secretariata
secretariata SuperDork
10/5/19 3:47 p.m.

So, I recently picked up a 2006 G35 sedan with a manual trans to become my DD once I sell off a few members of the fleet.  It will need tires soon.  Stock size is 245/45/18 on 8" wide wheels all around.  In window shopping tires I have found the Riken Raptor ZR A/S in 235/40/18 for $94 each on Tire Rack.  It has pretty good reviews and would keep my costs down.  Online tire dimension calculators indicate this is about a 4-5% difference in diameter and circumference.  I know this would cause my speedo to be off by about 3 mph.

I keep hearing the general rule is to stay within 3%, but it has always been in discussion of the relative difference between front and rear tire sizes.  In this case the tires would be the same size all around (same as stock setup) so no relative difference between front and rear, but the overall tire diameter and circumference would be 4-5% different from stock. Are the factory TC & VSS systems sophisticated enough to notice this and freak out?

ProDarwin
ProDarwin UltimaDork
10/5/19 4:59 p.m.

If its the same size all the way around, the factory system will have no way of knowing you changed the diameter.

nocones
nocones UltraDork
10/5/19 5:16 p.m.

Yep If it's expecting same speed (diameter) front and rear you can run anything as long as it's the same size.  Now the 350Z with staggered tires will freak our if you accidentally put the front tires on the back....  

secretariata
secretariata SuperDork
10/5/19 5:48 p.m.
nocones said:

Now the 350Z with staggered tires will freak our if you accidentally put the front tires on the back....  

It won't totally freak out. On the street it only interferes on some low speed sharp corners & won't give full throttle. It's not consistent about interfering either. No experience on track or autox to compare.

secretariata
secretariata SuperDork
10/5/19 5:49 p.m.

Yeah, I didn't think it was "smart" enough to tell anything beyond relative differences. Thanks!

G_Body_Man
G_Body_Man UltraDork
10/5/19 7:35 p.m.

As long as it's a square setup, a G35's stability control genuinely won't care about diameter. With a stagger it has to be within a 3% difference between the two sizes, and running a reverse stagger (as some 350Z owners may have done) can trigger VDC in tight corners simply because the rear contact patches are narrower than the fronts causing an imbalance in grip that can lead to oversteer.

secretariata
secretariata SuperDork
10/5/19 11:09 p.m.

Also, my TPMS sensors are dead.  This is pretty new tech for me, so questions...

RockAuto has AC Delco replacements for $32 each before the GRM discount.  Will these automatically be read by the system after a few miles or do they need to be programmed?  On my FRS the second OEM set just worked after a few miles, but I don't know if that is typical.

secretariata
secretariata SuperDork
10/5/19 11:13 p.m.
G_Body_Man said:

With a stagger it has to be within a 3% difference between the two sizes, and running a reverse stagger (as some 350Z owners may have done) can trigger VDC in tight corners simply because the rear contact patches are narrower than the fronts causing an imbalance in grip that can lead to oversteer.

I think the issue is related to rotational speeds due to differences in diameter/circumference not width.  My 350z (for sale in the classifieds) has a square setup and occasionally activates the VDC in tight corners.

Run_Away
Run_Away Dork
10/6/19 12:47 a.m.

As stated, low speed maneuvers may trigger traction control but higher speeds should be fine.

 

Had a customer with this issue on a juke, tires a couple sizes too small and being aggressive with steering inputs at parking lot speeds caused the traction control to freak out

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