ground clearance?

[bikesrfast]

I am interested to know if/what the 'industry' standard for ground clearance is (rule of the thumb) in comparison to suspension travel.

My vehicle i am building for weekend road use has 4" of shaft (mcpherson) with 2" bump rubbers, so I assume 3" of front suspension bump travel.

I currently have 4" of chassis clearance, does this sound good/bad?

 

[GregLocock]

In Australia the official ground clearance requirement is a 15 fl oz beer can's height (seriously). That's about 5"

Suspension stroke is up to you. On smooth roads, driven very carefully, 2" is just adequate. Stiffer springs mean you can run less stroke.







Cheers

Greg Locock

SIGlease see FAQ731-376 for tips on how to make the best use of Eng-Tips.

 

[cibachrome]

Two regions considered are wash rack tracks (static) and railroad crossing (dynamic).

Consumer Reports shows mostly 4, 5 and 7". A few are 2.5" (static measurements).

 

[GregLocock]

I'm talking from kerb to 2g dynamic, by the way, and when I said suspension stroke I should have said wheel stroke.

You'll also need some travel into rebound.

The more you have the more options you have when tuning the suspension.



Cheers

Greg Locock

SIGlease see FAQ731-376 for tips on how to make the best use of Eng-Tips.

 

[bikesrfast]

thanks for taking the time to answer me.

I think there's is some confusion as to what I require, although I was interested to know the industry standard (thanks Greg).

I have 3" of wheel travel in bump, I have 4" of ground clearance. Is this a reasonable combination for average and light sports driving? I am at rolling chassis stage and can adjust the ride height now if there was some thinking that I could go lower (preferable) or thinking that raising may be required.

My chassis would have about 600mm from front axle center to front protruding chassis low point running 640mm dia tyres (16/205/55).

I have a total travel of about 8.5" (4" up 4.5" down without 2" thick bump rubbers in place).

Thanks again!

 

[GregLocock]

If you don't have 5" ground clearance and you are stopped by the cops in Australia (generally for being an idiot) then you will get an unroadworthy ticket. Does that help?

So far as legal standards go generally, sorry that will depend on your jurisdiction.





Cheers

Greg Locock

SIGlease see FAQ731-376 for tips on how to make the best use of Eng-Tips.

 

[patprimmer]

You do not want the chassis or body to strike the ground at full bump.

Also it is very desirable that the chassis or body does not strike the ground when you get a flat tyre.

A lot depends on manner of use, how hard the springs are, type of terrain of use and local laws.

There are a lot of compromises in the mix, and you need to decide which trade offs you want to make.

New car designers and marketing spend a lot of times deciding on the trade offs for each model. A luxury model will be different to a family model which will be different to a off road or utility model which will be different to a soft core sports model to a hard core sports/racing model.

Regards

eng-tips, by professional engineers for professional engineers
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

 

[bikesrfast]

No it doesnt help because my car isnt a car so the 5" law doesnt apply

I havent built a roadcar from scratch before (a few racers up my sleeve)and have a 1" chassis clearance at full travel, level car. I was wondering if there was something about this figure that the more experienced roadcar boffins may know about.

Again, thanks for the interest.

 

[GregLocock]

Well it doesn't sound much, but it is about 1-2" less than a typical Australian sedan, so it doesn't sound like the end of the world.

Incidentally, a ground clearance line is a bit of a misnomer, the line is actually a series of planes underneath the car, to cope with kerbs, speedhumps etc. For instance, we can have less ground clearance out near the wheels, because the wheels protect that space.



Cheers

Greg Locock

SIGlease see FAQ731-376 for tips on how to make the best use of Eng-Tips.

 

[bikesrfast]

Thank you.

Yes I understand there are area's to be wary, obviously mid belly rearwards isnt a good place to be low for example.

Also I will try to have more clearance at the furthermost point of the chassis.

Of course we have all seen what happens to low cars with a big front spoiler hanging way out front when they negotiate sloping driveways etc.. Of course exhaust shops like the extra business

 

[bentwings1]

GregLocock, Your clearance rule has got to be one of the best yet. haha Were that the rule here, auto enthusiasts being what they are would invent an elaborate game involving many cases of beer to see whose streetrods were high enough. By the end of the day the height of rods would be long forgotten and individual's height would measured the same way. haha

And by the way my 41 Willys is just 4" in front. Just clears a small hyd jack so it looks like I'm in trouble already. I worry more about hitting road kill at night than anything. Especially skunks and 'possums.

99 Dodge CTD dually.