KaiB

Much to not understand here, including the reasoning behind the ruling. Nonetheless, I feel I should begin to get prepared, as it seems Walt has dug his feet in and drawn a line in the sand on this one.

Cut and paste from the CR:

B. For all other models, any slider other than the Cup type must be approved by the PCA Club Racing Rules Chair, and
must mount to the chassis with at least one M8 grade 8.8 bolt at each end of each slider. Earlier cars which used 6mm
bolts must have the chassis mounting modified to accept 8mm or larger bolts. At present only the Sabelt double locking
slider is approved if a Cup or equivalent Porsche slider is not used.

Has anybody been in contact with PCA to inquire if other similar sliders may be used, i.e. a perfectly new double locking Recaro?

4. The chassis mount must be modified if not made to take an 8 or 10mm bolt, and in any event must also be reinforced by
additional steel welded around the mount if a floor pan mount, or connecting a cantilevered mount to the floor pan, so it
cannot flex, and the sheet metal holding the chassis attachment is reinforced to prevent pull through.

Does this mean that ALL factory mounts must be reinforced somehow? By what and by whom. Has anybody done a stress analysis. I assume it's OK for me to go to the barn and fire up my arc welder and have at it on a perfectly good 964 tub, never mind the fact that I have no clue.

If a slider, seat
mount, or bottom mount seat is bolted through the floorpan, a steel backing plate at least 4"x4" x 1/8" must be used for
each floorpan fastener. It is recommended that the backing plate be welded to the floorpan.

I still don't understand why we have to put up with arbitrary rulings like these. This one reeks almost as badly as the stock class passenger seat ruling and the money behind the GTC spec tire proclamations.

Van

What if sliders are not used? Then is it OK to bolt the seat directly to the factory M6 locations without extra reinforcement?

KaiB

Van, my read is: Without the use of a back brace (another topic altogether), yes the factory M6 locations will a) have to be modified to accept a M8 bolt(s) and b) reinforced (whatever the hell this means, as no engineering has been done, no analysis and no specifications presented).

MSR Racer

This is for 2015 correct? We don't need it for next year?

jdistefa

^ Yes, not needed for the coming 2014 season.

Kai, agree, frustrating. I would like some clarification on things before doing surgery on my car. I have a set of cup sliders but it's going to be a major PITA to fabricate new custom mounts.

Have looked at the Sabelt slider and for the life of me can't see any significant difference re. the Recaro sliders. I don't get it. Further I'm not sure if 8mm bolts (and their heads) will fit in Sabelt sliders?

I get reinforcing the floor pan but I would be doing that based on gut and home engineering, not with any specific analysis or expert guidance. The pan corner failure seen in 6-cups may or may not be relevant to my car.

Lastly, I wonder where this is coming from.... Have there been slider and/or mount failures that we simply haven't heard about? I'm using the Patrick Motorsport weld-in floor pan mounts (setup for 6mm bolts) and haven't heard of any failures there. I have everything out at the moment and can't see any weld cracks, pan failure, etc. Sigh.

My plan as it stands for this season is to proactively reinforce the floor pan/tunnel, use fresh 6mm bolts and switch to Sabelt sliders. I'm not going to do any new fabrication until I have a better understanding of what/why/how.

Van

OK, gotcha. So if a seat-back brace is used, then any sliders and any size bolts seem allowed.

sundog

Such a great rule. What grade of M8 bolt and nut? Because I can get a M6 that is stronger than an M8.

I really don't have a problem with rules that solve a problem, but this doesn't specify enough information to solve anything. It is at best a stab in the dark.

If somebody goes to Home Depot to get M8's to replace the factory or aftermarket M6 fasteners, it is likely that they will not be increasing the load capacity of the joint. The strengths can vary within a fastener size by an order of magnitude.

I hope somebody does a little more engineering analysis of this requirement.

KaiB

Dog, 8.8 grade bolts are specified. Beyond that, nothing is and somehow I doubt any analysis whatsoever was done on the reinforcement requirement.

I also doubt that any (real) analysis whatsoever was done on the basic NEED for the rules change.

The current rule allows me to hop into the barn, find a bit of steel, fire up the arc welder and have at it. Trust me, I farm, I weld....very badly...and all of this is now OK with the Rules guys.

911racer

We are still bolting this to a piece of fiberglass or carbon fiber. I think that is going to be the weak link in the fastening no matter what.

Ed

mglobe

When I look at the rules, it looks like for late model cars, you can only use the Cup sliders:

"For 996s and later 911s, 996
and later Cup or other factory
race cars, Boxsters, and Caymans,
the slider used on the
Porsche Cup cars
(996.521.929.00) or the similar
part used on the other specified
models when delivered
without a power seat slider."

KaiB

Or similar?

And the requisite mounts...which may then be MODIFIED. By whom, in what manner, where are the specifications?

This entire rule stinks of backyard, homegrown bull.

What on earth promulgated this? Which study, what analysis and if a racing incident (as has been speculated), which post-accident survey by which engineering firm.

I'm calling BS on the entire thing.

Mahler9th

As has been pointed out, these new rules only affect those whom elect not to use a seat back brace. I think the idea is that in those instances, there is less hardware holding the seat in place in case of a shunt.

Some folks believe that some FIA seats (within their specified dating) should not be used with seat back braces. This may include Porsche AG as I have never seen a seat back brace in a newly delivered water-cooled factory race car with an FIA seat.

I have taken a look at quite a few sliders including Recaro double lockers and Sparco/generic double lockers. And of course the newer Recaro pin-style units. I am pretty sure that Walt/PCA looked carefully at a variety of sliders. There are differences.

The Recaro pin-style units are very inexpensive and they needn't be purchased new nor from PMNA. But they are not a bolt-in replacement for many (most?) situations where existing double locking sliders are installed. Fab is required.

I don't race a lot with PCA but I have been in touch with Walt on this and I encourage everyone with interest to work within the PCA processes to learn more about these new rules and to work carefully with the PCA scrutineers.

KaiB

But here we go once again Scott (I do appreciate your efforts here, but...).

Yet again, we go into the shed to "modify", or in your terms "fab" a unit so it can be used in an application where it was not intended. The engineers who designed the sliders you mentiond, and the groups who tested them DID NOT test "modified" units, or "fabbed" mounts.

PCA (I read Walt here, a well known tinkerer) has determined that the CUP sliders are OK, and that the Sabelts also seem to pass muster, yet will allow "modifications", "altering" and "fabrication", to not only the sliders in question but also the mounts.

They also seem to want us to "reinforce" our cars...without any structural analysis, specifications or guidelines.

Stinks. All of this has been done for what reason?

Toby Pennycuff

Kai.... You just *HAD* to open this old wound of mine, didn't you!?! And here, I thought I had gotten past it! NOT!!!!!

KaiB

Sorry Toby, just had to.

But I haven't entered into the Spce tire fray.

Now, however, there is talk about ADDING weight to GT cars if they run slicks!!! This comes, of course, after the powers decided there is no difference btw. slicks and DOT tires.

HA!!!