Taller rear tire -- tune required?

[BC]

Great news! Have you already otherwise tuned your car? Or in order to make this one parameter change, are you essentially performing a tune? It seems like it should be something more akin to reading/clearing codes -- you're updating a setting to reflect changes, not hunting for more performance messing with timing, RPM limits, air-to-fuel, etc.

Yes my car has been running a custom tune since last November, Steeda CAI with restrictor removed, 91 octane.

So I will return to stock, update my SCT X4. Then load my Steeda tune back on, and while doing so go to the user setting area and set my wheel diameter. So yes I will be loading the tune back and setting wheel size at same time.
If you have an SCT X4 and try to change just the wheel size I am not sure if that can be done just by itself without loading a tune.

I will be trying this on Saturday or Sunday and will post back.

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[mikeyjobu]

:cheers:

Yes my car has been running a custom tune since last November, Steeda CAI with restrictor removed, 91 octane.

So I will return to stock, update my SCT X4. Then load my Steeda tune back on, and while doing so go to the user setting area and set my wheel diameter. So yes I will be loading the tune back and setting wheel size at same time.
If you have an SCT X4 and try to change just the wheel size I am not sure if that can be done just by itself without loading a tune.

I will be trying this on Saturday or Sunday and will post back.

 

[ahl395]

Can you use the Whipple Flare device to change the tire specs even if you dont have a Whipple SC?

Edit: nevermind if SCT can now do it I'll be going that route Thanks for the update

 

[BC]

Edit: nevermind if SCT can now do it I'll be going that route Thanks for the update

Forget SCT for changing wheel size….at least for now.

I updated my X4, went back to stock, loaded my tune + changed my wheel size in options. It still has the drivability issues Steeda told me about last January and this time I experienced it firsthand.

Hesitation in throttle response at random intermittent times.

I loaded my tune back in and set tire size back to stock and hesitation issues gone.

 

[Need4SpeedMotors]

Forget SCT for changing wheel size….at least for now.

I updated my X4, went back to stock, loaded my tune + changed my wheel size in options. It still has the drivability issues Steeda told me about last January and this time I experienced it firsthand.

Hesitation in throttle response at random intermittent times.

I loaded my tune back in and set tire size back to stock and hesitation issues gone.

good news

 

[BC]

good news

I was hoping it would work so I could correct my speedo!

It's hard to tell if it even set the speedo right. I wanted to set wheel size to 27" and the only choices around that were 26.9" and next was 27.1".
I used a GPS app on my phone and if the app is accurate I was still off by about 1.5 to 2 mph, so I'm not really sure the SCT setting even worked.

I am definitely sure about the hesitation though. Got on a ramp and after hitting 3rd I gave it a little more throttle and it did not respond right away. It kept doing that several more times during the day at random times. Really sucked...never had hesitation in throttle before.
I'm glad the tune loaded with wheel size back to stock fixed it.

 

[Need4SpeedMotors]

I was hoping it would work so I could correct my speedo!

It's hard to tell if it even set the speedo right. I wanted to set wheel size to 27" and the only choices around that were 26.9" and next was 27.1".
I used a GPS app on my phone and if the app is accurate I was still off by about 1.5 to 2 mph, so I'm not really sure the SCT setting even worked.

I am definitely sure about the hesitation though. Got on a ramp and after hitting 3rd I gave it a little more throttle and it did not respond right away. It kept doing that several more times during the day at random times. Really sucked...never had hesitation in throttle before.
I'm glad the tune loaded with wheel size back to stock fixed it.

that's so small that it wont cause any issues. But glad to hear it correct it.

 

[09jsw]

Good info here for when I get wheels. Thanks BC

 

[gsxr1300]

Can you use the Whipple Flare device to change the tire specs even if you dont have a Whipple SC?

Edit: nevermind if SCT can now do it I'll be going that route Thanks for the update

They sell one that just does rear end gear and tire changes.

I run 315/35-20 in the rear 1 inch taller than stock.

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