Strut Brace attachement

[Testament]

I have seen alot of different styles of strut brace attachment on various vehicles, some aspects appear to be more for ease of installation e.g two piece with a threaded adjustable section in between, But there are a number of other designs I am looking at and trying to decide which will be best for my 131.

the main styles I see are

- strut bar welded directly to top plates which bolt to the strut top mounting bolts


I can see this would be a "stiffer" installation (no pivot points) but its harder to install or remove (have to partly dissasemble suspension to get engine out)

- strut bar bolted at each strut top on front to rear axis of car


in theory may allow some movement as the bolt could be a pivot point (could use spherical bearing), although in practice may or may not be negligible? allows simple removal of brace for engine access

- strut bar bolted to top plates with bolt/stud in vertical axis

similar to above but pivot on different axis (would have almost identical effect if spherical bearing used?) again, easy removal.


Other additional braces or features

- Strut bar also bolted to firewall/scuttle panel

- additional diagonal braces ala 131 abarth



I don't think it would actually make any measurable difference to my level of racing (trackdays and club hillclimbs) but I'm still interested in what (if any) benefits of the various designs are.

[Testament]

No comments?

[Guy Croft]

I know how you feel!


G

[idv]

The best strut brace is one with both ends welded, with or without an adjustable section in the cross bar, like your top picture.
The next best is with one end fully welded and one end with a pivot, again with or without an adjustable section in the cross bar, a hybrid between the top and second picture.
Strut braces with two pivoting links offer too many degrees of motion and only help by keeping the strut towers the same distance apart as they tilt. This can be improved with additional braces to the bulkheads if the bulkheads are strong enough.
Braces to the front of the cars are usually to strengthen the front, not the strut towers.

Of course a fully welded brace with bulkhead supports would be better (difficult on a 131 with top mount distributor) and a fully integrated roll cage extended to the strut towers better still.

For a standard 131 one of the two braces I have suggested would make a noticeable difference on trackdays, more with better quality tyres.
And if you are removing a motor, the time it takes to remove six nuts, remove the strut brace and replace the nuts would be the quickest part of the job.
A good quality brace is a worthwhile investment.

[Guy Croft]

a considered reply, well done.

I've never braced a car in my life but I know plenty about structures.

It's important to understand the fundamentals when it comes to bracing. For a given applied load a structure will always deform at the weakest point. Is the vehicle being braced to reduce flex (in any particular direction) under normal driving loads (which can be extremely severe of course in a competition car) or to provide rigidity to protect the driver and occupants in the event of a crash? Or both? And then have a think how the concept of deformable 'crumple' zones was introduced into vehicle design. These absorb impact energy. In the light of what I have said, how does a vehicle with braces (such as the nice examples arrayed here) behave? And where are the weak points?

GC