[bad mechanic]

It's been a number of years, but we rode and tested a bunch of Avy stuff. It started because about 15 years ago we were using their Hi/Low compression system in our original MX tune aftermarket upgrade. Craig does a really good job with low speed flow and LS adjusters which really translates to a good rider feel. He also runs a lot more overall damping which gives good absorption...definitely a situation where stiffer equals a more compliant ride on-trail.

Could you make a Charger 2.1 feel like Craig's fork damper?

 

[PUSHIND]

You can replay the stroke depth over time on EMA, but that’s the net result of the damper, spring, trail, bike, rider input on that one trace of data logging. It doesn’t tell you how a rider may ride differently if the damper is tuned differently or spring rate is changed. Stroke depth over time is the result but not the input of the whole system.

You could design a system to function as you intended at 5m/s shaft speed, or choose not to even look at it because those events are rare. Then you don’t know what is happening when that event does happen. Are you willing to accept cavitation at such shaft speed or any shaft speed? Clearly at least one Suntour engineer thinks some cavitation is fine and offers IFP pressure as a tuning knob.

Steep trails with lots of big compressions are not demanding on damper. The worse ones on a groomed trail are just braking bumps. A relative flat long stretch full of baby heads is the place damper matters. A poor one really robs the momentum and the good one keeps you going. However, damper tuned this way will not do big jumps too well.

It sounds like you and your customers don’t really care about such trails, and Avalanche/ Shockcraft are taking care that segment or customers. Vorsprung seems not happy about the overall market trend but decided not to address it, probably due to the small size of market.

I agree, data-logging by itself, or a dyno, or rider feedback or personal experience each on their own are difficult to translate.

I'll give a real world example. I got the new Trek Fuel EXe recently. Trek supplied all of the initial data and I built up an ELEVENSIX prototype for it. I really struggled with the setup and the more I adjusted the more I was confused. So, I installed the stock shock and turns out, was much happier with the on-trail performance. Knowing that there's more performance available I set out to see what was different between the stock setup and my prototype shock. With on-board data logging you can ride both setups, overlay the data, and see where the behavior differences are allowing me to quantify what was actually happening on-trail. After that, I ran a test on the spring curves of both shocks, and finally both dampers on the dyno. The end result, I not only had a preferred setup, but I understood how it differed from the other. I had been going in the wrong direction with the ELEVENSIX to be honest. The stock shock was producing higher low-speed damping and much higher spring loads. Using the dyno I was able to revalve the ELEVENSIX and see the exact changes that were being made. The result....an ELEVENSIX spec that you wouldn't have predicted if you looked at the linkage motion rate information and shock specs. Totally unusual setup for us. But the result is an excellent performing product!

In regards to suspension velocity, our standardized tests are 0-50in/sec in 1in/sec increments for both forks and shocks as they both are subject to this range. Past that we plot with a more coarse resolution to 120in/sec(3m/sec) for rear shocks, and 250in/sec(6.25m/sec) for forks.

As for cavitation, I certainly wouldn't want that happening in any of our products. I'm not sure how it could translate into a good thing.

Yes, every suspension setup has a compromise. As a rider, you have to determine what is the best compromise for you.

I'm not sure what makes you think that our customers don't really care about such trails. We have to build suspension for riders all over the globe over all different types of terrain and riding abilities. Here in Colorado we mainly ride long stretches of rock gardens and square impacts.... it's even in our region's name....Rocky Mountains

 

[PUSHIND]

Could you make a Charger 2.1 feel like Craig's fork damper?

Not without machining parts. Rock Shox has to cast a really wide net when it comes to external adjustability as mainly an OE company. This means larger LS bleed holes, and larger range needles. As I mentioned, the Avy stuff uses finer resolution LS circuits that are designed in and are able to do so as an aftermarket company.

We have a similar issue with our ELEVENSIX rear shock in that we have to offer 2-5 different damper specifications for each bike as our LS bleeds are not capable of covering the entire spread of rider weights from 110lbs up to 275lbs. So for example an ELEVENSIX for a 165lb rider on a Santacruz Megatower will have a different damper build than a 220lb rider on the same bike, not just a different spring rate.

 

[Dano91]

He talks about it later on, so yes.

At least you now have option to change it to linear rebound tune using "piston tuning guide".. which at least in my case really helped with the rebound feel (changed from preloaded L to linear M).
From MY23 linear tunes are default in stock SD's

 

[upsha]

I'll give a real world example. I got the new Trek Fuel EXe recently. Trek supplied all of the initial data and I built up an ELEVENSIX prototype for it. I really struggled with the setup and the more I adjusted the more I was confused. So, I installed the stock shock and turns out, was much happier with the on-trail performance. ...

In regards to suspension velocity, our standardized tests are 0-50in/sec in 1in/sec increments for both forks and shocks as they both are subject to this range. Past that we plot with a more coarse resolution to 120in/sec(3m/sec) for rear shocks, and 250in/sec(6.25m/sec) for forks.

As for cavitation, I certainly wouldn't want that happening in any of our products. I'm not sure how it could translate into a good thing.

Really appreciate your real world engineering example, but wonder why you don’t test fork to higher shaft speed since some bike has LR >3 at the initial part of the stroke.

Not without machining parts. Rock Shox has to cast a really wide net when it comes to external adjustability as mainly an OE company. This means larger LS bleed holes, and larger range needles. As I mentioned, the Avy stuff uses finer resolution LS circuits that are designed in and are able to do so as an aftermarket company.

Isn’t the super wide LSC tuning range exacerbating the mid-valve cavitation potential? What I am trying to say is the mid-valve contribution to compression damping must be designed in the right proportion for the lowest base valve force expected in the design to avoid cavitation, which is with LSC/HSC wide open.

Let’s use the 25% rule-of-thumb for the BV/MV compression force ratio for a fork to avoid cavitation, and assume a 50kg rider needs 100N of total compression damping (a random number I picked). This is saying MV should provide 75N and BV should provide 25N. A 100kg rider comes in needing 200N of total damping, there is still 75N from the MV and BV needs to provide 125N now. This is 5x range of tuning for riders with 2x weight change, and I don’t know how it could be achieved without revalving.

If the company decides to design the MV for a 75kg rider with a specific BV and LSC in the middle, the riders with LSC open are running risk of cavitation (not enough pressure difference at BV at low shaft speed).

Love to know your take on this over-simplified engineering example.

PS. Reference for the 25% rule-of-thumb.

Cavitation

Controlling cavitation oil foaming in shock absorbers requires pressure balancing the shock chambers through tuning of compression adjusters and fork base valves.

restackor.com

.

 

[Curveball]

Adjusters do something...but the harder I push it, the more it pushes back, vs the stuff that I use that gets better the harder I push it.

That was how I felt about the fork on your Balance. It was almost, but not quite, harsh at slower speeds, but then worked brilliantly when being pushed hard. It was a pretty eye-opening experience.

 

[PUSHIND]

Really appreciate your real world engineering example, but wonder why you don’t test fork to higher shaft speed since some bike has LR >3 at the initial part of the stroke.



Isn’t the super wide LSC tuning range exacerbating the mid-valve cavitation potential? What I am trying to say is the mid-valve contribution to compression damping must be designed in the right proportion for the lowest base valve force expected in the design to avoid cavitation, which is with LSC/HSC wide open.

Let’s use the 25% rule-of-thumb for the BV/MV compression force ratio for a fork to avoid cavitation, and assume a 50kg rider needs 100N of total compression damping (a random number I picked). This is saying MV should provide 75N and BV should provide 25N. A 100kg rider comes in needing 200N of total damping, there is still 75N from the MV and BV needs to provide 125N now. This is 5x range of tuning for riders with 2x weight change, and I don’t know how it could be achieved without revalving.

If the company decides to design the MV for a 75kg rider with a specific BV and LSC in the middle, the riders with LSC open are running risk of cavitation (not enough pressure difference at BV at low shaft speed).

Love to know your take on this over-simplified engineering example.

PS. Reference for the 25% rule-of-thumb.

Cavitation

Controlling cavitation oil foaming in shock absorbers requires pressure balancing the shock chambers through tuning of compression adjusters and fork base valves.

restackor.com

.

I'm not sure what you're referring to when you say LR>3 in relation to fork velocities.

The link that you provided refers to a pressurized system that doesn't currently apply to mountain bike forks, but would certainly apply to rear shocks. Not sure if your intent was related to forks or shocks on that one?

In a mountain bike fork If the mid-valve generates more resistance than the base valve then you're certainly opening up the risk of cavitation as there is no pressurization. Most, if not all, production forks come from the factory with the ability to set the damper to a near full open(soft) base valve position as well. Because of this manufacturers have had to move away from any type of mid-valve force being generated and utilize check valves.

 

[Curveball]

That was how I felt about the fork on your Balance. It was almost, but not quite, harsh at slower speeds, but then worked brilliantly when being pushed hard. It was a pretty eye-opening experience.

Oh, I'll add that when I attempted to charge hard on the rental bike with the Zeb Ultimate, it was harsh to the point of almost losing control. That was a scary fork to ride.

 

[Dougal]

Fork worked well

View attachment 2055183

View attachment 2055184

26" BOS Idylle

Presuming that's the mid-valve. That's a pretty grunty spring for a bike fork damper. Did the valve have any float or preload? What did the rest of the damper look like?

BOS is an enigma in the bike world.

 

[Dougal]

It's important to note that a shim stack is also a spring, just in a different shape and form. The HC97 does use a coil spring in place of shims, and a traditional parabolic low speed needle. If we had the valve plate sealed onto the valve when it was closed then it could behave as you're describing. This would be the same as using a preloaded shim stack via a hoop ring or dished piston/valve. But, that's not how it's designed.

With HC97 we use two different materials, and two different surface finishes to keep the valve from fully sealing at static. This is also why the LS free bleed is so small...because we're getting part of the bleed from the HS valve. The system is similar to a notched shim system and creates a smooth transition through the velocity range.

We could have easily gone with a traditional shimmed design with HC97, but the shimless technology allowed more flexibility with external tuning. With the current system, we're able to create both linear and more digressive damping curves. I know the forums like to hate on preloaded/dished valves but there is a large segment of riders that really prefer that setup. Really low friction coil setups are a great example of where you might see it. But as I keep saying....suspension setup is subjective and there is no right or wrong if it's working for you. The idea that all preloaded valving is bad, or all non-preloaded shim systems are amazing simply isn't the case. So the design decision was just to give riders more flexibility with external tuning via the dials, so they'd have to spend less time tearing down the cartridge to revalve.

This design also allows the HS dial to be opened to a position where it will create nearly zero compression damping because the oil can bypass the HS valve in that position.

I will say that the one mistake that we made with HC97 was coming out of the box recommending the 5wt damper fluid. We ride pretty aggressive terrain here in Colorado and almost always have coil conversions in our forks. We underestimated the volume of riders that would buy the kit and install it in the stock air fork. In that case, the 2.5wt damper fluid performs better. Simple enough tuning change, but rides still needed to switch out the fluid. In hindsight, we should have recommended the 5wt for coil conversions and 2.5wt for air springs.

Darren

In addition to the 5wt oil you also slowed down the rebound a lot with the HC97 kits. I questioned both chioces at the time.

It doesn't. Shakler rigs and drum testers show this. If you take a fork that is producing 60lbs of compression damping and 130lbs of rebound damping at 10in/sec off of a fixed dyno and put it on a drum tester it still is producing 60lbs of compression damping and 130lbs or rebound damping when the bump creates suspension movement of 10in/sec.

The fact of the matter is that an EMA dyno can create and measure what a fork and shock are doing from a damping perspective. The companies that manufacture these test machines would have a very difficult time finding customers willing to pay $150,000 to $400,000 for them if they didn't do exactly that.

You can match individual damping points at one speed with any type of damper. Including friction. It's the curve shapes across the whole speed range that matter.

It was noted at the time that the HC97 graphs were only for a very short speed range. The speed that can be covered by the lowest power crank dyno.

I am curious, what is the max speed, that these EMA dynos can achieve? Do they cover the 100% of the speed range the forks can see on the trail?

It's been a number of years, but we rode and tested a bunch of Avy stuff. It started because about 15 years ago we were using their Hi/Low compression system in our original MX tune aftermarket upgrade. Craig does a really good job with low speed flow and LS adjusters which really translates to a good rider feel. He also runs a lot more overall damping which gives good absorption...definitely a situation where stiffer equals a more compliant ride on-trail.

A couple of years ago I tried to purchase a Dougal setup, but he refused to sell it to me. Not sure what he thought I was going to do with it as we got out of the suspension tuning game over 7 years ago. Uncover the secrets I guess! While curious, I wasn't interested enough in going the long way around to acquire one.

It's standard practice in all industries to benchmark against products in the marketplace. We sell directly to FOX, Rock Shox, EXT, Ohlins, you name it. We also purchase from the same companies.

Darren

Push: Can I copy your homework?

Me: No.

Push: Okay, but I'm going to tell the whole internet you wouldn't let me.

I agree, data-logging by itself, or a dyno, or rider feedback or personal experience each on their own are difficult to translate.

I'll give a real world example. I got the new Trek Fuel EXe recently. Trek supplied all of the initial data and I built up an ELEVENSIX prototype for it. I really struggled with the setup and the more I adjusted the more I was confused. So, I installed the stock shock and turns out, was much happier with the on-trail performance. Knowing that there's more performance available I set out to see what was different between the stock setup and my prototype shock. With on-board data logging you can ride both setups, overlay the data, and see where the behavior differences are allowing me to quantify what was actually happening on-trail. After that, I ran a test on the spring curves of both shocks, and finally both dampers on the dyno. The end result, I not only had a preferred setup, but I understood how it differed from the other. I had been going in the wrong direction with the ELEVENSIX to be honest. The stock shock was producing higher low-speed damping and much higher spring loads. Using the dyno I was able to revalve the ELEVENSIX and see the exact changes that were being made. The result....an ELEVENSIX spec that you wouldn't have predicted if you looked at the linkage motion rate information and shock specs. Totally unusual setup for us. But the result is an excellent performing product!

In regards to suspension velocity, our standardized tests are 0-50in/sec in 1in/sec increments for both forks and shocks as they both are subject to this range. Past that we plot with a more coarse resolution to 120in/sec(3m/sec) for rear shocks, and 250in/sec(6.25m/sec) for forks.

As for cavitation, I certainly wouldn't want that happening in any of our products. I'm not sure how it could translate into a good thing.

Yes, every suspension setup has a compromise. As a rider, you have to determine what is the best compromise for you.

I'm not sure what makes you think that our customers don't really care about such trails. We have to build suspension for riders all over the globe over all different types of terrain and riding abilities. Here in Colorado we mainly ride long stretches of rock gardens and square impacts.... it's even in our region's name....Rocky Mountains

😬

At least you now have option to change it to linear rebound tune using "piston tuning guide".. which at least in my case really helped with the rebound feel (changed from preloaded L to linear M).
From MY23 linear tunes are default in stock SD's

Those RS tuning guides have been a massive saviour for service work. Before then we'd get shocks in for service that someone had messed up the shim order (or the piston nut has come loose and scrambled them) and it was incredibly hard to find reliable information on the stock order. Especially for less common tunes with multiple stacks in the lockout pistons.

We had one scrambled kids shock before the guides came out and we had to find a simliar generation shock to copy the shim order.

 

[Dano91]

Those RS tuning guides have been a massive saviour for service work. Before then we'd get shocks in for service that someone had messed up the shim order (or the piston nut has come loose and scrambled them) and it was incredibly hard to find reliable information on the stock order. Especially for less common tunes with multiple stacks in the lockout pistons.

We had one scrambled kids shock before the guides came out and we had to find a simliar generation shock to copy the shim order.

That being said, for some reason, they still don't list the so-called "light" rebound check tune on SD B2.. after opening mine, I found it's neither the standard (preloaded) nor the linear one, although it's very similar to linear.. which is interesting, since in stock it was paired with preloaded rebound tune.

 

[upsha]

I'm not sure what you're referring to when you say LR>3 in relation to fork velocities.

I assume rear and front experience the same “hub speed”, but rear shock sees less speed due to leverage ratio. If you test shocks to 3m/s, why not test forks to 9m/s assuming LR=3?

The link that you provided refers to a pressurized system that doesn't currently apply to mountain bike forks, but would certainly apply to rear shocks. Not sure if your intent was related to forks or shocks on that one?

I am not following why fork is not pressurized. Spring-backed IFP like GRIP/GRIP2 have back pressure. Even bladder-based design experiences lower ramping as external pressure. That pressure balancing calculation targets putting the pressure below main piston to be the same as the top oil reservoir, and doesn’t explore the range between 1 atm to vacuum (oil experiencing cavitation). With that said, this region will likely pull the dissolved gas out of the oil, and ingress more oil/gas from the lower.

In a mountain bike fork If the mid-valve generates more resistance than the base valve then you're certainly opening up the risk of cavitation as there is no pressurization. Most, if not all, production forks come from the factory with the ability to set the damper to a near full open(soft) base valve position as well. Because of this manufacturers have had to move away from any type of mid-valve force being generated and utilize check valves.

I would hope all current fork dampers truly implemented just check valve on the main piston. Dougal has a VVC GRIP2 plot in the other thread, showing total compression damping increases by 10% with LSR from open to close, while LSC remains closed. I read it as the main piston has something more than a check shim so the LSR orifice could have such big impact.

 

[Rick Draper]

That being said, for some reason, they still don't list the so-called "light" rebound check tune on SD B2.. after opening mine, I found it's neither the standard (preloaded) nor the linear one, although it's very similar to linear.. which is interesting, since in stock it was paired with preloaded rebound tune.

Also the check tune for the vivid is identical despite saying one is for RT CXXX and one is for CXXXX

 

[PUSHIND]

😬

Yes Dougal, I am able to admit that I didn't get the tune right the first time. I even said that the stock shock was initially better...how scandalous!

Our goal is to offer upgraded performance for the rider. In order to achieve this you must be honest regarding the stock OE performance.

At $1,600 for an ELEVENSIX it better not be "pretty good", it better be "the best rear suspension you've ever ridden". That's my expectation for the customer.

 

[Rick Draper]

Interestingly Cane Creek looked into pressurising the bladder chamber on the helm. Early ones have a seal groove on the damper and an air valve port in the top cap. I know avy looked into offering this on the Charger 1 damper.

 

[PUSHIND]

I assume rear and front experience the same “hub speed”, but rear shock sees less speed due to leverage ratio. If you test shocks to 3m/s, why not test forks to 9m/s assuming LR=3?

Now I follow. It doesn't actually translate directly from front to rear as the rider has influence on the suspension once it impacts the fornt.


I am not following why fork is not pressurized. Spring-backed IFP like GRIP/GRIP2 have back pressure. Even bladder-based design experiences lower ramping as external pressure. That pressure balancing calculation targets putting the pressure below main piston to be the same as the top oil reservoir, and doesn’t explore the range between 1 atm to vacuum (oil experiencing cavitation). With that said, this region will likely pull the dissolved gas out of the oil, and ingress more oil/gas from the lower.[/QUOTE]Current systems are under extremely low pressure at top out. While they build pressure as they're compressed, you have to account for the lack of pressure at the top of the stroke.


I would hope all current fork dampers truly implemented just check valve on the main piston. Dougal has a VVC GRIP2 plot in the other thread, showing total compression damping increases by 10% with LSR from open to close, while LSC remains closed. I read it as the main piston has something more than a check shim so the LSR orifice could have such big impact.
[/QUOTE]10% at what velocity?

 

[Dougal]

Interestingly Cane Creek looked into pressurising the bladder chamber on the helm. Early ones have a seal groove on the damper and an air valve port in the top cap. I know avy looked into offering this on the Charger 1 damper.

SPV showed me that even a small amount of air preload in a fork damper feels awful. Your fork spends a lot of time topped out when it shouldn't be. Especially climbing.

 

[angieri918]

Oh, I'll add that when I attempted to charge hard on the rental bike with the Zeb Ultimate, it was harsh to the point of almost losing control. That was a scary fork to ride.

i had exact same experience running the 2.1 and ch3 Zeb Ultimates. Exactly what @Jayem was saying, The times where I really noticed the excessive harshness of those forks were when I was charging into a rough/blown/braking bump steep sections right before a corner. The front end felt sketchy aF And these were on the front of a Lithium and Balance with 170mm travel. Switching back to my HTV2 with a 160 EXT ERA and the harshness was pretty much non existent. Maybe it still had some but switching right back to my fork from the Zebs it was very evident. I would sure like to know what the difference is in EXT’s damper that allows it to ride more composed compared to Charger damper.

 

[PUSHIND]

For giggles I ran down to the dyno room and ran the following. Brand new Charger 2.1 right out of a sealed box. The test below is

1m/sec Compression, 1m/sec Rebound
2m/sec Compression, 1m/sec Rebound
4m/sec Compression, 1m/sec Rebound

The results are below the video.
Green is fully open compression and rebound
Red is fully open compression and fully closed rebound

There are no spikes or odd restrictions. In fact, you'll see that with the rebound fully open the damper produces 25lbs of compression, and with it fully closed just 29lbs at peak velocity. Clearly the mid valve has plenty of flow and is behaving as a check at high velocities.

 

[Dougal]

For giggles I ran down to the dyno room and ran the following. Brand new Charger 2.1 right out of a sealed box. The test below is

1m/sec Compression, 1m/sec Rebound
2m/sec Compression, 1m/sec Rebound
4m/sec Compression, 1m/sec Rebound

The results are below the video.
Green is fully open compression and rebound
Red is fully open compression and fully closed rebound

There are no spikes or odd restrictions. In fact, you'll see that with the rebound fully open the damper produces 25lbs of compression, and with it fully closed just 29lbs at peak velocity. Clearly the mid valve has plenty of flow and is behaving as a check at high velocities.





View attachment 2055307

If you think that's fine, then just go ahead and design your fork the same.