Help sorting these caliper and suspension bolts

Jameel · 05:07 PM

Got my plating back today (full suspension and brake restoration on my 83 SC) and I've run into an identification problem.

I've got two groups of M12 bolts. One group is 35mm long (red brackets) These are the bolts for the front calipers and the bolts for the spring plate to trailing arm. These bolts are spec'd at 35mm long in the PET for both the calipers and the plates.

The other group (green brackets) is also M12, but only 30mm long. I have these labelled as rear caliper bolts. The PET shows these as 35mm.

The PET also shows the front calipers as using "spring washers" but I seem to have taken off split lock washers (PET calls these lock rings) and the PET shows the rears as having lock rings, but I seem to have taken off spring washers. If someone screwed these up in the past, they were at least consistent. All the fasteners were consistent left / right.

The other issue is, I have both 10.9 and 8.8 M12x35 bolts. I'm guessing that the 10.9's go on the trailing arm, since the shorter 30mm M12's I have labelled for the rear calipers are 8.8.

So the questions.

1. Should I put the washers back as I took them off the car, or follow the PET and switch them around?
2. Should I replace my rear 30mm bolts and use 35mm as per the PET? I have not checked the calipers yet to see if there's even room for the extra 5mm bolt length.
3. Where do the 10.9 bolts go, calipers or trailing arms?

Slanski62 · 01-27-2018, 06:52 PM

Depending on where exactly the bolt is used, you should be able to use a 35mm bolt in place of a 30mm, especially if you use a split washer. The split washers are thicker than spring washers but serve the same purpose. I believe euro cars use spring washers, whereas in the US we tend to use split washers. Also, I think you can use the stronger 10.9 anywhere you'd use an 8.8 bolt.

Pazuzu · 01-29-2018, 08:22 AM

I just had my front caliper off, so I measured.

I cannot guarantee that these are factory, but I know that in the 11 years I've drive the car, these were the bolts that came with it...

Front calipers, the 4 bolts were 30mm with spring washers. Which is different that your front calipers.

Those bolts go into through holes, you should be able to check that there is a slight bit of bolt tip exposure after they are torqued down, I assume that as long as the bolt tip sticks out a millimeter or so, and doesn't get close to the rotor, then they will be fine no matter what the length is.

Pazuzu · 01-29-2018, 08:25 AM

Quote:

Originally Posted by Slanski62

Also, I think you can use the stronger 10.9 anywhere you'd use an 8.8 bolt.

Thew 10.9 will be stronger in one direction, and weaker in another. The more hardened bolt will be stronger along it's length (clamping something to something else, like the trailing arm to the spring plate), but in this case, the forces are lateral (the brake caliper is trying to be twisted off the hub by the rotor), so 10.9 bolts will be WEAKER than the 8.8.

Pazuzu · 01-29-2018, 08:26 AM

Quote:

Originally Posted by Jameel

Got my plating back today (full suspension and brake restoration on my 83 SC)

Oh, and where did you get this done? Inquiring minds want to know

Jameel · 01-30-2018, 05:33 PM

Thanks fellas. Great info on the bolt grades too. Didn't know that.

I took a closer look at the PET (which still isn't consistent with what I took off the car) and did some trial fitting. I've concluded that I mislabeled my plating legend, swapping fronts for the rears. The rears need longer bolts, and the 30mm I have fit the fronts fine.

I had these plated by the local shop that does my company's day to day plating. They do automotive stuff on the side, so the turnaround is lengthy. I waited 6 weeks for this stuff and they pushed it through. I would imagine Houston has several zinc electroplating operations. If not, try Shaun at Tru6. Beautiful work.

911tracker85 · 01-31-2018, 12:05 PM

I have bagged/labelled all the parts I took off my project, now have it down to the tub. so lots of little bags with a few parts each.

I would love to have all my hardware replated, but daunted by the idea of dumping a lot of parts in a box and being able to sort them out later. maybe in small batches.

interesting comments about the different bolt strengths.

Jameel · 01-31-2018, 02:25 PM

Bob, I've always wondered the same thing. Here's what's worked for me. I bag groups of fasteners as I dismantle, with clear labels on the bag, and notes if necessary. Then I treat these bags as individual units when I go to the parts washer and bead blaster. One bag at a time. I only blast what I'm going to plate. Replacement parts like washers and lock nuts I only clean so when I photograph it doesn't make a mess. After they come out of bead blast I lay them all out on a clean white butcher sheet, measure them if necessary (big obvious stuff just gets labelled) and write those numbers right on the sheet. Take a cell phone pic. Sometimes two or three from lower angles so you can see the thickness of things like short nuts or thick washer. I sometimes take a video too which is handy for referencing perspective later. I organize all these pics into a folder on Google drive (see my engine legend here https://goo.gl/photos/jHaYNW5RhZzYfENr8) then I can refer back right on my phone when they come back from the platers. The plating shop is going to dump them all into one basket, so no sense in delivering labelled bags to them. It's a tedious job to sort the fasteners after plating, but with the legend it makes it a doable, if annoying task. Just seeing bags of golden fresh fasteners usually makes the first couple hours fun. After that it's just tedium. My experience anyway. I would love to know if there's a better method.

911tracker85 · 02-01-2018, 06:41 AM

Jameel,
thanks. since I am tearing this beast down to the tub for full, glass-out repaint, would love to have any visible bolts/parts replated. your suggestions are what I was suspecting I would have to do.

KTL · 02-01-2018, 07:44 AM

If you have the handy little Porsche pocket spec books, they give you the thread dimensions, material strength and the torque specs. These are like a condensed quick reference guide of the factory repair manuals.

The 10.9 bolts are definitely for the spring plates. They have typical witness marks on them where the passage through the plate and trailing arm flattens the threads close to the head. These bolts have deformed thread lock nuts and if they've been removed on a few occasions, they lose a lot of their locking effect on the bolt threads. So it's a good idea to replace these lock nuts.

I'd take a look at the wave washers and see how much wave they still have. They're not all that critical, as the torque on the fasteners is pretty high to keep them tight- 70 Nm=52 lb-ft. But if you're refreshing the suspension, might as well install new functional wave washers?

The spring plates also have some serrated cup lock washers (called Schnoor belleville disc spring washers) on the alignment eccentric bolts that should be replaced because the serrations get wiped smooth if they've been tightened and loosened several times.

Jameel · 02-01-2018, 08:24 AM

Oh that is so sweet Kevin. GREAT info and pics! I just got a tech specs booklet like two days ago, so I'll be using it more in the future. The list of fasteners is pure gold. Way easier than rifling through the PET. Awesome.

I've got a good selection of new wave and schnoor washers here that I'm putting on.