IMSA releases final Rolex 24 GTLM and GTD BoP adjustments

IMSA releases final Rolex 24 GTLM and GTD BoP adjustments

IMSA

IMSA releases final Rolex 24 GTLM and GTD BoP adjustments

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 All photos: Marshall Pruett

 

Following its release of the final Prototype Balance of Performance regulations for next week’s Rolex 24 At Daytona, IMSA published Rolex 24 specs for its GT classes. The changes to the GT Le Mans and GT Daytona classes were made bases on data collected at the Roar Before The 24, held Jan. 3-5.

 

In GTLM, Porsche’s factory 991-based GT3 RSR will gain 15kg (33 pounds), up from 1210 to 1225. The CORE Autosport-run cars have also gained a bit of horsepower with a change from two 29.3mm restrictors to a pair of 29.6mm units.

 

Ferrari’s F458, which has Krohn Racing and Risi Competizione fielding entries at Daytona, has gone in the opposite direction on the scale, losing 15kg from 1245 to 1230. Like Porsche, the Prancing Horse also has more power coming its way with a jump from a 40.0mm restrictor at the Roar to 40.6mm for Daytona.

No changes to the Aston Martin V8 Vantage, BMW Z4 GTE or Corvette C7.R were listed, other than a slight increase in refueling hose restrictor flow rates for the Aston.

 

The pair of factory SRT Vipers run by Riley Technologies received the biggest weight break among the GTLM cars, and will carve 30kg (66 pounds) from their coupes for the Rolex 24. Even with the diet, the V10-powered machines will tip the scales as the heaviest cars in the class, dropping from 1280 to 1250 for the race. The Snakes also have an extra 10 liters of fuel capacity to work with, up from 110 to 120.

 

 


 

BoP tweaks in the GTD class were extensive.

Porsche’s 911 GT America, which commanded the Roar test, has had a drop in fuel capacity from 90 liters to 85. With many new GTD cars entering the TUDOR Championship, and limited time to equalize certain aerodynamic measurements, IMSA has implemented a series of Daytona-only rear wing height and fore/aft mounting changes with the majority of the marques.

 

By Sebring in March, IMSA expects to have the spec GTD rear wing element affixed in the same relative place on each car. For the Rolex 24, the Porsches will have its rear wing lowered 70mm below the top of the roof – the standard reference point for each car. All GTD cars at the Roar had their rear wings 50mm above the roof, meaning the Porsche has seen a 120mm total decrease in height.

 

Its rear wing has also been moved forward from the Roar by 125mm. By drawing the wing down and in toward the body, its effectiveness and downforce production is reduced, which then limits the car’s maximum cornering potential.

 

Simply put, but taking the wing out of the airstream and tucking it closer to the body, IMSA is aiming to lower cornering speeds, but the tradeoff, which was a bit of an issue at the Roar, will come with increased top speeds. For the rear-heavy Porsches, the wing location change will increase rear tire consumption rates and decrease rear stability under braking.

 

The minimum weight for the Porsche has also been set at 1215kg, a change from the 1180 listed for the Roar.

Ferrari’s GTD F458 is at a minimum of 1280kg, down from the 1309 posted at the Roar, and has seen a change in restrictors from the two 55.5mm units at the test to 50.5mm for the Rolex 24. The car will lose four liters of fuel capacity, down from 90 to 86. Its rear wing will be lower and moved forward, resting 37.5mm below its roof and forward 100mm from its Roar placement. It’s V8 engine has received an extra 200rpms for the race, up from 8000 to 8200.

 

The 2013 Rolex 24-winning Audi R8 has lost the +50mm rear wing height from the Roar, and will run with the element parallel to its roof. Its fore/aft position has not been changed. Like the Ferrari, the R8 has 200 extra rpm, up from 8400 to 8600.

 

Turner Motorsport’s lone GT3-spec BMW Z4 is the first car in the class to receive a taller tire for the Rolex 24. The 305/650/R18 Continentals it used earlier in the month will be replaced with an extra 30mm of runner as 305/680/R18s are used for the race. Its rear wing height – the top spec element, not the smaller, lower element, retains the +50mm location above the roofline.

 

All GTD cars ran at the Roar with a mandatory 25mm rear wicker, and while that wicker height will carryover for most cars during the race, the Z4 has had 15mm taken off, down to 10mm, to improve its top speed. Its maximum rpm is 8750.

 

Aston Martin’s V12 Vantage has been given a 22kg (48.5 pound) weight break, and will also move to the tallerr 305/680/R18 front tires, gaining the same 30mm compared to what they ran at the Roar. The The Racer’s Group-run cars will get more power with a switch from two 46.0mm restrictors to 47.0mm plates. The British coupes, like the Audis, will have their +50mm rear wing height zeroed to run flush with the roofline.

 

The final GTD car to have its Rolex 24 BoP specs changed is the SRT Viper GT3-R run by Riley Technologies, and it will make use of the same taller front tires, the 305/680/R18s, will have its rear wing height zeroed and 15mm taken off its wicker like the BMW Z4.

 
Its V10 engine will have more ponies, thanks to a jump from twin 42.0mm restrictors to dual 45.0mm openings, but with the power increase, IMSA has dialed back the low-revving mill even more, taking it down to 6000 from 6300.

 

IMSA TUNE-IN:

Tune in for the 52nd Rolex 24 At Daytona at the following times:

 

Saturday, Jan. 25

2-4 p.m. ET on FOX (Live)
4-9 p.m. ET on FOX Sports 2 (Live)
 
Overnight (Jan. 25-26)
9 p.m. – 7 a.m. ET on IMSA.com (includes live images, in-car cameras and announcers)
 
Sunday, Jan. 26
7 a.m. – 3 p.m. on FOX Sports 1 (Live)

 

Tune in for the Daytona season opener at the following time:

Friday, Jan. 24

6 p.m. on FOX Sports 2 (Same Day)

MX-5 CUP | ROUND 9 – ROAD AMERICA

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