Tire size difference/affect on speedometer?

irv

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2,137
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Oshawa, Ont. Canada
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I just purchased some snow tires for my son's GF. The girlfriends mother wanted snowy's on her daughters car asap with the 3-4 inches of snow we received last night/this morning so since I was the chosen one to do this, I purchased some I found online but chose a different size tire/wheel. The winter tires/wheels with TPM's, (hopefully?) I bought came off a 2005 Malibu just like her car (exact same) but are 205-65-R15's compared to her current tires/wheels which are 215-60-R16's. How much difference in speed will she notice being as the tire is slightly smaller in diameter than what is currently on her car? As an aside, I got Nexen tires (which I believe are Cooper tires?) on stock Malibu rims and only paid 200 dollars for them. The tread is still healthy/deep, imo, as well.

Key's tires.png


Keys tires1.png


Keys tires2.png
 

irv

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2,137
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Oshawa, Ont. Canada
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Originally Posted by 4WD
Thanks, 4wd. This is the info it gave me. 2.6% difference. Thoughts? You might have to punch the numbers/sizes in yourself? All the numbers have shifted over when I copied and pasted it. Tire Size Comparison Specification Sidewall Radius Diameter Circumference Revs/Mile Difference 205/65-15 5.2in 12.7in 25.5in 80.1in 791 0.0% 215/60-16 5.1in 13.1in 26.2in 82.2in 771 2.6%
 
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271
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Northeast Georgia
Download a GPS app to your smartphone. Most will have your landspeed. They are not "always" 100%...but should get you close enough to keep from getting a speeding ticket. Put the phone on the dash and compare while driving. Shorter diameter tire = speedometer will show faster than what the vehicle is actually traveling. Taller diameter tire = speedometer will show slower than what the vehicle is actually traveling...which COULD get you a speeding ticket if the traffic laws are strict.
 

irv

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2,137
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Oshawa, Ont. Canada
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Originally Posted by GoldDot40
Download a GPS app to your smartphone. Most will have your landspeed. They are not "always" 100%...but should get you close enough to keep from getting a speeding ticket. Put the phone on the dash and compare while driving. Shorter diameter tire = speedometer will show faster than what the vehicle is actually traveling. Taller diameter tire = speedometer will show slower than what the vehicle is actually traveling...which COULD get you a speeding ticket if the traffic laws are strict.
That's a good idea. I will tell her to do that. Thanks. cheers
 

irv

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2,137
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Oshawa, Ont. Canada
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Originally Posted by FordBroncoVWJeta
Perfect. Thank you! cheers Speedometer Difference Speedo Reading Actual Speed 20 mph (32.19 km/h) 19.49 mph (31.37 km/h) 25 mph (40.23 km/h) 24.36 mph (39.21 km/h) 30 mph (48.28 km/h) 29.24 mph (47.05 km/h) 35 mph (56.33 km/h) 34.11 mph (54.89 km/h) 40 mph (64.37 km/h) 38.98 mph (62.74 km/h) 45 mph (72.42 km/h) 43.86 mph (70.58 km/h) 50 mph (80.47 km/h) 48.73 mph (78.42 km/h) 55 mph (88.51 km/h) 53.6 mph (86.26 km/h) 60 mph (96.56 km/h) 58.47 mph (94.1 km/h) 65 mph (104.61 km/h) 63.35 mph (101.95 km/h)
 
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39,409
Location
Great Lakes
Originally Posted by irv
The tread is still healthy/deep, imo, as well.
Did you look at the date codes? FWIW, my winter tires have plenty of tread left, but don't grip/handle in show all that well because they're old.
 
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265
Location
Canada, Russia
I would start looking for a new set of tires if my tires were like this. The tread wear indicator shows that only about 1 mm left if I see it correctly.
 
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14,874
Location
NE,Ohio
Originally Posted by Ded Mazai
I would start looking for a new set of tires if my tires were like this. The tread wear indicator shows that only about 1 mm left if I see it correctly.
are we looking at the same picture? they seem to be at least 8/32 to 9/32 to me.
 
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1,077
Location
Wisconsin
Originally Posted by Quattro Pete
Originally Posted by irv
The tread is still healthy/deep, imo, as well.
Did you look at the date codes? FWIW, my winter tires have plenty of tread left, but don't grip/handle in show all that well because they're old.
They probably grip better than my new summer treads
 
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265
Location
Canada, Russia
I don't know if we are looking at the same picture. A new winter tire usually is about 9-10 mm deep. If a winter tire is at 4 mm (where the tread wear indicator is) it is 100% worn out. I would guess the current tire tread is 5 mm deep. It may last for 1 season depending on the driving style. Not worth the trouble to have them mounted on the wheels even if they were free.
 

irv

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Oshawa, Ont. Canada
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Originally Posted by Quattro Pete
Originally Posted by irv
The tread is still healthy/deep, imo, as well.
Did you look at the date codes? FWIW, my winter tires have plenty of tread left, but don't grip/handle in show all that well because they're old.
No, I did not but I am not worried about that in the least. Like, Rand, I am unsure what pics Ded Mazai is looking at? The tires are, obviously, not new but they are far from being worn out and for $200 dollars for everything, I am not complaining one bit considering the tread that is still on them, which, imo, is still fairly decent and very much worthy.
 
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Location
Prospect, KY
Snow tires do seem to lose their snow traction very quickly as treadwear increases more so than all weather tires. However even worn snow tires tend to be better in snow than non snow tires. They don't drive so great on dry pavement either but in snow you will be very happy.
 
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39,409
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Great Lakes
Originally Posted by irv
Q&A: Replacing tyres at 3mm tread "an absolute waste" says Michelin director https://www.honestjohn.co.uk/news/m...n-absolute-waste-says-michelin-director/
Was the above piece addressing winter tires or only summer/all-season ones? The issue of degrading wet/snow performance as treadwear is worn down has been tested and addressed by multiple sources in the past. There is definitely an impact there. https://www.consumerreports.org/tires/make-sure-your-tires-have-enough-tread-for-winter/ https://www.tirerack.com/tires/tiretech/techpage.jsp?techid=163 I don't mind buying many used items, but winter tires will never be one of them, unless they're in "like new" condition that someone bought by mistake and never driven them, and they're no more than 1 year old from the date of manufacturing.
 

irv

Messages
2,137
Location
Oshawa, Ont. Canada
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Originally Posted by Quattro Pete
Originally Posted by irv
Q&A: Replacing tyres at 3mm tread "an absolute waste" says Michelin director https://www.honestjohn.co.uk/news/m...n-absolute-waste-says-michelin-director/
Was the above piece addressing winter tires or only summer/all-season ones? The issue of degrading wet/snow performance as treadwear is worn down has been tested and addressed by multiple sources in the past. There is definitely an impact there. https://www.consumerreports.org/tires/make-sure-your-tires-have-enough-tread-for-winter/ https://www.tirerack.com/tires/tiretech/techpage.jsp?techid=163 I don't mind buying many used items, but winter tires will never be one of them, unless they're in "like new" condition that someone bought by mistake and never driven them, and they're no more than 1 year old from the date of manufacturing.
Well, I guess we are all different as I honestly have no issue purchasing used snow tires, especially when they are practically new. Mine are 5 yrs old now and if I was looking for a used set, I'd also have no issue purchasing mine if someone else owned them. It is real easy to look for defects/slices, cupped edges, etc. If none of that appears, and depending on price, I'l purchase them if I need them. I checked the tires in question with a tread depth gauge and 2 tires measure around 7.75 MM or 9/32 and the other 2 are right at 8 MM,s. The difference between all 4 is marginal. I asked my son, who has far better eyes than mine, even with my glasses on, and he confirmed my findings. I appreciate the info/concerns just the same. Thanks guys. cheers
 
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