Big Tyres

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Potato

Potato

Member
Posts
46
Location
Derby
Hi all,
My deestone 7.50 are wearing down now so I'm after some bigger rubber. I'm already looking down the path of HD half shafts, lockers etc so the axles can handle it. What's the biggest tyre you can fit without to much bodywork cutting? I know some people run 9.00s but I'm thinking some 35/10.5/16 could work? Any advice is welcome as alot of existing info seems unclear
 
What vehicle?

What use, what mods and what sort engine. Your question is all a bit too open ended really.

Assuming you mean a Series 88. Then stock diffs and gearbox are weak and stock engines have low power. You also can't upgrade the front shafts and UJ's as far as I know.

9.00 x 16 gives very little choice these days unless you accept bar grips. But these are narrow tyres. Modern wider tyres are likely to foul the bodywork at some point unless you plan to address it.

End of the day pretty much anything is possible though.
 
Thanks for the reply and yes I have an 88. I'm looking into engine/gearbox's (maybe Perkins).I also have access to a machine shop where I plan to adapt defender shafts with CVs to fit the narrower axles (and heat treat them) so the axles should be upto it. Is it the width of the tyres that'll cause more trouble than the hight? I'm not worried about turning circle either
 
Which Perkins, they vary a lot. I run a 4203 which has loads of torque and is great for economy but too heavy and low revving for off-roading and not suited to bigger tyres, the transmission can't take it. If you put more torque in the protection off road is that the narrow tyres slip, if they grip its too much for the box.
 
rob1miles said:
Which Perkins, they vary a lot. I run a 4203 which has loads of torque and is great for economy but too heavy and low revving for off-roading and not suited to bigger tyres, the transmission can't take it. If you put more torque in the protection off road is that the narrow tyres slip, if they grip its too much for the box.
Click to expand...
TBH I was looking at the 4203 or 4236 but I haven't done a huge amount of research. I always assumed the torque was what you want, when I jumped from a 2.0L mitsubishi with no torque but 137HP to the 2.25 landrover engine it felt great off-road? What sort of engine should I be looking at, ideally I'd be after something period or is the 2.25 upto it anyway? Thanks
 
If its a 2.25 petrol I would leave it as it is, the diesels are a bit under powered. The 4203 really only has a comfortable rev range of 900 to 1800 which is not much use off road, its fine green laning but it runs out of revs quickly. Its geared for 2000 rpm at 60 which is why its economical. The 4203 weighs at least 50% more than the LR engine and the 4236 will be even more. The 4203 is only 63 bhp, the 4236 is much more powerful as it can have a turbo (the 4203 can't) but the torque is way up and would need very carefull driving. Looked it up, the 4203 is 236KG!
 
7.50 16 looks best on a series and no loss of steering lock
Any bigger I thinks has more disadvantages and is a waste of time
My 88 is 2.25 diesel and I turned the pump up and now it's got plenty of power
 
rob1miles said:
If its a 2.25 petrol I would leave it as it is, the diesels are a bit under powered. The 4203 really only has a comfortable rev range of 900 to 1800 which is not much use off road, its fine green laning but it runs out of revs quickly. Its geared for 2000 rpm at 60 which is why its economical. The 4203 weighs at least 50% more than the LR engine and the 4236 will be even more. The 4203 is only 63 bhp, the 4236 is much more powerful as it can have a turbo (the 4203 can't) but the torque is way up and would need very carefull driving. Looked it up, the 4203 is 236KG!
Click to expand...
Yeah it's the petrol so I see how it goes, I can always go for the 6 cylinder petrol instead...
 
Chopz said:
7.50 16 looks best on a series and no loss of steering lock
Any bigger I thinks has more disadvantages and is a waste of time
My 88 is 2.25 diesel and I turned the pump up and now it's got plenty of power
Click to expand...
I'm struggling in the deeper mud where the axles are bottoming out, without going portals bigger tyres seem like a good plan
 
rob1miles said:
I think 7.50 /16 or 235/85 / 16 take some beating, they are a good compromise as the fit without mods and are still quite large. An 88 on really big tyres can end up looking like a toy.
Click to expand...
I don't disagree that 7.50s are good tbf. They just don't seem to give enough clearance under the axles especially when at pay and plays where there are some crazy ruts
 
Potato said:
Thanks for the reply and yes I have an 88. I'm looking into engine/gearbox's (maybe Perkins).I also have access to a machine shop where I plan to adapt defender shafts with CVs to fit the narrower axles (and heat treat them) so the axles should be upto it. Is it the width of the tyres that'll cause more trouble than the hight? I'm not worried about turning circle either
Click to expand...
I don’t know much about the Perkins swaps. Are you in the UK?

A Tdi swap is pretty easy or a V8. They are the ways I’d go. The petrol 2.5 from an early 90 might be an option and with a few mods perform well.

Interesting project about the front CV conversion. Would be interested to see how you get on.

Ashcroft Transmissions offer HD rear shafts. But if you are planning to be brutal the stock 4.7:1 diffs are unlikely to survive long. 3.54:1 from a coil sprung vehicle are stronger. But will mess with the gearing off road. Even more so in big tyres. So the only real option will be a HD crown wheel pinion from someone like Ashcroft. Which is quite a bit of ££££.

Personally I would be concerned with steering lock. A nimble vehicle off road is a great attribute and something with the turning circle of a cruise liner will be at a distinct disadvantage. Unless you are in the USA mud bogging.

You say the ruts are too deep. Where are you using your vehicle?

As for the bigger tyres. If you have flex suspension a 7.50 should be able to touch the inside of the rear seat box under compression on an 88. Bigger tyres may pose a real problem here unless you plan to mod the boxes or limit up travel.

I have run 8.25 x 16 on an 88. This is the size between a 7.50 and a 9.00 and is about as tall as a 255/85R16. But a bit more narrow.

The issue is the wheel openings on a Series are smaller than a 90. If the wheel is close to sticking out of the arch. Then under flex and compression it will likely impact the body work. I had to slightly trim the corner of the rear tub buy the front doors to stop the 8.25’s rubbing here.

On a flex suspension setup I think it would have been very difficult to run a 9.00 sized tyre without further body mods.
 
300bhp/ton said:
I don’t know much about the Perkins swaps. Are you in the UK?

A Tdi swap is pretty easy or a V8. They are the ways I’d go. The petrol 2.5 from an early 90 might be an option and with a few mods perform well.

Interesting project about the front CV conversion. Would be interested to see how you get on.

Ashcroft Transmissions offer HD rear shafts. But if you are planning to be brutal the stock 4.7:1 diffs are unlikely to survive long. 3.54:1 from a coil sprung vehicle are stronger. But will mess with the gearing off road. Even more so in big tyres. So the only real option will be a HD crown wheel pinion from someone like Ashcroft. Which is quite a bit of ££££.

Personally I would be concerned with steering lock. A nimble vehicle off road is a great attribute and something with the turning circle of a cruise liner will be at a distinct disadvantage. Unless you are in the USA mud bogging.

You say the ruts are too deep. Where are you using your vehicle?

As for the bigger tyres. If you have flex suspension a 7.50 should be able to touch the inside of the rear seat box under compression on an 88. Bigger tyres may pose a real problem here unless you plan to mod the boxes or limit up travel.

I have run 8.25 x 16 on an 88. This is the size between a 7.50 and a 9.00 and is about as tall as a 255/85R16. But a bit more narrow.

The issue is the wheel openings on a Series are smaller than a 90. If the wheel is close to sticking out of the arch. Then under flex and compression it will likely impact the body work. I had to slightly trim the corner of the rear tub buy the front doors to stop the 8.25’s rubbing here.

On a flex suspension setup I think it would have been very difficult to run a 9.00 sized tyre without further body mods.
Click to expand...
Thanks for the detail, I kinda want to keep the engine period hence the Perkins. If the 2.25 can't handle it I might have to look into the 200/300tdi (without the turbo?). Also I assume pegging the diff would do.but I'll research how I can keep the ratios e.g Ashcroft 4.75 gears.
I use it alot at pay and plays so often run it through muddy rutted tracks/bomb holes and I fancy keeping up with the big boys lol.
With the bodywork I've heard I can use 90 outer wings on the front to keep it looking neat and I gathered that I'd need to raise the rear boxes.
The 8.25 your running sounds interesting but I can't find many in the UK so 255/85/16 might be worth a look. Thanks for the great response too and it sounds like 35s might be a bit ambitious
 
Don’t get me wrong. I’m sure 35’s can be made to work. Even more so as many 35’s end up quite a bit shorter when you put a tape measure on them.

Just be prepared to potentially solve some rubbing issues and drivetrain durability. Easy fix for the rear is to swap on a Salisbury from a 109. The diff centre is basically a Dana 60 and will allow you to run lockers or Detroit’s from the USA. This axle isn’t perfect, but it’s a good easy upgrade and still Land Rover.

I would seriously consider a V8 conversion too. Very common and done loads of times. So much so that Land Rover ended up building the Stage 1 and then the V8 90 & 110. It’s pretty easy to do too. All you’d need is a 3.5 on carbs. They are good for about double the HP of the 2.25 petrol and a lot more torque.
 
300bhp/ton said:
Don’t get me wrong. I’m sure 35’s can be made to work. Even more so as many 35’s end up quite a bit shorter when you put a tape measure on them.

Just be prepared to potentially solve some rubbing issues and drivetrain durability. Easy fix for the rear is to swap on a Salisbury from a 109. The diff centre is basically a Dana 60 and will allow you to run lockers or Detroit’s from the USA. This axle isn’t perfect, but it’s a good easy upgrade and still Land Rover.

I would seriously consider a V8 conversion too. Very common and done loads of times. So much so that Land Rover ended up building the Stage 1 and then the V8 90 & 110. It’s pretty easy to do too. All you’d need is a 3.5 on carbs. They are good for about double the HP of the 2.25 petrol and a lot more torque.
Click to expand...
Thanks for the great replys! I'll get measuring up see what I'll end up doing and get looking for a 109 rear
 
even 35.10.50s are starting to get harder and harder to find these days, but with that said what rims you want to use come a big part of how there going to fit.
For example I’m running 35.12.50s on mine and I’ve had to cut a fair chunk of body work out to stop any clearance issues and mine just touch the tub on full flex

And even then before I converted to disco axles
My old set of 35.13.50s would rub the leaf spring before you get anywhere near full lock and that was with a -32 offset 10” wide modular
 
henseyseries3 said:
even 35.10.50s are starting to get harder and harder to find these days, but with that said what rims you want to use come a big part of how there going to fit.
For example I’m running 35.12.50s on mine and I’ve had to cut a fair chunk of body work out to stop any clearance issues and mine just touch the tub on full flex

And even then before I converted to disco axles
My old set of 35.13.50s would rub the leaf spring before you get anywhere near full lock and that was with a -32 offset 10” wide modular
Click to expand...
Thanks for the reply,
The reason I was looking at the 10.50s is they will fit on a far narrower rim (8j or some people even fit them on 7j) that would let me space them out far further than on a 10j rim but it sounds like that still might not give me enough clearance. I'm going to the local tyre shop soon to measure the real world sizes of some 35/10.5/16 and 255/85/16s as I think they might be a better fit and generally cause less issues as I don't fancy going to defender axles yet... I'm also guessing that your wheel arches are off a defender, it looks amazing lol.
 
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