Different front/rear tires causing ABS/VSA issue

[ClearEyes]

Anyone running different size front/rear tires without issues? I have a civic 2017 EXT and I had 215 45R18 Michelin PS4s all around. A few weeks ago, a large screw got lodged into my side wall on 1 rear tire and Americas Tires said it was not repairable and had to be replaced. The tech said 215 is a weird size and that I should get 225 45R18s instead so theyre easier to replace. They offered YK GTX 225 45R18s. I decided to go ahead and replace both back tires (one was unrepairable) and leave my front tires for now, as the tread is fairly worn but not the point that it needs replacing. I also got their hazard tire plan for like $20/tire where theyll replace it for free if it happens again.

I drove around for a few weeks without issues. It seems they didnt even recalibrate the TPMS or anything and the car didnt complain. Yesterday, as I was merging from a freeway to another perpendicular freeway on a semi-circular road, I noticed my car slow down slightly and when i looked at the dash the VSA was flashing. I thought it was likely due to the tires and since it went away i left it alone. Then today, I went on a fairly long drive ~ 2 hours. I switched freeways on another semi-circular road and the VSA flashed again but this time the car gave warnings for VSA system, power steering and braking system that didnt go away immediately. The car drove fine and didnt seem to have any issues, so I kept driving to my next stop. I stopped for food and started the car again - all the warning lights were still on but car, again, drove fine. About 10 mins into the drive home, the warning lights went away but on another freeway merge, I got the VSA flashing light that went away shortly. I decided to go ahead and take it into the dealership for diagnostics. 1.5 hours later, the tech tells me they got a code theyve never seen before - C10094-94 for ABS/VSA activation taking too long. He said it was either the ABS failing (unlikely) or caused by the different tires. Since the VSA always came on first and this only occurred on curved roads where VSA would be engaged, it seemed fairly obvious it was the tires. Im thinking the ABS failing would also throw other codes. Luckily, they didnt charge me anything for the diagnostics.

Now im trying to decide if I should go ahead and just replace the front tires - they probably have like 2-5k tread left. Or if I should hold off. Im wondering if recalibrating the TPMS might fix it, as the TPMS may detect the tire differential and adjust.

I know having different tires is very uncommon on FWD cars, but has anyone had different tire sizes without issue? My civic is tuned on phearable 1.5. Ive had this tune for almost 3 years so I dont think the problem is related. Im thinking I may just go down to Americas tire and bite the bullet on the $500 to replace the front two tires.

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[bbeem]

The factory wheel and tire is an 18x8 with 235/40. I read you're running an 18x8.5 which I would also run the 235/40. 215/50 is strange for your 18x8.5-35 and the tech was a scrub for not looking at the factory spec and recommending 225/45 instead of 235/40 for a 8.5 wide wheel.

 

[ClearEyes]

The factory wheel and tire is an 18x8 with 235/40. I read you're running an 18x8.5 which I would also run the 235/40. 215/50 is strange for your 18x8.5-35 and the tech was a scrub for not looking at the factory spec and recommending 225/45 instead of 235/40 for a 8.5 wide wheel.

I actually have the Civic EX-T which comes with factory 17in wheels and 215 50R17 tires. I did upgrade to 18 x 8.5 wheels. At the time, I got 215 45 (not 50, my bad) R18 tires hoping to stay close to factory size. Now I switched rear tires to 225 45 R18. You are correct tho, 235 40R18s would be almost identical in size to stock. I am a little hesitant to go that low on the side wall cause theres tons of pot holes in my city and I think the larger wheel fills out the well more.

 

[Troy Jollimore]

The 18's look sweet and handle a tiny bit better (with the wider tires) in the dry, but yes, VERY susceptible to potholes, even with stock profile sizes. So the difference in aspect ratios between your tires and the 235s would not be enough to make a difference. Even a really good tire, with sidewall reinforcement/protection, probably wouldn't be enough against the types of potholes we see around here (2" or more deep. A Florida car group I was visiting once were going on about a huge pothole. I just kept squinting at where they were pointing and asking, "Where?").

Going back to 17s would be the best if you're really concerned, but it IS California! LOL... Those 225s give you almost 1/2" more protection (almost none, still) against the potholes. You'll take a loss selling those rears, so buying the fronts to match (our speedos are calibrated a little high, anyway) should be fine until this set wears out.

To answer your question, yes. You might be able to compensate a little by running your rear tires with less air. Not because of TPMS, but because the rolling diameter will be reduced a little. The ABS/VSA is seeing just enough of a difference in rotational speeds between your back outside wheel and the front inside in a tight corner that it thinks something is wrong. You can keep running it like this. The computer will keep screaming, and if you jam on the brakes like that it might not activate the ABS properly, if at all, but that should be it. You're not AWD, so there's no differential clutch to damage. You'll probably get fed up with all the warnings at some point, though...

 

[ClearEyes]

The 18's look sweet and handle a tiny bit better (with the wider tires) in the dry, but yes, VERY susceptible to potholes, even with stock profile sizes. So the difference in aspect ratios between your tires and the 235s would not be enough to make a difference. Even a really good tire, with sidewall reinforcement/protection, probably wouldn't be enough against the types of potholes we see around here (2" or more deep. A Florida car group I was visiting once were going on about a huge pothole. I just kept squinting at where they were pointing and asking, "Where?").

Going back to 17s would be the best if you're really concerned, but it IS California! LOL... Those 225s give you almost 1/2" more protection (almost none, still) against the potholes. You'll take a loss selling those rears, so buying the fronts to match (our speedos are calibrated a little high, anyway) should be fine until this set wears out.

To answer your question, yes. You might be able to compensate a little by running your rear tires with less air. Not because of TPMS, but because the rolling diameter will be reduced a little. The ABS/VSA is seeing just enough of a difference in rotational speeds between your back outside wheel and the front inside in a tight corner that it thinks something is wrong. You can keep running it like this. The computer will keep screaming, and if you jam on the brakes like that it might not activate the ABS properly, if at all, but that should be it. You're not AWD, so there's no differential clutch to damage. You'll probably get fed up with all the warnings at some point, though...

I blew out one of my tires in a giant LA pothole on a rainy Christmas eve 2021 and have been paranoid since haha. I lived inland at the time and had to drive 70 miles back on a spare. The car screaming at me is definitely not pleasant. I think ill just replace the front tires to get it to chill out.

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