Carbon Strut Bars

I am starting a new project which will be a GC8 Impreza . I am looking for strut bars and have come across the oem carbon strut bar which is held together with epoxy .

I am quite curious in regards to how it will hold ? Does anyone have any real world experience with these ?

What exactly is your concern?

Properly constructed carbon fibre parts are much stronger and stiffer than steel, for the same weight, which means they can be made lighter without sacrificing strength.That' s why the material is used where weight and strength are critical, such as motorsport, sailing, aircraft, etc.

There is also quite a wide range of "epoxy" with very different properties - they're commonly used in modern vehicle construction and are a crucial part of modern aircraft construction - they're largely glued together.

I totally agree with you on the matter of strength but my concern is when the car is under load in a corner will the brace work as its supposed to ?

I can't actually describe properly in writings what my concern is but I will give it a go . So let's say under a corner the inside shocks/tyres etc. will have more work to do than the outer . Will the the epoxy be enough to keep it intact? Won't the other side try to pull away or be free ? Not sure if you get what I am trying to say.

Also any good epoxy for such a thing ?

Hi Dimitrios. I understand what you are asking. The first thing to cover here is that as long as a carbon part is well made, you don't need to worry about the resin (normally an epoxy) as carbon fibre parts are designed to work together properly with the resin. As Gord pointed out, in most cases (for similar dimensions) a carbon part (including the epoxy!) is far superior in terms of both stiffness and strength relative to something like steel or aluminium.

As to the question of "Is an OEM carbon strut brace stiff enough?" To answer this properly we have to find a way to test the stiffness, which is more effort than most people are prepared to put it and makes this impractical In saying that, it's probably fine and doing an ok job, certainly better than nothing!

The bigger problem with the factory strut braces from the GC8 Impreza's is that they are not straight! They are designed to fit behind the original intercooler. Having a big arc in the main body of the brace makes it lose a lot of its stiffness. The limiting factor becomes the buckling of the bar in this case. If you no longer have the top-mounted intercooler, it's likely a better idea to use a totally straight strut brace bar for better stiffness overall.

Dimitrios, if it's OEM it will be fine. The loading are almost entirely being passed through the fibres and the bonding agent (epoxy) is used to bold the fibres together, in alignment, and to attach the end 'hard points'.

I would certainly be happy to use it, especially failing to find something stronger, as it will all aid the front stiffness by holding the truts in better alignment.

Tim, yup, a straight strut or tie is certainly the optimum design, for the reason you mentioned, but I expect Subaru were aware of that and tried their best, within the constraints placed upon them. I haven't experience of the Sub' brace, but have some minor experience with CFC parts and have a rather slim strut section from an America's Cup yacht that is incredible stiff compared to a steel part of the same dimensions, and expect much the same from the Sub' strut.

Compared to the standard GC8 bodyshell, the OEM Carbon Fiber braces add a lot of stiffnees to the front end of the car and work well. I have done testing of the bent braces and the straight unit, both on and off the vehicle and in most cases the carbon fiber units where stiffer in both tension and compression than the aftermarket aluminum braces.

Thank you to everyone taking the time to help me out . I have been reading a lot of mixed reviews in regards to it and I was kinda surprised as I had similar thoughts to everyone here . But never had I had a personal experience.

Thanks again .