This reminds me of a weird dream I had many years ago. I was riding my mtb and was amazing how smooth the fork felt. I looked down and saw I had a basket mounted in front of the bars and it had a pile of phone books in it. I haven't yet tried this in real life. Are phone books even a thing anymore?

There are some vids somewhere of guys experimenting with adding weight to their DH bikes. I don't recall the details or outcome.

 

A lot of dh racers experiment with adding sprung weight to their bikes to change the center of gravity. Reducing unsprung weight reduces the inertia that the suspension needs to overcome in order to react to input. Ask any racecar engineer if they would like less unsprung mass vs sprung mass and you'll get 100% agreement that less unsprung mass is desirable.

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Air springs are inherently linear in the mid-stroke, combined with methods to overcome initial stiction and most factory damping that is overly-restrictive to prevent fatties from blowing it, it results in having to run very little low-speed compression and lots of blowing through travel, exacerbated by the mid-stroke of the air spring. While they can work acceptably, they will never be linear through most of the travel with a ramp-up at the end. Running too progressive sinks you through the travel and creates deep-stroke harshness, also not a great way to run suspension. I wouldn't pay attention to that person at all.

 

It does seem like coil forks are mainly used by consumers and not professionals.

There's no question reducing unsprung mass and increasing sprung mass would help smooth out the ride. However, we're riding bicycles so the amount of mass needed to really see a significant effect would be overall detrimental to performance. It's not like you're going to add a couple pounds to your bike and make it feel like a motocross bike. Which is why DH racers generally worry more about saving weight than adding it, and why their bikes weigh only a few lbs more than enduro bikes.

Although it does increase unsprung mass, heavier tires and inserts do add a lot of damping. However, I do wonder how many people are after a more plush ride for performance reasons or for comfort. I was having a conversation with someone about Cushcore recently and they were going on about how great the ride quality is improved and they always run Cushcore Pro, even on tamer XC trails. Personally, I don't need a more plush ride on most trails and 260g per wheel is not worth it.

 

Subscribed.

It does seem like coil forks are mainly used by consumers and not professionals.

This has no bearing on what's right, wrong, good, or bad.

People need to stop thinking they should set up their bikes like "professionals", or that it's some kind of great benchmark. Paid athletes (racers) riding what they're told to ride, and the bikes are setup for doing a very specific job.

 

That's an interesting point.

I normally aim for suspension to be smooth, performance tends to follow.

A quick Google suggests a cruiser has a sprung/unsprung ~17/1
Motorcross 8/1
My bike is about 4/1

Surely the ratio is even more important if its that close?

 

That's an interesting point.

I normally aim for suspension to be smooth, performance tends to follow.

A quick Google suggests a cruiser has a sprung/unsprung ~17/1
Motorcross 8/1
My bike is about 4/1

Surely the ratio is even more important if its that close?

4:1 seems awfully high for a bike. Just doing a rough estimate off the top of my head it seems like an enduro bike would be less than 1.5:1. Did you include your fork lowers and ~1/2 the weight of your rear triangle in the unsprung weight category? Even if I keep it simple and count the entire fork and frame as sprung weight, it still seems like it would be maybe 2:1 at most. Is your bike an e-bike or gearbox bike or something?

 

The problem is only in the expectations.
85-90% of the sprung mass is loaded on the rider's arms and legs, no suspension will ever change that. Expectations that a suspension shoud give a magic carpet ride will only lead to messed up setups.

Unsprung mass should ideally be as low as possible, but strenght and damping are also necessary... so sometimes you need to give up the noodly rims and bouncy tyres. It's a matter of finding the best compromise here.

Coils may be more comfortable, if that matters, but modern triple chambe air springs (dual positive, like manitou's) can achieve any curve you may need.

 

The three chamber air spring curve is spot on. I've tuned mine to match the push smashpot.
However it is not as smooth as my old '03 coil dorado.

I'm not sure if it due to coil friction or the dynamic change of spring rate when air compresses... Or something else.

The coil on the back of my bike transmits no detectable spikes or vibration. My old Dorado would feel the same (when weight was far back), new dorado air... Not the same.

Not sure how we went from a sprung/unsprung chat to coil/air though... Different topics.

Anyone got any thoughts on the stored energy in a wheel affecting suspension?

 

Interesting points, he's talking about sprung & unsprung mass as different things but then seems to think adding weight has a similar effect regardless which one you add to?

Sprung vs unsprung weight is the key for sure, increasing sprung weight is almost entirely a positive thing because it makes the suspension work better and reduces vibration transmitted to the rider. Yes the rider is the bulk of the mass but certain vibrations will still be detrimental so reducing them can only be a good thing. Except for the case of very light riders the trade off for increased sprung weight is basically negligible, eg ie adding a kilo or so of weight with coil springs and a dropper post will make the ride far better in one way but the negative influence of weight will be imperceptible.

Unsprung weight however should be ideally as low as possible but that where you do need to compromise. Strong, wide rims, DH tyres and inserts all have benefits but the extra weight reduces the ability of the wheel to respond to bumps quickly so you do need to carefully pick which ones you need so you aren't adding too much unsprung weight.

Talk to any car or motorcycle designer and they will all agree that unsprung weight is the one thing that they would always reduce as much as possible given the chance

Anyone got any thoughts on the stored energy in a wheel affecting suspension?

Are you talking about the kinetic energy of the wheel in motion or the potetntial energy in the elastic parts eg rim, tyre, spokes?

 

What’s a push snashpot? Last I checked it’s a Push ACS-3 or a Vorsprung smashpot


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Good spot, you can guess I was half asleep when I wrote this.
Push acs-3 is what I meant.

 

From my understanding, for the most effective suspension, you want the heaviest frame and lightest wheels going. You want the frame to functionally stay still while the wheel moves over the obstacle.

I accomplished this once (by accident) while running my suspension at 40% sag. It was interesting, but the ground kept getting in the way of my pedals...

 

What model is yours again? The frames of his ive worked on were incredibly progressive which takes careful tuning for sure

 

Evolink 158 Xl.

Any applicable advice?

 

Anyone experienced want to comment

There's a lot to unpack here.

1) Coils more likely to have harsh bottom-outs - probably not. Maybe a poorly-designed one. Both the Vorsprung Smashpot and PUSH ACS-3 have anti-bottom systems (supplementary air spring or hydraulic damper) that work. And there's many options for coil spring rear shocks. You're only likely to have an issue if your shock can't be set up for your bike, such as an unsuitable leverage ratio.

2) Pros don't run coils - no. It seems to be a mix in the EWS (Pinkbike, VitalMTB). I haven't done a survey. The video of Curtis Keene testing a coil shock a couple years ago is what got me to try a coil on my Nomad (v3) and I still ride coil on my Nomad (v4). My other bike (5010 v2) is still on air.

3) You won't know if you don't try - go for it - YES. What works for someone else may not work for you. This includes the pros, by the way. Jordi Cortes comments in one of the Fox Dialed videos (I can't find which one specifically but it was from this season) about how even a pro "only" going at 90% of race pace isn't going to be happy with a setup for full race pace.

4) Tires (and inserts) are essential - YES. I can feel a difference just from knob thickness between a fresh set of tires and my old set (same make/model/pressure), let alone changing make/model/pressure or casing or inserts.

5) Chain/deraileur example - meh? I'm not sure what to make of this. I just think of Gwin's chainless run and how well his suspension responded without it... but to me that was more about direct interaction between the suspension and the drivetrain through the tension in the chain between the rear cog and front ring.

6) Setup matters - YES. Nothing more to say about this.

7) More unsprung mass is better - No. I'm not sure any of the posters here think it's true. We want our wheels to track the ground (item 4 on the list from Vorsprung when thinking about "correct setup"). I'm also not sure the original comments in the original post address unsprung mass in a meaningful way. It seems to ramble around many of the previous points instead.

¯\_(ツ)_/¯

 

There's a lot to unpack here.

1) Coils more likely to have harsh bottom-outs - probably not. Maybe a poorly-designed one. Both the Vorsprung Smashpot and PUSH ACS-3 have anti-bottom systems (supplementary air spring or hydraulic damper) that work. And there's many options for coil spring rear shocks. You're only likely to have an issue if your shock can't be set up for your bike, such as an unsuitable leverage ratio.

2) Pros don't run coils - no. It seems to be a mix in the EWS (Pinkbike, VitalMTB). I haven't done a survey. The video of Curtis Keene testing a coil shock a couple years ago is what got me to try a coil on my Nomad (v3) and I still ride coil on my Nomad (v4). My other bike (5010 v2) is still on air.

3) You won't know if you don't try - go for it - YES. What works for someone else may not work for you. This includes the pros, by the way. Jordi Cortes comments in one of the Fox Dialed videos (I can't find which one specifically but it was from this season) about how even a pro "only" going at 90% of race pace isn't going to be happy with a setup for full race pace.

4) Tires (and inserts) are essential - YES. I can feel a difference just from knob thickness between a fresh set of tires and my old set (same make/model/pressure), let alone changing make/model/pressure or casing or inserts.

5) Chain/deraileur example - meh? I'm not sure what to make of this. I just think of Gwin's chainless run and how well his suspension responded without it... but to me that was more about direct interaction between the suspension and the drivetrain through the tension in the chain between the rear cog and front ring.

6) Setup matters - YES. Nothing more to say about this.

7) More unsprung mass is better - No. I'm not sure any of the posters here think it's true. We want our wheels to track the ground (item 4 on the list from Vorsprung when thinking about "correct setup"). I'm also not sure the original comments in the original post address unsprung mass in a meaningful way. It seems to ramble around many of the previous points instead.

¯\_(ツ)_/¯

My interpretation of Leo's quote in the OP is that point number 4 here is more important than point number 7. I don't think he was actually advocating increasing unsprung mass just for the sake of increasing unsprung mass but rather not compromising tire, rim, and insert selections in an effort to minimize unsprung mass. I'm with you on points 1 and 2, though.

 

Why do you want less UNSPRUNG weight?
- It takes less energy to move it. Properties of mass with inertia. More mass=more inertia=more energy needed to initiate movement. In the suspension world, if you need to have more energy to move your unsprung weight, the suspension spring is not absorbing the impact. Instead, the energy is being transfered into the material, and then through to you the rider.

Why is having LESS SPRUNG weight a good thing?

- Suspension is ususally rated in kg/mm. Meaning, for every millimeter of travel, it takes XX amount of KG of force to move. When you have more weight holding the suspension down, you "preload it" with your sag. So, if the suspension is sagging 10mm, and you have a spring (air or coil, it doesn't matter) of 5.0kg/mm, you have 50kg of force pushing down on the suspension at that moment, even just sitting there. Now, it only takes another 5kg of force to move the suspension 1mm, but, the total amout of energy stored in the suspension is still greater. In the case of air suspension, that kg/mm number will ALWAYS be a constantly increasing number. (Since air is ALWAYS progressive) As that number goes up, the suspension spring will become stiffer.

When you have a lot of mass to the sprung weight, you are increasing the inertia of that object, so it is much less affected by the energy being imparted on the suspension, but thats about it. You still have all of the drawbacks of more mass. (greater suspension stiffness being needed, less maneuverability, and such and so forth.)

 

In the case of air suspension, that kg/mm number will ALWAYS be a constantly increasing number. (Since air is ALWAYS progressive) As that number goes up, the suspension spring will become stiffer.

Erm....depending on the size of the negative chamber an air spring typically DECREASES in rate for the first ~25%, is linear for a short while and then becomes progressive

Re: sprung mass, it takes a pretty huge increase to become a hinderance. You may feel (or think you feel) a difference but it probably isn't measurably worse. The increased stability and reduced harshness tends to outweigh any perceived disadvantages

ie you can literally just add weight to a frame in strategic places and it will improve how the bike rides all on it's own

You would never see it admitted publicly but it is not uncommon for race teams to add weight inside the frames if a bike is too light

I encourage people to go get some 1 pound weights and experiment with attaching them to the frame, then attaching them to the swingarm or forkleg to see how it feels

 

The entire context of this preload/spring rate conversation is the use of negative springs.
Negative springs are important for air sprung suspension because there is significant energy stored at top out. That is equivalent to winding on a lot of preload on a coil spring even though you're not compressing the air spring. The force generated by the negative spring can balance this preload so you don't need such a large increase in force to initiate movement. Actual spring rate is irrelevant.

 

So much spring confusion above, seems to be more an argument on terminology than engineering though. If I get involved I'd probably make it worse not better


This might be interesting for some.
You can make a spring very linear as long as you have a 3 chamber and large neg.

Typically I can't upload photos from my phone!

 

Nicely tuned dorado (compared to a coil)

 

Rockshox air spring

 

Hi,

Just got this opinion from the designer at Pole.

Anyone experienced want to comment, seems false to me, hence my checking?

"Personally, I don't see any reasonable point on the coil in forks. The air spring offers a nice ramp up and you can get the spring rate spot on. With coil, you are most likely to have more harsh bottom outs than on air-sprung. There is no fork or shock that will give you the plushest ride ever (similar to moto) because there is no mass on the bike itself that will load the suspension. The SAG is made only by the rider. The only way to make the bike less harsh is to use heavier stuff (tires, wheels, etc.). This is one reason why all Pro's run air springs and DH tires at EWS.
But... you won't know if you don't try it. I say go for it That's how I learn stuff as well.

ires (and inserts)are an essential part of the suspension as they damp the ride in the first part of the stroke. The excessive talk about unsprung mass -talk has gone too far and it is actually working counter benefits of the riders. Strong wheels, thick sidewalls, and inserts will make your ride immediately better.
The "unsprung mass" that you don't feel when you take off the chain and derailleur is actually the lack of movement of the chain and the derailleur that is slapping around. The chain is heavy and the movement of it with the derailleur is causing the feeling of "massive unsprung mass".
I have ridden light and heavy bikes and the unsprung mass is not the problem. The biggest problem in most cases is too nimble products and a lack of understanding of how suspension works. The bikes that have the most horrible suspension setups have too low tire pressure with light tires, suspension setup way out of the factory standards, light wheels, weird cockpit setup that puts your weight off the ideal, and imbalance of the rear and front springs.

From my understanding, for the most effective suspension, you want the heaviest frame and lightest wheels going. You want the frame to functionally stay still while the wheel moves over the obstacle.

Obviously there are other benefits that increase weight, but it's not the increase of weight you want. I run DHR tyres for a ton of benefits, but if they could be magically half the weight it'd be better for suspension?

Yeah that's weird.

Your bike suspension has two frequencies:
The slow frequency is the rider and bike chassis bouncing up and down on the suspension.
The fast frequency is the wheels and unsprung mass moving up and down against the ground.

The bigger the difference in the two masses (sprung vs unsprung) the bigger the difference in these frequencies and the better your suspension can handle fast rough ground.

But. On bikes our sprung mass isn't uniform like a car is. It's a light bike and then another set of four springs and dampers (arms and legs) connecting the rest of the sprung mass.

This is the bit that throws up massive differences between our suspension tunes and cars and motorbikes. It's why a lot of suspension tuners using car or motorbike theory produce some absolutely awful results.

The only performance downside to coil springs is weight and getting the correct weight. Harsh bottom-out isn't an issue. We have correctly tuned dampers and bumpers for that. Not to mention hydraulic bottom-out.

 

Your bike suspension has two frequencies:
The slow frequency is the rider and bike chassis bouncing up and down on the suspension.
The fast frequency is the wheels and unsprung mass moving up and down against the ground.

The bigger the difference in the two masses (sprung vs unsprung) the bigger the difference in these frequencies and the better your suspension can handle fast rough ground.

But. On bikes our sprung mass isn't uniform like a car is. It's a light bike and then another set of four springs and dampers (arms and legs) connecting the rest of the sprung mass.

This is the bit that throws up massive differences between our suspension tunes and cars and motorbikes. It's why a lot of suspension tuners using car or motorbike theory produce some absolutely awful results.

The only performance downside to coil springs is weight and getting the correct weight. Harsh bottom-out isn't an issue. We have correctly tuned dampers and bumpers for that. Not to mention hydraulic bottom-out.

Couldn't agree more!

 

I'll throw a hand grenade in the room.

I ride ebikes too nowdays, I get to try a lot of others bikes and even my own bike (merida e160) has the best suspension on any bike I've ever ridden shy of my Devinci wilson. In fact basically any ebike I've ridden has had superior suspspension manners than any enduro bike I've owned. It's fascinating and frustrating at the same time. These bikes are no joke on the downhills.

 

The one with X2 on the back and FIT4 in the fork?

Can I ask what other suspension you've ridden?

 

Yes the increased weight of 29" wheels is a negative, but the larger radius makes the acceleration and peak speed (or frequency) of the wheel travelling over the bump lower so the effects kinda cancel out to a degree.

Another thing to consider is a wheel travelling at a higher speed has more energy than a wheel that weighs more by the same percentage. Therefore reducing the speed of the wheel will make it track the ground better than reducing the weight

 

Okay, sorry for waking up a napping thread but I have a question for the knowledgeable in this thread. In another forum for Starling Cycles owners one poster posted a pic of his Swoop with his Ohlins coil shock oriented in "reverse" (the reservoir was mounted to the swingarm as opposed to the main triangle) to make room for a water bottle in the front triangle. Lots of Starling owners of medium sized frames will do this. Another poster responded and said that people shouldn't do that because it increases the unsprung weight. My first thought was, It can't be by THAT much, can it? I mean, would this impact the rear suspension enough to be noticeable? It's not that much weight, right?

Thoughts?

 

IMO it is not noticeable. You also have to consider leverage rate, so effective weight added has to be divided by 2,5-3, to evaluate the effect.
Majority of the bikes that have the shock in vertical orientation, also have the reservioar at the "moving point".

 

The 50g piggyback has its mass acting about 2.5x less on the suspension than the 1kg tire due to leverage rate.
Shock unsprung weight is pseudoscience. The whole unsprung mass idea is already full of BS.