Having looked closer at my lug nuts, it seems like despite having the right seat shape, the OEM lug nuts should not be used with these wheels.

Here is a close-up of one of my lug nuts:

https://i.imgur.com/tsOxzF4.jpg

It appears that at some point closer to the wider part of the conical seat in the wheel the OEM lug nuts are a bit too wide, so they started chipping (or is it the finish that's chipping?). Also, probably the hex part of the lug nut doesn't extend much, and you can easily damage the finish of the wheel with the socket. I see similar issues around other lug nuts, although not quite as bad.
Seems like spline-style lugs is the way to go.

It's disappointing that the shop I went to didn't catch that, despite me specifically asking them if my lug nuts are ok for these wheels.
Also, I didn't get a good advice on that when I reached out to Titan 7 directly weeks prior to installation.

I see.. Titan suggested I use aftermarket lugs as well.

Just installed Muteki 41885C Chrome 12mm x 1.25mm Closed End Spline Drive Lug Nuts - these look and sit much better!

On the photo with the stock lug nut you can see scratches from the socket -- I presume the lug nug was sitting so deep that the socket could only cover half of the length of the hex section. Yuck!

https://i.imgur.com/7ZdIdPJ.jpg
https://i.imgur.com/juHTCbk.jpg

Here is my car with T-S5 wheels...

https://i.imgur.com/iVoa2uz.jpg

Another data point:

I've put my 17x9 T-S5s with new 245/40R17 GT Radial SX2 and OEM TPMS sensors on my bathroom scales and measured 43.8 lbs.

For comparison the OEM PP wheels with medium-worn Michelin Primacy HP (stock) tires and no TPMS on the same scaled and measured 39.6 lbs.

So looks like at the end of the day a combo of 17x9 with 245/40 is still heavier than OEM PP wheels + OEM tires.

. Way more grip and better looking wheels :)

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The car looks great. I'm interested in the setup. I have the 2017 BRZ w/pp and the CSG Flex A coilovers. I'm currently running -2.5 chamber in front and -2.0 rear with the recommended height? About 1.3 lower than stock. Do you think the wheel and tire setup will fit?

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Yeah I think so. The reason why I'm higher than recommended is because I want a little more daily driveability :)

FTR, I recently went to a Car Control Clinic and noticed that when my car spins out of a drift the front tire does rub against the fender a bit, even though I'm maxed out on front camber. You may want to keep that in mind wrt your lower ride height.
Note that I've dropped 3 turns of the front coilovers (6mm?) since the last time I took photos, so I was at ~31mm drop from factory at that CCC.

Thanks for the info. Still on the fence.

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Absolutely love these wheels!

Now that they're track-proven, I've decided to share some more photos:

https://i.imgur.com/CVbopIC.jpg
https://i.imgur.com/Hho8u4T.jpg
https://i.imgur.com/U6QZWTQ.jpg
https://i.imgur.com/ZsFPqw1.jpg
https://i.imgur.com/0UriFRm.jpg
https://i.imgur.com/cmVRsyo.jpg

Sounds more like your particular combo is awful heavy. If your wheels come in at 15.8 lbs, then you have a 28 lb tire. There are a lot of tires that way MUCH less than this in that size. In fact, MOST tires of that size way much less than this, which comes to my surprise as to why these are so heavy? Maybe the performance in them stands out that much more? I would be surprised.

Now that you've mentioned -- yes, SX2s spec weight in that size is 26.2 lbs [1].
Still not clear where the extra 1.8 lbs come from; I don't think TPMS + center caps + balancing weights + dust and dirt would account for that.
Perhaps just an imprecision of my kitchen scales when used on an uneven pavement of my garage (I did try multiple locations though)...

Here's a quick table of weight SX2s vs Primacy HP in different sizes:

So yeah, apparently SX2s are so heavy that inertia-wise they outweigh the benefit of lightweight wheels. Still much faster laptimes though.

Perhaps when I'm ready for RE71Rs I can get well below 40 lbs for the wheel+tire combo :P
---
I couldn't easily find the weight of the OEM PP wheels without tires, but it used to be known to be ~22 lbs.

RE71R and yokos A052 are crazy light and have crazy grip. Be prepared to get a lot less durability out of them tho, probably 3 to 4 times less than the SX2.

Yup, I'm aware of the increased wear :) Thanks!