Chris200100
Member Since: 22 Mar 2006
Location: Nr Cardiff
Posts: 532
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Theres been a few post about AT tyres and load index's etc,
this morning I have looked into all this due to the fact that i'm after a set of General Grabber AT2's for my 18" wheels the correct size 255/60/18 arn't due out untill early next year.
There is 255/55/18 available but the load index on these tyres are 109 and LR recomend 112 for the D3 plus the profile is a little smaller.
Having looked into this and cooking my head a few times i've found the the load index of 109 = to 1030kg per tyre and the rule to work out what load index you need is to divide the gross weight of the car by 4 and add 20% for a safty margin,
The D3 comes in at 969kg so a tyre with a load index of 109 is within spec.
The mot people work it out a little diffrent they use the gross axle weight of the car and depending how many tyres per axle 2 or 4 they times the tyre load index by 2 or 4.
Now the RRS's 18" wheels use tyre of 255/55/18 load index of 109.
now the gross axle weight of the RRS is 1470 KG Front and 1710 KG Rear
the D3's are 1450 KG Front and 1875KG Rear.
The RRS and the D3's axle weight arn't a millon mile from each other so why such a dramatic diffrence in tyre load index weight??
The 255/55/18 tyres load index weight time 2 is 2060KG as you can see the axle weights are well within this weight.
I know LR warranty may be a problem.
I would like your comments on this issue and if anyone can see anything I missed out please let me know.
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 9th Aug 2006 12:32 pm |
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dylansdad
Member Since: 04 Apr 2006
Location: Solihull
Posts: 745
  
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There are 2 questions that come to mind for me.
a) the expected use of the vehicle could have some bearing on the amount of allowance?
b) I would expect the fully laden weight to be an issue, if the D3 is a 7 seater and the RRS a 5 then surely there needs to be allowance for the fact 7 fat blokes in a D3 will weigh far more than 5 in an RRS  2004 TDV6 HSE Auto Zambezi Silver
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| 9th Aug 2006 1:12 pm |
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Chris200100
Member Since: 22 Mar 2006
Location: Nr Cardiff
Posts: 532
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good point about useage of the vehicle didn't think of that one.
As for your second question tho a very good point I was looking at the max gross weight of the vehicle and max gross axle weight which is the max the vehicle will take fully loaded etc when I was working the tyre index weight's out.
the max EEC kerb weight is lower at 2718kg
which gives you axle weights of 1302kg front, 1416kg rear
EEC kerb weight includes, fluids,tools,spare, and 75kg driver.
thats whats in the D3 brochure.
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| 9th Aug 2006 2:40 pm |
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dylansdad
Member Since: 04 Apr 2006
Location: Solihull
Posts: 745
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fair enough, but if i were responsible for specifying components like this I would look at factors such as the max amount of weight the vehicle could carry. In this case allowing only for the driver would be an oversight given the difference between fully popluated vehice and 1 driver = 6 x75 = 450Kg !!
I am by no means an expert in tyre specification or the tchnicalities of vehicle design, just my opinion. hopefully a real 'expert' will appear and give us the answer. 2004 TDV6 HSE Auto Zambezi Silver
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| 9th Aug 2006 3:47 pm |
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Slimer
Site Moderator
Member Since: 06 Jan 2005
Location: Last Exit to Nowhere
Posts: 16295
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At a guess the load index figure is for a new tyre so it probably reduces during use (and abuse), quite possibly this is factored in when stating the minimum rating for the vehicle so it's still up to the job all the time it's still legal. Just speculation but it seem to make sense (in my head anyway)  The End
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| 9th Aug 2006 4:09 pm |
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dflo
Member Since: 04 Jul 2006
Location: Wading in and out of it...
Posts: 1361
 
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You lot are depressing me with all this talk of 75Kg drivers 
Pass me another lettuce leaf... "Funny, mine doesn't do that......."
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| 9th Aug 2006 4:10 pm |
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DG
Site Moderator
Member Since: 12 Dec 2005
Location: The Gaff
Posts: 50934
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Yer you can add another 20kg on for me
Chris, as Si's head has already said in a roundabout way ....the load index states 112 for 18" and thats that....I was ready to buy them on Monday after LR insurance gave the OK but Si's head (again ) advised me otherwise. Insurance clearance is one thing but invalidation of warranty is a big other. I'm still flying a flag for MTR's but I need the 5 x 19" rims first ...but if the right sized AT2's do come along before Christmas then I would seriously consider them then  21 year LR veteran > D2 GS 2003 > D3 S 2006 > D3 HSE 2009 > D4 HSE 2013 > D4 HSE 2015 > D5 HSE 2018 > DS HSE R-Dynamic P300e 2021
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| 9th Aug 2006 5:05 pm |
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Chris200100
Member Since: 22 Mar 2006
Location: Nr Cardiff
Posts: 532
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After some more searching on the net it seems that the profile of the tyre and the load index are related. The lower the profile the lower the load index and as long as this is above the fully loaded weight of the vehicle then it seems to be fine.
This was on a tyre manufacturer web site.
after more working out using max weight that the D3 is capable of (thats fully loaded etc which is 3230KG)
divided by 4 gives you 807.5KG plus a 20% safty margin (as recommended) comes to 969KG.
tyres with a load index of 109 are rated to 1030KG.
so there seems to be a safty margin of 27.5% on tyres with a load index of 109.
So it seems that it is possable to use the 255/55/18 with a load index of 109.
The LR warranty could however be a concern if something were to happen and it was related to the tyres.
However due to the fact that both the D3 and the RRS share the same drivetrain etc and the RRS uses the 255/55/18 tyres as standard, then the drivetrain should be able to cope with the lower profile tyres.
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| 9th Aug 2006 5:12 pm |
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Chris200100
Member Since: 22 Mar 2006
Location: Nr Cardiff
Posts: 532
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Fair comment dick however after looking into it in more detail and cooked my head a few times.
I am more than likely to go for the 255/55/18's and give them a go.
I was looking at getting 5 x 19 with MTR's however the cost of getting 5 new wheels and tyres.
The boss didn't like the idea of spending that amount when I can get 5X AT2's for £500, tho I will need to get a full size spare aswell but one wheel is cheaper than 5
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| 9th Aug 2006 5:20 pm |
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DG
Site Moderator
Member Since: 12 Dec 2005
Location: The Gaff
Posts: 50934
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If you can convince me that there are no warranty issues then I could be persuaded. 
Make sure you tell your insurers and get them to make a note on your file. 21 year LR veteran > D2 GS 2003 > D3 S 2006 > D3 HSE 2009 > D4 HSE 2013 > D4 HSE 2015 > D5 HSE 2018 > DS HSE R-Dynamic P300e 2021
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| 9th Aug 2006 5:45 pm |
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Chris200100
Member Since: 22 Mar 2006
Location: Nr Cardiff
Posts: 532
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yeah I will do,
As for warranty they would have to proove that the tyres caused the fault.
which in my experience with LR dealers they probably won't notice the tyres, they havn't picked up the fact I got USA xenons on the car and it been in there a few times with them on.
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| 9th Aug 2006 6:16 pm |
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dylansdad
Member Since: 04 Apr 2006
Location: Solihull
Posts: 745
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based on what we know of UK Insurers, you can be sure that even if you advise them you were putting tyre load index XXX on the vehicle they wouldnt check this against the manufacturers spec. untill it came to a claim, in which case you would have fitted tyres what were outside the manufacturers specification and therefor they wouldnt pay out. I would hate to think what sort of implications this would have on liability should you be in an accident and a 3rd partys insurer found you were out of spec. 2004 TDV6 HSE Auto Zambezi Silver
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| 9th Aug 2006 6:54 pm |
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DG
Site Moderator
Member Since: 12 Dec 2005
Location: The Gaff
Posts: 50934
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If the insurer accepts a modification and this is recorded then all will be well. I made sure the lassie typed the details into my policy notes as I was having the conversation.
It is worthwhile getting this info in writing though too, I guess 21 year LR veteran > D2 GS 2003 > D3 S 2006 > D3 HSE 2009 > D4 HSE 2013 > D4 HSE 2015 > D5 HSE 2018 > DS HSE R-Dynamic P300e 2021
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| 9th Aug 2006 8:22 pm |
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Ken
Member Since: 20 Feb 2006
Location: Here
Posts: 10865
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dickgriff wrote:Yer you can add another 20kg on for me
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| 9th Aug 2006 8:28 pm |
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DG
Site Moderator
Member Since: 12 Dec 2005
Location: The Gaff
Posts: 50934
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Something tickling those ribs there Ken .....  21 year LR veteran > D2 GS 2003 > D3 S 2006 > D3 HSE 2009 > D4 HSE 2013 > D4 HSE 2015 > D5 HSE 2018 > DS HSE R-Dynamic P300e 2021
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| 9th Aug 2006 8:53 pm |
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