Karter16's Silbergrau E46 M3 Journal

[karter16]

Hmm, they definitely do. Have a set on my car right now

So this is the thing - I can't find them anywhere. So I don't know if they've stopped making them? There not listed as a size on Michelin's website (either their NZ one or USA) likewise every tire supplier I check doesn't have that size listed. If you have a source I'd be very interested.

Edit: I obviously didn’t look hard enough last night and someone else has sent me a tire rack link with 235/40R18. Thanks for this!


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[karter16]

Unconventional suggestion: run 18x9 et42 245/40/18 front with 18x9.5 255/40/18 rear

Interesting - This wasn't one of the options I looked at last night. Thanks for this. I hadn't really thought to go wider than an 18x8.5 up front but willtheyfit shows the end result from a circumference perspective is very close. If you're suggesting it you presumably thing that the bit of extra rubber up front would be an improvement in handling? ( I'm not an expert at all in this space so very happy to take your advice)

[heinzboehmer]

Yep, tire rack has them, as do a bunch of other vendors in the US. Maybe just not as readily available in NZ.

I hope they start discontinuing them soon, I'm excited to try the new PSS5, but so far they have only released them in R20 and R21.

Edit: Wait! They actually do have them in R18 now, amazing: https://www.michelinman.com/auto/tir...-pilot-sport-5

Sizes are still a bit limited, but that should improve as time goes on. Now I'm excited for my next set of tires.

Maybe look for those instead of PS4Ss.

Edit 2: Nope, those are PS5 not PSS5. Damn. I have to say, their new naming scheme is confusing.

[Bry5on]

Interesting - This wasn't one of the options I looked at last night. Thanks for this. I hadn't really thought to go wider than an 18x8.5 up front but willtheyfit shows the end result from a circumference perspective is very close. If you're suggesting it you presumably thing that the bit of extra rubber up front would be an improvement in handling? ( I'm not an expert at all in this space so very happy to take your advice)

I think offset is most important, then rim width, then tire width. You can run a pretty good offset with a 9” wide wheel which means a 245 tire. I run 17x9 et45 with 245/40/17 and I find it’s really nice, doesn’t give up anything over a narrower tire by my hand. I think either way you’ll be happy, but personally I prefer a little closer to square for a tire with 50/50 weight distribution. If I had an M3, I’d probably be running either that setup, or an 18x9.5 et41 front with a 255/40/18 square. But there are no wheels in that spec, so 245

[karter16]

I think offset is most important, then rim width, then tire width. You can run a pretty good offset with a 9” wide wheel which means a 245 tire. I run 17x9 et45 with 245/40/17 and I find it’s really nice, doesn’t give up anything over a narrower tire by my hand. I think either way you’ll be happy, but personally I prefer a little closer to square for a tire with 50/50 weight distribution. If I had an M3, I’d probably be running either that setup, or an 18x9.5 et41 front with a 255/40/18 square. But there are no wheels in that spec, so 245

Awesome thank you so much for this - I really appreciate the guidance. This seems like the perfect option for me!

[karter16]

Well I placed the order with Apex last night. I've taken Bry5on 's advice and gone with 18x9 up front (245/40) and 18x9.5 (255/40) at the back, which gets closer to square, while also getting me a good offset (ET42) at the front. Why not go fully square? Firstly, I don't drive the car enough km's for it to really matter from a tyre wear perspective - these new tyres will likely go the way of the old ones before I wear them out. Secondly it means I don't have to worry about spacers on the rear wheels like I would really need to if I went square to suit the fronts. In NZ wheel spacers automatically mean you need a low volume vehicle cert which, as previously covered, I am intending to avoid.

I used willtheyfit.com (thanks George Hill!) to compare this setup with the various stock M3/CSL setups, and got a little concerned about how close the edge of the tyre tread will end up to the front spring perch on the Koni's. As has been identified by others the shape of the perch on the front right strut lends itself to running slightly closer to the tyre, and it's very close indeed. Although the new setup is a few mm shorter it's also closer to the strut and I was concerned it might be too close. When I compared the measurements against my car I couldn't see how it was going to work. Then when running the comparison for the 3rd time I realised I had made the amateur mistake of relying on a (top-google-ranked) post on another forum where that person had misquoted the offset on the 19in Style 67's. With the correct offset keyed in I was then satisfied that the new wheels should be an appropriate fit.

The wheels are coming UPS expedited, so will likely be the usual case of arriving in New Zealand in a week or so and then spending the next week sitting in the distribution centre in Takanini. I'll get some quotes for tires this week so that they're ready to go when the wheels get here.

Thanks everyone for your thoughts and advice on this, suddenly urgent, project!

[George Hill]

I run 255 on 9" et42 wheels on a lot of swaps, no issues with strut clearance and Konis so your 245 should have miles of clearance.

[karter16]

Well it's been an exciting weekend.

On Thursday I got stuck into the additional CAN message project. As a recap the idea here is to add an additional function into the 0401 program binary to send an additional CAN message.

I've given the new message the ARBID of 0x7D0 which makes it lower priority than all other CAN messages. The format of the message is:




There's basically 4 parts to achieving this:

1: Create a new function that replicates the existing function to send CAN messages from the DME. It needs to be recreated as we need space for the extra instructions to call an additional CAN message.
2: Modify the 10ms task to point to our new function instead of the original.
3: Load our new CAN message definition into the CAN config table in the program ROM.
4: Create a new function to assemble the new CAN message and push the frame to the CAN buffer.

The fun part is that this needs to be done by modifying the machine code in the binary, no easy way to write assembly or C here!

I got the above done on Thursday, spent code-checking it and then flashed it to my car on Saturday morning. As soon as I turned the ignition on I could tell something was wrong as the DSC light was flashing. All modules relying on outbound CAN were throwing errors. A review of what I'd done revealed a dumb mistake. I was trying to use slot 17 of a 15 slot buffer 🤦♂️. Anyway it was an easy fix and v1.1 ran without issue, and I connected to the MK60 with INPA and could view live CAN data, so I knew the standard CAN messages were working fine.

I'm not actually set up for CAN logging so at this point I shipped the binary off to Bryson for further testing.

I was very excited to get this back from him showing the new message being logged:



Bryson then setup his logger with the appropriate conversion factors and has been able to log AQ_REL, Lambda Integrator, etc. at 100Hz instead of the 5Hz or so that you get over DS2. He's posted a link to the log which you can find in his post here

I'm super stoked that this has worked out. In addition to being very useful for tuning, it also proves that these sorts of modifications are possible and that the disassembly work is good enough to understand what's going on to the degree that it's possible to make working changes and additions to the program.

Also - the new wheels are in the country and should hopefully arrive end of next week. Tomorrow's job is sorting out tires.

[Bry5on]

You’re the man!

[karter16]

Couple of updates:

1: The wheels arrived today 🎉 Mandatory photo, although we all already know what ARC8's look like 🙃




2: The male MAF sensor connectors arrived. I don't actually have need of these for myself, but I finally came across them and thought I'd order some to confirm they're a match and if so share the details with everyone as saves having to pay Turner money for their relocation harnesses.

These things appear to be the exact same item Turner are using and they come with the pins and seals.

I ordered 5 of these for the princely sum of $9.58USD total including shipping. per-unit price is $1.24USD.





You can purchase your own (you can order singles) here: https://www.hdconnectorstore.com/productdetail/32496.html

[karter16]

I ordered tires this evening. After much research I decided to go with the Bridgestone Potenza Sport. I had been planning to take the well-trod route of Michelin PS4S's, however they're not available in New Zealand (and importing tires was just going to be too expensive to make sense) in any of the sizes remotely close to what I need (I confirmed this with Michelin NZ directly), this was a surprise especially given I'd checked on their NZ website that those sizes were available here 👎

This meant I then needed to figure out alternative options. In Michelins that meant PSS's or PS5's (no Cup options available in NZ in the sizes I need). The PSS's are too old, and the PS5's while by all accounts very good had me a bit concerned about the softer tire wall than the PS4S. The RE050A's that I'm running currently, are fairly stiff in the sidewall department and while objectively terrible compared to modern options I am used to the stiffer sidewall. By moving to 18's I'm already introducing more compliance for a better ride and road stickability (that's the technical term 🙃), and I was a little concerned about also moving to an even softer sidewall as well.

I then looked wider, and after a bunch of research, looking at what is available in NZ, settled on the Potenza Sport. The Potenza Race would be an even better option I think, but they're not available in 18in options. The RE71-RS's while the stickiness would have been giggle-worthy, don't give the same degree of feedback and would be impractical in wet conditions, so the Sport it is. TireReviews.com have a good review of it and on dry handling it's very close to the PS4S, slightly better in the wet, and ranks worse on comfort (due to the firmer sidewall), slightly worse on noise and worse on wear. The wear doesn't bother me as I won't do enough km's anyway, the firmer sidewall I'm okay with and the noise will still be a lot better than the RE050A's anyway.

This is all splitting hairs of course, but might as well get the best option I can.


Big shout out to a member of the NZ BMW forum for suggesting Costco. Bridgestone NZ direct have the best price out of the rest due to a special deal currently which comes to only $2376.32 NZD for all 4 tires fitted. Costco, for exactly the same thing, is $1379.94, plus in addition you get a $360 store credit as well. Given we regularly shop at Costco for essentials this means the end cost for the tires comes to $1020. Which is quite astonishing to me. That's significantly less than I paid for new performance tires for my 318i in 2007!