Largest street tire size with NO power loss??

[resistance]

As I have mentioned in another thread, I have 245/75/16 Cooper STT's on, and I have lost serious power. I'm about to go on a long road trip and I will not regear, so I'll buy smaller street tires.

Since my vehicle is lifted, stock size tires looks way too small on it. So what is the largest street tire size I can get without losing power? 245/70/16?


(I had asked about this in one of the posts in the other thread, but since the title was not about this subject, I'm not sure if everybody heard my question. Sorry I hate starting new threads when it's not really necessary, but I'm about to buy the tires, so I had to.)

 

[DirtyKK]

Go with a narrower size and highway tread design for the least rolling resistance. Also look for something light in weight. If its lifted and has street tires its gonna look ******** anyway so I would just go stock. My 2 cents.

 

[KeswickDave]

Any increase above your original stock tires will result in some power loss, the question would be how much... I think many of us who haven't lifted yet have gone with the 245-70-16's - generally considered the maximum size without a lift.

That is what I'm running (Bridgestone Dueller Revo's), and to me, it has not made a noticeable difference in power or economy.

I haven't looked into getting the computer re-programmed for the different tire size myself, but some say that may help as well.

Dave

 

[tjkj2002]

As I have mentioned in another thread, I have 245/75/16 Cooper STT's on, and I have lost serious power. I'm about to go on a long road trip and I will not regear, so I'll buy smaller street tires.

Since my vehicle is lifted, stock size tires looks way too small on it. So what is the largest street tire size I can get without losing power? 245/70/16?


(I had asked about this in one of the posts in the other thread, but since the title was not about this subject, I'm not sure if everybody heard my question. Sorry I hate starting new threads when it's not really necessary, but I'm about to buy the tires, so I had to.)

The tire size that came on your KJ when it rolled out of the factory as that will be the largest tires you can run without any power loss,make sure you get the mushy "P" rated tires also.

Personally I would regear as it is cheaper then buying 2 sets of tires and 2 sets of rims.

 

[HoosierJeeper]

I'd go 245/70/16 or 235/70/16, depending on availability. Since you're lifted, they'll both look small anyway, so I'd just get whichever size is readily available in what tire you want.

 

[resistance]

You are right, so the title should be "Largest street tire size with minimal power loss". BTW, I'd definitely get stock size, but they look really small, even compared to 245/70's.

I'm planning to get 245/70/16 Kumho Road Venture APT KL51, but I don't know what the result will be in terms of regaining power. Any loss below 10% is ok, I can live with that

 

[SurfGuitar141]

OR.....you could try this if you haven't already.....

Change out stock air box with a K&N cold air intake, a fresh set of Autolite double platinum spark plugs, and replace your stock muffler with a high flow muffler.....(Thrush, Dynaflow, Magnaflow)...

These improvements certainly can't hurt, and you may get back the power you lost with the bigger tires.....

 

[tommudd]

remove the lift and install stock size then you'll be back to where you started and will be good to go on mileage.
Anytime you change one thing on a vehicle it changes something else.

 

[osufans]

you might be able to get away with a 235/80/16. it will be as tall as the 245's but narrower, which should reduce some rolling mass and resistance, and will be felt as less power loss.

just throwing that out there...not sure if those do fit or not though.

 

[resistance]

Thank you for your replies. I purchased 245/70/16 kumho apt kl51 street tires and used them during my trip. Well the power is mostly back, so is the silence! I'm happy with them so far. But for a better performance, it's clear that you have to go back to stock size.

But I don't understand why the gas pedal still does not respond well driving uphill or need instant acceleration. When I need the torque while driving, I hit the gas and nothing happens instantly. I understand that the vehicle is heavy; but you'd expect more from a 3.7 lt engine..

 

[HoosierJeeper]

I got those same tires on my LR3...they are great street tires.

 

[Ry' N Jen]

But I don't understand why the gas pedal still does not respond well driving uphill or need instant acceleration. When I need the torque while driving, I hit the gas and nothing happens instantly. I understand that the vehicle is heavy; but you'd expect more from a 3.7 lt engine..

How much extra weight did you have packed in your Jeep on your long road trip?

Even with 750 lbs. of camping and off road equipment and 245-75-16 M/T R's our Rig had excellent throttle response!
(That includes fully loaded roof rack, cargo basket, 11 cubic foot ski box= greater wind resistance!)
Just didn't use o/d on the steeper inclines.

Perhaps your engine needs a tune up?

 

[resistance]

Perhaps your engine needs a tune up?

I'm not sure but it seems likely. I didn't have much weight at all, only a couple of suitcases. If I'm driving above some certain speed and I hit the gas to accelerate, sometimes I get no response. This feels unsafe when passing other cars.

What exactly needs to be tuned in the engine? The ECU?

 

[HoosierJeeper]

Spark plugs, oil change, new air filter....just stuff like that.

 

[Ry' N Jen]

Clean the throttle body as well.

 

[resistance]

Well I have changed all fluids, air filter but the old spark plugs are still there. I had to change most of the exhaust system, because some damaged parts were making a loud noise.

Throttle body cleaning.. I don't know how it's done..

 

[tjkj2002]

Well I have changed all fluids, air filter but the old spark plugs are still there. I had to change most of the exhaust system, because some damaged parts were making a loud noise.

Throttle body cleaning.. I don't know how it's done..

Have the intake system professionally cleaned and then have the plugs changed,will make a world of difference.Some will say just use seafoam and do it yourself but it just is not the same and can end up with a blown engine or damaging the cats.

 

[resistance]

It's all done. Spark plugs changed, intake system cleaned. All fluids and air filter were already changed. Engine inspected with the digital hand unit (sorry I don't know what it is called) and there is no error.

It feels only a little bit better now, but I'm still not sure if this is the real power capacity of this vehicle. 3.7 l. is a big and powerful engine, but it doesn't feel like that KJ is a rare vehicle around here, so I couldn't try another one, therefore I've always wondered how other KJ's feel like. I mean is this it, or is there something wrong?

It's hard to compare and understand by just asking questions on the forum. How's your acceleration (0-100 kmh/0-60 mph in seconds)? Do you feel the power pushing you into the seat when you hit the gas? Many people reach that speed in 9 seconds or less, like in the video below:

http://www.youtube.com/watch?v=-rJIHCWqs1I

 

[HoosierJeeper]

9-10 secs is about right. KJ's aren't speedy by any means...

 

[resistance]

0-100 kmh in 9 seconds is not bad, especially for a 2 ton brick.

Maybe there's a hidden potential, but the main problem here is, KJ shifts too soon. When you begin climbing up the torque curve, it shifts up and everything is gone..

As far as I have read, it's a known issue for many people in here and LOST.