Tire Extenders
This may be a dumb question but because the tires have to be checked regularly why wouldn't the extenders come standard on the tires from the manufactory?
Forum Discussion
They don't come with extenders because extenders are a really bad idea, when you have someone like NHTSA tracking safety problems.
On RVs, they used to come with 80 PSI rubber-metal stems because that was the cheapest solution that permits a wheel to go on any position. From a safety standpoint, that is an adequate solution if the end user does not add anything heavy to the end of the stem, like a pressure monitor or an extender.
Fleet owners usually order these cab-chassis and cutaways with 1 to 1 1/2 inch metal stems. This lets a wheel go on any position on the vehicle, permits routine service using truck tire service tools, and is still short enough to sustain the loads on the stem when the wheel is spinning and banging down the road. These still do not permit the use of extenders, they will still flex like rubber/metal stems and fail from fatigue.
If you want to use extenders, you need to install the shortest available metal (preferably stainless steel) stems that will fit. These still need to be serviced (replaced, or the gaskets replaced) whenever the tire comes off the wheel for service. Problem with the short stems is that even if you don't use extenders, you need extenders to service the tire, as there is not enough space between rim and stem for the head of a pressure gauge or a chuck.
Usual recommendation for RV users is installation of custom long metal stems that allow service without using truck tools, and often let you check pressure with wheel covers installed. These are not going to be a factory solution, because the wheels then have to go to a specific position, and the long stems have to be properly supported, enough of a problem to become an issue with NHTSA because they put an additional "take care of this for safety" on the operator. Just look at the issues not too long ago with floor mats getting pushed under, or lately with knees bumping switches, or the "sudden acceleration" issues in the 70's from drivers not quite getting the transmission selector into park.
Most you can hope for from the factory is a metal stem long enough to service, short enough to not need support, like those used by fleet operators.
On RVs, they used to come with 80 PSI rubber-metal stems because that was the cheapest solution that permits a wheel to go on any position. From a safety standpoint, that is an adequate solution if the end user does not add anything heavy to the end of the stem, like a pressure monitor or an extender.
Fleet owners usually order these cab-chassis and cutaways with 1 to 1 1/2 inch metal stems. This lets a wheel go on any position on the vehicle, permits routine service using truck tire service tools, and is still short enough to sustain the loads on the stem when the wheel is spinning and banging down the road. These still do not permit the use of extenders, they will still flex like rubber/metal stems and fail from fatigue.
If you want to use extenders, you need to install the shortest available metal (preferably stainless steel) stems that will fit. These still need to be serviced (replaced, or the gaskets replaced) whenever the tire comes off the wheel for service. Problem with the short stems is that even if you don't use extenders, you need extenders to service the tire, as there is not enough space between rim and stem for the head of a pressure gauge or a chuck.
Usual recommendation for RV users is installation of custom long metal stems that allow service without using truck tools, and often let you check pressure with wheel covers installed. These are not going to be a factory solution, because the wheels then have to go to a specific position, and the long stems have to be properly supported, enough of a problem to become an issue with NHTSA because they put an additional "take care of this for safety" on the operator. Just look at the issues not too long ago with floor mats getting pushed under, or lately with knees bumping switches, or the "sudden acceleration" issues in the 70's from drivers not quite getting the transmission selector into park.
Most you can hope for from the factory is a metal stem long enough to service, short enough to not need support, like those used by fleet operators.
