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Everything posted by bmctx

  1. tireman9, Thank you for the additional details! I get your math, and I definitely want to make sure I am not underinflating. Of course, overinflating has other concerns such as stopping distance or handling/ride issues perhaps. I will be looking for a four point scale. Any ideas on finding one in the Dallas-Fort Worth area. The truck driver at Love's (where the CAT scale was) sort of snickered at me when I suggested that they do exist and this is the proper method to weigh a motor home (I guess he was thinking unicorns and stupid non-pro). Would you be concerned that the XRV chart for 255/80R22.5 says max at 110 vs. the 115 that one would calc for the rear by adding the extra 10% (after the 0.53 multiplier)? It seems that multiplying the rear 17140 by 0.53 (9050) is adding nearly 5.5% to each "theoretical" weight/side (17140/2=8580*1.056=9050) ... assumption seems that one side may be carrying an extra 470 lbs. I can see how that could be (thus need four point weight) given tank locations no matter how I try to balance the onboard weight. Since I am a math guy, I threw the XRV chart into a spreadsheet and had it calc the % difference between PSI jumps and corresponding single and dual jumps. It is strange that the PSI jumps are between 7.1 and 4.8 % where as the corresponding lbs jumps do not coincide and are widely inconsistent (not sure I can paste it but will try). For instance, between 80 & 85, PSI goes down by 0.4%, Single goes down by 2.4%, Dual goes up by 0.5%. There must be some complex calculus involved in developing this chart. Michelin XRV 255/80R22.5 Load & Pressure Chart 8-19-2019 https://www.michelinrvtires.com/tires/selector/#!/info/xrv PSI PSI %dif SINGLE LBS Single %dif DUAL LBS Dual %dif 70 0.0% 3875 0.0% 7050 0.0% 75 7.1% 4070 5.0% 7410 5.1% 80 6.7% 4300 5.7% 7720 4.2% 85 6.3% 4440 3.3% 8080 4.7% 90 5.9% 4620 4.1% 8410 4.1% 95 5.6% 4805 4.0% 8820 4.9% 100 5.3% 4975 3.5% 9050 2.6% 105 5.0% 5150 3.5% 9370 3.5% 110 4.8% 5205 1.1% 9610 2.6%
  2. Apologies for just returning to this. We had to take the motor home out on a quick trip this past week. I weighted it down (all tanks full - LP, diesel, fresh, grey, black) and some typical cargo. I could not find a handy four-point scale (one trucker tried to tell me they do not exist). The CAT shows the front axle at 8940 and the rear axle at 17160. If I factor another 10% on each axle as has been suggested, here are the figures I get: Front 8940*1.1/2=4917 and Rear 17160*1.1/4=4719. The difference from max for the XRV 255/80R22.5 is 288 pounds on each front and 86 on each rear. This assumes I am going to put another 2,610 pounds on the coach which I cannot imagine. Bottom line is 1) I now see why you guys are always asking about the actual weight and 2) I feel much better about the XRV stats. At my actual weight + 10%, the Michelin site shows 100 PSI single and about 105 dual. In answer to Manholt's questions: 1) those are the weights, 2) owned for a little over a year, and 3) the tires are all at eleven years if memory servers (forgot to get the actual codes) with minimal but noticeable weather checking especially on the front. Here is a follow-up question related to the XRV load table. If I took my actual loaded weights and applied the table, I would get 1) 4470 per tire on the front which is close to 85 PSI on the table and 2) 8580 per dual on the rear which would probably need to be rounded to 95 PSI on the table. These are well below the Winnebago sticker of 105 each. What should I go by - actual weight on the Michelin table or the 105 PSI on the plate from Winnebago? Either way, it looks like the XRVs still fit my need. Since I am concerned about ride quality as well as safety reputation, I think XRV is in my future unless someone tells me I need to rethink. Thanks for the opinions.
  3. I am a new member who has been trying to read everything I can on the tire topic. We have a 2003 Winnebago Journey DL WKP39QD. It came with and continues to have Michelin XRV 255/80R22.5s. As I have spent every spare moment lately researching and thinking about new tires, I came across this concern as I reviewed the placard. The GAWR front is listed as 10,410 lbs. Divide that, and you get 5,205 lbs. The placard lists the cold inflation pressure as 105 psi. Looking at the Michelin website for these tires, it lists the inflation pressure for single 5,205 lbs to be 110 psi which is also the max load and pressure for this particular tire. So, I am assuming that something has changed in the past 15 years with these tires to make Michelin feel they require 5 more lbs to carry the same weight. In that case, I am concerned that I have zero wiggle room (as I think one gentleman ups his inflation by 10% - maybe Bill?). Meaning, at my max GAWR front, I would have to max out this G rated tire. This is making me want to move up to an H rated tire at a minimum. However, as you probably are aware, I cannot find another tire in this size. I have learned enough from you all to realize I need to be aware of the Min Dual Spacing required as well as possibly clearance for the wheel wells. It seems that most of the "close" sizes have a higher (at least by 4/10 of an inch or more) Min Dual Spacing requirement. I have the stock 22.5x8.25 aluminum rims. At this point, I really do not care about the price. I am not trying to be uppity, but even a $1000 overall price difference (less than $200/year) is not worth the hassle or worry. I just want tires that are comfortable and safe. Comfort may mean higher load range for a bit lower inflation pressure. Safe, to me, means I have a margin on the weight (yes, I know not to exceed the GAWR - but the pressure max on the old tires seems a concern). In a previous DP, I replaced the XRVs w/Toyos. My personal experience was that the old XRVs had a superior comfort (very noticeable for us) to the new Toyos (M154s). I do believe Toyos are very good tires, so I am not trashing them. I am just stating my experience on a previous motorhome. Any advice or suggestions would be awesome. I really do need to make a decision ASAP.
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