Reconciling Safe Tire Pressure with Pressure Pro Warning Limits

[BillO]

Having just invested a goodly sum in six new Michelin tires I want to protect that investment with a TPMS.  I've pretty much settled on the Pressure Pro system, but have a bit of concern over their warning limits.  I'd like to hear how others using the Pressure Pro deal with it, or if I'm making a mountain out of a mole hill.

My concern is best illustrated by example using my steer tires.  After weighing at all corners and checking the Michelin load/inflation tables the minimum pressure for my front tires is 95 psi.  Many people here (and also the Michelin tech rep I asked) suggest adding 5 psi to that for safety which brings tire pressure to a round 100 psi.

Now the first low pressure warning for Pressure Pro is at 12.5% below set point.  Consequently, that first indicator will be at 87.5 psi which is already 8% below minimum safe pressure and suggests to me an immediate slow down and pull over reflex. (I admit that this may be influenced by having an inner dual tire go essentially flat between stops with my old tires)

Do Pressure Pro users compensate for this by running slightly higher initial pressures (so the first warning is at or slightly above minimum pressure to provide time to react) or just run a little slower with less than minimum pressure until a safe, convenient stopping place comes up?

I'll be really interested in Pressure Pro users' perspectives.

Thanks,

Bill

[andyshane]

This is why I routinely scroll through all my tire pressures on the TPMS as part of my preflight.

I'm interested in your comment about adding 5psi. Not objecting to the practice, since it is definitely not a safety problem; but, the engineers came up with those table pressures to give (for one) optimum contact patch, and it seems odd that a company rep would advocate essentially reducing customers' traction (albeit a tiny amount)...

I'm fully prepared to add 5 or 10 psi if a tire ends up hotter than 120F at a safety check. But, to date, adhering to Michelin tables exactly has produced 120F running temp on the hottest days; so, no need to reduce temps with extra pressure. Industry consensus is that we should never let our tires go above 180F.

[wolfe10]

Agreed, no problem.

I plug in my Pressure Pro to check pressures in the morning before we leave and before the sun or other factors influence tire pressure.

On the road, Dianne occasionally scrolls through the tire pressures. But I would not want my alarm set too fine-- a cold morning could have a lot of them going off. Ran into that a couple of mornings in the desert SW this winter. 30 degrees at 7am, alarm going off on a tire or two. 60 degrees by the time we left, tire pressure back where it should be.

[rossboyer]

Regarding the manufacturer's tire charts at least for Goodyear having had all four corners weighed, the tire pressure needed to be 85 lbs in the rear duals and 85 in the front. At the bottom of the chart there was a footnote to add another 5 lbs for safety. Therefore, mine were 90 lbs rear and 90 lbs in the front. I was getting some cupping of the right front right tire at 45,000 miles. A Goodyear factory representative at Perry, GA convention stated that I should add another 5 lbs in all tires. Which resulted in 95 lbs rear and 95 lbs front. While you feel the road a little more from the front tires, the cupping problem was reduced.

I have PressurePro and cannot say that I am satisfied. The seals are not very good. If you travel south in the winter as I do, I end up adjusting tire pressure 4 times a year. The seals just will not hold up to being unscrewed and screwed back on. I have 7 of my 10 off right now to send back for rebuild. But from conversations with other salesmen of other systems, this problem is typical of all systems and they say I am tightening the sensors to tight. Wouldn't you tighten your sensors when in about 300 miles you loose 25 lbs or down to 75 lbs just sitting overnight?

[andyshane]

At the bottom of the chart there was a footnote to add another 5 lbs for safety. Therefore, mine were 90 lbs rear and 90 lbs in the front. I was getting some cupping of the right front right tire at 45,000 miles. A GoodYear factory representative at Perry, GA convention stated that I should add another 5 lbs in all tires.

I have PressurePro and cannot say that I am satisfied. The seals are not very good.

Thanks, Mr. B!

Maybe Michelin has rolled that value into their RV tables, eg the note is absent.

Indeed, lots of Goodyear owners have cupping problems. My next door neighb at the ABQ Balloon Fiesta in October showed me his Goodyears, marked cupping on his steering tires. His tires had half the miles on them I had on ours. It makes sense to add pressure for that: shifts the load towards the center of the tire.

'Sure be nice to know if cupping sufferers also had higher temps, before they upped the psi.

BTW, my tires need air no more frequently with TireTraker than without the sensors. I wonder if valve core depth has an effect, eg if the core is set just above the threshold for conveying pressure to the sensor it'd be less prone to leak... I don't know.

[BillO]

AndyShane,

I replied to your query about the 5psi safety factor in the other thread I started. Essentially, a margin for the nature of RVers to take on more things in shopping, etc. while on the go rather than a real tire issue.

I can appreciate the issue of reviewing a TPMS before starting out because I've been doing that with standard pressure gauge since I bought my coach. I also understand that temp extremes could cause some false triggering.

However, I am more interested in normal driving response to the alarms. From the responses above I'm sensing that a 12.5% drop in tire pressure is no cause to immediately pull to the shoulder but that I should just be planning to slow down and look for a convenient stopping spot to check things out.

[wolfe10]

I have PressurePro and cannot say that I am satisfied. The seals are not very good. If you travel south in the winter as I do, I end up adjusting tire pressure 4 times a year. The seals just will not hold up to being unscrewed and screwed back on. I have 7 of my 10 off right now to send back for rebuild.

I took the liberty of of forwarding this thread to PressurePro. Here is the e-mailed I got back:

Here's a quick explanation about our seals. If there's anything else you have questions on or would like assistance in explaining just let us know.

PressurePro seals are designed to hold up to multiple installations over many years. The seals are made out of NBR, the same material used for most o-rings. As with any rubber seal, some care must be taken to ensure seal integrity. Think about changing your oil, if you screw on the oil filter too tight, you can damage the seal and leak! The same applies for PressurePro Sensor seals. Since valve stems can become rough and worn after many years of use, you don't want to over-tighten and cut into the rubber seal.

In the off chance that you do experience a leak, PressurePro seals are very easy to replace. If you aren't comfortable with installing the seals yourself, you can always send your Sensors back in to have the seals replaced and the Sensors tested. PressurePro remains the leaders in TPMS and continues to be 110% committed to not only providing the best, American Made, product available, but also in backing those systems up with the market’s best customer service.

PressurePro replacement seals are available in packs of 10 for $5, including shipping and handling. PressurePro recommends the use of a 3/16" hex driver for seal insertion. If needed, a hex driver and 10 seals is $12 + s&h. If you have this size hex driver, just make sure that it fits inside of the sensor without scraping the threads. Our drivers have been machined to make sure of a proper fit.

Installation is very simple. You place the seal on the top of the hex driver, with the dimpled side down. Slightly wet the edges of the seal, to aid insertion. Then press the Sensor over the hex driver so that the seal is pushed into the brass. Avoid over-pressing, as the seal may not seat correctly. Always perform a bubble test around sensors after installation.

If you prefer, PressurePro will replace seals in our office. Seals are covered under the one year warranty, otherwise there is a $1 charge per sensor. This covers the new seal, leak testing and a quick test of the sensor itself, including signal strength.