Wheel Ratings and Nomenclatures

[B2Bomber]

Earlier posts were from the Hyundai Getz thread, I figured I'd just post it here just incase the mods reckon I'm pushing my luck by posting tech questions over there.

I think www.tyrerack.com has a tire calculator. Basically, a 185/55r15 tire is a tire that is 185mm wide. The height of the side walls is 55% of 185 and is known as the ASPECT RATIO. 15 refers to the rim size intended for the tire. 5.5 jx15 means a 5.5 inch wide tire that is 15 inches across.

TY ulit!!! Looks like my assumptions were almost correct, I had a feeling the 55 had something to do with the side walls but didn't know whether it was the actual value or something else. I think I'm confused though, if used a 5.5 x jx15 which is 5.5" (139.7mm) how is it that a 185mm tire be appropriate for it? Or the 185mm tire rating is the width at the bulges?

Anyway of telling what x wide tire is appropriate with a y wide rim/mags? Oh and what about the letters, say like in 5.5 jx15, 185/55r15, 4.0Tx14, T105/70D14, what do the letters 'j', 'r', 'T' and 'D' stand for.BTW: I couldn't remember if it was in this forum that I got this but this is where I calc'ed the stock and compared it with the options: http://www.miata.net/garage/tirecalc.html
Oh, and uh, while I'm at it. I've been actually eyeing a mag wheel design but I'm clueless with regards to the size ratings nomenclature take for example this:


I assume the 15x6.5 is the same as previously discussed, 15in x 6.5in mags. What's the +xx for? Like the +18 or +33. The 4h/5h I assume are the number of holes(?) and the x/y right behind it are the diam/depth of the holes?

My main concern for these queries are basically safety. I wouldn't want to compromise my ride's safety should I manage to get a mag/tire combo that's not included in my ride's factory recommended options. Plus my function over form principle. If it would affect my ride, say in comfort, etc., in a significant manner, I'd rather opt for something within my ride's manufacturer's recommended options which are:
Rim Size Wheel Size
4.5 jx13 155/80r13
5.0 jx13 155/80r13
5.0 jx14 165/65r14
5.5 jx14 175/65r14
5.5 jx15 185/55r15
4.0 Tx14 T105/70D14
Lastly, am I correct at saying that to compute for the overall wheel diameter, in mm; one can use this formula:
((a*(b/100))*2)+(c*25.4)
where:
a=tire width (mm)
b=aspect ratio (%)
c=rim size (in)

and computing for rev/min at 20kph is:
(20000000/(pi*d))/60
where:
d=overall wheel diameter (mm)

TIA 4 d nfos-------

[B2Bomber]

Drats, I think I may have stumbled upon the answer my self, will read through it first...
http://www.motorcar.com.sg/Informati...ance/Tyres.htm

[nugundam93]

the +xx would be for the wheel offset. for that, always follow the correct offset as stated in the car's manual or you risk prematurely wearing out the wheel bearings and related suspension components.

http://www.enkei.co.jp/en/t_know.html

[OTEP]

The tire is usually wider than the wheel. Otherwise the bead won't hold and it won't be airtight.

I run a 12.5" wide tire on 7" wheels.

[B2Bomber]

thanks for all the input.

[B2Bomber]

hello guys, I'm back with another set of questions, hope you can still help me out. I've asked my gf to look for any mention of wheel offset for my car (05 Getz) (according to peeps from another board, it's +38) from its manual and it seems there aren't any.

all I see is wheel base, wheel tread (which I would also like to ask why does the front and rear values differ) and wheel free play(or is this the elusive wheel offset I've been looking for). I just need to make sure that I'll be getting the correct value. Lastly, are the wheel's specs like whether they are 15x6.5 +38 4h/100 etched on the wheel itself? How can you tell if the shop's just trying to make a quick buck by selling you one which isn't right, assuming you don't have your ride along with you when you go to the shop? TIA.

[theveed]

offset, if your spare isn't a steel rim (meaning same sya as your other mounted wheels) you can measure the offset naman eh.



Wheel offset is the distance between the rim centerline and the mounting face of the wheel.

[B2Bomber]

hmm...oo nga ano, masubukan nga yun sa May 20. :-D pero teka... steel rim rin pala yun e. tulad nung mga nakakabit ngayon. yun lang, may wheel cover yung mga nakakabit. :-D di ba applicable sa mga rim yung offset-offset? sa mags lang?

[nugundam93]

sir, afaik, may value na printed/stamped sa loob ng rim mismo. you'll have to take off the rim from the car though.

if +nn, positive offset yan and nn is the value.

[B2Bomber]

sir, afaik, may value na printed/stamped sa loob ng rim mismo. you'll have to take off the rim from the car though.

if +nn, positive offset yan and nn is the value.

hmm...looks promising. ok, will do that as soon as I get home. ty