Anaconda · Tuesday at 19:04

200tdi Ninety with Disco gearbox and transfer box.
Son has fitted some wolf wheels with 255/85 16 tyres and I have a feeling that they may be a bit big. I drove it for the first time today and while I knew the speedo would be out a bit, which it is.
Acceleration doesn't seem so good especially noticeable gaining speed from 40mph upwards.
Is it going to struggle a bit?
It did have 265/85 16 and in general was fine with those.

lynall · Tuesday at 19:15

I always smile when I see people saying disco tfer box best mod for defenders!

Anaconda · Tuesday at 19:24

And it works just fine with 265/75 16s.
That's how it was when he bought it, (I think) Disco 200tdi, gearbox and transfer box.
I'm wondering if he might have made a mistake with the wheels and tyres and made it slightly less driver friendly.

Hicap phill · Tuesday at 20:13

Ooo some cheap tyres may be appearing soon…

Are they smaller than a 7.50? (I Run this size)
I run a 1.22 transfer box & no hassle. Just can’t tow heavy trailers unless in low box to start.
Think the disco box is diffent geared & used to run 205s not sure what the biggest they used

Anaconda · Tuesday at 20:29

Hicap phill said:
Ooo some cheap tyres may be appearing soon…

Are they smaller than a 7.50? (I Run this size)
I run a 1.22 transfer box & no hassle. Just can’t tow heavy trailers unless in low box to start.
Think the disco box is diffent geared & used to run 205s not sure what the biggest they used

245s, mind you the 2a came with D1 steel wheels which were 205 I think. Maybe the alloys came with 245s?
They are nearly new BFG MTS, they wouldn't be cheap.
I can see I will end up with them on my TD5

Hicap phill · Tuesday at 20:43

Anaconda said:
245s, mind you the 2a came with D1 steel wheels which were 205 I think. Maybe the alloys came with 245s?
They are nearly new BFG MTS, they wouldn't be cheap.
I can see I will end up with them on my TD5

Change the transfer box to a 1.4. These are common and would help the pull away.
You may loose 1st or not use it much
Simple remove,replace to see if it helps

Anaconda · Tuesday at 20:47

That would be cheaper than changing the tyres for sure.
I might keep an eye out for one.
My son hasn't driven it yet, might think it's OK.

300bhp/ton · Wednesday at 09:50

Anaconda said:
200tdi Ninety with Disco gearbox and transfer box.
Son has fitted some wolf wheels with 255/85 16 tyres and I have a feeling that they may be a bit big. I drove it for the first time today and while I knew the speedo would be out a bit, which it is.
Acceleration doesn't seem so good especially noticeable gaining speed from 40mph upwards.
Is it going to struggle a bit?
It did have 265/85 16 and in general was fine with those.

Do you know which gear ratios? You say Disco box, so it is probably the latter taller gearset. In reality it is over geared. Which you'll notice in 1st gear pulling away and if towing.

But the Tdi is a stout engine and if tuned should pull it ok. How heavy is the 90, is it fully loaded up?

The Ashcroft transmission site has a gear calculator, you can look at the gearing options. However, a 1.4 transfer box would likely solve most issues.

But does depend on what you use it for and if high speed cruising is essential.

To show it can work, here is a vid of my 200Tdi (the pickup with the yellow roof). I'm also running a 1.2 transfer box and Disco LT-77. But the engine is modded.

I'm on 7.00 x 16's in this vid, but normally run 33.10.50R15's, which are quite similar to a 255/85

scott3933 · Wednesday at 09:57

To me it sounds like the transfer box is the issue... I know 90s came with a 1.4, and earlier ones came with 6.50 tyres, and later 205/75 (or something like that, im just guessing)... So putting massive tyres on even stock you're going to effectively shift everything up a bit higher with gearing. Then throw a 1.2 transfer box in and its the same yet again. So makes sense that it may be struggling.

Meanwhile my 110 is on the opposite end of the scale, still got its original 1.667 transfer box... pulls away nicely but she's a bit slow!

Anaconda · Wednesday at 12:52

300bhp/ton said:
Do you know which gear ratios? You say Disco box, so it is probably the latter taller gearset. In reality it is over geared. Which you'll notice in 1st gear pulling away and if towing.

But the Tdi is a stout engine and if tuned should pull it ok. How heavy is the 90, is it fully loaded up?

The Ashcroft transmission site has a gear calculator, you can look at the gearing options. However, a 1.4 transfer box would likely solve most issues.

But does depend on what you use it for and if high speed cruising is essential.

To show it can work, here is a vid of my 200Tdi (the pickup with the yellow roof). I'm also running a 1.2 transfer box and Disco LT-77. But the engine is modded.

I'm on 7.00 x 16's in this vid, but normally run 33.10.50R15's, which are quite similar to a 255/85

Doesn't carry any weight in it really, the engine is stock. It's used mostly for easy laning and the odd road trip to Wales now and again.
It might just be me comparing it to my TD5, will report back when he has driven it a bit.

dag019 · Wednesday at 15:14

On my 110 I found that running 35" diameter tyres was the same as fitting the 1.2 transfer box in terms of speed vs revs vs drivability (I am sure someone who can be bothers can work out the actual ratios and tell me different). Running both would certainly have made the thing struggle. I run 265/75 with the 1.2 now and that is a nice combination for high motorway miles and not a lot of towing. but as mentioned above is not good for setting off with a loaded trailer.
although overall diameters may vary manufacture to manufacturer the "true" diameter for the three combinations are below, but I would suggest that with manufacture variation there is a potential for them both to be the same size unless form the same brand:

size	Diameter
7.50	31
265/75	31.6
265/85	33.7
255/85	33

miktdish · Wednesday at 21:56

Wheels are good (ideal in my opinion) the transfer box is the wrong ratio for a Defender (again IMO).

Get a 1.4:1 ratio LT230, it bolts straight on and the car will spring back to life and look good too.
Small wheels kindof gets the ratio's right again, but looks pants.

Anaconda · 2025-08-28T08:23:28+0100

Update as promised.
My son took it out yesterday evening and drove a few roads which we have driven a thousand times. He knows what speed it would normally do and what gear it would be in. It's a mix of country, town and fast A roads with a couple of big long hills, no motorway though.
He was very pleased that it actually improved around town and had no negative effect on the faster roads. Another up side is the handling and ride comfort is far better and the wider track straddles the silly narrow speed bumps they put in. So the result is for general driving it has slightly improved, looks like I was worried about nothing, happy days.

300bhp/ton · 2025-08-28T13:22:57+0100

Anaconda said:
Update as promised.
My son took it out yesterday evening and drove a few roads which we have driven a thousand times. He knows what speed it would normally do and what gear it would be in. It's a mix of country, town and fast A roads with a couple of big long hills, no motorway though.
He was very pleased that it actually improved around town and had no negative effect on the faster roads. Another up side is the handling and ride comfort is far better and the wider track straddles the silly narrow speed bumps they put in. So the result is for general driving it has slightly improved, looks like I was worried about nothing, happy days.

Do remember the speedo will be out though. And it must have impacted acceleration, else physics have left the building. How do you mean improved around town? I imagine it won't pull 4th gear at 30mph now unless it is completely level ground.

Anaconda · 2025-08-28T13:33:22+0100

300bhp/ton said:
Do remember the speedo will be out though. And it must have impacted acceleration, else physics have left the building. How do you mean improved around town? I imagine it won't pull 4th gear at 30mph now unless it is completely level ground.

He knows that, he used his phone for a speed comparison.
It's 3rd gear for 30mph most of the time but not on full revs, you can accelerate out of 3rd into 4th when the speed limit changes.
30mph has always really been an in-between speed gear wise, ideally a 3 1/2 gear would be best.
I am sure if you had it in a lab on a rolling road then it most likely is slightly slower to accelerate but the most important thing is that it's not noticeably different or made it unusable.
It is after all an old Land Rover not a sports car.

dag019 · 2025-08-28T19:32:53+0100

Anaconda said:
30mph has always really been an in-between speed gear wise, ideally a 3 1/2 gear would be best.

With a 1.2 box and 265/75 tyres that ^^ I could not agree more with! You either need to sit a 25, or 35, neither of which is ideal!

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