AWD Chrome moly crossmember w/ roll stop ?

[NateCrisman]

The three crossmember bars and the front roll stop were exactly 20.5lb on my scale. So if this replacement bar is 5.5lb, we are talking about 15lb of weight savings. And at the very least, you need to use the rear chunks of the factory n/s bars to box in the subframe, which will add a pound or two.

Is this worth doing on a 3200lb street GVR4..hell no for both cost/gain and stucture reasons.

Is this worth doing for a flat out racecar (dragstrip) that is already down to 2300lb, already has CF body parts, 9lb wheels, and all the typical weight loss? HELL YES.

15lb is .015 of ET and a smidge less stress on your drivetrain. Granted this should be on the lower end of the list of "To-Do" when it comes to weight and power production, but to just say "forget it" on 15lb is foolish. This is the way you drop race weight...little bit at a time and generally every little bit is a sacrifice in money, effort, safetly, convienence, durability, or other negative factor.

This is something you do when there is no more "turn up the boost" available, there is no lighter car to buy, and ultimate performance is theonly goal. When you want to go 9.99 on a 16G turbo, then this is the kind of stuff one needs to look into. It's a RACECAR modification in my opinion.

 

[grocery_getter]

You don't find a merit in tieing the front chromoly roll mount bar to the subframe? Aside from those parallel bars nothing else are available there to keep a square structures. I know that there are the left and right frame rails going forward from the firewall area but the mounting point for the front roll mount bar is far too low and only by two studs on its far edge. You are going to end up bending the studs or doing some other damage from the motor torquing on it.

 

[NateCrisman]

The the engine produces enough torque to bend the TWO 14mm diameter studs that secure this bar to the frame, don't you think we would constantly see the SINGLE 10mm bolt bending that goes between the front roll stop and the engine mount bracket. The weakest link in the whole factory system is the cross bolt, and I'v never ever ever seen that bent. If there isnt enough force to bend one 10mm dia bolt, then there isn't enough force to bend two larger bolts since there is no leverage.

 

[Barnes]

Oh boy! This sounds like an excuse to perform a calculation! /ubbthreads/images/graemlins/grin.gif

P.S. Yes Andre, you did buy that subframe from me. Glad it found a nice home. /ubbthreads/images/graemlins/smile.gif

 

[JNR]

C'mon Barnes, let's see some of that SW magic /ubbthreads/images/graemlins/laugh.gif

Removing geometry from structural members on a street-driven chassis, yikes /ubbthreads/images/graemlins/crazy.gif Certainly room for improvement in the materials for performance gains, but a lot of professional thought needs go into it - I like seeing this stuff when it's done right though, so *can* be a good thing to look into...

 

[curtis]

This is could be compared to moving a building. When a company moves a house they slide a crap load of steel beams under it left to right them slide all that on 2 large ones and start down the road. Now lets pretend the house is 60 feet long and you put 10 cross beams at the back and one in the front. The distance of the span will flex up and down and rock over everybump. This is why house movers remove any brick facing and remove windows. Same with this car. If 30% of the span has no support its going to flex. Might be ok for a few times but eventually will crack something or start to deform the firewall or something on the rails.

 

[Galantvr41062]

I have made a few of these in the past, and I always use the 2 front to back bars to tie in the sub frame. I have cut the stock front to back pieces and welded a chrome moly tube to them and added flat flanges to attach them to the front cross member piece. I normally use the stock back half to retain the bolt pattern and use my own flange up front. In my race car build I still have the front to back bars on both sides and this is with a tubular front end.

~John