119 replies to this topic

[Jim Drago]

I am just wondering if the change may be just a bit softer of a stop in the rear and eliminate the front black hard spacer. What is the purpose of that anyway other than to suck up shock travel?

 

I believe the purpose of that is to keep the tire from crashing into metal fender well. We need that as we can still get to the fender well, but we just touch it now and it is a non issue.  

[Steve Scheifler]

I suspect that they can’t go softer on the rear orange stop. Based on what we’ve seen people are already fully compressing it under extreme conditions (at least) so softer just means a harder ultimate hit in those cases.

Just guessing, but the front stack may be closer to what they would do in back if they could. The front is heavier and probably takes more abuse particularly when hitting bumps while cornering, so a more progressive stop is useful on the steering end. Also, it may be that they come into play under threshold braking, more weight transferred forward. They could reduce nose dive and make it more stable over irregularities than just a single hard bump.

From my experience, the single most important thing about typical “protection” bump stops is to not get deep into them on one end of the car before the other.

[Ron Alan]

Ask and you shall receive Bench!

 

http://www.mazdamoto...Explanation.pdf

 

http://www.mazdamoto...Shim-Update.pdf

 

The engineers have spoken! Not going to worry about the shim(if you do then get the optional shim)nor the occasional bumpstop STRIKE! And as Jim mentioned above and the engineers also addressed...the chassis limits the ability to allow the shock more travel...basically we can already find it(but not advised!). 

[gerglmuff2]

pretty through explanations of both. 

a thicker shim is a nice touch though. 

[Bench Racer]

Thank you Ron and Mazda/Penske for the shock photos with dimensions. With your info I understand why the rear top shock mount can not be mounted higher.

[Steve Scheifler]

It was good of them to respond quickly. I’m not sure we learned much of anything new but they confirmed what Ralph and others have supplied. The statement about an extra inch of travel is a little misleading if taken alone but the diagrams and charts make it clear enough.

Assuming all the facts are accurate then they have increased the metal-to-metal travel limit by 1/3 inch. That’s key because once you get into the Penske stop it almost immediately becomes more firm than the old one, so from about 0.05” into the Penske the rate is higher than the same absolute position with the old one, then at around 0.25” the Penske still has some compliance while the old one has become effectively solid.

The extra resistance in that last 1/4” is not insignificant. Pulling from the chart is imprecise but if I’m getting this right it is hundreds of pounds to over 1000 (compared to our springs of 325). If we typically get into that range only over curbs and such then it’s probably manageable. If at your “typical” ride height you frequently use that much travel for cornering then expect problems, probably a mid to late corner loosness for starters. BUT, if we are in fact gaining 1/3” in absolute travel, and assuming that is not somehow reflected in the charts, then the green Penske lines effectively shift right that amount. Have I got that correct?

[38bfast]

Steve you also have to account for their higher compression dampening rates of the Penskes. The new shock will have a lower volicity when moving into the stop. This has to be looked at as a package than just comparing stops and travel.

Bottom line is ride height will be determined by the stop watch. Same as before. Some tracks will be faster low and some will be faster high. Same as before. Let your lap times dictate your setup.

[Steve Scheifler]

Steve you also have to account for their higher compression dampening rates of the Penskes. The new shock will have a lower volicity when moving into the stop. This has to be looked at as a package than just comparing stops and travel.

I get that Ralph, of course, and have made that clear previously. I was just trying to fit this new information into what we had already learned orcthought we’d learned. But to your point, as I also mentioned earlier, unlike the Penske pieces the FC stops served as a tuning device/compression damping substitute, slowing down the movement before it approched a hardness comparable to the Penske. Point being, looking at the differences in high & low speed damping also isn’t enough either. At a nominal height of 4 5/8 I expect the FC stops came into play quite a lot which would make your shock dyno graphs look quite different. Indeed, if setting up exactly that scenario on your dyno is practical it would seem a logical and direct way to get a reasonably accurate comparison.

[Steve Scheifler]

...
Bottom line is ride height will be determined by the stop watch. Same as before. Some tracks will be faster low and some will be faster high. Same as before. Let your lap times dictate your setup.

This is also very true and why I remain just slightly concerned about the only worry I’ve had from the start. The Penske paper mentions that people are worried about the need to run the cars higher and refuted that well enough. Speaking only for myself, my ONLY reservation at the outset was not about typical height but rather the penalty paid by those who opt to run a bit lower as a cheap fix for missing camber, a long established issue. I still would like to see a slightly shorter shock body and they didn’t really address why that’s a bad idea, but I accept that they are the experts and regardless it is done. If my interpretation of the data and diagrams is correct then my concerns have been largely addressed pending evidence to the contrary; that extra 0.3” (after new shim) of absolute travel should keep us from hitting excessive bump resistance earlier than before. Maybe not significantly better than before but not worse.

[Martinracing98]

From my experience, the single most important thing about typical “protection” bump stops is to not get deep into them on one end of the car before the other.

This does not seem likely to happen for SM, which should assure that we will want to pick a height that we are seldom on the stops

[Steve Scheifler]

You seem to say it is unlikely in SM? Hopefully less so now because the cost will be higher, but it has always been an issue largely mitigated when we adopted the NB hats for all and later the progressive FC bumps. Your statement that “we want to pick height that we are seldom on the stops” is now precisely the core issue. If you can get the camber you want/need at a safe height then splendid, but if you try to fudge a little lower the change in handling under certain conditions will be more abrupt, particularly for the rears. It is interesting that they shortened the fronts by about 0.55” then “spent” some of that by adding a second (softer?) bump rubber. There seems to be some discrepancy here between description and diagram, hopefully someone can clarify with actual thickness and relative hardness of those two pieces in the front stack. In any case, even if you get into front & rear at the same time they may progress differently.

Part of the problem with their explanation stems from the arbitrary ride height (RH) parameter. I have no idea where it comes from and can only hope that their 15” F & 12” R values equate to “level” based on the popular pinch weld approach. They may have checked for levelness of the chassis by other means so the F/R comparison may be off a bit from pinch welds. In any case, many people actually run NBs lower in back than front, something we never did with our 1.6s which seemed to rotate better with a little rake and probably helped aero.

[Martinracing98]

Your statement that “we want to pick height that we are seldom on the stops” is now precisely the core issue. If you can get the camber you want/need at a safe height then splendid, but if you try to fudge a little lower the change in handling under certain conditions will be more abrupt, particularly for the rears.

 

I agree it may end up being an issue. I am still holding out hope we will be the camber at a safe height. If night we will all have debate(argue) for 6, 7, or more pages about what to do next.

[Jim Drago]

I was at the 24hr.. just read the Penske article. I think it was very thorough and answered all the questions that I had and addressed all of my concerns. As i said from the start,  I love the shocks..  I had no teething issues or learning curve... I felt they were great from session one. I was only concerned post race after seeing the washer deformation.  I set my car higher as a precaution.. I never felt the hard transition to the rear stop that others felt where they were snapping loose.  That seems to concur with Penske's latest data sheet. After reading that, digesting the two weekends on the shocks.. I feel with a very high level of certainty that the deformation of my washer was likely done at T1 Homestead and not Sebring.   I will be heading to Cota next, a track that we have historically set the cars a little lower. I will likely mirror previous bilstein heights from years past and see how the car responds. I don't anticipate any issues.  One thing to consider, if the travel were identical to the billstein, It would be a good bit harder to get to the stop because the shocks are so much stiffer. It is hard to even bounce the cars now. I will report back after Cota.  I think hitting the stop in incidents where we slam curbs, drop wheels or go off roading is going to be inevitable. I will likely not bother to change the washer until time permits and/or we have the suspension apart again for some reason. 

[RWP80000]

You seem to say it is unlikely in SM? Hopefully less so now because the cost will be higher, but it has always been an issue largely mitigated when we adopted the NB hats for all and later the progressive FC bumps. Your statement that “we want to pick height that we are seldom on the stops” is now precisely the core issue. If you can get the camber you want/need at a safe height then splendid, but if you try to fudge a little lower the change in handling under certain conditions will be more abrupt, particularly for the rears. It is interesting that they shortened the fronts by about 0.55” then “spent” some of that by adding a second (softer?) bump rubber. There seems to be some discrepancy here between description and diagram, hopefully someone can clarify with actual thickness and relative hardness of those two pieces in the front stack. In any case, even if you get into front & rear at the same time they may progress differently.

Part of the problem with their explanation stems from the arbitrary ride height (RH) parameter. I have no idea where it comes from and can only hope that their 15” F & 12” R values equate to “level” based on the popular pinch weld approach. They may have checked for levelness of the chassis by other means so the F/R comparison may be off a bit from pinch welds. In any case, many people actually run NBs lower in back than front, something we never did with our 1.6s which seemed to rotate better with a little rake and probably helped aero.

Steve, 

I'm with you on not knowing where this ride height reference is actually referring to but from the Penske recommendations of setting up the shocks for 10 1/8 inch front and 6 1/8 inch rear, the data provided from our car which is a new build in 2018 with only two races on it and decent Pinch weld flanges showed that our car was about as level as you could expect.  Personally, I have no use for the Pinch weld data as these are so prone to damage/distortion as to be meaningless for talking setup differences vehicle to vehicle.  That is why I have always shared set up info based on measuring from the bottom of the threaded adjuster sleeve to the bottom of the spring seat adjuster collar.  Even with that there can be car to car differences but I have found in general that to be minimal.  I use a Starrett T-square ( 6 inch 1/4 wide ruler with 2 1/2 in wide base) and reference the readings in 1/64 inch increments typically something like 1 37/64th of an inch.  It can be done from underneath the car or if you want to raise the car and remove the wheels you can do that as nothing is going to change the as set measurement where as with flange height you need the driver or ballast for the Driver.

 

Penske/Mazda elected to perform a similar measurement but used a reference from the actual spring seat surface to the centerline of the lower mounting bolt.  To use this measurement reference on the car, I would need to modify the lower mounting bolts to provide an extended center point extended so a tape measure could be used but I feel the tape measure is more prone to reading variability as well as scale resolution so the reason I established the correlation of their reference values to my method. 

[Steve Scheifler]

Thanks Rich. We too based our heights on measuring from the bottom of the collar to the bottom of the perch. For approximate rake and levelness we use a digital level on door sills and the back shelf (multiple locations to get as close and repeatable as possible). We then use the pinch welds as a sanity check and for comparison to other people.

As I’ve noted before, the issue with just the collars is that “height” is then relative to the weight on that corner so equal measurements left to right are not necessarily equal height even if everything else is perfect. Hence the digital level, especially for initial setup. In the past I also measured from a beam between the scales up to marked centers on the camber bolts but that was a pain and far enough inboard to make the L/R resolution rather low.

And of course using the perch measurements saves a lot of time with track-to-track changes and getting close quickly when setting up additional cars the same way.

[Jim Drago]

Thanks Rich. We too based our heights on measuring from the bottom of the collar to the bottom of the perch. For approximate rake and levelness we use a digital level on door sills and the back shelf (multiple locations to get as close and repeatable as possible). We then use the pinch welds as a sanity check and for comparison to other people.

As I’ve noted before, the issue with just the collars is that “height” is then relative to the weight on that corner so equal measurements left to right are not necessarily equal height even if everything else is perfect. Hence the digital level, especially for initial setup. In the past I also measured from a beam between the scales up to marked centers on the camber bolts but that was a pain and far enough inboard to make the L/R resolution rather low.

And of course using the perch measurements saves a lot of time with track-to-track changes and getting close quickly when setting up additional cars the same way.

Something tells me that this wouldn't work well if we compared numbers   

[Steve Scheifler]

Something tells me that this wouldn't work well if we compared numbers

I didn’t want to say, but yeah. Nor would it work too well between me and Preston Pardus. Fortunately Tom and I are within a few pounds of each other and the cars were very similar so after setting up one car I would start the next with perch heights.

[Jim Drago]

I didn’t want to say, but yeah. Nor would it work too well between me and Preston Pardus.

Even worse.. Preston and I usually roll on and off the scale back to back  

[Bench Racer]

You seem to say it is unlikely in SM? Hopefully less so now because the cost will be higher, but it has always been an issue largely mitigated when we adopted the NB hats for all and later the progressive FC bumps. Your statement that “we want to pick height that we are seldom on the stops” is now precisely the core issue. If you can get the camber you want/need at a safe height then splendid, but if you try to fudge a little lower the change in handling under certain conditions will be more abrupt, particularly for the rears. It is interesting that they shortened the fronts by about 0.55” then “spent” some of that by adding a second (softer?) bump rubber. There seems to be some discrepancy here between description and diagram, hopefully someone can clarify with actual thickness and relative hardness of those two pieces in the front stack. In any case, even if you get into front & rear at the same time they may progress differently.

Part of the problem with their explanation stems from the arbitrary ride height (RH) parameter. I have no idea where it comes from and can only hope that their 15” F & 12” R values equate to “level” based on the popular pinch weld approach. They may have checked for levelness of the chassis by other means so the F/R comparison may be off a bit from pinch welds. In any case, many people actually run NBs lower in back than front, something we never did with our 1.6s which seemed to rotate better with a little rake and probably helped aero.

SHAFT SPACER & BUMP RUBBER : • Black Delrin spacer limits stroke - .75” long • Orange polyurethane bump rubber - .75” long
 

[Steve Scheifler]

SHAFT SPACER & BUMP RUBBER : • Black Delrin spacer limits stroke - .75” long • Orange polyurethane bump rubber - .75” long

Ah, thank you, I missed that. So just one and the same material but 50% thicker. Does leave me wondering why they shortened the tube but perhaps it will be more versatile for other applications or is an already common length for them.