Sunday, Sep 02, 2007 at 00:40
FIDLIM
The placard normally doesn't have a weight spec on it as the OEM has no idea what you are going to load the vehicle with.
Your vehicle will have GVM spec on the compliance plate which for a 75 series Troopy is around 3100kg.
If you break that down to 1000kg for the front axle and 2000kg for the rea axle you will be very close to the engineered limits.
This is where you get your minimum tyre weigt from.
Eg. rear axle 2 x 1000kg = 1000kg for each wheel as this is where your OEM load weight corresponds to excluding vehicle modificatiuons.
On the tyre chart 1000kg = load rating of 108
and increases in approx 30kg increments
eg.
1030kg = 109
1060kg = 110
etc etc
If you pick/choose a rating of 1000kg you are a dill and living on the edge
The lettering is the speed rating od the tyre and you can work that one out for yourself.
What do I do for tyres - easy.
Firstly I look for the tyre tread pattern I want and then check to see if the tyre has rim edge protection ie rubber bead edge extends/protrudes out over the edge of the rim.
Then I look for the Load Rating and never get one under 116 and/or speed rating less than N
Why, because I have had the Troopy re-engieered for GVM which is now 3495kg and I like to have a safety margin.
Then I look at Side wall construction - self explanatory.
Then we go to sizes.
Mine had 16in rims so it gets 16in tyres regardless of the fact that 15in will fit. OEM specs are based on 16in so that is what it gets.
Mind you I have had a 15in on there once as a make shift to get back to civilisation.
Tyre size - from memory you increase the dia by 15 mm and the width by 25mm and still be legal.
There is a national change to one code spec for allowable tyre size increases over OEM specs, however I don't think it has been adopt by the states as yet.
So for you
OEM 7.50 R16 31 10.50 R15
Dia 803mm 786mm
height 198mm 202mm
Width 191mm 267mm
Speed 100Kph 102 Kph
Load Rating 109
You have gone for extra width haven't you - at lowest cost. Good idea however in this instance my thoughts are as follows.
(1) 109 load rating is just within minimum and I have never ever seen a true 4WD thats off road and within the Max Load specs. Just a fact of life, you carry heaps of chit
(2) Width is approx 50mm over whats allowable to increases to OEM specs.
These two areas are where the safety, insurance and roadworthy aspects come into question.
Have a good week end and dream tyre size, vehicle specs and what is and is not legal.
AnswerID:
259917
Follow Up By: fidlim - Sunday, Sep 02, 2007 at 10:27
Sunday, Sep 02, 2007 at 10:27
Hi hi,
not greedy and trying to save money but
1) when I bought the truck it had 2 sets of
wheels 4pcs 16''x7 sunraysias with 7.5s on them -1-0mm left on them 1pc of split rim with desert dueler 7.5 roadworthy and then 5 pcs of 15'' with roadworthy 31'' M/Ts but some cuts and scuff and grazemarks on the sidewalls and not very reliable looking.
So to prevent sliding across the
intersection sideways with blownout tyre I went for compromise meaning 31'' desert duelers cheap but reasonable quality.
I always wanted 235/85R16 but I am unsure what rims to choosse as it is very hard to find 1 or 2 16x7 six stud sunraysias for good price and I don't want to go back to splitrims or having just the spares on splitrims (I suppose you can do that).
The 265/70R16 is another option as the diameter is exactly the same as 7.5R16 but the incrase in widht scares me a bit which does not make much sence after all because these are approximately the same widht as the 31'' tyres. But then the load index is much pleasent to look at.
Speed I am not worried about as this is not an F1. max on highway 110 S rating is way over that as far as I know 180kph
FollowupID:
521381
Follow Up By: Member - Davoe (Nullagine) - Sunday, Sep 02, 2007 at 16:20
Sunday, Sep 02, 2007 at 16:20
I dont get it - you say the vehicle had 4 16x7 rims and one 16 inch splitty
so why not just buy 4 decent 235x85 10 ply tyres such as Goodyear MTR or you can fit 265x75 on a 7 inch as
well. Both are the same diametre so your splitty can be a spare no matter which way you go.
Dont wast your time with 15s they are 6 ply construction usually and are not suitable for loaded 4bys as they just "pop" when driving on stony roads, tread fractures and down they go - quickly
FollowupID:
521408