Sorry: NPC - '95 Lexus ES300, but I know y'all will give excellent advice

Want to put 195/65 R15 on instead of 205/65 R15 and am told that car will fail Maine inspection because it has anti-lock brakes and those 12mm in circumference difference will negate effectiveness?

914's do not have antilock brakes...

Is THAT why I almost rear-ended that semi on I-95 yesterday???? I thought it was the dinky 165R15 - Kumho's cheapest.

Hi Rich

You could move to another state like MN. We don't have inspections.

i'll be following this thread...

i plan to mount 205-50's instead of 215-60's on the Subie.
i know the AWD requires identical tires (circumfrence) but i hadn't heard of (or thought of) an ABS issue.

I could certainly see issue with AWD or Anti-Lock brakes if you only did 2 tires of different size, but not all 4.

ABS will not care what wheel size you use, as long as they're all the same (assuming 4 channel ABS). There are a host of other reasons not to change tire size/type, but the ABS module will not be a problem.

I don't see it being a problem. I put 195 snows on my GTi and have stock size 205's for summer driving. The ABS works just fine especially in the winter.

ABS just detects when a wheel locks up and release pressure just enough until the wheel starts spinning again. Even if you put different sizes front and rear the system will still detect lockup and release pressure accordingly. It may just have to work a bit harder.

I don't trust tire salesmen. I once wanted to buy S rated tires for a VW fox that I had. He told me that since it was designed for H rated tires if I put S rated one on it I would skid out and crash. I asked him is that what the S stands for?? Skidout??

I can vouch that in NJ you will not fail inspection for a different tire size. I doubt its like that in maine either, how could you account for people changing the rims on a car? Hopefully its not illegal to roll on the dubs in maine

QUOTE (rhcb914 @ Dec 8 2005, 07:01 AM)

ABS just detects when a wheel locks up and release pressure just enough until the wheel starts spinning again. Even if you put different sizes front and rear the system will still detect lockup and release pressure accordingly. It may just have to work a bit harder.

More sophisticated ABS systems (4 channel ABS,... many cars in the last 10-15 years) measure wheel RPM to determine if a tire has low pressure. Therefore if your car has this system it will always tell you that you have low tire pressure if you run different tire sizes.

I'd guess that your Lexus uses ABS to measure wheel rpm.

In these days of ABS, IVD (intereactive vehicle dynamics) and RSC (roll stability control), you're taking a big risk by changing tires from the tire that the vehicle was developed on.

Keep this in mind. New 195/65's will be about the same diameter as worn out 205/65's. That's how small the difference is. And tires also vary from mfg to mfg. So it is more than likely that a different brand of 205/65's could vary in diameter even more than the theoritical difference between 195 and 205.

Can't imagine it could cause any sort of problem as long as you change all 4.

Of course, whether or not it causes a problem has nothing to do with whether or not you will pass inspection. If 'correct size' tires is a checklist item for the inspection and you don't have the 'correct size', you will fail.

Demick

QUOTE (rick 918-S @ Dec 8 2005, 08:02 AM)

You could move to another state like MN. We don't have inspections.

same thing in KY...

You should see some of the genius ways people hold thier cars together....duct tape, wire, or after that painful fenderbender the parts are just left on the car to drag around.

I especially like when people dont take care of thier cars, and the muffler droops closer and closer to the ground until...LIGHT SPARKS!

b

QUOTE (bd1308 @ Dec 8 2005, 11:53 AM)

QUOTE (rick 918-S @ Dec 8 2005, 08:02 AM) You could move to another state like MN. We don't have inspections. same thing in KY... You should see some of the genius ways people hold thier cars together....duct tape, wire, or after that painful fenderbender the parts are just left on the car to drag around. I especially like when people dont take care of thier cars, and the muffler droops closer and closer to the ground until...LIGHT SPARKS! b

Also true for Indiana -- and I imagine that if this state ever did start inspecting cars, at least 50% of the population would be car less judging by all the POS junkers on the roads here. Probably kill the last little bit of blue collar economic vitality left...tough on the migrant workers too...

But then I wouldn't be dodging mufflers, bumpers, and body panels that are routinely falling off all those junkers. It'd also get alot of those d*mn POS monster trucks off the road too, make it much safer to drive the teener.

But back on topic -- if you are really worried about a fault with the Lexus ABS system, why not talk to your local Lexus specialist and ask if it will make a difference. And if the problem is instead with the State's inspection checklist, file a complaint with your government representative. Maybe in ten or twenty years, something will be done about it. At least with the Lexus, you know it will probably still be road worthy then, as long as you can still buy gasoline for it...

QUOTE (groot @ Dec 8 2005, 07:44 AM)

QUOTE (rhcb914 @ Dec 8 2005, 07:01 AM) ABS just detects when a wheel locks up and release pressure just enough until the wheel starts spinning again. Even if you put different sizes front and rear the system will still detect lockup and release pressure accordingly.  It may just have to work a bit harder. More sophisticated ABS systems (4 channel ABS,... many cars in the last 10-15 years) measure wheel RPM to determine if a tire has low pressure. Therefore if your car has this system it will always tell you that you have low tire pressure if you run different tire sizes. I'd guess that your Lexus uses ABS to measure wheel rpm. In these days of ABS, IVD (intereactive vehicle dynamics) and RSC (roll stability control), you're taking a big risk by changing tires from the tire that the vehicle was developed on.

The way the low tire warning systems (ford for sure) is by measuring a prolonged difference in tire speed, via the ABS sensors. If one wheel of the 4 reads 32 rps, and the rest only read 31 rps, there is a low tire (and an idiot light). If all the tires are the same size, you should be fine.

Having said that, i agree there has been a lot of time and $$$ invested by toyota to make sure that lexus is safe and operates properly w/ the tires that came on it. For a street car, i advise sticking w/ a factory offered tire (size, brand, specific tire) unless there is a damned good reason to choose otherwise.

BJH

People are missing the point. THIS IS MAINE! They don't even know what a Lex-us is anyway. Shoot they're just happy with indoor plumbing. (ay-ah, I'm a former Main-ah)

Bruce,
Bite the bullet an buy the correct size tire. If the price is an issue, search for a tire in the correct size that fits the budget.

PS, hows the drive to work this morning?

QUOTE (Crazyhippy @ Dec 8 2005, 10:01 PM)

Having said that, i agree there has been a lot of time and $$$ invested by toyota to make sure that lexus is safe and operates properly w/ the tires that came on it. For a street car, i advise sticking w/ a factory offered tire (size, brand, specific tire) unless there is a damned good reason to choose otherwise.

My point exactly. I spent a moment up on the outriggers yesterday working on a damper tuning project. We use outriggers to keep the vehicle from flipping over. I was told the inside tires were 2 feet off the ground. I set it down nice and gentle like and drove off the handling pad.

Needless to say, we won't be using that damper tuning in production.

Please correct me if I'm wrong. I've been married seven years, I'm used to all the correction....what was that honey? Oh yeah....married eight years.

As I understood it, a 195/65 R 15 code is broken down to indicate a tire with a tread width of 195mm, a sidewall height of 65mm designed to fit a 15 inch rim, right?

So the circumference of the tire would be calculated using solely the rim diameter and the sidewall height, right? So roughly speaking...

...breaking out the ol' calculator...carry the one...

Circumference = PI x d.
d = diameter which would equal 15inches for the rim + 65mm for the sidewall on the bottom + 65mm for the sidewall on the top
d = 511mm (about 20 inches)....that sounds about right.
Circumference = 1605mm (about 63 inches....again, sounds about right)

So since the 195 and 205 measurement don't come into play anywhere here, a 205/65 R15 tire and a 195/65 R15 tire should have the same circumference, the 205 will just have more rubber gripping the road. So they should both spin just as fast.

Now, the extra rubber gripping the road would mean more friction, so the 205 might technically stop quicker, but one might think that would be even more harsh on the ABS than the thinner 195 tire.



Also, while it is true that the cars are tested extensively on the tires they leave the factory with, I would be very surprised if the tire choice is not heavily influenced by whatever deal the tire manufacturers are willing to cut the car manufacturer. I'm sure they have an idea of what class tire they want, and then find a good deal on a tire in that class. There are lots of ratings for tires (noise/load/speed/weather/etc) to take into consideration when selecting a new set, but I don't at all feel obligated by loyalty or safety to stick with the OEM tires.

Besides, tire manufacturers are updating their tire lineup all the time. Can you even get tires that were OEM on a car made 4 or 5 years ago?

Keep in mind, if the car is a 914LE, you MUST use OEM tires, else be branded an idiot....

QUOTE (Pnambic @ Dec 9 2005, 04:05 PM)

As I understood it, a 195/65 R 15 code is broken down to indicate a tire with a tread width of 195mm, a sidewall height of 65mm designed to fit a 15 inch rim, right?

sorry, you are wrong...

the "65" is the "aspect ratio" number. that number is the percentage of the treadwidth that the sidewall measures.

if unspecified, as it is with our original "165-15" tires, it's somewhere in the 78-80% range (varies by manufacturer...)

so a "165-65" aspect ratio tire has a sidewall 65% of 165mm or 107.25 mm. its approximate diameter (not corrected for compression reducing the effective rolling radius) is therefore 15" + 107.25mm*2.

Thanks Rich. I was wondering why my 225-50-16 tires looks so much different than the old 195-65-15s. I thought it was just my eyes playing tricks on me.

QUOTE (Pnambic @ Dec 9 2005, 12:05 PM)

Also, while it is true that the cars are tested extensively on the tires they leave the factory with, I would be very surprised if the tire choice is not heavily influenced by whatever deal the tire manufacturers are willing to cut the car manufacturer. I'm sure they have an idea of what class tire they want, and then find a good deal on a tire in that class. There are lots of ratings for tires (noise/load/speed/weather/etc) to take into consideration when selecting a new set, but I don't at all feel obligated by loyalty or safety to stick with the OEM tires.

While this is true, it's a bit more complicated than that. See, the tire manufacturers make deals with the OEMs, and submit up to 10 different tires for the OEMs to test. And they're always a compromise. While tires can be built to focus on different attributes, you really can only get 2 of those attributes since the attributes work against each other (fuel economy and NVH, or snow and wet handling, steering precision and NVH, etc). So, you look for the best mix and tune around the tire.

Picking a tire with slightly more grip on a passenger car can lead to a debead or rim strike in an emergency situation. We tested a competitive vehicle last week that debeaded it's right rear tire during the tire warm-up session. Scary stuff. So, the point is not all OEMs are as thorough as we are.

Being that your car is a 95 I would not worry about changing tire sizes. Most cars of that vintage use standard wheel speed sensors. I would check with the dealer but I doubt you would see any problems. I would drop to a 60 series side wall. The difference would be minimal.

Check with your dealer or hit www.lextrem.com and see if you can find an answer there.

QUOTE (groot @ Dec 10 2005, 11:18 AM)

QUOTE (Pnambic @ Dec 9 2005, 12:05 PM) Also, while it is true that the cars are tested extensively on the tires they leave the factory with, I would be very surprised if the tire choice is not heavily influenced by whatever deal the tire manufacturers are willing to cut the car manufacturer.  I'm sure they have an idea of what class tire they want, and then find a good deal on a tire in that class.  There are lots of ratings for tires (noise/load/speed/weather/etc) to take into consideration when selecting a new set, but I don't at all feel obligated by loyalty or safety to stick with the OEM tires.   While this is true, it's a bit more complicated than that. See, the tire manufacturers make deals with the OEMs, and submit up to 10 different tires for the OEMs to test. And they're always a compromise. While tires can be built to focus on different attributes, you really can only get 2 of those attributes since the attributes work against each other (fuel economy and NVH, or snow and wet handling, steering precision and NVH, etc). So, you look for the best mix and tune around the tire. Picking a tire with slightly more grip on a passenger car can lead to a debead or rim strike in an emergency situation. We tested a competitive vehicle last week that debeaded it's right rear tire during the tire warm-up session. Scary stuff. So, the point is not all OEMs are as thorough as we are.

You managed to actually debead a tire? In all my years and numerous stupid stunts (and riding with DJM914-6 and his crazy driving), I've never heard of that. Even my cheap-a$$ Kumho 165R15 732s on OEM steels didn't separate in HARD cornering manuevers. Sure, they rolled over and I might have scraped a rim, but no separation. Furthermore, if a high-end Michelin did that, they'd be out of business from lawsuits. Bottom line, the 2% difference in 195/65 and 205/65 shouldn't make a difference. I believe Maine passed this law with a batch of others in 1993, finally enacted them in 2004, and repealed most of them within 6 months - but the tire salesmen hang onto it.

Yep, it happens more often than it should, unfortunately. Keep in mind, I'm not drving around a parking lot doing this in my spare time. This is my job. And that job includes keeping Ford out of lawsuits.

When you combine heavy vehicles, with soft suspension, flexible sidewalls, possible under-inflated tires, weak shocks, hard driving in an emergency situation, you can have tires unseat. That is part of the reason why maintaining your vehicle is so important.

There are so many interdependent systems on a vehicle that small things that seem fairly insignificant can jump up and bite you in the ass.

Dude, you asked.