[retro83]

Is there any way to make an RP23 more progressive?

I've already got a low volume sleeve on it.

Alternatively, are there any providers of progressively wound coil springs for mountain bike shocks? Have searched but not much luck yet.

Background on this is that I have a frame that I am convinced has a falling rate ratio, but the manufacturer keeps telling me the opposite and I can't get the suspension working how I want it.

 

[subliminalshiver]

Don't think you're going to get any more progressive out of a coil than the RP23 you already have...
What frame are you talking about and what are you trying to accomplish?

 

[retro83]

That's what I feared.

Problem is that small/medium bumps are harsh (so traction is poor), yet when riding a whoop or landing a small drop, the shock bottoms out. Basically like the worst of riding a hardtail and riding a fully.

I think I have all eliminated the damping as a cause, by trying 3 shocks, the latest of which has been Pushed and subsequently tuned a few times by TF Tuned. It's the best it has ever been now, but it's still not right.

Maybe somebody could sanity check this for me ... does the attached pic show a falling rate frame? (i.e. does levarage ratio going up as per pic = falling rate as deeper into travel means more leverage on the shock?)

Once you get a problem in your head sometimes it's hard to think logically!

 

[tyler243]

yeah I'm pretty sure thats a falling rate. (takes less force to compress the shock at higher travel). There was a tutorial by somebody while back about how to shim an rp23. so you could search for that.

Also is the shock an aftermarket addition to the frame?

 

[PMK]

Per your own reply, this is a travel position to leverage graph.

The graph shows rising rate, the left column is increasing as wheel travel is used.

A spring alone in compression with no linkage, just compressed would be a horizontal line base from the leverage point of 1.0

A falling rate would see the plotted line head downward, but still move towards the right.

I believe I'm reading the graph correctly.

PK

 

[tyler243]

The way I look at it (which may be wrong so feel free to correct) is that if the leverage rate is increasing through travel then the force will compress the shock more per a given force as you get deeper into the travel

 

[mullen119]

PMK, Your actually reading the chart wrong. Rising and falling suspension curves are backwards from what you would think. The numbers on the left of that graph are leverage ratios. If you start with a low leverage ratio and move to a higher leverage ratio, That is actually a falling rate curve. Seems wrong, but let me explain. a 2.1 ratio means the shock will move 1mm to get the rear wheel to move 2.1mm. When the rate rises to a 2.9 ratio, the shock will move 1mm, but the rear wheel will move 2.9mm. So the higher ratio mean the shock moves the rear wheel more for any given amount of shock stroke. So when the leverage ratio rises through the shock stroke, It actually gets easier to compress the shock for a given travel amount, causing a falling rate.

I hope that makes sense :lol:

 

[derby]

...when the leverage ratio rises through the shock stroke, It actually gets easier to compress the shock for a given travel amount, causing a falling rate...

Yes, falling rate. Unfortunately there are no progressive rate coils made for mountain bikes.

Send your RP23 to PUSH. It will be transformed for you. A huge improvement.

Also you could try making an air shock shim to make the spring rate more progressive for free.
http://forums.mtbr.com/showthread.php?t=251551

 

[mullen119]

Like derby said, sending your shock to PUSH will help you get what your looking for. You could also get a Monarch from PUSH for around 100 bucks more then a getting your shock PUSHed. Darren from PUSH has said the Monarch offers advantages over the RP shocks when both are PUSHed. You could then sell your RP23 and get some money back.

 

[subliminalshiver]

The Monarch has a noticeably different spring curve than the RP23, and could make a dramatic difference for you, especially in the area of wallowy mid-stroke. I demoed one on my Ibis HD vs my stock RP23 and the difference was profound.
As above, the PUSHed Monarch is really the best suspension deal going right now.

 

[Dougal]

What is the bike? I read the graph as leverage on the shock increasing through compression, which would be a falling rate. But it's not that clear. Once we know the bike it's very easy to see if the graph fits.

 

[Vrock]

There are two ways of measuring the Leverage Ratio: Shock/Wheel and Wheel/Shock. Most of the time you find a curve just like the one you have posted (W/S), but sometimes you can find it the other way, Santa Cruz for example gives their numbers the other way. So you should't look at the direction of the graph because it can be confusing. Look at the numbers, and you would see that its a Falling Rate... and that sucks.

The graph is from a Pace, and those bikes are designed that way. Don't ask me why. I think a coil shock is going to work better than air one, even if it is more linear. You can give it a try and buy a cheap coil shock from Ebay, Chainreaction or whatever and see what happens. If you don't like sell the frame and get something nicer.

Hope that helps.

 

[derby]

What is the bike? I read the graph as leverage on the shock increasing through compression, which would be a falling rate. But it's not that clear. Once we know the bike it's very easy to see if the graph fits.

575? The travel in the graph fits. It appears to be a snip from a Linkage graph of leverage.

 

[Jayem]

Yes, falling rate. Unfortunately there are no progressive rate coils made for mountain bikes.

Well, not anymore, my stratos helix expert had a progressively wound coil spring as well as an air-spring. You could think of it as a hybrid coil/air shock , but it ended up being too progressive.

Other shocks like the dhx and older progressive suspension 5th element are able to provide "progressiveness" through their damping, which opened up a lot if flexibility for frame manufacturers, although there were still compromises with falling-rate designs.

 

[nhodge]

badly leaking fork seal

real bad. it was running out after topping out. never seen a fork leak that bad. turned out i let the oil go too long on the air side of an ' 06 Z1 Light. i was changing the spring side fairly regularly since they have a tendency to gunk up sooner, but let the air side go so long that the gritty gunk buildup @ the seal was causing the rubber to metal seal failure. :nono: wiped out all the gunk, cleaned the entire inside of the sliders w/ alcohol & everything sealed up real nice.

guess i'll change both sides @ the same time from now on.

 

[Vrock]

575? The travel in the graph fits. It appears to be a snip from a Linkage graph of leverage.

If you look at the OP Posts you can see that he got a Pace RC405 and this is how it looks like in Linkage... It's a bike that probably pedals nicely but the Leverage Ratio is crazy, 2.4-3.4 is really too much falling rate and it is going to be imposible to make it feel more plush.

 

[retro83]

If you look at the OP Posts you can see that he got a Pace RC405 and this is how it looks like in Linkage... It's a bike that probably pedals nicely but the Leverage Ratio is crazy, 2.4-3.4 is really too much falling rate and it is going to be imposible to make it feel more plush.

Yes, you're right - it's a 405. It does indeed pedal very well (better than any other full sus I've ridden). Thanks for confirming that it is a falling rate (and that it's too big to easily correct with the shock alone).

As for those suggesting Push treatment for the shock, as per the first post, the shock is already pushed and has subsequently had the shimstack adjusted by tf tuned to increase the high speed damping and reduce the low speed. This has helped but it cannot fix the problem. The only thing that can be done is to further reduce the size of the air chamber somehow - but I don't think this can be done.

As for buying a 'nicer' frame, this one retails for over £1200! :madman: It's beautifully made too, just the suspension is not working how i want it to.

I hesitate to do this, but seeing as the model of bike has already been mentioned - here is the reply from the designer after I asked if the frame was falling rate:

First to say that the 405 should be easy to set up and is not prone to bottom out with sag set correctly.

Second is to say that load-travel curve is progressive on 405- not regressive.

Standard sag confirguration should be sufficient to provide a plush ride and still have sufficient rate left to prevent bottom out.

There are no alternative linkages available for this bike.

 

[Dougal]

A new set of rocker plates and a longer shock would fix it. Either that or new rockers with the same shock but and an adapter block bolted in underneath to raise the lower mount.

 

[Vrock]

A new set of rocker plates and a longer shock would fix it. Either that or new rockers with the same shock but and an adapter block bolted in underneath to raise the lower mount.

Yep, with a longer shock a different rockers the frame would work much better, but that's not easy to do. If you have a friend with a CNC machine or something like that it can be done, but if not it's probably a lot of money.

I would sell the frame and get something else.

 

[PMK]

Yes guys I did not read the graph correct. Sorry about that.

I'm not spot on familiar with the Pace RC405.

Also, I'm not certain how these graphs were plotted. Was a system of data acquisition utilized or was it done as a cad drawing?

The reason I ask, is that in looking at photos of the bike, is has a full floater design, which will not only move the pivot angles as the suspension compresses, but also will accelerate the damper velocity.

http://www.pacecycles.com/?page_id=181

PK