Well I would think that the speedo being off would also lead to the rpm being off because it would say your going lets say 20 mph if your actually going 15 than the rpms will be inflated artificially I would think? Which could lead to you shifting too soon or too late. Sent from AutoGuide.com Free App
The rev counter is based off of engine rpm and is not related to the rear wheels at all. So the revs indicated will be unaffected by the rear wheel diameter. If he isn't using the wheels for anything more than competition, it'll be fine leaving it as is. However since you're reflashing the car to 93R when you autox and back again when you drive streets, why not just have bama send you an updated 93r with your comp wheel size? The SCT device carries 3 tunes anyways. Just change label to "87P Street" and "93R Comp".
Car: 2011 Black Mustang v6, 6-Speed Auto, Premium Package
MODS: KW Variant 3 Coilovers w/ Maximum Motorsport CC Plates | J&M Adj. Panhard Rod | AEM Intake | Bama 91R | Borla S-Type Axle-Back | Boss Front Conversion w/ Saleen Grille + Foglight w/ Auto Headlight | Boss Rear Diffuser | Forgestar F14 18x10 +42 w/ Nitto NT05 275/35-18 (all around)| BMR LCA | SVT GT500 BBK|
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Buttonwillow(CCW)-Let's not talk about it