JRZ shocks vs Bilstein RSR shocks

[Abby3.2Carrera]

Hey Guys,
I recently got my hands on a 87 G50 and in the process of rebuilding the suspension for track duties. The car will be used on the track whenever I have a chance; it will be used on the street as well during the weekend and such.

I have 2 options in mind, one is JRZ race double adjustable and the other one is RSR Bilsteins custom valved. the price difference between both set ups is $4500. I can afford the difference in price, but having a hard time justify it.

For guys with JRZ set up, would you guys say they worth the extra money? What are your experiences with JRZ shocks compare to RSR shocks or bilstein shocks in general?

I am a novice and have about a dozen track days under my belt. Will I be able to use the JRZs to their protential at my skill level?

The car will have matching torsion bars for either shop ,camber plates, front and rear bushings, bump steer kit, sways, big brakes, rear bolt in roll bar, 8" and9" fuchs on r-compounds.

Thanks a lot guys!

[Randy W]

It takes a while to figure out the best settings for JRZ double adjustable shocks, but once you have the numbers written down you are pretty much set. After a lot of testing (and help from experts), I have three different basic settings for my '72 T/ST: street, track, and autocross. Then there is the wet set up, which is softer. You are varying rebound and bump damping to match the shocks to the rest of your suspension, tires, the usage and surface conditions (smooth or bumpy track, low or high speed, etc.).

The advantage of double JRZs over Bilsteins or single adjustable shocks is the ability to match all this stuff, plus whatever changes you might make to your torsion bars over time. Double adjustables are worth it if you drive to the track, do both touring and competition, are a serious autocrosser, and/or just like to fiddle. The differences can be felt, are easily repeatable, and can inspire confidence to shave lap times.

[Abby3.2Carrera]

Randy,
Thanks a lot for the feedback, much appreciated!　
I have a feeling this is the route I should be going. It will be money well spend in the long run.

[moneymanager]

Everything Randy said is right and I wish I had JRZ's myself. But I'd offer a different view. Unless you are Schumacher it will likely be 30 or 40 events before you even realize you need different shocks. Run some standard Bilsteins, (or the sport version at the back if your rear torsion bars are 30mm or more) for a year or so. Get some experience then make your decision. After about 80 track events I switched from stock Bilsteins to a very stiff custom revalve to deal with one corner on one of the tracks I run. Nowhere else have I ever felt the need for different shocks. The car is faster. But I just switched back to rear sport shocks because the car was so stiff my fillings were coming loose.
Obviously I'm a slow learner, but I would hazard a guess that there are fewer than 50 people on this list who can actually drive a car at speed and correctly diagnose the need for different shock settings. Most of us simply can't interpret what we are feeling with much precision or don't really understand what shocks do and don't do. So my suggestion would be to play with torsion and sway bars for a while with good stock Bilsteins and leave the shocks for down the road.

[Abby3.2Carrera]

Moneymanager, thanks for the feedback.
I agree at my skill level, I am far from feeling the car and making adjustments on the shocks at the track unless the settings were given to me for different tracks.
JRZs are definitely appealing for longer terms if you break down the cost over 5-10 years, but they will require more maintenance. Bilsteins are set and go, and offer probably 90% of the performance on a smooth track. for the price of the JRZs, I can have both custom valved rsr bilsteins and 930 or brembo brakes.
decision decision

[winders]

Get some custom valved Bilstiens and save yourself a whole bunch of money and headache.

Out here in Northern California, there are many well driven and very fast 911 race cars (without budget limitations) that run custom valved Bilsteins instead of JRZ, Moton, Penske, or Ohlins multi-adjustable remote reservoir dampers.

Scott

[RichardNew]

I really like the custom Bilsteins. Just let them know what sort of suspension you have and let them make the decision. They usually give you a little more rebound than necessary but that's never a problem.

Adjustable shocks can put you right out of the ball park. You have a very good chance of going the wrong way with your adjustments. The problem is you'll never have enough experience to know you've totally screwed up.

Richard Newton
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[cstreit]

THe question is really, do you have the knowledge and experience to really set them up? I have triple adjustable JRZ's on my Cup Car and even with professional help, they can be a challenge... It's not always intuitive.

Frankly I almost wish they weren't adjustable.

Of course the benefits of getting it right are higher, like being able to run a soft setup in the rain and stiff on the fast tracks, but the downsides of a WRONG setup are just as significant. Be honest with yourself, how much are you willing to do? How much track time do you get, it can take a full day to really hone in on a setup on one track.

[Randy W]

Some really good counter arguments made - mostly from guys with race cars. For guys who drive their car long distances to the track (say WA to CA), have spent a day test tuning the shocks for different conditions (say with a guy like Greg Fordahl), and are willing to pay for shock rebuilds every few years (I'm not, but I do it anyway ), well.. double adjustable JRZs are something to consider. I agree that with triple adjustable shocks it gets more complicated, especially when you consider no track has all low speed or all high speed corners.

I personally would not go back to non adjustable or single adjustable shocks - unless I had a dedicated trailered race car or a dedicated street car.

[Abby3.2Carrera]

Guys, all the feedback appreciated.
I really have no knowledge to set it up from the starting point, let alone set up for different tracks. I will get on the phone with Steve@rennsport again tomorrow hopefully I can get the order settled.

[winders]

Originally Posted by Randy W

I agree that with triple adjustable shocks it gets more complicated, especially when you consider no track has all low speed or all high speed corners.

The high and low speed compression adjustments on the triple adjustable JRZ dampers have nothing to do with low or high speed corners.

The high-speed compression circuit relates to events when the damper shaft is moving quickly in bump such as on rough or uneven track surfaces or curbing. The low-speed compression circuit relates relates to events when the damper shaft is moving slowly in bump such as during corner transition, braking, and accelerating.

Scott

[Randy W]

Originally Posted by winders

The high and low speed compression adjustments on the triple adjustable JRZ dampers have nothing to do with low or high speed corners.

Nothing? Really?

Originally Posted by winders

The high-speed compression circuit relates to events when the damper shaft is moving quickly in bump such as on rough or uneven track surfaces or curbing. The low-speed compression circuit relates relates to events when the damper shaft is moving slowly in bump such as during corner transition, braking, and accelerating.

Scott

You have just described high and low speed cornering events.

At least you did a better job than I did!

[Pete R]

Just a couple observations.(I know nothing of those shocks but) Personally, every time I have something "adjustable" I adjust it..... and usually make it way worse than if I just left it alone, and I usually can't get it back to where I started . $4500 is a lot of seat time.

[winders]

Originally Posted by Randy W

Nothing? Really?

Nothing at all!

Originally Posted by Randy W

You have just described high and low speed cornering events.

No, I have not. Smooth fast tracks will have less instances where the damper shaft is moving quickly in bump than slow bumpy tracks. The damper has no idea how fast or slow the car is going. It only knows how fast the damper shaft is accelerated.

Scott

[Randy W]

The logic you are using suggests that the speed that a car travels over a bump has no relationship to the acceleration at which the damper shaft moves... Gee, I may have to test this on the speed bump outside my house at slow and high speeds! Hilarious!

[Eagledriver]

Every track has surface irregularities. If there was a perfectly smooth track we could run no suspension at all, like a go cart. When you hit those irregularities at high speed the suspension moves up much more quickly than at slow speeds. Think about a rock climbing 4X4 going 2 MPH. The tires move up and down very slowly then. This is part of why a race set-up is not the same as an autocross set-up.

-Andy

[Cajundaddy]

Originally Posted by Pete R

Just a couple observations.(I know nothing of those shocks but) Personally, every time I have something "adjustable" I adjust it..... and usually make it way worse than if I just left it alone, and I usually can't get it back to where I started . $4500 is a lot of seat time.

+1

I think the JRZ system is a marvelous setup for a very experienced driver who really needs precise dampener control AND has a deep understanding of how to fine-tune his dampeners from track to track... or has a trackside suspension tech on the payroll. It also depends a lot on the tire choices. The more lateral Gs (racing slicks), the more precision dampener control is needed.

For the rest of us, "Keep It Simple Stupid" just works better.

[winders]

Randy and Andy,

You guys crack me up. Our cars aren't traveling at speeds close to 2 MPH. Well, at least mine isn't.....

Look here:

Sports Car/Formula Car - 8770 Series canister option

Here is some text from that link:

Tuning Adjustments:

Low-speed compression:

30 clicks of adjustment control the low speed nose area of the curve. This adjuster is used to tune role stiffness, turn-in, and understeer.

High-speed compression:

64 clicks of adjustment control the high-speed blow-off area of the curve and adjusts gross threshold of compression damping. This adjuster is used to tune bumps and curbs, and to gain a general direction in damping levels.

Funny. Penske doesn't mention high versus low speed corners. I wonder why that is?

Look here too:

How dampers work

And here:

Bos Engineering Suspensions

And here:

How to turn a grocery getter into a world beater in 60 days: Part Six

Scott

[Cory M]

Before spending $4500 on some new JRZ's you should consider spending $17 on this book written by the founder of JRZ:

Vehicle dynamics and damping: Jan Zuijdijk: 9781449059163: Amazon.com: Books

It might make you decide a "set it and forget it" system is better for you, or it might make you decide you need 4 way adjustables!

[winders]

Originally Posted by Randy W

The logic you are using suggests that the speed that a car travels over a bump has no relationship to the acceleration at which the damper shaft moves... Gee, I may have to test this on the speed bump outside my house at slow and high speeds! Hilarious!

That is not the logic I used. It is the logic you [incorrectly] surmised I used. Yes, you are correct, the faster the car is going the faster the damper shafts moves when going over a bump. However, if you go over that speed bump outside your house at 30 MPH or 80 MPH, the high speed compression circuit is going to be dealing with it. Go 5 MPH over it and low speed compression circuit will most likely be involved.

The fact is that at normal track speeds, high and low speed corners do not correlate to the high and low speed compression circuits.

Originally Posted by Eagledriver

Every track has surface irregularities. If there was a perfectly smooth track we could run no suspension at all, like a go cart. When you hit those irregularities at high speed the suspension moves up much more quickly than at slow speeds. Think about a rock climbing 4X4 going 2 MPH. The tires move up and down very slowly then. This is part of why a race set-up is not the same as an autocross set-up.

Yes, you are correct. All tracks have surface irregularities. Did I say they did not? See what I wrote above.

An autocross setup usually requires more compliance because parking lots are often quite irregular. Also, understeer is a bigger issue so it is common to have a stiffer rear setup. Most of the bumps you hit autocrossing would be controlled by the high speed compression circuit. Even in the slowest corners.

Scott