I'm going to be buying new tires I've had the stock size 245/65/17 now. I recently purchased a small travel trailer. Geo Pro G14FK. It weighs around 3000 lbs fully loaded. I've only towed it a couple of times for test runs. Envoy pulls it fine but I keep it in 3rd as has been recommended. It tachs out around 2500 rpm at 63-65 mph. Would it be worth adding a little width and height to the new tires? I don't want to modify or put in spacers. I've read that the 265/65/17 is about the largest tire I can run in stock configuration. Only 1/2 inch taller. Thanks for any input. Cam (c good)
A little taller tire for towing? 2002 Envoy. 3.42 ration
- Thread starter c good
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Taller tires would result in a higher final gear ratio... typically for towing it is recommended to have a lower final gear ratio to increase horsepower and torque.
Matt
Member
- Dec 2, 2011
- 4,022
I run the 265/65R17 and they'll lower your MPG even more and throw your speedo off by about 2 mph faster than indicated.
Lower my MPG? I'm thinking it might help with MPG...but lower my RPM. I'm just wondering if it will help me tow in 4th/O.D. ? Or just keep it in 3rd and lower RPM a little.
Chickenhawk
Member
- Dec 6, 2011
- 779
The secret to towing is to keep the RPMs up and just live with whatever gas mileage you get.
This is why we recommend towing in 3rd unless the trailer is way under 1000 pounds. Low RPMs kill motors and transmissions, and raises heat levels while towing. Going up slopes means keeping it in the 2500 RPM area, and that might mean even downshifting to 2 upon occasion. You're fine. Save your money, and tow in 3rd.
This is why we recommend towing in 3rd unless the trailer is way under 1000 pounds. Low RPMs kill motors and transmissions, and raises heat levels while towing. Going up slopes means keeping it in the 2500 RPM area, and that might mean even downshifting to 2 upon occasion. You're fine. Save your money, and tow in 3rd.
Thanks Chickenhawk for the excellent info. So probably best to just stay with the stock 245/65/17 tires then?
Matt
Member
- Dec 2, 2011
- 4,022
What did you do?
No, taller tire for towing is nonsense. You are talking about 1/2 taller which will hurt mpgs but not that much. 1-2 mpg at worst.
For towing you would want a smaller/shorter tire so your rpm is higher and you can use more of your high gears where the TC is locked.
Unless you like bigger tires then just stick with stock, this is what the engine computer unit is programmed to operate the vehicle at. Changing sizes changes rpms as they relate to actual speed and transmission output so the engine might not operate at its peak, the computer will not know that you changed anything.
No, taller tire for towing is nonsense. You are talking about 1/2 taller which will hurt mpgs but not that much. 1-2 mpg at worst.
For towing you would want a smaller/shorter tire so your rpm is higher and you can use more of your high gears where the TC is locked.
Unless you like bigger tires then just stick with stock, this is what the engine computer unit is programmed to operate the vehicle at. Changing sizes changes rpms as they relate to actual speed and transmission output so the engine might not operate at its peak, the computer will not know that you changed anything.
cornchip
Member
- Jan 6, 2013
- 637
Not nonsense at all. Your towing in third where you can't lock the converter.... where only the TCC valve control's the amount of slip in third until it maxes out at 100 percent duty cycle. I noticed many times on long uphill grades where the speed limit was 65+ MPH that I'd hit some sort of a timer where duty cycle was at 100% and code. A touch taller tire could lower that final axle ratio enough to avoid this....or we just lower the speed limit. What's the limit on a TB is the 3.42's. Changing tire diameter to the max of something like 30.4" isn't going to appreciably change final RPM. Should have had 3.07's if towing in third was the plan. Just my opinion.
Example 3.42 with stock tire....3rd is 2600 or more with TCC at 100%.
Example 3.07 with stock tire....3rd is 2334 or more with TCC at 100%. That's a way more comfortable RPM to be at. Most every Jeep 4.0L Cherokee I ever drove had this setup.
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Mine is a 4 speed and the rpm from 3rd to 4th is not an 800 drop. I do not know if 4th is an OD gear or not, it is not the vehicle I drive much.
I am lost on some of the info. What is the second C in TCC?
Can you explain the 3rd gear TC slip control? I understand when it is locked, but not a 3rd gear slip control...
I am lost on some of the info. What is the second C in TCC?
Can you explain the 3rd gear TC slip control? I understand when it is locked, but not a 3rd gear slip control...
cornchip
Member
- Jan 6, 2013
- 637
Correct me if I'm wrong, but I believe I'm talking about the big plastic TCC solenoid and not the TCC PWM valve. My understanding is the solenoid (also controlled by PWM) can control the slippage between the vanes in the converter (not lockup). Your 800 rpm is way high.....I felt it was as much as 300 or so in third. Maybe somebody can clear this up a little if I'm wrong.
800 rpm jump between the two high gears is going to not be a gear change but the TC unlocking and letting the TC slip that much. A gear change will only be 300 rpm between the high gears.
When you press the gas pedal at speed or up hill usually it is the TC unlocking and not a downshift when you see rpm jump; the trans will use TC to get higher rpm's before it will decide to make a downshift unless you just floor the gas pedal and then it might give you a downshift. A lot depends on speed and current load and other parameters, but in general this is what happens. The TC unlocking will usually be a huge jump like 800 or more and a shift will be different, bigger gaps in rpm for lower gears and the gaps become smaller as the gears get higher.
When you press the gas pedal at speed or up hill usually it is the TC unlocking and not a downshift when you see rpm jump; the trans will use TC to get higher rpm's before it will decide to make a downshift unless you just floor the gas pedal and then it might give you a downshift. A lot depends on speed and current load and other parameters, but in general this is what happens. The TC unlocking will usually be a huge jump like 800 or more and a shift will be different, bigger gaps in rpm for lower gears and the gaps become smaller as the gears get higher.