fatbill Report post Posted August 30, 2020 May have been discussed, but I'm confused a bit..... My coach tag says my front and rear tires should be 80 PSI for the weight of the unit... The manufacturer of the tires I had put on says the tires should be 120 PSI.. They are 245 70R 19.5 on a 1999 Fleetwood Flair 34D Share this post Link to post Share on other sites
richard5933 Report post Posted August 30, 2020 Welcome to the FMCA Forum! Glad to have you join us. When you say: 1 hour ago, fatbill said: The manufacturer of the tires I had put on says the tires should be 120 PSI.. ...are you talking about what's on the sidewall of the tires as the 'max cold inflation' for the tires? If so, then that would be the amount of air necessary to carry the max load the tire is rated for, not necessarily the pressure that should be in your tires. The best way to determine the proper tire pressure is by knowing your coach's actual weight (by axle) as you typically roll down the road, and then using the manufacturer's load & inflation charts to select the correct pressure. If you post the brand & model tires you got someone will surely help you find the load & inflation chart. Share this post Link to post Share on other sites
rayin Report post Posted August 31, 2020 I go by the Federal Tire Placard air pressure in my MH. It works well for me. I wonder what people did before tire pressure monitors were widely sold? Goodyear says reducing air pressure to obtain a better ride is futile. Share this post Link to post Share on other sites
richard5933 Report post Posted August 31, 2020 7 hours ago, RayIN said: ...I wonder what people did before tire pressure monitors were widely sold? Goodyear says reducing air pressure to obtain a better ride is futile. They used a tire gauge daily. Not sure where you are getting the information about Goodyear's recommendation. If a coach is intended to ride at 80psi and you put 120psi in the tires the coach is going to ride like it's on rails. Putting the proper air pressure in the tires will certainly improve the ride if they are overinflated by 50%. Share this post Link to post Share on other sites
ianbullock Report post Posted August 31, 2020 19 hours ago, fatbill said: My coach tag says my front and rear tires should be 80 PSI for the weight of the unit... As Richard said, "The best way to determine the proper tire pressure is by knowing your coach's actual weight (by axle) as you typically roll down the road, and then using the manufacturer's load & inflation charts to select the correct pressure." in lieu of this, you should inflate your tires to the 80 PSI specification as per you coach placard. Share this post Link to post Share on other sites
rayin Report post Posted August 31, 2020 (edited) 3 hours ago, richard5933 said: They used a tire gauge daily. Not sure where you are getting the information about Goodyear's recommendation. If a coach is intended to ride at 80psi and you put 120psi in the tires the coach is going to ride like it's on rails. Putting the proper air pressure in the tires will certainly improve the ride if they are overinflated by 50%. That's what I mean, there were no load/inflation charts, they went by the Federal Tire Placard in/on the vehicle. Page 8 of: https://www.goodyearrvtires.com/pdfs/rv_inflation_guide_nov112014.pdfa and paragraph 2 of Tire Loading in this pdf: https://www.goodyearrvtires.com/tire-inflation-loading.aspx Edited August 31, 2020 by RayIN Share this post Link to post Share on other sites
richard5933 Report post Posted August 31, 2020 58 minutes ago, RayIN said: That's what I mean, there were no load/inflation charts, they went by the Federal Tire Placard in/on the vehicle. Page 8 of: https://www.goodyearrvtires.com/pdfs/rv_inflation_guide_nov112014.pdfa and paragraph 2 of Tire Loading in this pdf: https://www.goodyearrvtires.com/tire-inflation-loading.aspx Until the vehicle is weighed, the tire placard is a good starting pressure. On the same page you linked to, in the right-hand column, is a button to download the load & inflation table. That table spells out the specific pressure to be used according to weight. Every quality tire manufacturer publishes load & inflation tables. Share this post Link to post Share on other sites
fatbill Report post Posted August 31, 2020 22 hours ago, richard5933 said: Welcome to the FMCA Forum! Glad to have you join us. When you say: ...are you talking about what's on the sidewall of the tires as the 'max cold inflation' for the tires? If so, then that would be the amount of air necessary to carry the max load the tire is rated for, not necessarily the pressure that should be in your tires. The best way to determine the proper tire pressure is by knowing your coach's actual weight (by axle) as you typically roll down the road, and then using the manufacturer's load & inflation charts to select the correct pressure. If you post the brand & model tires you got someone will surely help you find the load & inflation chart. Sorry.. this is all greek to me.... The Tires are 245 70R 19.5 load range H I have Double Coin RT600 Steer tires on the front. The link to the spec sheet is: https://www.doublecointires.com/tire/rt600/ On the rear I have model RLB 490. The link to their spec sheet is: https://www.doublecointires.com/tire/rlb490/ The Fleetwood Flair spec sheet shows the GAWR for the front at 7000 and Rear at 13500 GVWR 20.500 and GCWR 24,000 hopefully this will help me get information.... I'm confused about being able to take the tire down to 80PSI from 120PSI, mainly because I do not understand :( Share this post Link to post Share on other sites
richard5933 Report post Posted August 31, 2020 57 minutes ago, fatbill said: Sorry.. this is all greek to me.... The Tires are 245 70R 19.5 load range H I have Double Coin RT600 Steer tires on the front. The link to the spec sheet is: https://www.doublecointires.com/tire/rt600/ On the rear I have model RLB 490. The link to their spec sheet is: https://www.doublecointires.com/tire/rlb490/ The Fleetwood Flair spec sheet shows the GAWR for the front at 7000 and Rear at 13500 GVWR 20.500 and GCWR 24,000 hopefully this will help me get information.... I'm confused about being able to take the tire down to 80PSI from 120PSI, mainly because I do not understand Where are you getting the number 120 psi as the proper pressure? If it's from the sidewall of the tire, then it is the max cold pressure, not the recommended pressure for your coach. Let us know where you got that number and we can go from there. Share this post Link to post Share on other sites
fatbill Report post Posted August 31, 2020 (edited) The spec sheet shows 120PSI and that is what the tire shop I got these installed from set them at. I got confused when I saw the placard on the coach talk about 80PSI The Tires show max 120PSI cold weight on the sidewall ps.. I much appreicated your help Edited August 31, 2020 by fatbill Share this post Link to post Share on other sites
jleamont Report post Posted August 31, 2020 Ideally you should have all 4 corners of the RV weighed (scale under each wheel position, not the entire axle) equipped the way you travel (all items stocked inside including passengers and the fresh water tank full). I checked and the PSI rating from the chassis label is assuming the vehicle is loaded to its MAX axle ratings. Since you do not have 4 corner weights running the 80 PSI is OK but there is a concern especially if the chassis is overloaded which is NOT uncommon. Personally I like to run 20% higher and see how it feels, if it wanders i'd back it down 5 PSI but wouldn't go below the 80 PSI rating from the chassis manufacture. The 120 PSI rating on the tire is a MAX pressure, you would ONLY need that if you had 9610 (or 4805 lbs on each front wheel) lbs of weight on the steer axle and 18160 lbs (or 9080 lbs on each dual wheel set) on the drive axle. Since your axle weight ratings are no where near that I wouldn't run that much PSI in your tires. I guess at this point you can see where having the coach weighed on each corner is so important. How does it handle with that much PSI in the tires? FYI, most tire shops have an SOP to fill tires to their MAX PSI rating, they do not want to be responsible for underinflated tires nor do they know what your vehicle weight is. The chart below is from the Double Coin website. Share this post Link to post Share on other sites
fatbill Report post Posted August 31, 2020 19 minutes ago, jleamont said: I How does it handle with that much PSI in the tires? FYI, most tire shops have an SOP to fill tires to their MAX PSI rating, they do not want to be responsible for underinflated tires nor do they know what your vehicle weight is. It rides like I'm driving on rocks, expecially if I hit a rough patch or a bump.... no 'give' in the ride at all Share this post Link to post Share on other sites
manholt Report post Posted August 31, 2020 Try 100# until you have coach weight (you can do that at any Truck Stop that has a CAT scale), then use Joe's chart. Share this post Link to post Share on other sites
richard5933 Report post Posted August 31, 2020 Agree here as well. Drop the pressure to about 100 and then take it to get weighed. If you can't find a place to weigh each corner separately, most truck stops will have a CAT Scale where you can get the weight per axle for $11-$12. If you are unsure how to get weighed when you get to the truck stop, go to the trucker's fuel desk and ask - they will walk you through it. You don't need to buy fuel to weigh - it's a separate transaction. Helps to do a Google Maps satellite view of the truck stop before you get there so you are familiar with where things are, where you need to pull in, etc. Especially if you will need to park momentarily while you go to the fuel desk, you don't want to end up facing the wrong way or getting stuck nose-in somewhere that it's difficult to get back out. If you are still confused after getting the coach weighed, report your weights here and someone will help you do the math. Share this post Link to post Share on other sites
fatbill Report post Posted August 31, 2020 You guys are the best... thank you so much for the help with this! Share this post Link to post Share on other sites
rayin Report post Posted September 1, 2020 (edited) 9 hours ago, fatbill said: The spec sheet shows 120PSI and that is what the tire shop I got these installed from set them at. I got confused when I saw the placard on the coach talk about 80PSI The Tires show max 120PSI cold weight on the sidewall ps.. I much appreicated your help That Federal Tire Placard states the recommended air pressure for the GVWR of your MH. If you are not overloaded the 80 psi is correct; at least until you get actual weights. Edited September 1, 2020 by RayIN Share this post Link to post Share on other sites
ianbullock Report post Posted September 1, 2020 9 hours ago, RayIN said: That Federal Tire Placard states the recommended air pressure for the GVWR of your MH. If you are not overloaded the 80 psi is correct; at least until you get actual weights. I agree with Ray, I would go with 80 PSI until you get actual weights. At 120 PSI I am not surprised that It rides like you're driving on rocks, especially if you hit a rough patch or a bump.... no 'give' in the ride at all. I am sure that the back end is probably all over the road as well. Share this post Link to post Share on other sites
fatbill Report post Posted September 1, 2020 Just had another thought.... it seems that after I took it for a ride... an hour or so.... the tires were aweful hot... that part of this? Share this post Link to post Share on other sites
kaypsmith Report post Posted September 1, 2020 (edited) 43 minutes ago, fatbill said: Just had another thought.... it seems that after I took it for a ride... an hour or so.... the tires were aweful hot... that part of this? Not likely! Bad ride yes. Edited September 1, 2020 by kaypsmith Share this post Link to post Share on other sites
hermanmullins Report post Posted September 2, 2020 If the tires are at 120 psi cold just think what they are when they get hot. Herman Share this post Link to post Share on other sites
kaypsmith Report post Posted September 2, 2020 (edited) Tire pressure will increase by 2 percent for every 10 degree temperature. 120 psi @ 70 degrees will increase by 6 percent just by checking again at 100 degrees, therefore just by going from 70 to 100 degrees the same tire will probably read 127.2 at 100 degrees. A number of things including just ambient temperature, temperature of pavement, and friction are all natural causes. Then you can add some heat generated by the braking system. Edited September 2, 2020 by kaypsmith Share this post Link to post Share on other sites
fatbill Report post Posted September 2, 2020 Taking the sage advice I've been given here, I'm taking them down to 95PSI until I can weigh the old gal! Share this post Link to post Share on other sites
rayin Report post Posted September 2, 2020 4 hours ago, hermanmullins said: If the tires are at 120 psi cold just think what they are when they get hot. Herman That is not a concern for the consumer, the tire mfgrs design engineers took care of that before the tire entered production. Where is Tireman9? Share this post Link to post Share on other sites
rayin Report post Posted September 2, 2020 3 hours ago, kaypsmith said: Tire pressure will increase by 2 percent for every 10 degree temperature. 120 psi @ 70 degrees will increase by 6 percent just by checking again at 100 degrees, therefore just by going from 70 to 100 degrees the same tire will probably read 127.2 at 100 degrees. A number of things including just ambient temperature, temperature of pavement, and friction are all natural causes. Then you can add some heat generated by the braking system. + Sunshine. It's a good thing Tireman9 and other design engineers built-in tire safety to account for that. Share this post Link to post Share on other sites
richard5933 Report post Posted September 2, 2020 How hot is "awful hot"? If we're talking about normal tire heating from going down the road, don't worry about it. The sun will also make the tire feel very warm, so if it's sunny you can reach around and check the inner side of the tire just to make sure. But, if we're talking about too warm to keep your hand on the tire, better start looking for problems beyond the tires. A dragging brake or a failing/dry hub bearing can cause excessive heat. Either of these can be dangerous and lead to a blowout and/or a fire. I'm not saying you have either of these problems, but on a 1999 coach they are both possible and worth checking for. If the hubs are oil filled, check to make sure that there is oil in them according to the manual. Brake drag is harder to check for, and a good time to check this is when you are having the brakes inspected/adjusted. (Air or hydraulic, period inspection is a good idea including checking to make sure auto-adjusters are doing their job.) A great tool for any coach is an infrared thermometer 'gun' for checking the temps of the hubs/wheels. Here's the one I use, but there are many others out there: https://www.amazon.com/gp/product/B01MYUVR4R/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1 This is usually done after being driven for some time so that you're checking a fully-warmed hub. The actual temp is not as important as checking to see if you have one which is substantially different than the others, possibly indicating a problem. Don't rely on a stem-mounted TPMS sensor to check the temp of the hubs, as they are too far away. Share this post Link to post Share on other sites
