Tires/valve stems on new Scamp 13

[Robert Scallan]

Comming home from Matagorda Madness, had a lady on I10 point to my drivers side tire on the Scamp....pulled over and found valve stem to be leaking badly--traveled short distance to off ramp/gas staton and changed tire..............last night, saw that the other side of Iggy has a flat tire....will change it today and see if it's a valve stem problem....if so, perhaps all new Scamp owners should look to this as a potential problem.....more info will follow, i.e. type of tire etc............Bob

[Robert Scallan]

It,s 8 AM...I just checked out the other flat on my 2007 Scamp 13....it was a bad valve stem like the other....both leaking at the base of the valve stem where it connects to rim..........tires are Goodyear Marathon ST175/80 R13.......don't know if any other newer Scamps are having this trouble....I am replacing all three tire valve stems with heavy duty ones.............this is just an FYI for you good folks out there in Fiberglass Trailer land.

[Roger H]

Bob...

Thanks for that info. It'd sure be interesting to see how many "blowouts" are actually tire stem failures. I have taken to replacing all of my trailer tire valve stems with metal tire stems.

Roger

[Patrick M.]

I never had a problem with my Scamp stems from new-to-25,000 miles, but the recommendation over on the Casita forums is to go with metal stems. I've also never had a rubber stem problem in 40+ years of car driving, so I have to assume it is extremely rare to have a bad seal or failure, but I will probably go metal when my tires need replacing on the Casita.

[Byron Kinnaman]

In the last year or so I've seen a couple stem failures. One on a car and one on a trailer. Neither were mine.
I'm wondering if there's some quality issues?

[Robert Scallan]

In the last year or so I've seen a couple stem failures. One on a car and one on a trailer. Neither were mine.
I'm wondering if there's some quality issues?

Took all three tires to Goodyear.hd heavy duty,high speed,metal valve stems installed..as an FYI.the guy at Goodyear said that the stems form the factory should not be on these tires since the tires require 35 psi..........he said that the factory stems are not meant for that psi.don't know but I've got new ones now.

[Brian B-P]

...as an FYI.the guy at Goodyear said that the stems form the factory should not be on these tires since the tires require 35 psi..........he said that the factory stems are not meant for that psi.

Since there are essentially no "highway speed" tires (normal car, truck, and trailer tires) which have a rated inflation pressure any less than 35 PSI, it's hard to imagine anyone selling valves and stems which are not adequate at that pressure. Many trailer and light truck tires have much higher allowed (and required) inflation pressures to handle more load, in "ranges" going up in basically 15 PSI steps... 80 PSI (load range E) tires are pretty common on heavy pickups and light commercial vehicles.

I suppose it's possible someone put valve stems for a wheelbarrow tire in the trailer wheels... but I would hope Scamp wouldn't be doing that. Trailer tires are often sold already mounted on wheels - and thus including the valve - so the trailer manufacturer may have no idea what they are getting for valves.

[Brian B-P]

I have taken to replacing all of my trailer tire valve stems with metal tire stems.

... the recommendation over on the Casita forums is to go with metal stems.

Took all three tires to Goodyear.hd heavy duty,high speed,metal valve stems installed..

Although Roger, Patrick, and Robert probably already know this, there are metal stems... and there are metal-clad stems. Some rubber valve stems have a chromed metal sleeve over them just for appearance, as a "dress up" accessory; I can't see how those would be of much benefit. I think the intended product is an actual metal stem, with rubber seals, although rubber stems are certainly available which are intended for use at up to 100 PSI.

I've had valves leak, but never a stem; however, I have only ever had one set of tires operated continuously at more than 35 PSI... my winter van tires, which have ordinary rubber valve stems.
Real metal valve stem (left) versus metal-clad rubber valve stem (right):

[DanPatWork]

Traditionally the only suitable "high pressure" valve stem would be either a metal core pop in valve stem or a bolt in with rubber grommet. The bolt in stem is similar to those found in heavy truck wheel applications and is very durable. The pop in stem is also quite durable and is generally used in medium duty pickups such as 3/4 ton and 1 ton trucks. The standard "low pressure" valve stems come in many lengths and designs, and are available for just about all stem hole diameters. The "low pressure" stems are generally suitable for pressures up to 35 psi. Some of the "low pressure" stems are only suitable for up to 10 psi, and is would be very hard to identify the difference through outward appearance.

All valve stems are still subject to the same risks and problems. Road grit and road hazards can still damage the rubber seal enough to cause a leak. Rubber still breaks down over time due to exposure to the elements. It is highly recommended that any style valve stem be replaced at every tire change. For the price of a couple of bucks per wheel, the reduced risk of valve stem failure is worth it.

[Roger H]

Dan, the advantage to the all-metal stem is that it doesn't flex when servicing the air or checking the pressure. The rubber seals don't move, they just seal, unlike the all-rubber stems that flex when you touch them. Flex in old rubber can lead to cracking, and subsequent failure.

Roger

[DanPatWork]

Dan, the advantage to the all-metal stem is that it doesn't flex when servicing the air or checking the pressure. The rubber seals don't move, they just seal, unlike the all-rubber stems that flex when you touch them. Flex in old rubber can lead to cracking, and subsequent failure.
Roger

Good point Roger, I hadn't planned on going as far as I did and not mention those same things...

My personal preference for the last 15 years in valve stems is the pop in high pressure brass shank valves. I like the solid fixed stems as well, but in our fleet of buses I've seen them break when traveling through muddy roads, and rubbing against hidden object. The rubber pop in stems still flex, and I've had no stem leaks with these. On the flip side of that coin, I've seen the rubber stems get torn while traveling through thick snow and icy roads. I average a tire change on just about everything I own once every 2-3 years. So far no stem failures, with low pressure pop in in the cars, high pressure pop in in the suv and all trailers.

[Pete Dumbleton]

Since the top end of the low-pressure stems is 35 psi, it's right on the edge of 35 psi users and too low for folks who use higher
TPs in their tires, esp trailer tires. I prefer to have stuf like stems well inside their design limits in normal use, not out on the edges.

[Byron Kinnaman]

Since the top end of the low-pressure stems is 35 psi, it's right on the edge of 35 psi users and too low for folks who use higher
TPs in their tires, esp trailer tires. I prefer to have stuf like stems well inside their design limits in normal use, not out on the edges.

I thought the low pressure stems were rated for 65 psi. Guess I missed something.

[Pete Dumbleton]

The "low pressure" stems are generally suitable for pressures up to 35 psi. Some of the "low pressure" stems are only suitable for up to 10 psi, and is would be very hard to identify the difference through outward appearance.

I'm relying in part on Dan's post above, but I believe I looked this up some time ago. Even at 65psi, a 55psi tire would be closer than I'd like to see it. The 100psi stems make more sense to me, considering the cost.

I did just find this article which says 65psi, so I dunno for sure; if I'm wrong, it wouldn't be the first time for sure!

ON EDIT:

Here's a stem source posted on Yahoo Scampers showing 65 psi, so I guess 35 is wrong.

[Byron Kinnaman]

I'm relying in part on Dan's post above, but I believe I looked this up some time ago. Even at 65psi, a 55psi tire would be closer than I'd like to see it. The 100psi stems make more sense to me, considering the cost.

I did just find this article which says 65psi, so I dunno for sure; if I'm wrong, it wouldn't be the first time for sure!

ON EDIT:

Here's a stem source posted on Yahoo Scampers showing 65 psi, so I guess 35 is wrong.

Items that can be considered to be a safety factor when a failure occurs are usually tested to at least double the rated pressure. Even non-safety stuff is tested much higher than published specifications. An example I know of is brake lines for air brakes in trucks. A truck's air system is 120 psi, brake air lines are rated for 300 psi, we tested to 600 psi. My point is that even with a tire inflated to 55 psi you're probably a long ways from failure.

I don't know what the down side is of going to a higher rated stem, if there is any other than cost. Assuming that isn't any real down side, go to the higher rated if it will reduce concern.

My tires are rated at 35 psi max, so I'm not gonna worry.

[Brian B-P]

The supplier I almost randomly picked when looking for an illustration for my earlier post listed their low-pressure stems as good for 35 PSI, which makes perfect sense to me, since that is the maximum operating pressure of the majority of passenger car tires. I'm all not not running at the ragged edge, but on the other hand we're talking about a rated normal working pressure, not a "one more PSI and it will explode" failure point. I'm not worried about the valve stems in my cars, but I think this discussion is a good tip to ask about the stems when having higher pressure tires mounted.