New Rear Tires causing no speedometer and all dash lights on

reckedz · 03-12-2020, 12:47 PM

Hey guys! I have a 7AT 370z. I just got new rear tires on and the car now has all dash lights on (Christmas tree), rev match not working, and speedometer not working at all. I’ve read that if the diameter is too different from the front to rear it will throw it off like this. Have already driven 200+ miles and codes cleared but no help. My wheels specs are: FRONT- 20x10 +28 REAR- 20x11 +12 the new rear tires are 305/30/20 and the front is still 255/30/20 (Used to have 285/30/20 in rear) I assume if I replace the front tires to a different size it will fix it but I need help figuring out what size will work and fix my problem. Thanks for the help!

JARblue · 03-12-2020, 02:20 PM

that tire stretch

You need to be within 3% tire diameter between front and rear.

FPenvy · 03-12-2020, 02:37 PM

Quote:

Originally Posted by JARblue

that tire stretch

You need to be within 3% tire diameter between front and rear.

305 on 11" isnt terrible but c'mon lol

i run 325 on 10.5"

BGTV8 · 03-12-2020, 03:16 PM

Your fronts are ~661mm in diameter and new rears are 691mm in dia. This is the root cause of your problem

A 285/30R20 front will be under 3% variance with 305 rear

FPenvy · 03-12-2020, 03:17 PM

Quote:

Originally Posted by BGTV8

Your fronts are ~661mm in diameter and new rears are 691mm in dia. This is the root cause of your problem

A 285/30R20 front will be under 3% variance with 305 rear

holy hell i just realized he's running a 255 on a 10" wheel

i retract previous statement. this man does not require help

reckedz · 03-12-2020, 03:26 PM

Alright so 285/30 is the best bet in front? I just worry about clearing it on my setup. I used to have 285 on the rear 11 wide and 255 in the front on 10 but wanting a meatier setup. I am on Swift spec r lowering springs and have fly1 carbon fiber vented fenders in the front.

FPenvy · 03-12-2020, 03:30 PM

Quote:

Originally Posted by reckedz

Alright so 285/30 is the best bet in front? I just worry about clearing it on my setup. I used to have 285 on the rear 11 wide and 255 in the front on 10 but wanting a meatier setup. I am on Swift spec r lowering springs and have fly1 carbon fiber vented fenders in the front.

the real question about your set up is..........are you running a ton of unnecessary negative camber?

with those widths of wheels you can run 285/325 without issue. i believe someone has even ran a 305 up front but thats like mm from rubbing everything.

on stock sport wheels (9"/10" i believe...it's been awhie) you can max out at 265/305 (what i run)

nismo wheels can go even more meat with the wheels being wider.

reckedz · 03-12-2020, 03:37 PM

https://images.fitmentindustries.com...gs2-bronze.jpg

https://images.fitmentindustries.com...gs2-bronze.jpg

Here are pictures from before i replaced the rear tires, but everything else is the same. Just want to make sure i wont be rubbing in the front since they are carbon and cant really do much of they do

FPenvy · 03-12-2020, 03:42 PM

Quote:

Originally Posted by reckedz

https://images.fitmentindustries.com...gs2-bronze.jpg

https://images.fitmentindustries.com...gs2-bronze.jpg

Here are pictures from before i replaced the rear tires, but everything else is the same. Just want to make sure i wont be rubbing in the front since they are carbon and cant really do much of they do

are you going widebody?

if not, you picked the wrong offset

reckedz · 03-12-2020, 03:46 PM

I am not. Bought these wheels from a guy who also wasn’t widebody. I don’t mind the poke. I have thought of doing a little camber for a cleaner look. I’m just trying to figure out how to get my speedometer working and dash lights off. Lmao

Eagle · 03-17-2020, 05:02 PM

Quote:

Originally Posted by reckedz

I am not. Bought these wheels from a guy who also wasn’t widebody. I don’t mind the poke. I have thought of doing a little camber for a cleaner look. I’m just trying to figure out how to get my speedometer working and dash lights off. Lmao

Increase front tire width or decrease the rear. Take your pick.

I've run 265 - 285 on an 18 x 10 +22 offset in the front. Currently running 295's square on an 18 x 10.5 +25 offset with -3.6 camber up front.

Rusty · 03-17-2020, 05:16 PM

OP your front tires are 26.1" Rear tires are 27.2". That's a 4.5% difference. No wonder your dash is lighted up as a Christmas.

A 285/30-20 is 26.8". With that, you would be 1.8% difference. You would be within the 3% range.

Smashley · 05-21-2020, 07:05 PM

Is 255/35/19 305/30/19 within 3% spec?
front wheels are 9.5 rears are 11

Rusty · 05-21-2020, 07:46 PM

Quote:

Originally Posted by Smashley

Is 255/35/19 305/30/19 within 3% spec?
front wheels are 9.5 rears are 11

Your fronts are 26" tall, and your rear is 26.3" tall. That puts you at 0.9%. You're good.

03-12-2020, 12:47 PM	#1 (permalink)
reckedz Base Member Join Date: Aug 2018 Location: Wisconsin Posts: 4 Drives: 13 370z Rep Power: 6	New Rear Tires causing no speedometer and all dash lights on Hey guys! I have a 7AT 370z. I just got new rear tires on and the car now has all dash lights on (Christmas tree), rev match not working, and speedometer not working at all. I’ve read that if the diameter is too different from the front to rear it will throw it off like this. Have already driven 200+ miles and codes cleared but no help. My wheels specs are: FRONT- 20x10 +28 REAR- 20x11 +12 the new rear tires are 305/30/20 and the front is still 255/30/20 (Used to have 285/30/20 in rear) I assume if I replace the front tires to a different size it will fix it but I need help figuring out what size will work and fix my problem. Thanks for the help!

03-12-2020, 02:20 PM	#2 (permalink)
JARblue A True Z Fanatic Join Date: Mar 2011 Location: Austin, TX Age: 43 Posts: 36,449 Drives: 11 Z34, 98 E36 M3 Rep Power: 2684440	that tire stretch You need to be within 3% tire diameter between front and rear. Chuck33079, Rusty, Ghostvette and 2 others like this. __________________ 2011 370Z 6MT Sport Gun Metallic \| ARC \| CJM \| Ecutek \| FI \| Fujimura \| R2C \| SPL \| Stillen \| TWM \| Z1 \| ZSpeed \|

03-12-2020, 03:16 PM	#4 (permalink)
BGTV8 A True Z Fanatic Join Date: Dec 2009 Location: 03350 Australia Posts: 1,503 Drives: 09 Nissan 370Z M6 Rep Power: 29907	Your fronts are ~661mm in diameter and new rears are 691mm in dia. This is the root cause of your problem A 285/30R20 front will be under 3% variance with 305 rear JARblue and reckedz like this.

03-12-2020, 03:37 PM	#8 (permalink)
reckedz Base Member Join Date: Aug 2018 Location: Wisconsin Posts: 4 Drives: 13 370z Rep Power: 6	https://images.fitmentindustries.com...gs2-bronze.jpg https://images.fitmentindustries.com...gs2-bronze.jpg Here are pictures from before i replaced the rear tires, but everything else is the same. Just want to make sure i wont be rubbing in the front since they are carbon and cant really do much of they do Last edited by reckedz; 03-12-2020 at 03:41 PM.

03-17-2020, 05:16 PM	#12 (permalink)
Rusty Ronin Samurai - Assassin Join Date: Dec 2011 Location: Fayettenam,Pennsyltucky Age: 68 Posts: 34,851 Drives: 2011 Nismo GM 6M Rep Power: 2684436	OP your front tires are 26.1" Rear tires are 27.2". That's a 4.5% difference. No wonder your dash is lighted up as a Christmas. A 285/30-20 is 26.8". With that, you would be 1.8% difference. You would be within the 3% range. Eagle and elhombre like this. __________________ 浪人 - 殺し屋 "The Difficult Anytime, The Impossible By Appointment Only" http://www.the370z.com/members-370z-...o-journal.html

03-12-2020, 03:26 PM	#6 (permalink)
reckedz Base Member Join Date: Aug 2018 Location: Wisconsin Posts: 4 Drives: 13 370z Rep Power: 6	Alright so 285/30 is the best bet in front? I just worry about clearing it on my setup. I used to have 285 on the rear 11 wide and 255 in the front on 10 but wanting a meatier setup. I am on Swift spec r lowering springs and have fly1 carbon fiber vented fenders in the front.

03-12-2020, 03:46 PM	#10 (permalink)
reckedz Base Member Join Date: Aug 2018 Location: Wisconsin Posts: 4 Drives: 13 370z Rep Power: 6	I am not. Bought these wheels from a guy who also wasn’t widebody. I don’t mind the poke. I have thought of doing a little camber for a cleaner look. I’m just trying to figure out how to get my speedometer working and dash lights off. Lmao

05-21-2020, 07:05 PM	#13 (permalink)
Smashley Enthusiast Member Join Date: Aug 2013 Location: Maryland Posts: 347 Drives: mt/sport/tour MB Rep Power: 11	Is 255/35/19 305/30/19 within 3% spec? front wheels are 9.5 rears are 11 Last edited by Smashley; 05-21-2020 at 07:07 PM.

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