Why? What does the in-wheel system do better than the cap type? Except be harder to service.
My TPMS cap-type system has worked without any issues for over 7 years on my toyhauler. And it's a snap to change
the batteries when necessary.
There is
that, but then, the cap style jobbies have been known to provide spurious signals due to their exposure to the sun &/or wind; they can flop around on the valve stem, sometimes being damaged in the process and occasionally even being ripped off; they are far more exposed to damage in general, just thru use & the weather they get to operate in; they are far more exposed to environmental temp variations & road hazards etc; if they are over tightened during any removal/change air pressure/replacement process, they can jam their internal rubber seal so far down into the valve stem that from there on in they will only return temp & pressure readings that reflects whatever's going on
IN the valve stem itself, which might or might not have little to do with anything that's going on inside the tire re temp & pressure..... and there's a whole bunch more besides!! Been there, done that, tested many,
many different makes of valve cap mounted TPMS sensors, and so far, they've
ALL eventually exhibited one or more of these issues &/or failures!! :gaah:
At best, the externally mounted valve cap style TPMS senders are pale imitations of the internally mounted jobbies, imitations that
might sometimes work OK; while the internally mounted units usually outlast the cap style units by a significant factor (I'm still using one set I purchased in the late 1990's!!) they'll usually outlast a tire between any necessary servicing; they are rarely bothered by any addition/release of pressure from inside the tire; they are well protected from external environmental changes &/or hazards; and overall, they are
far more reliable & consistently 'accurate' than the cap type jobbies..... :lecturef_smilie:
That said, the valve cap jobbies are certainly better than nothing - most of the time!! But while you may have been lucky (so far!

) Possible, I wouldn't recommend that you trust them exclusively to always tell you what you should know & need to know about what's happening inside your tires...

in fact,
I don't!! I run internally mounted sensors on my
own Spyder wheels, but I do use the valve cap jobbies whenever I'm running a set of 'loaners' &/or test rims & tires and I
STILL check my tire pressures with a known reliable tire pressure gauge before I fit them; and if the TPMS starts telling me the tire's temp &/or pressure is acting up or varying beyond what I've come to expect, then I confirm that change with my 'known reliable' instruments before getting too carried away - and funnily enough, more often than not, it's likely to be a 'cap sensor' issue or failure rather than a 'real problem'!! :banghead: And yet with the internally mounted sensors (well, since the early days of running the internal TPMS sensors when there were a few 'initial set-up' issues anyway) I just don't
EVER get them!

hyea:
A TPM System & either style of sensor are part of the latest & greatest range of
Handy tools that can improve our ryding safety, but they're
still just tools - and the cap style sensors are fairly 'cheap' tools at that! :shocked: The good quality internally mounted sensors are a much better quality tool that not only does the job better, but they usually last longer, work longer, work better, and often provide you with a bunch more & better info too! :yes: But I'll still use the cap style sensors whenever circumstances makes that the easiest option to save me having to crawl around on the ground checking tire pressures! :thumbup: