saflyer

Same tire size.

I fully understand the concept of calculating mileage. But two points. One, it was my first opportunity to update. Two, as I said it’s not likely I made a difference in filling of anywhere near 5 gallons but factoring that my mileage is still horrible.

Re: previous post about lowered mileage with new tires. Just did a fill up with the new Sumitomo ST719s. The last one had 124 miles on the old tires so this one is more representative. My last fillip on the Michelins gave 7.6 mpg. The last six fillups gave an average of 6.8 mpg. This fill up was after driving 309.8 miles mostly at 65 mph. Fuel used was 69.651 so about 4.5 mpg! Ouch! My mileage dropped by fully 1/3! I filled at the same station and pump so the coach level the same on both fills. I did squeeze more fuel in the second time so that dropped my mileage. But even applying a huge fudge factor of 5 gallons the mileage is still less than 4.8 mpg. Next week I’ll take the motorhome to a shop to find out if there could be any drive train problem causing the change. Ed ‘05 HR Ambassador

Interesting side note about lower inflation. When I purchased this coach 12 years ago Ibelieve it had Michelins but not absolutely sure. Driving it home from Michigan I thought I had made a big mistake. It drove terribly. Wandered all over the road. I was constant turning the wheel left and right wearing myself out. I was driving 60-65 and when trucks passed it scared the begeebers out of me. Got it home and had the alignment checked. It was good. Then I looked up the inflation tables. The dealer had the tires at something over 120 psi, exactly how much I don’t recall. The inflation tables were more like 95 rear and 100 or so steer. I was leary of lowering the pressure as I thought that could only worsen the drifting problem since the sidewalls would be less stiff. To my surprise that wasn’t the case. The new pressures improved the driving of the coach immensely. Still didn’t drive like a car but far better than before. I realize some of the improvement may have been muscle memory but I’m sure the inflation was a big part. To get better steering I switched from the Shephard steering box to a TRW one but didn’t notice any improvement with that.

I sent a request for info to Sumitomo via their website. Evidently they forwarded it to a U.S. distributor, TBC Corp. who responded as follows: Mr. Fogle, We are in receipt of your inquiry. We are a wholesale tire distributor of multiple brands of tires, not a tire manufacturer, and we create dedicated websites for each of the brands of tires we distribute; we distribute the Sumitomo brand of tires in North America. Most tire manufacturers only provide us with the maximum psi and maximum load a particular tire can hold, as they cannot foresee where the tire will be installed on; however, Sumitomo has provided a load inflation table which you can find by clicking on the link below: https://tbc.scene7.com/is/content/TBCCorporation/TBC%20Brands/Commercial/Sumitomo%20MRT/Catalog/2022/Medium-Truck-Technical-Data_0322.pdf This information can be found if you return to the website, go to the DEALER RESOURCES section, and under the 2023 MEDIUM TRUCK TIRES catalog, clicking on the third link that reads Medium Truck Technical Data; the information you are looking for is on page 4 of this document. Thank you, Olga Fraga Consumer Relations Tel. (800) 238-6469 Fax. (800) 467-4638 Email: ofraga@tbccorp.com

I’m not relying on the dash gauge. It’s just a heads up, first estimate. This is where I was led to the ST719: http://www.sumitomotrucktires.com/tires/find It says “steer tire” but the diagrams show them in all positions. The ST709 is stated as an “all position” tire. BTW they web page says ST 719 SE. I don’t know what difference the SE makes.

Tom, I had my coach weighed at the four points years ago but can’t find that anymore but as I recall the difference left to right wasn’t enough to make a difference in pressure. And yes, we weighed at travel weight. All of our gear, passengers, supplies, full fuel and 20 gallons of potable water. On a Cat scale it’s 10,000# front, 20,000# rear. Your table is different from the one Sumitomo gave me. The table I have has no pressures below 95 psi. At that the single weight is 5400# whereas mine imply 5000#. So steer and drive pressures would be 95 psi per my table. And, yes I checked the pressure in the shade at 75°. So, my 105 should be more correct than 115, or am I confused. BTW, the tire guru who writes for one of the RV travel email newsletters advises to add either 10psi or 10%, I don’t recall which, to the tables to allow for lower temperatures. He also does not adjust for temperatures different from 75° but I believe you should. Would it be possible to have a fuel leak while driving but not while stopped and idling? Thanks, Ed

Before my first post of this thread I fueled up at 390 miles with 72.25 gallons. This gives 5.4 mpg. But I had 124 miles of that tank on the old tires. Applying a conservative adjustment for that returns about 5 mpg. I’m fully aware of the inaccuracy of the dash gauge and a drivers inability to read it to a fine point but even allowing for 20% error gives 4 mpg. My gauge has been accurate enough over the years to have cause for concern of my current mileage. I plan to fuel up Friday at the same station which will take any difference in coach tilt out of consideration. As most know any tilt of the motorhome can make a significant difference in the amount of fuel you can squeeze in the tank. But I don’t think there is any way I’ll get near the 500 miles you suggest.

If the halfway mark on my fuel gauge is 50 gallons the mileage indicated is 3.2 (160/50). If it’s only indicating 40 gallons used that’s still no better than 4 mpg. The gauge has always been accurate. We’ll see at the next fill-up. I hope you’re right.

Fairly inaccurate but when gauge was on half mark, about 50 gallons used I had only gone 150 miles since fill-up.

Just installed a new set of Sumitomo ST719s on my coach in place of my Michelins.I haven’t done a rigorous check yet but they appear to be delivering about half the fuel mileage as the old tires. Maybe 3-3.5 mpg vs. my former 6.5-7, which was nothing to write home about. I can almost see the fuel gauge move as I drive. It’s so bad I checked for a fuel leak. Is this possible? The installers put 115 psi in all tires. I gat the Sumitomo numbers and the table ssid 95 psi so I lowered all 6 to 105 psi for this trip. Will update st my next fill up. Ed ‘05 HR Ambassador

One person said it’s best to buy Centramatics where they have all models in stock and do a lot of motorhomes so they can select the best ones. I don’t have that luxury but the tire shop that is installing my tires installs a lot of Centramatics on semis so I figured he could tell if they sent the right one from the local Centramatics dealer. So far so good.

Interesting. Just today someone posted on ramblinpushers.com the same thing. Seems like “belt and suspendes” idea but makes sense.

There are several different models based on wheel type. Hope they have good customer support for helping me order the right ones.

OK, I need to know more about Balance Masters. What’s the difference between them and Centramatic?

Anyone use Centramatics for balancing your steer wheels? I’m getting new tires all around and a friend advised me to go with them versus beads or spin balancing. Ed ‘05 HR Ambassador

What are others thoughts on the Centramatics? One friend was of the opinion bead balancing for motorhomes is not ideal since they sit so much of the time and the beads will migrate while sitting.

Well, since Toyo doesn’t make the 275/70R 22.5 anymore I checked locally and could only find Hercules and Sumitomo in my load and speed range. Current Michelins show 148/145M for these ranges. The Hercules and Sumitomo run close to each other in price, low $3000 range out the door. Any suggestions? Also, bead or spin balancing? If I go with online tires where they come to me to install I guess it will only be the bead option.

I need six new tires for my HR Ambassador, 275/70R 22.5. Running Michelins now but they’re too expensive this time around. A friend put Toyos on a few years ago for a good price.He’s happy with them. Another thread poster put Hercules on but had a harsher ride than his old ones. Nothing was said about other brands like Goodyear, Goodrich, Firestone, etc. Any sugestiona. Also, things like M144 and 11A were mentioned. Are these models or specs?

Thanks

I have no idea what lube they were originally filled with. When I need to add lube can I mix the synthetic with whatever is in it now or should I drain and start over.

Found it: Knight. Is that correct? Ed

Looked for a wiring diagram for my ‘05 HR Ambassador. The ones in files are for Monacos so I need to know the Monaco equivalent of the Ambassador. Thanks

On the advice of some on one of the forums i use I changed my front wheel hub grease fittings to the type in the picture. I don’t know what they are called so if anyone can help me with that please do. I was given the briefest insulation on checking and replenishing the fluid and have now forgotten what little I knew. Can anyone tell me how to check the level and fill if necessary and with what type of lubricant? Ed ‘05 HR Ambassador

Found out what the lower lights are. Fog lights with a separate switch. They work.