svt13 Posted October 2, 2012 Report Share Posted October 2, 2012 I'm putting this here since now that we are all probably going to have alcoas lets discuss tire sizes So far it seems 265/35 and 285/35 works for the 20x9 and 20x10 combo. Also people keep it to this set up for conversation. Once we establish what works and what doesn't work with the regular set up we will discuss widened set ups. According to some 275/35 and 295/35 will also work. Again wondering how this will effect the speedo or gas milage if at all. But it seems these are the 2 sizes that require no modification and do not effect anything adversely. But lets discuss it so people with first hand experience please chime in. This is NOT a theortical debate. Only comment if you have actual experience with the set up you are talking about otherwise there will be too much misinformation being thrown around. Link to comment Share on other sites More sharing options...
Fast Mover Posted October 2, 2012 Report Share Posted October 2, 2012 This thread is exactly what I've been looking for!!!! Link to comment Share on other sites More sharing options...
svt13 Posted October 2, 2012 Author Report Share Posted October 2, 2012 Too bad no one has contributed yet. Link to comment Share on other sites More sharing options...
BCPD199 Posted October 2, 2012 Report Share Posted October 2, 2012 May I ask why you wouldn't/couldn't use the factory 265/40 on the front? Link to comment Share on other sites More sharing options...
patrickshelby Posted October 2, 2012 Report Share Posted October 2, 2012 May I ask why you wouldn't/couldn't use the factory 265/40 on the front? cause it's a 19" ...therefore the 40' serie Link to comment Share on other sites More sharing options...
Snoopy49 Posted October 2, 2012 Report Share Posted October 2, 2012 May I ask why you wouldn't/couldn't use the factory 265/40 on the front? The factory front tire is for a 19" wheel, the Alcoa's are 20" wheels. 265-40-19 = 27.35" Dia. 265-40-20 = 28.35" Dia. Link to comment Share on other sites More sharing options...
patrickshelby Posted October 2, 2012 Report Share Posted October 2, 2012 I'm putting this here since now that we are all probably going to have alcoas lets discuss tire sizes So far it seems 265/35 and 285/35 works for the 20x9 and 20x10 combo. Also people keep it to this set up for conversation. Once we establish what works and what doesn't work with the regular set up we will discuss widened set ups. According to some 275/35 and 295/35 will also work. Again wondering how this will effect the speedo or gas milage if at all. But it seems these are the 2 sizes that require no modification and do not effect anything adversely. But lets discuss it so people with first hand experience please chime in. This is NOT a theortical debate. Only comment if you have actual experience with the set up you are talking about otherwise there will be too much misinformation being thrown around. People have to post comments and suggestions with pictures otherwise it's useless. The bulging and the way tires are coming out of the fenders is not something you can describe with words...you must show it. The SS has 255/35/20 and 275/35/20 on these Alcoa, since the beginning of those wheels. That's not wide but the fit and look are perfect to me! Link to comment Share on other sites More sharing options...
BCPD199 Posted October 2, 2012 Report Share Posted October 2, 2012 The factory front tire is for a 19" wheel, the Alcoa's are 20" wheels. 265-40-19 = 27.35" Dia. 265-40-20 = 28.35" Dia. Thanks. I really can't believe I missed that detail. Link to comment Share on other sites More sharing options...
Iceman5000 Posted October 2, 2012 Report Share Posted October 2, 2012 I tried 295/35 20's on the rear at the Tire rack when I got mine. They stuck out of the Fender about 3/4". It didn't look good, and it would definitely rub when I lower my car. It may have rubbed anyway on a large bump or expansion joint. I told them to go with the 285/35's instead. These were Mich Pilot Super Sports. I went with 265/35 on the Front and they look fine. I love the tires! Link to comment Share on other sites More sharing options...
HyperStangs Posted October 2, 2012 Report Share Posted October 2, 2012 Okay, I'll throw my .02 in here.... when developing the car I think a lot of time had to be spent considering what in all likelihood would be the predominant use of the car - obviously. In this case, by far the most GT500 drivers will never see a track, and for that matter, will only street race mildly if at all. When you're spending this kind of money its likely you're all grown up... for the most part. But, having said that, safety is a concern. Therefore, a car designed with 650+ hp might have less rubber than can actually be used, and should be designed with considerable understeer to make it manageable. Understeer is "safe" believe it or not since the natural propensity is to correct with less power and more steering input.... safe. Oversteer, and in the extreme case of snap, is something entirely different and unless you're familiar creates a very dangerous situation. My guess is these cars come with intentionally too little rubber to actually use the power they make. 275's are entirely too little rubber to put down the numbers we're making.... smoke = no traction, but for the most part its safe. I drive my car and it will be a DD. I also track my car (corners are my thing) and "occasionally" enjoy a short/safe street encounter. I'm not into full-blown drag racing... but I get those who are. So, with that in mind I will be going with the following combination in conjunction with a hodge-podge of suspension upgrades I know work to improve handling & reduce unsprung weight (yeah I know the Alcoas are heavy, some things have to be for looks too) more so than drag: Griggs, BMR, Girodisc, etc. Fronts: Using the 20x10 w/ 37mm o/s and a 275x35x20 tire will move the wheel centerline inboard by ~13mm while the overall width is increased by an inch (25.4mm), keeping the tire centerline virtually unchanged, and the tire diameter remains within 1%. Visually, the difference in outward protrusion of the wheel would be nearly imperceptible. Rears: Using the 20x9 w/ 24mm o/s and widening them to 11.75 would keep the centerline of the wheel virtually unchanged by moving the TIRE face outward by the same 13mm's, but the bulk of the wider wheel is moved inward by ~57mm. Several owners are running as much as 325's on this particular setup, but I will likely go with a 305x30x20 to promote less understeer. The net result again would be visually imperceptible. The net gain of a combination like this with the correct suspension upgrades should be a car with far better cornering AND straight-line traction, while still maintaining a predictably manageable power steer. I cannot take credit for this particular setup as I first saw several people using it on other boards, but I ran the math and it looks sound. I've attached two files which show the exact measurements between the OEM S.S. wheel/tires and this particular setup. figure1.tiff figure2.tiff figure1.tiff figure2.tiff Link to comment Share on other sites More sharing options...
svt13 Posted October 2, 2012 Author Report Share Posted October 2, 2012 I tried 295/35 20's on the rear at the Tire rack when I got mine. They stuck out of the Fender about 3/4". It didn't look good, and it would definitely rub when I lower my car. It may have rubbed anyway on a large bump or expansion joint. I told them to go with the 285/35's instead. These were Mich Pilot Super Sports. I went with 265/35 on the Front and they look fine. I love the tires! These are more the kinds of posts this thread needs. Robert M needs to chime in here though because hes the one who told me 275/35 front and 295/35 rear was perfect. I too though am wanting to go with michelin super sports so I may end up going same width as stock. I believe the understeer tendancys and tracation will be the same between both stock and this set up since the tire patch is the unchanged. Which is the goal of doing this thread is to find out what set ups can people use without doing crazy mods to their cars or effecting things like the speedo and gas milage. Link to comment Share on other sites More sharing options...
shel-b001 Posted October 2, 2012 Report Share Posted October 2, 2012 When you order the rims it gives you the recommended tire size (i.e 255/35 zr20 front & 275/35/ZR20 rears) are these the ideal sizes?????? Link to comment Share on other sites More sharing options...
HyperStangs Posted October 2, 2012 Report Share Posted October 2, 2012 When you order the rims it gives you the recommended tire size (i.e 255/35 zr20 front & 275/35/ZR20 rears) are these the ideal sizes?????? Ideal for daily driver, overall balance and acceptable aesthetics.... yes. You can't go wrong doing what's tried and true. Link to comment Share on other sites More sharing options...
svt13 Posted October 2, 2012 Author Report Share Posted October 2, 2012 They are not ideal because they r based from before the 2011 Shelby's Hence the thread Link to comment Share on other sites More sharing options...
HyperStangs Posted October 2, 2012 Report Share Posted October 2, 2012 They are not ideal because they r based from before the 2011 Shelby's Hence the thread The chassis are "virtually" identical, its mainly cosmetic changes through the various stages of a single generation (S197) of a car. So, what worked on the 2011 still works, especially as it relates to wheel/tire fitment. "Ideal" is a loaded word... would they be "ideal" on the car for drifting? No. "Ideal" for the drag strip? No. But for the regular GT500 owner, staying fairly close to OEM specs is... well, ideal. Link to comment Share on other sites More sharing options...
HyperStangs Posted October 3, 2012 Report Share Posted October 3, 2012 Just a quick note for anyone trying to figure out o/s for the widened version of the 9's. I've run the calculations a few times and since the wheels are widened it moves the true center a bit inboard, making the effective new o/s 55.75 mm. Edit: Thats for 20x11.5 conversion. Link to comment Share on other sites More sharing options...
Jody Posted October 3, 2012 Report Share Posted October 3, 2012 I have a 2008 KR and I have the 20" Alcoa's in front and rear. I have 275 in front and 295's on rear. They are Nitto Invo's. They do not stick out past wheel well or fenders. They do not rub during hard cornering or sharp turns. If I were do do it all over again I would use the same size tires I have. Again, I have the stock KR suspension with an added BMR adjustable pan hard bar only. Link to comment Share on other sites More sharing options...
89Saleen215 Posted October 3, 2012 Report Share Posted October 3, 2012 '08 with FRPP suspension and Fays2 watts link - running 275/35's front and 295/30's rear. Speedo and mpg unchanged - no rubbing. However, the sidewall height doesn't match. My next rear set will be 295/35's and a tire adjustment via the SCT to fix the speedo. Link to comment Share on other sites More sharing options...
elanore Posted October 3, 2012 Report Share Posted October 3, 2012 Okay, I'll throw my .02 in here.... when developing the car I think a lot of time had to be spent considering what in all likelihood would be the predominant use of the car - obviously. In this case, by far the most GT500 drivers will never see a track, and for that matter, will only street race mildly if at all. When you're spending this kind of money its likely you're all grown up... for the most part. But, having said that, safety is a concern. Therefore, a car designed with 650+ hp might have less rubber than can actually be used, and should be designed with considerable understeer to make it manageable. Understeer is "safe" believe it or not since the natural propensity is to correct with less power and more steering input.... safe. Oversteer, and in the extreme case of snap, is something entirely different and unless you're familiar creates a very dangerous situation. My guess is these cars come with intentionally too little rubber to actually use the power they make. 275's are entirely too little rubber to put down the numbers we're making.... smoke = no traction, but for the most part its safe. I drive my car and it will be a DD. I also track my car (corners are my thing) and "occasionally" enjoy a short/safe street encounter. I'm not into full-blown drag racing... but I get those who are. So, with that in mind I will be going with the following combination in conjunction with a hodge-podge of suspension upgrades I know work to improve handling & reduce unsprung weight (yeah I know the Alcoas are heavy, some things have to be for looks too) more so than drag: Griggs, BMR, Girodisc, etc. Fronts: Using the 20x10 w/ 37mm o/s and a 275x35x20 tire will move the wheel inboard by ~13mm while the overall width is increased by an inch (25.4mm), keeping the tire centerline virtually unchanged, and the tire diameter remains within 1%. Visually, the difference in outward protrusion of the wheel would be nearly imperceptible. Rears: Using the 20x9 w/ 24mm o/s and widening them to 11.75 would keep the centerline of the wheel virtually unchanged by moving the wheel face outward by the same 13mm's, but the bulk of the wider wheel is moved inward by ~57mm. Several owners are running as much as 325's on this particular setup, but I will likely go with a 305x30x20 to promote less understeer. The net result again would be visually imperceptible. The net gain of a combination like this with the correct suspension upgrades should be a car with far better cornering AND straight-line traction, while still maintaining a predictably manageable power steer. I cannot take credit for this particular setup as I first saw several people using it on other boards, but I ran the math and it looks sound. I've attached two files which show the exact measurements between the OEM S.S. wheel/tires and this particular setup. figure1.tiff figure2.tiff Would this set up worck on the 2012 SS since the car has ben lowerd ??? Link to comment Share on other sites More sharing options...
svt13 Posted October 3, 2012 Author Report Share Posted October 3, 2012 '08 with FRPP suspension and Fays2 watts link - running 275/35's front and 295/30's rear. Speedo and mpg unchanged - no rubbing. However, the sidewall height doesn't match. My next rear set will be 295/35's and a tire adjustment via the SCT to fix the speedo. So 295/30 doesn't mess up the speedo but 295/35 does? Link to comment Share on other sites More sharing options...
662HP631TQ Posted October 4, 2012 Report Share Posted October 4, 2012 Ok a lot of this is centered around lowered cars I am seeing. I am not lowering my car, so what is the best tire size I can have for the 20X9 up front and 20X10 out back? Does anyone know? I won't track mine, I'll drive the hell out of it, but not on the track. So I don't care about ride height. Link to comment Share on other sites More sharing options...
89Saleen215 Posted October 4, 2012 Report Share Posted October 4, 2012 So 295/30 doesn't mess up the speedo but 295/35 does? Exactly. Ok a lot of this is centered around lowered cars I am seeing. I am not lowering my car, so what is the best tire size I can have for the 20X9 up front and 20X10 out back? Does anyone know? I won't track mine, I'll drive the hell out of it, but not on the track. So I don't care about ride height. If it's not lowered then you can get away with a bit more, however, if you don't want to mess with a tuner to fix the speedo then the 295/30 is the tire, but I don't like the sidewall height...too short for my taste. Look at my rear tire compared to my front: Link to comment Share on other sites More sharing options...
svt13 Posted October 4, 2012 Author Report Share Posted October 4, 2012 Exactly. If it's not lowered then you can get away with a bit more, however, if you don't want to mess with a tuner to fix the speedo then the 295/30 is the tire, but I don't like the sidewall height...too short for my taste. Look at my rear tire compared to my front: So then 295/30 would not be the tire 295/35 would be. Jeeze can someone who has a lowered car or stock car (perferably lowered becuase then it will work either way) with alcoas and has 275/35 295/35 comment on them? Link to comment Share on other sites More sharing options...
jerseygator Posted October 4, 2012 Report Share Posted October 4, 2012 I tried 295/35 20's on the rear at the Tire rack when I got mine. They stuck out of the Fender about 3/4". It didn't look good, and it would definitely rub when I lower my car. It may have rubbed anyway on a large bump or expansion joint. I told them to go with the 285/35's instead. These were Mich Pilot Super Sports. I went with 265/35 on the Front and they look fine. I love the tires! +1 I have 295/35's on the rear. With Nitto Invos. They stick out and rub on big ruts or uphill turns. I bought them this way used and had no idea. Want to lower it and can't. And it does affect speedometer. Link to comment Share on other sites More sharing options...
svt13 Posted October 4, 2012 Author Report Share Posted October 4, 2012 +1 I have 295/35's on the rear. With Nitto Invos. They stick out and rub on big ruts or uphill turns. I bought them this way used and had no idea. Want to lower it and can't. And it does affect speedometer. Ok good info!. Now we need someone to confirm if the same thing happens with michelin pilot super sport tires. Probably does. It seems then the best size for lowered and stock cars then is 265/35 and 285/35. Link to comment Share on other sites More sharing options...
Snoopy49 Posted October 4, 2012 Report Share Posted October 4, 2012 I am starting to rethink the purchase of these wheels. I might be better off getting wheels that actually fit the car and don't require alterations to make them work. I think they are one of the best looking wheels for the GT500's, but without modifications, they seem to be more show than go. Link to comment Share on other sites More sharing options...
svt13 Posted October 4, 2012 Author Report Share Posted October 4, 2012 I am starting to rethink the purchase of these wheels. I might be better off getting wheels that actually fit the car and don't require alterations to make them work. I think they are one of the best looking wheels for the GT500's, but without modifications, they seem to be more show than go. Well this thread is for finding out the optimal tire sizes. Obviously if you go with what shelby suggests you won't have any problems. But we are seeing how far we can push the envelope without having problems as well. Link to comment Share on other sites More sharing options...
Iceman5000 Posted October 4, 2012 Report Share Posted October 4, 2012 I am starting to rethink the purchase of these wheels. I might be better off getting wheels that actually fit the car and don't require alterations to make them work. I think they are one of the best looking wheels for the GT500's, but without modifications, they seem to be more show than go. I don't see what the problem is. 285/35 20 R. 265/35 20. F. work fine, can't tell the difference from stock, and the speedo is right on the money. No modifications needed at all. I'm running those right now. Link to comment Share on other sites More sharing options...
jerseygator Posted October 4, 2012 Report Share Posted October 4, 2012 Well this thread is for finding out the optimal tire sizes. Obviously if you go with what shelby suggests you won't have any problems. But we are seeing how far we can push the envelope without having problems as well. Exactly. I have a stock set of rims for my Hoosier Racing tires. Next go round I will get the narrower tires. Time to go burn some rubbber! :burnout: Link to comment Share on other sites More sharing options...
svt13 Posted October 4, 2012 Author Report Share Posted October 4, 2012 I don't see what the problem is. 285/35 20 R. 265/35 20. F. work fine, can't tell the difference from stock, and the speedo is right on the money. No modifications needed at all. I'm running those right now. I believe this is the ideal set up. I talked with a guy named Paul someoen reccommended on another forum to me (forgot the company name) but he does a lot of stuff with mustangs and tire fitments. He said when you go wider on these rims you can run into 3 problems. That is the rubbing, lowering, and then speedo and such problems. Said when you push the envelope you usually can get 2 out of the 3 right and have to make modifications for the 3rd. Some guys get lucky to get all 3. But basically your throwing the dice. So to give clear information to everyone if you are going to lower your car and run alcoas the widest you can go without having any problems no matter what you do is 265/35 and 285/35. Anything wider MAY require modifications. Again your rolling the dice at that point. Now can someone explain to me why the TPMS sensor for a 13 can not physically work on an alcoa rim? Link to comment Share on other sites More sharing options...
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