As is my routine, I always remove the Pressure Pro sensors and adjust the tire pressure with a manual gauge before a trip. I did that today and found some wheel damage near one of the Pressure Pro sensors. See the pic below. This is the outside rear wheel on the passenger side. The valve stem extension from the inner tire sticks out enough to attach the sensor, but when the tire is turning, I'm sure the sensor rests on the outside wheel. I have always thought that the sensor would wear and not the wheel. But that does not seem to be the case. The damaged spot #1 is obviously from the sensor. But I am not sure how the the #2 area was damaged since the sensor is behind the sensor point of contact. Maybe it was from a shorter extension prior to our owning the coach.
Question.... Do you think this sort of damage is serious enough to consider replacing the wheel? The #1 area seems pretty superficial, but #2 is deeper (difficult to measure). Thanks in advance for any input.
Interesting George, I have to guess you do not use the rubber insert on the outer rim to hold the inner wheel valve stem centered. Maybe that is one purpose for the insert, to support the stem, on my wheels, I do not have extensions and do not have the issue with the PP, on the other hand I have not looked recently.
Dave M
Yes, the rubber insert is there. You can see it in the pic. It helps, but does not keep the sensor off the wheel. I have bent the sensor up a bit to increase the clearance, but it can't bend enough to keep it away completely and still screw in the extension.
I had not thought about not using the extension. I could do that and temporarily add them to add air and then screw the sensor directly on the valve stem of the inside wheel, but that would be a pain.
George,
I am trying to picture how a plastic sensor casing could gouge out aluminum???
And, if the gouges aren't too deep, no worries. If a question on this, go by any large truck tire store and have them look at it-- they work on hundreds of aluminum rims a month.
OK, Now I get the pix, I also had the identical happening when using the extensions, I now have the one piece stem, long, and got them bent into the center of the hole of the outside wheel, then installed the rubber insert, Bingo, no more issues and there is plenty clearance between the PP and rim. I do not care for em extensions, just more chances for em leaks.
Dave M
We have a similar problem wth Pressure Pro sensor wearing flat on one side with also a wear spot in the aluminum wheel.
Curbside inside dual wheel valve stem must be angled, because streetside sensor is far from wheel with no indication of sensor / wheel collisions.
Here is a photo of our solution that has been in place for several years.
All,
Another option:
Not liking to take unnecessary risks by continuing with the inner dual extensions (and rubber donuts) and not being able to find good quality long valve stems for the inner dual wheels (at least at a reasonable price - good quality long valve stems can be purchased for upwards of $120 a pair) I decided to do what many truck owners do. I eliminated the extensions, installed good quality "shorty" valve stems on both the inner and outer duals and I use a couple of special tools to install and remove the (inner dual) tire stem caps and the PP senders:
1. A 15" Valve Pal valve cap installation "stick" (about $10 plus S&H on the internet). e.g.
http://www.truckdog.com/store/Trucks___Trailers___Trucker_Exterior___Tire___Air_Accessories___ValvePal__15__ValvePal_Original_Valve_Cap_Removal_Install_Tool___VP15C?partnerid=googlebase&gclid=CNy1sJ-e8LECFcHd4Aodaj8AHw
2. A homemade PP TPMS sender installation tool. (PP makes one for about $5.00 plus S&H as well.)
I had posted these pictures about a year ago and the system still works great for me.
One does have to be limber enough to get one's eyes on the inner dual valve stem through the Alcoa outer dual access hole.
Why take the chance on extensions when this simple solution works so well?
Neal
Neal... What a great idea! Thanks. Wish I had paid attention last year!
Just one question.... how do you put teflon tape on the valve stem? Probably not, right? So do you use anything else to ensure a good seal?
George
When dealing with my tires and wheels, I genereally do not deal with junk (exception PP) and contraptions.
My long inner stems cost $15.00 each, and solved the issue for me.
I have had bad experience with the inner wheel short stems and bending of the valve core stem, slow leak and no joy.
Need to make sure the inner stem is EXACTLY positioned so it is correctly centered / pointed when the outer wheel is installed and you have a perfect positioning or you will sooner or later bend the core stem from either adding or checking the pressure.
Also, you have two types of gauges and air chucks, either angled or straight, sooner or later you might need to add air and your setup for a straight in type and only have a hose with the angled air chuck, you will most likely damage the core. Now you have to pick and choose where you can get air from, more joy than I need.
Like the old saying "Been there & Done that"
We all do what works for us. ;D
Joy
Dave M
I decided to try Barry's suggestion and got some 1.25" vinyl tubing from an Ace Hardware in Asheville, NC before we drove to Knoxville, TN today. This size provides a tight fitting cover which is relatively easy to cut. I didn't use any adhesive to hold it in place... just a pressure fit. Stayed in place on the trip over. Wish I had done this sooner. See pic below.
Steve commented that if it's polycarbonate, it's harder than aluminum.
Agree on the plastic marring the rim, then I woke up to the issues and solved them, all joy since as to positining with an inch between the PP and the rim.
Simple or make it difficult
Dave M
maybe I am being overly snesitive but would not putting the piece of plastic hose over the PP increase the weight too much as it revolves with the wheel, sort of like an out of balance tire??
and affecting the seal on stem?
John H
George,
Sorry.
We had company over the weekend and I haven't had a chance to get back to you before now.
I've always been of the school of thought that Teflon tape and air or hydraulic systems should never be mixed (a la the nuclear, aircraft, pneumatic and hydraulic controls industries). The "shards" or "strings" of Teflon, that are generated during assembly and disassembly of the threaded pieces, end up in the wrong places (e.g - on a valve stem core seating surface or in a hydraulic control valve seat or relief port). It may be that people routinely get away with the use of Teflon tape and lubricants around air and hydraulics without suffering the consequences, but I don't take the chance unless it's an absolute emergency situation.
Right, wrong or indifferent, the pressure sealing interface between the PP Sender and the valve stem, is the tiny "proprietary" gasket in the PP Sender and the END surface of the valve stem. If one is trying to seal the PP Sender threads to the valve stem threads, one is ignoring the ROOT CAUSE of a PP leak and one is just masking the symptoms with Teflon tape.
To get rid of the ROOT CAUSE of the leak, spend time inspecting/replacing the PP seating gasket or replace the PP Sender (never had to do that) or use a magnifying glass, looking for an imperfection on the end of the valve stem and polishing it away, or replace the valve stem.
I learned years ago that the inexpensive "angled" air chucks and gauges don't have "lead-in" alignment barrels and far too easily damage valve cores. Now, especially with our PP Senders and their sealing surface design, it's critical to use good quality chucks and gauges that have deep alignment barrels and good seating designs that ensure proper (gauge or chuck) alignment and ALSO minimize the chance of marring the end surface of the valve stem.
WRT "shorty" valve stems for inner duals, the ALCOA wheel ID information, stamped into the face of the wheel tells you, indirectly, what valve stem angle you need. I have verified that my inner dual
steel wheels are the same drop center angle and dimensions as my outer dual ALCOAs, which I would guess is the FT standard. In the below attached example, taken out of the ALCOA Owner's Manual (valid for all Alcoa wheels manufactured since 1977), the "22.5 X 8.25 15 degree DC" wheel ID information tells me that I have a "15 degree drop center". Therefore, to get a 90 degree angle, directly out through the outer dual access hole, I need a 75 degree bent stem. If I always change out to new stems with new tires, and I buy quality stems (from say ALCOA) and have them properly installed (clean and inspect the whole rim and all seating surfaces including the valve stem grommet seating surface, torque the new stem to the correct 9 to 11 ft-lbs torque), THEN the new stems will have silicone, high temperature sealing grommets that stand up well to the intended purpose. The short 2 inch ALCOA stems are incredibly rugged and are of very high quality. One would need a very heavy, long tool and LOT of destructive intent to bend or deform one. Although a little more expensive, I prefer this route rather than having inexpensive questionable stems "hand bent" by a tire tech. Those stems may have non-pedigreed rubber grommets that may not even be EPDM, much less high temperature silicone. If a tire store has quality stems with high quality materials and can show you the specifications, that's one thing. If, like many, they purchase based on low cost, mark them up triple and have little, if any, interest in the engineered quality of the valve stems, "but know they will work just fine based on their say so", then that's another thing altogether.
Anyway, hope this answers your questions on teflon tape and how to better ensure good PP seals.
My take on it, George, Dave
Neal
Thanks Neal. Good point on the PP sealing point and Teflon tape. However, it may be required on the Honda CRV. The valve assembly is made of aluminum and I read somewhere that there can be "dissimilar" metal problems if the sensor metal and the valve metal are not isolated from one another. But good point.
As for the weight of the sensor cover, another thing to think about John. It does add additional weight to the sensor, but as it turns, it would be forced against the wheel, thus I don't think it would torque the stem much, but it could certainly cause a balance problem. I did not notice anything, but would I? I don't think the tires were ever balanced with the sensors in place....same on the toad. Had the tires rotated recently and removed the sensors before I took it in.
Here are some numbers to put things in perspective. The sensor weighs 20 grams. The hose pad weighs 6 grams. That is less than an ounce for both. How much does a tire and wheel weigh?
Lil tid bit, 1 oz on a wheel assy rotating at 700 rpm is like 25 lb weight banging on your suspension 700 times a miunte. End of tid bit.
Dave M
Always have my wheels balanced with the PP sensors on the stems. Some "tire technicians" tell me it is not necessary. I tell them to "humor" me and watch them balance the tires. I did have issues with rubber valve stems and PP sensors on the wheel of a swivel wheel trailer I had. Small wheel, rubber stem, PP sensor and a very high RPM rate. Trust me a PP system was absolutely mandatory on that wheel, don't ask me how I know. Had metal stem installed end of problem. Maybe I am paranoid, but I always check and adjust the air pressure in my tires after a "tire technician" has replaced, repaired or otherwise messed with my air pressures.
Roland
Dave.... show me the numbers? Reference? Calculation? Hard to believe it would have that amount of impact. Wouldn't the PP sensor (and pad) be pressed against the side of the rim as it turns (centrifugal force). I don't see it banging as one is moving, but I must admit, I really don't know.
George, I have zero printed facts, just repeating what I was taught while attending the Bear Front End and Alignment School. Felt it was a good school, more to a front end than tire pressure.
You know how relieable schools are with info :o
Dave M
George, there is a chart somewhere I have seen giving those numbers and for all various wights too. It is amazing the loading on that one spot at various speeds.
John
OK !, For the wannabee's, know it all's, skeptics
Here is how this village idiot solved the issue of scuffing the rim with the PP.
?
Dave M
That's what ours look like, too. Unfortunately our TCI work order doesn't show OEM P/Ns so I can't tell exactly what valve stem they used on the inner duals.
-M
Michelle, This tire stem issue seems to have a big mystrey, My first was installed at Herman Tire, that is the one in the pix, later I went back for the other side stem, they said they never had such a stem, I told him a black man went into the shop, came out with a new one, then the saleman, went into the shop, pulled a couple bin drawers and found 1 new long stem. $15.00 and I am out the door, when I get to my favorite tire shop in Fl, they installed it along with all 6 wheels road balanced, $25.00 each, now a very smooth coach and NO EXTENSIONS.
You just gotta be lucky sometimes or speak words they understand.
Dave M
George,
The alternative, that I prefer to Teflon tape, to prevent brass-to-aluminum thread seizure problems, is to use an anti seize compound. I hesitate to call out a specific brand because with aluminum, it is critical to avoid using a copper based compound, or the aluminum threads may be damaged. I use "Si" #1200 Anti Seize, which I've had around for years (since aluminum head Corvette days):
Aluminum Based High Temperature Anti Seize Grease | Extreme Pressure Anti Seize (http://www.superior-industries.com/_1200_anti_seize_product_231.html#order)
I don't know where you can buy it. It never seems to dry out, harden or get crumbly. There are a number of other competing products available. You just need to ensure that the compound you use SPECIFICALLY addresses its safe use with aluminum to brass threaded connections.
WRT centrifugal force, Dave's essentially correct. His example is a little off in that the object (PP Sender) isn't at the outer radius of the wheel, but the force that the PP Sender is exerting (in trying to move away from the center of rotation) is surprisingly magnified. A one ounce PP will exert the equivalent of roughly 4.5 Lbf for our size wheels and tires.
Centrifugal Force = (Mass of PP Sender)(angular speed of sender, squared)(radius that sender is from the center of rotation)
For a 1 oz. sender, rotating at 504 RPM (22.5" wheels/tires at 60 MPH), at 10 " from the center of rotation, the centrifugal force = about 4.5 Lbf.
The sender isn't going to bounce much, but the two (PP Sender and ALCOA wheel) will sit there and "grind" away at each other as though the Sender weighs 4.5 Lbs.
Here a link to a handy calculator:
CalcTool: Centrifugal force calculator (http://www.calctool.org/CALC/phys/newtonian/centrifugal)
Best wishes,
Neal
g
Google,Dually valve stem kits
Dave.... Thanks for the explanation. Like your setup. Perfect. Neal, thanks too. Love the calculation. 4. 5 lbs is not a lot considering the total weight of the dual tire assembly and the forces involved. But not having it there would be better.... I have to admit that. But the question for me is, if a PP sensor is OK on the wheel by itself, will adding about 25% (i.e., going from 3.4 to 4.5 lbs) more weight for the pad cause a big problem?
I don't think the concern is the additional forces placed by the sensor or pad on the entire wheel assembly. But it would be good to watch what the additional forces do to the stem.
George,
No. Adding less than 25% to the PP Sensor, particularly where you have located it (to prevent further marring of the wheel) and where the stem can only move a very small amount before movement is limited by the wheel, isn't going to create new forces that you need to be concerned with. I don't know how rugged your stem is, so, as Benji said, look at it closely for a while until you become confident with it.
As common sense would tell you, the "fictitious" centrifugal force (it's a calculated force and not a measurable force) of the sensor at 60 MPH (4.5 lbf) is tiny in comparison to the 360 degree distributed centrifugal force of the wheel plus tire (integrated over 360 degrees, I would calculate our wheels plus tires to have on the order of 20,000 lbf or a 10 ton-force, distributed over 360 degrees, at 60 MPH). Also, the PP, being closer to the center of rotation, has proportionally less and less effect as MPH increases.
As a side topic;
This also leads to the logic of why the Centramatic type wheel balancers work so well. That wheel plus tire assembly that exerts 20,000 lbs of 360 degree centrifugal force at 60 MPH, only exerts 5 lbs of 360 degree centrifugal force at 10 MPH. It is possible to add physical weights that will balance any rotating unit at a given RPM, say at 60 MPH. But that same rotating unit will have somewhat different centrifugal forces at 50 MPH and 70 MPH, as compared to 60 MPH. Depending upon the nature of the imperfect weight distribution in a wheel plus tire combination (if it were perfect, one wouldn't need any artificial weights to balance the centrifugal forces), the Centramatics can show dramatic improvement over just physical weights . Within the Centramatics range of reactivity (a grossly imbalanced wheel/tire assembly would require some physical weights, but I have never seen that happen with Michelins) Centramatic technology allows the rotating assembly to continually and automatically adjust, over all rotational speeds, bringing perfect balance, not just at one speed but at all RPM.
Just an aside, FWIW,
Neal
Neal and others.. thanks for all the information and comments. Much appreciated.
Update.... the plastic tubing covers/pads (see above) on the PP sensors have stayed on now for about 800 miles of highway travel in 90 degree plus weather. I can see no movement.
I did report the wheel wear problem to Doug McMeen at Pressure Pro. Doug said he had not heard of this problem before and that the sensors are made of Xenoy plastic, which is a mix of plastics with one component being polycarbonate. Obviously, this plastic is very hard.
Another update to the Alcoa wheel damage caused by Pressure Pro sensors. I was able to contact someone at Alcoa and this is what he had to say.
"Unfortunately you cannot repair that type of issue. As for the wheel it might eventually crack out of that area resulting in air pressure loss.
Robert (Buddy) Bazzel
Sr. Quality Technician
Alcoa Wheel & Transportation Products
robert.bazzel@alcoa.com"
I plan to have the valve stem extensions replaced with a longer valve stem (similar to what Dave did) before we hit the road again.
Happy New Year everyone!
George
Regarding the use of Teflon tape. I just received the new O-ring seals for the Pressure Pro sending units. I have had a slow leak on one of my towed tires since I got the PP system two years ago. The new O-ring works great with no Teflon tape or anything. I'm not sure how long this O-ring seal system has been available but I think it will solve all of the leakage problems with pressure pro.
The cost was $15.00 including application tool from PP.
Pressure Pro sensors do not seal on threads and Teflon tape will not improve air seal, but may make it easier to remove sensor. Be sure to not let any pieces of Teflon tape get into PP sensor. I do not believe in using Teflon tape with Pressure Pro.
Pressure Pro sensors only seal against the top round surface of valve stem, so be sure it is smooth and even. New seals inside PP sensors will improve seal to top of valve stem.
Teflon tape is only used for tapered threads, like pipe thread, aka National Pipe Thread, NPT, FNPT, MNPT. Bolts, flare, compression and valve stems are not tapered and do not normally benefit from using Teflon tape or Teflon sealer.
Final update from me (hopefully). I removed the valve extensions from both inner wheels as Neal suggested. Also bought some tools to check the pressure without the extension and to add/remove a PP sensor, dill valve and valve cap when the PP sensor is off. The white tool that looks like a piece of PVC tubing is from Pressure Pro. It is made up of a piece of 3/4" schedule 40 tubing with a schedule 40 coupler on the end. The coupler fits tight on the PP sensor without modification. Total cost to make something like this must not be more than $0.50. PP should give these away... I won't say what I paid for it. But it does work. The top of the PP sensor is about 2.25" from the outer edge of the outside wheel. Close enough to make serving the tire easy. No more damage to the wheels from the inner tire sensor! Thanks Neal. Wish I had thought of this earlier.
George