Thanks for the suggestions guys.

I think my plan at the moment is to try and beg or borrow a set of 7.50 / 235/85 wheels and tyres and try them out. I don't do very many miles and have other cars for long motorway trips. If they feel OK then I'll probably leave it and accept the higher engine speed / wear. So long as it will sit at 60/65 happily then I'll be OK.

The only slightly daft problem is that I only have about half an inch of clearance between the roof and the garage door. So I may have to keep the old tyres and find another set of rims so I can get it inside!

I quite like the novelty of the overdrive, but I can probably flog that to pay for the upgraded transfer gears, although that means more work than bigger tyres.

Again, thanks for the information. Much appreciated.

Ric
 
ricyoung said:
Thanks for the suggestions guys.

I think my plan at the moment is to try and beg or borrow a set of 7.50 / 235/85 wheels and tyres and try them out. I don't do very many miles and have other cars for long motorway trips. If they feel OK then I'll probably leave it and accept the higher engine speed / wear. So long as it will sit at 60/65 happily then I'll be OK.

The only slightly daft problem is that I only have about half an inch of clearance between the roof and the garage door. So I may have to keep the old tyres and find another set of rims so I can get it inside!

Ric
Click to expand...

Mine doesn't sit happily at 60 to 65, even with bigger wheels and an overdrive, just too low geared. The bigger wheels are about 5" higher in diameter than the standard wheels..
Casp'
 
ricyoung said:
Thanks for the suggestions guys.

I think my plan at the moment is to try and beg or borrow a set of 7.50 / 235/85 wheels and tyres and try them out. I don't do very many miles and have other cars for long motorway trips. If they feel OK then I'll probably leave it and accept the higher engine speed / wear. So long as it will sit at 60/65 happily then I'll be OK.

The only slightly daft problem is that I only have about half an inch of clearance between the roof and the garage door. So I may have to keep the old tyres and find another set of rims so I can get it inside!

I quite like the novelty of the overdrive, but I can probably flog that to pay for the upgraded transfer gears, although that means more work than bigger tyres.

Again, thanks for the information. Much appreciated.

Ric
Click to expand...

the tyres on thier own will only give roughly a 10% increase in gearing (maybe not quite that much)

the ashcroft conversion gives nearly as much ratio increase as 3.54 diffs but as already said without the benefit of splitting gears that the overdrive will give

one of the things i like about the overdrive and diffs is the reduced noise level on the motorway, diffs, tall tyres and an overdrive brings the revs down appreciably at 60-65mph on the motorway thus reducing cabin noise (you could still do with extra noise killer stuff), mine just purr along nicely at those speeds with the overdrive but without you can certainly tell the noise increase from the engine, my 109 is a full bare van body so it echoes and reflects noise, my 88" is a bare truck cab so that also reflects noise

a rag top would be quieter as long as the canvas is taut and not flapping

what you "could" try being as you already have an overdrive (fitted??) is to fit a diff in the rear axle only (really easy quick job) to see what your thoughts are on noise levels (just don't try to use 4x4 or low box on solid ground unless you have freewheel hubs fitted so that you can disengage drive to the front wheels) with the overdrive engaged at speed and without at the same speed (use a satnag to give your speed)

just another suggestion for you to think on/contemplate
 
I went down the 3.5 disco diff route and did like NiteMere...fitted in the rear to test the water,

There are probs fitting some 3.5 diffs...I used early mk 1 Disco 3.5s...no filler plugs on the diff housing so had to weld some into the diff pans...and the speedo will under read,

My way around that was to take the glass off the speedo and put a small dot of white paint on the dial to co-inside with each 10mph segment upto 70 checked with a gps,

I was glad really to away from the overdrive...even thought I bought it new nearly 40 yesrs ago....needed to much maintenance...(topping up the oil) and getting away from the whine,

The diffs give the same gearing as the o/d did...I could do with slightly higher though...running on 205s so maybe a taller size in the future,

!st is still not used much even with my DI version of a 200.

Nick.
 
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Thanks all, I really appreciate you sharing your experience.

At the moment I can live with it so I think I'll just take it in easy stages. The front diff seems like a big job. Which considering the amount of use the car gets and the many other cars & boats which need attention. I might leave until it bugs me a bit more.

Luckily the overdrive doesn't whine and with the wright offroad matting its not crazily noisy - at least for the short trips I do.

If anyone in the North East has a set of 7.50 or equivalent wheels I can borrow for an hour I'd be very grateful! :)

Cheers, Ric
 
Have not got any 7.50's but have a 200DI with Ashcroft transfer case fitted if you want a test drive to see what you think of it.
 
I'm not sure how much time I'll have before the new year. So I'll PM you once I know if I'll be free.

Thank for the offer :)
 
At the risk of this becoming another wheels and tyres thread. I just wanted to share my conclusions having played about with the ratio calculator on the Ashcroft site.

The way I see it there I have three options. Stick with the standard diffs and overdrive and fit the biggest tyres I can, Upgrade to a higher ratio transfer box (and fit big tyres) or swap the diffs to 3.54 keeping the overdrive and big tyres.

Swapping the diffs makes by far the biggest difference as has already been mentioned. However If I was to go for 255/85 tyres on my current setup it would be comparable to a defender on 205/85s but not as good as one on 235/85s.

You should be able to see the comparison chart below for interest.

I take the point about increased engine wear, but presumably engines fitted to defenders with 205/85 tyres are not prone to excessive wear...?

So, to cut a long story short - can anyone see a problem in fitting 255/85 tyres to a standard Series 3 on standard springs?

At the moment this is my preferred option as its simple and easy :)

Cheers, Ric

 
Would have thought 255 width would greatly affect your turning circle .What wheels have you got as the offset also is a factor
 
I'm on the basic white 8 spoke steel ones you get at Paddocks etc. I think I'm going to have to get more wheels though as I need to keep the 205s, otherwise I can't get in the garage. So if I need different ones then its not the end of the world. I have got the originals somewhere but I had trouble using tubes with tubeless tyres so swapped to the aftermarket ones.

Regarding turning circle, I'm sure it will be different but I think I can probably live with it provided I can get into a normal car park bay without too much swearing.
 
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honestly i really wouldn't bother with the 255 tyres with the 4.7 diffs as you'll be putting yourself further into halfshaft stresses/snapping range with a 200tdi up front

the taller tyre will be a greater lever to push round

i'd possibly use that size tyre under a 109 but it'd want to be fitted with a PAIR of salisbury or ENV axles for me to be happy and neither of those go under an 88" with any semblance of ease plus would require custom length (shortened) propshafts

the simplest and most fuel efficient combination in my opinion is definitely, 7.50 or 235/85 tyres (less rolling resistance with the narrower tyres) with 3.54 diffs and your overdrive plus there'll be no need to fit excessively wide rims and minimal risk of body rub on articulation

also with 255 tyres you may need to fit spacers to retain any semblance of a sensible turning circle, which in turn will give you a 99% chance of pushing the tyres out past the edge of the bodywork which will possibly require trimming and to stay within the law will definitely require wheel arches/eyebrows fitting

235s fit nicely on 6.5" and fill the arches just nicely (ANR1534 or wolf) rims (as do 7.50s) but stay under the bodywork tucked nicely out of the way, you can also fit those tyres on standard 5.5" rims as were fitted to the 90/defender

i have ANR1534 rims on my '65 109 and i consider them to be in keeping with the age of the vehicle, wolf rims don't look too out of place either

you can play with your ratio calculators all day but they don't take into account stresses, to date i've only snapped one halfshaft which was under my 109 whilst loaded up and towing 1-1.25ton at a steep junction in Wales

as i've said earlier the optimum (in my opinion) is a pair of 3.9 (yes 3.9, rarer than rocking horse poo) diffs, overdrive and 7.50 tyres, this will minimise stresses and give very good fuel economy with a (thrashing the knackers off it) top speed of 90mph or more, it'll keep your low range down as well for hauling heavy loads and take a lot of stress off the gearbox
 
Thanks for the reply, I'll knock that idea on the head then...

Just out of curiosity, is it possible to run without the front propshaft attached? It's very rare that I use low ratio and on the few occasions when I have I don't think I would have needed 4 wheel drive. If I'm going to try swapping the rear diff to try it out, I'm just thinking that I could remove the front propshaft and at least retain low range - albeit at the rear only.

I don't have freewheel hubs I'm afraid.

Thanks again for you advise. Ric
 
yes you can remove the front propshaft and still drive it

i never have though even on my 109 which has a 3.54 rear diff and a 4.7 front diff (and fwh) , the reason for not removing it is if a halfshaft snaps you can then engage 4x4 and drag yourself away on just the front axle and you still have a handbrake to stop it rolling away

i've used 4x4 on my 109 about 4 or 5 times when i've lost traction to get me moving again, this is quite safe to do on loose or slippery surfaces and then change back into 2x4 once moving before you get back onto hard packed ground
 
I left my 4.7 in when I put one in the rear for a month or so...glad I did...worked fine in the snow...but had to be careful as the back end wanted to over take the front.
 
Hi All.

Just a quick update to say that I managed to get a set of 7.50 wheels and tyres on last week. As discussed before it's made about 10% difference to the gearing, so now my speedo is just under-reading. (60 indicated = 62 on GPS).

So I think that's how I'm going to leave it. Its happy sitting behind the HGVs and first isn't completely useless. My only consideration now is whether to put wider tyres on. My wallet says stick with the 7.50s as they do the job and are paid for, however having had wide tyres on before they do look a bit lost under the arches... Unless anyone has any suggestions??

On a completely unrelated topic I did the bilge blower mod to the heater fan and I'm really pleased with the improvement. The 3" one will (only just) fit between the wing and the matrix so I have installed it in-line with the original fan. By the wonder of diodes I've wired the switch to run the original fan at max on position 1 and both on 2.



Cheers, Ric
 
you could "give" ;) me the 7.50s that you don't like and buy yourself a nice shiney set of 235s to wear out :D

i run 7.50s on both of mine as the price was right (plus my bitsa has the super aggressive General SAG crossplies on it :D )

i've worn out both 235s and 7.50s
 
That is a very generous offer :) I'll be honest and admit I paid bu&&er all for them so if I do replace them I'll give you a shout.

I think the next plan is to give the wheels a bit of a refurb and see how flush I'm feeling after that.

Does anyone know an easy way of measuring wheel width when they have tyres on? They are very rusty on the inner face so I can't see any marks or stamps.

Cheers, Ric
 
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