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Discussion Starter · #1 ·
Looking to do aftermarket wheels in a 20" front, 21" rear staggered setup. After some searching, seems that 235/30 20" fronts are OK without rub issues (thanks Feh).

Been reading through the threads here, there may be rub issues with 245 at full lock turn (I am assuming stock wheel 19x8" front with 245/35 tires) - (by Excelsior and ImHuntingWabbits) this was the thread here:

Max tire size on stock wheels

Anyone ever try 245x30 20" fronts, any undesired issues?

Which leads me to my next question #2: What would be the optimal setup in tire section width/profile heights for wheel widths in 9" front 12.5" rear, while retaining good steering feel while maintaining stability ? The rear tires will be 325/25 21". This would be for street use on PS4S tires and occasional fun runs on highly deserted streets far away from civilization.

Reading the experiences here and I am paraphrasing, it seems that this car is under-tired, probably to keep it more fun as you can approach the limits faster. I also see that 245's on stock 8" width wheels can numb the steering feel - is this because the section width of 245 is just too wide a tire and perhaps sidewalls flexing too much (that's question #3)?

Last question #4: any benefit to attempt to maintain the stock front 225 rear 285 ratio ? I am debating between a 235/30 or a 245/30 for 9" width front wheels. The 245 front combined with 325 rear would be closer to OEM F/R ratio than the 235/325 (just pertaining to tire width). The 245's would have bigger front contact patch, which I'm guessing will help for a car that is considered on the understeery side, but it would add more more rotational weight compared to the 235's, and importantly, might rub.

If 245's rub, then its moot, and I will go with the 235's.

Lastly, probably important, I'm assuming the wheel manufacturer has wheel offset parameters dialed in appropriately.

Anyways, thanks a bunch for the feedback and responses.
 

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I run 245s on these: Finspeed F10 forged wheels for 600LT / 570S / 675LT

245 PS4S is ok, but tires vary greatly in tread width. A 245 3R or AR1 will rub.

For the front wheel why do you want a 9” front wheel? It’s not clear to me it will fit, has anyone made one? 8.5” is pretty tight, I don’t have more than a few mm of clearance.

The rear might be ok. I’ve run 245 / 315 PS4S, but the handling was so bad I went back to stock sizes for the street. This car is really sensitive to tire diameter and we run 245/35R19 at the track but it’s poorly balanced. For that size you really want a > 708mm rear tire (diameter), which on a 21” wheel means you really want a 30 ratio. 325/25R21 is way shorter than the stock 285, your proposed fronts are taller. It will handle like garbage.

That math is what will determine your handling balance in addition to size / wheel selection.

You can use this site to compare sizes: Tire Size Calculator

Edit: It's probably worth summoning @savage600lt to talk about their experience with tires / TC / fit. Also MV Wheels might be your thing?

 

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Discussion Starter · #3 ·
Thanks ImHuntingWabbits, your post was extremely informed and insightful. I didn't realize that overall diameter had such a significant impact on handling. Your post has revolutionized my thinking on what I might try to do next.

Haha, that calculator link you sent is really nifty. Here I am doing my diameter calculations manually with notepad and windows calculator, like a dinosaur :ROFLMAO: , might as well pull out my abacus.

It's pretty interesting you mention 245F 315R was a hot mess. As far as fronts, assuming you went 245/35 fronts, that's a 2.4% tire diameter increase (doesn't seem like much, but like you said from experience, this car is sensitive to diameter changes), but also roughly a 8% increase in tire section width. Curious what the rear specs were. Maybe hard to say, but why do you think it went so poorly ?

I am sure the engineers at McLaren had the setup we have for a good reason at 225F 285R. Is 235 285 or 235 305 an overall improvement? I guess my question is has anyone found the holy grail tire and wheel size combo for our car that might improve upon the OEM specs?

I almost feel like needing to build the wheel around the tire, instead of selecting a wheel first and then tires after. Lol :)

Thanks for the great chat.
 

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It's pretty interesting you mention 245F 315R was a hot mess. As far as fronts, assuming you went 245/35 fronts, that's a 2.4% tire diameter increase (doesn't seem like much, but like you said from experience, this car is sensitive to diameter changes), but also roughly a 8% increase in tire section width. Curious what the rear specs were. Maybe hard to say, but why do you think it went so poorly ?
Front: 245/35R19
Rear: 315/30R20

So about as good as you can do in today's tire market but still +17mm front -7mm rear, so a big change in F/R balance. The 245 also moves the scrub radius a little bit on an 8.5" wheel because of the offset change, the steering geometry doesn't love it. It feels fine at the track but it's more jittery on the road, you lose the nimble feeling in the front end.

I guess my question is has anyone found the holy grail tire and wheel size combo for our car that might improve upon the OEM specs?
No, they haven't. There are a bunch of 600LT drivers in our area and no one loves bigger sizes more than the stock ones. If you want a 20/21 setup I would try to stick to the stock sizes / offsets / diameters as much as you can, you're not really winning anything otherwise.

You can change compound for more grip and handling balance. For example an R888R or Goodyear Supercar 3 or Goodyear SuperSport have great street-temp grip and allow you to use a lot more pedal when cold than the PS4S or a track tire like the AR1 / 3R. On summer days (75-80deg) my 3Rs would be hot enough on the street that I could use WoT uninhibited in the right conditions though.

But yeah your intuition is correct, build the wheel for the tire, and if you can figure out what car that tire is built for. If that manufacturer dies, or the car becomes less popular, tire selection will decrease significantly.
 

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Discussion Starter · #5 ·
So about as good as you can do in today's tire market but still +17mm front -7mm rear, so a big change in F/R balance. The 245 also moves the scrub radius a little bit on an 8.5" wheel because of the offset change, the steering geometry doesn't love it. It feels fine at the track but it's more jittery on the road, you lose the nimble feeling in the front end.
Great technical info. Sometimes you make modifications, but also need to factor in other variables since everything is interconnected. Steering feel is important on the street since I won't be be taking it to the track.

You can change compound for more grip and handling balance. For example an R888R or Goodyear Supercar 3 or Goodyear SuperSport have great street-temp grip and allow you to use a lot more pedal when cold than the PS4S
Awesome advice. I have a really hard time with the Trofeo R's. It takes forever to warm them up despite living in a pretty warm climate. I'm spinning in 1st and 2nd and 3rd and by the time they are somewhat warm, my drive is over and already back home. But I guess that's what to expect from an R compound on the street. Could also be my tires are harder since they are older (original OEM made in 2018). I was contemplating PS4S since I run them on two other cars (less powerful than the Mac) and they were fine for the street and gave decent lateral grip. However, with your advice, I would like to give GS3's a look (tirerack has them in 235/35 305/35). I have read the R888R are kinda noisy, but that's fine, since the 600LT is noisy. Any experience with the PS Cup 2 Connect ?

I checked out your very informative post here, btw:


Thanks!
 

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Looking to do aftermarket wheels in a 20" front, 21" rear staggered setup. After some searching, seems that 235/30 20" fronts are OK without rub issues (thanks Feh).

Been reading through the threads here, there may be rub issues with 245 at full lock turn (I am assuming stock wheel 19x8" front with 245/35 tires) - (by Excelsior and ImHuntingWabbits) this was the thread here:

Max tire size on stock wheels

Anyone ever try 245x30 20" fronts, any undesired issues?

Which leads me to my next question #2: What would be the optimal setup in tire section width/profile heights for wheel widths in 9" front 12.5" rear, while retaining good steering feel while maintaining stability ? The rear tires will be 325/25 21". This would be for street use on PS4S tires and occasional fun runs on highly deserted streets far away from civilization.

Reading the experiences here and I am paraphrasing, it seems that this car is under-tired, probably to keep it more fun as you can approach the limits faster. I also see that 245's on stock 8" width wheels can numb the steering feel - is this because the section width of 245 is just too wide a tire and perhaps sidewalls flexing too much (that's question #3)?

Last question #4: any benefit to attempt to maintain the stock front 225 rear 285 ratio ? I am debating between a 235/30 or a 245/30 for 9" width front wheels. The 245 front combined with 325 rear would be closer to OEM F/R ratio than the 235/325 (just pertaining to tire width). The 245's would have bigger front contact patch, which I'm guessing will help for a car that is considered on the understeery side, but it would add more more rotational weight compared to the 235's, and importantly, might rub.

If 245's rub, then its moot, and I will go with the 235's.

Lastly, probably important, I'm assuming the wheel manufacturer has wheel offset parameters dialed in appropriately.

Anyways, thanks a bunch for the feedback and responses.
Looking to do aftermarket wheels in a 20" front, 21" rear staggered setup. After some searching, seems that 235/30 20" fronts are OK without rub issues (thanks Feh).

Been reading through the threads here, there may be rub issues with 245 at full lock turn (I am assuming stock wheel 19x8" front with 245/35 tires) - (by Excelsior and ImHuntingWabbits) this was the thread here:

Max tire size on stock wheels

Anyone ever try 245x30 20" fronts, any undesired issues?

Which leads me to my next question #2: What would be the optimal setup in tire section width/profile heights for wheel widths in 9" front 12.5" rear, while retaining good steering feel while maintaining stability ? The rear tires will be 325/25 21". This would be for street use on PS4S tires and occasional fun runs on highly deserted streets far away from civilization.

Reading the experiences here and I am paraphrasing, it seems that this car is under-tired, probably to keep it more fun as you can approach the limits faster. I also see that 245's on stock 8" width wheels can numb the steering feel - is this because the section width of 245 is just too wide a tire and perhaps sidewalls flexing too much (that's question #3)?

Last question #4: any benefit to attempt to maintain the stock front 225 rear 285 ratio ? I am debating between a 235/30 or a 245/30 for 9" width front wheels. The 245 front combined with 325 rear would be closer to OEM F/R ratio than the 235/325 (just pertaining to tire width). The 245's would have bigger front contact patch, which I'm guessing will help for a car that is considered on the understeery side, but it would add more more rotational weight compared to the 235's, and importantly, might rub.

If 245's rub, then its moot, and I will go with the 235's.

Lastly, probably important, I'm assuming the wheel manufacturer has wheel offset parameters dialed in appropriately.

Anyways, thanks a bunch for the feedback and responses.
These Finspeed Custom wide wheels with 245-30-19 and 305-30-20 will fit a 600LT perfectly, without any rubbing:
 

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Discussion Starter · #8 ·
These Finspeed Custom wide wheels with 245-30-19 and 305-30-20 will fit a 600LT perfectly, without any rubbing:
Hi Pilota, I am not interested at the moment, but if anything changes, will let you know. Thanks.
 

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Discussion Starter · #10 ·
I agree entirely. One of them was to distance track performance from the "super series" cars, for marketing and profit generation. The "distance" could be removed with wider tires and a tune.
:ROFLMAO:. I have seen this sentiment before regarding the 600LT and it being "under-tired." There's even a thread out right now about under-tiring and McLaren, in general.


In your opinion, if you had to redesign the tire and wheel size for the 600LT to optimize performance on a stock OEM tune, what would you use ?
 
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