Tyre sizes

Submitted: Friday, Aug 01, 2003 at 12:08
ThreadID: 6304 Views:3192 Replies:9 FollowUps:14
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Can anyone (Diamond - you legend?) explain to me the difference between the 265/70 R16 tyres on my ute and 265/75 R16 tyres on my off road camper. I would like to have identical tyres on both but am not sure if this is possible."Live today as if there may be no tomorrow"

Wombat
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Reply By: PJ - Friday, Aug 01, 2003 at 12:30

Friday, Aug 01, 2003 at 12:30
I think the two end dimensions (70 & 75) referrs to the profile of the tyre: distance from bottom of tyre to rim (width of rubber basically).
AnswerID: 26521

Follow Up By: Member - Rohan K - Friday, Aug 01, 2003 at 17:14

Friday, Aug 01, 2003 at 17:14
The tyre's profile (65, 70, 75 etc) refers to height of the sidewall as a % of the width.

So a 265/70 has a sidewall height of 185.5 while a 265/75 has a sidewall height of 198.75. All things being equal (brand, model, inflation, etc) the total extra diameter between the two tyres is 26.5 mm.

Have a look in the archives, and also here Overlander forumSmile, you're on ExplorOz
Rohan (Sydney - on the QLD side of the Harbour Bridge)
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FollowupID: 18174

Reply By: crowe - Friday, Aug 01, 2003 at 12:30

Friday, Aug 01, 2003 at 12:30
Wombat,

The trailer tyres have a slightly higher sidewall and hence will have slightly higher diameter. The 75 is basically a percentage of the width so 75 tires will have a sidewall height of approx 198mm (265 x 0.75) whearas the 70 tires will have a height of approx 185mm (265 x 0.7). This is how i understnad it, if wrong someone please correct me. IMHO the slight diffeence wouldnt be worth worry about, as long as the track and width are right it should be good enough.

crowe
AnswerID: 26522

Follow Up By: Member - Rohan K - Friday, Aug 01, 2003 at 17:21

Friday, Aug 01, 2003 at 17:21
Crowe, this is correct provided all other things (brand, model, inflation etc) are equal. In the great search for information to support my choice of tyre, without requiring an engineer's cert, I have discovered that there are vastly different "rolling" circumferences between makes and models of tyres in the same size. So, mixing and matching different brands and models as well as sizes, could result in a significant difference, in rolling circumference, for the purpose of interchaneability.

A 4% difference in RC based purely on the diff between a 70 and 75 profile of the same tyre probably wouldn't cause too many problems as long as there was sufficient wheel slip to equalise the wheel revolutions. Using a diff-lock would change this equation somewhat.Smile, you're on ExplorOz
Rohan (Sydney - on the QLD side of the Harbour Bridge)
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FollowupID: 18176

Follow Up By: Member - Rick - Friday, Aug 01, 2003 at 20:28

Friday, Aug 01, 2003 at 20:28
the problem with this theory is simple.tyres of a different diameter on the same axle will cause accelerated wear on the outside edge of the smaller diameter tyre, as well as place strain on the diff centre.
(think about it...) :)
running them on dirt for a short period would be ok, but go near bitumen and things will wear very quickly. thats why we rotate our tyres every 5k, so that every one of them wears down evenly.
as the saying goes in the world of tyres,,,,don't mix and match...
sell the ones off the camper ort 4by and get ones that match the tyres you keep..

rick.
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FollowupID: 18192

Reply By: Outnabout David (SA) - Friday, Aug 01, 2003 at 12:52

Friday, Aug 01, 2003 at 12:52
Wombat,

The above is correct. The diameters and rolling circumferences will be different.
If you want the tyres and wheels to interchange between camper and vehiclke then that may be a problem especially if constant 4wd.We have so little time to enjoy our land
AnswerID: 26526

Reply By: Member - Wombat (Vic) - Friday, Aug 01, 2003 at 13:04

Friday, Aug 01, 2003 at 13:04
I think I've got my head around it. The obvious next question is: Can I fit the higher profile (265/75) tyres (legally) to my Triton? I assume this will give me the advantage of a 13mm lift? . . . . and do Cooper ATs come in a 265/75 R16 LT size?

Thanks for the help guys."Live today as if there may be no tomorrow"

Wombat
AnswerID: 26528

Follow Up By: crowe - Friday, Aug 01, 2003 at 13:51

Friday, Aug 01, 2003 at 13:51
need to multiple 13mm by 2 for both sides of the tire so in essence it will be approx 26mm lift, 13mm on one side wall and another 13mm on the opposite side wall
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FollowupID: 18145

Follow Up By: GaryInOz (Vic) - Friday, Aug 01, 2003 at 14:45

Friday, Aug 01, 2003 at 14:45
Lift WILL be 13 mm (ground to axle, 185mm vs 198mm sidewall height + half the 16 " rim), other 13 mm will be "guard filler", therefore overall 26 mm larger diameter tyre.
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FollowupID: 18156

Follow Up By: Member - Wombat (Vic) - Friday, Aug 01, 2003 at 14:53

Friday, Aug 01, 2003 at 14:53
I nearly made the same boo boo crowe. But of course any additional height is only gained from the radius below the centre."Live today as if there may be no tomorrow"

Wombat
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FollowupID: 18160

Follow Up By: Hugh - Saturday, Aug 02, 2003 at 01:03

Saturday, Aug 02, 2003 at 01:03
Wombat,

Yes, Cooper sell the AT in 265/75/16LT size. I have these on my Patrol and they are great, good grip for the off-roading I do, excellent in sand and also quiet on road.

The following link will let you make up your own mind and specific pages show all the dimensions you ever wanted to know about tyres, certainly enough to answer all your questions.

www.coopertires.com.au

Regards,
Hugh

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FollowupID: 18211

Reply By: Member - Andrew O - Friday, Aug 01, 2003 at 13:12

Friday, Aug 01, 2003 at 13:12
Wombat,
265/75R16 tyres are very widely available - its the standard size for a cruiser. There are regulations about tyre size, I cant recall exactly what they are, but having seen them before, and this change is ok ... I'm planning on doing the same change to my Patrol on the next tyre change.
Cheers
So much to see, too little time ...
Andrew
AnswerID: 26530

Follow Up By: Truckster (Vic) - Friday, Aug 01, 2003 at 13:49

Friday, Aug 01, 2003 at 13:49
15% of standard you can go without causing problems.

if in doubt Vicroads site has ALL the info on there, if u can find it.
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FollowupID: 18144

Reply By: Member - Fred - Friday, Aug 01, 2003 at 14:22

Friday, Aug 01, 2003 at 14:22
Cooper info I have says 265/70/16 has outside diameter of 30.40 inches
P 265/75/16 has outside diameter of 31.50 inches
LT 265/75/16 has outside diameter of 31.60 inches

Hence lift will be 0.55 inches or about 13 mm - speedo wil change by about 4% - s
Suggest Crowe do the sums again
AnswerID: 26541

Reply By: diamond (bendigo) - Friday, Aug 01, 2003 at 20:31

Friday, Aug 01, 2003 at 20:31
gday wombat.
checked sizes for you today.
all sizes are aproximate only will vary fron tyre to tyre but not to much
your triton came out with 265/70/16 wich has overall diameter of 772mm
265/75/16 haave an overall diameter of 803mm.roughly 32"
the actuall vic roads law is 15mm not 15% so legally you cant run 265/75/16.
theres not to much choice for the triton.
only other option is 245/75/16 if you have 6.5" rims min.
hope this is some help to you.
ps do you know what a legend is.
acording to dr harry cooper.
its a small gland that lubricates a dogs bum so it can you know what.
its called a legend gland lololol.
new job coming so no fraser this time:-((
AnswerID: 26574

Follow Up By: Member - Wombat (Vic) - Monday, Aug 04, 2003 at 11:40

Monday, Aug 04, 2003 at 11:40
I'll think twice about calling someone a legend again! I wonder if Dr Harry's a legend? I spoke with Coromal with regard to getting Coopers on the camper on delivery but they say no go - she only comes with Bridgestone ATs. So if I can ask one more question; Should I put the legal 265/70/16s on the Triton and then replace the original Bridgestones on the trailer with the same tyres to get a match and if I did this do I trade the three brand new Bridgestones in or sell them privately?

Thanks for the help.

PS I wonder if any Vicroads inspectors would which tyres are larger than legal?"Live today as if there may be no tomorrow"

Wombat
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FollowupID: 18271

Follow Up By: diamond (bendigo) - Monday, Aug 04, 2003 at 13:45

Monday, Aug 04, 2003 at 13:45
gday wombat.
my chooice would be just keep the 265/70/16 on your triton.
if you want to change the tyres on your camper just so you have extra spares i would sell them privately.
i run 31" on my patrol and 30"on the camper and have one spare for the patrol and one spare for the camper.
if worst came to worst i9 would just fit the 30" to the front of the patrol if i needed to.

ps most peoplpe at vic roads wouldnt have a clue about tyre sizes but they have a group of coppers who have been trained to know the roadworthy laws(there was 10 there when i did my course).
and of course your insurance company.got over no fraser.
get on with life(more weekend fun)
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FollowupID: 18282

Follow Up By: Member - Wombat (Vic) - Monday, Aug 04, 2003 at 13:55

Monday, Aug 04, 2003 at 13:55
Thanks for the great advice which I shall take. What should I pay for five Cooper 265/70/16 ATs and is your new place of employment a Cooper agent?"Live today as if there may be no tomorrow"

Wombat
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FollowupID: 18283

Follow Up By: Member - Wombat (Vic) - Monday, Aug 04, 2003 at 13:56

Monday, Aug 04, 2003 at 13:56
Hit me offl forum if you prefer;
Paul
at
backhouse-thomas
dot
com
dot
au"Live today as if there may be no tomorrow"

Wombat
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FollowupID: 18284

Follow Up By: diamond (bendigo) - Tuesday, Aug 05, 2003 at 19:42

Tuesday, Aug 05, 2003 at 19:42
gday wombat.
you should be paying about $245-250each for your tyres.
that seems about the average price.
just remember to screw the tyre place for free rotatio/balance.
might be the only thing that decides where you buy them.got over no fraser.
get on with life(more weekend fun)
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FollowupID: 18392

Reply By: Leroy - Saturday, Aug 02, 2003 at 01:24

Saturday, Aug 02, 2003 at 01:24
Wombat,

I don't think the trailer will be bothered if it had odd tyres on if you had to use a spare from the Triton.
I think the Trinton would have something to say about using the trailer spare though!!

Leroy
AnswerID: 26602

Reply By: Leroy - Saturday, Aug 02, 2003 at 01:25

Saturday, Aug 02, 2003 at 01:25
Wombat,

I don't think the trailer will be bothered if it had odd tyres on if you had to use a spare from the Triton.
I think the Trinton would have something to say about using the trailer spare though!!

Leroy
AnswerID: 26603

Follow Up By: Member - Wombat (Vic) - Monday, Aug 04, 2003 at 11:43

Monday, Aug 04, 2003 at 11:43
Yeah the poor old Triton would look like a limping wombat. Hey I thought you guys would have been off by now enjoying the peace and quiet. When do yo leave? "Live today as if there may be no tomorrow"

Wombat
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FollowupID: 18272

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