Need help buying tires , 55 to 50

First question is, why do you want to change tire profile?

Have you experimented with different pressures, or checking alignment?

I have no idea on your questions regarding tires.

Your '50' or '55' is an aspect ratio, not a diameter. If you knew the actual rollout (loaded circumference at proper pressure) you could know the difference between them for rotations per mile or per engine speed etc. But you don't.

1. Go to tirerack.com. They are honest, their prices are good. The customer reviews are doubtful because they are often made by people who have just changed from a failed tire to a new tire and are impressed with the improvement.
2. Tires with directional tread look like they have directional tread. If you see a V shape or you see a center rib, it's a directional tire. I like directional tread designs; they perform much better on wet roads. Yes, they limit your ability to easily rotate tires.
3. TPMS reset on many newer cars requires plugging in an OBD-II tool and telling the computer there is a new tire. Not a huge deal, but a thing worth billing for.
4. The difference in noise between different tires is substantial, but tires sold as "quiet" aren't necessarily quieter. If you drive a very quiet car where the tire noise is one of the worse noise sources then you might worry about trying different "quiet" tires. Note that the customer ratings about noise on tirerack bear no connection with how noisy the tire is.

--scott

On 4/4/2020 6:14 AM, micky wrote: ...

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Aspect ratio gives profile and is ratio of sidewall section height to section width...but the overall diameter is

Doverall = Drim + 2*Hsection

So the ratio of the two tires is

(Drim + 2*Hsection)/(Drim + 2*Hsection*55/50)

Well, this is simple w/ MATLAB which is open in other window...

So there's only roughly a 3% difference in overall diameter instead of

All in all, it doesn't matter enough that you'll notice it other than, perhaps, the lower profile will drive and ride a little more stiffly. Whether you'll actually notice unless you drive the vehicle very hard is doubtful.

Why there's so much difference in price I've not looked at at all...more marketing than anything else one would suspect.

Nice drawing/explanation at

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Scott Dorsey: RE: Tire Noise vs Ratings

By stating that "customer ratings on Tire Rack have no bearing on actual tire noise", are you suggesting that how noisy a particular tire is is subjective?

On 4/4/2020 9:30 AM, dpb wrote: ...

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Sorry, missed a fixup on renaming the overall diameter anonymous function...in last section...

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On 4/4/2020 9:30 AM, dpb wrote: ...

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Just noticed was 215, not 225. Minimal difference but for the record...

No, one could measure it objectively. But the people who write reviews on Tire Rack do not. They just replaced their bald Comfortreads with brand new Defenders and... wow... they handle so much better and don't make that swishing noise!

Most of the people making comparisons are comparing bad worn-out tires to new tires, and this is not a fair comparison.

--scott

Scott Dorsey:

Your 'swishing' comment triggered something I remember from decades ago, but rarely ever hear anymore:

Back in the '70s, the tires on about one out of every five cars going by a busy street made a crackly gravelly sound. Like it had a hundred pair of casino dice inside the tires or something. I forgot what someone said that was.

Do you remember that?

Of course, but it helps you to calculate the nominal diameter. The formula is simple:

rim diameter + ((tire width * aspect ratio as a percentage) *2)

Converting the 17" rim diameter to mm, you get 431.8 ((215 * .50) * 2) = 215

((215 * .55)) * 2 = 236.5

Now you can compare 646.8 to 668.3.

All of those are nominal values. Production differences will cause some variation, not to mention wear as a tire is used.

While I find it's literally both trivial & impossible to properly select tires by its known trusted specs, I do well agree with others on the almost total lack of validity of most "boy racer" tire reviews on the net.

As for objective measurement... o Measuring and Reporting Tire-Pavement Noise Using On-Board Sound Intensity (OBSI)

They essentially mount a probe at the x:y:z 3-dimensional leading & trailing edges of the tire contact patch with the road surface at 60mph: o 4 inches horizontal from the tire sidewall o 3 inches vertical above the pavement o 4.125 inches in front and behind the axle centerline

Typical concrete tire interfaces, they say, generate from 99dBA to 108dBA reported in the 400 Hz to 5,000 Hz band, where (get this), the results are viewed in Google Earth!

I don't know what _that_ noise was, but this tire-seller page (so take it for what it's worth), "claims" tire noise can be from a variety of causes... o How to Keep Tire Noise Down

1. UNBALANCED TIRES
2. TIRES THAT NEED ROTATING
3. OFF-ROAD AND PERFORMANCE TIRES
4. UNEVEN TREADWEAR
5. UNEVEN OR LOW TIRE PRESSURE
6. DEBRIS IN TIRES

The cynical may note that the tire seller in question holds most of the solutions, or so it might seem...

This article at least explains somewhat that tire noise is normal... o Common Causes of Tire Noise and How to Fix Them

"Wide tires generate more noise than narrow tires..." "Touring tires and low-rolling-resistance (LRR) tires are typically the quietest, while snow tires and off-road tires are the noisiest (studded snow tires are even louder). Performance tires and all-season tires fall somewhere in between. Because of their stiff sidewalls, run-flat tires (RFT) are usually noisier than non-RFT tires."

"Low-profile tires typically generate more noise because there is less rubber sidewall to absorb it. This noise gets transmitted through the chassis and the rest of the vehicle. While these tires offer improved traction, they can sometimes generate excessive noise."

For what it's worth, Consumers Union does test & report for measured noise. o Consumer Report: Tire Rating & Reviews

I'll get back to you about individual replies but I see a tire store here advertising rim seals for $15/tire but I can't find anything about them with google.

They're closed now but do you know what rim seals are.