Is a 265/75R16 tyre too wide for my D90 without mods?

As Far As I know these are pretty standard here in South Africa and the BFG are known for good milage. (Thats tyre wear, not fuel consumption).

we only really got the tdi and td5 in 90 format so I am not too sure how the d90 will handle them. The big advantage of a taller tire is that it raises the whole wagon which gives you more clearance. It might slightly raise your overall gearing but I doubt this would be noticable.

In South africa a lot of off road driving involves soft sand in which case the wider and taller the tire the better. In the UK I think you tend to deal more with mud so I don't think the extra width will help you much?

regards stephen

Dave,

BDG AT = Excellent tyre & give good longevity.

On a 90 I think I am right in saying that 265/75R16s will fit without any problems, though you will need to turn out the lock stops on each swivel assembly to stop the wheels rubbing on the radius arms on full lock.

I was told that 265x75s are more suited to a 110 due to the increased self weight over a 90. Its all to do with ideal ground pressure at each wheel - the wider the tyre for the same weight reduces the ground bearing pressure and therefore the vehicles ability to grip due to its own self weight.

Further to the ground pressure issue I believe the ideal tyre for a 90 is a 235x85R16. Its more or less the same height as the 265x75 but is a tad narrower, thus restoring some of the ground bearing pressure.

On a practical note, I have 235x75xR16 BFG ATs and can confirm they are an excellent all rounder. Depending on your wheels you may need to adjust your lock stops. Its easy though, from memory about a 3/4 spanner sorts its out.

Another thing people may say is that wider tyres put more strain on the power steering pump. This is true but the 265 pattern is a standard option anyway on some Defenders so I dont consider it a problem.

Just my opinion. Others will perhaps disagree.

Jon

Thanks Stephen. It's the 200tdi that I have. Have I misdescribed my vehicle when I say D90? I presume that's short for a Defender 90.

Thanks a lot for your tyre advice.

Dave.

Hi Jon, thanks for your detailed reply. I presume turning out the lock stops will reduce my turning circle a bit, not really too important though I guess.

Interesting, I'll have to do some more investigation into ground bearing pressure on the wheels. I wonder if our local tyre shop will understand what I am talking about ... :-)

I was just planning on steel wheels, don't need anything fancy. What wheels do you run?

I have heard that occasionally on full articulation the bigger wheels can rub, have you raised your suspension at all? And when people talk about raising their suspension by, say, 2", is that an easy job for an amateur to perform?

Apologies to reply with more questions but the deeper I delve into this, the more questions I get, and because a complete new set of wheels and tyres is not cheap I want to get it right :-)

Many thanks for any more advice,

Dave.

Yes it does, perhaps obvious, but the bigger the tyre, the greater its reduced - ignoring different wheel offsets for different wheels!!!

I doubt it! Also, bear in mind, if your driving on sand wide tyres are good, mud and general UK stuff normally requires the tyres to "dig in" to some degree rather than "float on".

I have a 200Tdi, 90. Mine is currently sat on Disco 1 steel wheels. They are fine for both sizes of tyre but the offset is not as great as

3rd party steel modulars so the lock stops need tourning out that little but more. I trial with mine and dont find the turning circle that much of a problem. I also managed to get 4 wheels for £20 rather than paying £30 per wheel for new modulars!

In message , Dave Smith writes

265/75 is standard fit on later D90s - my 98 50th Anniversary has them.

You will need to reduce your lock and this will reduce your turning circle quite a bit. I certainly noticed a difference compared to my 84 D90 with 235/85 which personally I think is a better tyre for off road use.

Your speedo will also be outside legal limits with the taller tyre and you will need to sort that out. I don't think you have to change the actual instrument, but no doubt someone more expert than me will be able to tell you how it's done on a 90.

I wouldn't take too much notice of what you read on car sites. It doesn't often translate onto Land Rovers.

HTH

On or around Thu, 10 Nov 2005 08:25:10 +0000, Dave Smith enlightened us thusly:

probably, depends, unlikely...

unless you do a lot of very soft ground then it's too wide, really, for most off-roading. Anything much over about 235 is wide on a 90. On hardish terrain you'll not gain any grip, and might even lose grip, due to reduced ground pressure. Grip ain't all about width - I had 10.5 wide on my 110 and have 7.50s on the SIII 109, and the latter performs better off-road - the

110 was lacking in grip on firm steep stuff, although it had a bit more flotation on soft going, I suppose - on marginal ground it maybe wouldn't have sunk where a narrower tyre would - however the range of terrain where that'd be decisive is quite narrow, and the lack of grip on firm slippery stuff was quite marked.

SWB series go very nicely on 7.50s, which are about the same width as a 205, but taller. 235/85 are a good compromise for a SWB or a 90 - a bit wider than standard, nice tall profile for better diff clearance, but not so wide that you lose too much grip.

I agree with Austin. Not all that good with metric tyre sizes. I have

31x10.5x15 on my 110 that I use for towing my trials landy, that has 7.50x16's on.

Wide "floats" over softer ground, narrow bites down through for grip. Depends so much on what you are driving on.

Wish we could have a nice tyre that will work on ALL terrain.

I have found that now I have the 235x85R16s on my speedo is spot on when tested against the GPS. I also have the factory fit gear cog.

If you bother to change your speedo its an easy job to do, the gauge doesnt need to be changed but there is a little plastic cog that fits into the Transfer Box (at the end of the speedo cable) - They are colour coded so its easy to see which one you have. I think from memory they are blue and yellow... or is it green? Personally I'd just put the tyres on and forget about the speedo thing...But thats just my opinion.

Jon

On or around Thu, 10 Nov 2005 19:35:04 -0000, "Bartty" enlightened us thusly:

You'd want a cunning self-modifying tyre, which changed it's tread pattern to suit the surface and got wider or narrower according to the softness of the terrain. Ideally the compound of the rubber would vary as well, of course.

I daresay someone will make one one day.

didnt they try that with the new Disco!

In message , Austin Shackles writes

Bridgestone and Michelin but they only fit em on F1 cars - and they only do about 200 miles and they're shot.

...and Jon spake unto the tribes of Usenet, saying...

I found the same going from 205s to 235/85s on a 90. No changes to the speedo at all.

FWIW, and IA (definitely) NAL, but I don't think there is a legal requirement to have an accurate speedo. The law simply requires that you drive within the speed limit - how you arrange that is up to you. I don't think speedo accuracy (or even the presence of one) is an MoT test point either. (At least, a search on

for "speedometer" gives no matches.) All the stuff about accurate to -0/+10% is C&U regs, as I understand, and unlikely ever to be tested in the real world.

On or around Fri, 11 Nov 2005 19:07:49 -0000, "Richard Brookman" enlightened us thusly:

but of course, if you arrange for it to under-read, by, for example, fitting bigger wheels, then it's not too clever to claim "well, it only read 30 on my speedo, officer" when nabbed.

I was thinking about this in respect of the minibus. Got a long term plan to replace the 195R14s (which is as big as you can go on the standard rims, original tyres are 185R14) with 205R16s, thereby making it ride better, increasing the ground clearance and increasing the choice of tyres.

This will require, among other things, the acquisition of 7 Iveco van wheels, which are the right size, type and stud spacing but will need chamfers on the stud holes as they have a different type of nuts. It may require some minor mods to the front wheel arches.

a bit of calculation yields that the original 185R14s have a nominal diameter of 25.7", whereas 205R16 have a ND of 28.9", which will raise the gearing by about 11%. This will not be a bad thing as the current 5th gear is usable at any speed over about 30 mph, whereas the current 1st gear is flat out at about 15 mph.

However, it will result in the speedo reading, for example, about 53 mph at a real 60 mph, presuming it was accurate before. Obviously, I'll take steps to check it, but presuming it is that far out, I was reckoning on making a new set of figures on a bit of paper and pasting it onto the speedo dial.

Why not keep the ground clearance the same, fit 205/60R16's and the speedo will be correct.......

Alex

Thanks for all the excellent helpful advice guys. Another thought occurs, do my insurers need to know about a change in tyre size? I'm just with the coop at the mo and I guess that as soon as I start talking about modifications the premium will hike so I'd be best looking at a land rover specialist insurer anyway.

Regards,

Dave.

Dave Smith wrote:

On or around Fri, 11 Nov 2005 22:23:28 +0000, Alex enlightened us thusly:

defeats the object - I'm trying to get it to ride more smoothly on small, sharp bumps. Fitting 195 instead of 185 section tyres has improved it. But the series III on it's 750R16s rides more smoothly on the same bit of terrain. Admittedly, it's on parabollocks, but then so's the minibus. from my observation, low profile tyres add harshness to the ride. Smaller wheels likewise, since the bumps are larger by comparison with the tyres.

There's also the issue of tyre availability - 205R16 is a very common size, fitted to loads of things, from jap trucks to rangies to 90s to discos. The old standard van tyres, 185R14 and 195R14 are on the decline - transits went to 15" wheels some time ago and now to 16" wheels with 175/70 or 185/70R16 style tyres on, and other vans likewise. Bugger all point, IMHO - you don't need the sharp handling that lower profile tyres give in a van, ferfexache. But the effect is that "traditional" van size tyres are getting more difficult to find and/or less choice.

In message , Richard Brookman writes

AIUI your speedo must not read slow. Speaking entirely from memory, I think you are allowed a 10% error if your speedo is fast ie indicates a speed higher than your actual speed. Logical really.

It is an offence not to have a speedo which falls within the legal requirements of accuracy. The fact that it is not an MOT point doesn't mean it's not illegal.

If you increase the diameter/circumference of your tyres then your speedo is going to read slow by the same percentage.

If you go from, say 7.50 x16 to 235/85 then they are virtually the same diameter, but a 235/85 is quite a bit taller than 205s - which is why the OP is considering changing in the first place, and why there are the different drive arrangements as someone has already mentioned.

7.50s of course were standard fit on 110s and on military 90s.