Polybushes and strut braces

LiamC

I've ruined my car 🙁
Hello people of knowledge. I'm looking to get your opinions on here about suspension stiffening, in terms of removing flex. Basically I bought a fairly modified micra (suspension wise) to break for parts since it's been crashed about a thousand times and no longer has any sills. I've stripped all the fun bits off it now, but I have a question about refitting some of it to my own car.

The car I bought had fully polybushed wishbones, which I have already fitted on my own car, but it also had a whiteline front lower strut brace. Seeing that strut braces are fitted to reduce flex in the bushes, but polybushes are stiff as hell, I was wondering if there is much justification on fitting it. Basically, the polybushes have made a massive difference already, but I'm not sure if the lower brace will do anything much other than look nice if someone is unfortunate enough to have their head under my car for whatever reason.

I have done a large amount of Googling on this subject, but with answers ranging from "every single bush needs to be completely solid and braced so there's no movement at all" to "all strut braces are pointless and only add weight" I thought I'd get other people's thoughts on it.

Thanks for reading micra fans

"It just looks like a scrotum" - Jeremy Clarkson on the K12
 
Seeing that strut braces are fitted to reduce flex in the bushes, but polybushes are stiff as hell, I was wondering if there is much justification on fitting it
The front lower strut brace is supposed to reduce the movement of the mounting point, nothing to do with bush flex, although I can see where you're coming from with this, there could be a case for it actually being more important when you have stiffer bushes fitted.

A shame we never see any science shown about how much these brace bars reduce the movement at say the bottom ball-joint.
 

pollyp

Club Member
the lower arm poly bushes help sharpen steering response, maintain suspension geometry & alignment, and resist higher forces (especially with big powerful brakes on trackdays which used to destroy the standard front rubber bushings) by transferring forces between the arm & chassis mounts immediately with minimal deflection.

the front mounting structure for the lower arms is like a floppy open pelvis shape. all the lateral forces are transferred to the main chassis via this structure poking out and during intense trackday loads, these mounting points flex alot, affecting response & alignment geometry.

a lower brace really helps to join the pelvis structure to improve rigidity & reduce flexing.
I've even stiffened up the central beam and then anchor the lower brace onto that solid beam to further stiffen all that structure.

brace.jpg


the upper strut brace doesn't really do much tbh other than for aeshthetics cos the strut towers are already right up against the solid bulkhead.
 
OP
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LiamC

LiamC

I've ruined my car 🙁
the lower arm poly bushes help sharpen steering response, maintain suspension geometry & alignment, and resist higher forces (especially with big powerful brakes on trackdays which used to destroy the standard front rubber bushings) by transferring forces between the arm & chassis mounts immediately with minimal deflection.

the front mounting structure for the lower arms is like a floppy open pelvis shape. all the lateral forces are transferred to the main chassis via this structure poking out and during intense trackday loads, these mounting points flex alot, affecting response & alignment geometry.

a lower brace really helps to join the pelvis structure to improve rigidity & reduce flexing.
I've even stiffened up the central beam and then anchor the lower brace onto that solid beam to further stiffen all that structure.

View attachment 56891

the upper strut brace doesn't really do much tbh other than for aeshthetics cos the strut towers are already right up against the solid bulkhead.
Thank you 1275 and Paul, I'll get that fitted over the next week or 2 and let ye know how it goes. I didn't think the chassis and mounts would be flexing enough to warrant needing a brace, so I thought it must have been just bush related. They definitely do make a difference, most noticeable on a bend that has a slight hill. It's adjustable too, similar to how the top strut braces and also panhard rods are, which leaves room for a bit of change

"It just looks like a scrotum" - Jeremy Clarkson on the K12
 
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