242 replies to this topic

[Steve Scheifler]

Dave, you certainly aren’t wrong about the tires being a major factor. As I’ve said before, we could switch to a much less expensive bias-ply construction that wouldn’t work well at all with more than a couple degrees negative. But even if a strong case could be made for that we (the people paying for them) don’t have much direct influence on the matter.

Sure, other classes have similar issues but none are as scrutinized, or as easily scrutinized, as SM. Too many different makes & models so a lot more fudging is possible and frankly tolerated. At a minimum it has never made economic sense to force people to run less camber than a car needs for even tire wear (which is my gripe with certain SM “purist” spinoff classes).

I don’t recall the brief Hankook period being much different but we were out for most of that so I don’t really know. We always struggled with camber during the Toyo era and before that with the early Hoosiers. You may recall that the factory bump stops were also like bricks. You had to either be in them all around, or off them completely because the transition on one corner of the car at a time would cause it to push like a mother one second then snap into oversteer the next, even mid-corner. Guys who were fast back then and didn’t experience that had revalved shocks and bent parts to avoid it.

[Dave D.]

So what is the best way to deal with this? Turn a blind eye to the methods of achieving camber? Don't ask, don't tell? No sure....

One thing for sure, I am really looking forward to trying these shocks out! I have always hated the way the Bilsteins felt.

[Ron Alan]

It appears that the winning Miata at thunder hill 25 was on the new Penske

Ok...now for some real world reporting!

 

I was asked if I would be interested in running the new set up on one of my cars at the NASA 25HR of Thunderhill this year...this was a no brainier and I actually kept it from the drivers until the race!

 

I'm not a professional set up guy nor a driver...just enough info in my pee brain to get me in trouble! Take what I say here as just what I found/did...not what is necessarily correct or the best!

 

The shocks were shipped to me complete...just had to bolt them in. I was given measurements from the bottom of the adjuster ring/nut on the collar to the CL of the bottom mounting bolts as a starting points. This part is foggy right now but one of these measurements seemed really off? I believe it was the front because when I set the car on the scales for the first time my rear camber numbers were fine but  I had 1.5 degrees in the front with one maxed adjuster and offset bushings?? Visually the front of the car was way up based on the gap at the fender to tires...I could see the top of the tire! At this point I lowered the front of the car what I remember was about 1/2" and set it back down...ok, camber was back to acceptable then I bounced the car...shit! I went to far because it had to be on the bumps...it didnt move!!! But the rear of the car didnt move either...no way I could be to low there???? So now I was looking at the shock to bumpstop gap, all mounting bolts...had something hung up or did I do something wrong? In the end...I determined as Ralph reported these shocks are nothing like the softer Bilsteins...you are hard pressed to bounce the car!!!!

 

In the end I went back to my usual very unscientific method of car set up. Finger width(.5-.75") between the top of the shock and bumps under load and looking at the fender gaps. For sure the car sat up VS being to low...because when I felt the bumps I thought man those are hard...I dont want to be on them!  But then I 2nd guessed myself on this because I could hardly get the car to move when i bounced it...it's never going to get to them...LOL! Leaving the car up a little I did lose camber(maxed eccentric on one side)but this was my compromise to avoid finding out to low is a bad thing!

 

Being a very low budget program and lack of time trying to get 4 cars ready, this car never saw the track until Friday night practice and qualifying at the event!

My 4 drivers had a range of experience(10 years to 2 years racing) and all are on the faster end of the scale in a typical regional weekend. This was their overwhelming response...LOVED the car!!! A few specific comments that were made...Stable, less body roll, quick set, drove off the corners well, extremely predictable!

 

With that said here are my thoughts/caveats. First off, this race is not a "sprint" and all drivers know to find their pace. Driving a car a couple seconds off sprint pace always makes them feel better! But a couple of my drivers found themselves turning laps easily at a pace faster than i wanted them to run! In fact, they had to make a consciences decision to slow down a little...this even after they were already doing the small things we do in endurance to minimize car fatigue!

 

I guess I didn't think about tire wear much but in hindsight we had zero issue going the length of time I wanted to before changing! Obviously very pace dependent on tire wear...but with similar drivers over the years and the same tires, we did the time with ease and no corded tires! Also, I installed a new set of hubs from my local auto parts store(cheap Oreilly...Master Pro)...other than long studs I didn't touch them. Lasted fine! The P2 team lost both brand new Mazda taper bearing hubs  

 

Our pit space at this race is directly across from one of the bumpiest parts of the track. It is called the "bypass". The cars come over a blind rise and drive down an off-camber hill trying to maintain grip in a very bumpy gradual right hand turn before entering a left hand turn. Watching all speeds of cars drive this corner it becomes very obvious when suspension packages are different! And I could see this difference between my cars running the Bilstein's and my car running the Penske's! The amount the chassis moved vs the suspension was obvious! 

 

So in this very unofficial real world testing we found the shocks to be completely acceptable!

[Ron Alan]

Just to be clear...I'm not positive now were I really ended up with the measurement between the top of the shock and the bumpstop on the new shock. I remember thinking my fender gaps looked ok and the cross was good on the car. A visual at the gap was all I did to make sure there was one...then checked camber...all acceptable. I was going to measure the pinch welds but forgot! So I just did this(unloaded the car) and surprised to find I was some where around 4.2" in the front and 4.5" in the rear at the pinch welds...based on some previous readings maybe this was to low? Hmmm...maybe the numbers they gave me were correct...but my camber was not good at that height....

 

Well, they seemed to work though now maybe I was to low? Time will tell!

[infamousjim]

Just Sayin...

("Borrowed" from here: https://nomoneymotor....wordpress.com/ )

[Mitch Reading]

Ron,  Great write up... thanks for the share.

[RWP80000]

Thoughts to consider for those who will be doing their own installation and set up of the new Penske shock package:

 

It should be noted that the design dimension from the centerline of the lower shock bolt to the lock ring/groove on the shock body (used to locate the threaded adjuster sleeve) is supposed to be identical between the Bilstein's and the Penske shocks (comparing shock dimensions front to front and rear to rear).  It would be worthwhile measuring and recording your original shock package per the directions suggested for the Penske's just to see where you "stand" to the recommended specifications. (Are you within the 1/4inch window?)

 

Theoretically, if you locked your adjuster collar to the threaded sleeve before removing them from your Bilstein's and then installed them on to the new Penske and re-installed in original position location as removed, you should find your car virtually at the same ride height as before the shock change.  This also is based on using your existing Fat Cat upper spring isolator cushions in their original locations. 

 

There will be other variables that could have a small affect on what you might find.  Obviously, if the lower shock bushings in your Bilstein's are distorted from use there could be a small increase in measured ride height after installing the Penske's. Another potential variables that might affect ride height would be from a difference in the gas charge of the shock where a higher pressure could exert a small additional force on the shock rod to "lift" the car slightly.  I do not have any info on the gas pressure charge specifications between the two shock brands and I don't think this will likely be found to be a factor.

 

It is also expected that just the process of removing and reinstalling the parts involved will likely result in some small ride height variation, especially if you do not keep the preload on the suspension bushings at the same level as when originally disassembled.

 

Taking the time to record your starting point and where you end up would be a good recommendation in that if you find your car to be significantly different to what it was originally, you might want to double check your installation steps against the instructions.

 

Assuming the car is reasonably close to it's original ride height, you can now measure the top of shock to jounce bumper gaps (once you finalize your set up) so you have a new reference/baseline for use going forward in developing your set up.  Given that the reference dimensions are not easily measured with the shocks in place on the car, an easier measurement that has a fixed relationship to the reference dimensions is to measure from the bottom of the spring seat adjuster collar to the bottom of the threaded sleeve using a small scale with a locking T-square slide.  This value is unaffected by tire pressures or bent pinch weld flanges although you will want to have your tire pressure reasonably set to get accurate cross weight readings.

 

Rich Powers

[38bfast]

So right now the first Miatas that ran penskes in completion have won. 25 of Thunderhill and Champ Car overall win at Barber.

[Ron Alan]

So right now the first Miatas that ran penskes in completion have won. 25 of Thunderhill and Champ Car overall win at Barber.

Be careful Ralph...the first time we ran the new Mazda "Hubs" they had no issues

 

For some reason though I think this time we have a solid name behind the product with real testing!

[38bfast]

I just got the balance of my order today. So it appears Mazda is shipping stuff out again. 

[Sphinx]

Any suggestions for a decent chafer/deburring tool?  I couldn't find one at my local big box store.

[ChaseH]

Any suggestions for a decent chafer/deburring tool?  I couldn't find one at my local big box store.

 

McMaster Carr, Fastenal, Grainger or MSC will have countersinks in stock. Countersinks larger than 1" are expensive though...

 

Do you know any machinists? I'm sure they'd let you borrow one or they could deburr the holes for a few bucks. 

[Bench Racer]

If you have a small air driven hand grinder put a small stone tool in and gently grind burr away. 

[Sphinx]

McMaster Carr, Fastenal, Grainger or MSC will have countersinks in stock. Countersinks larger than 1" are expensive though...

 

Do you know any machinists? I'm sure they'd let you borrow one or they could deburr the holes for a few bucks. 

 

 

If you have a small air driven hand grinder put a small stone tool in and gently grind burr away. 

 

 

Thank you both!  Yep, a dremel with a small stone seems to work well.

[davidb]

So I'm wondering, would any of you guys "in the know", care to assure me that an expensive top hat "upgrade" isn't going to happen; before I invest in hats and FC isolators for my new build?

[Bul Winkle]

An observation from someone that is relativly new to this, so please indulge. I do have some professional experience with investigations with failure or damage in hydraulics and mechanical systems, so getting to root cause is where this comes from.

 

A common thread through the Penske discussion, and one that also occurred on the Bilsteins, is riding on the bump-stops vs having a minimum ride height. Simply, if you are on the bump-stops, this does not allow the suspension to operate in the range that the shock to operate in is designed range. Has anyone on SMAC gone back to Mazda or Penske to see what the parameters were that they designed this shock to?

 

Specifically on the Penske's, there is an interesting battle going about ride height vs. the resulting damage to some of the stack up components - something that did not turn up in over 1000 laps of testing. If they are not already engaged in an investigation here, that would be very surprising. I looked at the Mazda presentation, and the stickup does not look like is should be causing that damage, but it consistently occurs. It's either a missing part in the stack-up, or an installation/assembly issue that is consistently applied. OR - the cars are not set up to work in the shock's operating range (ride height). It's be good to get Penske's or Mazda's input on this, and prevent speculation from driving the discussion - and potentially more damaged parts.

 

Round three - Ding!

[Sphinx]

Quick assembly question.  When I went to torque down the top nut with my impact as Mazda recommended, the pillow assembly rotated.  It was properly torqued to 50 ft. lb.  Do I need to worry about dissembling and retorquing the pillow assembly?  I have no way of knowing whether just the top pillow nut only rotated or whether the bottom "bolt" piece did too.

[Bench Racer]

Bul Winkle, there's a reason Penske/Mazda/SMAC are telling Penske parts users to stay off the ORANGE shock protectors.  In the first approx. 2mm (.079 inch) of compression the rate is 600 pounds which is approx. two times the rear Spec Miata spring rate. The Fat Cat bump stops are a progressive spring rate of which we can use the first 3/4 inch.

[Bul Winkle]

I agree, which dictates a very different setup, a different driving style, or a combination thereof.

 

My question was only to get a better understanding of what the design guys were really thinking, then to see what their thoughts are for real world usage. These two items are not mutually exclusive. I am expecting a second technical bulletin (hopefully) ahead of COTA.I know how smooth that track is, but that alone won't inhibit the problem.

[RWP80000]

Quick assembly question.  When I went to torque down the top nut with my impact as Mazda recommended, the pillow assembly rotated.  It was properly torqued to 50 ft. lb.  Do I need to worry about dissembling and retorquing the pillow assembly?  I have no way of knowing whether just the top pillow nut only rotated or whether the bottom "bolt" piece did too.

If you were able to torque the lower "nut" to the upper "nut" and have all of the Belleville and shim spacer parts properly stacked over the lower nut and under the upper nut, then the "Monoball" bearing should be properly secured within the upper and lower "nuts" and in the top hat assembly.

 

If, given you achieved the specified torque, and you find the assembly loose in the top hat then, assuming proper parts stack, you have an issue with the thickness of the Top Hat in the area where the lower and upper nut assembly spacing sets the gap in which the shim spacer and three conical Belleville washers provide the preload limiting the amount of "play" of the upper/lower nut assembly within the Top Hat. 

 

If you find it loose, I would inspect the Top Hat,  as poor machining of the 15/16 clearance hole may have compromised the effective Top Hat thickness in the immediate area where the shim spacer and Belleville washers rest against the Top Hat surface.  I have heard reports of this happening when using a "step drill" to open the hole in the Top Hat.  On car symptoms of this are a clunking knocking sound heard at low speed driving around the pits or when pushing up and down hard on the car.

 

If you study the provided instruction sheet cross section view of this assembly, you will be able to see that there is nothing to prevent the rotation of the upper/lower nut assembly within the Top Hat. There has not been any specification provided as to what the torque to rotate tolerance for this joint should be. That said, if you find it to rotate effortlessly, I would change to another properly machined Top Hat. 

 

Rich Powers