortable?

Take landing a drop, there’s a lot more energy to go into the spring and damper, does that mean it’ll be a harsher hit being transferred to the rider? It seems to me that for a spring to store a given amount of energy, it’d be more comfortable to compress a longer but softer spring because you can take more time to compress it.

Or consider riding over a small rock, will the heavier rider get more of a kick through their handlebar or saddle due to the stiffer spring they’re running? It seems that if you run a hard spring for the weight on top, then it’s going to be less sensitive to impacts coming from below.

Just out of interest. It’s not that I’ve put on weight and am looking to justify a new bike, I promise.

Get a G1. Long travel very well controlled. No reason to ride shorter travel especially a big lad. Go get a demo ride.

No I don’t think so.

The “comfort” will come from the deceleration when hitting the ground being the same in both cases.

Both bikes will fall at the same vertical speed and so will hit the ground at the same vertical speed.  If they then reduce this speed to zero across the same suspension travel they will both feel the same deceleration and so the same “comfort”.

But to achieve this the 105kg rider will need a suspension about 50% firmer sprung than the 70kg rider.

That makes perfect sense for the drop scenario J-R. I felt something was wrong in my reasoning.

Thoughts on the firmer spring’s effect on riding over a rock or into a square edge?

Isn’t all that a function of the damping control? I guess for unsophisticated forks or shocks you might have a point but,for half descent forks/shocks, you can adjust compression and rebound damping, add/remove tokens and/or play around with shim stacks or oil weight.

So no, I don’t think fatties need more travel, though they are more likely to break fragile lightweight XC race bikes which tend to shorter travel

Interestingly enough the Raaw Madonna has two different rocker options, one for under 90 kg rider and one for over 90 kg.

J-R. I think there is another layer to it. What you type works if the load (rider) is a passive solid lump. But it’s a flexible human. The rider needs to resist that deceleration force with their arms and legs so that as the bike gets to the bottom of the travel the rider does not ‘buckle’ at the wrists, elbows and knees’ and carry on into the bike. The fat lad is carrying more kinetic energy. Longer travel suspension translates into a greater length of time for the deceleration to happen so it will be slower, reducing the forces the rider must resistance. The total energy transfer is the same regardless, but the time to do it is increased reducing the forces.

If the heavy rider is proportionally stronger then the same travel would be fine. If the rider has put on weight but not increased strength then longer travel would help.

Or something.

test ride, having moved from a top spec trail bike 150/150 to a mid spec enduro 170/160

it does everything so much better, climbs, drops, jumps, flat acceleration you name it.

but, I know people who have gone big and they’ve been disappointing lumps.

A heavier rider weighs more compared to their bike so the unsprung mass (the wheels) is relatively less compared to the rider leading to a more comfortable ride (the suspension is more active)

I’ve been making the argument for years that heavier riders would benefit more from longer travel bikes. It’s not so much about “speed”, it’s about decelerating mass. More mass decelerated over the same distance puts greater force through contact points – Tyres, bars, saddle, pedals – which means a harsher ride.

A heavier rider weighs more compared to their bike so the unsprung mass (the wheels) is relatively less compared to the rider leading to a more comfortable ride (the suspension is more active)

The suspension would only be more active for the heavier rider if they both rode the same bike set up the same way.

In theory the heavier rider should have ‘better’ performance from their suspension due to having much better sprung to unsprung mass ratio.

In practice the fact that the arms and legs make up a significant part of the suspension ‘system’ (and let’s not forget the big low pressure tyres, especially if running inserts) and the answer is probably closer to ‘it depends’.

There might be some generalisations that can be made regarding rider weight and ideal suspension travel but I suspect that a rider’s style is far more important.  A rider that is more active on the bike should need less suspension travel.

Hmm, interesting, but longer-distance bikes tend to take in more energy, so bigger riders may find them more comfortable. However, regardless of the rider’s weight, good bike setup and tuning are essential for comfort and performance.

For the drop it’s the same acceleration but your heavier rider gets 50% more force as they have 50% more mass.

If the heavier rider is 50% stronger that’s fine. They get 50% larger forces when walking or running

The suspension would only be more active for the heavier rider if they both rode the same bike set up the same way.

Even if the bikes suspension was set up proportionally the same (ie 50% more spring rate and damping) the system with compatibly less unsprung mass (the heavier rider) would be more active.

You can sometimes see this when big lads ride downhill, they can plow through rock gardens and get bucked much less than small riders

Put another way, say a heavy rider rides off a 10 foot drop. A lighter rider would have to ride off a much larger drop to generate the same amount of force through the suspension. Would you think more suspension travel would be beneficial for riding off larger drops? Ask Josh Bender.

Even if the bikes suspension was set up proportionally the same (ie 50% more spring rate and damping) the system with compatibly less unsprung mass (the heavier rider) would be more active.

You can sometimes see this when big lads ride downhill, they can plow through rock gardens and get bucked much less than small riders

So you’re saying there’s an optimal ratio of sprung to unsprung mass, which means riders of differing masses should be on completely different equipment to achieve that optimal ratio? I agree.

As a fatty, you get a harsher ride. Basically due to it being harder to get the suspension damping tuned for your weight. Getting a decent compression tune from a standard fork or shock is difficult. Custom tuning dies help though.

When I say harsher, I mean for pittery pattery stuff. The suspension is never “buttery” as some folk talk about. Over big stuff, not that big of an issue.

I think you’re over thinking it.

Marketing, ability and frame strength/stiffness will have a bigger impact.

Big guys won’t be racing XC, so won’t buy XC race bikes.

Big guys will need stronger frames, so will be riding AM/Enduro bikes even if just mincing allong the trails.

Big guys are bigger and stronger (ignoring ‘overweight’ as a separate category) so could muscle through rough stuff better which goes against the original hypothesis that they would be avoiding it.  Also the light rider is probably faster regardless, you’re not being slowed down by the rocks if you’re in the air.

So I think you’re right, but only for people who buy a suspension bike for its comfort. Which isn’t why people usually buy them.

Big lad here.

I’ve found longer forks to be easier to get dialled, but not sure if that’s due to having more travel, or longer forks being more likely to have better dampers, with more adjustments.

I’ve been able to get buttery small bump sensitivity whilst also having midstroke support and enough bottom out, for +160mm forks, but not on my shorter travel forks.

But then again, I’m not rattling down the rough stuff on my shorter travel bikes, so fork performance ain’t as important.

I would assume that a top end fork or shock with a big enough range of settings would be able to set up so that it would be the same for the bigger and small rider. Cheaper suspension with less adjustments and poorer damping would be more noticeable

From a bike weight point of view I would guess that a 125kg rider would notice the slight weight increase of longer travel less compared to a 50kg rider as it would be a smaller percentage of the overall weight so there would be less disadvantage to the Clydesdale running more travel (which could give them more comfort).

The “comfort” will come from the deceleration when hitting the ground being the same in both cases.

Both bikes will fall at the same vertical speed and so will hit the ground at the same vertical speed.  If they then reduce this speed to zero across the same suspension travel they will both feel the same deceleration and so the same “comfort”.

If this was true, there would be no point in using bigger hammers to hit things with.

More mass decelerated over the same distance puts greater force through contact points – Tyres, bars, saddle, pedals – which means a harsher ride.

Makes more sense to me. Extra distance buys you time, so you decelerate slower, so less harshly.

I think you’re over thinking it.

Someone says something like this on every bike nerdery thread I start! 🙂 It’s the whole reason for the thread.

As a larger rider, fork chassis rigidity has a big effect.

my twopenneth…….

when i rode a full sus bike, i started with a Heckler with a standard coilover shock.  it was rubbish. bottomed out all the time. i upgraded the coil to a 300lb spring after speaking to Mr Flooks.  the bike was more rubbish, and far too harsh.

i changed the bike to a bike with 30mm more travel, same coilover shock, same 300lb spring. also 20mm longer travel forks.  the new bike was fantastic.  supple over flat rocky stuff, ace at speed on long rocky descents, and also seated climbing there was no bob or noticeable flex. so for me at 22 stone back then, a longer travel bike was far better.

As a “Clydesdale” (you’ll know if you’re old enough) I ride a 120mm bike and I think I’m less concerned about travel than I am flex and strength.  As I (weirdly) get more confident and capable in my late 40s than I think I’ve ever been I start to think about the potential for breakage/failure as it’s clearly not as robust in terms of general construction as a 150mm bike would be.

Speaking from personal experience – I lost just over 3 stone in 6 months whilst riding the same bike. Other than having to change the air pressures and rebound/compression settings on shock & forks I didn’t notice any other differences in the ride quality (was able to ride faster and get up hills easier though).

So I’d say rider weight makes bugger all difference if the bike’s set up properly.

In theory the heavier rider should have ‘better’ performance from their suspension due to having much better sprung to unsprung mass ratio.

I’ve noticed this effect with particularly light riders struggling to maintain momentum over rocky terrain, and heavier riders pulling away from average weight me.

But it answer to the OP, nah, that’s literally what spring and damper adjustments are for.

Genuinely not sure if the first response “get a G1” was humour. For all we know, OP was looking at XC bikes.

Can I throw in the thought that longer travel forks are usually just the same forks with longer travel?

My Pike could be run at 120-160mm and my Lyrik at 150-180mm – only change is the airshaft.

Same chassis, same damping, same rebound – just the length of travel changed.

@intheborders – I assume they mean that a Fox 34 is stiffer than a 32, 36 more than a 34, Lyric more than Pike , etc rather than comparing a 120 Pike to a 160 pike (in which case I assume the shorter Pike would be stiffer as there’s more stanchion/lower overlap).

And longer travel bikes tend to be built heavier and stronger than lighter bikes with shorter travel.

Agree with the stiffness/beefiness arguments. Flex in forks is going to hamper their telescoping nature. At 90kg dressed, my self-built bike has a 140 lyric where the stock builds come with a Pike.

Assuming someone is not so heavy or light that they are beyond the range of adjustments of the suspension then the amount of travel shouldn’t be changed to get the “same” feel between two drastically differnet riders.

Someone heavier is going to be stronger, that will make up for the harder impact.

But it answer to the OP, nah, that’s literally what spring and damper adjustments are for.

What do you say to the stuff about decelerating more mass over the same distance? I don’t think that physics reasoning can be overlooked and saying “nah”.

Genuinely not sure if the first response “get a G1” was humour. For all we know, OP was looking at XC bikes.

It was irrelevant, this is just a point of interest. It was purely about the length of travel, but the other things people have brought up are interesting.

Someone heavier is going to be stronger, that will make up for the harder impact.

It doesn’t seem to me that strength is going to compensate for the additional discomfort from riding into and over a rock with a 50% higher spring rate.

I assume

Assumption, the Mother of all ****-ups 🙂

“Mother, brother, any old f****r!”

Can I throw in the thought that longer travel forks are usually just the same forks with longer travel?

Up to a point but I ride a 120mm bike and my Rebas are at max length.  If I went up to 140 I’d be on Pikes etc I expect.

I was toying with a CRC bargain fork for a while but missed the one I wanted due to pontification.

“ If this was true, there would be no point in using bigger hammers to hit things with.”

It was true. The bigger hammer point shows you don’t understand the physics of this.

The overwhelming problem with bike suspension is that the dampers are tuned to work best over a surprisingly narrow range of weights. With custom tunes a bike will ride equally well regardless of your weight but your weight and limb length will affect your riding style.

When I weighed a bit more (only about a stone) and was doing fairly heavy deadlifts and squats in the gym I could bottom out my bike quite a lot more easily, with the same shock tune and sag. I took a volume spacer out to regain that last 5-10mm of travel because I just wasn’t getting there last year despite only being a bit lighter than a couple of years before. And that was only going from 87kg down to 80ish, not much of a change vs the range of rider sizes.

It was true. The bigger hammer point shows you don’t understand the physics of this.

Correct, that’s why I started this thread. It is actually helpful to tell me I don’t understand. Multiple seemingly contradictory yet convincing takes have been given, and I’m trying to make sense of them. My hammer point was trying to illustrate that if you hit something with a bigger weight, at the same speed, and it decelerates over the same distance, then the thing you’re hitting is going to receive more energy.

Let me look at it again

No I don’t think so.

The “comfort” will come from the deceleration when hitting the ground being the same in both cases.

Both bikes will fall at the same vertical speed and so will hit the ground at the same vertical speed.  If they then reduce this speed to zero across the same suspension travel they will both feel the same deceleration and so the same “comfort”.

But to achieve this the 105kg rider will need a suspension about 50% firmer sprung than the 70kg rider.

I stand corrected (emphasis mine, overlooked this bit before), it is true. However a longer travel bike reduces the speed to zero across longer suspension travel, assuming a light enough spring has been chosen to make use of that travel. I hadn’t noted that assumption as I thought it was obvious that the reason to get a longer travel bike was to make use of that travel.

More mass decelerated over the same distance puts greater force through contact points – Tyres, bars, saddle, pedals – which means a harsher ride.

Does anyone want to try and argue against this directly? Rather than reason about it from completely different principles (however valid, relevant, and interesting those may be).

I don’t think the physics is that hard or in dispute here. What’s complicated is interpretation.

You make the point above that longer travel reduces the force. But that applies to riders off all weights. So should we all be on longer travel bikes?

The big problem is should the bigger rider just accept bigger forces. My conjecture is that they should and for the record I’m a tall 100kg. If I’m on a roller coaster the forces are proportional to my mass as they are in pretty all activities. But I can’t prove that this position is correct as I’ve ridden very few bikes