Legal (?) tyres to suit 5.5 Defender rims.

[twisted leader]

Currently run 235/85/R16 Cooper's on my 1996 Defender (5.5" rims) but was told that they are not legal and may be an issue if I had to make an insurance claim. The Cooper site says that I can use 235/70/R16 but all my searching on the net says you can't run 235's on 5.5 rims. Any advice on what is the maximum tyre size I can use on the standard rims?
Thanks... David

[87County]

what does your tyre placard/owner's manual indicate ?

[87County]

If you take the choice of running D1 wheels, as many defer owners have, you can satisfactorily go up to 235 85 16s - AND you can run them tubeless - another definite advantage. This size closely replicates the circumferencial dimension of the standard 7.50X 16 tyre.

If you go up to 255 85 16s on D1 rims you'll then find that the gearing is a lttle bit too tall for comfortably driving the standard 300tdi/R380 combination.

[Jeff]

The problem with 235/85-16s is tyre manufacturers give different information, some saying it is a direct replacement for 7.50-16 while others say you can't and it has been on here very much with both replies. It seems to rear its ugly head every time someone mentions 235/85-16.

I think D1 rims look terrible on a Defender, the biggest problem with the original rims is the lack of a safety bead, and despite many people having done it, you shouldn't run tubeless. If I could cut the centres and weld them to some rims with a safety bead and a little more width, I would. Now there's a plan.

Jeff

:rocket:

[Slunnie]

I would be looking to be guided by the tyre manufacturers guide. There is a little bit of variation sometimes between manufacturers rim width requirements.

[alex.com]

Hi my name is Alex this is my first entry on this forum. I bought my first landrover a 1998 defender 130 less than a week ago. I bought this car unregistered and after much work now have it licensed. The car has all the fruit including Maxi drive rear diff, lift kits etc..anyway I bought this car to travel to work 200km around trip. 95% of the time it will be on road. However I found that at 100kph the rpms are 3450. I am r running 235/85/16 tyres. I dont want to play around with diff centres or transfers $$$.
1: Can I fit bigger rims and tyres ie: range rover 18", eg 255/85/18 to give me a bigger circumference and extra top end speed at lower rpms. I downloaded an app on my android, tyre calculator.
2: Has anybody done this change, do they rub, any recommendations.
3: Could this cause issues with my tranfers/ drive.
4: I believe I have 300tdi/R380/LT230/3.54:1, I can work this out but as previously stated I dont want to spend $ modifying diff centres or transfers.
Thanks in Advance for your replies

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[isuzutoo-eh]

Rims that fit your Defender are those from the Series 3 Land Rover through to the current model Land ROver, and all Range Rovers up to but not including the P38, and Discovery 1 rims.
The weight rating is important though, you must use an appropriately rated rim, this leaves out most alloy rims and some steel rims.
You will be hard pressed finding an 18" rim to suit a Defender.
The 255/85/18 tyre size you are talking about has a 35" diameter. That's quite big. You may find a 300tdi is a bit gutless on big rims if you have much stop-start traffic to contend with.
Many of us use 255/85/16 tyres comfortably-a 33" tyre, on a 6.5" or wider rim, such as the stock 130 rims or aftermarket steel rims from Dynamic (I have 7" wide Kings but don't recommend them)
35" tyres on 16" rims are typically wide enough that the tyres will rub on the wheel arches. Most who run 35" tyres also change diff ratios to around about 4.10:1.

I recommend aiming for a taller tyre on the rims you already have.

[alex.com]

Thankyou for your reply isuzutoo-eh Interesting facts in regards to the rims and their load rating. I will now look at going down the path of fitting an overdrive.

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[chopper]

Thankyou for your reply isuzutoo-eh Interesting facts in regards to the rims and their load rating. I will now look at going down the path of fitting an overdrive.

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What about a transfer ratio change ?

[isuzutoo-eh]

Alex, are you sure your maths is correct? That RPM seems awfully high for a turbo diesel, I reckon you've found an answer around 1000rpm higher than it should be, or you've calculated it using fourth gear instead of fifth gear.
I think, for a 300tdi Defender, fourth at 100km/h will need 3200ish rpm, whilst fifth at 100km/h will see 2500ish. That is for a stock vehicle.

[alex.com]

Hi Isuzutoo -eh
Yes unfortunately this is correct I drive 200kms round trip to work. Last night I used my speedo and the GPS and at 100kpm im at 4000rpms
I have used this link [URL]http://www.ashcroft-transmissions.co.uk/calc/ratio_calc.html
Today I will physically confirm that I have a 300tdi r380 lt230 (1.6) 4.7 diffs and 32" wheels which gives me the 100kph@4000rpms this is what the calculator suggests i have.
I wore ear plugs and sat on 80kph on the way home from work last night. I will only drive this car around until I get a Discovery transfer lt230(1.2) which will bring my rpms down to 2860@100kph. Thanks again for your time I will post my transmission detail asap

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[alex.com]

Hi Chopper
Yes I will have to change my transfer to the discovery lt230(1.2) does anybody have any tips on what to look for when buying second hand
I can source one but usually they are being wrecked and not running. Also I will have to work out what serial numbers/model numbers to look for on the casing. Thanks for time Chopper.

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[isuzutoo-eh]

Unless someone has changed your front and rear crownwheels and pinions, you will have 3.54:1 not 4.7:1 diff ratios. All Defenders that we're likely to come across have 3.54 diffs from factory, the 4.7:1 ratio diffs were standard for leaf sprung Series Landies.

Recalculate with 3.54:1 diff ratio and you might find your numbers a bit better.

EDIT: In a previous post you said you have 3.54:1 diffs. I suspect your LT230 has a 1.410:1 high range ratio too.

No matter what, you need to know what you actually have before you can start making changes. If it is that loud, something is definitely up.

[alex.com]

Hi isuzutoo-eh
Yes I aggree with you...Strange?
I found my speedo is out compared to gps. I will check my tacho after but the noise and vibration suggests it is correct. 100kph@4000rpm
I have only had this car approx a week and it is my firsy Land Rover
I was originally quoting the factory fitted transmission configuration that was documented. And so far I have only physically confirmed that you are right it has a 22D def D/TDI 1.41 ratio transfer. I cannot find the location of the gearbox id/serial # on a r380 ( i think ) Does anybody know the location? I will jack up the diffs soon to check the ratios. Also does anybody know if I should have a plug in here , just behind the sump (photo) looks like the Clutch/ bellhousing drain???


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[isuzutoo-eh]

It'll almost certainly be an R380 gearbox.
The hole in the bellhousing does not come with a plug, nor does it usually need one. A wading plug can be fitted when fording water (or expecting to).

Defenders are occasionally labelled Deafeners, it may be that your Defender is just noisy. Is the interior complete, or is there a lot of white sheet metal visible in the footwells and around the seatbox?
At 100km/h you should be able to hold a conversation with a front seat passenger using slightly raised voices.

[PAT303]

I've been running 235/85x16 tubeless tyres on 5.5 rims for 16 years,never had an issue and I've never had a tyre shop say anything to me about it. Pat

[TonyC]

Alex,
If your Defender is a 300Tdi it should have a R380 gear box.
The R350 has reverse to the right and back, below 5th. The LT77 and LT85 have reverse to the left and forward, next to 1st. The LT95 is a four speed and has the transfer as part of the gearbox casting.

A 300Tdi Defender had a 1.41 high range in the transfer when it left the factory.

All (almost) coil sprung Land Rovers have 3.45 diffs.

These numbers give 2510 rpm at 100km/h using the Ashcroft web site.

Tony

[alex.com]

Thanks for the reply TonyC you are right about the ratios. I have a 300tdi r380 (56A ) lt230 (22D ratio 1.41) and 3.54 ratio diffs. I think my vdo tacho is out! As stated 100kph @3500 rpm seems too high. I have been offered a lt230 (14D A) that is a auto from a RRC with a 1.003 ratio does anybody know if these are a straight swap if not what will I need? Thanks

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[TonyC]

Thanks for the reply TonyC you are right about the ratios. I have a 300tdi r380 (56A ) lt230 (22D ratio 1.41) and 3.54 ratio diffs. I think my vdo tacho is out! As stated 100kph @3500 rpm seems too high. I have been offered a lt230 (14D A) that is a auto from a RRC with a 1.003 ratio does anybody know if these are a straight swap if not what will I need? Thanks

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I don't know if they are straight bolt up, but I doubt a 300tdi will pull a 1.003 high range transfer.

Your tacho is reading the frequency of the AC in the alternator.
So it needs to be set to match the alternator and the crank/alternator pulley ratios.

Tony

Tony

[alex.com]

Thanks TonyC I will try to work out how set up my rpm as you suggest. I bought the transfer lt230 1.003 (14D#@$/A) anyway and will try it out. I drive on the freeway to work.
I wont fit it just yet as I will overhaul it first and besides the wife and kid are jealous of the time I am spending on the new car already lol
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[slug_burner]

I don't expect anyone will recommend the 1.003 transfer behind the 300tdi. Some have found the 1.2 a bit tall if you are going to tow or carry any weight which is what the 130 is suited to.

You will be able to sell that 1.003 to someone doing a 4bdt conversion, I would not refurbish it as you will not get your money back.

[alex.com]

Thanks slag_burner I am sure you are right but I have a friend who tells me he put a 1.2 ratio on his defender it made little difference in fact he said putting bigger tyres on made more difference. I already have 235/85/16 tyres fitted. My engine is a 1998 300tdi and pulls hard in 5th at 100kph. I will try the 1.003 and fit a AP60 Cruise control ($260 from ebay I recommend) as I do 40,000 kms a year to work and back. I am sure your right but at least ill have plenty of practice in fitting transfers.


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[slug_burner]

the raio of 31 to 33 inch tyres is 1.0645 the ratio between a 1.2 and 1.4 transfer case is 1.166. I'll leave it up to the numbers to tell which would have the greater effect, you are going for a 1.4 ratio change when going for that 1.003 transfer case.

It will be good to get the practice if your keen to learn, but I would maximise my learning from others experience instead of learning lessons that have already been learnt before.

[alex.com]

Ahh i may have found my issue i have a maxi drive diff locker rear are they 3.54 ratio or 4.11 i will have to work it out.

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[slug_burner]

The maxi drive diff lock has no bearing on the ratio, it is just a sleeve that slips over a set of splines on the long side axle/drive shaft and locks the shaft to the diff and nullifies the differential action of the diff center.

Better of counting how many times the prop shaft turns for a turn of the wheels or open the diff and count the teeth on the crown wheel.