Just picked up my new 2014 Sahara Unlimited yesterday. I put on front and rear Smittybilt SRC bumpers, Rock Star II rims and Mickey Thompson ATZ tires. The jeep is very sluggish vs the jeep I test drove. I expected a little difference but........I know my mileage would suffer a little, but wow. It is just because its new? Tires causing this? Bumpers too heavy? or all of the above. I will be using this for my DD, but don't want to go broke at the pumps. Any input would be great .

 

What size tires?

 

Lt 305/65r17

 

I wouldn't think that'd make much of a difference, but I jumped from stock to 37's. It's going to have some effect as the bigger diameter is harder to turn so without a regear it'll be a little slower off the line.

 

What is your gear ratio? I'm guessing 3.21s because 3.73s should be pretty good with 33s. A regear would help but at least a reprogram of tire size in the computer. It really helps with shift points on an auto.

 

Thanks. How would I get the computer reprogrammed? You would think my dealer would have done that since I bought the jeep with this tires installed?!

 

Most dealers will not reprogram beyond the largest stock tire size which is 32. I doubt they reprogrammed yours to 32 but if your stock wheels were less than 32 then you should have them reprogram them. There are several reprogrammers like flashpaq, flashcal, and Diablo if you want to do it yourself. I used an aeroforce interceptor to reprogram mine.

What size were stock tires and is it auto or stick?

 

Auto Trans. Actually the stock tire is P255/70R18. Gear shifting does seem off a little, and may account for the sluggish feeling.

 

Gearing depends on if you have the tow package or not. If you don't then you have 3.21. If you do then you have 3.73.
Getting a tuner and doing it yourself will help regain some of it back. Will also make sure your speedo is accurate. Correct the shift points since you have an auto. Ultimately re gearing is what you will need to have that test drive feeling again especially if you plan on adding any more weight via mods.

 

This one came with the max tow package. I have been trying to find the gear ratio, but I have not had any luck. So if I am reading this correct, a reprogram could help a little. When I look at the weight of the two bumpers, I find it hard to think that 300lbs or so, would effect a the performance of a jeep weighting in at 4500+lbs to begin with. But, hey, I don't know jack about this stuff. I just want it to look cool.