New Tire Size found 235's to 245's

[Mopar1973Man]

Well, I can say that tire really hasn't changed much MPG wise... Started logging at July 2nd...

 

Edited July 22, 2018 by Mopar1973Man

[Marcus2000monster]

@Dieselfuture How has mpg been with the 285/75/17?

[Mopar1973Man]

I got to admit for the RV trip home was all uphill the whole way and I was beating on the truck pushing hard and fast. So the 13.9 MPG with towing the RV is actually an improvement. 

 

As for driving habits and gear use, I find that I can stay in 5th gear much longer now. 4th gear is rarely ever used on the highway but in the city.

[Dieselfuture]

1 hour ago, Marcus2000monster said:

@Dieselfuture How has mpg been with the 285/75/17?

I average 18 if it's mostly hwy, mix driving 17 or so sometimes a little less, but it's not easy for me to get over 18. If i drive 60-65 that's my best mpg range I believe and few times I've gotten 20+ towing around 10k I get 13-14 just depends. 

When I got my truck it had 295 something 16 and they were wider and a little taller then my current ones. I wanted to get toyo in extreme size 275/75/17 but they were out of stock which now I'm glad I didn't, so I got 275/70/17. With 295s I was probably 1-1.5 mpg less all across, but it's hard to tell as I started playing withe the quad and ran tunes with higher timing with original v1 tunes.

My next set will be 265/70/17 for less wear and tear and a bit better ratio. I don't think I'll ever put 235s or 245s on just because. 

[notlimah]

On 7/22/2018 at 5:23 PM, Mopar1973Man said:

I got to admit for the RV trip home was all uphill the whole way and I was beating on the truck pushing hard and fast. So the 13.9 MPG with towing the RV is actually an improvement. 

 

As for driving habits and gear use, I find that I can stay in 5th gear much longer now. 4th gear is rarely ever used on the highway but in the city.

 

According to your log, every other time you had the rv hooked up you recorded better mileage then 13.9, what am I missing? 

[Marcus2000monster]

@SilverMoose How has mpg been with the bigger tires??

[SilverMoose]

15 hours ago, Marcus2000monster said:

@SilverMoose How has mpg been with the bigger tires??

I'm up on NYC right now on vacation and wont be back until a week from tomorrow. I am still on the first tank.  I will let you know after I get back and fill up.  We rented a chrysler 300, what a different driving experience that is.

 

L8tr

D

[Guest 04Mach1]

On 7/5/2018 at 7:57 PM, dripley said:

It would be good to see if the 01 got the same mileage as the 97 on the same run.

Wont disagree on this, just not sure to buy the different size since the 265's have done so good every where i have used them. Might try a used set one day or check into the price of the narrower tires. 

 

 

Well not the same run but a trip to Gallup, NM  in the '01 gave me unexpected results. I did 142 miles of I-40 at 78 mph and topped off the tank with 6.12 gallons of fuel when I got back to Grants. I was quite shocked when I calculated the avg. MPG of 23.2. This is probably the best MPG I've seen from this truck in the almost 7 years I've owned it. All that I've done recently that could effect economy is the 4" exhaust.

 

Since my sig is out of date:

 

RV275 injectors

 

Unknown mileage on remanned VP44 as it was on the truck when I bought at 76k miles.

 

AD 100 with .50 fuel lines. Factory filter by-passed.

 

K&N CIA (I know, we've been through this conversation before)

 

Smarty on SW#1

 

HY35 turbo (with a sticky sometimes stuck wastegate) 

 

Rotella T6 5W-40 engine oil

 

Neglected stock 47RE auto ( can't say the last time it was serviced, getting closer to the 200k mark and figured might as well let it croak so I can build it and get a real tuner)

 

3.55 gears with 265/75R16 tires @65 psi.

 

4" exhaust

[Mopar1973Man]

Now see if you can repeat it again. Then you know you got the tune figured out. It could be a fluke too. Time to find out.

[Scottfunk]

Well I sold some equipment out of the garage that I don't use anymore so I'll be junkyarding a 4.10 gear set in the morning. Can't wait to see what kind of a difference it makes with engine load and ECT's. I'll post up some results although mpg's are beyond my capabilities since I still don't have an odometer. @Mopar1973Man I'd like to try the quad update that has the fuel data available but I am curious...Will this override the custom program @Me78569 wrote for me to use the Cummins programming with the Allison?

 

Also, shy of changing injectors I think I've done just about everything that can be done to squeeze every last drop of power out of the 24 valve. I use level 5 as my daily tune and have used level 7 to wipe out a couple snot nosed punks in Subaru' s but I've never even used level 10, so I feel like I'm going to stick with what I got there. Only thing I'd like to see is a little less lag time. I can count slowly to 3 from the time I mash the pedal until when the turbo kicks in and I was wondering...would looking into a vgt and the lilblackbox be the best way to get the turbo up to speed quicker or is it possible to use a smaller turbo to drive the hx35? I'm not scared to build adapters and piping and such I just want to know which would yield the most satisfying results.

 

[Mopar1973Man]

1 minute ago, Scottfunk said:

@Mopar1973Man I'd like to try the quad update that has the fuel data available but I am curious...

 

Be aware that that fuel data is BETA and not functioning very well when my last trip home shows I'm only making 4 MPG. 

 

 

[Scottfunk]

I just had the best luck at the junkyard today! I scoped out a Dana 70 that was under an E-350 last weekend that, according to the BOM tag, was a 70-U with 4.10 gearing. I studied up a little on it over the course of the week and decided that as long as I scavenged all the parts that go along with the r&p, like bearings and shims, I should be able to plug it in to my 70-2U and just reuse my old pinion bearing. Well I got the assembly out from under the truck this morning and lo and behold it's a 70-2U. 

Well the pinion nut kicked my butt and almost won. It broke my breaker bar so I tried a pipe wrench but it just wouldn't find purchase on the socket. Next I ran home and welded a huge nut onto the end of the pinion socket so I could turn it with my 3' crescent wrench. Success! This is all incredibly difficult after the axle assembly is removed from the vehicle and I probably won't try that again. I am looking forward to getting the 4.10's all setup under the Chummy and seeing what that does for my turbo lag and fuel mileage. Cheers!

[Scottfunk]

Ok so I got the gears swapped out and it feels really great. The turbo lag is all but gone, acceleration is insane, and the load seems to have come down some. Only problem is I can't get the iquad speedometer calibrated. According to the calculator at grimmjeeper.com my road speed at 2000rpm with the old setup was 85 mph and the new setup should yield 77 mph. The problem is when I change the gear ratio in the iquad from 3.55 to 4.10 the speed actually reads FASTER. Has anyone ever had to do gear ratio adjustments? What's the deal?

[Mopar1973Man]

ABS computer has two adjustments for gear ratio and for tire rev per miles. 

[Scottfunk]

I don't have an abs computer, my Allison tcm hands the speed straight over to the quadzilla. Guess I'll have my tcm adjusted. 

[Ironforger]

Great thread. 

02 3500 quad cab 2wd 6speed.  3.55's 

 

I have the factory size 235/85R16's .  Glad I found this thread as It will soon be time for a set of 4 tires for the rear duallys.  I may just try the 245's.

 

I'm not even going to think about mpg's / economy at this point. (13 mpg last time I checked).  I have a huge service body on the truck. Ridiculous wind drag.  Planning to fabricate aerodynamic wings at some point. 

 

But I'm curious, do you think 3.73's would be worth considering?   Not concerned about power, (I feel like the truck is way powerful as is without any mods, but considering an edge or quad in the future)  but would 3.73's help my mpg's ?   What would top speed be in 5th gear with the 3.73's?  I try not to do any towing in 6th gear since I've read that towing in 6th is not a good idea with the NV5600 / high trans temps etc.

 

Thanks

[Mopar1973Man]

27 minutes ago, Ironforger said:

But I'm curious, do you think 3.73's would be worth considering?

 

245's will put you close to the 3.73 ratios (3.69:1) without changing the gears. 

 

With the 245's with 3.55 rear gears 66 MPH is a perfect 2k on the tach. Then at 80 MPH your at 2,400 on the tach. 

[Ironforger]

1 hour ago, Mopar1973Man said:

 

245's will put you close to the 3.73 ratios (3.69:1) without changing the gears. 

 

With the 245's with 3.55 rear gears 66 MPH is a perfect 2k on the tach. Then at 80 MPH your at 2,400 on the tach. 

 

Is your 02 a 5 speed?

 

Here are my speeds & corresponding rpm's for my 02 3500 6 speed NV5600 & 3.55 gears

 

5th gear:

35 mph  1600 rpm

45 mph  2000 rpm

55 mph  2500 rpm

65 mph  3000 rpm

 

6th gear:

60 mph  2000 rpm

66 mph  2150 rpm

80 mph  2600 rpm

 

Wondering what 245's would do for this?

 

I kinda like the current spread shown above. Do you think I would see any improvement with 245's?  Anyone here running 245's with a NV5600 6 speed and 3.55 axle ratio?

 

 

I sold my 1990 W250 4x4 a few years back. It was a 5 speed, but not sure what the axle ratio was. I do recall I hated the transmission ratio spread. The ratio jump between 3rd and 4th was too much (revved high in 3rd,& revved low lugging/struggling in 4th). Although 4th gear was the 1:1 straight through ratio on that truck.

 

I love the fact that I can putz around town in my 02 3500 6 speed NV5600 doing 35mph in 5th gear at 1600rpm without lugging. 

[Mopar1973Man]

Just remember...

 

NV5600 6th gear -> 0.73 - 0.75 <- NV4500 5th Gear

NV5600 5th Gear -> 1:1 -- 1:1 <- NV4500 4th Gear

 

2 hours ago, Ironforger said:

The ratio jump between 3rd and 4th was too much (revved high in 3rd,& revved low lugging/struggling in 4th)

 

No longer an issue with 245's. I'm typically in 4th gear (1:1 direct) on NV4500 by about 30 MPH. You can cruise 30 MPH at 1,200 RPM's. 

2 hours ago, Ironforger said:

80 mph  2600 rpm

 

With my NV4500 in 5th, 3.55 rear end gears and 245's on for tires I'm 200 RPM's lower at 2,400 at 80 MPH. I seriously wonder if your rear axle is a different ratio.

[Tractorman]

8 hours ago, Ironforger said:

Anyone here running 245's with a NV5600 6 speed and 3.55 axle ratio?

 

I have this setup.  Just last week I changed over to four 245/75R16 Yokohama tires.  For the previous 297,000 miles I ran 265/75R16 Michelins.  The 245's are performing just like Mopar1973Man states and I like the benefits - less steering effort, better braking (with and without exhaust brake), and more time spent in sixth gear.  One more benefit - the truck is 1/2 inch closer to the ground.

 

Also, I do tow in sixth gear if my road speed is higher than 45 mph, which is most of the time.  And, if the grade is 5% or less I will stay in sixth gear just as long as my road speed is 50 mph or higher and the speed can easily be maintained.

 

6 hours ago, Mopar1973Man said:

With my NV4500 in 5th, 3.55 rear end gears and 245's on for tires I'm 200 RPM's lower at 2,400 at 80 MPH. I seriously wonder if your rear axle is a different ratio.

 

I agree with Mopar1973Man here.  Your engine rpm numbers don't match the road speed numbers for 3.55 gears.  Your 235/85R16 tire and my previous 265/75R16 tire are virtually the same diameter.  With my 265 tire the tach would read 2000 rpm @ 50 mph in fifth gear and right near 2000 rpm @ 70 mph in sixth gear. 

 

Thanks, Mopar1973Man, for introducing the 245 tire idea.

 

- John