New rear tyre help.

[Captain Greg]

Hi Guys
please give me your thoughts, I got a deal on a new set of rear tyres, stock was 275/40/19 …now the new ones are 295/30/19
they will fit the wheel wel I have wheel spacers on the hub, if I am unable to recalibrate the on board computer will it still be fine?
I was bargain hunting because rear tyres don’t last long when we ride it enthusiastically so I’m hoping this will be ok?
advise appreciated ..I really don’t want to damage my car

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[NightmareMoon]

Well 295/30R19 is noticeably shorter than your front tires, so its probably going to look funny and sit a bit nose-high.

295 is also wider than you should go on a random tire on stock 9.5" wide wheels.

 

[MidnightStars]

They should fit fine, I run 305/35/R19s all-around with properly offset wheels, and no spacers. Just make sure the wheel you currently have is wide enough for the tires you received. Not all 305s are "truly 305s."

As for recalibrating your computer, I wouldn't worry too much about it, unless you're a fellow autist like me. All it will do is display a higher gauge speed vs. GPS speed, and the miles on the odometer will rack up faster than reality, but not by much. Actually, it's different enough to where I would go ahead and do it, unless you can spare the mental energy to remember to drive 5 mph faster to actually go the speed limit, and to also not mess with the shift tables. The car relies on both speed, and engine load, to decide when to shift up/down.

Recalibrating it is incredibly easy to do, just need FORScan, and the appropriate USB <-> OBDII cable to have it done.

Great tool to use: https://www.calculator.net/tire-siz...5&car2=30&cws2=19&ctype=2&x=Calculate#compare

 

[robvas]

26" is too short, I wouldn't even bother with them. You want a 285/35 19 (or 275/40 like you had, they are 1.7" taller than the ones you have now)

 

[BullittTheBlueSky]

Of all the things to be cheap on with a vehicle, tires are the last. Your entire contact with the road for all four tires combined is surprisingly tiny.

 

[Captain Greg]

Well I have the tyres , .. it would be a waste of cash not to run them ? As long as they don’t do any damage …being shorter will surely get it off the line faster ?

 

[Skye]

I'd pass on these tires. What seems like a great deal could only bring you problems. I realize you have purchased the tires. See if you can sell or donate to someone who can make good use of them.

My concerns:

- The front will effectively be lifted by .85 in / 21 mm. IDK what that's gonna look like

- In extreme examples, people who lift the front end (google "Carolina squat") have issues with oil and transmission fluid circulation. I'm not saying that's going to happen. But it's not helpful

- I try to stay within 3% of the factory tire circumference. You'd be changing more than 6% with these. That effects not only speedo, but shift points, braking, etc. If placed on the rear, it'll be akin to a rear end gear swap

- Returning to point one, a previous thread in another forum captured some odd events with the car's systems after a wheel/tire swap. I can't say if something similar will happen with your car or not

https://www.mustang7g.com/forums/threads/pre-collision-assist-cruise-control-problem.170023/

https://www.mustang7g.com/forums/threads/taller-tires-cruise-control.174753/

- Tires that are too wide or too skinny for a given rim, the tire itself doesn't work very well, performs differently than expected. The tire can be squished or stretched. Instead of a flat contact patch "_", it rests as a "U" (bulging, squished) or concave, where the center is pulled in "^" (stretched)

https://akalloys.co.uk/pages/rim-wi...2gTSyOorHJNoYgFRCCNmsPgNC6JhMnh56RpXRR-uatwc9

Edit,

"...rear tires don't last long..." I get it: you enjoy driving the car. If the tires are wearing evenly, good. If not, check the tire pressure and the alignment.

 

[glockholiday]

It won't hurt anything, your speedo will be off by like 4mph. Burnem off and then next set try to get closer to stock height

 

[obgod3]

So my GT had 255/40/19 front and 275/40/19 rear. I went with 285/35/19 front and 305/35/19 rear. The primary reason is that both those tires are as close to stock as possible in diameter. The other folks here are right, keeping the balance between front and rear is important. If you use a proper backspace like other said you wont need spacers, Im running Apex VS5‘s 19/10+40 and 19/11+52 and no rubbing on steeda minimum drop springs. But if your running stock PP1 wheels then I can see where you tire sizes are limited due to rim width. A 305 wont work on them, not well anyway.

 

[galaxy]

26" is too short, I wouldn't even bother with them. You want a 285/35 19 (or 275/40 like you had, they are 1.7" taller than the ones you have now)

dude, you gotta stop saying that. A ~26” tire is absolutely not too short for a mustang. Especially considering most looking into aftermarket tires and such are probably lowered.

The only things needed to answer the original question is the 295 is getting pretty wide for a 9.5” wheel. Dangerous? No. Ideal? Absolutely not. And your rear tire will be sorely shorter than the front which will look pretty darn dumb. The comparisons to the Carolina squat (and the ensuing complications) is quite extreme and unnecessary, but you’ll see it visually.

 

[robvas]

It is too short. 27/27.7" is the way to go and 28" or even a little bigger for the rear if you want traction

26 is tiny tire wheel gap city

 

[galaxy]

Aaahh yes, I see it now. Way too much gap on these 26.3” tires…

 

[HoldenSSVandGT350]

Aaahh yes, I see it now. Way too much gap on these 26.3” tires…

I run 305/30 square on my 350. It’s better. Looks, turn in sharpness (as if that was needed), and, the drop to 26.2” rear diameter was a nice effective gear swap as well. Good stuff.

 

[robvas]

Aaahh yes, I see it now. Way too much gap on these 26.3” tires…

Great example. You could probably fit two hands in there.

Look how much less gap there is with a 27" + tire

These are big cars and need big tires. 26" was a height more appropriate for the smaller SN95/New Edge cars.

I get it, there's a limited selection of tires and you might not be able to find the width you want in a better looking height, but there's no arguing the car doesn't look better with an inch taller tire on it.

 

[Bob Lob Law]

Not everyone wants a lowered look. I personally like the look of the 26 inch over the 27+.

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