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Here is the thing- from a pressure aspect- you should be able to put whatever you want on it. Physically it will not be shorter/taller etc and affect a TPMS module (former TPMS module sensor+controller+RF chip engineer in past life). However the problem is with how the stem is constructed from a materials aspect. Most higher end cars which go higher speed or can hit the racetrack use metal TPMS stems on the wheel. The more basic, non-TPMS or regular stems are rubber with a brass valve stem.
The problem when it gets cold, or from salt in the road etc- brass and aluminum/steel can have a reaction that causes them to stick. I have never seen this happen on a car of my own, but I have heard stories about it, and I also lived in very moderate climates. When they stick (typically the rubber stem with brass connection to the steel or aluminum stem cap), I hear they require pliers, dremels to be removed. That can snap the rubber base off, and you end up with flat tires, and needing to remount the tires.
I suspect these caps you linked are plastic and metal options but cannot tell from the photos. Metal for the TPMS module cars (newer and have metal housings), and plastic for the older cars without TPMS and the brass threading. Of course plastic could probably be used for any type. I did a quick search and here are some horror stories for those that mixed the steel/aluminum with brass. Again- no issues for me ever- but there is always a corner-case that engineers have to address and write a spec for even the smallest things. http://fdo-workspace.blogspot.com/20...-removing.html http://clubsx4.com/forum/archive/index.php/t-2576.html
I run my street/race cars without caps at all, because adding four cap-take-offs, and four cap-replacements to the 10-15 times I might have to check or reset my tire pressures at a race, is a red-tape pain. I do use the info I get from TMPS, at races, between runs etc, and it correlates to what my fancy hand-held tire-pressure gauge shows, and that info is going to be sent, regardless of cap, let alone cap color or material. If the cap was for anything besides keeping the valve innards clean, then the TPMS data would be showing a leak when running without caps. It doesn't.
HTH,
Joe
Last edited by Joe Weinstein; 04-23-2020 at 03:38 PM.
I run my street/race cars without caps at all, because adding four cap-take-offs, and four cap-replacements to the 10-15 times I might have to check or reset my tire pressures at a race, is a red-tape pain. I do use the info I get from TMPS, at races, between runs etc, and it correlates to what my fancy hand-held tire-pressure gauge shows, and that info is going to be sent, regardless of cap, let alone cap color or material. If the cap was for anything besides keeping the valve innards clean, then the TPMS data would be showing a leak when running without caps. It doesn't.
HTH,
Joe
Over the years I have had friends get nearly flat tires on the race track due to leaking valve stems that pick up debris or just plain fail when no cap was installed. If you have a sealing valve cap (like most decent ones with the o-ring in it) it also acts as a fail safe to keep the pressure in the tire, in the event a valve isn't sealing properly. In an autocross it might not matter since the runs are short and lower speeds are attained and there's no car around you, so the risk of a tire going low isn't all that high. But on a race car I'd always use valve caps since I don't want a tire to fail for a cheaply preventable reason. And on Cayennes that see dirt, lots of washes, etc., caps predictably reduce the risk of the valve leaking or corroding and wearing out. I'm a fan of caps!
Thanks yes, that make sense too. I don't do track days, just freeway and autocross. I am too aggressive for the track. And I'm tire-obsessed, checking pressures a lot at the beginning of every drive, then every 25 minutes or so, once I'm comfortable that everything is stable and warmed up to where I want them. My wife accepts that I will get other driver's attention in the street if I see their tires too low, or if their tire wear shows some horrible misalignment issue...
Thanks yes, that make sense too. I don't do track days, just freeway and autocross. I am too aggressive for the track. And I'm tire-obsessed, checking pressures a lot at the beginning of every drive, then every 25 minutes or so, once I'm comfortable that everything is stable and warmed up to where I want them. My wife accepts that I will get other driver's attention in the street if I see their tires too low, or if their tire wear shows some horrible misalignment issue...
You must love TPMS! I know I do, and greatly miss it on the cars that don't have it!! Nothing like knowing your pressures while rolling along!
Yes, modern stuff is so good. And as an elder, I find it more and more important to save my energy. In the 80's I'd load a roof rack with race tires and a jack, zip to an AM race where I change the wheels, *remove the roof rack*, and do my race+work. Then I'd reassemble, and drive AFAF 90 miles to do it again at a second PM event that day.
Nowadays, I always stay at a motel near by the night before, drive and run the car exactly as-is, get as sit-down a work assignment as I can, and even then, I don't always fully recover my energy and focus between runs, and it's a real pain if I have to get out of the car to check things. With the TPMS, I can see at the dash whether the tires cooled enough to stay in my pressure range... Some of our events are whole-day, with 5-7 runs AM and PM. Nowadays it's a 50/50 question whether I can focus and deliver in the PM...
Heck, I raced pre-ABS! I had a car with so much weight imbalance in the front that I'd dial in a leeetle bit of left-turn while braking hard, even for a right-hand turn, so my front right tire didn't break loose and flat-spot.
I've been using whatever, plastic, aluminum-valve stem caps and have never had a single issue with any TPMS.
TPMS is fantastic. It has saved me this past winter when I had picked up a screw in the tire and I was able to pump the slow leaker back up and when I got home I plugged the tire.
With the TPMS, I can tell how all the pressures are at a glance as those that enjoy some spirited driving that I'm on-point with how all the tires will work.
01-30-2020, 04:30 PM
with TPM, why are special valve caps necessary?
