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Metric vs Imperial Tyre Size

 
 
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ahlidap
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Joined: 06 Nov 2010
Odometer: 11




PostPosted: Wed Aug 08, 2012 8:27 am    Post subject: Metric vs Imperial Tyre Size Reply with quote

Hi,

I've been searching the foruns, but I haven't found anything...
Basically, I can't figure how this is calculated...


I've always used 205/75 R15 on my NIVA, but I would like to return to the original 16" rims, but with a taller and wider tyre (when compared to 176R16).


So, I don't want a "BIG" lift in my NIVA to use 205R16 and don't want to loose mine ~7L/100Km ( 40 mpg? )..


According to baxters web site:

"The biggest tyres you can fit on a standard Niva are 195/80R (6.00x16) on the 16" rims"


This is exactly what I'm looking for!

But when I search for a formula, I always get to:
6.00x16...

width = 6"* 25.4mm = 152.4mm.....

err.. not 195 :/



Can you help me?
Is 6.00x16 , the same as 600R16 ?


Another "problem" is that, Brazilians say that 175R16 is the same as 6.95R16... so.. how could a 6.00R16 be wider??


I have a 50/50 tyre, and I think I would keep with it...
http://www.fedimatyres.com/pt/4x4/4x4/fronteira but with original rim Smile


For offroad this is a very good tyre!
http://www.recip-pneus.com/epages/Store.sf/pt_PT/?ObjectPath=/Shops/RecipPneus/Products/%22RECIP%20TRIAL%22/SubProducts/%22RECIP%20TRIAL%20-%206.00R16%22


And If you look on two, FEDIMA have 600R16 and RECIP 6.00R16.



Hope you can help me with this sizes Embarassed
Thanks


PS:
Also found this table, that shows the 600R16 somewhere between the 175/80 R16 and 215/80 R15... so, probably the 195/80R16.

__________________________________
1997 Lada Niva 1.9D Tinga
--> Turbo e manifolds from Citroen ZX
--> + 1/4 Diesel
--> BackBox Exhaust out!
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Xpajun
Mud Obsessed


Joined: 22 Sep 2008
Odometer: 3242



1988 Mitsubishi Shogun

PostPosted: Wed Aug 08, 2012 9:38 am    Post subject: Reply with quote

To convert:


divide the first number by 2.54 (gives you inches) this gives you the width of the tyre

Then multiply the width by the number after the slash as a % (i.e /75 = 75% or 0.75) multiply the result by 2 then add on the wheel size (if there is no number after the first then use 80% or 0.8 as the multiplier)


EXAMPLE:

205/75 R15

205 divide by 25.4 = 8.07086614 = tyre width

8.07086614 x 0.75 (75%) = 6.05314916 X 2 = 12.1062992 + 15 = 27.1062992

Rounding up the figures to the nearest .5" your tyres are 27 x 8 x 15
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Xpajun
Mud Obsessed


Joined: 22 Sep 2008
Odometer: 3242



1988 Mitsubishi Shogun

PostPosted: Wed Aug 08, 2012 9:59 am    Post subject: Re: Metric vs Imperial Tyre Size Reply with quote

ahlidap wrote:
Hi,


According to baxters web site:

"The biggest tyres you can fit on a standard Niva are 195/80R (6.00x16) on the 16" rims"


This is exactly what I'm looking for!

But when I search for a formula, I always get to:
6.00x16...

width = 6"* 25.4mm = 152.4mm.....

err.. not 195 :/



Can you help me?
Is 6.00x16 , the same as 600R16 ?


Another "problem" is that, Brazilians say that 175R16 is the same as 6.95R16... so.. how could a 6.00R16 be wider??





The 6.00x16 would indicate 6" wide by 16" wheel - at a 80% profile would equal a 25.6" tyre

Think baxters may be wrong

My calculations say that 175R16 is about the same as a 6.95R16 (standard aspect ratio is 80%) and that would give you a 30" tall tyre
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ahlidap
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Joined: 06 Nov 2010
Odometer: 11




PostPosted: Wed Aug 08, 2012 10:32 am    Post subject: Re: Metric vs Imperial Tyre Size Reply with quote

Xpajun wrote:



The 6.00x16 would indicate 6" wide by 16" wheel - at a 80% profile would equal a 25.6" tyre

Think baxters may be wrong

My calculations say that 175R16 is about the same as a 6.95R16 (standard aspect ratio is 80%) and that would give you a 30" tall tyre



Ok Wink
This confirms the things on the web..
So, as you said, maybe the error is in the info given by baxters..



195/80 R16 are hard to find... at least with a 50 road / 50 offroad tread.


Thanks for your quick reply!
Wink

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--> + 1/4 Diesel
--> BackBox Exhaust out!
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scrunt
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Joined: 11 Jul 2012
Odometer: 985
Location: Tayside.



PostPosted: Wed Aug 08, 2012 2:24 pm    Post subject: Reply with quote

Are you sure that 195 is the widest tyre the standard 16" rims can take,
have you measured the actual rim width?

You are going to posiibly lose some MPG anyway are you not, going to even keeping the same rolling radius but from a A/T tread to a Mud tread?

?? I think you were saying that you want to stay with an All Terrain style tread?
The one you show is like a Copy of the BF Goodrich all terrain tread and common here in remoulds. i used those myself in 195/80/15 (Colways)

195/75/16 Malatesta M&S
or 195/80/16 Mud tyres for taller.
http://www.tyresdirectuk.co.uk

Staying at the same width as 205/75/15
why not go 205/65/16, Not taller tho.

taller would be 205/80/16 which is probably too much for you.
http://www.kouki.co.uk/utilities/visual-tyre-size-calculator

http://www.camskill.co.uk

george
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baxter
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Joined: 08 May 2006
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Location: Dunedin, New Zealand


1990 Lada Niva

PostPosted: Sun Sep 02, 2012 9:28 am    Post subject: Re: Metric vs Imperial Tyre Size Reply with quote

Xpajun wrote:
The 6.00x16 would indicate 6" wide by 16" wheel - at a 80% profile would equal a 25.6" tyre

Think baxters may be wrong


Off the top of my head Imperial tyres are measured in height not width (like metric tyre are), hence a 6.00x16 is a 12 (ie 6+6) + 16 = 28" tall tyre.



There should be a link to a couple of tyre calculators on my yre page that should answer above.

__________________________________
1990 Niva 1600, 2" lift, LSD
www.ladaniva.co.uk/baxter -Baxter's Temple of Niva Site
If you do not have anything to occupy yourself - buy a Niva.
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Xpajun
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Joined: 22 Sep 2008
Odometer: 3242



1988 Mitsubishi Shogun

PostPosted: Sun Sep 02, 2012 12:25 pm    Post subject: Re: Metric vs Imperial Tyre Size Reply with quote

baxter wrote:
Xpajun wrote:
The 6.00x16 would indicate 6" wide by 16" wheel - at a 80% profile would equal a 25.6" tyre

Think baxters may be wrong


Off the top of my head Imperial tyres are measured in height not width (like metric tyre are), hence a 6.00x16 is a 12 (ie 6+6) + 16 = 28" tall tyre.



There should be a link to a couple of tyre calculators on my yre page that should answer above.



My calculations were based on the quote below - standard aspect ratio is (as far as I'm aware) 80%

The Numeric system is old and outdated and unfortunately not only difficult to convert (so you know what you're fitting) but the conversion has to be based on an assumption.


Quote:
Numeric

Earliest system, dates back to the 30’s when there were few tyre sizes available (or needed)

Example:

9.15-15

9.15 is the section width in inches
15 is the rim diameter in inches

Notes:
- Using this system you can’t tell the OD of the tyre without knowing the Aspect Ratio
- In the 1950s and early 1960s, the standard aspect ratio was 82-84%
- Around 1970, bias ply tyres moved to a 78% aspect ratio
- In the 70’s the "standard" aspect ratio dropped to 75%
- Today, Aspect Ratios of 65%, 60% and even as low as 35% are available.
- If you know the AR of the tyre in question you can calculate the OD as: (Section Width x Aspect Ratio) x 2 + Rim Diameter (eg. in the above example, if we knew the Aspect Ratio were 78%: (9.15 x 0.78 ) x 2 + 15 = 29.3" )
- If you don’t know the AR, the only way to tell the OD is to consult the manufacturer’s specifications.


Incidentally I've found that so many of the online tyre calculators to be flawed that I no longer use them - nor would I advise anyone to use them. In addition the size written on the side wall of the tyre very often bears no relationship to the size of the tyre anyway, especially with remoulds and, sometimes, even with new tyres as well
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baxter
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Joined: 08 May 2006
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Location: Dunedin, New Zealand


1990 Lada Niva

PostPosted: Mon Sep 03, 2012 1:51 pm    Post subject: Reply with quote

Ahh so it is a measure of width afterall. My ones must have had a close to 1:1 width to height ratio (except my tractor ones, which explains why they're 32 inch 6.00-16s) hence they measure either way.

But yeah, not including aspect ratio on various Imperial tyre sizes would indeed make it impossible to know overall diameter, so to answer the op - it depends on the aspect ratio; ask the seller the overall diameter.

__________________________________
1990 Niva 1600, 2" lift, LSD
www.ladaniva.co.uk/baxter -Baxter's Temple of Niva Site
If you do not have anything to occupy yourself - buy a Niva.
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lambert
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PostPosted: Wed Sep 12, 2012 5:42 am    Post subject: Reply with quote

600's 650's 750's etc are all 100% aspect ratio. So as to get different sizes overall the rim size was altered. Better way than all this metric garbage we have now
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scrunt
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Joined: 11 Jul 2012
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PostPosted: Wed Sep 12, 2012 10:40 am    Post subject: Reply with quote

http://www.ctc.org.uk/DesktopDefault.aspx?TabID=3802
Laughing
600, 650, 700, is that not 'mm'?
Is that not Metric garbage measurements.

Now 31", 33",35" etc, is Imperial i think,
12" to the foot and 36" to a yard. Good old British. The Empire & the Commonwealth, The Raj rule. Wink

george
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Xpajun
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Joined: 22 Sep 2008
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1988 Mitsubishi Shogun

PostPosted: Wed Sep 12, 2012 1:09 pm    Post subject: Reply with quote

scrunt wrote:
http://www.ctc.org.uk/DesktopDefault.aspx?TabID=3802
Laughing
600, 650, 700, is that not 'mm'?
Is that not Metric garbage measurements.

Now 31", 33",35" etc, is Imperial i think,
12" to the foot and 36" to a yard. Good old British. The Empire & the Commonwealth, The Raj rule. Wink

george


600 = 6" 650 = 6.5" 700 = 7" george so imperial and very old as in 1930s era Shocked
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