The McLaren 570S GT4 and the entire TCR field has undergone what’s essentially been a Balance of Performance reset ahead of this weekend’s IMSA Michelin Pilot Challenge round at Mid-Ohio.

Confirmed by IMSA in a bulletin issued late last week, the McLaren GT4 will race based on SRO Motorsports Group’s newly-confirmed BoP for the 2019-spec model.

It includes a 35 kg weight break, reduction in fuel capacity and a move to the recently homologated ECU.

Previously, the car, which won the season-opening round at Daytona International Speedway, had been running the SRO-homologated ECU from 2016, which is understood to have provided more top-end power.

SRO’s BoP serves as the baseline for the entire GS class in Pilot Challenge, although IMSA reserves the right to make adjustments.

A similar global BoP update, meanwhile, has impacted the entire TCR class, following the release of TCR International’s 2019 BoP for the touring car class.

It sees weight adjustments for all five eligible models, as well as engine map adjustments.

The Volkswagen GTI TCR is the hardest hit with a 30 kg increase, with the Audi RS 3 LMS TCR getting 20 kg of additional weight, 15 kg to the new-for-2019 Hyundai Veloster N TCR and 10 kg added to the Honda Civic Type-R TCR.

The only car to receive a weight break is the Alfa Romeo Giuletta TCR, which will shed 20 kg for Mid-Ohio.

WSC, the regulators of the global platform, confirmed the changes on Friday.

37 Entries for Mid-Ohio

Pilot Challenge resumes this weekend at Mid-Ohio after a seven-week break since the second round of the season at Sebring, with 37 cars on the entry list.

It includes the No. 82 BimmerWorld BMW M4 GT4 of Devin Jones and James Clay, who took over the GS class championship lead following their runner-up finish at Sebring.

Shelby Blackstock and Tom O’Gorman, meanwhile, lead the way in TCR, following back-to-back wins to star the season in their LA Honda World Racing Honda TCR entry.

Track action gets underway on Friday, with the two-hour Mid-Ohio 120 taking the green flag Saturday at 1:45 p.m. EDT, with live coverage on IMSA.tv.