C-925790 Report post Posted March 21, 2021 I recently purchased TST-507-FT TPMS kit to install on my 2014 Newmar Ventana. The installation was fine except for the inner dually tires. The valve stem for these tires is slightly larger in diameter that the rest of the tires. Consequently, the sensor can not be screwed onto the valve stem. Has anyone have or heard of this problem and have a recommendation on how to resolve it? Share this post Link to post Share on other sites
hermanmullins Report post Posted March 21, 2021 Welcome to the Forum. I would go to a truck tire shop and have the correct size stem installed. Herman Share this post Link to post Share on other sites
rayin Report post Posted March 21, 2021 (edited) I never heard of an oversize valve stem. Are you sure there isn't an adapter screwed onto the inner stems, or they may have became slightly bent. Does a standard metal valve cap screw on OK? Have you tested those sensors on different stems? That's all I have to offer. Edited March 21, 2021 by rayin Share this post Link to post Share on other sites
wildebill308 Report post Posted March 21, 2021 C-925790, Welcome to the forum. New one on me. I have never seen a oversize valve stem on a RV. Bill Share this post Link to post Share on other sites
charlieiam Report post Posted March 22, 2021 (edited) Do a search for "Are there different valve stem sizes." That should give needed information. Edited March 22, 2021 by charlieiam Share this post Link to post Share on other sites
wayne77590 Report post Posted March 22, 2021 (edited) Valve stems can be 0.453 inches in diameter or 0.625 inches in diameter. Typically the 0.453 is the norm for our HP engines but as you get up to the much higher commercial HP vehicles it is the 0.625 size. If you have the larger size I would think it was a mistake or someone didn't have the normal size and stuck in the larger size. Tireman - check in please. Edited March 22, 2021 by wayne77590 Share this post Link to post Share on other sites
rayin Report post Posted March 22, 2021 (edited) .I just spoke with the owner of the largest HDT repair shop in the area. He said all valve stems have the same threads and O.D. Only the base of valve stems are the two different sizes Wayne listed. This means either the stem has been deformed or threads ruined. Reference: https://www.coyoteaccessories.com/valve-stems?p=3 Quote: " Valve Stem Sizes Depending on the application, valve stems holes in wheels will be typically 0.453” for cars / light duty trucks and 0.625” for heavy duty / commercial truck applications. Based on application, valve stems are available to fit 0.453” or 0.625” holes. Some clamp in models are configured to work in either size hole by simply changing the supplied grommet to different size. Edited March 22, 2021 by rayin Share this post Link to post Share on other sites
wayne77590 Report post Posted March 22, 2021 With only a 0.172 inch difference I would think the grommet would make the difference for hole size. Share this post Link to post Share on other sites
manholt Report post Posted March 22, 2021 C925790. Welcome! Are you the original owner of the Vantana? What length model is your coach? Share this post Link to post Share on other sites
kaypsmith Report post Posted March 23, 2021 That style sensor is not round, rather an elongated style, probably the stem is too close to the outer rim and wont allow a straight screw on effect. most truck valve stems are made of brass and can be bent slightly for a better fit. Question for OP is, does a regular metal valve cap screw on correctly? If it does,, then you may be able to cover the cap with a short piece of rubber hose the same inner size as the outer of the cap, then carefully with a pair of pliers bend the stem toward the center of the outer wheel to give relief for the tpms to screw on. If you don't feel comfortable with this task, take to truck tire shop and ask for help. Share this post Link to post Share on other sites
C-925790 Report post Posted March 23, 2021 2 hours ago, manholt said: C925790. Welcome! Are you the original owner of the Vantana? What length model is your coach? No, I bought it last Oct. and the coach is 43'. Share this post Link to post Share on other sites
C-925790 Report post Posted March 23, 2021 On 3/21/2021 at 2:10 PM, rayin said: I never heard of an oversize valve stem. Are you sure there isn't an adapter screwed onto the inner stems, or they may have became slightly bent. Does a standard metal valve cap screw on OK? Have you tested those sensors on different stems? That's all I have to offer. No, a metal cap doesn't fit on it, in fact the stem on the 2 inner dually tires didn't come with caps as all the other tires did. I didn't have any issues installing the sensors on the other 6 tires. Share this post Link to post Share on other sites
C-925790 Report post Posted March 23, 2021 1 hour ago, kaypsmith said: That style sensor is not round, rather an elongated style, probably the stem is too close to the outer rim and wont allow a straight screw on effect. most truck valve stems are made of brass and can be bent slightly for a better fit. Question for OP is, does a regular metal valve cap screw on correctly? If it does,, then you may be able to cover the cap with a short piece of rubber hose the same inner size as the outer of the cap, then carefully with a pair of pliers bend the stem toward the center of the outer wheel to give relief for the tpms to screw on. If you don't feel comfortable with this task, take to truck tire shop and ask for help. No, the stem for the inner tire sticks straight out the back of the outer tire's rim. There is nothing in the way of screwing the sensor onto the stem. Share this post Link to post Share on other sites
C-925790 Report post Posted March 23, 2021 On 3/21/2021 at 2:00 PM, hermanmullins said: Welcome to the Forum. I would go to a truck tire shop and have the correct size stem installed. Herman I have an appointment with an local tire store Friday morning. I'll let you all know what I find out. Share this post Link to post Share on other sites
rayin Report post Posted March 23, 2021 (edited) 1 hour ago, C-925790 said: No, a metal cap doesn't fit on it, in fact the stem on the 2 inner dually tires didn't come with caps as all the other tires did. I didn't have any issues installing the sensors on the other 6 tires. Well, I learned something new today. Obviously I'm not too old to learn. Turns out there is a large bore valve stem and valve core. Does your valve stem look like those pictures? The good news is this company sells large bore to standard bore adapters.https://tiresupplynetwork.com/search?type=product,page,article&q=large bore valve stem* NAPA sells them too. The hole in the rim is .8125" Edited March 23, 2021 by rayin Share this post Link to post Share on other sites
kaypsmith Report post Posted March 23, 2021 9 hours ago, rayin said: Well, I learned something new today. Obviously I'm not too old to learn. Turns out there is a large bore valve stem and valve core. Does your valve stem look like those pictures? The good news is this company sells large bore to standard bore adapters.https://tiresupplynetwork.com/search?type=product,page,article&q=large bore valve stem* NAPA sells them too. The hole in the rim is .8125" Yep Rayn, we all can learn cant we. https://tiresupplynetwork.com/products/large-bore-to-standard-bore-adapter?_pos=5&_sid=45003ccd8&_ss=r Here is the adapter needed to adapt that large bore down so that the valve stems will not need replacing, was listed on the website that you showed, $2.99 each. Then while replacing tires next time have the stems replaced. Share this post Link to post Share on other sites
richard5933 Report post Posted March 23, 2021 So all this information still leaves a question... If I'm reading all this correctly, the inner duals had a different size valve stem than the other tires. Why? Just doesn't make sense for only two tires to have these larger valve stems. Did they expect the user to carry two sets of everything needed to maintain them (tire gauge, etc.)? Share this post Link to post Share on other sites
rayin Report post Posted March 23, 2021 (edited) If he truly has special rims for the large bore valve stems he cannot simply have the stems replaced. The .812" /7/8"rim hole is too large to safely use a standard metal valve stem. It's either use those adapters or replace rims. I'd really like to see a picture of his present stems. Richard's thought of only 2 special rims not making sense is logical. Edited March 23, 2021 by rayin Share this post Link to post Share on other sites
C-925790 Report post Posted March 23, 2021 (edited) 12 hours ago, rayin said: Well, I learned something new today. Obviously I'm not too old to learn. Turns out there is a large bore valve stem and valve core. Does your valve stem look like those pictures? The good news is this company sells large bore to standard bore adapters.https://tiresupplynetwork.com/search?type=product,page,article&q=large bore valve stem* NAPA sells them too. The hole in the rim is .8125" Its hard to tell since these pictures have the caps on and there is no picture showing the end of the stem. I'll check with my local NAPA store for the adapter. Edited March 23, 2021 by C-925790 Share this post Link to post Share on other sites
wildebill308 Report post Posted March 23, 2021 Just a guess but it sounds like someone replaced the inner rims with rims with the big valve stems or Newmar just used/put on rims with big valve stems and didn't notice it. Lots of times they use aluminum on the outers and steel on the inside rims. Bill Share this post Link to post Share on other sites
C-925790 Report post Posted March 23, 2021 1 hour ago, rayin said: If he truly has special rims for the large bore valve stems he cannot simply have the stems replaced. The .812" /7/8"rim hole is too large to safely use a standard metal valve stem. It's either use those adapters or replace rims. I'd really like to see a picture of his present stems. Richard's thought of only 2 special rims not making sense is logical. As you can see, there are large openings in the back of the outer rim that a rubber grommet fits into and the stem goes through the center of the grommet. Share this post Link to post Share on other sites
C-925790 Report post Posted March 23, 2021 3 hours ago, richard5933 said: So all this information still leaves a question... If I'm reading all this correctly, the inner duals had a different size valve stem than the other tires. Why? Just doesn't make sense for only two tires to have these larger valve stems. Did they expect the user to carry two sets of everything needed to maintain them (tire gauge, etc.)? Actually, the tire gauge and air chuck that I use work on both types of valve stems. Share this post Link to post Share on other sites
kaypsmith Report post Posted March 23, 2021 The larger inner valve stem may have been specked there for more rigidity because of the need for a longer stem. The rubber grommet is used to as a stabilizer for same reason. Share this post Link to post Share on other sites
rayin Report post Posted March 23, 2021 (edited) I think I understand after viewing your pictures. You have a flow-thru valve cap on a standard valve stem. It will unscrew to expose the standard size threads and standard valve core.. Think of it as a really short valve extension. Remove that flow-through stem cap and you should be able to screw on a standard metal valve cap or a pressure sensor. Matter of fact I have those on my sensors on inner duals too now that I know what we're discussing. That explains why your standard air gauge fits, only the threads are larger as it is not designed to accept a metal valve cap because it is designed to be both a short extension and valve cap combined. (it has its own rod inside to depress the original valve core in the stem). Kay is right, the large rubber grommet is there to stabilize the long original valve stem. Edited March 23, 2021 by rayin Share this post Link to post Share on other sites
jleamont Report post Posted March 23, 2021 As Ray said. Remove the flow through cap, your TPMS will fit then. Share this post Link to post Share on other sites
