I have after market rims and my car uses tire pressure sensors., so i bought new sensors and i mocked it in and their is this gap. don't know anything about this, so is this gap normal or is it suppose to be flush against the rim?

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Plus their is a part on the stem that is threaded for what looks like a nut to go on so it could be tightened for a good seal. But the sensors never came with this nut, do I need it and if I do were can i get it?

 

The gap between the sensor and the wheel shouldn't matter at all. The people installing the tires just have to be a bit more careful.

You already have four of the nuts you're asking about. They're holding your stock TPM sensors into the factory wheels. As long as there's room in the aftermarket wheels for that nut to fit into you'll be fine. If not, you'd have to use a regular valve stem and live with a tire monitor light on all the time... or find different wheels.

 

Does the dinging just happen when you turn the car on or every so often does it start dinging again?

 

looks good to me

 

It'll happen when you turn the car on and that's it, but you'll always have a flashing Tire Monitor light.

 

Also I don't have the metal valve stem on my stock steelies, its just rubber.