Outer Limits 4x4 Board

Hey all, putting air shocks in the front of madcow and have been looking at these ones on eBay- good price and easy to get
iPhone URL:
Fox Shocks 18" Travel Nitrogen 2.0" Shocks (pair)

Browser URL:
Fox Shocks 18" Travel Nitrogen 2.0" Shocks (pair)

Question is - it says in the description that the max weight they can handle is 550lbs per shock at 500psi,
At a guess the cow weighs in at around 1600ish kg full of fuel on 38s,
They are only going on the front the rear is staying 3/4 elliptical for now but
Are they going to be big enough?? don't wanna order the wrong part and regret it later on..

Cheers

Ryan

Ok so my iPhone won't post the links like i was hoping, but if you search eBay for fox air shocks they are
The only 18" travel ones that will come up in the list

My thinking would be weight above axle but dont take my word for it.

Ryan wrote:Hey all, putting air shocks in the front of madcow and have been looking at these ones on eBay- good price and easy to get
iPhone URL:
Fox Shocks 18" Travel Nitrogen 2.0" Shocks (pair)

Browser URL:
Fox Shocks 18" Travel Nitrogen 2.0" Shocks (pair)

Question is - it says in the description that the max weight they can handle is 550lbs per shock at 500psi,
At a guess the cow weighs in at around 1600ish kg full of fuel on 38s,
They are only going on the front the rear is staying 3/4 elliptical for now but
Are they going to be big enough?? don't wanna order the wrong part and regret it later on..

Cheers

Ryan

Well i know bugger all about air shocks, but for a start you can estimate the weight of your tyres and axles and take them out of the equation as they are unsprung weight. At a guess you could take 150 to 200kg off each end with those alone so that brings it to 1200 to 1300kg for the truck.

then you need to look at the weight balance. What motor are you running? (i'm assuming it's up the front). So surely there's a bias towards the front for weight.

Could you trailer it to a weighbridge nearby? Even one at a quarry or tip? Weigh the corners, axle, and total mass?

Milo is right you need to figure out what your weight split is front to rear and then take off the weight of your axles and wheels. That way you can figure out what weight is on your front suspension and then simply halve that and you have your front corner weight for each shock. Another way you can weigh it is if you can get some sort of scale that is big enough and sit it where the spring/shock would normally sit between the body and axle and let the body rest down on the scale and see what the weight is.

toughnut wrote:Milo is right you need to figure out what your weight split is front to rear and then take off the weight of your axles and wheels. That way you can figure out what weight is on your front suspension and then simply halve that and you have your front corner weight for each shock. Another way you can weigh it is if you can get some sort of scale that is big enough and sit it where the spring/shock would normally sit between the body and axle and let the body rest down on the scale and see what the weight is.

Get back to work you slattern!!!!

IMO:

Air shocks should only be used in a maximised droop suspension set up. ie 2-4 inches up travel and the rest droop/down travel. Perfect for slow rock crawlers, not so good for racers.

Air shocks work really well as bump stops because of the progressive pressure increase working against the compression of the shaft.

You need not get caught up in the exact weights of your rig. What you need to consider is the way in which an air shock works. The weight of the rig on each corner is supported on Nitrogen pressure acting on a 1.25 inch shaft. so whether a 2.0 or 2.5 inch shock is used the ride height pressure will be the same(but weight specs are very different??). What changes is the pressure within the shock body when the shock has to compress. The bigger the shock body the more volume of nitrogen and the less exponetial increase in pressure occurs. Remember the oil volume will not compress..

What this means: if you have a light rig your shock will have a much lower pressure at ride height-and much much lower pressure at full compress. So the shock will work in a acceptabe progressive nature.
If you have high pressure to support your rig, the progressive nature becomes very stiff and prevents full compression(hence 2.5 inch body in heavy rigs).

Hope this helps
Dan

dck7aok wrote:IMO:

Air shocks should only be used in a maximised droop suspension set up. ie 2-4 inches up travel and the rest droop/down travel. Perfect for slow rock crawlers, not so good for racers.

Air shocks work really well as bump stops because of the progressive pressure increase working against the compression of the shaft.

You need not get caught up in the exact weights of your rig. What you need to consider is the way in which an air shock works. The weight of the rig on each corner is supported on Nitrogen pressure acting on a 1.25 inch shaft. so whether a 2.0 or 2.5 inch shock is used the ride height pressure will be the same(but weight specs are very different??). What changes is the pressure within the shock body when the shock has to compress. The bigger the shock body the more volume of nitrogen and the less exponetial increase in pressure occurs. Remember the oil volume will not compress..

What this means: if you have a light rig your shock will have a much lower pressure at ride height-and much much lower pressure at full compress. So the shock will work in a acceptabe progressive nature.
If you have high pressure to support your rig, the progressive nature becomes very stiff and prevents full compression(hence 2.5 inch body in heavy rigs).

Hope this helps
Dan

Thanks for clearing that up for me i understand now mate cheers
air shocks on the way from the states