ShelbyKR664 Posted March 2, 2014 Report Share Posted March 2, 2014 I just installed my new 20" x 9 " Alcoa's on 275/35/20 on all four corners yesterday. I was super excited get them cleaned up and take some pictures. While doing so this morning, I noticed a offset issue. The back driver's side was sticking out further than the passenger side. After measuring, they are a full 1/4" off. The fronts are off as well but only slightly. The 18" OEM Alcoa's did not have this issue. Is it possible the new Alcoa's have different offsets????? I have never heard of this happening. Help! Link to comment Share on other sites More sharing options...
JeffJ Posted March 2, 2014 Report Share Posted March 2, 2014 If you bolt up your stock tires, I bet you would measure the exact same difference. However, you never noticed with the wheels up under the fenders. You're KR is lowered just slightly compared to a factory GT500. When you lower any mustang, the single length panhard bar will push the rear end over to the left. Just physics. If you want your rear end to be perfectly centered under your car, you need to get an adjustable panhard bar to move your rear back over to the right a bit. Here's what you need: http://www.shelbystore.com/product-p/z25-s5ma-4264-a.htm Link to comment Share on other sites More sharing options...
ShelbyKR664 Posted March 2, 2014 Author Report Share Posted March 2, 2014 Jeff, thanks for the info. I will definitely look into it. I want to upgrade to a watts link eventually. Link to comment Share on other sites More sharing options...
UOP Shadow Posted July 9, 2014 Report Share Posted July 9, 2014 We have the 10" wheels in the back wrapped in 295/35/20 Invos on our stock suspension 2013 GT500. They stick out on the drivers side more than on the passenger side. Adjustable pan-hard is the way fix it. Link to comment Share on other sites More sharing options...
Robert M Posted July 13, 2014 Report Share Posted July 13, 2014 I just installed my new 20" x 9 " Alcoa's on 275/35/20 on all four corners yesterday. I was super excited get them cleaned up and take some pictures. While doing so this morning, I noticed a offset issue. The back driver's side was sticking out further than the passenger side. After measuring, they are a full 1/4" off. The fronts are off as well but only slightly. The 18" OEM Alcoa's did not have this issue. Is it possible the new Alcoa's have different offsets????? I have never heard of this happening. Help! photo 21.JPGDriverSide.jpgphoto 31.JPGphoto 41.JPG Depending upon the specific brand of tire 275/35's will have a sidewall bulge on a 9" Alcoa that will always be a little bit past the fender on each side once you get the axle centered. Using a 275/35 on a 10" Alcoa flattens the sidewall a little more and keeps the tire even with the fender lip instead of beyond, and when using the 10" Alcoa's on the front, the tires can be tilted in a little more at the top if needed, but still be within Ford alignment specs. Flattening the sidewall is the key to not sticking out with the Alcoa's once the axle is centered. Shown below is a 275/35 on a 10" Alcoa, it fits very nicely on the front of my car. <<The reason why I mention the front is because many people are still not aware that the 10" Alcoa is a very nice fit on the front of a GT500, they think it is only a rear wheel size/offset only. R Link to comment Share on other sites More sharing options...
ShelbyKR664 Posted July 13, 2014 Author Report Share Posted July 13, 2014 Robert, thanks for the information. I did install the adj panhard bar and it did help center the axle. I will check out the sidewall issue you are referring to. I put the HRTz3's on there to start. Thanks again for your comments. Link to comment Share on other sites More sharing options...
Robert M Posted July 13, 2014 Report Share Posted July 13, 2014 Robert, thanks for the information. I did install the adj panhard bar and it did help center the axle. I will check out the sidewall issue you are referring to. I put the HRTz3's on there to start. Thanks again for your comments. I want to see pictures. I'll bet that 20" Alcoa set-up looks Great on your car!!! You will probably have minimal bulge beyond the rear fender lip by the measurements you showed in the pictures above, maybe 1/8" to 3/16" on each side when the axle is centered? A slight amount of tire bulge past the lip is acceptable, it is when the tread surface also gets out beyond the fender lip that the tire wheel combo starts to look like "it really does not fit properly". R Link to comment Share on other sites More sharing options...
KB12 Cobra Posted February 20, 2015 Report Share Posted February 20, 2015 Depending upon the specific brand of tire 275/35's will have a sidewall bulge on a 9" Alcoa that will always be a little bit past the fender on each side once you get the axle centered. Using a 275/35 on a 10" Alcoa flattens the sidewall a little more and keeps the tire even with the fender lip instead of beyond, and when using the 10" Alcoa's on the front, the tires can be tilted in a little more at the top if needed, but still be within Ford alignment specs. Flattening the sidewall is the key to not sticking out with the Alcoa's once the axle is centered. Shown below is a 275/35 on a 10" Alcoa, it fits very nicely on the front of my car. <<The reason why I mention the front is because many people are still not aware that the 10" Alcoa is a very nice fit on the front of a GT500, they think it is only a rear wheel size/offset properly Thanks RobertM for the insight about the Alcoas, I've been debating about going with michelin pilot super sports in either a 285/35 or 275/35 for the rear and 255/35 or 265/35 for the front on my fifty year Alcoas. I hate that bulge that some people get with certain brand tires, I also don't like a tire that has a side wall that looks too tall because it ends up not looking "right" on the car and I want to avoid that. My car is stock height so I doubt I would have an issue with the axel not being centered, but I'll probably encounter that problem when I eventually do lower the ride height of my 2012 GT500 svtpp R Link to comment Share on other sites More sharing options...
KB12 Cobra Posted February 20, 2015 Report Share Posted February 20, 2015 I want to see pictures. I'll bet that 20" Alcoa set-up looks Great on your car!!! You will probably have minimal bulge beyond the rear fender lip by the measurements you showed in the pictures above, maybe 1/8" to 3/16" on each side when the axle is centered? A slight amount of tire bulge past the lip is acceptable, it is when the tread surface also gets out beyond the fender lip that the tire wheel combo starts to look like "it really does not fit properly". R Sorry I totally posted my response inside your quote Link to comment Share on other sites More sharing options...
Robert M Posted February 24, 2015 Report Share Posted February 24, 2015 Sorry I totally posted my response inside your quote ^^^No problem. This past weekend I saw an Alcoa install that had 275/35 MPSS front (9") and 295/35 MPSS rear (10") and that tire combination really seemed to fit these wheels nicely, and also the car. The tire bulge appeared to be identical for the tire sizes and rim widths, and the tires looked nice with the fender lip profiles. I was not aware of the MPSS in the 275/35/20 size, but that was the size this owner claimed he had on the front 9" Alcoa's. R Link to comment Share on other sites More sharing options...
KB12 Cobra Posted February 24, 2015 Report Share Posted February 24, 2015 ^^^No problem. This past weekend I saw an Alcoa install that had 275/35 MPSS front (9") and 295/35 MPSS rear (10") and that tire combination really seemed to fit these wheels nicely, and also the car. The tire bulge appeared to be identical for the tire sizes and rim widths, and the tires looked nice with the fender lip profiles. I was not aware of the MPSS in the 275/35/20 size, but that was the size this owner claimed he had on the front 9" Alcoa's. R 275/35/20 is an unusual size for the front 9" Alcoa, usually people go with that size in the rear 10", in your opinion at what size tire does the MPSS start to bulge over the Alcoa lip on the 10" rear? Link to comment Share on other sites More sharing options...
Robert M Posted February 24, 2015 Report Share Posted February 24, 2015 275/35/20 is an unusual size for the front 9" Alcoa, usually people go with that size in the rear 10", in your opinion at what size tire does the MPSS start to bulge over the Alcoa lip on the 10" rear? Below is a picture of a 275/35/20 Michelin Pilot Sport PS2 (before the MPSS) on a 9" Alcoa. I would guess that these PS2's are probably similar in width to the MPSS in the same size? They really don't fit bad at all. Also shown in this picture is a 335/30 PS2 on a 12" Alcoa...............<<They did get a little bulgy beyond the rear fender lip. Here is a more straight down view of the 275/35/20 Michelin Pilot Sport PS2 on a 9" Alcoa.............It really fits quite nice......... ^^^^A 295/35/20 will fit/bulge pretty much this same way on a 10" Alcoa. R Link to comment Share on other sites More sharing options...
KB12 Cobra Posted February 24, 2015 Report Share Posted February 24, 2015 Below is a picture of a 275/35/20 Michelin Pilot Sport PS2 (before the MPSS) on a 9" Alcoa. I would guess that these PS2's are probably similar in width to the MPSS in the same size? They really don't fit bad at all. Also shown in this picture is a 335/30 PS2 on a 12" Alcoa...............<<They did get a little bulgy beyond the rear fender lip. R Yeah that 275/35/20 doesn't look bad at all on a Alcoa 9" but that size is a bit unusual for the front, you usually see that size for the rear 10" I don't know if I wanna put that size on my front 9" Alcoa, I was thinking of maybe 255 or 265/35/20 for the front and then 275 or 285/35/20 for the rear. I know those are probably the most common sizes for the Alcoas, What are you thoughts about those sizes? Link to comment Share on other sites More sharing options...
Robert M Posted February 24, 2015 Report Share Posted February 24, 2015 Yeah that 275/35/20 doesn't look bad at all on a Alcoa 9" but that size is a bit unusual for the front, you usually see that size for the rear 10" I don't know if I wanna put that size on my front 9" Alcoa, I was thinking of maybe 255 or 265/35/20 for the front and then 275 or 285/35/20 for the rear. I know those are probably the most common sizes for the Alcoas, What are you thoughts about those sizes? While you were replying I added another view of the front, check it out above. I moved my 10" Alcoa to the front, in fact I may have been the first to do so because 6 years ago everyone said that they would not fit, the offset was wrong, but that proved to be wrong. I like a 275 tire on the front, the 255 is a little narrow for these cars as heavy nosed as they are, and a 265 may work fine, but I have never experimented with that size on the front. To me, the 275/35 is a little narrow on the 10" rim for a rear application and for proportion of tire bulge matching front and rear, the difference between 275 and 295 (20mm) and 9" to 10" (26mm) work well for matching. Other sizes, narrower or wider, can start down the path of the tire bulge not matching as well front and rear. You see how well the 275/35 fits that 9" Alcoa, a 255 would start to get narrow looking IMHO, and my car came with the 255 and 275 tire combination when I received it back from Shelby. To start with, a 275 tire installed on the rear of a car that originally had a 285 tire factory installed while also adding 225hp (500 to 725) seemed a little strange, but that is the way they came. I am not saying the 255-275 tire combination does not fit the rims, they do, but they are on the narrower side of the range that can fit those rim sizes and still look like the fit properly. R Link to comment Share on other sites More sharing options...
tomshep Posted February 24, 2015 Report Share Posted February 24, 2015 Robert, I agree with all of your comments on 9" vs 10" and your tire size recommendations. I am running 9" CS1 rims with a 275/35 Nitto Invo. Yours have a nice round shoulder to them on 9". Mine are much more squared off on the tread face compared to yours with a flatter sidewall. I will post a pic when I get some. Tom Link to comment Share on other sites More sharing options...
KB12 Cobra Posted February 24, 2015 Report Share Posted February 24, 2015 While you were replying I added another view of the front, check it out above. I moved my 10" Alcoa to the front, in fact I may have been the first to do so because 6 years ago everyone said that they would not fit, the offset was wrong, but that proved to be wrong. I like a 275 tire on the front, the 255 is a little narrow for these cars as heavy nosed as they are, and a 265 may work fine, but I have never experimented with that size on the front. To me, the 275/35 is a little narrow on the 10" rim for a rear application and for proportion of tire bulge matching front and rear, the difference between 275 and 295 (20mm) and 9" to 10" (26mm) work well for matching. Other sizes, narrower or wider, can start down the path of the tire bulge not matching as well front and rear. You see how well the 275/35 fits that 9" Alcoa, a 255 would start to get narrow looking IMHO, and my car came with the 255 and 275 tire combination when I received it back from Shelby. To start with, a 275 tire installed on the rear of a car that originally had a 285 tire factory installed while also adding 225hp (500 to 725) seemed a little strange, but that is the way they came. I am not saying the 255-275 tire combination does not fit the rims, they do, but they are on the narrower side of the range that can fit those rim sizes and still look like the fit properly. R RobertM I checked out the picture that you added, those pictures are a great visual reference. Thanks for adding them and for such a comprehensive comparison of tire and rim sizes for the Alcoa rims. I also agree with you about the rim and tire sizes, I am more confident about choosing wider tires for my set of Alcoas and not as hesitant for the fear of tire bulge when choosing a wider tire. It definently makes since opting for a larger tire especially when it came from Ford with larger tires and in your case converting to a higher HP supersnake. It's because of smart and insightful members like yourself I choose to be a part of this forum, thanks! Link to comment Share on other sites More sharing options...
07gt500conv Posted February 24, 2015 Report Share Posted February 24, 2015 I went with the 275/35 on the front also. Also, went to 315/35 on the rear. I love this combo. Link to comment Share on other sites More sharing options...
Robert M Posted February 25, 2015 Report Share Posted February 25, 2015 RobertM I checked out the picture that you added, those pictures are a great visual reference. Thanks for adding them and for such a comprehensive comparison of tire and rim sizes for the Alcoa rims. I also agree with you about the rim and tire sizes, I am more confident about choosing wider tires for my set of Alcoas and not as hesitant for the fear of tire bulge when choosing a wider tire. It definently makes since opting for a larger tire especially when it came from Ford with larger tires and in your case converting to a higher HP supersnake. It's because of smart and insightful members like yourself I choose to be a part of this forum, thanks! The main concern with the tire selection is going to be "if" the brand tire you are buying runs wider or narrower in its measurement. Unfortunately a 275/35 is not a 275/35 across the tire spectrum as it relates to width and height, and this goes for any size across the tire brands. One brand tire may look fine when mounted on a 9" or 10" Alcoa, but when you buy a different brand in the same size, they stick out beyond the fender well. The whole "10" on the front" thing was to get back some of the size lost when a 9" Alcoa was installed on the front, downsizing form the original 9.5" GT500 wheel that was originally installed on the car when it was new. !0" on the front got the car back to its original width on the front, and added 1/2". <<<This was usually only an thought for an owner was going to have a pair widened beyond 10" for the rear, they now had an option to keep the 9" Alcoa on the front and widen the 10" OR move the 10" to the front and widen the 9" for the rear. This is if they bought a 9"/10" Alcoa combination to start with. The option of installing the 10" up front changed everything. R Link to comment Share on other sites More sharing options...
Robert M Posted February 25, 2015 Report Share Posted February 25, 2015 I went with the 275/35 on the front also. Also, went to 315/35 on the rear. I love this combo. ^^^^COOL!! What rim width did you use on the rear? I see you are in Apopka, I'm in Lakeland. R Link to comment Share on other sites More sharing options...
KB12 Cobra Posted February 26, 2015 Report Share Posted February 26, 2015 The main concern with the tire selection is going to be "if" the brand tire you are buying runs wider or narrower in its measurement. Unfortunately a 275/35 is not a 275/35 across the tire spectrum as it relates to width and height, and this goes for any size across the tire brands. One brand tire may look fine when mounted on a 9" or 10" Alcoa, but when you buy a different brand in the same size, they stick out beyond the fender well. Yeah, I see what your saying. I read somewhere on this forum that the MPSS run a bit wider across then other tire brands, it was something like a 275/35/20 MPSS is as wide as some other brand (I can't remember the tire brand) 285/35/20. Have you ever encountered that? Link to comment Share on other sites More sharing options...
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