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!

that tire stretch :eekdance:

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

:shakes head:

305 on 11" isnt terrible but c'mon lol

i run 325 on 10.5" :stirthepot:

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 :facepalm:

i retract previous statement. this man does not require help :wtf2:

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.

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 :rofl2:

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.

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. :rofl2:

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

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.