v2.52 includes updates to the tires, brakes, P1 boost settings, and damage modeling. Recommended reading from the model developers:

v2.52 summary

Tips concerning v2.51 and (2.52)
Sometimes there’s just aren’t enough hours in the day or week to do all the things you’d like or that pop up into your mind from time to time. One of the things I had originally wanted to do was post a reminder about the v2.51 changes before the GT race. But time and opportunity both being short this week I couldn’t get to it. But it’s in plenty of time for the four-class race.

First of all, remember, the biggest overall change in the mod has been the temperatures. By that we mean the tires and brakes have very different temperature characteristics than they did before.

THE TIRES:
When it comes to the tires what you’ll typically find is that the tires take a bit longer to heat up. Generally it takes about three good laps before the tires come up to temp. Once they’re up however they stabilize and will remain at temp much better than they did before. However because of this change the formation lap is something that you should factor into your race strategy because the tires, just as they did before, will cool off during the formation lap and the time spent sitting on the grid.

Now despite what some may want to believe, the new tires are NOT any more difficult to drive when they're cold than they were before. The only difference is that 1) the tires start out about 10°F (5.55°C) warmer than they did before. And 2) because they take longer to warm up you probably should not be as aggressive during the opening laps unless you feel that your talent is such that you can still drive fast on cold tires.

Medium Tires:
On a track like Silverstone we’ve found through testing that the medium tires are for the most part about a second to a second and a half faster per lap. This means that you will definitely gain a performance advantage using the medium tires. However… the medium tires do NOT take abuse very well. They are fast and stable, but only as long as you are smooth and stable. If you start throwing the car around the corners the mediums will heat up and once the medium tires overheat they become more unstable than the hard tires will at those same temperatures. So if you really like to throw the car around the corner and push your car hard then the better tire choice for you will be the hard compounds.

Another change is that the medium tires do not degrade as fast as they did before, but again, only as long as you treat them right by driving smoothly. As long as you treat them right you will probably be able to create a significant gap over the competitors who chose the hard tires. The strategy of course comes down to how much of a gap you can build up verses how long it takes to change a set of tires and only you can determined that outcome.

Qualifying Tires:
Believe it or not the qualifying tires are faster than the mediums, BUT only if you get them up to their proper operating temperatures, which is 115°C (240°F). The qualifying tires are meant to be abused and are specifically designed for very aggressive driving, consequently they respond well to heat. The higher optimum temperature rating however may require a slight change to your setup. Again this is something that only you and your race engineer can decided, but remember, if you can only get the qualifying tires up to 230°F (110°C) you’ll probably be better off qualifying on the mediums. So when it comes to the qualifying tires the advantage will go to those who take the time to test with the qualifying tires. - As opposed to just coming in and throwing them on and taking off with no adjustments to your setup or your driving style.

THE BRAKES:
Brakes temperatures are the other big change, for all of the cars. Again, you can’t use the same approach to the v2.51 brakes as you did in 2.2 These brakes actually heat up and will stay warm and fade and fail if you abuse them or let they stay too hot over the course of the race, however you do have plenty of options to cope with these new characteristics.

First, you have seven different brake duct options to choose from in every car now. The default setting is 4, but you should run some good hard race laps, with a full tank, before you commit to the default setting. If you have a heavy braking style then you will need to make some adjustments. First and foremost you need to choose a duct setting that will help you keep the brakes cooler. Once you have the temperatures stabilized you’ll need to consider how often the brakes get hot during a full tank run. If they get hot a lot, but still cool off in between you may want to consider using a larger (thicker) brake rotor. If they get hot and stay hot then you should consider a larger brake duct setting.

A thicker brake rotor can also help dissipate some of the heat; however the primary purpose of the thicker brake rotors is to give you more surface area with which to wear away. Unfortunately ISI never implemented the optional brake pads, which would be the more natural choice, but at least with thicker rotors you’ll have a lot more surface area on the rotors to wear away before the brakes fail. Also, be mindful of the fact that the larger rotors also will increase the unsprung mass of the car, which, depending on the car, may change the car's handling characteristics somewhat.

Now if you find yourself using the thickest rotors and the largest brake ducts and the brakes are still too hot, you’d better hope that everyone who drives the car is experiencing the exact same thing because if they ain’t, then it’s all on you brudda. So you’d better figure out what you’re doing wrong and take the time to learn how to correct it. The one thing we’ve found is that you simply cannot late brake at every corner, during every lap and still expect the brakes to just take it.

P1 BOOST SETTINGS:
P1 drivers take note; You no longer have 5 different boost levels to choose from any more. Now you only have three. The biggest difference however is that each incremental setting produces more power than before, but it also burns more fuel than before. So don’t head out onto the track thinking you’ll just use the same 2 or 3 setting as you did before without experiencing very different results in your mileage.

DAMAGE MODELING:
You really need to pay attention to this section because these changes may drastically alter your race if you’re not careful.

Let’s face it; the nose and front splitter of an LMP car just sits out there, fully exposed for the whole world to see. Its carbon fiber in most cases, maybe fiberglass in others, but no matter what it’s made of it’s a sure bet that it’s not tank armor, right? Well trust us, it isn’t and neither are the noses of the LMP cars in this mod. From now on if you’re driving an LMP car and you run up behind or into another car you’d better just go ahead and plan on making a pit stop because you will suffer damage, more damage than before and possibly even severe damage, which includes losing the splitter entirely. If this type of damage happens, whatever you do, DO NOT try to race back to the pits. With the splitter gone you will have little or no downforce and without it you may just wind up doing more damage trying to limp back to the pits if you loose control of the car.

If you find yourself limping back to the pits, remember to keep your relative speed in mind. A speed that may feel eternally slow as you’re trying to crawl your way back to the pits may in fact turn out to be 60-70 mph or better. And without a nose to hold the front end down you car may still be good in a straight line, but will definitely be crap in the corners.

So what's the trick to avoid this? It’s simple really. Drive carefully and don’t do anything or take any unnecessary risks that might crunch the nose of your LMP car.

SUMMARY:
Hopefully by now you’ve recognized a pattern in that overly aggressive driving will create more problems that you think it may solve. Keep your lines nice and tidy and the tires will last and treat you well and perform very well. Don’t stomp on the brakes at every corner using brake ducts that are too small along with thinner rotors and they won’t fade or fail. Don’t run the boost all the way up on the P1 cars and not expect to suffer some sort of gas-guzzler penalty or inflict extra wear and thereby potentially damage on the engine. Also, if don’t hit other cars, you won’t loose a splitter. BTW just because the Porsche RS Spyder and Lola do not have removable splitters doesn’t mean that you won’t suffer the same level of negative effects as you would in the Audi, Pescarolo or Dome. Oh, and one more reminder about the revised damage modeling, don’t forget that the GT cars also have splitters.

The bottom line is, TESTING, TESTING, TESTING… This is the only way you will ever get the most out of the cars and learn to better understand the differences in v2.51. Test on your own and make sure you thoroughly examine these four features before you commit to a setup or race strategy.

LM tires description: Also included in this patch is a new set of LM tire compounds. The LM tire compounds have been specifically designed to generate more heat at tracks where the standard tires may be running considerably cooler than the optimum temperature of 230°F (110°C). However these special LM compound tires are NOT intended for use on most road courses because they will overheat very rapidly under normal race conditions. Furthermore the grip levels of the LM compound tires are slightly less than those of the standard compound tires. However when the track configuration requires a little extra heat in your tires heat, these are the tires to use.

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I highly recommend testing the new brakes as some people who 'brake heavy' and/or 'late' will need to make adjustments to their braking style, brake ducts and/or discs.