Rear Brace or Strut bar

[kmckmc]

Rear brace:


Rear brace: Right side detail


Rear brace detail 1:


Rear brace detail 2:


Rear brace detail 3:

[Sy V]

Front brace: What it would look like.

I have grave concerns about your proposed front brace mounting position. The rear appears to be OK though.

[Elanlover]

The rear brace looks like a nice piece of work. Curious as to your concerns about the front one though Sy. Could you share?

[Dave M]

I agree with Sy on the front brace as that mounting point is only held with an M5 bolt IIRC. If a larger bolt can be used, it may be an good option/location. Though with the weight and forces acting on the front suspension I'd think the current small bolt could snap. Maybe use two larger bolts in each of the front shell mounting points (the one you currently use + the one just to the right in the picture)? I'll check my car tonight to see if these both go through the strut tower - that would be best.

[algirdas]

Dear Dave:

I must be missing something here. The rear does look like a nice piece of work and I can see the need for the rear bar. But the need for a front bar has me scratching my head. I can see the need for a strut bar on a car with a suspension that is firmly affixed to the frame/unibody. If the frame/unibody starts flexing, it will start throwing off the suspension geometry.

But on the M100, the front suspension is insulated from the frame through the raft bushings. Because of that, who really cares if the strut towers move a little? Since the rafts and prongeron are all part of a coordinated dance movement independent of the frame/longeron, will firming up the strut towers make much of a difference?

Alternatively, I doubt if the suspension will transmit enough force through the rafts and raft bushings to the longeron/strut tower in order to cause the strut towers to start flapping around like fish out of water.

So, would the goal of the front strut bar be to firm up the struts during suspension bounce and rebound?

I need one of you brainiacs to educate me on this.

Sincerely,

Algirdas

[Dave M]

Algridas, you have a very good point. Due to the nature of the front suspension, the question of a front bar is debatable. The only reason I would install a front bar would be to tie the strut tower tops together and remove any additional movement (whatever little there may be) out of the equation. The reasons I haven't pursued it more is 1) the difficulty of getting proper bracing in that space without cutting or scarring the fiberglass shell, 2) the fact that there are existing braces that tie the strut tops to the chassis (just not to one another), and 3) the fact the car has a tendancy to understeer. Therefore stiffening the front more would make this worse.

I would like to try a bar however to see what difference it *could* make, however. Hopefully Michael can give us some feedback on how v1 of the bar does and see if it is worth pursuing further. Getting to a track anytime soon, Michael?

[kmckmc]

Hi All,

After discussing with my rollbar guy, he also agreed that the idea of Front Brace should be dropped.

However, the REAR BRACE looks fine, right?

[RayD]

I apologise in advance if the strut is only for cosmetic purposes… as a functional item I doubt it will do a great deal. After the holes have been drilled it will do slightly less. If the tops of the suspension legs have a tendency to come closer together, a piece of flat, machined aluminium bar won’t stop them.

If anyone thought there was a need to make it more solid they’d do better to drill a hole in the other corner for a four bolt fixing, and identify the optimum shape of the strut. If someone who knew what they were doing came up with the answer, it would probably be made of two curved steel tubes, and in the extreme it would be anchored to the chassis in the centre.

Thank you to the person who took the original picture, I hope you don’t mind me using it.

Ray

[GeoffSmith]

Welcome fellow sceptic! I raised a similar point about Dave M's strut as I can't see it making too much difference to the rigidity of the chassis U section. Doug claimed torsional rigidity is improved because the rear wheel lifts quicker when jacking at the front jacking point; I am even less convinced about this claim and Algirdas has agreed? to take a before and after photograph/video to convince me!

Geoff

[RayD]

Thanks Geoff,

I hadn’t read the Dave M’s Strut thread until now. My post was only in answer to the question raised by kmckmc.

If the standard chassis is too solid to be improved by a strut, then the reason for the rear wheel lifting sooner when using the front jacking point would be down to the improved fixture between the body and the chassis after a strut bar has been fitted. In other words you could get the same result by just fitting a top flange and increasing the number of fixing bolts.

Ray

[algirdas]

Dear Geoff:

I have agreed to do what?

Sincerely,

Algirdas

[ailwyn]

I have agreed to do what?

Agree that the rear strut is pointless by the sound of it....

[GeoffSmith]

I have agreed to do what?

Not long after me saying this, you said:

I better find out if they make a "long" lens for my camera.

Algirdas (a crotchety old fart in his own right)

I took it that you had agreed to take before and after photographs to prove me wrong and allow the powers-that-be to ceremonially burn this heretic at the stake.

[algirdas]

Dear Geoff:

But are we talking about me on Viagra or M100 on strut bar?

It's Friday. And it has been a long week.

Sincerely,

Algirdas

[GeoffSmith]

If it's Viagra, then you're probably in for a long hard weekend.

[GeoffSmith]

PS Don't forget the pictures.

[Doug]

Thanks Geoff,

I hadn’t read the Dave M’s Strut thread until now. My post was only in answer to the question raised by kmckmc.

If the standard chassis is too solid to be improved by a strut, then the reason for the rear wheel lifting sooner when using the front jacking point would be down to the improved fixture between the body and the chassis after a strut bar has been fitted. In other words you could get the same result by just fitting a top flange and increasing the number of fixing bolts.

Ray

I agree this is the possible reason -- I just pointed out the observation which was definitley different after the bar.

I don't see how the bar would affect the main frame center piece, which would likely be the twisting culprit if any.

Perhaps you could consider the bar as a rear tow bar for when Monty is stuck spun around off the track

[GeoffSmith]

Perhaps you could consider the bar as a rear tow bar for when Monty is stuck spun around off the track