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Running different size on front and rear question. #4689796
03/09/18 05:53 PM
03/09/18 05:53 PM
Joined: Apr 2004
Posts: 7,743
New York
pbm Offline OP
pbm  Offline OP
Joined: Apr 2004
Posts: 7,743
New York
I recently picked up a 2006 Focus wagon and I'm replacing 2 tires (2 are like new). The OE size is 195/60/15. I have 2 brand new 195/65/15's (Cooper CS-5) that I bought for a different car. Would you run the slightly bigger (195/65/15) on the rear or front? (I'm thinking rear is better but I'm open to be educated differently). Anybody see a problem doing this? Thanks.


'Journalism is Dead'
Re: Running different size on front and rear question. [Re: pbm] #4689803
03/09/18 05:56 PM
03/09/18 05:56 PM
Joined: Feb 2014
Posts: 2,491
Canada
Lolvoguy Offline
Lolvoguy  Offline
Joined: Feb 2014
Posts: 2,491
Canada
Most tire and service shops will not mount/balance your new tires if they know the other set are a different size.
Personally I'd hold out for all 4 the same size to avoid any safety issues.


06 Lexus IS350- Wife
88 BMW 325is- Mistress
Re: Running different size on front and rear question. [Re: pbm] #4689823
03/09/18 06:24 PM
03/09/18 06:24 PM
Joined: Oct 2005
Posts: 11,365
PA
d00df00d Offline
d00df00d  Offline
Joined: Oct 2005
Posts: 11,365
PA
Don't do it. Different front and rear diameters will screw with your ABS. Stability control too, if you have it.

At a minimum, those systems won't work right. Your car might even disable them outright if it detects a chronic difference in wheel speeds between front and rear.


2011 Mazda RX-8 R3
Mobil Super 5w-20
Re: Running different size on front and rear question. [Re: Lolvoguy] #4689824
03/09/18 06:25 PM
03/09/18 06:25 PM
Joined: Apr 2004
Posts: 7,743
New York
pbm Offline OP
pbm  Offline OP
Joined: Apr 2004
Posts: 7,743
New York
Originally Posted By: Lolvoguy
Most tire and service shops will not mount/balance your new tires if they know the other set are a different size.
Personally I'd hold out for all 4 the same size to avoid any safety issues.


Where I get them mounted and balanced that won't be a problem.


'Journalism is Dead'
Re: Running different size on front and rear question. [Re: pbm] #4689828
03/09/18 06:28 PM
03/09/18 06:28 PM
Joined: Jun 2012
Posts: 1,704
USA
oldhp Offline
oldhp  Offline
Joined: Jun 2012
Posts: 1,704
USA
3/4" taller with the 195/65R15 which would be 3/8ths" taller on the car. Wouldn't hurt a thing to me. I would put these on the rear. Go to https://tiresize.com/comparison/ to see for yourself.



Re: Running different size on front and rear question. [Re: pbm] #4689829
03/09/18 06:30 PM
03/09/18 06:30 PM
Joined: Sep 2014
Posts: 2,099
US-WA
Dyusik Offline
Dyusik  Offline
Joined: Sep 2014
Posts: 2,099
US-WA
Rear to not mess with the speedo. Did that on my old Cavalier, they were MUCH bigger. Improved my handling drastically, much needed as my front shocks were fubar.


95 Cherokee 190K DELO 10W30, XG8
07 IS250 100K Napa 10w30, FULL
04 YZF-R1 19K DELO 15w40, XG7317
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Re: Running different size on front and rear question. [Re: pbm] #4689831
03/09/18 06:30 PM
03/09/18 06:30 PM
Joined: Jun 2013
Posts: 1,039
iowa
Traction Offline
Traction  Offline
Joined: Jun 2013
Posts: 1,039
iowa
It's a pretty simple answer. Sell them, and run what's supposed to be on your car.


Certified Tire Service Instructor since 2009
50 Chevy Fire Truck
13 Tahoe Pursuit
97 C5 Corvette
00 BMW M Roadster
02 Camry
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Re: Running different size on front and rear question. [Re: pbm] #4689844
03/09/18 06:44 PM
03/09/18 06:44 PM
Joined: Oct 2012
Posts: 4,631
Taiwan
Ducked Offline
Ducked  Offline
Joined: Oct 2012
Posts: 4,631
Taiwan
If you follow the "best tyres on the back" mantra, and you think lower profile tyres are better, then the OEM tyres should go on the back, assuming there are no clearance issues at the front, and that you're not bothered about a slight change in gearing and speedo reading.

I wouldn't have thought a 5 point change in aspect ratio would make that much difference to handling or modern gizmology like ABS, but I'm open to being educated differently too.

Theres allegedly a rule-of-thumb limit of 2% change in rolling radius. According to this online calculator, you'd be over that at 3.17% and shouldn't do it.

http://tyrestore.in/upsizing.htm

Re: Running different size on front and rear question. [Re: pbm] #4689868
03/09/18 07:08 PM
03/09/18 07:08 PM
Joined: Mar 2008
Posts: 6,837
USA
slacktide_bitog Offline
slacktide_bitog  Offline
Joined: Mar 2008
Posts: 6,837
USA
Tires in those 15-inch sizes are not expensive. Get a set of 4 of the correct size 195/60-15 smile

DT/DTD often has a good sale on the CS5 Ultra, so you can always get a set when they go on sale again. It ends up being a set of 4 tires for the price of 2 anyway.

Re: Running different size on front and rear question. [Re: Ducked] #4689873
03/09/18 07:12 PM
03/09/18 07:12 PM
Joined: Oct 2002
Posts: 36,312
Great Lakes
Quattro Pete Offline
Quattro Pete  Offline
Joined: Oct 2002
Posts: 36,312
Great Lakes
Originally Posted By: Ducked
I wouldn't have thought a 5 point change in aspect ratio would make that much difference to handling or modern gizmology like ABS, but I'm open to being educated differently too.

The ABS sensors in my car will trigger the traction control light when my tires are only slightly under-inflated (cheap man's TPMS), so I can see how using an even slightly different tire size could do the same.



'02 530i (Edge 0W-40)
'15 Q5 3.0T (Edge 5W-40)
'18 Charger SRT (FF)
Re: Running different size on front and rear question. [Re: pbm] #4689904
03/09/18 07:44 PM
03/09/18 07:44 PM
Joined: Nov 2008
Posts: 12,558
NH
supton Offline
supton  Offline
Joined: Nov 2008
Posts: 12,558
NH
If it has ABS I probably wouldn't--although if they are on rims and you can swap on and off with ease... then why not? Could always disable ABS if you're trying to save a buck. If it didn't have ABS I wouldn't think much about it. Same width, only slightly different aspect ratio.

Not that uncommon to drop a size in width (and gain in aspect) when running snow tires, under the mantra of more narrow is better for traction. This case, it's not even that.

I'd be more concerned with running wildly different tread patterns, and upsetting the cars natural handling--but I'm guessing that, as long as the tires have tread, it's just a matter of how much it wants to understeer, not that it suddenly oversteers.


2011 Toyota Camry, base, 2.5L/6MT, 163k, hers
2010 Toyota Tundra DC, 4.6L/6AT, 144k, ours
1999 Toyota Camry LE, 2.2L/4AT, 190k, his
Re: Running different size on front and rear question. [Re: pbm] #4689909
03/09/18 07:46 PM
03/09/18 07:46 PM
Joined: Mar 2005
Posts: 29
KY
pburchett Offline
pburchett  Offline
Joined: Mar 2005
Posts: 29
KY
It will work just fine. Did this on a 2009 Focus. Wore the tires out and never had a problem.

Re: Running different size on front and rear question. [Re: pbm] #4689985
03/09/18 09:18 PM
03/09/18 09:18 PM
Joined: Aug 2017
Posts: 560
MN
14Accent Offline
14Accent  Offline
Joined: Aug 2017
Posts: 560
MN
It'll be fine.

I'm running completely different size than stock on my Marauder due to the factory size rear being very odd (and expensive). Stock is 235/50R18 front 245/55R18 rear. I'm running 245/40's up front and 255/34's out back. The ABS works just fine, it doesn't know the difference.

The 2004 Marauders are more picky, but there's still a wide range of sizes that work fine.


2013 Chevrolet Volt - Saves enough in fuel to pay for itself!

2003 Cadillac Seville STS - The winter "beater", it uses the Volt's fuel
Re: Running different size on front and rear question. [Re: 14Accent] #4690184
03/10/18 06:08 AM
03/10/18 06:08 AM
Joined: Oct 2005
Posts: 11,365
PA
d00df00d Offline
d00df00d  Offline
Joined: Oct 2005
Posts: 11,365
PA
It's one thing if the ABS works -- as in, it engages and does something.

It's another thing if the ABS works "just fine" -- as in, the way it should. How have you determined that part?


2011 Mazda RX-8 R3
Mobil Super 5w-20
Re: Running different size on front and rear question. [Re: d00df00d] #4690270
03/10/18 08:43 AM
03/10/18 08:43 AM
Joined: Aug 2010
Posts: 5,685
Champlain/Hudson Valley
Kira Offline
Kira  Offline
Joined: Aug 2010
Posts: 5,685
Champlain/Hudson Valley
To pbm: Simply explain the situation to the manager and swap 'em. Lots of cars use the 196-65-15 size so they'd move.
Keep it simple and easy. Do your new "65's" still have their stickers?

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