Will a smaller rolling diameter be a problem?

Discussion of Infiniti's amazing (and underrated) sport-luxury crossovers, the EX35 and EX37. For 2014, the EX series will be renamed QX50, in line with Ininfiit's new naming conventions.
me73
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Will a smaller rolling diameter be a problem?

Postby me73 » Sat Dec 05, 2020 11:45 am

Hi all. I have a 2017 QX50 AWD with the tech package which means I have the 19" wheels. I have a set of winter wheels from my previous G37 which are 17"s and are about 3.5% smaller in rolling diameter that I'd like to fit to the car this winter. I am wondering if anyone has experience with running a slightly smaller diameter tire. I just don't want any of the electronics to be confused by the diameter change.


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VStar650CL
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Car: 2013 Altima 2.5 SL, 2004 Altima 2.5 S

Re: Will a smaller rolling diameter be a problem?

Postby VStar650CL » Sat Dec 05, 2020 2:12 pm

Generally you'll be fine if you change all 4. The algorithms used by the ABS and AWD are all ratiometric, so altering size on one axle or one wheel will cause guaranteed issues. When changing all 4, the car simply won't know it's travelling slower than indicated. Of course your speedo will read 3.5% high and you'll have a bit more torque off the line, but other than that, you shouldn't have issues.

me73
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Joined: Fri May 19, 2006 4:17 pm

Re: Will a smaller rolling diameter be a problem?

Postby me73 » Sat Dec 05, 2020 2:49 pm

VStar650CL wrote:
Sat Dec 05, 2020 2:12 pm
Generally you'll be fine if you change all 4. The algorithms used by the ABS and AWD are all ratiometric, so altering size on one axle or one wheel will cause guaranteed issues. When changing all 4, the car simply won't know it's travelling slower than indicated. Of course your speedo will read 3.5% high and you'll have a bit more torque off the line, but other than that, you shouldn't have issues.
Thanks for the feedback. My main concern are the systems that rely on the camera like the pre-collision and smart cruise control.

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VStar650CL
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Re: Will a smaller rolling diameter be a problem?

Postby VStar650CL » Sat Dec 05, 2020 3:02 pm

They may be slightly affected, but the ADAS and Radar work with closing vectors and closing speeds that don't consider much data from the rest of the car unless it becomes an AEB situation. It might also affect VDC and 4WAS in an AEB, skid, or traction-loss situation, but 3.5% isn't a huge difference and my guess is all the systems would have plenty of built-in "slop" to handle it.

me73
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Joined: Fri May 19, 2006 4:17 pm

Re: Will a smaller rolling diameter be a problem?

Postby me73 » Sun Jan 03, 2021 10:53 pm

Just to close this out, I've been running on 225/55r17 winters that I originally had on my G37. They do seem to work just fine, not obvious issues with the optical control systems. No obvious handling repercussions (save for a bunch of understeer on the soft winter rubber) and the ride feels very similar to the 19" Goodyear Eagles.


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