Question about tire sizes
Thread Starter
Dr. Dave
Joined: Dec 2015
Posts: 323
Likes: 242
Question about tire sizes
I have a '16 M7SR completely stock with 65K miles. The front tires are 245/40-18 and the rears are 285/35-19. I am running Pilot Sport A/S 3 tires.
Now, to possibly soften the ride a bit I am thinking of going up to the next higher aspect ratio: 45 on front and 40 on rear. I'm pretty sure those sizes will still mount on the rims okay. And the car has quite a bit of clearance around the tires.
I'll gain a little less than 1/2" of side wall on the rear, and something else on the front. It might soften the ride a bit on the F'd-up San Diego streets.
I think it might throw the speedometer off a bit but maybe not much.
Anyone ever done something like this?
And *PLEASE*, lets keep this a technical discussion and not a flame session, okay?
Now, to possibly soften the ride a bit I am thinking of going up to the next higher aspect ratio: 45 on front and 40 on rear. I'm pretty sure those sizes will still mount on the rims okay. And the car has quite a bit of clearance around the tires.
I'll gain a little less than 1/2" of side wall on the rear, and something else on the front. It might soften the ride a bit on the F'd-up San Diego streets.
I think it might throw the speedometer off a bit but maybe not much.
Anyone ever done something like this?
And *PLEASE*, lets keep this a technical discussion and not a flame session, okay?
Racer
Joined: Jul 2019
Posts: 388
Likes: 213
From: RI
Tires do a lot more than just determine ride quality, so altering from OEM specs will "slightly throw off" a few things in terms of performance.
If you really want a softer ride, look into shocks, or different tires of the correct size. Personally, I think you asking for problems that aren't worth a (maybe) perceivable softer ride.
If you really want a softer ride, look into shocks, or different tires of the correct size. Personally, I think you asking for problems that aren't worth a (maybe) perceivable softer ride.
Racer
Joined: Apr 2020
Posts: 425
Likes: 272
From: Cape Coral,FL
Biggest issues with larger tires are clearence, speedometer/odometer and gear ratio. Weight is another factor but not a big deal on a small increase. A small increase won't affect any of these things much to say have to use a programmer or to regear. I had a 16 wrangler with 37's I had to buy a tuner to change the tire size so the speedo was correct and I changed the gears because it was a dog and wouldn't get out of 3rd gear at 60 mph. The programmer allowed me to change the gear ratio. If you use a tire calculator you can put in your exisitng size tire and what you want to go to and see how much the speedo is going to be off. As far a clearence issues thats another question either someone who has changed the tires can tell you or you do it and see for yourself. Tire calculator says you speedo is off by 2.5 mph so at 60 mph your at 62.5.
Burning Brakes
Joined: Oct 2017
Posts: 1,230
Likes: 467
From: Colorado
245/40-18 and the rears are 285/35-19 seem pretty squishy already. I'm not sure if you can stuff a bigger sidewall in there without rub. 65k miles, maybe the shocks, but I doubt that as well. I'm running 265/30/19, 305/25/20 and it's harsh - but not undriveable in our fkd up Colorado streets (I'm starting to name our potholes).
Thread Starter
Dr. Dave
Joined: Dec 2015
Posts: 323
Likes: 242
245/40-18 and the rears are 285/35-19 seem pretty squishy already. I'm not sure if you can stuff a bigger sidewall in there without rub. 65k miles, maybe the shocks, but I doubt that as well. I'm running 265/30/19, 305/25/20 and it's harsh - but not undriveable in our fkd up Colorado streets (I'm starting to name our potholes).
Thread Starter
Dr. Dave
Joined: Dec 2015
Posts: 323
Likes: 242
Tires do a lot more than just determine ride quality, so altering from OEM specs will "slightly throw off" a few things in terms of performance.
If you really want a softer ride, look into shocks, or different tires of the correct size. Personally, I think you asking for problems that aren't worth a (maybe) perceivable softer ride.
If you really want a softer ride, look into shocks, or different tires of the correct size. Personally, I think you asking for problems that aren't worth a (maybe) perceivable softer ride.
Maybe I should try some non run-flat tires first...
Drifting
Joined: Feb 2005
Posts: 1,456
Likes: 173
From: San Jose Ca
Thread Starter
Dr. Dave
Joined: Dec 2015
Posts: 323
Likes: 242
Yes you should. That will be easiest. There have been some comments about all season non run flat tires providing a smoother ride. At 65K, the shocks could be worn out, and if they are, that would soften the ride some too. I assume you don't have mag ride, because if you do, the software update may help. I don't know what an M7SR is.
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Instructor
Joined: Mar 2020
Posts: 169
Likes: 166
From: Lancaster PA
St. Jude Donor '20
Sounds simple but what psi are you running? Alot of people drive on over inflated tires which kill the ride and the tires ability to do their job.
Last edited by Braski; Aug 23, 2020 at 06:06 PM.
Melting Slicks
Joined: Aug 2017
Posts: 2,195
Likes: 2,206
From: Massachusetts
I like the idea myself. I don't like these very low-profile tires. Even a little increase in sidewall would soften the ride, and help against wheel damage when hitting potholes. Let us know if you go bigger.
You can use 'Tire Size Calculator". I found this one: https://www.tacomaworld.com/tirecalc
You can use 'Tire Size Calculator". I found this one: https://www.tacomaworld.com/tirecalc
Burning Brakes
Joined: Feb 2019
Posts: 1,234
Likes: 416
From: San Diego
I'm in San Diego also and recently got some Michelin pilot sport 4S. Keep tires at 30 cold and yes, my non run flat tires are both smoother and quieter. Funny how that works. Not cheap but the best never is =)
Racer
Joined: May 2020
Posts: 251
Likes: 125
From: Beavercreek, OH
It might not be what you want but just as people do +1, +2 on wheels to get wider aspect tires/wheel combos to keep overall diameter/circumference the same
You could do -1 and get 17 and 18 inch wheels and tires to get a larger sidewall/aspect ratio.
Little more expensive but would probably give you what you want.
You could do -1 and get 17 and 18 inch wheels and tires to get a larger sidewall/aspect ratio.
Little more expensive but would probably give you what you want.