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Droop!
doughie - 28/7/13 at 07:06 AM

In your experience, what amount of droop do i need to build into my book locost chassis 1. front and 2. back?


steve m - 28/7/13 at 08:35 AM

I was not aware of any droop in the book design, and mine does not have any


doughie - 28/7/13 at 08:57 AM

thanks steve m, i'm not sure if i'm describing this correctly?

when you jack your car up how much travel downwards do your front and rear wheels have?

when built and sitting on its wheels i want the rear trailing arms to be parallel with the floor and the front wishbones to be about the same... the suspension will need to move up (to accommodate bumps) and down (to accommodate holes in the road) - it's the down movement i am looking to build in... am guessing at about 1.5 inches if there is to be 4 inches of travel in total...??? is this right???


Slimy38 - 28/7/13 at 09:01 AM

Doughie, can I ask how you can 'build in' suspension travel? I thought it was dependent on things like final kerb weights, length of suspension dampers, spring ride height etc?


Theshed - 28/7/13 at 09:42 AM

Sounds like a perfectly sensible question to me! You will need an idea of bump/droop travel to find the right shocks. Trouble is I do not know the answer. Hopefully a 7 guru will be along shortly.

Adjustable spring collars will permit droop to be set to take account of weight changes etc.


JoelP - 28/7/13 at 09:46 AM

I think a couple of inches is the norm. If you have your shocks you can put the top bracket in the right place.


matt_gsxr - 28/7/13 at 11:35 AM

Rule of thumb seems to be 2:1 (compression to droop). I think I read it in a Staniforth book.


Theshed - 28/7/13 at 11:52 AM

My Peugeot 406 has about 25mm of droop. As it backs off the drive over the kerb one wheel will lift right off the ground.

Rally cars and offroad vehicles require bundles of droop. Circuit racers seem to have very little. I have split my suspension travel 40mm/10mm.

Presumably the requirement for droop depends upon whether, at high roll angles, grip from the inside wheel is going to be lost.


doughie - 28/7/13 at 12:07 PM

great answers guys - that's helped me get an idea - have the shocks already so with 1.5 inches droop at the rear and 1 at the front i can see where i need to position the shocker brackets


PhillipM - 28/7/13 at 05:59 PM

quote:
Originally posted by Theshed
My Peugeot 406 has about 25mm of droop. As it backs off the drive over the kerb one wheel will lift right off the ground.

Rally cars and offroad vehicles require bundles of droop. Circuit racers seem to have very little. I have split my suspension travel 40mm/10mm.

Presumably the requirement for droop depends upon whether, at high roll angles, grip from the inside wheel is going to be lost.


It's more for how rough the surface is, it usually doesn't matter if the wheel has been picked up on the inside in a corner as there's no weight there anyway, but for rough roads a lot of droop stops the chassis dropping into holes if the droop is limited.