Can a 235/75 be used in place of a 31/10.5

Submitted: Tuesday, Oct 01, 2013 at 16:10
ThreadID: 104557 Views:4125 Replies:4 FollowUps:27
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One of my caravan tyres is legally bald because the wheel bearing was not tightened properly when it was last serviced (will do it myself in future) I have a spare Desert Dueler which is size 31x10.5 R15 LT. Can I use it on a wheel which has a 235/75 R15 LT? and how old is too old and where do I find the date on a tyre.
Thanks, Geoff
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Reply By: Shaker - Tuesday, Oct 01, 2013 at 16:36

Tuesday, Oct 01, 2013 at 16:36
Wheels & tyres on any given axle have to be the same size.
The tyre diameter difference is over 2", so no!

AnswerID: 519020

Follow Up By: Member - geoffqld - Tuesday, Oct 01, 2013 at 17:09

Tuesday, Oct 01, 2013 at 17:09
Thanks for that, looks like another good idea bites the dust.
Thanks,Geoff
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Follow Up By: philldeb - Tuesday, Oct 01, 2013 at 17:12

Tuesday, Oct 01, 2013 at 17:12
Shaker caravan axles are not drive wheels. Why do they have to be the same size
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Follow Up By: Member - geoffqld - Tuesday, Oct 01, 2013 at 17:26

Tuesday, Oct 01, 2013 at 17:26
All the van wheels are braked so I assume that could cause some problems if the diameters are different.
Geoff
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Follow Up By: Shaker - Tuesday, Oct 01, 2013 at 17:47

Tuesday, Oct 01, 2013 at 17:47
Doesn't have to be drive wheels, would you like to steer with a 2" tyre diameter difference?

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Follow Up By: Member - Boobook - Wednesday, Oct 02, 2013 at 07:20

Wednesday, Oct 02, 2013 at 07:20
Actually having wheels of different diameters will not affect steering. The main issue is a different height.

Think about tractors, the front of the tractor doesn't run away from the back. The bigger wheel will just turn more slowly. The brakes on the smaller wheel would definitely work harder though, and it's not something I would do permanently.

I looked into this a lot for my camper. I have the same wheels and tyres as the tow vehicle and 1 or 2 spares on that. When I put my bigger muddies ( 33 vs 31 inch) on, I wanted to just carry one spare most of the time and have tried it, it works fine. Tracks true. Having said that, I would only do it till I get to a tyre repair location though.

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Follow Up By: Shaker - Wednesday, Oct 02, 2013 at 08:25

Wednesday, Oct 02, 2013 at 08:25
Tractors don't have different size wheels/tyres on the same axle.
Anyway, regardless of what you say or do, the law says wheels & tyres have to be the same on each axle!
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Follow Up By: Member - Boobook - Wednesday, Oct 02, 2013 at 10:50

Wednesday, Oct 02, 2013 at 10:50
Thanks for the legal advice Shaker. I am just commenting on the fact that it does work without steering problems. I have done it. If there is no diff and connection, there is no relationship between the wheel speeds and sizes at all, even if on the same axle.
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Follow Up By: Shaker - Wednesday, Oct 02, 2013 at 15:16

Wednesday, Oct 02, 2013 at 15:16
So are you suggesting that you could put a 28" & a 33" on the front of your vehicle without affecting the steering?
Try it without power steering!

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Follow Up By: Member - Boobook - Wednesday, Oct 02, 2013 at 17:08

Wednesday, Oct 02, 2013 at 17:08
I reread my post 5 times and don't recall mentioning putting a 28" and 33" on the front of any vehicle. Or any vehicle.

Seriously Shaker, get a grip... of something else!

You have no idea what you are talking about. Best this for you to do is to remain silent, then you look smarter. LOL

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Follow Up By: Shaker - Wednesday, Oct 02, 2013 at 17:50

Wednesday, Oct 02, 2013 at 17:50
I am alluding to the fact that there must be a cut off point where it does affect steering.
As far as your personal attack, what about your dumb reference to tractors?
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Follow Up By: Shaker - Wednesday, Oct 02, 2013 at 17:53

Wednesday, Oct 02, 2013 at 17:53
Maybe I'll mention at this point, I signed RWCs in Victoria for 11 years & you can't have different size or construction tyres on the same axle, you can only have different tread pattern.
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Follow Up By: Member - Boobook - Wednesday, Oct 02, 2013 at 21:18

Wednesday, Oct 02, 2013 at 21:18
Good on you Shaker. Go for it man. You are obviously always right yeah?
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Follow Up By: The Bantam - Wednesday, Oct 02, 2013 at 22:14

Wednesday, Oct 02, 2013 at 22:14
Lets get one thing straight.

The 50mm increase in tyre size limit as discribed in VSB14 and in force on most states applies to motor vehicles and not trailers.
AS far as I have been able to establish.

The rules are far more lax for trailers.

As long as the tyres are otherwise compliant ( clearance, condition, so forth) as long as the tyres are larger ( greater diameter and or greater width) and of a higher load rating than specified on the tyre plackard if there is one....you should be fine.

NOW

start with ......is there a tyre plackard on this caravan or there is a tyre size specfied on the VIN plate....if there is, as long as the tyre is larger and of a higher load rating than specified on the plackard AND the tyres are the same size and profile..you should be fine.


235/75R15s will be smaller in diameter than 31x10.5R15s and narrower, they may however be of a higher load rating.

SO start with what is specified...if at all for that trailer.

If nothing is specified and or there is no tyreplackard...as long as the tyre is of sufficient load rating you should be fine.

There are complications like going considerably larger..like stepping from 14 inch rims to 15 inch rims associated with the de-rating of the axle for the larger wheels.

235/75R15s and 31 x10.5R15s are often run on similar sized wheels.

cheers
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Follow Up By: The Bantam - Wednesday, Oct 02, 2013 at 22:18

Wednesday, Oct 02, 2013 at 22:18
Yes tyres have to be run in pairs as same size and profile on the same axle.

cheers
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Follow Up By: wizzer73 - Thursday, Oct 03, 2013 at 09:10

Thursday, Oct 03, 2013 at 09:10
Just to throw the cat among the pidgeons, what about those spaver tyres. How can they be legal?

wizzer
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Follow Up By: wizzer73 - Thursday, Oct 03, 2013 at 09:12

Thursday, Oct 03, 2013 at 09:12
oh for an edit button. I meant pigeons and space saver tyre.

wizzer
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Follow Up By: Shaker - Thursday, Oct 03, 2013 at 12:22

Thursday, Oct 03, 2013 at 12:22
There are specific rules & limitations pertaining to the use of space saver spare wheels.
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Follow Up By: The Bantam - Thursday, Oct 03, 2013 at 21:38

Thursday, Oct 03, 2013 at 21:38
You will find that space saver spare tyres are limited in the speed they can be run at and the distance that can be run.....and that distance is not far.

like 80kmh and 200Km is common.

cheers
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Reply By: Member - Rosco from way back - Tuesday, Oct 01, 2013 at 17:11

Tuesday, Oct 01, 2013 at 17:11
+ I very much doubt you would fit a 10.5" wide tyre on the rim (which I guess would be perhaps 7" for a 235, though you don't mention the size).
AnswerID: 519025

Follow Up By: Member - geoffqld - Tuesday, Oct 01, 2013 at 17:25

Tuesday, Oct 01, 2013 at 17:25
I measured across the tread and its the same on both tyres, 235mm but the diameter is different as above.
Thanks, Geoff
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Follow Up By: Member - Scrubby (VIC) - Tuesday, Oct 01, 2013 at 19:35

Tuesday, Oct 01, 2013 at 19:35
G`day Rosco,
Mate, my 60 series L/C (March `85) has had Yokohama 31-10.5-15`s on 7" X 15" wheels since new, 350,000 klm with no problems.
Look up a tyre chart and I think you will find that a 7" width is listed for that size tyre.

Scrubby.

I don`t know where i`m going but i`m enjoying the journey.

Member
My Profile  My Blog  My Position  Send Message

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Follow Up By: Member - Rosco from way back - Tuesday, Oct 01, 2013 at 20:38

Tuesday, Oct 01, 2013 at 20:38
You are correct of course. Serious brain fade here. I'm running stock 265 on stock 7" rims ..... doh!!
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Reply By: Ron N - Tuesday, Oct 01, 2013 at 20:20

Tuesday, Oct 01, 2013 at 20:20
Geoff - A 31 x 10.5 R15 is the equivalent of a 265/75 x R15. Here are the two tyres specifications ...

31 x 10.5 R15 LT

Sidewall - 198.8mm
Radius - 389.2mm
Diameter - 778.5mm
Circumference - 2445.7mm
Revs per km - 409

235/75 R15 LT

Sidewall - 176.2mm
Radius - 366.8mm
Diameter - 733.5mm
Circumference - 2304.4mm
Revs per km - 434

So you can see there's a fair difference in diameter and width (45mm and 30mm).

Putting the 31 x 10.5 R15 on one side with a 235/75 R15 on the other side will tilt the van a little and throw the C of G off-centre a little - but probably not enough to affect handling and braking any noticeable amount.
I personally, would only consider doing this though, as an emergency measure.

As previously stated, the law states that tyres on one axle shall be the same size each side - and a sharp-eyed cop would probably pick up the difference, meaning you'd be booked.

Tyre life is generally recognised as being 6 years - however, well-cared-for tyres (kept out of the sun) will generally be good for 10 yrs or a little more.
Look for fine crazy cracking in the sidewall and tread as an indicator that the rubber is "ozoned", and becoming hardened, and at the end of its life.

Tyre dating method can be found here ...

http://www.tirerack.com/tires/tiretech/techpage.jsp?techid=11

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Follow Up By: Shaker - Tuesday, Oct 01, 2013 at 20:38

Tuesday, Oct 01, 2013 at 20:38
........ and an even sharper eyed insurance assessor!

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Reply By: Penchy - Wednesday, Oct 02, 2013 at 07:27

Wednesday, Oct 02, 2013 at 07:27
define "legally bald"
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Follow Up By: Ron N - Wednesday, Oct 02, 2013 at 10:50

Wednesday, Oct 02, 2013 at 10:50
Legally bald is tread depth less than 3mm or approximately one-match head thickness, in the old rough and ready measurements.

If the tyre has tread depth markers - as many do today, then the markers level with the tread indicate 100% worn.
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Follow Up By: Penchy - Wednesday, Oct 02, 2013 at 11:10

Wednesday, Oct 02, 2013 at 11:10
I see what you are saying, but a tyre is either legal, or not legal, bald is not legal. If it is past the markers it is illegal, if it not past, it is not legal.
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Follow Up By: landseka - Thursday, Oct 03, 2013 at 10:12

Thursday, Oct 03, 2013 at 10:12
NOW I have heard everything!

Thanks Penchy, I like a laugh every day and now I have already had today's.
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Follow Up By: Penchy - Thursday, Oct 03, 2013 at 11:06

Thursday, Oct 03, 2013 at 11:06
Glad to help out the simple folk.
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Follow Up By: Ron N - Thursday, Oct 03, 2013 at 13:00

Thursday, Oct 03, 2013 at 13:00
Ah-ha! - but you can do things that are illegal, but still safe to do.

Or you can do things that are unsafe, but not illegal.

When I chided an old mate about doing something illegal with his truck one day - he said - "I've been illegal all my life!! - and I'm not about to start becoming legal, now!! LOL
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