The physics behind worn tires and braking distance

"It never rains in southern California." You never heard that? I have to drive in the rain maybe twice a year. It's always a good idea to avoid driving during the first hour of rain before the accumulation of oil gets washed away. In theory, anyway. Plain cold water never seems to get rid of much grease when I'm washing dishes...

Reply to
The Real Bev
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Interesting.

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Reply to
The Real Bev

It's a standard way of measuring the hardness of a material. The scale was invented by a guy named Shore in the 1920s. He also came up with a tool to measure it which is still used in undergraduate engineering classes today.

Interesting, my .signature is a misquote from Diva. I had been using it for nearly fifteen years before anyone pointed out to me that it was a misquote. By that time I figured it was too late to worry about it. Now it's been nearly thirty years that I have been using it on Usenet and I don't think people even notice it anymore.

I'm pleased to see it mentioned in another film. There's also one (a Nagra III as in Diva) in Blow Out.

--scott

Reply to
Scott Dorsey

Tyre design is a science that is not perfectly known. Engineers of race cars have to use the manufacturer's data and the guestimated track conditions.

A driver will test drive for many laps in order to get a 'feel' for the best responses.

Tyre grip is subject to change at any moment for many reasons.

The amount of tyre to toad contact is dependant on many things too, of which some are; inflation, wheel alignment, amount and type of tread, road surface material and, road surface evenness, springs and damper combination and rates, the speed around a bend which determines change in camber, and the steer amount and castor also adjust camber.

Any or all of these effect the heat generated in the tyre. As others have said, heat changes the characteristics of the tyre surface. It can go from hard to liquid in a very short moment of braking or cornering. However, given the skills of a driver, they may find the 'sweet spot' where the tyre is sticky.

Under stress, a tyre may break up in different ways dependent upon heat. A hard tyre may lose 'chunks' meaning less contact patch or, if heat rises to liquid form, begins to slide sideways increasing heat and subsequent loss of steering direction.

If the road undulates then the spring & damper combo may not be able to keep the tyre surface on the road at all times. for each moment one wheel is not in contact with the road it is tending to the outside of the bend. Skipping. This can happen at micro-levels. However, at micro-levels the car is going as fast as is possible without losing to much steering direction and it is this level that a driver will try to aim for. There for, you might not hear that horrid noise of screeching, which joy riders consider a skill but, the slightest little tyre squeal.

The amount of breaking also contributes to tyre wear and heat. Break parts, too have a 'sweet temperature' where deceleration is attained in the shortest distance. The heat from the brake assembly will contribute to the heat in the tyre but, more likely the heat the tyre can shed off.

So, as far as cornering is concerned, a 'fast' driver is someone who knows the 'feel' of all these factors. The tighter the steer and the faster you go the less likely you are to feel these critical moments. Crucially, the line you take through a corner makes the a difference to all these factors.

Your driving friend may well have a good sense of these things without the knowing. She can feel the car approaching the limits and drives within them. I'm not sure(these days) that I would like to test a car on mountain roads :-)

The brand and grade of the tyre is a small part in the art of driving.

...Ray.

Reply to
RayL12

I've driven the same road (always dry, a few times with chains) many times in my 88 Caddy and the previous 83 Sentra. I consider the squeal at a corner a sign that I've gone too fast at that particular point. I don't think I'm in danger of sliding out, but after a lifetime of frugality I just don't like the idea of wasting rubber. When I drove her car on the same road it was an absolute revelation. The car held the road silently at what I believe to be at least 15mph more than I was used to and I think I was driving -- in comparison to my friend -- conservatively. The acceleration (in spite of my ham-fisted shifting, it's been a while) itself was breathtaking, although I don't think the tires had anything to do with that. I wish I didn't NEED a Corolla -- I'd buy an S2000 in a heartbeat!

Yes.

Reply to
The Real Bev

2013. 17K miles. 16" alloy wheels, H tires.
Reply to
The Real Bev

Woah, Bev, don't go firing too much tech at me. Sorry if I gave the impression I knew more than I do. :-) And for most of the time, one car looks the same as another.

However, Simply looking at the pictures of the 2 designs, I can see that the S2000 is 'sporty' in design. It is probably tighter sprung and sitting slightly lower. The S2000 will roll, due to a lower centre of gravity less and, have better ground suction.

Less roll means the car needs less camber which, in turn, means more tyre contact on the straights.

It may also have faster rebound settings in the dampers which gets the tyre back to the surface a little faster which is a bonus during cornering and acceleration.

A way to measure how much corner slip the car makes is to use tape at the top centre of the steering wheel. Take the corner at a low speed and make a note of the tape angle. Then take it at speed and notice the difference. A car accelerates faster when all the wheels are pointing in the same direction so, the sooner you get the whole of the car pointing into the straight, the sooner you can unwind the steering and put your foot down.

Anyway, I only got out of bed to make a quick cup of tea. I'm going back to bed. Nite nite.

...Ray.

Reply to
RayL12

Sorry, that was just sort of the tail end of a thread and I was in a hurry. I bought a 2013 Corolla S with 17K miles (I'm ashamed to say that it was the first car I looked at -- I couldn't see a reason to NOT buy it!) and 16" alloy wheels with P205/55R16 89H tires. The paranoid who leased it even had it serviced more frequently than required -- 20K checkup/oil change was done at 13K, so I guess I'm good for a while :-)

I need to find out what kind of oil they actually used. I can't believe anybody in southern California uses 0-20 :-(

That's more anal than I'm interested in :-( The FEEL was fantastic!

Sleep tight...

Reply to
The Real Bev

Well if you run the Synthetic 0-20 W you get a 10,000mile or 1 year oil change interval. Personally every time I get a new buggy I change out all fluids to give me a known baseline. I also send out samples of the oils for testing. That way I know what oil, coolant and lubes were used and can start tracking from there.

Have fun with the new car...

Reply to
Steve W.

Oil that thin is intended for cold climates, which we definitely don't have. 10-30 is normal, but I'd been using 20-40 conventional when I changed my own oil. Is the thickness no longer an issue with synthetics? I bought a case of Mobil 1 at a divorce sale ("Here, take the whole thing for $2, that'll teach the bastard...") maybe 10 years ago but I've never used it. Still good?

I only drive the Caddy 3K-4K/year, mostly on the freeway, so I just change the oil (probably 10-30 bulk, whatever Pep Boys uses) once a year. It doesn't need top-ups and the oil looks pretty clean toward the end, although not 'clean'. I don't feel good about it, but good enough :-)

Carfax claims the dealer I bought it from, as well as the other dealer (several times) changed the oil; how much incentive does a dealership have to lie about stuff like that?

Fraught with anxiety. It's perfect now, all I can do is make it worse :-(

Well, not COMPLETELY perfect. The lumbar support (like they all have now) makes me bend a bit backward so I can't rest my upper body against the seat back, but I figure I can hang some sort of pillow from the top of the seat; and the instrument console is only illuminated when the real headlights are on, which is stupid. Not all designers are geniuses.

Not as stupid as the Caddy designer who put the useful tech information in a thing down in the middle of the dashboard two feet below the window line and DIM so that if you really want to see it you risk whatever you risk by bending over and looking away from the road for 5 or 10 seconds.

Reply to
The Real Bev

Buy Radial T/A tires from BF Goodrich at Tirerack.com

They had a soft compound when I bought them. Back in the 80's.

Talk to a Tire rack specialist on the phone first.

Reply to
geo pearl

The 2013 Corolla (17K miles) came with Goodyear Eagle H-speed tires that would look brand new even if they hadn't painted them with pretty shiny tire black stuff. Thus endeth the problem :-)

Reply to
The Real Bev

You can't "unadjust" it enough with the rocker switch on the side of the seat, behind the forward/back and seatback angle switches? (Owner's manual, pg 51).

You have Daytime Running Lights, correct? On most cars that just turns on the high-beam headlights at half brightness. I've seen WAY too many people flying along the highway in the middle of the night, DRLs so dim they can hardly see, and the back of their cars totally black, because they think "Well, the dash is lit up... that must mean my lights are on". The dash being dark reminds you to turn on the main headlights (and tail, side, license and dash) at night. (Owner's manual, pg 159).

Reply to
Sanity Clause

Oil that thin is what the company wants you to run because new engines have much tighter clearances and oil passages than engines from the 90s even. Run a thicker oil and you can easily damage parts of the engine. Long ago you would switch to a thinner oil for cold weather, these days the oils are MUCH better. I run a 5W 20 blend in the 03 Jeep, it's got

209756 on it at the moment, uses about 1/2 pint of oil in a 5000 mile change.

Oil should still be fine as long as it is sealed. BUT it may not meet the spec for that new engine.

Well, if you drive the new one that way you can easily go with a yearly change.

Not much, but it's just a check mark on the form. Plus remember that Carfax only reports things that go through a dealer or insurance claim. You can buy a car that has been pieced together from parts of 3 cars and if it was done by a small shop it won't show on the sheet.

The lumbar support should be adjustable.

Reply to
Steve W.

Yeah they seem to love tire shine, Even when rubber isn't supposed to be glossy...

Reply to
Steve W.

This has manual seats. I can tilt the back more forward, and probably will, but i'd rather just dig out some of the lumbar padding -- my back is kind of weird. Not going to do that, of course, I'll just complain :-(

In fact, there's a transparent cover over the whole thing which reflects badly. For one thing, it's curved and distorts the upper part of the display. If I were taller (or the seat would actually rise up rather than just tilting to make my knees higher) that would be less of a problem. The tiny liquid crystal information displays are totally useless for those of us in the bifocal generation who have to move our heads too far forward to actually read them, providing there's enough light AND no annoying reflections.

I't like the actual mechanicals of the car were designed by experts, who then left the user interface to the interns :-( It's not bad enough to have disqualified the car (I didn't even look while I was test driving, I figured anything would be OK because I'm not real picky; I was kind of wrong.) but bad enough to bitch about.

I think they're separate. There are two headlights on each side, one bigger than the other, and the turn-signal light. Down near the bottom is another white light, which I assume is the fog light. Those used be yellow, but I guess modern technology has found that white is better. Or cheaper. Too much trouble to hop in and out of the car etc. Maybe if I'm in a convenient place at night pointing at a wall...

When only motorcycles had DRL they were actually useful. With their proliferation to cars, not so much. Just more visual clutter.

Duh. I'm more likely to need a louder bell to remind me to turn the headlights off during the day. I've actually driven on the freeway at night with NO lights and then been shocked to find that I was doing so. Once only, but still.

The 88 Caddy was capable of turning off the headlights a few minutes after you turned off the engine, but I never trusted it; when my mom had the car it didn't work once and ran her battery down. We couldn't jump it because there was a cabinet in her carport overhanging the hood AND we couldn't put it in N with a dead battery so I could push it out. The AAA guy showed us the magic switch under the right fender, but we never needed to use it again.

It seems stupid to turn on the headlights just so I can see the instrument panel better. It can't help but wear out the battery sooner, right?

Reply to
The Real Bev

Probably more than that -- misspellings, etc.

It will show up as a 'salvage' car on the pink slip, though, right? Unless that's just a California thing and/or cheating is easy, of course. A kid-friend bought a really nice salvaged Mustang that he invested a lot of money in for dragstrip purposes. It broke in half. Not good. The fact that we told him beforehand to NEVER buy a salvaged car didn't make it any better.

The Carfax site looks like it has a place to add additional information even if you're just an owner. Didn't try, though.

Not with manual seats.

Reply to
The Real Bev

It won't unless the VIN they use was actually declared as totaled AND the state records it as such. There are a lot of vehicles out there that were "totaled" but not reported as such. I've bought a few and rebuilt them myself. Done correctly they are as good as factory, sadly there are a lot more folks who stick them together and don't do it correctly...

I'll have to look at one, but the adjustment may not be "user friendly".

Reply to
Steve W.

Perhaps wrecking yards are required to do that. A normal pink slip is no guarantee, of course, but a salvage title is pretty definite -- a trout in the milk, as it were :-)

I'm right about the lumbar thing, but I was wrong about the seat height adjustment, I just wasn't pushing hard enough. It does raise the height of the seat, which is definitely a good thing. I never feel comfy brute-forcing things when I'm totally unsure of how much force is required.

Reply to
The Real Bev

What? The InterWeb lied?!?!? One no-longer-trusted site said the S model got power seats.

Then I found this:

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"Fabric-trimmed front seats; 8-way power-adjustable driver?s seat;...." But, only in the LE model, and only as part of some "package". :(

Reply to
Sanity Clause

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