heinzboehmer's 2002 Topaz 6MT Coupe

[heinzboehmer]

Yeah all 3 are solid. I never gave this approach a thought (it's appealing) but might try that. I worry about different materials used in the front bushing vs the rear/cover. But maybe given the front bushing is mounted laterally, it doesn't matter.

Will need to think about it but I like this idea!

Yeah forces on the two sets of bushings would be orthogonal, so it should be fine (?).

I ran a rubber front bushing on my car and poly rear for threeish years (forgot to buy the rear diff bushings when I did my vincebar and then got lazy and put off swapping them). Had no issues with that combo in terms of accelerated wear or anything like that.

And, well, we all know that if you read something on the internet then it's a fact, so you should be good to go now!

[Casa de Mesa]

Are all three solid? The cover was much simpler than I expected to swap in place. Hour or two of work. It's been a while, but I think there was a significantly bigger decrease in diff noise when I swapped out the rear poly bushings for stock compared to when I swapped out the front poly bushing for stock.

Might be worth swapping out the rears sooner and getting to the front bushing next time the diff is out.

Yeah all 3 are solid. I never gave this approach a thought (it's appealing) but might try that. I worry about different materials used in the front bushing vs the rear/cover. But maybe given the front bushing is mounted laterally, it doesn't matter.

Will need to think about it but I like this idea!

[heinzboehmer]

Hey Heinz! Love the track photos! The car looks amazing, especially with the CSL lips.

What brake pads are you running? And are you running the same front to rear?

You could try a pad with less initial bite in the back, or a pad with more initial bite up front. My racecar doesn't have a brake bias valve due the type of ABS it has. Running a less aggressive pad (still a race pad, just less aggressive bite) in the rear might solve your issue if the bushings do not. I have always run different front and rear brake pads. It's not elegant, but it works.

Hey Bryan! Appreciate the compliments and tips, as always.

Running PFC08 pads all around. mrgizmo04 mentioned something similar to me when I complained about the instability under hard braking. He's running split compounds front to rear on his 996 calipers. I'll have to think about doing the same once I wear these pads out. Definitely less effort involved in buying a different compound than in swapping out the RTABs . Although I am due for an alignment soon...

Also I need to do the bushing swap in my car. Still have the solid aluminum ones... 😶

Are all three solid? The cover was much simpler than I expected to swap in place. Hour or two of work. It's been a while, but I think there was a significantly bigger decrease in diff noise when I swapped out the rear poly bushings for stock compared to when I swapped out the front poly bushing for stock.

Might be worth swapping out the rears sooner and getting to the front bushing next time the diff is out.

[Casa de Mesa]

Hey Heinz! Love the track photos! The car looks amazing, especially with the CSL lips.

What brake pads are you running? And are you running the same front to rear?

You could try a pad with less initial bite in the back, or a pad with more initial bite up front. My racecar doesn't have a brake bias valve due the type of ABS it has. Running a less aggressive pad (still a race pad, just less aggressive bite) in the rear might solve your issue if the bushings do not. I have always run different front and rear brake pads. It's not elegant, but it works.

Also I need to do the bushing swap in my car. Still have the solid aluminum ones... 😶

[heinzboehmer]

Quality posts! Topaz blue might be my favorite blue for E46.

Thanks! I've managed to catch it in some pretty good light recently

[Sprp85]

Quality posts! Topaz blue might be my favorite blue for E46.

[heinzboehmer]

Some more pics from the track day:




About to launch off the bypass:



Aaand landed:



This last one is probably my favorite pic of the day. Was chasing my friend in the S2K down while he had a passenger in the car. Passenger had zero track experience, don't think he had ever really been in a fast car on the street. Guess my chasing was a bit too much for him, as they had to pull into the pits (one turn after where the pic was taken) to let the dude puke lol. Fun times.

[heinzboehmer]

Been busy lately, so didn't have time to undo all the track stuff until recently.

Track day went great though. Cars feels amazing and is so much faster than me. Best lap was a 2:08 at Thunderhill East, which was 5 seconds faster than my previous best. Yeah it's not crazy fast, but I'm happy with it. Good friend of mine (who's a better driver) jumped into the car and put down a 2:07 first try with me in it. Clearly the car is capable of even faster laps.

The huge jump in time is partially due to all the changes to the car, but probably mostly due to the fact that I got an instructor for one of the sessions. Was great to have someone in there to point out all the bad habits I had developed. Felt so much more confident in my driving after that session and will definitely do it again if I get the chance.

The one complaint about the car I have is that it's a bit unstable under high speed braking. I changed too many variables to know for sure what caused it, but probable causes are the more rear biased 996 setup or my solid RTABs. I might swap the RTABs out for E89 rubber RTABs with limiters on the outside so that the car doesn't toe out under acceleration but does toe in under braking. It wasn't hugely unsettling though, so it's not a priority.

Anyway, grabbed a pic right before heading back home that I think turned out pretty good. That S2K is owned by that same friend who drove the M3 around:



First thing I did after the track day was to swap out the diff bushings. The slon wall acts as a speaker and made the poly bushing diff whine go from annoying to intolerable, especially after driving a total of 5ish hours on the highway.

I got some tools laser cut to press E36 bushings in without removing the diff. Basically just glorified washers and a thin wrench.



Started by removing the poly bushings, which wasn't too hard. Removed the aluminum insert with a big screw extractor and then just pushed the poly part out. Then used the different bolts to push the new bushing in. Was going great until the last mm or so. The E36 bushings are slightly shorter than the diff cover, so I made sure to make the press tool with a slightly smaller diameter to be able to get the bushing fully seated. Unfortunately, the press tool must have gone in crooked or something cause I heard a loud crack.

Sooo diff cover came out:





Bummer, but I was half expecting this to happen, so not too heartbroken. Brand new diff cover prepped and installed:





Opted for the liquid gasket instead of the paper because I wasn't confident that I would be able to get the diff side of the surface prepped well enough for that to not leak (since the diff case did not come out of the car). So far no leaks, but we'll see how it holds up to track abuse.

Since I had the diff cover off, I went in and measured backlash. I absolutely did not have the proper tool to do it with, but I managed to get a very repeatable measurement with my caliper. I stuck it to the diff with a magnet and used a wrench on the ring gear bolts to move things around:




I then used a similar technique to take backlash measurements of the spider gears through one of the cutouts in the carrier. This measurement was much less precise, but it told me what I needed to know. Here's what I measured:

Ring-pinion: 0.14 mm
Spider gears: 0.55 ± 0.03 mm

Note that the spider gear measurement is the lash between adjacent spider gears, so the total lash at the ring gear would be even more. Crazy how much play those things have. Left it alone for now, but something will need to be done about this diff in the future.


With the diff back together, I was able to do the rest of my track un-prep. Brake ducts removed, track pads swapped out and street wheels back on. The cause of my steering wheel vibration on the way back from the track became super obvious pretty quickly:




I always forget to do the aluminum tape after balancing the wheels. Will try my best to not forget before the next track day. Not a lot I can do about the rubber though

As a bonus post track surprise, I found a catastrophically failed front dust boot:



Hard to see in that picture, but it failed all the way around. Thing came out in two pieces. This was the only boot I found with a serious failure, but I did find a few others that were half melted. Replaced it with a girodisc boot for now and will likely replace the rest before the next track day. We'll see how those hold up.

Also, friend of mine recently bought a 3D scanner and said he'd be down to help me scan the car so I can design my V2 brake ducts. Those should help the boots last longer as well.

[heinzboehmer]

Obioban here's what the gap between the seats and the wall looks like:

[bigjae46]

Interesting! I hadn't thought of that. Appreciate you sharing.

Looks like 255/40R17 is right over 25" and I didn't feel the tires overheating too much today, but what you're saying makes total sense. I'll keep it in mind for my next set of tires. Looks like I might be messing around with the setup anyway.

A 275 on a 10” wheel can fit with about -3.0
camber and fender mods. The lip just needs to be rolled flat which is pretty easy. Just need to be careful at the forward edge and the backside of the arch - might need to make a small relief cut in those spots to flatten the lip. It’s worth it.

[heinzboehmer]

7.5mm is a scary amount of spacer. I'd bump that up to a hubcentric 10mm.
... I'm thinking after I install my rear bulkhead, I may just hit it with some spray adhesive and put a superleggera pad of some sort on it for good.

Edit:
Actually, how close does it sit to the seat backs when installed? If it's right up against them, I'll probably just leave it alone-- I don't care if it gets visually scuffed up, just don't want it getting broken by something flying around in the trunk. If it's right up against the seat backs, probably minimal danger of that...

Oh! I forgot a picture!



I installed hub extenders even with just the 5mm spacer, so no sketchiness here.

And the wall does not butt up against the seat at all. There's a couple inches between them. I'll grab a picture later. But yeah, that's exactly why I built this partition.

Because of the limited contact with centering lip? From reading the Core4 Motorsports wheel mounting stuff, it doesn’t seem like the centering lip actually has any role in holding the wheel on. They write that the wheel is held in place by friction between the actual mating surfaces and the friction is maintained by clamping force from the lugs. Centering lip is just for centering. Makes sense to me, but I’m also going the route of eliminating spacers altogether for my track setup to avoid thinking about it.

I really wanted to stay away from spacers too, but also wanted to stay away from much lower offsets than stock, which is why I went for the ET35 wheel. Had I known that a 5mm spacer wasn't going to work, I would probably have just gone for the ET25 wheel to keep them square.

Oh well, I might swap the front wheels out when the tires are dead.

I would recommend a tire OD of at least 25.5" and IIIRC a 255/40R17 is under 25" especially on higher speed tracks. A shorter OD results in a more RPMs for the tire at the same speed which adds a lot of heat into the tire. You run a much higher risk of overheating the tire which at best will force a cool down lap. I've found it causes the tire to wear out much quicker - in my case it was about 20% to 25% quicker. I essentially got one event less out of the tire.

I ran a 245/40R17 tire and they would get greasy after 4 laps. The gearing effect was nice.

Interesting! I hadn't thought of that. Appreciate you sharing.

Looks like 255/40R17 is right over 25" and I didn't feel the tires overheating too much today, but what you're saying makes total sense. I'll keep it in mind for my next set of tires. Looks like I might be messing around with the setup anyway.

[bigjae46]

I would recommend a tire OD of at least 25.5" and IIIRC a 255/40R17 is under 25" especially on higher speed tracks. A shorter OD results in a more RPMs for the tire at the same speed which adds a lot of heat into the tire. You run a much higher risk of overheating the tire which at best will force a cool down lap. I've found it causes the tire to wear out much quicker - in my case it was about 20% to 25% quicker. I essentially got one event less out of the tire.

I ran a 245/40R17 tire and they would get greasy after 4 laps. The gearing effect was nice.

[repoman89]

7.5mm is a scary amount of spacer. I'd bump that up to a hubcentric 10mm.

Because of the limited contact with centering lip? From reading the Core4 Motorsports wheel mounting stuff, it doesn’t seem like the centering lip actually has any role in holding the wheel on. They write that the wheel is held in place by friction between the actual mating surfaces and the friction is maintained by clamping force from the lugs. Centering lip is just for centering. Makes sense to me, but I’m also going the route of eliminating spacers altogether for my track setup to avoid thinking about it.

[Obioban]

7.5mm is a scary amount of spacer. I'd bump that up to a hubcentric 10mm.

... I'm thinking after I install my rear bulkhead, I may just hit it with some spray adhesive and put a superleggera pad of some sort on it for good.

Edit:
Actually, how close does it sit to the seat backs when installed? If it's right up against them, I'll probably just leave it alone-- I don't care if it gets visually scuffed up, just don't want it getting broken by something flying around in the trunk. If it's right up against the seat backs, probably minimal danger of that...

[heinzboehmer]

Track day tomorrow, so bunch of stuff got done this week.

First, I swapped the front bi xenon auto leveling sensor, as the original one cracked and the lever arm kept slipping out. Here's the old one:



New sensor and new lever arm installed:



Decided to swap out the lever arm as well because the control arm clip broke off a long time ago. Zip ties held up great though!



Unfortunately, the outside portion of the sensor connector crumbled when I went to reattach it, so I added some zip ties to keep it in place (visible above). Guess I just ended up swapping one set of zip ties for another.

Then I swapped out the turn signals, as the originals were falling apart.

Old:



(Note the deteriorated weather stripping and broken mounting tabs)

New:



Last came the new track wheels/tires and track pads. Wheels are ARC-8 in 17x9.5" ET35 up front and 17x10" ET25 in the rear. Tires are RE-71RS 255/40R-17 square. Yes, a bit of an unconventional setup with staggered wheels and squared tires, but I wanted to avoid spacers as much as possible.

I did quickly weigh this new setup vs my old track setup and it's significantly lighter. Should be fun on track. Here are the weights (per corner):

18" Style 67 RE-71R Front	48.7 lbs
17" ARC8 RE-71RS Front	43.6 lbs
18" Style 67 RE-71R Rear	53.7 lbs
17" ARC8 RE-71RS Rear	45.1 lbs

So total savings of 5.1 lbs per side up front and 8.6 lbs per side in the rear. Great!

Anyway, I knew I was going to need spacers to clear the front brakes, so I ordered a set of 5mm spacers. Here's what the clearance looked like with those:




It technically cleared, but there was <1mm between spoke and caliper, so I decided to step up to a 7.5 mm spacer.

Aah, muuuch better:




Here's what the car looks like dressed up in it's new track clothes:







And here's what the trunk looks like all packed up and with the partition in place. Even though the partition reduces trunk space a bit, everything still fits!