Moving up trailer wheel size?

[jdavis92]

I have a 2007 Jayco Jayfeather Sport 165

Wheel/tire size is 175/80 R13.

I was thinking of going up to 205/75 R14.

There seems to be enough room in the wells. I'm just wondering if going up in size will allow me to tow faster, or if there is something else I should be considering.

Thanks.

[muelldawg]

I have wanted to do this also; but am not yet comfortable with wheel clearance issue. Every time I put on our "sun screen" cloth wheel covers I am reminded of how little space there is.

Has anyone with a Sport165 gone to the 14 inch wheel and found that it works?

I had not thought of the increase in speed you may be able to safely do. The issue for me is max load increase. And the axle may be more important than tire size for max load.

[3'senough]

Originally Posted by jdavis92

I have a 2007 Jayco Jayfeather Sport 165

Wheel/tire size is 175/80 R13.

I was thinking of going up to 205/75 R14.

There seems to be enough room in the wells. I'm just wondering if going up in size will allow me to tow faster, or if there is something else I should be considering.

Thanks.

You will not be able to increase your speed. ST tires are rated up to 65MPH regardless of size. You will only reduce your total turns per mile since you will have added circumference.

If however you go to LT with increased load capacity your tire speed ratings do increase based on manufacturer specs. First you need to check your rim ratings and if the added pressure can be taken if you go up in load range to meet your weight requirements. LT's are rated for less weight than ST's in similar load ranges due to the softer sidewalls which is why you need to go up in rating. They also are not built to take the twisting that takes place in double axle configs which is not an issue in your case being a single axle.

[clubhouse]

Towing at high speeds simply isn't a good idea.

As 3'senough pointed out, ST tires are 65MPH rated regardless of size.

As for LT tires, sure you can get higher speed ratings than ST...however I am not to sure if LT tires are made for 13" wheels, possible you could get one for 14" wheel but even that I doubt there would many options if any.

In CA the speedlimit while towing is 55mph, so the ST speed rating isn't an issue for me. I typcially find myself on the interstate running at 60-62, generally the same speed as the truckers.

[jdavis92]

Yeah just did California from Needles to Guerneville and back.

I too stayed between 60 and 65 most of the way despite the 55 thing. Odd that most other western states don't have that restriction.

Here's my thought. At 60-65, my truck runs right at 2700RPM and I get 10MPG. If I could run at a slightly higher speed, say 65-70, and 3000RPM, I think I might get slightly better MPG and get to my destinations a little faster.

Edit: the other thing I am trying to "fix" is that my Sport 165 rides so low that the E2 WDH shank is not low enough to totally level out my rig. It's really darn close (probably close enough) but it would be nice to have everything REALLY level.....I'm weird like that.

Jeff in Flagstaff

[clubhouse]

Needles to Guerneville is quite a tow. I'd say that 1300 mile round-trip tow though all types of terrain and traffic would tell you for certain if the WD hitch needs adjustments.

You are trying to accomplish a lot, here is what I would consider....

1) Only way to get speed rating you want it leave ST tires, focus on LT tires.
2) LT tires may be available in 14" but likely you will need 15" or larger -- will 15" fit?
3) Your orginal plan 175/80R13 to 205/75R14 is a overall 2" diameter increase, or 1" in actual height. Is 1" enough? If not, and you can fit 15" wheel/tire, that will get you closer to 1.75" in actual height increase.
4) Can you can flip the axle and stick with smaller wheels.

Beyond that I don't have any thoughts.

IMO, if the TT hieght is good, just not perfect I wouldn't go through changing wheels and tires just for additional height. Secondly, how much better is you MPG going to be, is it really enough to off set the cost you are considering? And don't forget the possible CHP ticket for running at 65-70

[jdavis92]

Thanks clubhouse.

Yeah after 1700 miles I really don't think the WDH needs adjustment......maybe a little, but again I'm weird like that. Plus, I'm not an experienced tower. It could be that it does need adjustment and I just don't know it. It didn't feel as it we were bobbing all over the place and we encountered some fierce crosswinds that didn't put the TT all over the road either. Chances are, things are good.

Answers (or more questions):
1) I wonder if LT rated tires would "support" my trailer. It has a 3500 GVWR. I guess I would have to look into it.
2) 14" would fit, not sure about 15" unless I got lower profile tires. Although a wider 15" might not fit either.
3) 1" more effective diameter would probably level things out. I mean it really is close. I should have taken a photo of the entire rig while it was all hooked up.
4) I don't think flipping the axle on a Sport 165 is even possible. It's a Tor-Flex axle.

As far as increasing MPGs being "worth" it. I got 10MPG on my trip. $700 in gas. If I got 12MPG instead, gas would have been roughly $580. The new wheelset would be paid off around 4500 towing miles with that math. I think it's worth it.

Then again, maybe I'm just being picky.

[clubhouse]

Best of luck, and yes LT = Light Truck, OEM on all 3/4 and 1 ton trucks. They will handle 3500 lbs TT GWR.

[Doug]

Hi Jeff,
I never did try a 14" wheel on my trailer.
Height didn't seem to be a big deal. I had to slinky the hose a few times but no issues with driveways etc.
I thought I seen a post by our resident rig hauler and he reported getting the best MPG at 55?
Keep us posted if you get 14's fitted.

Kind regards,
Doug

[Paulx213]

Originally Posted by jdavis92

Yeah just did California from Needles to Guerneville and back.

I too stayed between 60 and 65 most of the way despite the 55 thing. Odd that most other western states don't have that restriction.

Here's my thought. At 60-65, my truck runs right at 2700RPM and I get 10MPG. If I could run at a slightly higher speed, say 65-70, and 3000RPM, I think I might get slightly better MPG and get to my destinations a little faster.

Edit: the other thing I am trying to "fix" is that my Sport 165 rides so low that the E2 WDH shank is not low enough to totally level out my rig. It's really darn close (probably close enough) but it would be nice to have everything REALLY level.....I'm weird like that.

Jeff in Flagstaff

I'm not following why you think you would get better mileage. Drag increases exponentially with speed and my experience has been anything over 60 mph causes mileage to drop fast.

[steveb285rks]

jdavis,
As mentioned by paulx, you may be in for a rude awakening when you check your mileage running faster. The extra drag from wind resistance and the additional rpms equate to more fuel used. Getting there faster comes at a cost. My rig does 12.8 towing and 17 average (mostly in town) not towing. But it is a diesel. My old gas truck towing a 22' 5er was lucky to get 9 mpg towing over the same terrain. It is all up to you but for the reason of running faster to expect better mileage then it is a bad choice. I did LT tires on the old Dutchmen to get a bit more height and it worked out great. Plus I went with nice chrome wheels that really dressed up the old girl.

[LiftedAWDAstro]

Going up in speed will NOT increase your mileage. My setup got 10.03 mpg towing mostly at 60 - 62 mph with a short jaunt at 70 on interstate. The same trip home, we were pressed for time and I ran 50% - 60% interstate at 70 and we got 9.2 with less weight as we burned through a weeks worth of wood plus we dropped in elevation coming home from the Adirondacks.

[29BHS ECO]

The faster your speedo goes the faster your gas gauge goes down

[jdavis92]

What some of you may be forgetting is that going just a tad faster (say 70 instead of 65) and thus putting my RPMs 300-400 higher puts the engine in a better spot along the power band. More torque, more HP. Increased RPM does not necessarily equate to more fuel used.

Larger tires would roll better thus decreasing rolling resistance and increasing the moment of inertia when up to full speed (of course it would take more energy to GET them up to full speed).

Larger tires would also decrease the number of revolutions on the axle, thus decreasing the amount of wear.

And, my whole rig would ride a little more level.

Ultimately the question is, would all the positives outweigh the one big negative of increased wind resistance on the TT at a slightly faster speed?

I don't know. I may not even try and find out. If I do try this, it won't be until next season before our first big trip. I'll need to take the TT to the same place a couple times to do some control runs before (if) I go up in tire size, and then do those runs again to see what happens.

[tinlizzie23]

I would NEVER run a trailer at 70 MPH. You can get in a lot of trouble very quickly should something happen, either to a vehicle in front of you, or to your rig. Braking power does not increase with increased speed, and controlling a blowout at 70 is much more difficult and dangerous than the same blowout at 55 or 60. To me, the risk to me and my family just isn't worth getting there 15 minutes sooner. JMHO

[steveb285rks]

Your theory might work with an aerodynamic, unladen vehicle in ideal conditions but considering the fact that wind resistance increases exonentially with an increase in speed, your theory will not work. Period. Safety concerns aside, you can't get better milege going faster.

Originally Posted by jdavis92

What some of you may be forgetting is that going just a tad faster (say 70 instead of 65) and thus putting my RPMs 300-400 higher puts the engine in a better spot along the power band. More torque, more HP. Increased RPM does not necessarily equate to more fuel used.

Larger tires would roll better thus decreasing rolling resistance and increasing the moment of inertia when up to full speed (of course it would take more energy to GET them up to full speed).

Larger tires would also decrease the number of revolutions on the axle, thus decreasing the amount of wear.

And, my whole rig would ride a little more level.

Ultimately the question is, would all the positives outweigh the one big negative of increased wind resistance on the TT at a slightly faster speed?

I don't know. I may not even try and find out. If I do try this, it won't be until next season before our first big trip. I'll need to take the TT to the same place a couple times to do some control runs before (if) I go up in tire size, and then do those runs again to see what happens.

[29BHS ECO]

jdavis92--After you increase you tire size don't forget to have you TV's computer reprogramed to suit the tire dia. increase. Larry

[jdavis92]

I'm not sure I follow?

Why would I need to reprogram anything on my TV if I move the TT tires up in size?

[steveb285rks]

Jeff,
After further consideration of your statement in post #6 what you need to do is increase engine speed into the "sweet spot" without increasing vehicle speed (and resultant drag). Your truck would need to be refitted with different gear ratio (or smaller diameter tires, not practical) in order to get the engine to turn 3 grand at 60-65 MPH. It may be an expensive proposition and not worth the payback but that is really what you are trying to accomplish by raising the speed of the engine. I went from 3.55 gears on my 96 Ram 1500 to 4.11 gears. It towed better but the gas mileage was not that great either way. Being a 4x4 I had to do 2 sets which cost $1300 in 2002. That's about 325 gallons of gas.