Tyre sizes....

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Badger

Badger

Well-Known Member
Posts
4,669
Location
Marldon, Devon
Oki oki, calm the fook down, a genuine question here which hasn't been covered that i can find.

After chatting with a neighbour of a job i was on, we were talking about me landy and he tells me he's got some old wheels his son left behind when he moved away with some off road tyres on. As my ears perked up i began to dig a little deeper and he tells me to pop round and see if they're any good to me, so not to look a gift horse in the mouth, i went into his garage today....

He's got a pair of black modular with 32 11.5 tyres on them and i can have them as well as another rim for £50.

Now my rear tyre got a flat spot at the bottom due to a screw puncturing the sidewall some weeks ago so i've been running a spare which is a road tyre to my current 225x75x16's.

My question is ( and you're gonna love this ) can i whack the modulars on the rear and keep my standard GG AT2's on the front till i win the lottery and can get another modular for the front and another pair of rubbers for them?

I'm not bothered if it looks odd for abit, just thinking is it going to upset the running at all...i'd leave difflock alone whilst in this set up, but it would be abit more balanced than the one road tyre i have atm and it seems a waste to let these go.

Another bonkers moment for me?
 
Your existing tyre is approx 29" diameter. ie 2" smaller roughly 9% smaller. Suggest the different road speeds may damage transfer box but I am sure somebody will shoot me down in a while.
 
That was my thoughts tbh. They'll have to sit there for abit me thinks, money has to be diverted elsewhere before a new pair of rubbers for the front.
 
Having another think about it, what about lower pressure in the larger wheels to bring the diameter to a smaller size....
 
sible88 said:
Wouldn't suggest it tbh shouldnt any harm but don't take my word
Click to expand...

:0 .... see point 'b'

couple of points....

a) i assume the tyre pressure comment is a joke to get a bite as surely nobody in their right mind would suggest that if the car is ever going to be used on a road you would do that, to get a 2" change you would need a big difference if it could be done and id expect the CPS to get you a long stay in a small room complete with tv and xbox in the event of a serious rta.

b) if the tyres are as stated 32x 11.50 then they are crossply (ie no 'R') your AT2's will be radial,

just a minor issue (not) but it is very very dangerous and very very illegal to fit radials up front and crossplys on the rear :0 amazed nobody mentioned this straight away ???

cheers steve
 
have a look here for an old but applicable Public Information Film....

[ame=http://www.youtube.com/watch?v=c23MFIKiVdE]Crossplys and Radials Don't Mix - YouTube[/ame]

Guess they no longer bother as there are not that many cross ply users out there anymore??

Cheers Steve
 
ebbadger said:
:0 .... see point 'b'

couple of points....

a) i assume the tyre pressure comment is a joke to get a bite as surely nobody in their right mind would suggest that if the car is ever going to be used on a road you would do that, to get a 2" change you would need a big difference if it could be done and id expect the CPS to get you a long stay in a small room complete with tv and xbox in the event of a serious rta.

b) if the tyres are as stated 32x 11.50 then they are crossply (ie no 'R') your AT2's will be radial,

just a minor issue (not) but it is very very dangerous and very very illegal to fit radials up front and crossplys on the rear :0 amazed nobody mentioned this straight away ???

cheers steve
Click to expand...

Nice to see those replying have amazed you enough to use large wording and colours too, the information you have given will possibly be quite informative to those who aren't as educated in these matters as yourself, including me.

however it's a shame you're such an arse at showing it.
 
Badger said:
Nice to see those replying have amazed you

however it's a shame you're such an arse at showing it.
Click to expand...


sticks and stones :) but if it saves a life Im hardly worried

And by the sound of things it may be more than informative, it may well prevent a tragedy so Bold, red, large, flashing and with a hooter would probably be better, otherwise somebody such as yourself may miss what is an essential piece of advice when glancing through the replys

Clearly my method of getting the information across has worked as this will stick in your mind whereas regular type may have been missed or disregarded... so feel free in future to think ahh I cant mix those tyres because of what that arse said, as I said if it keeps people alive I can live with it :)

and as a road user its your job to know what is illegal and downright dangerous, mix tyres and kill someone then itll be a long stretch in a small room with bars only an xbox and sky tv for company and the excuse I didnt know doesnt work... so you can thank this arse for also potentially keeping you out of jail.... God Im helpful :)

as is the suggestion to run incorrect pressures to correct a 2" difference in rolling radius... I assumed that was a joke, now you have really amazed me


:)

Steve
 
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After spending 30 minutes on the good ol' internet:

What does the law say?
REGULATION 25: This Regulation is concerned with the tyre's load index and speed ratings. It specifically deals with items such as the tyres fitted to Goods Vehicles, Buses and Trailers and for which a Ministry Plating Certificate must have been issued, and a Ministry Plate attached to the vehicle. Amongst other vehicle information the Plate, which must be securely attached to the vehicle in a conspicuous location, gives the maximum axle and gross vehicle operating weights. The Regulation requires that the tyres fitted to the vehicle are not only capable of supporting the maximum permitted load on each axle but of doing so at the vehicle's maximum legal speed. In defining 'load-capacity index' and 'speed category' the Regulation makes reference to UN ECE Regulations 30 and 54 and to the European Union Directive 92/23/EEC.

REGULATION 26: Deals with the mixing of tyres of differing structures. The regulation defines three types of tyre structure, diagonal ply (Crossply), bias-belted and radial. No vehicle shall be fitted with tyres of differing structure on the same axle. For cars and vans (even with twinned rear axle), the following are the LEGAL tyre combinations. Mixing of a temporary spare tyre on a car is allowed, provided it is not driven at a speed exceeding 50mph.

Front Rear
Diagonal ply (Crossply) Diagonal ply (Crossply)
Bias belted Bias belted
Radial Radial
Diagonal ply (Crossply) Bias belted
Bias belted Radial
Diagonal ply (Crossply) Radial





REGULATION 27: Deals with the condition and maintenance of tyres. It specifies when a tyre should not be used on the road due to for example: it not being suitable for the use to which the vehicle is being put, or issues relating to its condition or maintenance, such as inappropriate tyre pressures, cuts, bulges or tyre damage. It also allows the use of run flat tyres when in a deflated state provided the tyre and wheel are so constructed to be fit for the use to which the vehicle is being put. This Regulation also specifies that the grooves of the tread pattern of every tyre fitted to cars and light vans shall be of a depth of at least 1.6mm throughout a continuous band comprising the central three quarters of the breadth of tread round the entire circumference of the tyre.
In accordance with these rules, look under the heading 'Tyre selector' for the alternatives offered by MICHELIN for each vehicle model.
Click to expand...

Have a read of section 26, although they do state:

Never mix radial and non-radial tyres
Do not mix radial and non-radial (i.e. cross-ply or bias-belted) tyres on a vehicle. If mixing tyres is unavoidable, never mix radial and non-radial tyres on the same axle. If two radial and two non-radial tyres are installed on a vehicle, the two radials must be installed on the rear axle and the two non-radials on the front axle.
Click to expand...

You can find the information above here:

When should I change my tyres? | Buying Guide | | Learn and Share | MICHELIN

Digging a little further i was interested in what the guidelines were for MOT testers regarding this, some interesting reading:

Method of Inspection:
Type of structure, ie bias-belted, cross-ply or radial.

Note: Steel and fabric radial-ply tyres are to be regarded as the same structure type.

Reason for rejection:

a. one tyre is of a different type of structure from another tyre on the same axle

b. a 3- or 4-wheeld vehicle fitted with single wheels, and

i. a cross-ply tyre or bias-belted tyre fitted on rear axle and radial-ply tyre is fitted on front axle, or

ii. a cross-ply tyre fitted on rear axle and a bias-belted tyre fitted on front axle.

Note: Any tyre ‘type’ mix between different axles is acceptable for vehicles that have

. 2 axle and ‘twin’ wheels on the rear axle

. 3 axles, one steering and one driving

Note: This does not apply to vehicles with an axle fitted with tyres having a road contact area at least 300 mm wide.

c. a tyre of a different type of structure is fitted to a steerable axle from that fitted to another steerable axle

d. In the case of non-steerable axles a tyre fitted to a driven axle is of a different type of structure from that fitted to another driven axle
Click to expand...

Information link here: MOT Testers Manual - tyres

It is an MOT failure to run radials on the front and another type on the rear, but the other way around ( radials on the rear ) is legal and deemed ' road worthy ' by MOT standards.

It does seems to be a grey area as such, legally you can run different ' construction types ' of tyre as long as none are different on the same axle & radials are at the rear, but there's plenty of chatter on the internet regarding running different sets of construction types and whether it's safe or not, but from what i've read alot of it is pointing towards higher speed vehicles ( above 50mph ), but it's a personal choice i guess ;)

If i was to run this set up, i would need to run the larger tyres on the front and the others on the rear, but could still have an issue with the transfer box....





=: This post was brought to you with concise accurate links, lack of large letters, colours, xbox's & tvs :=
 
congratulations 30 mins on the net and a huge post to confirm what i said about radials front and crossplys rear is illegal, plenty of good info but what you will find is people cant be arsed to read such a long post so your work will be in vain

might i suggest you highlight the pertinant points in bold and red to make it easier for the casual browser to see the important bits amongst the irrelevant drivel, I would hate people to miss out on the useful stuff you have found confirming my earlier post :)

I and you could have also gone into tread depths, recuttable tyre laws etc etc but i felt simply explaining the errors that could get people killed the best approach

Its something we teach when instructing on power point, dont post a slide full of info as it distracts, simply post bullet points as they have more impact and are then remembered... case and point proven with my initial post I feel....

as you will notice none of this is bold or coloured as its not important and if people glance over it they will not be missing anything of particular importance

still Im glad you took the time to confirm my initial post as it adds extra weight should anyone have not believed me...

Cheers Steve
 
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