changing tire profile size dangerous?

MD-370z · 09-06-2011, 07:07 PM

Hello wheel experts of the 370z forum.

I am thinking about buying track rims for my 370z that I would put on before track events and drive to the track with and back. I think I have settled on 18 inch rims with the offset of 18x10 +34. I want to run 285 ad08's on these rims but these tires only come in a profile of 30.

I used the tire calculator and it said it was too much of a difference and would be dangerous for braking. Thus in short I am asking if this is true if so, it would completly negate the reason for me getting track rims, to get faster on track and save a little cash in the long run, if my brakes dont work well then tracking just isnt that fun anymore...

So can anyone give me their opinion or experience with running lower profile tires than the sports package 19inch rays?

Thanks in advance!

vividracing · 09-06-2011, 07:27 PM

What calculator are you using? In theory, it's possible that the brakes will get hotter with the smaller wheel. But the calculator can't account for the design differences in wheels...

Tons of people run 18s on their 370Zs for the track, I wouldn't sweat it. What wheels and tires are you thinking about?

Red__Zed · 09-06-2011, 07:43 PM

your speedo will be slightly off, and effective gearing shorter. With a 285/30/18 it won't be that problematic though. My SSRs have a similar tire profile.

cossie1600 · 09-06-2011, 07:59 PM

I ran 285/30/18 (sold it to another forum member). Your speedo will be off by about 5mph. Car will feel like it gained an extra 50hp. In my case, more wheelspin and hop since it is so much less to spin. Other than that, nothing dramatic. You would probably need to disable the VDC.

MD-370z · 09-06-2011, 08:01 PM

im strongly considering the forgestar f14 in orange ( Im dutch so I have to represent my country!). The vdc is always off cossie it bites far too early than I want so that will never be an issue.

the tire size calculator i am using is the one from 1010 tires.

Nikon FM · 09-06-2011, 08:05 PM

Quote:

Originally Posted by MD-370z

Hello wheel experts of the 370z forum.

I am thinking about buying track rims for my 370z that I would put on before track events and drive to the track with and back. I think I have settled on 18 inch rims with the offset of 18x10 +34. I want to run 285 ad08's on these rims but these tires only come in a profile of 30.

I used the tire calculator and it said it was too much of a difference and would be dangerous for braking. Thus in short I am asking if this is true if so, it would completly negate the reason for me getting track rims, to get faster on track and save a little cash in the long run, if my brakes dont work well then tracking just isnt that fun anymore...

So can anyone give me their opinion or experience with running lower profile tires than the sports package 19inch rays?

Thanks in advance!

I run
265x30x19 front
295x30x19 rear

car feels great on the track. A little higher RPMs of course but braking is fine now that I found a good setup (pads, fluid, rotors).

ChrisSlicks · 09-06-2011, 08:18 PM

I have short and tall tires on 2 different sets of wheels. The "short" tires have great acceleration due to the shortened gearing. I haven't noticed any braking issues as long as front and back are kept a similar diameter.

MD-370z · 09-06-2011, 08:51 PM

well id be purchasing square rims so i can rotate the rims w/ tires to get the most use out of them. so all four corners would be running 18x10 + 34 with 285/30/18 inch rims. SO the opinion is that it should work?

ChrisSlicks · 09-06-2011, 08:53 PM

Quote:

Originally Posted by MD-370z

well id be purchasing square rims so i can rotate the rims w/ tires to get the most use out of them. so all four corners would be running 18x10 + 34 with 285/30/18 inch rims. SO the opinion is that it should work?

Yes.

cossie1600 · 09-06-2011, 11:26 PM

I forgot to mention that the only thing I hate about the 285/30/18 (might have been 295/30 F&R, honestly dont remember). The car sits way too low for my liking. It would rub at every little incline

MD-370z · 09-07-2011, 07:00 AM

Are you lowered cossie?

kenchan · 09-07-2011, 10:41 AM

check load ratings and if they are similar to the RE050A's or the Yok's you get on the 18's you're fine.

cossie1600 · 09-07-2011, 10:44 AM

Quote:

Originally Posted by MD-370z

Are you lowered cossie?

No, but the car rode more than an inch lower with the smaller tire.

Mike · 09-07-2011, 10:52 AM

One of my sets of wheels is exactly what you are looking at. 18x10+34 F14s with 285/30-18 AD08s all around. The other is even smaller with 275/35s. The speedo is off by about 10% and you will need a 15-25mm spacer in the rear, but other than that, no issues.

b1adesofcha0s · 09-07-2011, 11:35 AM

So is the speedo going to read higher or lower than the actual speed? Getting lower profile tires myself, but not as dramatic of a drop. 50 -> 40 for the front and 45 -> 35 for rear.

09-06-2011, 07:07 PM	#1 (permalink)
MD-370z Base Member Join Date: Apr 2009 Location: canada Posts: 137 Drives: 370z,MB, sport, m6, Rep Power: 16	changing tire profile size dangerous? Hello wheel experts of the 370z forum. I am thinking about buying track rims for my 370z that I would put on before track events and drive to the track with and back. I think I have settled on 18 inch rims with the offset of 18x10 +34. I want to run 285 ad08's on these rims but these tires only come in a profile of 30. I used the tire calculator and it said it was too much of a difference and would be dangerous for braking. Thus in short I am asking if this is true if so, it would completly negate the reason for me getting track rims, to get faster on track and save a little cash in the long run, if my brakes dont work well then tracking just isnt that fun anymore... So can anyone give me their opinion or experience with running lower profile tires than the sports package 19inch rays? Thanks in advance!

09-06-2011, 07:27 PM	#2 (permalink)
vividracing The370Z.com Sponsor Join Date: Jun 2009 Location: Gilbert, AZ Age: 38 Posts: 7,306 Drives: 350Z,370Z,GTR Rep Power: 39	What calculator are you using? In theory, it's possible that the brakes will get hotter with the smaller wheel. But the calculator can't account for the design differences in wheels... Tons of people run 18s on their 370Zs for the track, I wouldn't sweat it. What wheels and tires are you thinking about? __________________ Rocky @ Vivid ♦ 480.966.3040 x236 ♦ Rocky@vividracing.com Email, PM, or call me directly for aggressive The370Z.com member pricing!!!

09-06-2011, 08:01 PM	#5 (permalink)
MD-370z Base Member Join Date: Apr 2009 Location: canada Posts: 137 Drives: 370z,MB, sport, m6, Rep Power: 16	im strongly considering the forgestar f14 in orange ( Im dutch so I have to represent my country!). The vdc is always off cossie it bites far too early than I want so that will never be an issue. the tire size calculator i am using is the one from 1010 tires. Last edited by MD-370z; 09-06-2011 at 08:04 PM.

09-06-2011, 08:18 PM	#7 (permalink)
ChrisSlicks A True Z Fanatic Join Date: Mar 2009 Location: North East Posts: 6,203 Drives: 09 370Z Sport M6 Rep Power: 653	I have short and tall tires on 2 different sets of wheels. The "short" tires have great acceleration due to the shortened gearing. I haven't noticed any braking issues as long as front and back are kept a similar diameter. __________________ Hotchkis ARB \| Stillen CAI \| Art Pipes \| Berk CBE \| Stillen AP Racing Brakes \| AE Performance Oil Cooler \| BC Racing ER Coilovers \| Doran Control Arms

09-07-2011, 10:52 AM	#14 (permalink)
Mike The370Z.com Sponsor Join Date: Jun 2009 Location: Loganville, GA Posts: 5,944 Drives: 370z Rep Power: 2186	One of my sets of wheels is exactly what you are looking at. 18x10+34 F14s with 285/30-18 AD08s all around. The other is even smaller with 275/35s. The speedo is off by about 10% and you will need a 15-25mm spacer in the rear, but other than that, no issues. __________________ NISSAN: 75 280Z / 86 300ZX GLL /87 Sentra SE / 03 350Z / 23 Z Porsche: 93 968 / 23 Macan GTS / 93 968

09-06-2011, 07:43 PM	#3 (permalink)
Red__Zed A True Z Fanatic Join Date: Jul 2010 Location: window seat Posts: 28,940 Drives: Mostly on two wheels Rep Power: 120	your speedo will be slightly off, and effective gearing shorter. With a 285/30/18 it won't be that problematic though. My SSRs have a similar tire profile.

09-06-2011, 07:59 PM	#4 (permalink)
cossie1600 A True Z Fanatic Join Date: Jun 2009 Location: californee way Posts: 5,380 Drives: 370, Leaf Rep Power: 30	I ran 285/30/18 (sold it to another forum member). Your speedo will be off by about 5mph. Car will feel like it gained an extra 50hp. In my case, more wheelspin and hop since it is so much less to spin. Other than that, nothing dramatic. You would probably need to disable the VDC.

09-06-2011, 08:51 PM	#8 (permalink)
MD-370z Base Member Join Date: Apr 2009 Location: canada Posts: 137 Drives: 370z,MB, sport, m6, Rep Power: 16	well id be purchasing square rims so i can rotate the rims w/ tires to get the most use out of them. so all four corners would be running 18x10 + 34 with 285/30/18 inch rims. SO the opinion is that it should work?

09-06-2011, 11:26 PM	#10 (permalink)
cossie1600 A True Z Fanatic Join Date: Jun 2009 Location: californee way Posts: 5,380 Drives: 370, Leaf Rep Power: 30	I forgot to mention that the only thing I hate about the 285/30/18 (might have been 295/30 F&R, honestly dont remember). The car sits way too low for my liking. It would rub at every little incline

09-07-2011, 07:00 AM	#11 (permalink)
MD-370z Base Member Join Date: Apr 2009 Location: canada Posts: 137 Drives: 370z,MB, sport, m6, Rep Power: 16	Are you lowered cossie?

09-07-2011, 10:41 AM	#12 (permalink)
kenchan A True Z Fanatic Join Date: Aug 2009 Location: N/A Posts: 76,801 Drives: N/A Rep Power: 141521	check load ratings and if they are similar to the RE050A's or the Yok's you get on the 18's you're fine.

09-07-2011, 11:35 AM	#15 (permalink)
b1adesofcha0s A True Z Fanatic Join Date: Jan 2011 Location: MD Posts: 40,963 Drives: HypeTrain Choo Choo! Rep Power: 142	So is the speedo going to read higher or lower than the actual speed? Getting lower profile tires myself, but not as dramatic of a drop. 50 -> 40 for the front and 45 -> 35 for rear. __________________ Project: b1adeZmobile (2009 370Z) \| Uprev Tune by AAM Competition \| Berk Exhaust Project: b1adeZmobile 2.0 (2014 C7 Z51) \| Corsa Xtreme Exhaust

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