Indy 500: How often do you pit?

  • Thread starter chaosdd
Hi All,

Yesterday, I did the Indy 500 with a Peugeot 908 HDI. I did some experiments on tire and tankful mileage that I wanted to share and ask about your experience. Findings:

1. A tankful of diesel lasts ~42 laps on Indy in a diesel LM car.
How many laps are you getting on petrol LM cars? The sole point of using a diesel for endurance is the lower fuel consumption. Let's try to confirm this is in the game as well.

2. Soft tires 1#: On maximum attack, soft tires last ~20-23 laps. Laptimes around 40 sec. (sometimes dipping under).

3. Hard tires: 32 laps driven hard (43-44 secs per lap).

4. Medium tires: similar result, 42-43 secs.

Findings so far: no set of tires can last a fuel tank. If so, diesel doesn't make much sense.

5. A pit stop takes around 90 seconds.

6. Soft tires second try: Now I tried to drive as smooth as possible, almost without getting any skiding and squeling from the tires. Right tires were wearing off much quicker than left under maximum attack (surely), so I tried hard to prevent that.

The result was astonishing. I did 40 laps on a set of soft tires, lapping at 42-43 secs. This is approximately as much as a fuel tank lasts, which was the main objective. Also laptimes were under the best possible on hard tires, under maximum attack, lasting less (32-32 laps).

I tried to do the same with the medium tires (in order to get over 40 laps per set), but it wasn't possible with decent pace. Actually mediums wore faster. I haven't tried hards with such aggressive tire saving approach, but I think the results will be even worse and laptimes too slow.

Conclusion: fastest around Indy endurance is on racing soft tires. Driven just under the limit of skidding/squeling, they can outlast hard tires, while maintaining much better pace. Indy 500 can be done with only 4 pit stops (908 HDI).

I guess, similar results can be recreated on other tracks. However, I am yet to test it (no time for endurance). Also, it will be much more difficult to drive under the skidding limit on other tracks (braking and slow corners, you see :)).

What do you think? Do you agree and are you getting similar results?
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I was taking on about 68 litres for 25 laps on Racing Softs in the Minolta Toyota. Thought I could do 32 on Hards (or more likely Mediums) which I started the race with, but ran out of tyre on the last corner of the 32nd lap and had to try to get into the pits with an uncontrollable car. After that I switched to the Softs.
sauber mercedes c9 on soft tires ~ 28 laps
minolta on soft tires all race ~ 26 laps
in x2010 on soft tires all race ~ 27 laps
I'm going to do the Indy 500 with the Peugeot 908 tonight. I was wondering the same thing about the mileage and tires. Thanks for your research, now I know what to do :)
I will give the soft tires a try and see how many laps I can manage.

Was it an easy race by the way ? Can you post your setup also ?
I'm going to do the Indy 500 with the Peugeot 908 tonight. I was wondering the same thing about the mileage and tires. Thanks for your research, now I know what to do :)
I will give the soft tires a try and see how many laps I can manage.

Was it an easy race by the way ? Can you post your setup also ?

Setup: I cannot check it right now. I did some test laps. Suspension was hard and low (obviously). Don't remember the downforce, but wasn't maxed out. However, I might try increasing it, since theoretically can help reduce even more high speed tire skidding, thus helping the tire life. Transimission was 440 km/h, due to the diesel power curve. I hit 420 in a massive draft, once. Do a few test laps.

I won by 2+ laps. However, I barely made it to the finish with the last tires. If I had to pit, it would be very close. It seems the AI have some boost enabled, once you pull off. They were actually lapping at decent pace (43-44?), but pitting much rarely than me in the beginning. Obviously, they were preserving tires better than me, before I made dedicated efforts on that.

Other remark: on maximum attack, front right tire was wearing faster than rear right (some understeer). While driving for preserving the tires, rear right was going down faster. You might want to make some adjustments (dowforce, susp.) to even that out.

Skidding wears off tires much faster than driving itself. The softs have much higher threshold. Try to corner just under that threshold without any tire squeling (or very minimal). Let's see whether you can recreate 40+ laps on soft tires with decent pace (I'm not doing this again :)).
I did it with the F GT using DFGT manual with soft racing tyres and low downforce and was getting 39 laps a tank (running it until dry and rolling half a lap to the pits) tried hard to get 40 laps but was impossible for me, the tyres outlasted the fuel and still had life in them after 39 laps but i was forced to change them in the fuel stops anyway. I know this thread for for lm cars but I thought I'd put this F GT figure in as a reference :)
Hmm, 39 laps on a fuel tank for FGT vs 42 laps for a diesel LM car seems unfair. Obviously, FGT is easy on the tires as well. It has never been a real car anyway :)

Does anybody from the US know how often similar racers pit on Indy IRL?
On the FGT I can get 37 laps out of a tank, running lap times between 37.8 - 39.5 seconds. (Lap times < 38 seconds require lucky drafts with the backmarkers)

Don't seem to have any problem making racing softs last that distance, unless I spin out 'cos I hit a backmarker at speed. Didn't notice a lot of difference in wear/grip between racing softs and racing mediums.

Also: I tend to map the pit changes across the whole of the 200 laps, so I pit on laps 35, 70, 105, 140 & 170. I guess it's worth using a car that can go 40 laps per tank, because you could cut out the 5th pit; but I find running on ragged tyres more effort than I can be bothered with whilst driving 200 circles.

I did play around with fuel loads as well, but found that refuelling time per litre was less than the time advantage gained per lap per litre less of fuel (didn't measure anything scientifically, just used the ready-reckoner in my skull).
FGT on a DFGT, default tune, got 42 laps out of the first tank. Assumed I could get 42 out of 2nd tank of fuel.

Nope, just 41.

However, fuel ran out long before tires, so pitted on fuel.

Second pit, ran out on lap 84 at turn 2.

Third pit, ran out of fuel lap 126, turn 3.

Fourth pit was scheduled for lap 168, went in as soon as fuel turned red, no problems.

Finally learned my lesson.

AI starts pitting when I was on lap 42, and maintains same pit interval, so the AI was getting about 40 laps.

Chaosdd: I don't know for sure, but 40/45/50 seems about right.
I ran the FGT and tryed to squeeze 38 laps on the first tank but ran out of fuel coimng out of turn 4 on lap 38. Later in the race as the oil started to burn I was able to get 38 laps but unlike the LMP cars lap 37 was just as fast as lap 2. In fact laps 2-37 were within 1 10th of each other all in the 39s with pretty much a stock tune. Only real change was a slightly raised gear.
With my Nissan R92CP I had to pit around every 23 laps for tyres and every 46 laps for fuel.
Much more than my opponents (who were all LMP cars and thus a bit more frugal, lasting nearly twice as long as me) but my speed advantage made up for more time than the extra pitting cost me.
Red Bull X2010 with Soft Tires: Every 25 Rounds.
But because of the fuel :D

25 is not pushing the fuel to the lowest amount most likely. I have ran 27 lap stints constantly in the X2010, but I was using the access roads in the corners to run faster laps (by about 1-1.5 seconds). I will try a stint using the regular track later today. The fuel will deplete quicker than the tires will wear (even on Racing Soft).
I *believe* (don't quote me on this) that Indy car drivers plan between five and eight stops in the Indy 500, depending on race pace (crashes bring out caution flags that *greatly* extend fuel mileage), how hot they have to run the engine (leaders can usually dial the power back a notch or two and save fuel), gearing (many set up their cars so that the top three gears can be used all the way around the track--fourth for passing, fifth for cruising, and sixth for fuel-misering), and what the current rule is on fuel tank size. That would indicate, depending on strategy, pitting, on average, every 25-33 laps, though this is often thrown off by full-course cautions seeing everyone pit to try and avoid a green-flag stop that can cost two laps or more.

Last I heard, IRL rules set a 35-gallon limit, running straight (denatured) ethanol fuel, very roughly equivalent in terms of energy content to 25 gallons of gasoline, so take that as you will.
I did my first attempt yesterday (didn't finished - got only 1,5 hour free) i was racing with BMW C12 and i had to pit every 20-22 laps. I was mainly hot driving - making ~39sek a lap, and my tires didn't last long.
Zonda R '09 - 20 Laps (Racing Soft & IIRC 65L Fuel)

Using the Medium or Hard compound was worse on tyre wear (more tyre slip/squeal) as I had to push very hard to ensure I was making up enough time to win the race with double the pit stops :scared:. Ended up winning by 1.75 laps (saw them in turn 1 as crossed the line... :mad:) and made 9 stops (obviously). By turns 3 & 4 on lap 19 I was needing to brake to get initial turn-in of car as tyres were so badly worn :nervous: but managed 41.0-41.2 consistently or dipped into high 40.x :) with good draft when passing other cars.

So, if you want a good challenge. Do it in the Zonda R! :sly:
BMW V12 and Audi R8 '05 both 30 laps per stop. If I slowed down a bit into the 41's with BMW I could get 35-36 laps per stint. I'd rather do 39's though so 30 laps. All with soft race tyres. They lasted better than medium and hard tyres.

The AI Audi R8 '01 was getting 43 laps per stint though. How it did that I have no idea.
Using the Medium or Hard compound was worse on tyre wear

I had the same experience with a Minolta. I did Indy 500 the first time today using a joypad and no driving aids whatsoever, but automatic shifting.

I didn`t pay alot attention first, but later I tryed every tyre and felt hard racing tyres were worn out faster than soft. It could be such a high speed during a corner destroys hard material on a hard surface faster than softer material. Thats the only explanation i have for this experience today.

The Minolta was set to a top speed of 410km/h hit 385km/h on a straight 397km/h with drafting and slowed down to 350-360km/h through corners.

Laptimes reached from 38,7 to 40,0. Although i had noticable more pitstops than the AI I won with 12 laps ahead.

I don`t see the benefit of hard racing tyres. You could use them for races about 25-30 laps on regular tracks avoiding any pitstop compared to soft tyres.
But you have to pay more attention, you can`t take certain sectors as fast and you may even have to brake or roll while you could go full throttle with soft tyres in some cases (car<>track<>corner).
Considering you risk to spin out alot more with hard tyres which takes away alot from their lifespan thats another point to choose soft racing tyres.

All in all the lifespan of hard tyres don`t seem to be noticable longer to accept all drawbacks they have.
Did this with the Peugeot 908 using racing hard tires. The tires don't last 40 laps so I need to do at least 5 pitstops. I'm pitting every 35 laps or so and fill the tank up to 80 liters. This way you can do a few laps more if you're in a beneficial (slipstream) position.
I used the PEUGEOT 908, but made only 25 laps on RS, maybe 27 sometimes. AI didn't stand a chance though, won by four or five laps. Noticed a similar phenomenon like some of you: the 908 was eating his hard tires faster than soft - wtf :P
citreon 2cv, no tyre or fuel stops, takes one week though..........
Interesting read. Im working to unlock the Indy 500 and have been considering what car to use and fuel/tire tactics.
Your 908's, are you guys stock car? or tuned to the +900hp?
Quick indy question, how long does the race take? Obviously it depends on the car, but I'd like a ballpark figure so I know how much ironing I will have to get keep the wife quiet. :)
Quick indy question, how long does the race take? Obviously it depends on the car, but I'd like a ballpark figure so I know how much ironing will I have to get keep the wife quiet. :)

have her as a second driver for the endos đź’ˇ