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Old 02-24-2014, 06:15 AM
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Tire size (CRD specific version)

I know a few of you have moved up to a somewhat larger tire size. How (if at all) has the driving experience changed?

I've read about which tires will "fit" and know that topic has been beaten to death. But our trucks drive differently than the gas burners. Is there a noticeable difference in power/efficiency with moving a size up?
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Old 02-25-2014, 10:55 AM
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Re: Tire size (CRD specific version)

I've got 255/70/18 blizzak dm-v1's on it for the winter. Being a snow tire dry grip(mainly braking) is diminished some, but overall it's not horrible. It's hard for a baseline as to mileage because I put them on before the jeep got home from the dealer as we had them on our '13 Hemi.
On the hemi, mileage in winter with the bigger rubber 32.1 vs 30.5 stock 20's dropped from 15-15.5 down to 13-13.5. Right now the wife is getting between 19-20.2 overall. That's also impacted by the jeep getting remote started sometimes 3 or 4 times a day and a fairly heavy throttle...her words "I've got things to do and places to go". I'd rather her do that than get in it cold though.
I'll probably ditch the factory tires in the spring(with 200 miles of us test driving the jeep on them) for 275/55/20 and not worry about a couple mpgs. I'll put Bilstein shocks on it to, so there should be any impact on handling, if the bigger shoes increase braking, I'll throw on EBC rotors/pads.
I would say, you want bigger rubber, put it on and enjoy it
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Old 02-26-2014, 09:52 AM
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Re: Tire size (CRD specific version)

I have the 2014 CRD Overland with ORAII...

I changed from 265/60r18 to 275/55r20 (Cooper Zeon LTZ XL). Drove on the originals for about 500 miles. The new wheels/tires have about 2500 miles.

No significant difference in the ride - Noise is minimal, handling is slightly better, resistance does not feel any different.

Of course the speedometer is slightly off but it does not bother me. I drove 1700 miles between Denver CO and St George UT this week and average 28.2mpg (calculated at refill). That was mostly highway but also included several mountain passes and a few mountain climbs to radio sites on unimproved roads. Otherwise I am averaging about 25mpg driving around town on the new setup. I was getting about 26mpg around town on the original tires.
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Old 02-26-2014, 12:57 PM
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Re: Tire size (CRD specific version)

I have 275/65r18 Duratracs on my diesel. With proper tire pressures the ride quality has not really suffered at all. Noise is slightly higher but not bad at all. Both dry grip and wet grip are improved, while braking on snow/ice is much better than stock. It id hard to tell the effect on gas mileage since the larger tire affects the onboard calculations but on a recent road trip i was reading 33-34mpg at 80mph on flat highway with the bigger tires and 3/4 inch lift they provide to the vehicle in all suspension settings. I was told that my mpg was probably slightly higher than the onboard reading due to the tire size. So 35mpg with 32 inch tires at 80mph is pretty good. 80-85mph serms to be where my diesel gets its best mpg. Might be time for a radar detector.
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Old 02-26-2014, 06:45 PM
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Goonbash- what tire pressure are you running? I've tried 32psi then 35 and now up to 40. I like the ride at 40 the best with the Duratracs.
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Old 02-26-2014, 06:50 PM
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Re: Tire size (CRD specific version)

I went the opposite way. The tire shop set them at 40. I thought the ride was a little harsher and bouncy so i dropped them to 36. Liked that better. Now i run them at 34.

My experience with my Rubicon and higher load rated tires was that you have to run fairly low pressure to get even tread wear and smooth ride.
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Old 02-26-2014, 09:08 PM
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Re: Tire size (CRD specific version)

Quote:
Originally Posted by Goonbash View Post
I have 275/65r18 Duratracs on my diesel. With proper tire pressures the ride quality has not really suffered at all. Noise is slightly higher but not bad at all. Both dry grip and wet grip are improved, while braking on snow/ice is much better than stock. It id hard to tell the effect on gas mileage since the larger tire affects the onboard calculations but on a recent road trip i was reading 33-34mpg at 80mph on flat highway with the bigger tires and 3/4 inch lift they provide to the vehicle in all suspension settings. I was told that my mpg was probably slightly higher than the onboard reading due to the tire size. So 35mpg with 32 inch tires at 80mph is pretty good. 80-85mph serms to be where my diesel gets its best mpg. Might be time for a radar detector.
I LOVE Duratracs, I had them on my H3 for 3 years (and 3 very bad winters) and they were unstoppable. I was out driving around in a record 4ft noreaster we got last feb in them, never had an issue with traction. If I had to pick one AT tire to run all year round, it would be the Duratracs. I concur that they're a bit louder than stock, but not horrible.

Re: the size difference. That's the exact reason I didn't opt to upsize my tires. I didn't want to throw off my MPG calculations which I've been following so intently I don't really think 30+ MPG is possible at 80+ MPH, I think the size change is definitely greatly inflating the MPG calc.
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Old 02-26-2014, 09:16 PM
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Re: Tire size (CRD specific version)

Nope. The calculations would read low just like the odometer and speedo with larger tires.

the car thinks you are driving less miles than you really are.
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Old 02-26-2014, 11:41 PM
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Right, my 255/70/18 are about 5% bigger than the stock set up, so when the wife think she's going 70, I remind her she's going a bit faster, roughly 73 ish, also mpg are lower also. It said 20.7 tonight, so I'm guessing its in the 21.5-22pmg range. I'll take that over the 13.5 the hemi got in the winter, but then again I didn't buy it for mileage, if I wanted that I would get a diesel Jetta and tune it. Going to 275/55/20 in the spring, over the course of the lease may save me a few miles though shhh don't tell jeep
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Old 02-26-2014, 11:54 PM
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Re: Tire size (CRD specific version)

Exactly. And the larger tire equates to less rpm at a given speed. So I am not sure what Thebc2 was talking about. I was reading 33-34mpg at 80mph on the speedo. So that would equate to 35ish mpg at 83 mph, on flat low traffic Interstate, just like i said above. When i was steady at 65-70mph my mpg dropped to 27-28 reading which would be 29-30mpg actual.
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Old 02-27-2014, 04:32 PM
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Re: Tire size (CRD specific version)

I want to know your secret to getting 30+ mpg at 80+ mph WITH bigger tires.

Are you juicing?
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Old 02-27-2014, 06:51 PM
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Re: Tire size (CRD specific version)

No secret at all. We should change your forum name to 'DoubtingThomas'. There is a sweet spot with turbo vehicles where you arent making noticeable boost (which sucks gas) but where the compressor wheel is still helping the engine to be very efficient when you have larger tires that sweet spot rpm and throttle position happen at a higher road speed because bigger tires give less rpm at the same speed as smaller tires. Also bigger tires hurt gas mileage under acceleration especially stop and go stuff but once the car is at speed and consistently travelling at highway speed the effect on mpg is negligible under those particular circumstances. Pay attention to your own vehicle and maybe you will figure it out.
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