Super singles for motorhomes?

[Chance]

Lately I've noticed more and more large trucks on highway have converted to super-single tires.

Any thoughts on this trend spreading to motorhomes?

[JamieGeek]

Since we have to call road service anyway when there is a blowout I don't really see a down-side (and as mentioned in the thread below) the frame can be wider. For an RV that means more room for stuff in the RV.

Wide Base Tires (Super Singles) | TruckersReport.com Trucking Forum | #1 CDL Truck Driver Message Board

[Chance]

Jamie, thanks for link -- lots of good opinions.

Initial cost seems to be the main objection; but that applies to conversions from duals. If the chassis started out with singles from OEM I'm not sure if it would add cost at all. It seems to me like they might be cheaper than duals.

I'm not a big fan of duals, and also prefer the way super singles look -- particularly on alloy rims. My main concern would be in case of rear-tire blow out.

I'm curious -- if they made a super single in size for Axis/Vegas rear, would you consider the change? Maybe when tires need replacement?

[KCook]

I work for a towing company and I was told they use a different axle that dually’s.

KC

[EA37TS]

One of the things to look at when considering this is the tire and wheel size. Great strides have been made in super single weight ratings at the 22.5 inch size (Challenger, Miramar and diesel pushers) but what have they done at the 19 inch (Hurricane, Windsport) and 16 inch (E350) sizes.

I was reading where to handle the weight of a coach with slides you would need a 20 or higher ply tire (to get the correct weight rating) and a tire that hard would result in an uncomfortable ride on a coach without air suspension. I believe that is one reason it took so long to get super singles on the high end bus conversions (Prevost etc...). It seems some of those manufacturers are starting to make the switch now.

As to upgrading a current coach, estimates I've seen from a couple years back have the cost at between 3200 and 4000 for a coach with 22.5 inch tires. The question that one must ask is do the miles driven annually justify such an expense. In general (not always the case) motorhome tires will be replaced due to age rather than mileage.

One additional point I read was along with super singles is the addition of a wider tracking front tire to complete the package. As low as the Challenger body sits over the front tires while travelling I'm not sure I could put a wider tire up front.

[Chance]

Dave, in 16-inch rim size the only tires I'm familiar with are the size that have been used for years on Mercedes Sprinters with Super Single option. And while they can meet the load rating for the 11,500-pound E-350 they don't quite meet the 12,500-pound GVWR chassis as far as I can tell.

I've seen specs for luxury motorhomes with front axles up to 20,000 pounds, but that's very unusual. Most semi trucks I've noticed on roads using Super Singles on drive wheels and or trailers use standard front steer tires. And having different size wheels and tires on a motorhome would be less than ideal in my opinion.

For most motorhomes under 24,000 pounds or so I'm not even sure why front-engine chassis are built with duallies in the first place (other than saving a few dollars).

Why not have front and rear axles of similar capacity and design coach with near 50-50 weight distribution? It's worked for cars, vans, and smaller motorhomes for decades, so why not on bigger units?

Duallies make/made a lot of sense in the past for trucks (on which many Motorhomes are based), but with advances in engineering their need seems outdated to me.

I would like to see larger modern-versions of classic motorhomes that were built with four equal-size standard tires, like the old Revcon, Cortez, etc...

[KCook]

Originally Posted by dstankov

One of the things to look at when considering this is the tire and wheel size. Great strides have been made in super single weight ratings at the 22.5 inch size (Challenger, Miramar and diesel pushers) but what have they done at the 19 inch (Hurricane, Windsport) and 16 inch (E350) sizes.

I was reading where to handle the weight of a coach with slides you would need a 20 or higher ply tire (to get the correct weight rating) and a tire that hard would result in an uncomfortable ride on a coach without air suspension. I believe that is one reason it took so long to get super singles on the high end bus conversions (Prevost etc...). It seems some of those manufacturers are starting to make the switch now.

As to upgrading a current coach, estimates I've seen from a couple years back have the cost at between 3200 and 4000 for a coach with 22.5 inch tires. The question that one must ask is do the miles driven annually justify such an expense. In general (not always the case) motorhome tires will be replaced due to age rather than mileage.

One additional point I read was along with super singles is the addition of a wider tracking front tire to complete the package. As low as the Challenger body sits over the front tires while travelling I'm not sure I could put a wider tire up front.

Chance is correct Super Single are only for no Steering axles. Trucks with wider or flotation tires the front fender are set up for turning.

KC

[EA37TS]

No arguments and only going with what I've read about the issue. One point that was constant and one with which I must agree based on years of experience with large tactical vehicles, is that if there is a failure with one tire in a dually setup the other tire can support the weight for a small distance. That is not the case with a super single.

Now if you want to talk about a tire upgrade, one that I believe would be better money spent, is a run flat for the steering axle tires. Keep the duals and add run flats to the steering axle and we may stop seeing coaches on their sides because of a blow out.

I know Rodgard makes run flat inserts for wheels up to 22.5 inches but they are primarily for emergency and military vehicles and may be priced outside the budget of RV owners. Also, I'm not sure if they make them wide enough to go inside a super single. I may give them a car in the near future. If not outrageously priced this might be a good winter project.

[Chance]

Originally Posted by dstankov

....cut...

Now if you want to talk about a tire upgrade, one that I believe would be better money spent, is a run flat for the steering axle tires. Keep the duals and add run flats to the steering axle and we may stop seeing coaches on their sides because of a blow out.

....cut.....

I would think that the industry-wide trend to make motorhomes taller and taller with higher center of gravity isn't helping much as far as roll overs go.

I find it interesting that many classic motorhome designs (GMC, Cortez, Revcon, Vixen, Aero Cruiser, etc...) were built fairly low on custom-designed chassis optimized for RV use.

Newer motorhomes over 12-feet tall worry me. I like the Axis/Vegas for being lower to ground, although I would prefer a motorhome that was lower still.

[Chance]

Originally Posted by dstankov

One of the things to look at when considering this is the tire and wheel size. Great strides have been made in super single weight ratings at the 22.5 inch size (Challenger, Miramar and diesel pushers) but what have they done at the 19 inch (Hurricane, Windsport) and 16 inch (E350) sizes.

....cut....

Dave, this data from Michelin answers some of your questions regarding 22.5- and 19.5-inch available Super Single tire sizes. The larger sizes seem like overkill for most motorhomes, with ratings in the 20,000-pound-per-axle range.

In smaller 16-inch size this Michelin table doesn't show any Super Single or Wide Base tires, but other manufacturers may have offerings. Like I mentioned before, Mercedes offers what they call Super Single option on Sprinter vans. I'm not sure but may be made by Continental.

Load & Inflation Tables | Michelin Truck

After reviewing Michelin tire load data and specs for Ford F53 chassis, it seems to me that tires are not the limiting factor to having a motorhome with four equal-size tires if the OEM wanted to build one. Dual rear tires make sense to me for many trucks because their empty versus loaded weight can vary so much (can double the weight), but that's not the case at all for motorhomes.