deciphering tire-speak

AaUuuuGaa! · Oct 8, 2004

I saw an article in a recent issue of a motorcycle rag that was interesting. But the author was either confused or he was simply a moron. Maybe you guys can clear things up for me.
It concerns the "code" that's imprinted on the sidewalls of every tire.
It'll be easiest to work with an example: 130/70R17 H 62

Here's what I'm sure of:
130 = width (in mm) of the tire
R = Radial
17 = size of rims the tire fits onto
H = "H" rating - for sustained 130 mph

Here are 2 things that I'm not so certain of:

62 = load at maximum air-pressure
I understand that "maximum" air-pressure is NOT the recommended air-pressure at which the tire should be run. But what exactly is that 62 supposed to tell me?

70 = aspect ratio (in percentage) of the height of the tire in relation to the width... right? If'n that's so, then the actual height of the sidewall of this example would be 70% of 130 = 91 mm... right? But the author goes on to say that the 70 means that the tire's sidewalls are 70 mm tall.:confused If'n that's true, then the 70 is simply a straight-up number, and NOT a ratio. But the author contradicts himself and says that it is a ratio. So... which is it?

Oh, and another tidbit of interesting info: every tire made after 2000 has a four-digit number imprinted on it that represents the date of manufacture. The first 2 digits denote the week and the last 2 digits denote the year.

frogstr · Oct 8, 2004

Yes, the 70 in your example is the ratio not the sidewall heigth.

The 62 should be the "LOAD INDEX" number which means it could carry 584 pounds at maximum recommended pressure. See load index chart at...
www.discounttire.com/dtc/brochure/info/helpDeskLoadIndex.jsp

You · Oct 8, 2004

frogstr said:
Yes, the 70 in your example is the ratio not the sidewall heigth.

The 62 should be the "LOAD INDEX" number which means it could carry 584 pounds at maximum recommended pressure. See load index chart at...
www.discounttire.com/dtc/brochure/info/helpDeskLoadIndex.jsp

+1 What magazine was this article in?

AaUuuuGaa! · Oct 8, 2004

I don't remember for sure. But I think it was the new "Motorcyclist".

AaUuuuGaa! · Dec 2, 2004

Here's a conundrum I'm having:

The stock tire on my Sp3 is a Bridgestone 190/50ZR17.
However, I was thinking about getting a Pirelli SuperCorsa 190/55ZR17...

Would anyone know what effects the difference in aspect ration would have on the bike's handling? Or if'n it may not even fit at all? :confused

You · Dec 3, 2004

AaUuuuGaa! said:
Here's a conundrum I'm having:

The stock tire on my Sp3 is a Bridgestone 190/50ZR17.
However, I was thinking about getting a Pirelli SuperCorsa 190/55ZR17...

Would anyone know what effects the difference in aspect ration would have on the bike's handling? Or if'n it may not even fit at all? :confused

My *guess* would be that it would fit on your bike without a problem since it's only a slightly taller sidewall.

Handling wise is another guess that it will make the bike a little less stable since your rear will be up higher. If the bike turns in slow now it may make the bike fall into turn faster which could be good or bad.

But this is only a guess. :shrug

Scotteq · Dec 3, 2004

Compared to the normal 180/55, a 190/50 is a little flatter and therefore somewhat slower turning. Also, in my experience, a 190/50 is less neutral mid corner.

A 190/55's profile is supposed to mimic that of a 180/55. Except 10mm wider, which should also mean that it's about 5.5mm taller. That's about 1/8". You may or may not need to make any suspension/height adjustments to compensate. Hell, you might like it taller...

If you ride real fast, you might want to shoot an eMail to Pirelli and ask how much (if any) the tire 'grows' at speed. IIRC, Pirellis use a "Zero Degree" belt (Runs in the exact same direction as travel), which theoretically should prevent tire growth from centripetal forces, but..... If the tire grows, and you have little clearance between it and the swinger, it isn't outside the realm of possibility that it could rub when you get real aggressive with the Loud Handle.

Scott

eRacer777 · Dec 3, 2004

Ok now that Mr. AaUuuuGaa! has his answer...what about mixing tire brands? Let say that same SC 190/55 tire and a BT-010 front tire for a hypothetical scenario. Think it'll work or cause unforeseen / unwanted handling effects? I think physically it will work but you won't get the most out of each tires best abilities. Someone please debunk or fortify this concept for us....

Scotteq · Dec 3, 2004

eRacer - That's a bad idea. Not only can the tire profiles mismatch, but constructiion differs as well. Match your tires, please.

Scott

eRacer777 · Dec 3, 2004

Scotteq said:
eRacer - That's a bad idea. Not only can the tire profiles mismatch, but constructiion differs as well. Match your tires, please.

Scott

You heard that Mr. AaUuuuGaa!? I told you so...:nanana

RCM78 · Dec 4, 2004

There are several reasons I wouldnt mix those tires.
1, The rear Super Corsa has a much taller and rounder profile then the street Bridgestone.
2, The stickier SuperCorsa can and will push the front bridgestone when riding hard.
3, The pirelli has a much softer construction the the bridgstone. This will make the bike handle weird. The rear tire will me much more compliant then the front...

In2Speed · Dec 4, 2004

RCM78 said:
There are several reasons I wouldnt mix those tires.
1, The rear Super Corsa has a much taller and rounder profile then the street Bridgestone.
2, The stickier SuperCorsa can and will push the front bridgestone when riding hard.
3, The pirelli has a much softer construction the the bridgstone. This will make the bike handle weird. The rear tire will me much more compliant then the front...

Good Job Ralph, Mike I would suggest the soft front and med rear for the Super Corsas, I destroyed the SuperSoft front in 1 day and a half. Dont mix company's!

Jay

deciphering tire-speak

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