TPMS

[bob]

Has anyone found any particular brand of in tire TPMS sensor for the S550's TPMS better or more accurate than any other brand?

 

[blacksheep-1]

The TPMS sensors are always a little sketchy IMO, I would try to go with the factory Ford ones, however I have had success using the ones from American Muscle in my Gt500. If you are planning to "map" with them let me just say they are another tool in the box, no racer that I know of uses them for the absolute pressure adjustment. The reason is that your tire pressure around the track, and depending on the track configuration, length and duration of corners, due to all that, will very at least 3 to 4 psi. When we look at the numbers from the TPMS (and the Astin has to be read because we aren't allowed telemetry) we look for a "window" that the psi will stay in. Even with the Porsche, which had telemetry, depending on where on the track the car was, the pressure varied greatly, so it comes down to a point where you still do the temps and pressures on pit lane, and only reference the TPMS data.

 

[bob]

Thanks for your input! For me I was mainly curious. I figure the car has TPMS, I wonder what value it might be? 3-4PSI dynamic variation is a big amount. I never knew. I'm not even sure my 2019 updates the data view fast enough to see that happening in real time. I also question the accuracy of the sensors. One advantage of the pressure gauge is the same one is used to measure all your temps so the +/- error is the same.

 

[DaveW]

The TPMS sensors are always a little sketchy IMO, I would try to go with the factory Ford ones, however I have had success using the ones from American Muscle in my Gt500. If you are planning to "map" with them let me just say they are another tool in the box, no racer that I know of uses them for the absolute pressure adjustment. The reason is that your tire pressure around the track, and depending on the track configuration, length and duration of corners, due to all that, will very at least 3 to 4 psi. When we look at the numbers from the TPMS (and the Astin has to be read because we aren't allowed telemetry) we look for a "window" that the psi will stay in. Even with the Porsche, which had telemetry, depending on where on the track the car was, the pressure varied greatly, so it comes down to a point where you still do the temps and pressures on pit lane, and only reference the TPMS data.

Just curious, are you able to keep the sensors awake to read more often? I always thought they only polled every so often (which is how they make batteries in them last 7-10 years)

DaveW

 

[blacksheep-1]

With the competition stuff, yes, the info can be downloaded after the event, the pressures also display on the dash (in bar) and can be read over the radio, basically we say if it's between x and xx don't worry about it too much, if it's over xx, a couple of times, worry about it a little, if it goes under x.. worry about it a lot. the Porsche read constantly and it was visible on the telemetry in graph form, you get a long right hand corner and the left rear will go up 5 psi in some cases. I've never had to make pressure adjustments because of the TPMS feedback, it's just a reference. If the numbers are trending high in the window, I may pull a few tenths out, then run the projected temperature numbers for the race or next practice, and adjust to that.

 

[bob]

Rob,
how do you know or calculate minimum safe tire pressure?

 

[blacksheep-1]

Rob,
how do you know or calculate minimum safe tire pressure?

I'm sorry, I really cant go into that, but if I think that tire pressures are too low to let the car go out on, I put them in the sun to get the starting pressures up. This is why F1 uses tire warmers. We aren't allowed to do that so we have to set them outside. This really becomes an issue at Daytona in January when it can get into the 30s. This is one reason that I always say that a psi without a temp reference is useless.

 

[blacksheep-1]

Remember, it's always the hoy pressures that dictate the cold pressures, so whatever the hot pressures turn into with the tires cold, you're stuck with.

 

[bob]

I put them in the sun to get the starting pressures up. This really becomes an issue at Daytona in January when it can get into the 30s. This is one reason that I always say that a psi without a temp reference is useless.

The Sun! I seem to have an easier time obtaining my target hot pressures when my car sits outside in the paddock when I'm going buget and I'm paddocked out in the sun without even a canopy. There is ambient temp that effects the tire and the direct sunlight the black tire absorbs. The guy I travel race with is a garage lover and has got me addicted to the comfort of renting a garage which is always cooler and out of direct sunlight so the just before leaving for grid cold pressures going to rise just sitting on the grid and throw my hot pressures off unless I account for that too. I have not figured out how to do that. Then as the sun rises during the day the ambient changes plus often you get some direct sunlight into the garage so say the front tires are in direct sun and rears are not changing the pressures again from ambient and direct sunlight effects. All I can say is this is complicated and hard for me to wrap my head around and figure out a plan of attack. I have done things like car in garage take the pressure then roll car out and sit in sun for 15 mins and take the new pressure to guess at a delta for in and out of a garage. It's pretty ghetto but I guess it is a start.

 

[blacksheep-1]

You are exactly right, one of the issues I have is guys go to the garage and roll up the doors, the sunlight blows the rear tire pressures. I've finally got them to let me do pressures BEFORE rolling up any doors or tent curtains.