2/3rd's of the original suspension travel explained!

**Oxer** · 06-11-2010 12:34 AM

Most of us have heard the famous words " Your car doesnt have 2/3rds's of the original suspension travel " at some stage, through a friends defect or through your own.

Here is a little information I posted on another forum that acually explains what the rule actually means and how cops get it so wrong on seemingly a constant basis.

Originally Posted by Oxer

the 2/3rd rule has nothing to do with the stiffness of the ride. The next time a cop pushes down on your car put in a complaint.

2/3rds means you take a factory strut, measure the length of the shock from one end to the other with NO weight on it at all. Divide that length by three, then whatever 2 thirds of the original length is is what your new suspension is allowed to be at a minimum...

Example: stock strut is 90mm > new coilovers etc are allowed to be a minimum 60mm in length with no weight on them. (no shit the example is stuped being in mm... )

There are a couple of rules as to the coilover construction (all locking rings have to be the same material as the shock body(eg. metal on metal, alloy on alloy etc.), Rose joints must have large washers so they dont simply pop through etc) but the 2/3rds has nothing to do with the stiffness of your ride quality. Dampners can be set to their hardest setting with 14kg springs and it can still be legal.

This was explained to me by a VASS engineer that specialises in suspension. Damn ****ing straight. He urged me to put forward complaints to any police that push down on the car to supposedly "test".

I elaborated a little more in that quote and thought it would be usefull to most people on here. There arent any restrictions on the stiffness of a cars suspension, For a cop to fine you for a car being too stiff is rediculous, and they dont know what the actuall rules/law are.

In saying that, there are exceptions to the coilovers as I said, aswell as ride height etc, but Im just making you aware that they have no right to push down on your car to "test" the 2/3rds rule as it has nothing to do with stiffness.

I recieved this information whilst talking to Bill Malkoutzis(VASS No.1011/ Talk Torque Automotive 48 Hillcrest Road Ph: (03) 9575 2347.) about engineering suspension work in the civic. We only had a brief chat, and as I said to him Im only looking into it for the time being as the car isnt running yet.

This is the real deal guys.

Pretty self explanitary, Though I wouldnt go telling cops you heard or read this info on an internet forum, as they will laugh in your face.

**Red_EG4** · 06-11-2010 06:42 AM

Do you know what the reasoning behind the locking rings needing to be of the same construction as the body?
Cheers for the information, handy to know. I might print it out and stick it in my glove box

**Oxer** · 06-11-2010 08:16 AM

Because of the different grades of material. A alloy lock ring can thread on a metal threaded strut, and a metal lockring will sheer on a alloy housing... It probably wouldnt, but technically from an engineering point of view, with enough force they will. The theory is that if its made from the same compound it will take a much much greater force to thred/sheer it.

Like I said, no point in printing this off to show police, because they will laugh in your face. Just question them, and put in the complaint. But you have to know your facts.

This information isnt about coilovers anyway, Its just to explain the 2/3rds rule. Technically, you need to engineer all the components to be 100% stress free.

**IEVAQ8** · 06-11-2010 10:19 AM

great work man....

**Red_EG4** · 07-11-2010 03:30 PM

Originally Posted by Oxer

Because of the different grades of material. A alloy lock ring can thread on a metal threaded strut, and a metal lockring will sheer on a alloy housing... It probably wouldnt, but technically from an engineering point of view, with enough force they will. The theory is that if its made from the same compound it will take a much much greater force to thred/sheer it.

Like I said, no point in printing this off to show police, because they will laugh in your face. Just question them, and put in the complaint. But you have to know your facts.

This information isnt about coilovers anyway, Its just to explain the 2/3rds rule. Technically, you need to engineer all the components to be 100% stress free.

KW suspension uses plastic spring lock, interesting.

How can a part in a suspension system be 100% stress free? not sure what you mean there.

**Oxer** · 07-11-2010 10:17 PM

Originally Posted by Red_EG4

KW suspension uses plastic spring lock, interesting.

How can a part in a suspension system be 100% stress free? not sure what you mean there.

Are you serious?

I suggest you re-read the last line, several times. If it doesn't make sence after that, book yourself into your nearest tafe's english course.

**anzai** · 08-11-2010 03:28 AM

just got done for this today. i didnt risk arguing because I knew if i did i wouldve gotten a fine or possibly points. ended up getting a major and roady without fine nor points

**Oxer** · 08-11-2010 04:51 AM

Pretty sure they cant give you points for driving an unroadworthy vehicle....

Unless the reason they pulled you over was for speeding/reckless driving.

They can fine you for anything....

The can fine you for your hairstyle if they really wanted to

**anzai** · 08-11-2010 04:56 AM

oh really? i think ive heard of people getting points while getting defected. not sure tho

anyway, whats annoying is the fact that it had to happen during exams period. fml

i might just sell up and buy a stock car haha. im so devoed i cant believe im still awake lolll

**Red_EG4** · 09-11-2010 09:51 PM

Originally Posted by Oxer

Are you serious?

I suggest you re-read the last line, several times. If it doesn't make sence after that, book yourself into your nearest tafe's english course.

Alright, I see what you're saying. In a topic where we were talking about engineering and material components my mind was relating stress to materials. Chill out brother.