Question about tires

Jhon Snow · 07-02-2014, 03:20 PM

as you guys know the car comes with these tires (with sports package):
245/40WR19 (front) and 275/35WR19 (rear)

I would like to cheaply increase the minimum ground clearance just a little bit (by about 1.1" if my math is correct), and i was planning on doing this by changing the tire size from the standard ones it comes with to something along the lines of:

245/45WR19 (front) and 275/40WR19 (rear)

From what I have found on Google searches, this would be a bad idea, because it would:
-throw the mileage off (but by much?)
-mess up the breaking system (don't know how, but many people claim this)
-make turning harder (not really sure how for this one either)

So what I wanted to ask you guys was, is this true?
Should I do this once I get the car? Or am I asking for trouble?
(probably have the car in 2 weeks to a month, but want to change tires and add an oil cooler as soon as I get it)

Any help would appreciated,
Thanks

JARblue · 07-02-2014, 03:36 PM

That's a pretty minimal change. I'm not sure it would affect any of the things you mention.

It will throw your speedometer off by a very small percentage. Here is a good website where you can compare the differences: Custom rims, wheel tire packages for your ride - RIMSnTIRES.com

quickboat · 07-02-2014, 04:11 PM

It would smooth out the bumps some while lowering steering response. But for someone who is contemplating this mod, steering response is likely not too critical.

kenchan · 07-02-2014, 04:14 PM

if you want slightly taller sidewall, go 10mm wider and same profile.

Davey · 07-02-2014, 05:36 PM

Your math is not exactly correct. That's not getting you 1.1" of ground clearance.

You are right, it's about 1" taller overall. Think about it; if you add 1" to the diameter you are only adding 1/2" to the radius. About 3.5% increase, it's not too far out of spec but it's only getting you 1/2" in actual clearance.

So your speedo will read a little low (off by less than 3 mph at legal speeds) and your gearing will be a little higher and your car will be 1/2" higher off the pavement.

Jhon Snow · 07-08-2014, 05:59 AM

Sorry was very busy this week, just got around to this post. Thanks a lot for all the input, really appreciate it.

Jhon Snow · 07-08-2014, 06:02 AM

Quote:

Originally Posted by Davey

Your math is not exactly correct. That's not getting you 1.1" of ground clearance.

You are right, it's about 1" taller overall. Think about it; if you add 1" to the diameter you are only adding 1/2" to the radius. About 3.5% increase, it's not too far out of spec but it's only getting you 1/2" in actual clearance.

So your speedo will read a little low (off by less than 3 mph at legal speeds) and your gearing will be a little higher and your car will be 1/2" higher off the pavement.

Just looked it up, you are right, my mistake

07-02-2014, 03:20 PM	#1 (permalink)
Jhon Snow Base Member Join Date: Jun 2014 Location: ny state Posts: 3 Drives: 370z soon... Rep Power: 11	Question about tires as you guys know the car comes with these tires (with sports package): 245/40WR19 (front) and 275/35WR19 (rear) I would like to cheaply increase the minimum ground clearance just a little bit (by about 1.1" if my math is correct), and i was planning on doing this by changing the tire size from the standard ones it comes with to something along the lines of: 245/45WR19 (front) and 275/40WR19 (rear) From what I have found on Google searches, this would be a bad idea, because it would: -throw the mileage off (but by much?) -mess up the breaking system (don't know how, but many people claim this) -make turning harder (not really sure how for this one either) So what I wanted to ask you guys was, is this true? Should I do this once I get the car? Or am I asking for trouble? (probably have the car in 2 weeks to a month, but want to change tires and add an oil cooler as soon as I get it) Any help would appreciated, Thanks

07-02-2014, 03:36 PM	#2 (permalink)
JARblue A True Z Fanatic Join Date: Mar 2011 Location: Austin, TX Age: 43 Posts: 36,450 Drives: 11 Z34, 98 E36 M3 Rep Power: 2684440	That's a pretty minimal change. I'm not sure it would affect any of the things you mention. It will throw your speedometer off by a very small percentage. Here is a good website where you can compare the differences: Custom rims, wheel tire packages for your ride - RIMSnTIRES.com __________________ 2011 370Z 6MT Sport Gun Metallic \| ARC \| CJM \| Ecutek \| FI \| Fujimura \| R2C \| SPL \| Stillen \| TWM \| Z1 \| ZSpeed \|

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07-02-2014, 04:11 PM	#3 (permalink)
quickboat Base Member Join Date: May 2014 Location: ohio Posts: 65 Drives: '14 370Z TSN M6 Rep Power: 11	It would smooth out the bumps some while lowering steering response. But for someone who is contemplating this mod, steering response is likely not too critical.

07-02-2014, 04:14 PM	#4 (permalink)
kenchan A True Z Fanatic Join Date: Aug 2009 Location: N/A Posts: 76,801 Drives: N/A Rep Power: 141521	if you want slightly taller sidewall, go 10mm wider and same profile.

07-02-2014, 05:36 PM	#5 (permalink)
Davey A True Z Fanatic Join Date: Apr 2011 Location: Indiana Posts: 3,766 Drives: '15 NISMO 6MT Rep Power: 117171	Your math is not exactly correct. That's not getting you 1.1" of ground clearance. You are right, it's about 1" taller overall. Think about it; if you add 1" to the diameter you are only adding 1/2" to the radius. About 3.5% increase, it's not too far out of spec but it's only getting you 1/2" in actual clearance. So your speedo will read a little low (off by less than 3 mph at legal speeds) and your gearing will be a little higher and your car will be 1/2" higher off the pavement.

07-08-2014, 05:59 AM	#6 (permalink)
Jhon Snow Base Member Join Date: Jun 2014 Location: ny state Posts: 3 Drives: 370z soon... Rep Power: 11	Sorry was very busy this week, just got around to this post. Thanks a lot for all the input, really appreciate it.