[ShaneFalco]

I have a 2017 340GT with the 400M wheels with the stock 225/50R18 Contis. (400M is 18x8 ET34)

I bought some BMW 351M take off rims, 19x8.5 ET33, square setup. I'm going to put the Continental DWS06 tire on them, just need to decide between the 255/40R19 or the 245/40R19. Purely based on diameter, the stock tire falls in between them, and they both are within 1%, so I don't have concerns on gear ratios and speedo.

I'm leaning toward the 255 for a few reasons:
-slightly larger sidewall which would provide a bit more cushion against potholes.
-fill out the fenderwell a bit more being slightly larger
-provide a bit more width to protect against curb damage (I park on the street).
-avoid the stretched tire look. Not to say that a 245/40 would look stretched, I just hate the stretched tire look.

My main concerns:
-Will the fronts clear the strut on the inside?
-Will they have a 'squishy' feeling when steering, since there's slightly more sidewall?

Anybody have any experience with a 255/40 R19 on the GT?

[Billfitz]

The width of the 255 could cause a number of problems.

[ShaneFalco]

Billfitz, care to elaborate?

[Billfitz]

There are a number of things that an overly wide tire can hit, including the wheel well liners. I wouldn't use a tire size that wasn't available as OEM. My manual shows 225-45/R19 as the largest offered for the front. The largest rear are 255-40/R19, which can be larger because the rear wheels don't steer.

[mikelo_74]

I have a GT with 245/40 in the fronts and 275/35 in the rears with the 437m in 19" and fits good.

[dagr8_1_F34]

Originally Posted by mikelo_74

I have a GT with 245/40 in the fronts and 275/35 in the rears with the 437m in 19" and fits good.

could you post some pics?

[mikelo_74]

[Sportstick]

Originally Posted by mikelo_74

I have a GT with 245/40 in the fronts and 275/35 in the rears with the 437m in 19" and fits good.

Would you please be willing to take a look at your set-up and give an opinion?

For my needs, I am looking for a new set of run flats on my original OEM 18" wheels. The only ones well rated only come close to fitting with 245/50-18. The tread width is the same as yours, but the overall diameter is almost one inch greater due to being a larger 50-series profile. As you look outward from the wheel center, with the wheels straight or fully turned, do you see space for another half-inch of clearance in all directions?

Thanks so much!

[Billfitz]

Summer or A/S? I've just come across these, which come in 245/40R18 and 245/45R18. They're ranked as the #2 A/S at Tire Rack, and are a lot less expensive than the #1 rated Michelin CrossClimate+. The downside is that they're only available on-line. https://www.tirerack.com/tires/tires...TPXL&tab=Sizes

[Sportstick]

Originally Posted by Billfitz

Summer or A/S? I've just come across these, which come in 245/40R18 and 245/45R18. They're ranked as the #2 A/S at Tire Rack, and are a lot less expensive than the #1 rated Michelin CrossClimate+. The downside is that they're only available on-line. https://www.tirerack.com/tires/tires...TPXL&tab=Sizes

Unless I missed something, those don't seem to be run flat. The all-season run flat tires I am attempting to verify for fit are:

https://www.tirerack.com/tires/tires...4PZP&tab=Sizes

in 245/50-18 size. According to 1010tires.com calculator, they are "green" for a minor difference in comparable size. What is not yet clear is the fit on the 3 Series GT.

[ShaneFalco]

Originally Posted by mikelo_74

Mikelo,
Is that a stock suspension? or do you have aftermarket setup installed? Looks slightly lower than mine, but maybe it's just the bright sunlight, white paint, and dark shadow of the wheel well fooling me!

[Billfitz]

Originally Posted by Sportstick

Unless I missed something, those don't seem to be run flat.

Sorry, they're not run flat. They are what's now at the top of my list if I get tires any time soon. If I was to stay with run flat I'd get Bridgestone Driveguard, which are consistently among the highest rated run flats despite their relatively low cost. The MXM4ZP is the highest rated run flat, but the Quatrac Pro beats it in every category at almost half the price, saving you more than enough to get a temp spare if you don't already have one. I've got one, which is a big part of my decision.

[Sportstick]

Originally Posted by Billfitz

Sorry, they're not run flat. They are what's now at the top of my list if I get tires any time soon. If I was to stay with run flat I'd get Bridgestone Driveguard, which are consistently among the highest rated run flats despite their relatively low cost. The MXM4ZP is the highest rated run flat, but the Quatrac Pro beats it in every category at almost half the price, saving you more than enough to get a temp spare if you don't already have one. I've got one, which is a big part of my decision.

Thanks. It’s not about cost. It’s about logistics of the temp and jack taking up space but wanting it there always for the unforeseen/unexpected need. In short, with no good underfloor storage location, I’m stuck with run flats and DriveGuard reviews are mediocre on Tire Rack.

[mikelo_74]

Originally Posted by Sportstick

Would you please be willing to take a look at your set-up and give an opinion?

For my needs, I am looking for a new set of run flats on my original OEM 18" wheels. The only ones well rated only come close to fitting with 245/50-18. The tread width is the same as yours, but the overall diameter is almost one inch greater due to being a larger 50-series profile. As you look outward from the wheel center, with the wheels straight or fully turned, do you see space for another half-inch of clearance in all directions?

Thanks so much!

I´ll take a look tomorrow, here is already night

[mikelo_74]

Originally Posted by Sportstick

Would you please be willing to take a look at your set-up and give an opinion?

For my needs, I am looking for a new set of run flats on my original OEM 18" wheels. The only ones well rated only come close to fitting with 245/50-18. The tread width is the same as yours, but the overall diameter is almost one inch greater due to being a larger 50-series profile. As you look outward from the wheel center, with the wheels straight or fully turned, do you see space for another half-inch of clearance in all directions?

Thanks so much!

Originally Posted by ShaneFalco

Mikelo,
Is that a stock suspension? or do you have aftermarket setup installed? Looks slightly lower than mine, but maybe it's just the bright sunlight, white paint, and dark shadow of the wheel well fooling me!

Is the standard suspension in europe. I want put coilovers, only lowering with springs is not enough for me

[Billfitz]

Originally Posted by Sportstick

Thanks. It’s not about cost. It’s about logistics of the temp and jack taking up space

I've got a jack, pump and repair kit under the floor. I realized that if I was on a trip out of town that I wouldn't want to be fixing a flat on the side of the road, so for those longer trips I got the temp spare. The fix it kit has paid for itself. I picked up a nail twice in the last three years, luckily close to home, so it was no biggy to fix both times.

[KRS_SN]

f34 has poor road noise insulation and in my case the confort increased and noise decreased the moment i switched out of runflats to normal tyres.
i had a flat tyre and had to pay exorbitant rate to get it fixed within the hour but im happy with the trade off.

[Fade_The_Public]

Originally Posted by ShaneFalco

I have a 2017 340GT with the 400M wheels with the stock 225/50R18 Contis. (400M is 18x8 ET34)

I bought some BMW 351M take off rims, 19x8.5 ET33, square setup. I'm going to put the Continental DWS06 tire on them, just need to decide between the 255/40R19 or the 245/40R19. Purely based on diameter, the stock tire falls in between them, and they both are within 1%, so I don't have concerns on gear ratios and speedo.

I'm leaning toward the 255 for a few reasons:
-slightly larger sidewall which would provide a bit more cushion against potholes.
-fill out the fenderwell a bit more being slightly larger
-provide a bit more width to protect against curb damage (I park on the street).
-avoid the stretched tire look. Not to say that a 245/40 would look stretched, I just hate the stretched tire look.

My main concerns:
-Will the fronts clear the strut on the inside?
-Will they have a 'squishy' feeling when steering, since there's slightly more sidewall?

Anybody have any experience with a 255/40 R19 on the GT?

19/255/40 ????

I don't have the data on this, but I can't imagine that won't rub. I'd bet big money this can't be done without modification.

[Billfitz]

Originally Posted by KRS_SN

i had a flat tyre and had to pay exorbitant rate to get it fixed within the hour but im happy with the trade off.

95% of flats are easily fixed with one of these, or something similar:
https://www.amazon.com/dp/B07MR5FX8M..._t3_B07VK6ZSDT

Keep a small bottle of kid's bubble blowing solution in the boot, use it to go over the repaired spot to see if it's fully sealed. It might take more than one plug. One of my tires I repaired a year ago, another two years ago, both are still as tight as a drum.

[KRS_SN]

Originally Posted by Billfitz

95% of flats are easily fixed with one of these, or something similar:
https://www.amazon.com/dp/B07MR5FX8M..._t3_B07VK6ZSDT

Keep a small bottle of kid's bubble blowing solution in the boot, use it to go over the repaired spot to see if it's fully sealed. It might take more than one plug. One of my tires I repaired a year ago, another two years ago, both are still as tight as a drum.

thanks i will look into this!

[ShaneFalco]

Originally Posted by Billfitz

95% of flats are easily fixed with one of these, or something similar:
https://www.amazon.com/dp/B07MR5FX8M..._t3_B07VK6ZSDT

Keep a small bottle of kid's bubble blowing solution in the boot, use it to go over the repaired spot to see if it's fully sealed. It might take more than one plug. One of my tires I repaired a year ago, another two years ago, both are still as tight as a drum.

Yes, having one of these is necessary, no matter if you have run flats or standard tires. 3 of my current Conti runflats have plugs in them. BMW dealer told me they can't plug/patch a runflat, because "it's not safe". One of these plugs has been in for over 15,000 miles, no leaks, no issues. On my previous Audi with Continental DWS tires, I had a plug for 30,000 mi, no issues. A plug kit, if not a life-saver, is definitely a dollar saver!

[ShaneFalco]

Originally Posted by Fade_The_Public

19/255/40 ????

I don't have the data on this, but I can't imagine that won't rub. I'd bet big money this can't be done without modification.

Exactly my thoughts! There's consensus from enough guys that a 245/40/19 on 8.5 rim will be OK on a stock setup with no modifications, spacers, etc... I was hoping somebody had a definitive answer on the 255/40/19, but looks like we'll continue to speculate! I'm going to play it safe, and go with the 245.