I don't know about reasonable, but I also started on track with a stock M240i. I think high 1:50s (emphasis on high) was about what I was doing too when I was starting out.
My second day ever on track I did 2:01 [1] at Laguna, a couple of weeks later -- 1:59 [2] with some terrible all-seasons. The best I've done with the car mostly stock (just camber plates to stop eating tires and KWs) was 1:56 [3]. That was on 7-8 track days of experience, I'm sure a better driver could've extracted quite a bit more from that setup.
Since then, I'm with a bit more experience (30ish track days) and the car's a bit further from stock (tires, diff, suspension, brakes, bushings). So far, I've gotten 1:46-high out of it [4]. The M235ir-s get 1:37-1:41 on slicks, so there's still quite a bit to go.
Last weekend at Laguna must've been SpeedSF, no? I had to miss it this time because the car's out getting a cage built, but say hi at the next one. I'm the blue M240 with orange numbers.
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