Superchip for larger diameter tire?
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Junior Member
Joined: Dec 2000
Posts: 2
Likes: 0
From: Colonial Heights, VA, USA
Superchip for larger diameter tire?
Just a transplanted farm boy living in suburbia with a 1998 2x4 Super Cab 4.6L. Trips to the dump and construction sites for dumpster diving led me to replace stock tires with 265/75R16 on same 16x7 rims for height. Also periodically tow max GVW 3500# trailer. I observed the expected power loss and downshift under less load than should be. Understand I could go to the expense of a rear end change but.....the money? I also need to change the speedo sending gear - low cost. Will a Superchip fix my performance challenge?
Former Sponsor
Joined: Mar 1998
Posts: 13,385
Likes: 4
From: Virginia
Hi scout180,
Welcome to F-150 Online!
You're lucky in that because yours is a 1998 model, it still has a simple reduction gear you can change to restore speedometer & odometer accuracy. So then it's "just" a matter of how many fewer rpms you're turning due to however much taller your new tire size is over stock, and how far below the torque curve you are as a result. If it's not much change, say an inch to maybe an inch and a half or less in additional tire height, then you can usually get away with it, though you'll notice that performance and sometimes gas mileage too, is affected. Just how much it is affected determines whether or not you feel you can live with it, or if you really have to do a gear ratio change to compensate and get the engine back to turning the same number of rpm's it did before the tire change, so you're back in the torque band.
So in your case, you don't need any *custom* programming in the Superchip to correct the speedo, as you can easily fix the speedometer accuracy with the correct reduction gear. So you can save the custom programming fee to correct it in the program, and simply use the "standard" Superchip for your vehicle's computer code. Now, the operative question then becomes, will the Superchip help to offset this additional tire height, which has effectively changed the numerical gear ratio and thus reduced the amount of torque multiplication. Well, yes and no... no in that it can't of course change your gear ratio, but yes, in that the Superchip will help simply because it does increase power available at any throttle position from about 1200 rpm on up. It can't make up for say, a set of 33" tires of course, but with what seems to be from your description a rather minor change, less than 2 inches, I think you should be pretty happy with the results of the Superchip. It all gets down to just how much of a change in height between the 2 tire sizes.
If you'd like to go over this in more detail, please feel free to give us a shout, our contact info is just below.
Good luck with your truck,
------------------
Mike Troyer
Performance Products, Inc.
National Distributor of Superchips
(540) 862-9515
Email: mtroyer@compuserve.com
Performance Products F150Online Superchip ordering system: F150Online Superchip Ordering System
First National F-150 Online Rally Event Organizer
Welcome to F-150 Online!
You're lucky in that because yours is a 1998 model, it still has a simple reduction gear you can change to restore speedometer & odometer accuracy. So then it's "just" a matter of how many fewer rpms you're turning due to however much taller your new tire size is over stock, and how far below the torque curve you are as a result. If it's not much change, say an inch to maybe an inch and a half or less in additional tire height, then you can usually get away with it, though you'll notice that performance and sometimes gas mileage too, is affected. Just how much it is affected determines whether or not you feel you can live with it, or if you really have to do a gear ratio change to compensate and get the engine back to turning the same number of rpm's it did before the tire change, so you're back in the torque band.
So in your case, you don't need any *custom* programming in the Superchip to correct the speedo, as you can easily fix the speedometer accuracy with the correct reduction gear. So you can save the custom programming fee to correct it in the program, and simply use the "standard" Superchip for your vehicle's computer code. Now, the operative question then becomes, will the Superchip help to offset this additional tire height, which has effectively changed the numerical gear ratio and thus reduced the amount of torque multiplication. Well, yes and no... no in that it can't of course change your gear ratio, but yes, in that the Superchip will help simply because it does increase power available at any throttle position from about 1200 rpm on up. It can't make up for say, a set of 33" tires of course, but with what seems to be from your description a rather minor change, less than 2 inches, I think you should be pretty happy with the results of the Superchip. It all gets down to just how much of a change in height between the 2 tire sizes.
If you'd like to go over this in more detail, please feel free to give us a shout, our contact info is just below.
Good luck with your truck,
------------------
Mike Troyer
Performance Products, Inc.
National Distributor of Superchips
(540) 862-9515
Email: mtroyer@compuserve.com
Performance Products F150Online Superchip ordering system: F150Online Superchip Ordering System
First National F-150 Online Rally Event Organizer