19" Wheel Options for 991 RS
02-09-2016, 12:38 AM
#31
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^ it doesn't really work that way, only on paper
you pick what you THINK will work, then you have to actually drive it.
case in point. if you just do numbers 245/315 works on 997GT3
when they are new, worked fine.
after one day on track the rear had enough wear that unless u turn off TC, the car goes crazy. it's not ABS. i cannot explain it, but the rear just spins and you will get to 50mph then wont go any faster. like i said, the car goes crazy. but by calc they should work.
there are other instances with other cars wiht the calc works but in reality they do not
same thing with wheel offset. you have to PUT IT ON the car.
using GT4 as example, you can have right offset on paper but the diameter can be such that (smaller) it will rub LCA radially (this is not a spec that's usually measured but once you try to mount the wheel, it becomes obvious).
also, just b/c it worked once doesn't mean it works. they may work when dry, but little bit of wetness, TC/PSM may go nuts due to sizing, as an example
u have to try it empirically.
you pick what you THINK will work, then you have to actually drive it.
case in point. if you just do numbers 245/315 works on 997GT3
when they are new, worked fine.
after one day on track the rear had enough wear that unless u turn off TC, the car goes crazy. it's not ABS. i cannot explain it, but the rear just spins and you will get to 50mph then wont go any faster. like i said, the car goes crazy. but by calc they should work.
there are other instances with other cars wiht the calc works but in reality they do not
same thing with wheel offset. you have to PUT IT ON the car.
using GT4 as example, you can have right offset on paper but the diameter can be such that (smaller) it will rub LCA radially (this is not a spec that's usually measured but once you try to mount the wheel, it becomes obvious).
also, just b/c it worked once doesn't mean it works. they may work when dry, but little bit of wetness, TC/PSM may go nuts due to sizing, as an example
u have to try it empirically.
02-09-2016, 02:15 AM
#32
^ it doesn't really work that way, only on paper
you pick what you THINK will work, then you have to actually drive it.
case in point. if you just do numbers 245/315 works on 997GT3
when they are new, worked fine.
after one day on track the rear had enough wear that unless u turn off TC, the car goes crazy. it's not ABS. i cannot explain it, but the rear just spins and you will get to 50mph then wont go any faster. like i said, the car goes crazy. but by calc they should work.
there are other instances with other cars wiht the calc works but in reality they do not
same thing with wheel offset. you have to PUT IT ON the car.
using GT4 as example, you can have right offset on paper but the diameter can be such that (smaller) it will rub LCA radially (this is not a spec that's usually measured but once you try to mount the wheel, it becomes obvious).
also, just b/c it worked once doesn't mean it works. they may work when dry, but little bit of wetness, TC/PSM may go nuts due to sizing, as an example
u have to try it empirically.
you pick what you THINK will work, then you have to actually drive it.
case in point. if you just do numbers 245/315 works on 997GT3
when they are new, worked fine.
after one day on track the rear had enough wear that unless u turn off TC, the car goes crazy. it's not ABS. i cannot explain it, but the rear just spins and you will get to 50mph then wont go any faster. like i said, the car goes crazy. but by calc they should work.
there are other instances with other cars wiht the calc works but in reality they do not
same thing with wheel offset. you have to PUT IT ON the car.
using GT4 as example, you can have right offset on paper but the diameter can be such that (smaller) it will rub LCA radially (this is not a spec that's usually measured but once you try to mount the wheel, it becomes obvious).
also, just b/c it worked once doesn't mean it works. they may work when dry, but little bit of wetness, TC/PSM may go nuts due to sizing, as an example
u have to try it empirically.
GMG setup with 19" 265/345 was fine, but James said they turned everything off. He did not mention anything about reversing the bolt (?LCA) or tweaking the brake line bracket as on GT3, but I presume that would be a distinct possibility as well on the RS...
02-09-2016, 07:39 PM
#33
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Going on hold
Hmmm. I don't have the kind of R&D cash to spend on wheels and tires that may not work with PASM, so I am stepping down until another brave soul tries the 19/19 path with PASM and hot laps.
The alternative that may help here is a 20" Hoosier that is coming in 2016 sometime. If that looks good, I will check tire diameters with 19/20 combo which should allow for similar front rear ratios and give me enough confidence to try them.
As for now, I just ordered a set MPSC2s for track set #2.
The alternative that may help here is a 20" Hoosier that is coming in 2016 sometime. If that looks good, I will check tire diameters with 19/20 combo which should allow for similar front rear ratios and give me enough confidence to try them.
As for now, I just ordered a set MPSC2s for track set #2.
02-10-2016, 01:36 AM
#34
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So you want to be the guinea pig? Let the rest of us know what we need to do?? I know you are going to do it anyways...lol
GMG setup with 19" 265/345 was fine, but James said they turned everything off. He did not mention anything about reversing the bolt (?LCA) or tweaking the brake line bracket as on GT3, but I presume that would be a distinct possibility as well on the RS...
GMG setup with 19" 265/345 was fine, but James said they turned everything off. He did not mention anything about reversing the bolt (?LCA) or tweaking the brake line bracket as on GT3, but I presume that would be a distinct possibility as well on the RS...
i ran 19 BBS both E07 and monoblock.
surprisingly the E07 3 pcs had more clearance than monoblock
both i had to file and reverse the bolt on LCA, no biggie. i also had to push the hard brake line a bit. other than that, they do work
but these were on 991GT3. i cannot speak from experience on RS.
and certainly turning off nannies will help. but i know some like to keep nannie on so that should also be tested. and similar test should be done on end of life worn tires too.
i be happy to be guinea pig, though i dont have an RS. if you get me one, i will test it.
09-19-2017, 12:08 AM
#38
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Is there more track experience now with 19" or 20" on RS with R7 / slicks?
Can anyone confirm SC is OK?
We have the GT2RS N2 MPSC2 arriving soon I guess but I'm getting tired of tossing a $2300 set every 3-4 days. Fronts will go longer but gets slower.
Bought set #18 today...
R7 cheaper
Can anyone confirm SC is OK?
We have the GT2RS N2 MPSC2 arriving soon I guess but I'm getting tired of tossing a $2300 set every 3-4 days. Fronts will go longer but gets slower.
Bought set #18 today...
R7 cheaper
10-14-2017, 09:32 PM
#40
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Changing the aspect ratio, i.e., going with a taller tire on a shorter rim does not appear to be a viable option as far as I can see.
The logical tires to put on 19" wheels would be Hoosier R7s in 265/35/19 and 345/30/19s and the front rear difference is 0.6" in diameter, whereas the MPSC2s in 20/21 have a difference of 1.4" in diameter. By my math the stock fronts are 4.9% smaller than the rears, whereas the R7s would only be 2.3% smaller than the rears. This seems like a big enough difference that the PASM may get wheel speed data that is different enough to confuse it. Anyone have experience with this?
We know they will fit, but in going this route are you committing to turning PASM off?
The logical tires to put on 19" wheels would be Hoosier R7s in 265/35/19 and 345/30/19s and the front rear difference is 0.6" in diameter, whereas the MPSC2s in 20/21 have a difference of 1.4" in diameter. By my math the stock fronts are 4.9% smaller than the rears, whereas the R7s would only be 2.3% smaller than the rears. This seems like a big enough difference that the PASM may get wheel speed data that is different enough to confuse it. Anyone have experience with this?
We know they will fit, but in going this route are you committing to turning PASM off?
265/35/19 (295/35 will even fit under the fender) and 345/30/19 will not upset SC.
But 235/35/19 front actually keeps the ratio between front and rear closer to OEM. for the tiny difference in actual thread width that may be a safer bet for SC on.
Setup will be a challenge because I don’t know enough.
We can now drop the car a lot, so it’s a matter of how much front grip we get /lose by adding / taking away rake VS the new diffuser add on/steep rear spoiler...
I can’t go down much I the rear because then I can’t drive home on 21”
So probably more rake and more front grip.. Diffuser ordered...
10-15-2017, 04:26 AM
#41
19 forgelines on yoko slicks with carbon brakes. I believe I posted the specs of the slicks somewhere else. Ran it with all off. No error messages I don't think TC and SC are as important on slicks as the limit is very very high and I suspect if you pass the limit might not be able to save it even with TC SC not sure. Tried with TC SC liked it without much more.
10-15-2017, 03:57 PM
#45
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Beautifully setup car Martini 
Haven't seen the post with your slick sizes but looks like you are running 690s in the rear? Seems there is room for a 710 and increase contact patch by 10% or so. Any reason behind it?
For reference (Trackcar post), specs given by the manufacturer are not always exact.. I measured my mounted R7 265/35 section width very precisely, on 9" wheels it is 10.4".. Rear width 325/30 is 13.0"
Trofeo 245/35 is 10.2".
Haven't seen the post with your slick sizes but looks like you are running 690s in the rear? Seems there is room for a 710 and increase contact patch by 10% or so. Any reason behind it?
For reference (Trackcar post), specs given by the manufacturer are not always exact.. I measured my mounted R7 265/35 section width very precisely, on 9" wheels it is 10.4".. Rear width 325/30 is 13.0"
Trofeo 245/35 is 10.2".