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Monday, July 21, 2014

TPMS Batteries

Many have smartly made the move to add a Tire Pressure Monitor System to their RV. While TPMS will not eliminate 100% of the possibilities of having tire failure they can eliminate many "Blowouts" as they can provide warning of air loss. Many times giving the driver an opportunity to pull over in a safe location and to avoid destroying an otherwise potentially repairable tire.

One issue with TPMS is battery replacement and battery life. As we all know from personal experience it is almost impossible to accurately predict when a battery will "die". While we might not be able to predict the "when", there are steps that can be taken with external sensors to extend the life of the batteries and possibly prevent having a battery fail and leak and damage the sensor.

When I was shopping for an External Sensor TPMS to buy,  I selected TireTrakker. I used the selection criteria I outlined in THIS post.




 The user replaceable
 low cost batteries were a major consideration.

Now I am not a full timer so my RV is parked for weeks at a time and for months over the Winter here in Ohio. Now while the "Standby" mode of the sensor only draws 500nA so the "life" is not draining out very fast but there is still the potential for the battery to fail and corrosive chemicals to leak out and damaging the sensor. Remember your battery drain rate may be different.

Here is a suggestion.

Get one of those pill boxes and place a battery from your sensor in each section. I have six sensors so I have space for a new sensor battery as a back-up to the others.

Next label each sensor with the position it is associated with. This will eliminate the need to re-calibrate the sensors when you place them back on your RV.



This storage approach prevents the metal batteries from shorting out against each other too.



Tuesday, July 15, 2014

Can I change from ST to LT tires on my Trailer or 5ver? Part Two

In Part 1 we left off with having to do some calculation.

I will assume you have confirmed the actual individual tire loading and have moved some heavy items around to end up with a reasonable balance of loads,

I will also assume you still want to change from ST type to LT type tires which means you must increase the Load Range and or increase the tire size to get a load capacity in the LT to match or exceed the capacity of the OE ST type tires.

Now before we move on you need to realize that "LT" is a designation used here in the US and European and some Asian countries have what they call "Commercial" tires. These Commercial sizes do not start with LT or CO but will probably look like 7.00R15  or for metric sizes 205/75R16The "C" in this case is not the Load Range but stands for "Commercial". The Load Range will be identified as normal LR-C, LR-D etc or possibly with RL or XL for Reinforced or Extra Load. To make this post easier to read I will limit my comments to LT type tires. Just remember there are other options that may be better for those with 15" or 14" wheels that do not want to change rims.

NOTE: All of these letters and numbers are important when selecting a size so be sure you record them all when doing your research.

So on to step
#6 Dimensions. There are two key dimensions Outside Diameter or OD and Width. Now I am confident that we all understand OD but width can be a bit confusing. Depending on the wheel well contour the overall maximum width or "Section Width may be most important. Some tires may have a narrower clearance nearer the tread so they will need to do some actual measurements at a number of locations.
It may be easiest to use the dimensions for OD and Section published for your current tires and just do a confirmation with your tape measure. Remember tire "width" is not the same as tread width.

You need to be sure the tires NEVER contact any portion of the RV frame wheel well or bodywork. You should try to have equal or greater clearance with the new tires that you have on your original size.

7. The challenge
When moving from ST type to LT type you will need to move up in Load Range or up in Size or both.

Now comes the research to see what your options are
8. Knowing the target Load Capacity and the maximum OD and Section width, it's time to use the Internet to do some research. The objective is to find tires that meet your needs for the numbers and that are appropriate tread pattern. You certainly don't need Snow Tires or heavy traction tread pattern. I would suggest that the tread be identified for "All Position" or Steer for your trailer application.
You can go to web sites from large dealers such as Tire Rack, Pep Boys, WalMart, NTB, Discount Tire or similar. You might also just Google "Trailer Tire" + the name of a large city or town near your location.
Once on their web site find the various possible tires that meet your needs.

9. If you are increasing the Load Range with the associated increase in inflation you need to confirm the wheel can manage that higher inflation. The info may be marked on the back side of the wheel or you may need to contact the wheel seller or manufacturer or you may need to get different wheels if your OE seller doesn't know what the rating is for the OE wheels

10 Finally, as I have previously suggested in my post on "The Best Trailer Tire" you need to make your purchase decision not just on lowest price but need to consider the tire warranty, even if there is a Road Hazard Warranty. Also how easy will it be to get a replacement if your tire gets a sidewall cut or unrepairable puncture.

11. Last step:  After all this work we want to do a first class job. Some might want to say you can't change from ST type to LT type due to Federal Regulations. Well a friend Dave Gray has an excellent post just on this topic. He has even provided an example of what would be the appropriate label you should apply after making modifications to your RV.


I hope these two posts have helped you understand the steps, calculations, measurements and research needed to make such a change.