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Ok... well Im sure that this topic has been discussed before... but Ima "Newbie"... so Ima ask anyways. Im looking into buying new rims... however is the low tire air pressure warning going to be affected (you know... the warning light you get when your tires are running low on air)? Does anyone know how it works?
 

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It won't be affected as long as you get it to the right tire pressure and zero it out. It is explained how to do this in the owner's manual.
 

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Mine did not go off after putting 245/40/17 on one set of wheels and then swapping the wheels again. I did not reset the TPMS.
 

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Originally posted by Dr. Isotope@Oct 17 2005, 05:02 PM
Same here. Went from the all OEM stuff to pretty much the same setup Zoltiz has, and have never seen the TPMS light. I think it's another Scion Myth.
I've had it go off on me when I was going 90mph on I-65 in Alabama
Can freak you out when you are at-speed (turns out that the tire was almost to max inflation rate).
 

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I'm on my third set of wheels/tires and I've never seen that lamp come on. The range was from stock 17s to 225/40/18 on 18x8.5s and then to a third set that's same size as stock.

-Ed
 

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Those are all very close in diameter though. I think before I mount my Nokians I'll let ten pounds out of one of my tires and drive around the block to see if it goes off.
 

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All the TPWS does is compare the rotating speed of each tire. If all 4 are low, it won't detect anything is wrong. When I got a nail in my tire, it came on to let me know that it was low.
 

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Exactly. If all the wheels are rotating at a similar enough rate, the sensor won't do anything. It has nothing to do with the diameter of the wheels, only their relative rotation rates.

Something to keep in mind about the tC, it uses virtual instrumentation for a number of functions. All four wheels are used to determine road speed, tire inflation, ABS function, Electronic Brake Force Distribution (brake proportioning), automatic transmission gear selection, VVTi, and Electronic Stability Control. One sensor on each wheel, but the signals get sent to various functions in the ECM. It's not like the old days where they used separate devices for all these things, they're doing it "better, faster, cheaper" by taking raw data from a single reliable source and using it for a wide range of vehicle control.

Peep this!
 

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I never imagined a small technical brief like that would have so many advertisements.

Or is that a clip out of a magazine?

-Ed
 

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Its from an SAE (Society of Automotive Engineers) brief. I still get excerpts and email newsletters from them, even though I haven't renewed my membership for a couple of years. The ads are hoping the engineers will incorporate their products in their next design, so they advertise pretty aggressively.
 

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Question, if i goto wider tires, can my dealer retune my computer to compansate for larger tires so my speedo wont be off?
 

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Wider tires won't affect your speedo. Only larger in diameter tires will do that. Sizes that are OK:

215/45/17
245/40/17
225/40/18
245/35/18
225/35/19

None of these are far enough off to make a significant difference.
 

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.2mph slow for a 245/40-17 is alot, when you get up to 80mph it'll read like 75mph...

anyways, will my dealer be able to adjust my computer or no?

and whats the widest tire i can go with no rub?? I was thinking of a 225 tires, ust next size up but i plan on dropping the car so I dont know if it'll rubb or not, i'm sticking with 17" wheel, no 18's too big for me...

Rob
 

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Originally posted by fiream@Oct 25 2005, 01:25 AM
.2mph slow for a 245/40-17 is alot, when you get up to 80mph it'll read like 75mph...
Not a math major, are we? With 245/40/17 when your speedo shows 80mph you will actually be going 80.3mph - that's 5 times closer to stock 17s than the optional 18s with 225/40/18 that come on tC and 3 times closer to stock size than 225/45/17 that you are looking at.
 

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Fix the tire with the nail in it.
 
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