TST TPMS and Valve Stems

[Tireman9]

Originally Posted by bbcubed53

I purchased the TST 507 TPMS system at the International Rally in Doswell last year. After a short time I started to notice rubbed places on my rims where it appeared that the pressure sensor caps are hitting rim while in motion.

Our Airstream is a 2020 30ft International with the OEM valve stems which are high pressure rubber base with a metal stem.

I contacted TST about the markings. They said they had never head of this issue and did not have any solutions. TST was quick to answer my emails but could not offer any advice to resolve the issue. I did inquire about their internal monitors and they provided me information about those.

Although the damage to the rims is disappointing, my biggest concern is a catastrophic failure of the rubber base of the valve stems due to the repeated motion caused by the added weight of the tpms sensors. I have found that most tire dealers in our area aren't knowledgable of the stem mounted sensors as I've inquired with them about solutions. After several conversations I have decided to have one of them install metal value stems (without the rubber base).

This post is make others aware and ask if anyone has had this issue.

Here are the pictures of rim damage.

Don't know who at TST you talked with but I strongly recommend you get bolt in metal valves. the "High Pressure stems still have rubber base and you are seeing the flex. This will eventually fail the valve stem.

[bickp]

Great post. Walked out to my trailer and sure enough the wheels are marked. Calling Discount tire first thing tomorrow and will shuttle two tires at a time. I've got 8k on the rubber stems and feeling lucky. Thanks OP and all contributors.

[bbcubed53]

I have upgraded to Dill 902-w valve stems. Thanks for all the input!

[steelbird312]

Having run into Dill's lack of distribution concerns, I continued my search to another well known US manufacturer, Milton Ind. I ordered a box of 5 from Amazon. Although pleased, much to my chagrin, I find Milton has been sold to a 'group' who, in their wisdom, decided the best place to manufacture this product is China. I received it in 2 days.
Milton 470 TR416 box of 5. $13.26

[Adiredneck]

When I upgraded from 15" to 16" wheels and Michelin XPS Rib tires, I also added the TST 507 TPMS system. I, too, wondered about the effect of the sensors on wheel balance, so I completed the upgrade with Centramatic balancers. On my 5th year and 30,000 plus miles and everything is going great. Remember to change out your batteries every Spring.

[Shads Shack]

This is a much more complex issue than it seems. The issue isn't necessarily the fact that the stem bends under tire rotation-induced forces and the sensor hits the rim. The issue is more the flexing (bending in and out) as the speed changes, resulting in fatigue of the valve. (note that the sensor seating on the rim shouldn't hurt the rim, e.g. metal vs. plastic)



Consider, at some speed the sensor/valve combination (SVC) bends enough to hit the rim. Once it does that the valve stem doesn't flex much until the speed drops enough to bring the SVC off the rim. If, say, the seating speed is 20 mph, then after that the SVC seats and flexes very little until a slower speed is achieved. If, however, the seating speed is 60 mph, the valve stem is flexing a lot more as speeds change. Say on the highway, between 45 and 65 mph.


Consider valve stem with no sensor. It is constantly flexing, as it never seats on the rim. The flex is much less, but happens much more.


In order to get a real design-based conclusion one would have to consult TST to see why rubber stems are OK for the smaller sensors and metal stems are required for larger sensors.

[Mollysdad]

Originally Posted by bbcubed53

I have upgraded to Dill 902-w valve stems. Thanks for all the input!

I love it when a plan comes together!

Originally Posted by Shads Shack

In order to get a real design-based conclusion one would have to consult TST to see why rubber stems are OK for the smaller sensors and metal stems are required for larger sensors.

TST has always said rubber stems are okay. Remember, TST stands for TRUCK Systems Technology. They are thinking 23" rims for a semi, not 15" RV aluminum rims.
They were fortunate enough to score a large portion of the RV market because their word of mouth is so good.
Just replace the rubber stems.

Originally Posted by steelbird312

Milton 470 TR416 box of 5. $13.26

The 416's wouldn't fit my rims. The machined area is too small for the washer and nut to go down in.

[dhroberts]

I use the TST TM-507RV/SE system. Have never had the rubbing of wheel problem. I would think a longer stem would subject the stem to increased forces: excessive swing, road debris, etc. I recently had a rubber stem split concurrent with the adjacent tire blowing out - the metal hook that caused the blowout had a nylon stray attached - I think the strap whipped the adjacent tire's stem causing the stem failure. Double jeopardy! I am going to metal stems prior to my next trip! I am also traveling with two inflated spares for both the tow vehicle and the Airstream. Why not as I have room in the pickup's bed.

[Tireman9]

Originally Posted by Shads Shack

This is a much more complex issue than it seems. The issue isn't necessarily the fact that the stem bends under tire rotation-induced forces and the sensor hits the rim. The issue is more the flexing (bending in and out) as the speed changes, resulting in fatigue of the valve. (note that the sensor seating on the rim shouldn't hurt the rim, e.g. metal vs. plastic)

Consider, at some speed the sensor/valve combination (SVC) bends enough to hit the rim. Once it does that the valve stem doesn't flex much until the speed drops enough to bring the SVC off the rim. If, say, the seating speed is 20 mph, then after that the SVC seats and flexes very little until a slower speed is achieved. If, however, the seating speed is 60 mph, the valve stem is flexing a lot more as speeds change. Say on the highway, between 45 and 65 mph.

Consider valve stem with no sensor. It is constantly flexing, as it never seats on the rim. The flex is much less, but happens much more.

In order to get a real design-based conclusion one would have to consult TST to see why rubber stems are OK for the smaller sensors and metal stems are required for larger sensors.

Having been involved with TPMS since 2002 I have seen and learned a bit. Vibration can and will eventually fail rubber pieces. The addition of TPM sensor can significantly increase the flexing. While some short rubber stems like TR412 may survive longer as they are only 0.88" long some valves can be 2.9" and all the HP stems are 1.27 or longer they may last longer.
IMO ALL rubber stems (TR and HP type should be replaced with full metal bolt in stems. With some alloy wheels with deep countersunk valve holes the Dill 902-w with its shoulder nut seems to be a good alternative. I have seen some other specialty stems used on Corvette wheels.
I would think that any of these painted or plated brass bolt in stems would work with any external TPM sensor. Obviously I have not tested all combinations but I think the above is reasonable.


"High pressure" stems may be more failure resistant but here is one that failed.
https://youtu.be/G-R3-MNaFB4


I am writing a post for my blog specifically to address different valve stems and TPM sensors. Should be live next week.

[Tireman9]

My blog post part 1 is live. It shows the flexibility of standard rubber stems and of HP rubber stems as well as an HP rubber stem that had failed when a TPMS sensor was applied. Part 2 next week will show the inner (brass) part of the two different rubber stems.

[majorairhead]

I have the TST 507 screw-on, originally had the OEM valve stems....the 507 caps definitely were hitting the rim. I quickly moved to metal stems, no worries since.

[djbar]

Just upgraded to Dill 902-W metal stems for my TST 507 Cap-type sensors. Cost was $34 (stems & labor) at Discount Tire. 45 min job.
Cheap insurance.

[Tireman9]

Found the bolt in metal valve VS 902W on eBay


Note the suffix "W" is important as there are a number of 902 valves.


These have the external "shoulder nut" not the internal double nuts.

[Salvagediver]

I called Dill to get a number for a distributor; Mohawk.

Call Mohawk at (800) 666-6464. Mohawk distributes from MA, GA, TX, and UT.

I paid $2.74 for each valve and ordered five...and I know this is crazy, but since I'm such a remarkably friendly old crank, I didn't pay any shipping.

[Ultraclassic]

Does anybody know of any inside the rim sensors like on our cars and trucks, that are compatible with TST?

[Tireman9]

Originally Posted by Ultraclassic

Does anybody know of any inside the rim sensors like on our cars and trucks, that are compatible with TST?

I have not seen any published guide for TPMS interchangeability across brands of vehicle or aftermarket supplier.


TST sells internal TPM sensors that work with their monitor, so you could just purchase a set of internal sensors.


What are you trying to do?

[Mollysdad]

I'm considering adding cap sensors to my truck.
I don't want it to show up as 8 total sensors because it takes too long to cycle around.
Instead, I'd call it "trailer 2" so I could switch between the two.
My truck has aluminum rims with internal sensors, but they only report low pressure. The stems actually look like the 902-W's because the rims have the same machined depression as the trailer.

[fran&frank]

You can buy the DIL VS902W valves from Discount Tire online for $3.00 a piece and free shipping direct to you. I just ordered them to go with my new Goodyear Endurance tires that I purchased from Sams Club and I'm getting installed next week. --Frank

[Tireman9]

Originally Posted by pmclemore

My tire shop added extensions to the valve stems. No biggie.

Pat

If they added the short 3/4" extensions all they did was move the TPM sensor out away from the wheel. Since you are running rubber stems they will bend and can eventually fail.


This video is from my RV Tire blog and shows the possible movement. TPM Sensors should not be used on "snap-in" rubber stems but only on bolt in stems.

[Tireman9]

Originally Posted by Rltports

I have been considering adding a TPMS. So am I correct that the tire needs to be balanced after you have installed a TST?

TPMS might affect balance by 1/4 OZ so you probably do not need to worry about r-balancing