Finally got wheels, now need tire help.
04-08-2012, 04:02 PM
#16
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^^^Really? This worries me as I do not want to deal with any rubbing whatsoever.
Well, the wheels arrive Tuesday. I'll measure the offset and report back before I order the tires.
Nick, can you tell me what the offset of that 9" wheel is?
Also there is another member on this forum who is running a 9.5" CCW wheel without any problems.
Well, the wheels arrive Tuesday. I'll measure the offset and report back before I order the tires.
Nick, can you tell me what the offset of that 9" wheel is?
Also there is another member on this forum who is running a 9.5" CCW wheel without any problems.
Last edited by RAudi Driver; 04-08-2012 at 05:33 PM.
04-08-2012, 04:08 PM
#17
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I think the effective offset for a 9" wheel for the front of a 997 GT2/3 should be around 45mm, but -here is the caveat- I cannot verify since my car is sitting at Champion Motorsport's showroom until Monday or Tuesday when it comes back.
The orange GMG car that is in another thread uses 10" wide wheels with Cup fenders and flares, greatly enhancing the available area under the fender. I wouldn't use that as an example since it is pretty far from the standard fender.
The orange GMG car that is in another thread uses 10" wide wheels with Cup fenders and flares, greatly enhancing the available area under the fender. I wouldn't use that as an example since it is pretty far from the standard fender.
04-08-2012, 04:20 PM
#18
Mike-
Read carefully between the lines.
1. Paul said that 245 width tires rubbed at stock height and stock spring rate. The only way that changed was to up the spring rate (reduce travel).
2. He also said he had to rotate the strut to accommodate the inner side of the tire/wheel.
What I have found- on a 9" wheel, proper backspacing, 245 width on 2.7 degrees camber is slightly beyond the limit of what the OE fender can accommodate (which is why the newer cars with 245/35R19 fronts have the carbon fenders or high clearance steel fender/plastic flare). That is, if you are **** like me, and refuse to accept any sort of rubbing whatsoever and require OE fit and finish (to me, the tire/fender rubbing, or doing what Paul did with spring rates, strut rotation etc., is not acceptable, but for others it may be perfectly fine).
Read carefully between the lines.
1. Paul said that 245 width tires rubbed at stock height and stock spring rate. The only way that changed was to up the spring rate (reduce travel).
2. He also said he had to rotate the strut to accommodate the inner side of the tire/wheel.
What I have found- on a 9" wheel, proper backspacing, 245 width on 2.7 degrees camber is slightly beyond the limit of what the OE fender can accommodate (which is why the newer cars with 245/35R19 fronts have the carbon fenders or high clearance steel fender/plastic flare). That is, if you are **** like me, and refuse to accept any sort of rubbing whatsoever and require OE fit and finish (to me, the tire/fender rubbing, or doing what Paul did with spring rates, strut rotation etc., is not acceptable, but for others it may be perfectly fine).
1) not at stock ride height but at 'slightly' lower than Stock Ride height it happened to me - by slightly it was 5mm lower. But I was running -2.5 front camber without strut rotation and thus caster was implicitly very high (let's say 8.9). What I then did was have the strut tops rotated and shimmed the LCA to add track and add some caster back - caster is now 7.9-8.0. I didn't do the strut rotation because of the outside lip or the inside lip - it was to change the wheel position for caster. I then ordered 7mm spacers and longer wheel bolts to increase the front track. Even with the spacers, the 245 MPSS with struts rotated have well over a fingers spacing to the fender lip. And this is why, with struts rotated, proper offset, 9.5" wheel + a little fender work you can fit a 285 tire in there - there is space if you do everything correctly.
2) using the above technique, without fender extensions like on the mk2 cars, you can fit a big tire but the wide track / wide tire will protrude from the lower part of the car - you can use fender extensions or cupcar liner extensions in the front to improve the aero
I'm going to watch the Masters now
Last edited by 997gt3north; 04-08-2012 at 11:20 PM.
04-08-2012, 04:46 PM
#19
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Paul, I don't want to get into an argument over this but...
1. Rotating the strut reduces caster. That is bad. That is arguably the worst tradeoff to accommodate the tire width, in my opinion (and that is purely that, my opinion, for you that may work fine). That is almost as bad as increasing scrub radius.
2. If the tire path intersects the fender surface, rubbing will result. No way around that. Using higher spring rates to "cure" this causes other problems, some that are significantly bigger than just trying to find a way to stuff a bigger tire in a fender. And for some of us that go to bumpy tracks (say, like Sebring) the higher spring rate may not cure the rubbing.
Have fun watching the Masters, golf never really interested me much unlike a lot of my friends.
1. Rotating the strut reduces caster. That is bad. That is arguably the worst tradeoff to accommodate the tire width, in my opinion (and that is purely that, my opinion, for you that may work fine). That is almost as bad as increasing scrub radius.
2. If the tire path intersects the fender surface, rubbing will result. No way around that. Using higher spring rates to "cure" this causes other problems, some that are significantly bigger than just trying to find a way to stuff a bigger tire in a fender. And for some of us that go to bumpy tracks (say, like Sebring) the higher spring rate may not cure the rubbing.
Have fun watching the Masters, golf never really interested me much unlike a lot of my friends.
04-08-2012, 05:37 PM
#20
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nick and paul are both right. i think just slight communication glitch.
rotate strut reduce caster but any one who rotate strut on GT3 must be tracking. else it's much ado about nothing. if you track and rotate you must also be shimming to the caster back and more camber.
on a street driven car. dont fk around with offset and tire sizes. OEM is best. you will not out think porsche. on track is totally different and not only do i rub fenders, i also pulled the coolant lines and such all off b/c my tires is too big. but that's on track.
there is no free lunch.
rotate strut reduce caster but any one who rotate strut on GT3 must be tracking. else it's much ado about nothing. if you track and rotate you must also be shimming to the caster back and more camber.
on a street driven car. dont fk around with offset and tire sizes. OEM is best. you will not out think porsche. on track is totally different and not only do i rub fenders, i also pulled the coolant lines and such all off b/c my tires is too big. but that's on track.
there is no free lunch.
04-08-2012, 06:15 PM
#21
nick and paul are both right. i think just slight communication glitch.
rotate strut reduce caster but any one who rotate strut on GT3 must be tracking. else it's much ado about nothing. if you track and rotate you must also be shimming to the caster back and more camber.
on a street driven car. dont fk around with offset and tire sizes. OEM is best. you will not out think porsche. on track is totally different and not only do i rub fenders, i also pulled the coolant lines and such all off b/c my tires is too big. but that's on track.
there is no free lunch.
rotate strut reduce caster but any one who rotate strut on GT3 must be tracking. else it's much ado about nothing. if you track and rotate you must also be shimming to the caster back and more camber.
on a street driven car. dont fk around with offset and tire sizes. OEM is best. you will not out think porsche. on track is totally different and not only do i rub fenders, i also pulled the coolant lines and such all off b/c my tires is too big. but that's on track.
there is no free lunch.
I am speaking about what I have done to make the car work on the track.
Basically my car is set up to run a 265 Hoosier if I want to - it works and it doesn't rub.
The OP is trying to fit a 9.5" wheel - I'm trying to help him do it. If you go into a situation with the correct expectations it will be fine.
Rotated strut, shims, top caster adjustment, slight fender rolling, 255 or 265 to fit the rim. When you are going 1 inch wider than a 'stock' rim - you have to be ready to 'make' it work.
04-08-2012, 06:28 PM
#22
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ok, I'm getting scared. I am more than happy to run stock tire sizes for the street. I can always pick up a set of 18's for the track, later down the line, if I feel that I need more rubber on the tarmac.
That being said, I got the wheels for a decent price, $3k. The seller, who isn't the owner of the wheels, told me that the fronts are 9.5" in width. I still purchased them because I can get 2 new outer halves, to make them 9's, for a little over $200 each if needed. It would be nice to not have to spend the extra money on wheel halves, so that is why I am inquiring about tires that will be a better fit, to the wheels, than the stock sizes.
I think at this point I should just go with the 245's and call it a day.
Keep the replies coming. I have a lot to learn.
That being said, I got the wheels for a decent price, $3k. The seller, who isn't the owner of the wheels, told me that the fronts are 9.5" in width. I still purchased them because I can get 2 new outer halves, to make them 9's, for a little over $200 each if needed. It would be nice to not have to spend the extra money on wheel halves, so that is why I am inquiring about tires that will be a better fit, to the wheels, than the stock sizes.
I think at this point I should just go with the 245's and call it a day.
Keep the replies coming. I have a lot to learn.
04-08-2012, 07:04 PM
#23
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^ i can't help you there. wheels and offset are VERY tricky. and when ppl say "offset" 1/2 of them don't know what they are talking about. i spoke with CCW (john, who's very good at this) and ryan at jongbloed (who's also very good) and guess what, they give me different numbers. until you actually put the thing on your car with your alignement and your road condition, you just dont know. that's the most accurate news i can give you. and take this, not every GT3 is the same. strange but true. i have 9 or maybe 10 996gt3's. you put them on a body shop frame jig, they do not measure the same (i am talking brand new cars that's not hit ever). so if one wants to play with wheel sizes, you have to try and see. my gut feelings is 9.5 will fit, if you get right offset and right camber. but what's the right offset and right camber for you.
04-08-2012, 08:09 PM
#24
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Mooty, Paul, like I said, I think it depends on your level of acceptance of the result. I don't think Paul is wrong from his point of view, but neither am I, we are just splitting hairs. Now the OP can decide which side of the hair he wants to split.
Wheel offsets are a strange thing, they should be measured from the wheel's centerline, but many US wheel guys use backspace numbers in inches then convert. Neither is wrong, although it does create confusion. Purner is an old friend, he built wheels for me a decade ago.
Would I use a 9.5" wheel? Knowing what I do about the space available and the alignment I prefer, probably not. But I do use the biggest tire I can fit in front with OE fenders that haven't been molested with rollers and baseball bats.
Wheel offsets are a strange thing, they should be measured from the wheel's centerline, but many US wheel guys use backspace numbers in inches then convert. Neither is wrong, although it does create confusion. Purner is an old friend, he built wheels for me a decade ago.
Would I use a 9.5" wheel? Knowing what I do about the space available and the alignment I prefer, probably not. But I do use the biggest tire I can fit in front with OE fenders that haven't been molested with rollers and baseball bats.
04-08-2012, 08:43 PM
#25
Race Director
Mooty...the 9x18 CCW's I bought from you....John @ CCW said they are a et50 offset. He said this is what he builds for all Carrera S and GT3's. I mostly used 245/40/18 on those 9x18 with that offset. No rubbing, drove to and from the track...in and out of tight parking lots....this set up worked great. I had Sport PASM which is lower than the Carrera S stock PASM...looked almost as low as stock GT3 factory height. Also looked like it could have gone slightly lower with no issues. I also used 255/35/18...slightly short diameter but this size worked to.
04-08-2012, 08:46 PM
#26
Race Director
LOL...not reading well....now I'm having a tough day after polishing and waxing some of my boat and my lower back is in bad pain. Thanks....got it...Super Sports. I was in R-Compound thought mode....even went back and looked on Michelin and Pirelli websites at the MPSC and Trofeo....didn't realize you were talking about Super Sports.
Mike,
You are having a tough day or not reading very well.
The 255/30/19 is a Mich Pilot Super Sport
I believe the pics of the Orange 997gt3.mk1 that GMG is showing on another thread with all the body mods, wide fenders has the 255/30/19s - I zoomed in and am pretty sure that is them.
All the best
Paul
You are having a tough day or not reading very well.
The 255/30/19 is a Mich Pilot Super Sport
I believe the pics of the Orange 997gt3.mk1 that GMG is showing on another thread with all the body mods, wide fenders has the 255/30/19s - I zoomed in and am pretty sure that is them.
All the best
Paul
04-08-2012, 09:44 PM
#27
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Wheel offsets are a strange thing, they should be measured from the wheel's centerline, but many US wheel guys use backspace numbers in inches then convert. Neither is wrong, although it does create confusion. Purner is an old friend, he built wheels for me a decade ago.
you are RIGHT ON.
most US manufacturers use back spacing numbers while euro uses ET.
04-08-2012, 09:45 PM
#28
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Mooty...the 9x18 CCW's I bought from you....John @ CCW said they are a et50 offset. He said this is what he builds for all Carrera S and GT3's. I mostly used 245/40/18 on those 9x18 with that offset. No rubbing, drove to and from the track...in and out of tight parking lots....this set up worked great. I had Sport PASM which is lower than the Carrera S stock PASM...looked almost as low as stock GT3 factory height. Also looked like it could have gone slightly lower with no issues. I also used 255/35/18...slightly short diameter but this size worked to.
and i put my money where my mouth is (is that how they say it in english?)
i have 8.5", 9", and 9.5" fronts. i have ran different width tires on my own car with my preferred offset so i know if it rubs for ME or not. like nick said, it depends no what is ACCEPT to YOU. when you push beyond 9.5, you are playing with fire and i am a pyro.
on the 4.0, i cannot afford to crack the stupid CF front fenders so i will not be experimenting with wheel width. whatever stock width it came with it will stay that width.
04-08-2012, 11:35 PM
#29
ok, I'm getting scared. I am more than happy to run stock tire sizes for the street. I can always pick up a set of 18's for the track, later down the line, if I feel that I need more rubber on the tarmac.
That being said, I got the wheels for a decent price, $3k. The seller, who isn't the owner of the wheels, told me that the fronts are 9.5" in width. I still purchased them because I can get 2 new outer halves, to make them 9's, for a little over $200 each if needed. It would be nice to not have to spend the extra money on wheel halves, so that is why I am inquiring about tires that will be a better fit, to the wheels, than the stock sizes.
I think at this point I should just go with the 245's and call it a day.
Keep the replies coming. I have a lot to learn.
That being said, I got the wheels for a decent price, $3k. The seller, who isn't the owner of the wheels, told me that the fronts are 9.5" in width. I still purchased them because I can get 2 new outer halves, to make them 9's, for a little over $200 each if needed. It would be nice to not have to spend the extra money on wheel halves, so that is why I am inquiring about tires that will be a better fit, to the wheels, than the stock sizes.
I think at this point I should just go with the 245's and call it a day.
Keep the replies coming. I have a lot to learn.
If the rim offset is correct, the wheel will fit - whether it is the 245, 255, or 265.
Given everything you have written so far, I would recommend the 255.
Paul
04-08-2012, 11:44 PM
#30
Race Director
RAudi Driver....these are 2 is an important questions I should have asked you....
1-Are these track wheels/tires or going to be your street wheels/tires?
2-Also what is your track experience?
If these are street tires and your new to the track...1 year or under and in the instructed group.....stay with stock or close in sizes and use the new Michelin Super Sports or a tire like that.
If you are now in the solo run group and looking for track wheels and sticky tires you can experiement with what 997gt3north has posted but you will not find his recomended 255 size in a r-compound tire and I'm not sure myself if you can get 265's in your fenders without some suspension magic....so 245's should work. This all depends on the offset of these 9.5" wide wheels and on a GT3 without fender extensions like the RS version has I'm really curious to find out how this all fits. However making these into a 9x19 with an offset (euro spec) of et50-53 is cheap and simple.
1-Are these track wheels/tires or going to be your street wheels/tires?
2-Also what is your track experience?
If these are street tires and your new to the track...1 year or under and in the instructed group.....stay with stock or close in sizes and use the new Michelin Super Sports or a tire like that.
If you are now in the solo run group and looking for track wheels and sticky tires you can experiement with what 997gt3north has posted but you will not find his recomended 255 size in a r-compound tire and I'm not sure myself if you can get 265's in your fenders without some suspension magic....so 245's should work. This all depends on the offset of these 9.5" wide wheels and on a GT3 without fender extensions like the RS version has I'm really curious to find out how this all fits. However making these into a 9x19 with an offset (euro spec) of et50-53 is cheap and simple.