Re: GC tires - 225/75 vs 245/70 (R16)
 

J Strickland proclaimed:
> Not if the change was from 225 to 235. These numbers represent the tread
> width in mm, and 10mm is the functional equivelent of 3/8".
>
> Now, there is some misunderstanding (at least on my part) of just exactly
> where they measure 225 or 235, and the actual tread blocks being square on
> one tire and rounded off on the other might play a role in your perception
> of an inch difference, but the actual difference is 10mm. Your point being
> that you are looking at the tread patch on the ground is not lost on me ...
>
The 225/235 is the sectional width, not the tread width. And now that
you mention it, I can't remember where they measure it either... and
the actual size is always rounded off anyway. Unless the tires
involved have exactly the same tread compounds and patterns,
comparing traction based on section [or tread] width is a waste of
time, as it really depends more on the pattern and compounds.

Re: GC tires - 225/75 vs 245/70 (R16)
 

"J Strickland" <spam@nospam.net> wrote in message
news:3b2dncRGuadR9b3eRVn-gA@ez2.net...
> There will be no difference (OK, the difference will be very small).
>
> The 245 is 20mm wider, that's 10mm off of center, which is about 3/8".
This
> should pose no particular problem for clearance inside the fenders.
>
> The 70 or 75 represent a diameter change (larger in your case) of 0.4
> inches. This will not present any problems for the speedometer or the
> gearing. Indeed, your speedometer is about 3 mph fast at 80mph right now,
> and will be about 2 mph fast with the larger tires. You will be fine.
>
> The caluclation is
> <width -- 225> * <aspect ratio -- 75%> * 2 / 25.4 + <rim -- 16> = overall
> diameter. (you multiply by 2 to get the total sidewall height, and divide
by
> 25.4 to convert from mm to inches.)
>
>
tnx for all the info, the math, and the tire discussion -
I was going to get the Bridgestone Dueler H/L - but it was a bit pricey
($700)
if I only keep the 2001 Grand Cherokee Laredo another couple of years.
I might go with the Firestone Destination LE ($450)
and also go with the alt size of 245/70R16

Re: GC tires - 225/75 vs 245/70 (R16)
 

"J Strickland" <spam@nospam.net> wrote in message
news:3b2dncRGuadR9b3eRVn-gA@ez2.net...
> There will be no difference (OK, the difference will be very small).
>
> The 245 is 20mm wider, that's 10mm off of center, which is about 3/8".
This
> should pose no particular problem for clearance inside the fenders.
>
> The 70 or 75 represent a diameter change (larger in your case) of 0.4
> inches. This will not present any problems for the speedometer or the
> gearing. Indeed, your speedometer is about 3 mph fast at 80mph right now,
> and will be about 2 mph fast with the larger tires. You will be fine.
>
> The caluclation is
> <width -- 225> * <aspect ratio -- 75%> * 2 / 25.4 + <rim -- 16> = overall
> diameter. (you multiply by 2 to get the total sidewall height, and divide
by
> 25.4 to convert from mm to inches.)
>
>
tnx for all the info, the math, and the tire discussion -
I was going to get the Bridgestone Dueler H/L - but it was a bit pricey
($700)
if I only keep the 2001 Grand Cherokee Laredo another couple of years.
I might go with the Firestone Destination LE ($450)
and also go with the alt size of 245/70R16

Re: GC tires - 225/75 vs 245/70 (R16)
 

"J Strickland" <spam@nospam.net> wrote in message
news:3b2dncRGuadR9b3eRVn-gA@ez2.net...
> There will be no difference (OK, the difference will be very small).
>
> The 245 is 20mm wider, that's 10mm off of center, which is about 3/8".
This
> should pose no particular problem for clearance inside the fenders.
>
> The 70 or 75 represent a diameter change (larger in your case) of 0.4
> inches. This will not present any problems for the speedometer or the
> gearing. Indeed, your speedometer is about 3 mph fast at 80mph right now,
> and will be about 2 mph fast with the larger tires. You will be fine.
>
> The caluclation is
> <width -- 225> * <aspect ratio -- 75%> * 2 / 25.4 + <rim -- 16> = overall
> diameter. (you multiply by 2 to get the total sidewall height, and divide
by
> 25.4 to convert from mm to inches.)
>
>
tnx for all the info, the math, and the tire discussion -
I was going to get the Bridgestone Dueler H/L - but it was a bit pricey
($700)
if I only keep the 2001 Grand Cherokee Laredo another couple of years.
I might go with the Firestone Destination LE ($450)
and also go with the alt size of 245/70R16

Re: GC tires - 225/75 vs 245/70 (R16)
 

"J Strickland" <spam@nospam.net> wrote in message
news:3b2dncRGuadR9b3eRVn-gA@ez2.net...
> There will be no difference (OK, the difference will be very small).
>
> The 245 is 20mm wider, that's 10mm off of center, which is about 3/8".
This
> should pose no particular problem for clearance inside the fenders.
>
> The 70 or 75 represent a diameter change (larger in your case) of 0.4
> inches. This will not present any problems for the speedometer or the
> gearing. Indeed, your speedometer is about 3 mph fast at 80mph right now,
> and will be about 2 mph fast with the larger tires. You will be fine.
>
> The caluclation is
> <width -- 225> * <aspect ratio -- 75%> * 2 / 25.4 + <rim -- 16> = overall
> diameter. (you multiply by 2 to get the total sidewall height, and divide
by
> 25.4 to convert from mm to inches.)
>
>
tnx for all the info, the math, and the tire discussion -
I was going to get the Bridgestone Dueler H/L - but it was a bit pricey
($700)
if I only keep the 2001 Grand Cherokee Laredo another couple of years.
I might go with the Firestone Destination LE ($450)
and also go with the alt size of 245/70R16

Re: GC tires - 225/75 vs 245/70 (R16) Now Tire vs Tread size
 

Lon wrote:
>
> J Strickland proclaimed:
> > Not if the change was from 225 to 235. These numbers represent the tread
> > width in mm, and 10mm is the functional equivelent of 3/8".
> >
> > Now, there is some misunderstanding (at least on my part) of just exactly
> > where they measure 225 or 235, and the actual tread blocks being square on
> > one tire and rounded off on the other might play a role in your perception
> > of an inch difference, but the actual difference is 10mm. Your point being
> > that you are looking at the tread patch on the ground is not lost on me ...
> >
> The 225/235 is the sectional width, not the tread width. And now that
> you mention it, I can't remember where they measure it either... and
> the actual size is always rounded off anyway. Unless the tires
> involved have exactly the same tread compounds and patterns,
> comparing traction based on section [or tread] width is a waste of
> time, as it really depends more on the pattern and compounds.

I think that is what Jeff is missing, the 'section' width vs the 'tread'
width.

It is very deceiving and I learned to only trust a tape measure for the
'actual' tread width way back in the 70's.

I just measured my new BFG AT's and the P235/75x15 tire has a tread that
is only 7 7/8" or 200mm wide.

That is a far cry from the 'book' spec of 235mm wide. Well, over 15%
difference anyway.

I also measured my son's vans tires and the P205/75x14's and the tread
width is only 165mm, not the 205mm one would think!

I have a goodyear spare that is a P235/75 15 M+S and the tread is only
180mm wide! Crap, that is a difference of 55mm or over 2" from the
'book' size!

Now if I take a caliper and measure the sidewall width at the biggest
part, (spare with no load on it) it is 235mm just like the book says.
You can hold a 3' long straight edge on both sides of the tire across
the center sticking out both ends and measure between them to get the
section or sidewall width or use a big caliper.

Mike
86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00
88 Cherokee 235 BFG AT's

Re: GC tires - 225/75 vs 245/70 (R16) Now Tire vs Tread size
 

Lon wrote:
>
> J Strickland proclaimed:
> > Not if the change was from 225 to 235. These numbers represent the tread
> > width in mm, and 10mm is the functional equivelent of 3/8".
> >
> > Now, there is some misunderstanding (at least on my part) of just exactly
> > where they measure 225 or 235, and the actual tread blocks being square on
> > one tire and rounded off on the other might play a role in your perception
> > of an inch difference, but the actual difference is 10mm. Your point being
> > that you are looking at the tread patch on the ground is not lost on me ...
> >
> The 225/235 is the sectional width, not the tread width. And now that
> you mention it, I can't remember where they measure it either... and
> the actual size is always rounded off anyway. Unless the tires
> involved have exactly the same tread compounds and patterns,
> comparing traction based on section [or tread] width is a waste of
> time, as it really depends more on the pattern and compounds.

I think that is what Jeff is missing, the 'section' width vs the 'tread'
width.

It is very deceiving and I learned to only trust a tape measure for the
'actual' tread width way back in the 70's.

I just measured my new BFG AT's and the P235/75x15 tire has a tread that
is only 7 7/8" or 200mm wide.

That is a far cry from the 'book' spec of 235mm wide. Well, over 15%
difference anyway.

I also measured my son's vans tires and the P205/75x14's and the tread
width is only 165mm, not the 205mm one would think!

I have a goodyear spare that is a P235/75 15 M+S and the tread is only
180mm wide! Crap, that is a difference of 55mm or over 2" from the
'book' size!

Now if I take a caliper and measure the sidewall width at the biggest
part, (spare with no load on it) it is 235mm just like the book says.
You can hold a 3' long straight edge on both sides of the tire across
the center sticking out both ends and measure between them to get the
section or sidewall width or use a big caliper.

Mike
86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00
88 Cherokee 235 BFG AT's

Re: GC tires - 225/75 vs 245/70 (R16) Now Tire vs Tread size
 

Lon wrote:
>
> J Strickland proclaimed:
> > Not if the change was from 225 to 235. These numbers represent the tread
> > width in mm, and 10mm is the functional equivelent of 3/8".
> >
> > Now, there is some misunderstanding (at least on my part) of just exactly
> > where they measure 225 or 235, and the actual tread blocks being square on
> > one tire and rounded off on the other might play a role in your perception
> > of an inch difference, but the actual difference is 10mm. Your point being
> > that you are looking at the tread patch on the ground is not lost on me ...
> >
> The 225/235 is the sectional width, not the tread width. And now that
> you mention it, I can't remember where they measure it either... and
> the actual size is always rounded off anyway. Unless the tires
> involved have exactly the same tread compounds and patterns,
> comparing traction based on section [or tread] width is a waste of
> time, as it really depends more on the pattern and compounds.

I think that is what Jeff is missing, the 'section' width vs the 'tread'
width.

It is very deceiving and I learned to only trust a tape measure for the
'actual' tread width way back in the 70's.

I just measured my new BFG AT's and the P235/75x15 tire has a tread that
is only 7 7/8" or 200mm wide.

That is a far cry from the 'book' spec of 235mm wide. Well, over 15%
difference anyway.

I also measured my son's vans tires and the P205/75x14's and the tread
width is only 165mm, not the 205mm one would think!

I have a goodyear spare that is a P235/75 15 M+S and the tread is only
180mm wide! Crap, that is a difference of 55mm or over 2" from the
'book' size!

Now if I take a caliper and measure the sidewall width at the biggest
part, (spare with no load on it) it is 235mm just like the book says.
You can hold a 3' long straight edge on both sides of the tire across
the center sticking out both ends and measure between them to get the
section or sidewall width or use a big caliper.

Mike
86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00
88 Cherokee 235 BFG AT's

Re: GC tires - 225/75 vs 245/70 (R16) Now Tire vs Tread size
 

Lon wrote:
>
> J Strickland proclaimed:
> > Not if the change was from 225 to 235. These numbers represent the tread
> > width in mm, and 10mm is the functional equivelent of 3/8".
> >
> > Now, there is some misunderstanding (at least on my part) of just exactly
> > where they measure 225 or 235, and the actual tread blocks being square on
> > one tire and rounded off on the other might play a role in your perception
> > of an inch difference, but the actual difference is 10mm. Your point being
> > that you are looking at the tread patch on the ground is not lost on me ...
> >
> The 225/235 is the sectional width, not the tread width. And now that
> you mention it, I can't remember where they measure it either... and
> the actual size is always rounded off anyway. Unless the tires
> involved have exactly the same tread compounds and patterns,
> comparing traction based on section [or tread] width is a waste of
> time, as it really depends more on the pattern and compounds.

I think that is what Jeff is missing, the 'section' width vs the 'tread'
width.

It is very deceiving and I learned to only trust a tape measure for the
'actual' tread width way back in the 70's.

I just measured my new BFG AT's and the P235/75x15 tire has a tread that
is only 7 7/8" or 200mm wide.

That is a far cry from the 'book' spec of 235mm wide. Well, over 15%
difference anyway.

I also measured my son's vans tires and the P205/75x14's and the tread
width is only 165mm, not the 205mm one would think!

I have a goodyear spare that is a P235/75 15 M+S and the tread is only
180mm wide! Crap, that is a difference of 55mm or over 2" from the
'book' size!

Now if I take a caliper and measure the sidewall width at the biggest
part, (spare with no load on it) it is 235mm just like the book says.
You can hold a 3' long straight edge on both sides of the tire across
the center sticking out both ends and measure between them to get the
section or sidewall width or use a big caliper.

Mike
86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00
88 Cherokee 235 BFG AT's

Re: GC tires - 225/75 vs 245/70 (R16)
 

"Phil Schuman" <pschuman_NO_SPAM_ME@interserv.com> wrote in message
news:3VMTe.684$au2.349@newssvr17.news.prodigy.com. ..
> The Grand Cherokee OE tires are the Wrangler ST with 225/75R16 -
> I was wondering if the 245/70R16 sizes cause any probs
> with speedometer or front turning clearance under the cowling
> or any other considerations on going from the 75 to the 70 ?
> It seems like the overall outside tire diameter is the same, but ??
>
One last nagging question on the slight sizing difference -
What about the full size spare I have - 225/75R16 -
Any major concerns on running 3 tires of the alt size - 245/70R16
along with the spare that is 225/75R16 -

The diameters calc out to a difference of .216"
225/75R16 = 29.287
245/70R16 = 29.503