Need help translating chinese tire sizing into Pirelli SL26 By olivertwisted (Read 1,193 times)

[olivertwisted]

I've got what appears to be the original tires on this Jonway yyt150t-2 QMJ157. The only stamping on them that I see as relevant is "Yuanxing" brand, 4.00 x 12 . I want to replace them with the Pirelli SL26's as, I've read many opinions and they seem to be great, by consensus. But, I'm not well versed enough in tires to know what size my scoot requires. Does anyone know?

Thank you.

[jct842]

Can't remember off hand but if you were to give motorcycle super store a call they will tell you and they are generly the best price on tires. There are charts on the net if you search too. I am too lazy to ddo that at 12:30 in the am

Probably around 120/?/12

[olivertwisted]

Thanks, yes I eventually will call to confirm before placing an order. I found some charts and general info ( I usually do try to help myself before calling on anyone ) but the info just made me dizzier on the subject. I've had motorcycle super store's site open and you're right about their best price. I had tried earlier to use their support function but it won't send from the page. I see they are open tomorrow so, I'll try to catch someone there.
Thanks again jct842

[richardv]

The 4 is in inches which is 102 in millimeters.

[Alleyoop]

Most replace their 4.00x12 tires with a 120/70/12 front and 130/70/12 rear.

[olivertwisted]

Ahhh, thank you!

[richardv]

Sorry I wasn't feeling well this morning and should have mentioned the equation used. So here goes.
4 inches multiplied by 25.4 equals 101.6 millimeters. Being that the American sizes are not very accurate 120mm would be almost exactly the same.
120mm divided by 25.4 = 4.724".

[rks]

A quick search turned up this.....

12" Tires

4.00x12 : 4.0"W x 20.5"T
110/70/12 : 4.3"W x 18.1"T
110/90/12 : 4.3"W x 19.8"T
110/100/12 : 4.3"W x 20.7"T
120/70/12 : 4.7"W x 18.6"T
130/70/12 : 5.1"W x 19.2"T
140/60/12 : 5.5"W x 18.6"T
140/70/12 : 5.5"W x 19.7"T


Looks like your closest match is 110x100x12

[olivertwisted]

Thanks, richardv I do hope that you feel better soon!

[olivertwisted]

Thanks rks too.
So, all we are doing here is converting inches to millimeters, yes? "4 x 12" does refer to inches? I was afraid to assume what seemed obvious since, it is another $100 into this "rust animal" that I probably couldn't return.

[olivertwisted]

No, I'm still not getting it. "Fibro fog" getting in the way here, I guess. I used a inches to millimeter converter and got 102 x 305. I just don't have any comprehension about these formulas.

[JR]

Dec 13, 2015 18:52:49 GMT -6 olivertwisted said:

No, I'm still not getting it. "Fibro fog" getting in the way here, I guess. I used a inches to millimeter converter and got 102 x 305. I just don't have any comprehension about these formulas.

Go to the bottom of any page, check the "Tire Size Calc." and hit Select, then use it to find your tire size.

JR

[richardv]

Dec 13, 2015 18:28:15 GMT -6 olivertwisted said:

Thanks, richardv I do hope that you feel better soon!

Thank you it was just a one day thingy.

Did you also notice in the chart that the outside diameter is also listed. That is important as well. A bigger diameter will make the speed at a fixed engine RPM faster. While a smaller diameter will make you go slower at the same engine RPM. It's kind of like changing the gear ratio.

I hope that helps your confusion this evening.

[jct842]

One more thing to take into consideration is most chinese scooters have a optimistic speedometer reading. In other words when the speedo says 60 you may only be going 55 or slower. For more confusion if yours is that way you might want to think of getting a slightly larger front tire diameter to get the speedo reading more like it should.

And you are looking good when considering sl26 tires. Scooters and low or low center of gravity bikes have to lean further over when rounding a curve than a taller high center of gravity machine so traction is real important with them. Pirelli makes tires that will grab the road and hold onto it.

[olivertwisted]

... "For more confusion" lol, that's exactly what I need, jct842 ! What you and richardv said makes some sense to me though. It seems to coincide with Alley's mention of the two slightly larger sizes than stock size, that many prefer to use. I will get my calipers out tomorrow to check clearances between shocks on front and rear, to have the best info when I call MSS.
Cool, the SL26's are what I'll stick with (Pardon the pun) and I'll look into the sizes that Alleyoop mentioned. I appreciate you all chiming in with all the info, recommendations and calculations !