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Upgrades needed for running large (35 inch) tyres

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Hi all

currently this is what i have on my 90 defender (it's bishbosh's old one) http://forums.lr4x4.com/index.php?showtopic=53877&st=0&p=491449entry491449

in short

• Disco 200TDi auto

• 1.22 Transfer box

• Disc braked rear axle with ARB locking differential (10 spline).

• Adjustable A frame ball joint.

• Extended stainless braided brake hoses all round

• Sumo track rod and drag link with Disco drop arm on the steering box so no more drop arm ball joint stress!

• HOFS HD cranked rear trailing arms.

• Gwyn Lewis shock mounts all round with +5" Rough Country shocks.

• Gwyn Lewis heavy duty rear spring retainers and relocation hook wotsits.

• Gwyn Lewis heavy duty front spring retainers.

• Front propshaft – wide angle from the Propshaft Clinic.

• Rear propshaft – wide angle from GKN (via Gwyn Lewis).

• Terra Firma +40mm springs all round.

and I am looking at these


so i have two questions really. all in all what will I need to upgrade in order to run these properly

and what will is the bare minimum i can get away with for the short term until i can save up some money???

i'm a little new to a lot of this so dont worry about teaching me to suck eggs. state the obvious!!!!



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Diffs / halfshafts and most likely CVs will all say Bye Bye

You need IMHO AS A MINIMUM 4 pin diffs, and after market (no, thats not britpart bearmach etc :lol: )

ARB 10 spline - diff fine, but 10 spline not, only some of the ARBs can be upgraded to 24 (what you need)

HD Type Shafts and CVs 24 spline and CVs 23 spline

In a word ££££££££££££££££s :)


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Gearing may need to be altered to suit the car. my Disco 300 Tdi manual / 1.22 transfer box needed 4.1 final drive ratio to help with the 33" tyres I put on.

As for putting 35" on. You'll probably need to alter the gearing in some way, either by changing the transfer box or by final drive gears, then it should be OK on the road.

10 spline shafts aren't the best of all shafts and do have a tendancy to 'ping' when put under stress, shafts would be my next point of call. You'll probably want either 24 spline OE shafts, or better yet some after market ones (KAM, Ashcroft, Terrafirma?? etc) will last a lot longer. however, along with the 24 spline shafts, you'll need some 24 spline diffs, and obviously something to replace the 10 splines ARB (may be able to get upgrade kit) Once that's done.

C.V joints will be the next on the list. You probably have the 32 spline CV's which are about as much use as the 10 splines. (23 spline CV's are more durable). CV upgrade's aren't cheap though. You can probably get away with the current CV's for a while, but I don't think they will last super long, so expect either a lot of second hand replacement CV's or some after market ones.

All in its not a cheap mod to run 35" tyres... but you can get by just by popping them on and driving around (slowly unless you sort gearing out) on the road, nothing should break straight away but be gentle. Go off road and it's anyone's guess as to weather things will last or not.

hope this helps


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OK, been there, done that so from bitter experience the bare minimum is..... NOTHING. Just run it and see what, if anything, breaks.

At some point you will break things though, I've since upgraded my rear shafts but the front is still good old 10 spline (I've got some ashcroft 24 spline and spare diff waiting on the shelf just in case though).

TBH I think the biggest issue you will have is the gearing which will be uncomfortably high. Hard to pull high gears and lack of control at low speeds. I run a 1.192 transfer box with my 35's but changed the diff gearing to 4.75s long before I worried about strengthening anything.

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x2. Change nothing for now, then see what is weak. I ran 35" simex for about 2 years on completely standars 90 drivetrain (apart from a rear locker for traction benifits) and have NEVER broken a drivetrain component.

Drive it sensibly and it'll be fine.

Might want to look at the 1.2 transfer box though - will be a bit high geared.

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What Trev said - try it, and learn MECHANICAL SYMPATHY, which is not only uncool but it's also not EXTREME or bling.

Chances are you'll end up going a different direction depending where the mood takes you (EG bigger again, or maybe an axle swap) so keep hold of the cheque book for now and see what happens.

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A friend of mine is running the same tyres & constantly broke things!! Diffs shafts etc. He is gently with it but does like to do extreme things!!

As above try & see what happens!!

Just a word of warning though!! when my friend measured his tyres and they measured at 36.5's although they say 35's on the tyre! He has ripped the pop rivets from the rear tub where tyre caught on the inside of wheel arch. If your running 1.222 trans box you'll probably end up changing to a lower ratio box.

Good luck with them if you go for it as they are a nice tyre ;)

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