Mild square setup, no poke

[smithhead]

There are a million threads here, mostly about the largest sizes that can be fitted. I'm just trying to figure out a more reasonable setup than what I have -- a base GT, 235/50r18 (27.25" diameter), stock suspension.

• Square
• No rubbing concerns
• No poke
• Preferably no spacers
• Reasonable ride, etc
• Reasonable cost

It seems the largest size that generally fits is 285/35r19 on a 10" wheel, although the diameter is somewhat smaller. Others go for the 275/40r19 but it's a bit larger. The closest to my stock diameter is 265/40r19, which I never see mentioned and is not nearly as widely available. And both of those seem to go best on a 9.5" wheel, which I don't see many of.

In some ways I wouldn't mind sticking with 18" wheels, as I'd like to keep my current setup for winter, although then I couldn't upgrade my brakes if I wanted to. But there aren't many options there either.

I do have Forscan so I guess I can adjust the tire diameter though. So what is the best all-around (especially reasonable cost) size to go with?

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[NightmareMoon]

Nothing wrong with 18” or 265s on 9.5” wheels. With the right 18” wheel, the Brembos brakes fit, so it doesnt need to rule out a brake upgrade, but sure a lot of 18” wheels won’t work. (Apex SM-10 or EC-7 for example do work with the brembos are are great wheels), although I think people usually get those in 10” sizes.

With a 10” wheel you can safely run anything from a 285 to a 255 tire. 265 the max wheel width would be a 10.5” or less, but if you price compare the narrower 18” sizes may not actually be that much cheaper than 19” 285s, it just depends.

Me, I went with 285 on 19x10 wheels and haven’t looked back.

 

[MidwayJ]

I used to run 275/40r19 on 19x9.5 et33 square and now I'm running 285/35r19 on 19x10 et37 square. Both work very well. I might even go back to 275/40 on my 19x10s when the current tires wear out.

 

[smithhead]

Nothing wrong with 18” or 265s on 9.5” wheels. With the right 18” wheel, the Brembos brakes fit, so it doesnt need to rule out a brake upgrade, but sure a lot of 18” wheels won’t work. (Apex SM-10 or EC-7 for example do work with the brembos are are great wheels), although I think people usually get those in 10” sizes.

With a 10” wheel you can safely run anything from a 285 to a 255 tire. 265 the max wheel width would be a 10.5” or less, but if you price compare the narrower 18” sizes may not actually be that much cheaper than 19” 285s, it just depends.

Me, I went with 285 on 19x10 wheels and haven’t looked back.

I used to run 275/40r19 on 19x9.5 et33 square and now I'm running 285/35r19 on 19x10 et37 square. Both work very well. I might even go back to 275/40 on my 19x10s when the current tires wear out.

Thanks both for the good info.

I actually created a spreadsheet with all the stock specs, as well as measured the clearance on mine, and calculated what widths and offsets should fit for sure (except I don't know which ones poke, the Mach 1 HP stick out a lot more than the others). Along with all the tire specs. Doesn't mean something else wouldn't fit though. I just like doing spreadsheets.

When I first did it I thought I found that the 10" fits exactly with a 35 offset, but I changed something and now it doesn't add up, but if it works it works. And really surprised the 37 fits, let alone the 40 that Apex recommends. Seems like you'd need a 5mm spacer.

I usually like to stick close to the mfgs measured rim width, and don't like to go too wide as I want a little protection. But I read the article that was mentioned in another thread on sizing wheels based on Tirerack's tread width, which is supposedly a consistent measurement. I used the PS4S as a sample and noticed something really interesting:

The 255 is actually slightly wider than the 265, and the 275 is slightly wider than the 285 which is slightly wider than the 295. The 265 and 295 are a Mercedes OEM size so might have a different shoulder. Not sure why the 275 and 285 don't make sense though, except one is 40 series and the other 35. The 295 is closer to stock diameter and might actually fit, although maybe not with a different tire.

Anyway, I guess I'll see what wheels are out there right now and go from there.

 

[thompsje]

This is my car today. I'm running Michelin PS4S 275/35-19s on Apex EC-7s in 19x10 with the 40mm offset. I *just* finished installing Steeda minimum drop springs and Bilstein B6 shocks all around (1/4" spacer in the rear). It might not be as dropped as some people would care for, but it's about as low as I would want to go living in the northeast and this being my DD.

It was a non-PP car, so even with the minimum drop springs I went down between 1" to 1-1/4" in the front, and about the equivalent in the rear minus the spacers. I've got less than 100 miles on it since the suspension and it needs an alignment, but there's no rubbing even at full lock. The fronts are *close* to the struts, but they clear, and looking straight down from the fender tops, there's no poke.

 

[shogun32]

When I first did it I thought I found that the 10" fits exactly with a 35 offset, but I changed something and now it doesn't add up, but if it works it works. And really surprised the 37 fits, let alone the 40 that Apex recommends. Seems like you'd need a 5mm spacer.

10et40 fits to the inside fine (4mm to spare) and can be moved 5mm outboard and still remain this side of flush.

 

[NightmareMoon]

Thanks both for the good info.

I actually created a spreadsheet with all the stock specs, as well as measured the clearance on mine, and calculated what widths and offsets should fit for sure (except I don't know which ones poke, the Mach 1 HP stick out a lot more than the others). Along with all the tire specs. Doesn't mean something else wouldn't fit though. I just like doing spreadsheets.

When I first did it I thought I found that the 10" fits exactly with a 35 offset, but I changed something and now it doesn't add up, but if it works it works. And really surprised the 37 fits, let alone the 40 that Apex recommends. Seems like you'd need a 5mm spacer.

I usually like to stick close to the mfgs measured rim width, and don't like to go too wide as I want a little protection. But I read the article that was mentioned in another thread on sizing wheels based on Tirerack's tread width, which is supposedly a consistent measurement. I used the PS4S as a sample and noticed something really interesting:

The 255 is actually slightly wider than the 265, and the 275 is slightly wider than the 285 which is slightly wider than the 295. The 265 and 295 are a Mercedes OEM size so might have a different shoulder. Not sure why the 275 and 285 don't make sense though, except one is 40 series and the other 35. The 295 is closer to stock diameter and might actually fit, although maybe not with a different tire.

Anyway, I guess I'll see what wheels are out there right now and go from there.

Manufacturer spec tires can vary from the usual dimensions, so probably ignore those Mercedes spec tires.

Also pay attention to the listed wheel width that Tire Rack was using when getting that section width spec. If they tested a 255 on a 9.5” wheel but a 265 on a 9”, that will account for the difference in measured widths.

Some people report clearance issues with 10” ET40 wheels at the strut, but a lot of others don’t. I’d be prepared to run a 5mm spacer if I had ET40 10” wheels, just in case.

 

[Rick#7]

If you're concerned about speedometer error going to a 275/40r19, don't be, the amount of difference that change would cause isn't really that much. It's common for a car to leave the factory with a small amount of error to begin with. My car actually shows 2 mph faster than my GPS reading at 60, so a slightly taller tire would actually correct the factory speedo error

 

[smithhead]

10et40 fits to the inside fine (4mm to spare) and can be moved 5mm outboard and still remain this side of flush.

Some people report clearance issues with 10” ET40 wheels at the strut, but a lot of others don’t. I’d be prepared to run a 5mm spacer if I had ET40 10” wheels, just in case.

Thanks, good to know there is plenty of clearance even with 10" wheels.

I hadn't looked at the GT500 wheels; looks like they extend 11 mm farther inward than the Mach 1 wheels.

 

[smithhead]

This is my car today. I'm running Michelin PS4S 275/35-19s on Apex EC-7s in 19x10 with the 40mm offset. I *just* finished installing Steeda minimum drop springs and Bilstein B6 shocks all around (1/4" spacer in the rear). It might not be as dropped as some people would care for, but it's about as low as I would want to go living in the northeast and this being my DD.

It was a non-PP car, so even with the minimum drop springs I went down between 1" to 1-1/4" in the front, and about the equivalent in the rear minus the spacers. I've got less than 100 miles on it since the suspension and it needs an alignment, but there's no rubbing even at full lock. The fronts are *close* to the struts, but they clear, and looking straight down from the fender tops, there's no poke.

Looks great.

 

[smithhead]

Also pay attention to the listed wheel width that Tire Rack was using when getting that section width spec. If they tested a 255 on a 9.5” wheel but a 265 on a 9”, that will account for the difference in measured widths.

I assume tire rack uses the mfg specified measuring width, which is 9 for the 255 and 9.5 for the 265. But I don't think that impacts the tread width as much as the section width anyway.

 

[smithhead]

If you're concerned about speedometer error going to a 275/40r19, don't be, the amount of difference that change would cause isn't really that much. It's common for a car to leave the factory with a small amount of error to begin with. My car actually shows 2 mph faster than my GPS reading at 60, so a slightly taller tire would actually correct the factory speedo error

I'm more concerned with odometer error; speedometers are usually intentionally high, whereas the odometer is not. But it's still not a lot, and I'd rather be off that way than the other way.

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