No Stupid Questions Thread
 

I'm sure all of us have had questions about our cars that we feel like we should know the answer to but were too afraid to ask.

Ask here, you'll get made fun of but you might get an answer.


I'll go first. Are treadwear ratings linear or exponential? Can we quantify a difference between a 200TW tire and a 300TW tire and plot the grip?

No, you cannot. Treadwear ratings are not really subject to any huge scrutiny. For example, there are lots of 200tw tires on the market, they don't all have the same exact grip. As another example, there were quite a few 140tw tires that suddenly became 200tw tires when the SCCA mandated a minimum of 200tw for street class. And you'd think the tires got less grippy because of that, but they actually got stickier.

A tire with a tread wear rating of 300 is expected to last three times that of a tire rated 100.
The fun part is that the tire manufacturers rate the tires without any government monitoring or required testing methods. So one can do extensive testing and get a rating and anther could just send Joe out back and he says "ummmmmm about a 400" and both are the official ratings. Take the ratings with a grain of salt since they are not standardized.


Edit: Too slow Tripp beat me to it.

"Are treadwear ratings linear or exponential? Can we quantify a difference between a 200TW tire and a 300TW tire and plot the grip?"
Sorry I don't do much math, don't test tires, just know things from my own experiences.


To go along with what's been said by Tcoat:

I recently had Michelin Pilot Sport A/S 3+ tires on my car...for about 3000 miles. Their treadware is rated by Michelin at >500<. I got rid of them as they seemed so soft, like driving on marshmallows....though they gripped well.

I replaced them with OE style tires. Michelin Primacy HP, which Michelin rates at treadware of >240<. I got about 48,000 miles out of my original Primacy HP tires...and they are harder riding tires than the Pilot Sports...as they (the Primacys) are similar to summer tires, not soft rubber for all season capability (mud and snow).

I don't think the soft Pilot Sports would last anywhere near as long as the harder (and low rolling resistance) Primacy tires...so makes no sense to me how they rate these two models of tires for how long they are expected to last.

Note: both above model tires are rated 91W (good for 168mph). Both Temperature A. Pilot Sport A/S 3+ has traction AA (better). Primacy HP has traction A (lesser).

Back in the 80's, I'd read that treadwear ratings were *supposedly* somewhat accurate within a manufacturer's own lineup, but there's no standards/regulations which ensure a tire with, say, a 300TWR will be equivalent between brands A and B. I think, however, that even within a single brand, there's not much consistency any longer..

Here's mine: What exactly is happening in our cars to cause the crickets sound?

Fuel cavitation at certain temperatures and ethanol levels.
The 2017 changes to reduce the cam lift and reduce friction likely reduce the probability and severity of the cavitation. The fact that some 2017 owners still report that they have crickets under certain conditions means they didn't 100% eliminate it.


Or at least these are my thoughts on the subject based up reading extensive posts and at least a working knowledge of fuel systems. I could be totally wrong.

Wonder if a '17 cam could be swapped into an earlier motor to help with the crickets...? Or are there other changes to go along with the reduced lift?

I've heard that replacing the fuel pump with a my17 usually fixes it

So is the cricket/cavitation caused by a different pump design, or the higher lift from the earlier cam? Would the newer pump, which was intended to work with a lower lift cam, work correctly with a high lift cam? Or is the dealer swapping out the cam as well when replacing with a my17 pump?

They are just swapping out the pumps and they work fine. There have been mixed reviews on how effective it actually is for crickets though.

Why are Scion owners more likely to rebadge with a Toyota badge than a Subaru?

Can't tell if trolling or serious--but in the spirit of the thread, if serious: probably because they are drawn to the nostalgia of the AE86 or other past toyota sports cars and wish to pay homage to the spirit of the car instead of sport a badge that was slapped onto the car for marketing purposes.

The subaru badges (while resolving the issue of having to display a scion badge) would simply seem...out of place on an FRS (event though subaru and fuji heavy industries have their logos stamped all over inside the car / engine bay). It would honestly probably be just as (if not more awkward than) having Scion badges all over the car.

They may also just think the Toyota badges are more aesthetically appealing and clean (as is the case with me).