New Tires & Wheels - What to do?

[Matt400]

I just got these and now think I bit off more than I should have so dunno what to do. The problem is we took the plunge on an RV that is over twice the weight of the old one (after buying the tires & wheels) so with 3. 73's , auto trans and 33. 5" tall tires its just fine unloaded but I like to tow in OD at about 60-65mph which puts the R's kinda low. When shopping for tires & wheels I wasn't planning on the change in RV.



Do I leave em on and just deal with it or trade someone?

Brand new 295/70R17 Toyo M/T's -

 

[gsbrockman]

Do you still have the stockers ? If so, swap'em out when you're taking a road trip if the new gearing is undesireable.



Greg

 

[Spooled-up]

I like Greg's thinking. It would give me an excuse to get my shop with a 12K lift and set up the compressor with the impact wrench, but that's just me.



What are your rpm's at the speed you'll be towing the trailer?



What did you get for a trailer?

 

[SierraRam]

If you really like the look then I would think about regearing to 4. 10s, your 33's are not a lot taller than stock. Do you have any power adders? A smarty Jr or EZ may be enough to make up for the tires without killing you stock transmission too.



SR

 

[Matt400]

I don't have the stockers anymore. If I did trade someone for smaller tires & or wheels I would just leave em on I think.



If I tow at 63 mph in OD I have just 1600 RPM, towing at that speed in drive gives me 2400.



We bought a Crossroads Kingston 5th wheel that is little over 9K empty and just under 14K gross.



The look is nice but gotta have function too. While it would be a hit in the wallet I think I would trade someone for there stock alloys & 285's maybe just a Edge EZ or even their mileage box would do, Only mod I have on the motor is a cam.



Running the numbers though I see that would give me just 100 rpm which doesn't sound like much but the difference in power from 1600 to 1700 seems substantial.



Gearing to 4. 10's would be good, wish I didn't have the added cost of a 4x4.

I was playing with calculations just for fun and it seems 5. 38's would give the same 1st gear ratio of the 68re & then add a GV unit in double overdrive would be just right. That would be a fun mod for a 4x2 model.

 

[MickeyMiller]

Matt,



Sierra Ram is right! Now you have the perfect reason to get a Smarty JR! Boost the power and you won't care about larger rolling radius.

 

[MegaRocks]

Same with the Superchips Flashpaq. In the performance tow setting you will get all your power back and then some!

 

[Slicks]

Matt I think you will be fine, we pull a 20,000 pound 5er with our dually and I run 3. 73's and 34. 1 inch tall tires. The truck holds overdrive in all but the mountains(we travel in the mountains a lot). The truck in only using a smarty right now, the only trouble I have is the amount of smoke when pulling long grades. The EGT's are well within reason, but the smoke is a killer. That is getting fixed in 2 weeks(MPI twins).

 

[Matt400]

The Jr. sounds interesting, I would like to see the smoke issue resolved. Don't want to be red flagged.



Slicks- where are you getting your twins from?

 

[Motorhead]

Do you still have the stockers ? If so, swap'em out when you're taking a road trip if the new gearing is undesireable.

Greg

I bought a set of stockers for just that reason only mine is the LATE G56.

 

[Slicks]

Nathan wright, maximized perfomance inc. He is in boise, id.

 

[CoastyAV8R]

Something else to think about is what are those tires rated at?

 

[Slicks]

Matt, i also just bought a us gear underdrive unit.

 

[Paddy McMahon]

The tires you have are rated at 3970 lbs each at 80psi according to the Toyo website. I have the same tires and issues. I simply use the tow/haul function to keep out of overdrive and avoid smoke or lugging on the hills when travelling at 50-60mph. I only tow a skid steer so my tow weight is way less than yours. Anyway, other than the road noise they really are great tires ... . you might want to postpone taking a bath on them by selling/trading them off until you give them a little time under your truck to see how you warm up to their performance.

 

[Matt400]

All good input, its great to post up your thoughts for feedback, thanks everyone!



I have decided to keep em, haven't picked up our new RV yet. . maybe this weekend and towing home will be a 2500 foot climb in 60 miles. They do look good and the weight rating is hard to beat without going to 19. 5's

 

[Matt400]

Nathan wright, maximized perfomance inc. He is in boise, id.

Are you going to use your stock turbo with their kit?

 

[Slicks]

Twins

Originally, yes. Then i decided with the mileage, the stock one should be rebuilt. So instead i went with a 62/13 ss polished with a s400 polished & ceramic coated exhaust housing, ceramic coated manifold, all duct work & flanges will be 304 ss, and i just bolted on my silverline 5" 304 ss exhaust. All i can say is if it don't run good, it should look good

 

[betterthanstock]

I wonder if 2400 rpm (assuming it's not noisy) would really cause any decrease in towing MPG. Are you happy with the initial acceleration? You can always get out of trouble with 4 LO.



Also, what % do you tow vs. empty?



May be best to drive it like it is until you have some mpg numbers. You would lose money on the tire trade anyway, so just drive it at 2400 w/ the slightest hill or headwind, and at 1600 with downhills and tailwinds. Your transmission will run cooler in direct, and less gear friction in direct by about 3%.



If you decide to use an aux trans, keep in mind that if you go overdrive with a 0. 78 in 3rd, it would give you . 78*2400 = 1872. Perfect. If you go underdrive, you get 1600/. 78=2142. That is a little high, and it's doubling the losses thru two sets of OD gears.

 

[wneubauer]

I wonder if 2400 rpm (assuming it's not noisy) would really cause any decrease in towing MPG. Are you happy with the initial acceleration? You can always get out of trouble with 4 LO.



Also, what % do you tow vs. empty?



May be best to drive it like it is until you have some mpg numbers. You would lose money on the tire trade anyway, so just drive it at 2400 w/ the slightest hill or headwind, and at 1600 with downhills and tailwinds. Your transmission will run cooler in direct, and less gear friction in direct by about 3%.



If you decide to use an aux trans, keep in mind that if you go overdrive with a 0. 78 in 3rd, it would give you . 78*2400 = 1872. Perfect. If you go underdrive, you get 1600/. 78=2142. That is a little high, and it's doubling the losses thru two sets of OD gears.

I tow a 8-9000 lb RV stock, and anything over 1900 rpm or so really hits my mileage...

 

[Matt42]

I drive/tow while watching the exhaust gas temperature (EGT) gauge I got from Geno's. Keeping the EGTs at or under 1,000F (when possible) really improves fuel economy. That's regardless--for me--of the RPM. And, quite literally, YMMV.

My signature file lists my 1996. This experience is with the 2004. 5 that I use on the job.