Thread: So how do I increase my tyre size without reducing articulation?

There seem to be two questions there. 1) do I need a lift to run bigger tyres and 2) will a lift detract from articulation.

You don't say what sized tyres you're currently running - we would presuming the stock 235/70 ?

I am no suspension expert but assuming you match the raised srings with the apropriate length/travel shocks, I would not expect you to lose too much if any articulation if going for say a 40mm (2") spring lift.......especially if you are adding larger tyres at the same time. I think it's only when you start going higher or lower in springs and shocks that you will then have to look at bump stops etc.

Think I am right with my assumptions Mick

Originally Posted by black betty

I had a nice little drive over the school holidays and came across a troopy needing a bit of a snatch out of a muddy hole.

What I noticed was that the lack of wheel articulation (leaf springs all round) was a factor in the troopy getting stuck. My standard Disco with road tyres crossed the muddy hole with no problems.

Well I was thinking about getting a 2”spring lift, which seems a standard modification these days, but now I’m not so sure as it will reduce my articulation.

So how do I increase my tyre size without reducing articulation?

there is absoluely no reason a 2 inch spring lift should REDUCE articulation... if done correctly it should INCREASE articulation

important factors:

spring lenght
spring rate
shock travel
shock lenght open
shock lenght closed
mounting height and position of shocks
extend brake lines

other little things that should be looked at:

retain springs, upgrade rear trailing arms, haultech slotted radius arm bushes.

bumpstop clearence... this can be changed to adjust where your up and down travel is...

food for thought

Serg

....body lift....

Assuming that you are not running on the pump stops, most spring lifts will reduce articulation.

Most spring lifts use a heavier spring.

It is simple maths. If a corner on your car weighs 1,000 lb. If you have 150 lb springs, you will get a total movement of around 13.33 inches. That is, zero compression when there is no weight on it, as all the weight is on the other wheel. 6.67 inches compressed when sitting flat (1,000 lb divided by 150 lb per inch). 13.33 inch compression when there is no weight on the opposite wheel and there is 2,000 lb of weight sitting on the spring.

Now increase the spring rate to 250 lb inch. Your total movement has just reduced to 8 inches (same calculations as previous with different rated springs).

The only time that stiffer springs may improve your articulation is where your upward movement is currently limited by the bump stops or springs binding on a regular basis. But this is not really lifting the vehicle as you are attempting to return it to normal ride after increasing the load in the vehicle or your springs are stuffed and you are replacing them with new ones.

OK, so now I'm really confused.

I thought that if you have longer shocks you get less compression - because the body of the shock is longer so it hits it's internal stops sooner.

Leaving legalities like insurance & engineering certificated aside..

A 2" spring lift is a very cost effective mod. Cheap to do, very useful increase in approach, ramp over & departure, & no changed necessary to steering. Usually.

Note that 2" is often 1 to 1.5" after 12 mths with spring sag!

With the same shocks you will have exactly the same articulation. Its moving through exactly the same cycle, with one exception.

The exception is extra winds in the (taller) spring, depending what you get. The spring may bottom out a bit earlier. Not good.

There are packages around like ARB/OME that have matched springs & shocks for a 2" lift.

Tyres - if you stay sensible in the bigger tyre size, say no more than 32", not much more is necessary. Wide tyres will need more trimming than skinny. 235/85/16 worked well on my old Disco. And you gearing/speedo is out correspondingly. All fixable. Wide tyres need offset rims to stop rubbing & steering lock issues. That in turn leads to flared guards.

Its when you go for more articulation that you need to worry about bump stops, brake lines, shock lengths etc etc.

Its not necessary to go crazy to get big improvements in grip & clearance.

Regards
Max P

Originally Posted by r.over

Assuming that you are not running on the pump stops, most spring lifts will reduce articulation.

Most spring lifts use a heavier spring.

It is simple maths. If a corner on your car weighs 1,000 lb. If you have 150 lb springs, you will get a total movement of around 13.33 inches. That is, zero compression when there is no weight on it, as all the weight is on the other wheel. 6.67 inches compressed when sitting flat (1,000 lb divided by 150 lb per inch). 13.33 inch compression when there is no weight on the opposite wheel and there is 2,000 lb of weight sitting on the spring.

Now increase the spring rate to 250 lb inch. Your total movement has just reduced to 8 inches (same calculations as previous with different rated springs).

The only time that stiffer springs may improve your articulation is where your upward movement is currently limited by the bump stops or springs binding on a regular basis. But this is not really lifting the vehicle as you are attempting to return it to normal ride after increasing the load in the vehicle or your springs are stuffed and you are replacing them with new ones.

There was no mention about stiffer springs the only thing mentioned was lift.

You can get softer springs than you currently have and still get a 2" lift but the main thing is to get shocks to match the length of the springs.

The shocks will then be your only limiting factor.

The other thing to keep in mind is swaybars.

When I did my lift, I ramped it before and after and it ramped exactly the same due to thats where the rear swaybar overcame the spring rate.

Unless your going to go a lift over 2" you wont have to worry about adjustable radius rods or excentric bushings blah blah blah.

You will be able to run 32" (maybe 33" depending on offset) tyres with a 2" lift and a camel cut (trimming the rear guards) without any effect on articulation unless you go for rock hard springs but this is something you can pick and choose when you buy your springs.

Body lift will lift the body so you get more clearence between tyre and top of inner guard but again, unless your going to run 37" tyres......theres no point.