Shock Revalving
 

As promised here is some information on the updates to valving from JRZ for those of you that have expressed interest. The nice thing about JRZ is most stuff is interchangeable and compatible with each other. For example if you have two ways you can upgrade to three ways by just replacing the valve head on the canister. while there are differences in the piston inside the shock housing over the years the basic principle fluid dynamics, and operation stays the same and will work with converting 2 ways to three ways or just updating your older three ways to the new style....

1. The 1231 (new style) is both softer and stiffer than the old style. (by 30%) each way.
2. There is a finer range of adjustment as the 1231's have 12 Low speed and 20 high speed adjustments..... double the old style so the range is a lot finer.... (say you think on the old 3 is too little and four is too much thats all sorted out now with the fine range)
3. The velocity remains the same as the old style but offers the finer range of adjustment.
4. The 1231 separates the chambers for low and high speed. This allows finer tolerances in machining so there is a smoother buildup of pressure. Having them in separate chambers also allows us to match them better side to side.

There is so much more to this (updated shafts, guides etc) but to get it started thats the cliff notes! I have attached some pictures from the dyno and also the valving..... Old style is the stacked black nobs and the 1231 is the single red ones.

Comments!

How about a DIY to top up the fluid ;) And the low down on Staublis?

What do the dyno numbers mean? Is it pressure v. travel?

So the older 2-way race like mine can be updated to 1231, right? Would it be worth it, or just a waste, to update to the old-style 3-way? I.e. using the left over parts from those who upgrade from old 3 to new 3.

What about shaft diameter? Old was...? New is...? Is it a big deal?

What viscosity oil do you use?

How often should one get these rebuilt? What's involved in the rebuild? Just seals and oil?

Man, you want questions, I got em :D

I guess that what I need is a "Adjustable-Dampers-With-Remote-Reservoirs-For-Dummies" book.

Francois, looking for old style 3 way cannister?

Haha, not yet. I just bought a set of freshly rebuilt 2-ways from Tim, so I'm good for a while until I figure them out. After that, I might be ready to add a bit more complexity.

It's not a simple guide "for dummies" and could use some editing this book is a good resource and is written by the founder of JRZ:

http://www.amazon.com/Vehicle-dynami.../dp/1449059163

For some free info check out the Penske Racing Shocks manuals:

http://www.penskeshocks.com/Downloads.php

Thanks great christmas gift for me.

I use SRP fluid.... A old engineer told me "the fluid is the tire of the shock" and its very true... Shock rebuilds and fresh oil is probably the most neglected part of a race car. I rarely see them unless there is a blown seal but once a year is recommended. Two or three year old fluid is black and sludgy, kinda like never bleeding the brakes! Thats how it reacts soft and spongy... Damper oil breaks down just like engine, gearbox, or brake fluid..... For example in the Pro's we rebuild after every race, which is excessive but once a year should be the standard...

As far as bleeding and field filling? Thats why guys like me have careers! Its doable but not without a tool kit from JRZ for disassembly thats around $1400 retail....

A rebuild involves seals, oil, and cleaning and dynoing. Standard price for that is industry wide $850 for all four..... I am doing them for $650 as a winter special :) The deflection shims on the valves and the piston get really gummed up and after a while when the oil breaks down it can cause the guides to wear out prematurely.

Piston diameter? latest and greatest is 25mm..... I would love to sell them to everybody but to be truly honest unless you are running a cup car on Michelins with Pat Long driving I don't see the investment... for club racing you guys just arent producing the lateral tire load that a bigger shaft demands.... wait till you bend one and then replace them all :) (only going to bend on impact)
I would look at uprading the guides for sure in the front if anything... the new ones that came out two years ago are $160 a piece and are twice the length as the original design... it makes a big difference in wear and tear and longevity of the guide. (not a performance thing just a reliability thing)

Yes three way valve heads are a possibility..... there are guys that change them out to the 1231 and sell the old ones. I just did some for a old 911 fronts only that my customer is looking to sell..... (he only did the upgrade in the front which is quite popular)

The dyno traces that I do are force vs velocity.

You meant shaft diameter right?

What size pistons does JRZ use? Do you find metering the shock oil at the reservoir versus at the shock (like Ohlins/Penske) makes a difference? Also, are you a fan of higher or lower reservoir pressures. Talking to a couple of people at PRI I heard some really good reasons for lower reservoir pressures.

Matt:

Sorry for the typo yes it is shaft diameter.... with a 44mm piston..... One advantage of the larger piston that I neglected to mention is that it increases the blow off valves responsiveness.... but thats a whole 'nother technical discussion that should be done over beers :)

I am a fan of the remote reservoir.. it increases volume in the shock itself and increases oil which helps dissipate heat.... which decreases foaming and aeration of the fluid for one reason... Another reason I like it is there is maximum volume for air pressure...

I like lower pressures, lots of compression (something no one wants to do :):):)

Nice. If I had a set of JRZ's, I'd send them your way!

Thanks Cory, and Tim, please keep it coming.

Anytime!

Do you have any graphs to compare the adjustment setting from the new to the old style? Or against other shock manufacturers?

Yes I should have some in my files..... I can email them to you next week?

I don't need them for me - I thought it would be a good illustration to everyone on how the upgrade helps and how the shock adjustments work.