Changing Tire Size

[eoddewey]

Has anyone went from a 305/70/22.5 tire size to a 295/88/22.5?
I want to install new tires on my 2006 Dutch Star 4320 and the only other 305 tire is a Continental.
Anyone using these Continental tire?

[Ronnie Bledsoe 2006 Dutchstar 43']

Why do you want to change and move away from Michelins? I have had real good service from mine. I had them inspected at a local Michelin dealer last month and he said there is no evidence of sidewall problems and tread is about 60% after 57K miles. I will keep a good eye on them.

[Harm]

I just replaced my 305's with all new Michelin 295/80's. They are a little taller but I have no clearance problems. I had ripped a flap out of my RR sidewall and just decided to replace them all with the larger tire. The 305's are in very limited supply and many people have stated they have waited weeks for a new tire after a blow-out. The 295's are available anywhere. If you make the switch remember to have them reprogram the speedometer for the larger diameter of the 295's.

[wardy]

I looking to up-size so I'm hoping for advise. I have the Spartan MM with IFS mfg'd in 2006. I have 275/80/22.5's (tires are 6 years old) and I've weighed the coach, I only have 160 pounds before I exceed the front tire's max load. I want to up-size for some weight margin to the 295/80's or maybe the 305/70. I'm hoping someone can tell me what to expect pro or con. Sorry to be a little off subject...

[rvjimmy]

Our one set of new trucks at work came with 295/80's on them we took most of them off with 140,000 miles on them no problems. There are a lot of good tires out there without the michilen price tag though. JMHO Jim

[Mr_D]

Originally Posted by wardy

I looking to up-size so I'm hoping for advise. I have the Spartan MM with IFS mfg'd in 2006. I have 275/80/22.5's (tires are 6 years old) and I've weighed the coach, I only have 160 pounds before I exceed the front tire's max load. I want to up-size for some weight margin to the 295/80's or maybe the 305/70. I'm hoping someone can tell me what to expect pro or con. Sorry to be a little off subject...

But if you upsize the tires to support more weight will the axle rating be enough? If the tires are matched to the axle rating then just changing tires won't gain anything. the ratings are taken from the lowest rated component which could be the tires, axle, brakes or even the wheels.
Our 2002 DSDP came with 275/70's and it was overweight on the front axle if I filled the fuel and propane tanks. The only solution was to have a new axle installed. Since it was overweight as it left the factory that meant that it was unsafe to have on the road and legally couldn't be sold. Newmar had Spartan replace the axle (12,000#) with a 14,600# unit. But they left the old tires on which limited us to 13,200#'s. I replaced the standard front tires with 305/70's so now can use the full axle capacity.
I tried to find out about the 305/70 Continental tires but they weren't in production yet. Might be now though as it was a couple years ago this month.

[wardy]

MR_D: Thanks for the reply. I also have the 14,600lbs axle as you now do. But here's the thing, I am not wanting to add more weight but I'm looking for a safety margin. My current tires are rated at 7160 each or 14320 total at maximum inflation of 120 pounds. My coach has 14160 pounds on the front end now with full tanks, wife (114 & me 175 pounds) and self. In other words there is so little margin left over and that's only if we are at the max tire inflation. Even hitting 115 PSI put's us in an over-load. In other words no extra margin of safety. Unfortunately my rims are 7.5 inches which further limits our choices. I've emailed Michelin Tuesday asking for advise using their technical address but I've not heard back. I know there are engineering safety margins in all ratings so maybe I should just relax. It's just that with tires it goes against my thinking.

[footdoc]

I just went through the same dilemma....If I changed to the 295 tires, I'd give up ALOT of carrying capacity....the 305s are load range L and are rated about 7700 lbs as a single tire....I like having about 2 TONS of carrying capacity...it's a great safety margin without having to fill them to 115 lbs...I didn't have a speck of trouble finding 8 of them in June...

[Mr_D]

Originally Posted by wardy

MR_D: Thanks for the reply. I also have the 14,600lbs axle as you now do. But here's the thing, I am not wanting to add more weight but I'm looking for a safety margin. My current tires are rated at 7160 each or 14320 total at maximum inflation of 120 pounds. My coach has 14160 pounds on the front end now with full tanks, wife (114 & me 175 pounds) and self. In other words there is so little margin left over and that's only if we are at the max tire inflation. Even hitting 115 PSI put's us in an over-load. In other words no extra margin of safety. Unfortunately my rims are 7.5 inches which further limits our choices. I've emailed Michelin Tuesday asking for advise using their technical address but I've not heard back. I know there are engineering safety margins in all ratings so maybe I should just relax. It's just that with tires it goes against my thinking.

When I changed from the 275/70's on OEM steel wheels I went to Alcoa 8½" wide rims and 8½" wide steel wheels on the inside duals. They're a little wide for the 275's on the rear though.

[wardy]

Originally Posted by Mr_D

When I changed from the 275/70's on OEM steel wheels I went to Alcoa 8½" wide rims and 8½" wide steel wheels on the inside duals. They're a little wide for the 275's on the rear though.

If you stayed with 275's in the rear why did you change the rear rims? You now have me thinking though. The 305 is only 1/2 inch shorter than the 275/80. So I could replace the front Alcoa's with 8.25's (seem to be in the high $300's) and keep the 275 size in the rear. I may need to tweak the tag or front air bag ride height slightly though.

footdoc: Did you install the conti hsr1? About what price per tire?

[KSCRUDE]

If you change tire diameter from front to rear you may fool the abs system into doing very strange things. Probably not safe to drive unless all tires are same height!

[Mr_D]

Originally Posted by wardy

If you stayed with 275's in the rear why did you change the rear rims? You now have me thinking though. The 305 is only 1/2 inch shorter than the 275/80. So I could replace the front Alcoa's with 8.25's (seem to be in the high $300's) and keep the 275 size in the rear. I may need to tweak the tag or front air bag ride height slightly though.

footdoc: Did you install the conti hsr1? About what price per tire?

Had steel rims all around, wanted to go to the Alcoa's but couldn't get them in the narrower width at a reasonable price. Would have had to buy them new rather than used from a truck wrecking yard.

[Mr_D]

Originally Posted by KSCRUDE

If you change tire diameter from front to rear you may fool the abs system into doing very strange things. Probably not safe to drive unless all tires are same height!

275/70's and 305/70's are only about 1.1" difference in diam. or .55" radius. Didn't change a thing as for as the ABS is concerned. Difference in revs per mile is 545-531 or 14 revolutions per mile.

[Mr_D]

Originally Posted by wardy

If you stayed with 275's in the rear why did you change the rear rims? You now have me thinking though. The 305 is only 1/2 inch shorter than the 275/80. So I could replace the front Alcoa's with 8.25's (seem to be in the high $300's) and keep the 275 size in the rear. I may need to tweak the tag or front air bag ride height slightly though.

footdoc: Did you install the conti hsr1? About what price per tire?

Ride height is set by measuring between suspension points and has nothing to do with measuring the house to ground clearance. Changing tire size will not change the ride height although you might need an alignment due to the change in offset