aktiv Suspension

[driftking]

The original article is on pinkbike here.
http://www.pinkbike.com/news/trek-fox-penske-reaktiv-suspension-press-release.html

I think its interesting, They are using a regressive curve.
Personally I think its very early to pass judgement on the shock, I do however think its a interesting point of discussion.
They claim that the new design has no draw backs in that previous designed tended to have the draw back of increasing LSC for pedal efficiency made the bike track quite poorly.

Personally I see this quite odd given their new curve has a very steep initial curve that than regresses.
I think this probably works in that the LSC initially starts lower still so it provides a good traction although it ramps up much faster and steeper to the sag point, this gives you that high dampened pedaling efficiency, than it regresses back down to provide a supple feeling for bumps after sag point.

Although during that initial ramp up the traction is still going to be effected i wonder by how much.

A curve that peaks around sag point is a great idea, At first I thought this new design was a bit of marketing than I actually though myself why don't we have a curve that peaks at sag than regresses, Realizing this is exactly what this design does I suddenly understood this shock as more than just marketing. It gives you a high supported pedal platform with a softer regressive curve after for bumps, as it extends from sag point the curve than lowers back down to a softer point.

I like it, I would like to see where it goes.

 

[Ivan]

Sag point is immaterial.

This is a damping curve. The X axis is shaft speed. The proof will be in the riding.



And a propedal curve for comparison

 

[driftking]

Sag point is immaterial.

This is a damping curve. The X axis is shaft speed. The proof will be in the riding.

I was trying to find that cheers.

So given my understanding of the ramp to to sag is wrong. 2 questions.

1.What is wrong or right with my idea and would it be right to assume that my example of a shock that ramps up than regresses from sag may be ideal?

2.How does this shock work than, how are they claiming it has no drawbacks?

As detailed as you can or feel bothered to go into for both would be great, I am always open to learn lots about suspension I love it.

 

[Psyloman]

http://p.vitalmtb.com/photos/storie...14_06_11_at_10.37.26_AM_210414.jpg?1402508757

Here is the chart for the normal ctd shock. Looks like aktiv is similar to riding in climb mode. Doesn't sound overly fun to me but I'd still be interested to try it and see what it's like in real life.

 

[Ivan]

Forget about sag, you may be confusing these curves with leverage curves for frames.

This is all about compression damping force (in the case of Aktiv as they have said it only affects the compression circuit).

As you can see from the supplied curve, when comparing the Akitv curve to other types of dampers, at low to medium shock velocities the compression damping force is higher, whilst retaining similar damping at higher velocities. Their is also a sharp drop in damping force in the curve.

If you believe the marketing, this means you could have a lot more LSC for low speed suspension movements (weight shifting, pedalling, braking) than other dampers with similar performance at high speeds (bumps). The sharp drop in curve is also of benefit if it is positioned at the perfect velocity point that is the difference between the previously mentioned movements.

i have never seen shock speed data for an actual bike, so I don't know how viable it is to easily separate those movement types. I imagine it is not as easy as it seems.

 

[driftking]

Forget about sag, you may be confusing these curves with leverage curves for frames.

This is all about compression damping force (in the case of Aktiv as they have said it only affects the compression circuit).

As you can see from the supplied curve, when comparing the Akitv curve to other types of dampers, at low to medium shock velocities the compression damping force is higher, whilst retaining similar damping at higher velocities. Their is also a sharp drop in damping force in the curve.

If you believe the marketing, this means you could have a lot more LSC for low speed suspension movements (weight shifting, pedalling, braking) than other dampers with similar performance at high speeds (bumps). The sharp drop in curve is also of benefit if it is positioned at the perfect velocity point that is the difference between the previously mentioned movements.

i have never seen shock speed data for an actual bike, so I don't know how viable it is to easily separate those movement types. I imagine it is not as easy as it seems.

yeah my initial thought was in regards to leverage curve in which case why not run a cruve that progresses to the sag point then regresses as I originally thought?

As for this though why are we using LSC to control HSC bumps. Is it because generally the higher the LSC is adjusted the later the HSC comes into play or the higher the threshold is for HSC, SO by regressing the dampening like this it allows riders to have the LSC set up stiff but without these down falls of the LSC ending stoke and the cross over effect on High speed compression.

If this is true than I can only assume its claim of "pedal efficiency without the loss of traction" is pure marketing, well less marketing but more missdeicted as most are assuming a beginning stroke improvement not mid stroke.. While this has a benefit the benefit is mostly seen at the cross over between LSC and HSC and therefore initial traction and importantly the one that mostly effects pedaling efficiency will still be greatly compromised by higher LSC. This is more improving the mid stroke and beginning of High speed traction.

The question than is asked. If true, will initial traction be compromised by having a heavier dampening curve or it will be no different than now as riders will come to a point where pedal efficiency is the same but the initial traction will still be unaffected just their mid stroke will be much improved.

 

[creaky]

I'm confused. I think I'd just have to ride it to find out. Not expecting mind blowing change from a typical LSC adjustment to be honest.

 

[g-fish]

View attachment 292525

Correct me if I'm wrong, but won't this give it a wallow/bottom out on bigger hits? The damping doesn't ramp up on big hits meaning it will just push straight through the travel rather than ramping up.

Or does the ABP suspension path compensate for this separate to the shock?

 

[driftking]

Correct me if I'm wrong, but won't this give it a wallow/bottom out on bigger hits? The damping doesn't ramp up on big hits meaning it will just push straight through the travel rather than ramping up.

Or does the ABP suspension path compensate for this separate to the shock?

My concern is here in the green.


While it regresses the increase dampening force appears higher than that of a shimmed damper so that brings up the question, is this going to actually improve traction over the conventional damper or not. As ivan said (please correct me if this is not the point you were referring to) if the damper hits the mid and HSC cross over point at point X than yes this should actually be a good move, however if it hits this earlier it will actually lower traction from my understanding as the shimmed damper has lower dampening force prior to this point.

As for the wallowing bottom out it still ramps up as you can see but it is much more linear dampening which arguably is a good thing, you would expect that the bike has external adjustment to help the ramp up.

the question than still remain the intial traction though during the LSC area is still providing much higher dampening forces and therefore will provide less traction initially?
This seems like a solution to providing more LSC while maintaining mid stroke and ending stroke bump compliance but does nothing for initial traction.?

Ivan pull this post apart if need be to school me.

 

[g-fish]

My concern is here in the green.
View attachment 292532

While it regresses the increase dampening force appears higher than that of a shimmed damper so that brings up the question, is this going to actually improve traction over the conventional damper or not. As ivan said (please correct me if this is not the point you were referring to) if the damper hits the mid and HSC cross over point at point X than yes this should actually be a good move, however if it hits this earlier it will actually lower traction from my understanding as the shimmed damper has lower dampening force prior to this point.

As for the wallowing bottom out it still ramps up as you can see but it is much more linear dampening which arguably is a good thing, you would expect that the bike has external adjustment to help the ramp up.

Totally agree with the first point, it looks extremely over damped. We'll see how adjustable it is.. And as far as I understand this graph only shows the shock characteristics rather than suspension leverage.. I've never ridden an abp trek, but if they have a lot of wheel travel in their initial stroke it'll probably combine well with the shock.

I was more referring to the fact the leverage curve slopes downwards/plateaus from the green point you have outlined creating the liner feel. Maybe it's just my riding style, but every bike I've owned with a linear mid-end stroke (linkage driven single pivot, maestro and DW link) has sucked because it gets stuck in its travel after consecutive bumps, eventually leading to bottom out. I've got a DW split pivot bike now, it has heaps of anti-squat initially and a decent support as you get deeper into the travel.. Can't fault it.

 

[driftking]

Totally agree with the first point, it looks extremely over damped. We'll see how adjustable it is.. And as far as I understand this graph only shows the shock characteristics rather than suspension leverage.. I've never ridden an abp trek, but if they have a lot of wheel travel in their initial stroke it'll probably combine well with the shock.

I was more referring to the fact the leverage curve slopes downwards/plateaus from the green point you have outlined creating the liner feel. Maybe it's just my riding style, but every bike I've owned with a linear mid-end stroke (linkage driven single pivot, maestro and DW link) has sucked because it gets stuck in its travel after consecutive bumps, eventually leading to bottom out. I've got a DW split pivot bike now, it has heaps of anti-squat initially and a decent support as you get deeper into the travel.. Can't fault it.

yeah I see your point but even though it is been regressive its dampening force is still higher than that of a traditional shimmed shock so it shouldn't bog down it should remain quite supported, up to the point where the lines cross, from there the aktiv will be more linear and less progressive. It will no doubt feel like its not ramping up but thats exactly how you want it because the initial starting point is already so much higher the initial will feel stiffer so you will want it to smooth out by been regressive. If it was progressive you would just have a extremely hard shock that would be too stiff in the mid stroke to high speed compressions.
Essentially what this is trying to achieve is the feeling of running high LSC initially but without the draw back of the harshness and lack of suppleness initially after the LSC.

It should be fine up to the cross over point where it begins to be more linear than progressive.

unless of course I am missing something here.
Ultimately while its not the suspension curve low velocity equates to LSC and HSC and those can be related to shaft position. So you would hope that the shock is only LSC up till the cross over point. This brings up the issue though as before very stiff LSC dampening.

 

[Wombatone]

First there is RP than came CTD and now Active, what is next at Fox?
They might surprise us one day and make a rear shock that works?

Let me know if this is the one - until then I will stick with Cane Creek.

 

[Jaredp]

Gotta say I am a little bit the same.

I will stick with cane creek until ohlins releases something.

The future of shocks has to be the electronic shifting shock. Even if it is a handle bar mounted remote that activates a preset set of user parameters. Nothing the video really addresses the hardest issue in MTB... Building a shock you don't have to fiddle with.

A nice evolution of a rear shock would be the specialized auto sag feature with the rockshox ei shock on the Lappierre...

Set the air and rebound. Ride.

The most interesting component evolution in years has been the XTR Di2. Can't wait for that to be XT.

 

[Alo661]

Ridden DRCV, don't like it (currently riding a 2014 Remedy with DRCV), feels harsh and active when you don't need it, shoots through it's travel when you do. I do know of the spacers for the air-can, but why use spacers, when a shock should be tune-able externally, like the CC. Much prefer a normal air shock (ran a vivid air on my old 2012 remedy).

Always will prefer Rock Shox over fox (Old Pike 454 > Fox 831 anyday!). Having sold my 2012 Remedy, I miss the plush feel of the Pike/Vivid combo, against the Fox 34/DRCV rear on my 2014. Never used the 3 position lever on my pike, but on the CTD and DRCV, I have to switch between trail and decent, never can find a happy medium.

aktiv seems like nothing more than marketing spin. Similar to DRCV when it was released (http://www.pinkbike.com/news/fox-drcv-shock-test-2010.html), anyone notice that in 2014, Trek don't use DRCV in any of their front forks? I did. I wish DRCV would be ditched from Trek's range completely.

Next bike will be a Norco Range (fingers cross they arrive on time in August....), Pike/Monarch combo. I like the Trek geo, feels great, but the shocks just let it down. Can only hope that aktiv completely replaces their DRCV system (it is pretty old as well, http://reviews.mtbr.com/gary-fisher-roscoe-pro-review/5), but I'm doubtful.

 

[Ivan]

For driftking http://www.theoryinpracticeengineering.com/tech/shocks.pdf

G-Fish:

I don't know why they chose to spec maestro bikes with high volume air cans, but IMO it was a mistake. The linear leverage ratio at the end of the travel benefits from a more progressive, lower volume air spring. A medium air volume spacer in my RP23 HV on my TranceX made a massive difference to both initial suppleness and ramp up at the end of travel.

 

[Klips]

For those of us who would love to learn more but don't know where to start, does anyone have a good resource for beginners on the effects of shock curves etc? I can understand a bit of this but a lot is going over my head, particularly in the paper Ivan linked.

 

[Ivan]

For those of us who would love to learn more but don't know where to start, does anyone have a good resource for beginners on the effects of shock curves etc? I can understand a bit of this but a lot is going over my head, particularly in the paper Ivan linked.

this is not a bad intro to all things MTB suspension
http://cdn.sram.com/cdn/farfuture/1...ocs/rockshox_suspension_theory_10-replica.pdf

 

[g-fish]

For driftking http://www.theoryinpracticeengineering.com/tech/shocks.pdf

G-Fish:

I don't know why they chose to spec maestro bikes with high volume air cans, but IMO it was a mistake. The linear leverage ratio at the end of the travel benefits from a more progressive, lower volume air spring. A medium air volume spacer in my RP23 HV on my TranceX made a massive difference to both initial suppleness and ramp up at the end of travel.

I also changed the air volume spacers in my trance, but this leads to a harsh progression and technically more chance of overheating on repeated cycles (not that I felt this).. I guess I'm impossible to please. A HV air can with a progressive leverage is the only way to go IMO.

 

[g-fish]

Trek has also introduced a new hub standard with these bikes:
http://www.bikeradar.com/mtb/news/article/trek-and-sram-roll-out-wider-axle-standard-41352/

148x12mm, with the extra width coming within the hub shell.. meaning current hubs won't be adaptable. Hopefully this one doesn't stick.

It must be asked, is there much point in developing proprietry suspension, hub, wheel and stem standards which may net better performance but make upgrading, servicing and finding spares significantly harder? The gains from this hub standard are tiny, and the shock is probably only a minor gain - at best - over current platform shocks/suspension designs.

 

[Wiffle]

Whilst we're commenting on suspension, can we please use the correct term "damping"; dampening means making something wet, and that's not what's happening here.

Remember LSC/HSC refer to damper shaft speeds, not bike speed; pedalling/braking/body shifts are the primary LSC events, whilst bumps generally (even smallish ones) are a HSC event. I suspect that what this damper is attempting to do is create a shock which doesn't need a lot of tinkering; in theory it'll work well to stop LS events compressing the shock, whilst opening up quickly and easily for impacts of all sizes. How effective it is will probably come down to a couple of factors, primarily how well they've matched the "blow off" shaft speed to trail impacts, and secondly how quickly and smoothly the LSC circuit opens up upon impact. I think without riding it the best we can say is it has theoretical potential, but how well that theory is applied will determine it's effectiveness.

RE End stroke support; bottom out resistance is controlled by a combination of factors, one of which is HSC damping, and the other is spring progressiveness. The RE:Aktiv damper is slightly progressive after the LSC fall-away, so if it's matched to the correct sized air can it could still provide plenty of big-hit support; again it comes down to matching the spring and damper curves to each other. Bear in mind also that riders of different weights, and hence air pressures, will have differing experiences with this shock, and some time experimenting with spring spacers (and even possibly a custom oil/shim tune) will be the secret to getting the best out of it.

As I understand it, the graph shows three completely different dampers, so there's no "crossover" point between the different curves. The "crossover" is the transition from LSC to HSC at the peak of the curve ie: where the LSC damper effectively switches off.

Like I said I think it's got potential, but needs to be ridden to see if it's well executed.