hrgottman@hotmail.com Report post Posted March 30, 2014 New tires for 04 DS DP Spartan chassis 370 hp.original tire Michelin XZA1 275/70R22.5 LRH. The dealer says theXZA2 275/70R22.5 LRJ is the tire i need. OK, but what about the XRV305/70R22.5 LRL? The XRV would require less PSI for comp loads is this a good thing? Diameter is 1.1 inch more on XRV & dual wheel spacing 13.5" compared to 12" for XZA2. Axle ratings Fr 13,200 lbs Rr 20,000 lbs. Any thoughts or suggestions? Share this post Link to post Share on other sites
huffypuff Report post Posted March 30, 2014 It's best you talk to tireman9 Share this post Link to post Share on other sites
tireman9 Report post Posted March 30, 2014 Right off the bat I would be concerned with the need for greater "dual Spacing". Going from a requirement of 12" to 13.5 is probably going to require new wheels. In the Michelin RV Tire guide on pg 11 they outline dual spacingLooking on the Mich tire data web page we see the requirement for 8.25 or 9.0 wide wheels.for the XRV305/70R22.5 LRLI can't be sure, but it is possible that your XZA1 275/70R22.5 LRH came on 7.5 wide wheels so you need to confirm your wheels meet BOTH the width and offset requirements.You are correct that the larger XRV would require less pressure to carry the same load. While you provided your axle "ratings" you did not provide your actual corner loads or even just the actual total load on each axle.Without knowing the actual load requirements it's difficult to offer suggestions on inflation (including an extra margin which can be beneficial) A 275/70R22.5 LR-J is rated at 6,940# @ 130 psi and 6,305#@120 Dual, so this size meets the needs of the axles of 13,200 and 20,000.While it may seem logical to assume a lower psi in the 305/70R22.5 LRL size would translate to improved ride there are other tire construction features that may not support that "assumption".One thing that is probably true is that the larger tire with it's shallower tread depth could deliver a slight improvement in fuel economy but that savings may not be enough to offset the cost of the wheel change. Share this post Link to post Share on other sites
wolfe10 Report post Posted March 30, 2014 You will also have the verify that you have clearance with the wider tire between it an suspension and body parts. As Roger said, your 275's may already have a reasonable safety margin-- won't know until actual coach weighting (4 wheel positions best). Share this post Link to post Share on other sites
hrgottman@hotmail.com Report post Posted March 30, 2014 Thanks for the responses, I have the corner weights these are the heaviest & probably the max we will be within a couple hundred pounds ever. L front 6,300- R front 5,850, L rear 9,300- R rear 8,960. The wheel size & dual spacing is going to take a few days the coach is in storage 75 mile round trip away, same for the clearance concerns. I am not trying to make a big deal about the XRVs but now is the time to inquire not after spending $4,000 + . Thank you both for the thoughtful questions. PS these weights were with 150 gallons of fuel, full fresh water 100+ gallons & enough STUFF for a 4 month trip. Share this post Link to post Share on other sites
hrgottman@hotmail.com Report post Posted March 31, 2014 I spoke to Spartan today, the build sheet for my chassis states 7.5" rims they do not list duals spacing but do note 2" between duals. So lets take the Michelin published overall width of 10.8" + 2" spacing =12.8" not good enough, 13.5" needed & also the XRVs need 9.0" or 8.25 rims not 7.5". Regarding Brett's clearance concerns, a DS owner on Irv2 with the bigger rims installed the XRVs with no problems. One other piece of info, a Spartan Alteration Label sent on 3-4-04 stating correct tire pressure for installed wheels is not to exceed 120 PSI not the 123 PSI provided with coach as delivered on 2-21-04. Am I to be concerned about this going forward ? Any suggestions on the best & safest tire, wheel combo. If there is more info needed I will try to get it. Share this post Link to post Share on other sites
tireman9 Report post Posted April 8, 2014 RE tire pressure. What is the number on the Tire placard. Based on the above I think it would be 120psi. The GAWR for each axle must exceed the load capacity total for all the tires on that axle (singles and duals). Not sure about the various communication specs. I would not consider any of them to be final. If there are numbers that do not match then Spartan needs to explain which numbers are correct. Share this post Link to post Share on other sites
RDavidPhillips Report post Posted April 30, 2014 We have a 2008 Newmar Dutchstar #4304 - tag. Currently has Michelin XRV305/70R 22.5 tires. Looking to buy 8 new Michelins. Been told MIchelin is not producing the same tires. Tire shop suggested using Michelin XZA2 295/80R 22.5. Has anyone made the switch from 305/70R to 295/80R that has the same 2008 DSDP #4304? Thanks in advance, David Share this post Link to post Share on other sites
