It's an rx7 specific dampener. Meant for street/sport stiff spring rates...
The limit for the dampeners I'm told are:

400 lb-in spring for fronts
300 lb-in spring for rears.

Anymore and the shock won't be able to dampen them on the highest setting.

I run 400 and 250 right now.

As you can see from the above pic of a 17 year old rx7 with stock suspension never touch before, I did install my shocks correctly as per mazda. It is Mike who is wrong... which makes me even more mad.

 

If you are going to change, I think you might be better off looking for a more dedicated race damper. Obviously, it is all money and I understand that. I am thinking about contacting www.sellisengineering.com for my needs. No affiliation, no experience, etc, etc, but it might be worth calling them and see what they say. If you call them, please post how it goes.

 

In reality, I'm looking for a budget basement setup that works good, not the best. Hence I chose those bilsteins.

I may try these guys: http://hotbits.ca/

They are down the road from me, canadian, and looks like they are very active in the ontario amatuer motorsports scene.

 

On the products page, Ellis is advertising a complete coil over shock with valving to your specs for $105.90 (US). That is cheaper than anything else I can think of. Implications of that are of course both good and bad.

I think a couple of Focus guys have run the Hotbits and been quite happy. Would be a good choice especially if they are local to you.

 

Again I stress that you want a spherical bearing or a softer rubber bushing that will allow the shock to move freely.

If the shock bushing you use does not allow free movement of the shock then the shock itself is still trying to bend every time the suspension moves. You already know the worst case scenario with the solid bushing. If your bushing at all restricts the degrees of freedom the shock needs you're placing a great side load on the seals and bushings around the shaft in the shock body. At best the shock isn't as responsive due to friction, at worst the seals wear more quickly. Shocks are not meant to be structural members of the suspension. They are not struts.

 

Don't get me wrong guys, I uh.... wonder.... about a lot of things I've seen on cars that have come out of that shop I'm just not going to flame Mike because my name is on these posts and I see him at the track most weekends.

I just don't let him work on my car....

 

Thanks for all the replies guys. ISC is sending me a new shock. I should have it no later than Tuesday June 6, 2006. I live in Canada so it takes a bit of time. I have a race June 9, 2006... so we shall see if I can make it.

I'm willing to give the guys at ISC a 2nd shot. The shocks/setup perform well on the track so I'm not just quite willing to give up on it just yet... I will follow Mike's advice and turn the washer/cup around so that it does not contact the delrin bushing but rather the bushing sleeve... and see what happens.

I'm going to be running brand new R comps on the 9th, 10th and 11th, rather than 4 year old Toyos so i'm pretty stoked to see how many seconds I can take out of my last year's lap times. Wish me luck.

 

Frustration comes from doing the same thing twice and expecting different results. I personally wouldn't want to drive hard into a corner with the thought of a shock breaking in the back of my mind.
At the very least find a stock rubber bushing for the shock. I'd hate to read your future post that might be titled, "Shock broke and I backed it into the wall HARD--- Car is a write-off"

Just my 2 cents worth(2 1/2 cents Canadian )

 

Would drilling some holes in the delrin help or perhaps just make a nice place for a crack to start?

 

Any chance you can give me some details on your car and the front dampers as well? Thanks.

 

I guess you could drill the bottom of the bilstein bushing sleeve to accept a zerk fitting and run grease into it every so often?

 

I wasn't thinking to add lube, but to increase compliance. A little air in there might reduce bind and flex of the damper.

 

Delrin is self lubricating and IMO drilling holes will make a place for a crack to start.

I would make the hole in the center bigger on each end and keep the center 20mm by rocking a drill bit around the hole. That way you would have a small 'bearing' area in the middle but have some movement at the ends. Then put something like a hunk of rubber on each side of the shock to keep things centered but not binding. Something to act like a big rubber washer before the steel one.

The opposite could be done on the outside of the bushing by rounding off the ends to make it sort of a ball shape(or a football with the ends chopped off) That way the shock could pivot around a little.

 

please listen to Damonb as he has the answer. the "shock" will need to move as the arc of the suspension moves, struts are solid since they help locate the suspension. this is why the oem setup uses a rubber bushing on the shock and why real "race shocks" will have a spherical bearing. The delrin setup will break something eventually and will likely wear out the seals and bushings inside the shock. a decent set of shocks will cost about $1200 to $1500 minimum. Of course the sky is the limit for shocks. Tein and some others make some nice stuff for about $1500 for the complete setup(shocks, struts, springs, and camber plates). I think I paid about $2200 for my custom sized and valved Biltsteins(not "yellows" street junk). If your running an EP car 2 grand for shocks is not likely to impact the budget to hard. these are expensive cars to build and alot of things will be more expensive. save yourself a big crash damge bill and buy some quality parts.

 

? I have installed my washer on my suspension with the bevel facing the center of the car. Therefore the flat part hits the sleeve (metal part) and the rubber is closer to the beveled edge.

(Metal sleeve should not move. Its the rubber bushing in the bottom cup that you snapped that should move around?)

I thought when were were at the track the weld is no good from what little I saw of it.

Not sure If I made any sense.

 

I looked at the bushing sleeve under a Stereomicroscope in materials lab at work. The weld seemed good. I think it was welded by resistance weld where bilstein spins the shock body up super fast on a lathe type machine and slams the bushing sleeve into the bottom of the shock body.

You can see the straitation lines from the failure spots. Lines that run like a barcode across the surface of the break. You can also see that when you put the two peices together they are not flush anymore and that the weld started to neck before it broke. One side was in tension and the other side was in compression when it snapped.

 

I agree. the suspension moves in an arc to allow for camber gain as function of suspension compression. What would really be bad if there was any bump steer causing toe angle change as the suspension moved up and down. The delrin bushing would not allow for any compliance for that...

Right now there is still some rotational compliance around the mounting stud. But that is the only degree of freedom for where the delrin bushing interfaces between the shock bushing sleeve, and the mounting stud. In reality you need minimum of 2 degrees of freedom at that bushing as I depicted in an earlier picture.

I'm surprised I've been the only one so far with this failure.

 

I believe all mass marketed shocks are assembled with the resistance weld method. On a street car installed properly with the correct springs for the application and a rubber bushing the shock should last for more than ten years of street driving. on a race car that sees limited use it may last for 5 years. alot of people don't keep race cars for that long and parts get replaced over time. In my opinion this setup is just not very good technically. It may "work" for short periods of time and good drivers can make bad cars fast at times. just because a car/driver is fast doesn't mean he has the best setup or parts installed. It maybe that the driver is much better than the competition and his machine doesn't have to be the best engineered.

 

http://www.teamfc3s.org/forum/member...view&car_id=78
sorry for the cross link.

But she's just a stock 89TII massaged a little for SoloSprint racing in Ontario Canada. Which is similar to your NASA Time trial HPDE type events in the states.

The front dampeners are stock shocks with the guts removed. THe body is then reworked to accept a Bilstein insert, which goes to a Ground control camber plate. I run 2.5in OD race springs. 10 inches long.

400 lbs in the front
250 in the rear
no rear antiroll bar.

 

I see your bilstein is from a BMW. On my FC, I run the old Mazdaspeed Motorsports kit and it came with Konis. I believe all the parts are sourced from AWR Racing. AWR racing is also now using/suggesting Bilsteins in their current kits according to their website. The Koni rear shock from my kit is from a Porsche 914 rear and the Koni number is 8241-1050. The koni I use still has the original rubber bushing from Koni. Mazda motorports supplies a larger diameter stud that replaces the factory lower shock stud. The part number is/was 0000-04-7214-AA.
I am thinking if you want to run Bilsteins (but not the factory replacement Bilsteins as the Porsche 914 struts have a much larger shaft) you could probably get the Porsche shocks and run the Mazda Motorsports stud. You'll have to check on the upper strut plate to see if that is the same though. On the other hand, you could probably contact AWR racing and see if they are running the same stuff as ISC racing or what Bilstein they are using because it does not say on their website.

Just trying to give you some more options.

-Jack

 

Speaking of options, and since this is a Bilstein thread, does anyone have any insight into what valving numbers one would specify during a custom revalve?

First, check out this thread on HybridZ that deals with adapting inserts to front strut housings. The first gen RX7 and the Z car are very similar in terms of front suspension design, and I imagine that even second gen guys might find some of the info useful.

Second, check out this PDF of Bilstein Motorsport dampers. While there aren't any RX7s on the list, there might be some cars that are similar enough to get some ideas from.

Third, look at this Bilstein stuff from a Volvo guy. Again, not the same car, but might offer some ideas.

Note that the Bilstein valving numbers are at .52 m/s and rated in Newtons (I think) while most domestic parts are rated at 3 inches/second and in pounds.

The reason I ask is I have a pair of P30-0102 inserts that I am considering using on my car. They are among the smallest (total height) inserts, and I will need to have them revalved and rebuilt before use. Any guidance, thoughts, contacts or information that I can use before I call Bilstein would be great. It is not that I don't think they can help, I just prefer to enter into any situation with as much information in my corner as possible.

 

I'd just send it back to bilstein to have them revalved for 65 bucks each. Call them and see if they have any info on the required bump and rebound dampening rates for a 1st gen rx7. They should have some.

All I can say is the ISC ones need ALOT more rebound dampening. Even just putting your weight into the shock you can see the shaft flyback up at great speed. There is very very little rebound dampening. But it seems like it has a lot of compression dampening

 

Well, doing that is one option, but I would like to know what they are talking about if I am presented with any options. Again, I don't doubt that they can do a good job, but with all the RX-7 racers here, perhaps I can get to something better than just good. Can you call ISC and see if they have the Bilstein valving numbers for the shocks and struts they provided you? That would give us a known baseline.

 

They just buy the bilstein dampeners from a distributor. Open the box. Throw away the box. Slide a threaded sleeve over the shock and then bolt the upper mounting plate on and ship it to me. It's an off the shelf part. Whatever a 1971 BMW 2.8L Bavaria's dampening rates are is whatever I'm running.

 

OK, but why did they choose that damper? It isn't like Senior Six BMW is a natural choice when looking for parts. Maybe it fits particularly well and that is all there is to it. I am just wondering if they had some inside info on the damping of those particular units because they really aren't one that would spring to mind.

I know that there is another company that says that particular Mustang rear shocks fit and work well on some RX-7s. I can see a situation where you are running your RX-7 on track, someone with a Mustang pulls a shock and you go "hey, that might fit my car and I bet the valving is stout because Mustangs are heavy." I've run with BMW CCA, and the chances of that happening with a Bavaria are about zero unless you knew Al Taylor when he was running his! See what I am getting at? Does ISC have a valving reason to use these shocks? Since you have the shocks, I was hoping maybe you would ask them. More likely to get a non-sales pitch answer than someone they don't know, like me.