I've got 16mm of spacers on mine...
I've got 16mm of spacers on mine...
Well I've neglected this thread again, time for an update.
After this season I decided that the stock PASM suspension just wasn't cutting it. The active system is nice on the street but if anything gets in the way when approaching the limit of grip. A few months ago I bought a used DSC shock controller to give that a try. It was an improvement but still just not what I was looking for and required more tinkering than I wanted. I debated a few options and then found a used set of ohlins road & track coilovers for a price that I couldn't pass up. I wasn't sold on the super high front spring rate, but I rode in a friend's car with the same setup and it seemed to work well.
But first...I finally made it back out on track at the end of the season at nelson ledges. Other than being incredibly cold and the tires clearly starting to age out, the day was fun and uneventful. Swapping the track pads on went fine, but when I went to put the street pads back in I noticed that one of the caliper stud nuts wasn't quite as tight as the others when removing the caliper. Then when reinstalling that caliper, that stud/nut wouldn't take torque. Well, I know what that means...
There's your problem:
The threads were pulling out of the aluminum knuckle. In truth this is all my fault. When I originally installed these studs I didn't quite take the process of cleaning out the threads before installation seriously enough (the holes are open to the environment on the bottom end and the studs thread in further than the stock bolts) and that stud seized not quite fully installed. I made it work and it held up for two years and probably 10-12 torque cycles, but the reduced thread area finally gave out.
I contemplated trying to repair the threads with an insert, but ebay provided me with a whole replacement knuckle from an 11k mile 911 for not much more than the thread inset kit would have cost. That plus a new stud kit was an annoying but ultimately fairly cheap fix, with the added bonus of a basically brand new wheel bearing. All in all this was the best time for this to happen since I'm about to pull the suspension apart anyway.
New knuckle, with new studs installed. The slight irony was that, having learned my lesson about cleaning up the threads well, the threads on this knuckle were so nice that the thread chaser threaded through by hand with zero resistance.
With coilovers and a new knuckle sitting around, I had the opportunity to do some...unconventional wheel/tire fitment checks.
Ohlins did one of my least favorite things and came up with an aftermarket suspension setup with less clearance than OEM. To be fair the OEM clearance is very good and I guess ohlins wasn't intending these to be used with 18" wheels, but there's still an easy 10-15mm of dead space in the spring seat and the spring is longer than it needs to be. This is with 3mm more spacer than I run with these wheels on the stock suspension, and less clearance if anything.
Well, let's see if I can do something about that. I switched to shorter springs and also went down a step in rate which both made me a bit happier with the setup and meant more preload would be needed, moving the spring seat further up on the strut. Then I cut down the upper spring seat as much as I felt comfortable with, which also involved trimming the lip on the stock strut bearing to clear.
Before and after:
Between the shorter springs and modified upper seats, plus running slightly less lowering than the default setting (which was always the plan) the spring seat moved around 2" up the strut body and completely out of range of wheel contact. This is back to the normal amount of spacer, and the tires I'm planning on running in the future (RE71RS) run a bit narrower so there should be sufficient clearance. Not ideal but a big improvement.
So time to start installing, and do some wheel/tire fitment checking along the way. Since the left front was getting the knuckle replaced too I started there and did it the "hard way" of totally disassembling the suspension. That turned out to be an awful process. There was some magic in the control arm installation where everything went back together fairly easily that was missing here, I guess because of the significantly reduced droop travel of the coilovers. Eventually I ended up using a ratchet strap from the control arm to the chassis to load up the inner control arm bushing enough to make the holes align, and finally everything went back together.
The other front was much easier, when you don't need to remove the knuckle there's enough space to sneak the strut out of the fender opening by just loosening the inner control arm bolt to allow a bit of extra range of motion. And of coure the much shorter coilover goes in pretty easily.
Onto the rear, where the internet provided me with the "easy" method, the alternative being fully disassembling the whole corner including the axle and brakes...no thanks. There's not much preload to the stock springs which allows you to applly a spring compressor, slip the lower end of the spring out of the seat, and then thread it down the strut body allowing for enough clearance to slip the strut up onto the hole in the body and then out of the car.
Installation of the coilover is kind of the reverse process. Thread the adjuster way down to get the spring out of the way, insert the upper end through the hole in the body, then into the knuckle. Again the ratchet strap came in handy, this time to compress the strut while slipping the strut mount up into place. The first one was a bit rough including accidentally installing the upper spring seat parts in the wrong order at first, but with those lessons learned the second side went together quickly and easily.
Okay so how about those tire clearances? This was mostly out of curiosity as, having run them for two years, I knew that these tires cleared on the much softer stock suspension, just not by how much. Here's the front, it's hard to show but these are all taken with the tire just barely not touching the fender.
Wheels straight ahead is the worst, with the front of the tire peeking out of the fender:
But as soon as the wheels start turning, things get better:
It's a little hard to measure but these should all be pretty solidly beyond what the suspension travel will allow.
The rear is a bit harder because I'm planning to downsize from the current 19" wheels to 18s, so I don't have a great representation to check with. The real concern is wheel clearance to the toe arm and possibly to the lower control arm when the suspension compresses. The front wheel with no spacer is within a few mm of the backspacing of the correct wheel, so it's a decent reference:
Again that should be beyond the possible travel so the control arm clearance should be fine. The toe link clearance is a bit tough to judge because it depends on the exact shape and thickness of the inner wheel lip. My plan is to go a bit aggressive with wheel offset and be prepared to run a small spacer if needed.
And I tossed on the 19" wheel/tire, which is both taller and wider than the tire I plan to run, to check fender clearance. No problems there:
Okay, final setup time. One of the things I learned from this process is just how hard it is to find a relatively flat and level car sized piece of concrete. Knowing that my garage floor isn't flat, I took measurements of each fender height on the stock suspension as reference points. They were pretty uneven, especially the fronts, but I just went with it and aimed for reproducing those heights with the offset of the ~1/4" of lowering I was aiming for.
After that was all done, I took it to work where I have access to a set of scales. After spending quite a bit of time managing to set them up flat and level, I lowered the car onto the scales and found that my initial setup was basically dead on. This is with ~180lb (a bit light for me but it was all the ballast I could come up with easily) in the drivers seat:
I forgot to take the photo but if you do the math that works out to 49.6% cross weight. I worked it out that the correction to make it perfect was about half a millimeter height change on one of the rears....that's more than close enough for me. I did miss a bit on the rake, the rear was higher than I wanted and the front just a touch too low, but that's an easy change to make that doesn't require scaling the car so I just set the front swaybar endlinks and packed it up to make the rake change at home.
And for reference this is the weight with no driver, with basically a full tank of fuel:
Made that final ride height change did a torque check of everything after diving it for a few miles, then went out and washed the car to take a nice photo of the new ride height.
My initial impression is that these things are pretty nice. The ride quality with essentially doubled spring rates is a bit worse, but at least as good as I was hoping for and definitely not unbearable. Handling is a bit hard to judge on all seasons in 40* weather but the car seems more predictable and planted than it used to.
Ended up being busy this week and forgot to post, but some fun stuff has shown up in the last couple of weeks...and now I'm poor for a while.
Wheels test installed on the car:
Back when I ordered these wheels I did some fitment checks and a lot of measuring and math with the wheels I had available, but every wheel is slightly different. Considering I'm trying to run a pretty aggressive setup I wanted to maximize the offset and went a bit aggressive, I'd rahter have to run a few mm of spacer than end up with extra inner clearance. So I figured out what offsets I was confident would work and then added 2mm to them. So how did that go? Up front there's no wheel clearance issues, only tire, so that'll have to wait until I get around to mounting the tires. But the rear limit is wheel clearance to the toe link, which I can check now.
Turns out, better than expected. This is with no spacer and it's right where I hoped it would be. It's hard to photograph well but the toe link is tucked within the step of the wheel lip slightly, with 3-4mm clearance axially and just under 3mm radially which hopefully should be plenty.
Oh and these also appeared about the same time...I had convinced myself to wait until next winter but these came up for sale for a price that was too good to pass up. Now I need to decide if I'm going to install them now or wait until I can afford the tune that should go with them.
I finally took care of a small project I've been wanting to do. I generally like these seats but the combination of their limited adjsutability and my slightly long legs mean that the seat base is too flat and it's a struggle to stay upright while driving hard, especially on track with heavy braking. The extra lap belt I added last year helped but still wasn't great. I tried but couldn't quite convince myself to replace the seats with something better, but I figured out that since the seat base pivots/raises mechanically (in a way that's not useful for what I want to do) it attaches to each slider at a single point front and rear. That means it should be pretty easy to raise the front pivot point to lift the front of the seat up to a better spot.
After a lot of measuring and some CAD work, these arrived in the mail. I got a few different heights so I could experiment if needed
Step one: extract the sliders from the seat. This was surprisingly easy, with the slight complication that the last idiot that removed the seat (hey...that's me) used a normal hex socket instead of the proper e-torx on the seat bolts so the heads were a bit chewed up.
Unmodified slider:
Drill an extra hole in the slider bracket for extra support of the add on tab, paint and install the tab, and the finished product:
And reinstall it all. The mount points are wider now, but there seems to be enough compliant in everything taht it went back together without binding anything up. The seat base angle before:
And after:
In photos both configurations look fairly steep, but the new setup feels much better. This is with the shortest brackets (~1" lift) which was definitely the right choice. I actually wouldn't mind a little less lift, but it can't go much lower without interfering with the original slider mount and I don't want to make any irreversible modifications to anything.
Intermittent nice weather means a semi-local test and tune event this weekend, which means it ws time to mount the tires and install on the car. The front needed 3mm of spacer for reasonable tire clearance which is about what I expected.
Still looks just as gorgeous. Actually even better now with those matte bronze wheels! :)
Well the first event of the season is over, which makes this the perfect time to tear the car apart for clutch replacement and header install...right?
Step 1: spend the winter slowly accumulating all the parts you need so that it doesn't seem quite so expensive.
This isn't the first 981 clutch job I've been involved with (and unfortunately won't be the last either) so I know more or less what to expect. The last one was on a texas car with <40k miles, this one is on a car that started life in new england and is approaching 90k miles so there might be some surprises along the way.
Getting everything unbolted and the transmission out was surprisingly uneventful other than having to relive the experience that the transmission doesn't really quite fit out through the provided opening between trunk floor and subframe cross brace nicely. But it's out.
Having access to a lift and transmission jack makes this infinitely easier than when I did this job on my 986 boxster on the floor with a floor jack.
As expected the clutch, flywheel, and pressure plate have seen some things. It's hard to photo but the PP surface looks like a brake rotor that's ready for replacement, complete with a few grooves. And of course quite a few hot spots.
And...uh...I'm pretty sure dual mass flywheels aren't supposed to move on this axis
As somewhat expected the project has scope creeped a bit with some "while I'm in there" stuff - rear main seal replacement, repainting the crossmember that's starting to get rusty while access to it is better, and some other hardware and seals that I didn't think about when first ordering parts.
As expected this has dragged on between add-on projects and things taking longer than expected. I tried to avoid replacing the rear main seal but gave in and decided it was the right thing to do. Removal went...well it went.
This week I 3D printed an installation tool since of course the new seal needs to be set at a specific depth rather than just bottomed out into the channel.
...and then promptly found out that I didn't leave enough clearance for the flywheel dowel pin and had to hack it up some. Ugly, but it worked and the seal seems to be seated well.
And got the shiny new flywheel installed and am finally on the path to actually putting things back together.
Some side projects...rear crossmember rust treatment and paint. I'm annoyed at how rusty this was but I guess overall I should be happy with porsche's rust prevention. For a car with almost 90k miles that spent the first few years of its life in new england being driven year round and has seen salt a few times during my ownership, only two bolts in this whole project were slightly troublesome and they were exhaust bolts which doesn't really count since that stuff always rusts.
This was a *very* interesting place to find rust though...inside the vacuum solenoid for the valve that controls coolant flow to the trans cooler.
After a long weekend of work, it lives! Of course it's still not quite finished. The cooling system needs to be bled but it at least was able to run long enough to verify that the clutch works and the headers sound amazing.
Final step: run a coolant bleed cycle, hope the level is okay afterwards, then drive it home.
And home, looking shiny thanks to a 40 minute drive through intermittent heavy rain, and with a reminder to check the coolant before driving again
I've been driving it as much as I can to get the clutch broken in (and just enjoy the car) despite the terrible weather. I'm really happy with all of the changes. I'm not sure I ever listed the details so here they are:
-replacement flywheel, GT4 clutch kit: unsurprisingly the clutch pedal now feels exactly like a GT4 (which is a good thing). As best I can tell the clutch disk is the same as stock but the pressure plate definitely has a bit extra clamping force than the original. As a bonus the GT4 kit was actually cheaper than the stock replacement.
-Rennline trans mounts: assembly of these was awful but they seem to work well. A bit more low rpm NVH than I was hoping for but very tolerable and the drivetrain definitely feels more controlled. Some of the extra noise transmitted through the chassis is actually nice, it gives it a bit of the sound/feel of a classic porsche.
-Cargraphic headers with high flow cats: a huge pain to install but they sound good while not being incredibly loud, the cats work well enough to not make any bad smells or cause a CEL, and the low-mid range torque isn't life changing but is definitely an improvement. Eventually I'll get around to getting a tune which should really wake it up.
I also replaced the M1 delvac gear oil (it was also 3-4 years old and probably about ready for replacement anyway) for some redline 75w90NS. So far that's an improvement as well. The delvac was on the thick side for cold weather operation, this stuff seems a lot better and the high temp viscosity should be about the same.
At least on the 996's, the lore is Porsche or Delvac in the transmission ONLY. Under the threat of the 4 Horseman coming to knock on your door...
I found a ton of mixed reviews on what works and (mostly) what doesn't work in my 986. I ended up going OE for fluid and it's... fine. I've put redline in everything else I've worked on and been very happy. Curious to see how it works for you.
Yeah everyone has their own opinions and they all conflict, kind of like brake pads, brake fluid, oil.... It's worth noting that I believe this is a pretty substantially different transmission than the earlier cars. The delvac was *fine*. I chose it originally because everyone raved about the high temp performance. Which did seem good but the penalty was the driving below about 50* ambient felt like every shift was ripping the teeth off of the synchros until everything warmed up. The "on paper" specs of the delvac aren't overwhelming - the viscosity index is fairly low which is why it needs to be syrup at low temps to achieve good high temp performance. I did this research a while ago and don't remember the numbers but the redline has a higher VI so the high temp viscosity is very close to the delvac but the low temp viscosity is much better. So far it's been good, but like I said some of that is probably just from the oil being fresh. The only direct experience I've had with "bad" gear oil was in my friend's 997 GT3 and it was apparently very immediately obvious that it wasn't right. So given that it's done ~100 miles and is still fine I don't forsee any major issues.
Had an event with the new headers. As expected the power/torque difference is pretty minimal until I get around to getting a tune for it but man, does it sound good. No issues revealed other than a minor leak somewhere in the system as everything settles in. Should be as simple as cranking the clamps down a bit more.
Now that the car has a bit more runtime and has seen some higher speeds and warmer conditions, it's time to evaluate the wheel fitment.
Front: just the tiniest bit of tire rub on the spring seat and spring, not worth doing anything about
Rear: in some load condition that happened in this event but not the first one, the inner edge of the inside lip of the wheel just barely makes contact with the toe link. I'm probably going to toss 1-2mm of spacer on it just to be safe and since I was expecting to have to do that originally anyway.
All in all I'd say that's a pretty good precision fitment!
Also after probably almost 1000 street miles and around 20 autocross runs none of the spring seats have moved which was good to see.
You'll need to log in to post.
