Tires

pnichols, I appreciate all of the feedback. I’m a fan of narrow tires, so no problem there! I’m, almost. ?? looking forward to buying 6 tires! Having the 450 chassis, with the low gearing, is definitely a plus! As said before, not looking for a “rockcrawler”, but 1 or 2 inches extra chassis height would be welcome! Thanks Again, Todd

Todd(?),

Your Bigfoot probably is built on the E450 chassis, so your great crawling differential ratio of 4:56 in 1st and 2nd gear will still provide plenty of slow speed pulling power even when using aggressively over-stock-diameter tires on it.

Just run larger diameter tires on it so as to get 1 to 2 inches of more ground clearance.

Try to keep larger diameter tires as narrow as possible so you can stay with the stock Ford 16 inch steel rims -> if and only also if 1) you can keep decent spacing between the tires in each rear dual set so the sidewalls don't ever rub at 80 lbs. pressure and, 2) you still have full front wheel suspension clearances so as to maintain the full turning radius and, 3) all wheel well clearances are adequate so as to not allow any tire rubbing from up/down axle motions on rough road surfaces.

BTW as I may have mentioned earlier, larger diameter tires wear longer too.

This is a post I made last April in a similar thread

https://www.rv.net/forum/index.cfm/fuseaction/thread/tid/29608055/gotomsg/29615202.cfm#29615202

Which is relevant to your situation.

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If your rear axle is at or over the max weight, consider using one of these tires,

There is a new tire out there (I'll refer to it as the Euro C). it is designed for cargo vans.

The Continental version is called the Vanco Four Season. The size carries the C after the designation. Much higher weight rating than a standard LT tire. There only a few manufacturers producing the tire.

Edit, added new link.

https://www.tirerack.com/tires/tires.jsp?message=singleSize&tireMake=Continental&tireModel=VancoFourSeason&width=225%2F&ratio=75&diameter=16&cameFrom=selectSize&partnum=275R6VANCO4

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Nexen Roanian CT8. Top four tire sizes in the chart at this link are the Euro C sizes (fourth down is your 225/75R16C)

https://www.nexentireusa.com/tires/suv-light-truck/roadian-ct8-hl

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OK, Michelin has apparently dropped the Agilis Alpin truck tires, so I edited and deleted this info.

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These three tires (in the 225/75R15C size) all have the 3195 lb rating at 83 psi (single) and 3085 lb (dual installation), and have a load index and speed rating of 121/120R which is suitable to your MH.

To compare, the standard LT225/5R16E tire you are probably using now, has a single wheel rating of 2680 lbs and a dual wheel rating of 2470 lbs (at 80 psi inflation)

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Not sold in the US market but available in Europe and Mexico is the Michelin Agilis Alpin Camper tire. Tread is designed for Motor Home use.

https://www.michelin.co.uk/tyres/michelin-agilis-camping#tab-tyres-benefits

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These Euro C tires are mandatory on the Ram Promaster as a standard LT doesn't have the weight rating necessary.

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Another alternative is to switch to a 17.5 inch rim and the much heavier tire that is used on it.

https://ricksontruckwheels.com/wheels-ford-e350450.php

Charles

pnichols, Yes, wheelbase is our biggest enemy, rear hangover, not so much! We went down a “very” tame two-track this past summer, it required some very careful navigation to prevent dragging. We came within less than an inch (much less) from an exhaust pipe contact. It will never be an off-road vehicle, but with our clearance....it’s barely a parking-lot speedbump vehicle. In it’s present configuration, it virtually eliminates our desired uses. While an inch or so isn’t much, it would certainly help. We really love the unit, it is certainly more at home in a paved parking lot, than a dirt/rock road! :M

memtb wrote:
pnichols, It would be a minor lift, no more than 4”! This thing, body, frame, steps,etc. are so low, you couldn’t pass over a small turtle without contact. Certainly understand the center of gravity elevation change, but for our uses and desires....this thing is near useless. We much prefer the roads “less” traveled by rv’ers. We will have to respect the higher potential “roll-over” risks involved! We’re not looking for a “rock crawler” just something we can travel on a mild “two-track” for some boondocking/ hunting/ fishing/ hiking, etc!

I assume that you're talking about your 2007 Bigfoot 30MH26Sl?

If so, then I'm guessing that the length of it - instead of it's traction - may be the biggest limitation to going on some two-track roads (in dry weather) to/from off-highway camping sites.

Our 24 foot Class C - with it's slightly larger diameter tires - now has about stock pickup truck road surface clearance, including all under-floor coach components. Also, it's relatively short wheel base length also helps to provide some high-centering protection.

I actually prefer it's rear duallies on rutted two-tracks because, if I take it easy, I can steer carefully so as to keep each rear tire up onto the upper sides of the ruts instead of having single rear tires that ride right down into the ruts. Driving this way with duallies decreases the chance of suspension and drive line components scraping the road surface between the ruts in the road.

However, driving off-highway with a Class C above all else requires driving very slow - unlike being able to blast along in a highly lifted 4X4 vehicle with it's long-throw shocks and suspension. That's especially a problem way out there when a "true off-road" vehicle comes up behind and wants to pass a Class C on a two-track with nothing but soft surfaces on each side of the road! :)

pnichols, It would be a minor lift, no more than 4”! This thing, body, frame, steps,etc. are so low, you couldn’t pass over a small turtle without contact. Certainly understand the center of gravity elevation change, but for our uses and desires....this thing is near useless. We much prefer the roads “less” traveled by rv’ers. We will have to respect the higher potential “roll-over” risks involved! We’re not looking for a “rock crawler” just something we can travel on a mild “two-track” for some boondocking/ hunting/ fishing/ hiking, etc!

memtb wrote:
I concur. We like narrow tires for a multitude of reasons, one being they seem to work better in snow.....which we see a bit. I was just using the assumption that we would see a greater mph change, and the correction would be wise. When we got our rig, it had already been computer chipped....and while I haven’t actually checked, I figured that the tire size was reprogramable. If not needed.....all the better! The only bad thing, of course “not” spending money is not really a bad thing”.....it had brand new tires when we bought it last August. It will be a while before we get the much needed ground clearance with taller tires. When we win the lottery :B.....it will get a 4x4 conversion, which will cure most any clearance issues, as well as low range for those steep grades and boat removal from slick ramps!

Is your current rig a Class C?

Our 24 foot E450 Class C can still crawl along great with it's 4:56 rear differential, even though I've countered that slightly with the taller tires.

The one thing I don't like about 4X4 conversions is the lifting of the whole rig, thus doing something you don't want - creating a higher overall center of gravity. You want everything as low as possible in a 4X4 for off-highway use - EXCEPT the undercarriage and suspension/drive components. Increasing tire diameters thus does just what you want - raising undercarriage and suspension/drive components for rough roads while at the same time not raising the overall center of gravity any more than absolutely necessary.

We take our Class C into the Oregon and Utah back country with, so far, no problems - but we we do have to travel slow when off-highway with it.

I concur. We like narrow tires for a multitude of reasons, one being they seem to work better in snow.....which we see a bit. I was just using the assumption that we would see a greater mph change, and the correction would be wise. When we got our rig, it had already been computer chipped....and while I haven’t actually checked, I figured that the tire size was reprogramable. If not needed.....all the better! The only bad thing, of course “not” spending money is not really a bad thing”.....it had brand new tires when we bought it last August. It will be a while before we get the much needed ground clearance with taller tires. When we win the lottery :B.....it will get a 4x4 conversion, which will cure most any clearance issues, as well as low range for those steep grades and boat removal from slick ramps!

memtb wrote:
pniichols, I can see nothing wrong with your logic. When I originally got involved on this posting, I thought I was on the 5th wheel site( senility has it’s downfalls)....we have both a class c and a 5 th wheel. When I mentioned the 19.5’s, I was referring to the truck, thinking I was on 5th wheel site! . We haul very heavy loads with a SWD truck, another topic for another day. The 19.5’s allowed us to have “much” greater rear load rating.

When we put “new shoes” on our class c, we will do the same as you. A much taller, 16” tire, and recalibrate the speedometer. We’re running 4.30 gearing, taller tires will be a huge plus in many ways!

I'm curious ... how do you recalibrate the speedometer without spending money for a repair shop to do it via the OBD2 connection?

Our speedometer only reads about 1 MPH slower, so I have just left it as is.

By the way, of course when you go up in tire diameter on the 16 inch rims you usually wind up with tires that have higher per tire weight rating. Hence you get maybe a quadruple bonus using your stock 16 inch rims with taller tires: 1) More ground clearance, 2) a better ride, 3) slightly better gas mileage from making the overall drive ratio a bit taller, and 4) increased tire life due to less tire tread revolutions per mile.

My Ford E450 Class C came with the usual stock 225/75R16 LR E tires. I now run 215/85R16 LR E tires on it. I use the same tire pressures, use the stock 16 inch rims, get the same per tire load ratings, and gain about a 1.2 inch larger tire diameter for an increased 0.6 inches of ground clearance.

Another very subtle bonus is that the 215 tires are just a bit narrower - for better cooling air flow in between the sidewalls on rear dually sets during hot weather and for slightly more pounds per square inch downward pressure on all six tires that improves traction and steering via being able to better push through the slick layer to rougher material on wet or snowy road surfaces.

Larger diameter tires are always a better way to go. Even towables should, IMHO, come stock with larger diameter tires than what is commonly found on them.

pniichols, I can see nothing wrong with your logic. When I originally got involved on this posting, I thought I was on the 5th wheel site( senility has it’s downfalls)....we have both a class c and a 5 th wheel. When I mentioned the 19.5’s, I was referring to the truck, thinking I was on 5th wheel site! . We haul very heavy loads with a SWD truck, another topic for another day. The 19.5’s allowed us to have “much” greater rear load rating.

When we put “new shoes” on our class c, we will do the same as you. A much taller, 16” tire, and recalibrate the speedometer. We’re running 4.30 gearing, taller tires will be a huge plus in many ways!