Bill Pemberton
0ld Ford Automotive Racing Terror
What pressure are you starting with?
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Depends on the tire and how many laps I’ll be running. In an ideal circumstance, I’ll be able to get up to temp quickly and have a fast setup that lasts a full session. Not easy.What pressure are you starting with?
Sounds to me like you are doing fine and it will often take one or two laps to get to a good temp, but I started at 25-26 lbs when I ran Cup 2s. I do make sure on Lap 1 ( especially when I was running W2W ) to drag the brakes plenty as the heat from the brakes will translate into getting some warmth into the tire early, but honestly if you are running long sessions few tires will stay completely the same during the entire term. That is part of the fun drama of racing, being able to adapt to changing conditions , whether it is the track, the weather , or the tires. I know I found Cup 2s getting greasy toward the end of a session, but then I have seen this with practically every tire I have run on. Sure, some stay more stable for longer periods but some of the ones that see almost no change often are also slow.
I guess I would not be that concerned ,it sounds like you have a decent handle on things, but you also will likely see differences at various tracks. Some heat your tires up faster than others, many heat up one side more than the other due to the number of turns or load and as you noted you just want everything ---- well , you can't have it all, ha, but you are analyzing things to get the best overall usage imho.
Kind of hard to say, what you should see is conistency, You can actually see each specific tire rise the same amount every session. instead of 6 psi one session, 10 the next, or of humidity is a thing, as much as 15 or more psi. So you can expect the same amount of pressure rise in say, the right rear 6 psi every time, same with the rest. (depending on the track, it might not be the same as the RR, it could be more of less, but the same each time)This lets you set the pressure consistently and because air pressure is spring rate, tune the car better.So if I have been seeing pressure gains in the 8 lb range, what should I expect from dehumidified air?
This is the key. You'll be able to set your cold pressures and have confidence that when the tires warm up they'll be at the hot pressures you want.what you should see is conistency
Not sure I'd trust this in a motorsports/HPDE venue (high speeds & curb cutting). It looks like the valve stem cap contains the sensor/sender/battery unit, so it needs to push the Schrader valve in to be able to read the pressure. Which means if the cap loosens, you start losing tire pressure. And the sensor/sender/battery unit in the cap needs to weigh more than a standard cap, which can put more g-load strain on the valve stem at high wheel speeds - probably not a concern with a metal valve stem, though galvanic corrosion may come into play with a metal valve stem. Then again, I like to game out worst-case scenarios. This might be fine.an in-car tire pressure monitoring system, maybe something like this?
I removed the oem tpms sensors on my track wheels because the plastic/rubber oem valve stems were breaking under hard track use. Metal stems fixed that problem but now I don't have tpms on track. Similar to you, my 2011 GT tpms doesn't give specific readouts. You make good points about potential problems, although I suppose if I started losing pressure on track at least I would know about it lol.Not sure I'd trust this in a motorsports/HPDE venue (high speeds & curb cutting). It looks like the valve stem cap contains the sensor/sender/battery unit, so it needs to push the Schrader valve in to be able to read the pressure. Which means if the cap loosens, you start losing tire pressure. And the sensor/sender/battery unit in the cap needs to weigh more than a standard cap, which can put more g-load strain on the valve stem at high wheel speeds - probably not a concern with a metal valve stem, though galvanic corrosion may come into play with a metal valve stem. Then again, I like to game out worst-case scenarios. This might be fine.
However, if you already have TPMS sensors installed for the built-in Ford system (and you don't have a built-in PSI readout - my 2013 Boss only says "OK"), you might be able to tap into the CAN-BUS data with something like ForScan on your phone or a tablet and build a real-time dashboard.