Got some new Coopers 3 weeks ago. I went from 265/75/16 to 285/75/16.

While I expected to loose some power starting off, it feels like I lost more than expected.

Anyone else notice this? Is there any way to trick the computer to make up for it?

Thanks

 

Im going to guess you have 3:55 ratio as well?
Going to a larger does indeed affect the final drive ratio and it forces more energy output to get the same movement.
Trucks running the 4:10's can absorb the larger tire with less difficulties.
I went from the stock wheel/tire combo to a 33X12.50X16.5 and it did make a difference (I too have 3:55's).

As far as tricking the computer, there are aftermarket chips you can purchase that will provide more power output via timing and/or fuel.

Rich

 

you can have the trucks computer reprogramed so your speedo is correct, if you have an auto this will correct your shift points

and yeah I noticed a power drop when I went from my 245's to the 285's, it's to be expected cause you just geared the truck higher .........only real fix would be to go with lower gears

 

What Tranny? I assume it's an auto..to be noticing that much difference.

Re-Calibrate your computer for new tire size...need Revolutions per Mile...see here http://www.sjdsm.com/tech/tire_size.htm

Also adding an Edge EZ or equivolant will more than make up difference.

RJ

 

I have a 95 Chevy right now (Hopin to get a 12v in the next month or so) so I went from 265/75/16 street tires to 32X11.50/15 Buckshot mudders and I couldn't really tell a difference and I have the tall 3:42 gears in my truck but it's modded a little.Duals,Custom Chip,Underdrive pulleys,Injector spacer,TBI spacer,and a K&N 12 inchx3 inch open element filter.


JUst figured with all the torque of a diesel you wouldn;t notice it that much cause if I get a diesel I want to run Super Swamper SSRs.33x.14.50s on a 16 inch rim.

 

I went from stock to 285's for the past few years and hardly noticed any loss. Now I put on 315/70/17 BFG's and I can feel it big time. I am in the same situation. I didn't think it would be this bad with the 3:55's and an automatic. I need to fix this soon.

 

I cant figure this out. Stock tires were 245/75/16 and now I have 315/70/17. How does this compute? I need to get the truck re-callibrated and am not sure what it needs to be set at.

 

The main reason the auto feels gutless with big tires is that the larger tires exaggerate the slippage in the stock converter (more load on the converter).

You won't hear of this problem much with guys who have modded trannies with tight converters.

The EZ might help, but it's not going to fix what's really wrong. It's the converter.

You rarely hear about larger tires killing performance with the stick shifters either...

Justin

 

If your saying can't figure out the go to web Site...just tried it for your tires. Works fine.
1st # = MM
2nd # = Aspect ratio
3rd # = Rim size
put in 70 mph and click on compare!
RJ

 

Never noticed slippage with my stock tranny and 285's, but was fairly low mileage. Larger tires will definately add stress to stock converters.
When DTT questions prospective customers about their vehicles, they get fairly serious about wanting to know of any plans for larger tires.

Maybe Pogorules had some tranny issues/problems before new tires?

RJ

 

Maybe so. 285s aren't much of a step up if your truck came with 265s like mine.

But take a truck with 245s and put on a 285, 295, or even 315 and the OEM converter will see a huge increase in stress. I don't think an aftermarket converter would even sweat it, but the stocker probably does.

Justin

 

I went from stock tires on my 2500 to 315/75R16 but I also dropped in 4.10 gears and a rear locker. I didn't notice any difference from stock as far as acceleration but did notice tranny slippage. I put in a 3 disc torque converter, valve body and shift kit and it's as good as new.

 

Thanks for the reply everyone.

Yes, I have 3:55's and an auto.
The truck came with 265's.
No, there were no tranny problems.

Reflashing the computer to reset shift points.... Any drawbacks? Any chance of the *********** screwing up my mileage? How much does it usually cost?

 

Dnn't believe it's a full reflash...just a reset of one item...# of rev's per mile.

But it is my understanding that the reflash problems are in the past and 02's have had no problems with reflashes.

RJ

 

I went from 265 to 285 with mine and didn’t notice a difference.