So how are those two, speedo/odometer, being affected now with just going from 255s to 285s tires with the stock 3.55s.. Is my speedo reading faster and slower and is the odometer doing the same???

 

Well, it's tough to say, because a tire with 255 width and a tire with 285 width may be the same outside diameter. For instance, my stock tires were 265/60/18's, my current ones are 285/60/18's. That is only a 1" difference in outside diameter, which would create about a 2mph difference on the speedometer/odometer. Your speedo would read 65mph, but you'd be going over 67mph.

 

Thats what I was thinking, just wanted to hear it from someone else, thanks. So right now speedo reads slower, odometer reads slower and am I correct in thinking rpms are lower?

Now if I have the same bigger tires then change the gears from 3.55s to 4.10s, how does that translate..

 

RPM is actual RPM, it is not dictated by the ECU or a programmer. The only thing that changes your RPM at a given speed is rear end gear ratio and tire size.

If you go up in tire AND change the rear ratio to something like a 4.10, your RPMS would go up, the speedo/odometer would be reading slower than actual, so you'd still need a programmer to correct it. Larger tires offset the higher gear ratio, but a 1" difference doesn't have a huge effect. If you were upgrading to 33's or bigger, it would have a larger effect.

 

[QUOTE=SoonerTruck;5084171]RPM is actual RPM, it is not dictated by the ECU or a programmer. The only thing that changes your RPM at a given speed is rear end gear ratio and tire size.

If you go up in tire AND change the rear ratio to something like a 4.10, your RPMS would go up, the speedo/odometer would be reading slower than actual, so you'd still need a programmer to correct it. Larger tires offset the higher gear ratio, but a 1" difference doesn't have a huge effect. If you were upgrading to 33's or bigger, it would have a larger effect.[/QUOT

Ok... then the comment I read some were that bigger tires and 4.10s would make the the odometer "count" or however you put, faster is false?

But i thought that changing gears when adding bigger tires brings the vehicle back to a stock setup, which to me would mean rpms wouldn't be any different than what they were when the truck was stock?

Already have the 33's on the truck, no gears..

 

The odometer will "count" faster if you upgrade to 4.10's, but leave the tires stock and don't tell the ECU you changed the gears or tires. It is true that as you go up in tire size, it offsets a higher gear ratio (like 4.10s) to be closer to stock levels. However, it takes a ton of tire size to completely offset it.

Basically, to get the same ~2000RPMs at 65mph with stock tires (30.5") and 3.55 gears, you'd need 3.73's to get you back to stock with 33's, or 4.10's with 35's.

 

Well as of right now like I said I have the 33s with the stock 3.55s and run 2000 rpms at 70mph.. Initially I was planning on going with just 3.73s, but the more and more I read people are saying 4.10s, that I wouldn't notice the 3.73s... So going off your first comment... if I changed the gears to 4.10s and didnt change the tire size from stock, then the odometer would read faster, correct? Like I said I have already changed the tires from 30s to 33s, so will putting 3.73s or 4.10s have an affect on the odometer..

I really appreciate your responses, I apologize if I'm sounding repetitive or asking to many questions, I just really don't know much about this, just trying to get as much info as possible before I go ahead with it..

 

You would notice it, but for $800+, it's not going to be a HUGE change. Your acceleration would definitely improve. The point they are trying to make, is that going only 1-step up (from 3.55 to 3.73) may not give you the bang for your buck. If you go 2 steps up (to 4.10's), you're truck will be a whole new ride in terms of haulin' the mail. Your truck is slower than stock with the 33's, 3.73's will get you back to stock, and 4.10's will get you a good bit faster than stock. All of this with minute fuel mileage decreases on the highway.

I bet you can barely, if at all, chirp those 33" tires from a dead stop without power braking. With 4.10s, they'll break loose of the pavement pretty readily.

 

Its all starting to make sense, thanks a lot man. Yea I can break the tires loose if its wet and im turning out of somewhere, lol, but thats about it. It would be nice to at least be able to spin those suckers on dry pavement from a dead stop.. Yea putting 3.73s will get me back to the factory stock, but even then it had a hard time spinning the tires, so a set of 4.10s will put me past stock but in a positive way... And with 33s and 3.73 I wouldnt need a programmer to adjust speedo and odometer, but if I did 33s and 4.10s then I probably need on since that would put me past a stock setup..

 

You got it. The good thing about the programmer is that most of them allow you to monitor a lot of things (tranny temp) that you normally couldn't, in addition to trouble code reading, etc. $400 is a lot, but it's not out of this world compared to all of the things you get with the programmer in addition to the extra HP/TQ.

 

Thanks again brother, think im ready to go ahead and buy the gears, I may have to ride it for a bit without the programmer, I only budgeted myself for the gears and labor cost.. Things shouldn't be to far off.. Now that unlike now wee my speedo reads less than actual just with the tires, with gears and the tires the speed should read faster than actual which would also make the odometer record faster as well, correct me if Im wrong...