Speedo doesn't work after wheel swap

Tombonombona

So two days ago I swapped my wheels from the factory Sport rays to my "summer" set. They are a little big so rolling diameters will probably be off... My issue is that since I swapped them my speedo doesn't work, abs is off, trac is off, and mykey light is on. Car also doesn't like shutting off ( have to hold the button).

In the previous years I've ran these wheels I haven't had an issue, apart from when I had it on the dyno. Same symptoms and cleared up in a few km.... But this time I've done probably close to 300 miles ish now total and it hasn't fixed itself. I did leave the battery unhooked overnight to see if that would help clear anything, it didn't.

Another thing I noticed is when I give it some gas and the rear slips a bit in second or third is that it seems to correct itself, all warning lights go away, speedo works, but that only lasts for a minute or so after.

Does anyone have any ideas or tips and tricks? I plugged my computer into it and of course it comes up with the speed sensor code. But its fine with the stock wheels on.

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Tom B.
Exotic Speed R2 Titan Catback-GTM Stage 2 Supercharger 522 whp on a mustang dyno
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cooltoy

Can you provide specs of your "summer" wheels?

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Tombonombona

275/35/20 front 315/35/20 rears on Pilot Super Sports.

So for comparison. The stock rear compared to the stock front is 0.4 inch less and 5 revolutions per mile more. While my summer set is 3.5" bigger around and 28 rev per mile less comparing back to front

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Tom B.
Exotic Speed R2 Titan Catback-GTM Stage 2 Supercharger 522 whp on a mustang dyno
2004 Subaru STi *SOLD* *WRITTEN OFF*

BGTV8

By my calculations, your fronts are 673mm in diameter and rears are 697mm in diameter and the difference is ~24mm or an inch, which is going to be too much of a difference for the electronics. OEM diameter differences are ~5mm.

Are you sure these have been run on your car before ??

cooltoy

The difference in diameter of the back tires and the front tires has to be below a certain number (I cannot remember what that is, 3mm I think). Anything greater then that number messes up the computer.

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Tombonombona

But I've driven it for the past three years without issue with the bigger tire setup. It's only after I put them on for this summer did I have an issue

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Tom B.
Exotic Speed R2 Titan Catback-GTM Stage 2 Supercharger 522 whp on a mustang dyno
2004 Subaru STi *SOLD* *WRITTEN OFF*

cooltoy

Not the first weird thing to happen in Saskatchewan.

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Jsolo

Start with checking the wheel speed sensors. Make sure they're still there and not damaged.

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Rusty

Put your other set of wheels and tires on and see if you still have the problem. If you still have the problem. Then you know it's not the wheel and tire combo.

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Tombonombona

So I swapped back to the stock wheels, all the gauges and warning lights fixed themselves after driving for like fifty feet... I put the "bigger" wheels on and within a mile, I lose my speedo, trac, abs, rev match, and the car doesn't think the key is in it so it's hard to turn off...... but if I go around a tight corner and give it a bit of gas, it seems to fix itself, but then after a mile I lose everything.

Very confused as to why these wheels worked for two years and now they don't. I really don't want to have to spend $1300 on new rear rubber when the ones on there have been barely used.

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Tom B.
Exotic Speed R2 Titan Catback-GTM Stage 2 Supercharger 522 whp on a mustang dyno
2004 Subaru STi *SOLD* *WRITTEN OFF*

SouthArk370Z

My guess is that one or more of the speed sensors is aligned so it just barely works with the stock wheels. Something about the new wheels disturbs the magnetic field enough to mess up the sensor signal. It may help to move the sensor(s) a little closer to the target.

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240se

If they worked before then maybe a little more air presure in the front tires and a little less in the rear may get it to work. You really need to get tires that are closer in diameter though.

Edit: What tire presures are you running now?

OptionZero

Even besides the speedo issue, those tires are significantly taller than stock

Better sizes would be 275/30/20 and 315/25/20

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barncobob

I leave everything stock size and have never had any of these problems, just my.02 cents..

Tombonombona

I would have liked stock sizing. At the time I bought them, few years back... I was assured by the tire person that all will be good... and for two years all was good... and forking over a big chunk of change for new rears when these are practically still brand new is a hard pill to swallow.

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Tom B.
Exotic Speed R2 Titan Catback-GTM Stage 2 Supercharger 522 whp on a mustang dyno
2004 Subaru STi *SOLD* *WRITTEN OFF*