Tubular rear subframe - Input needed

[snowborder714]

I'm ready for one now. I'd love to take my current one off, send it to Robispec for the lateral arm mount mod, and then put solid bushings in it. But I figure why waste my time when hopefully someone will get a tubular unit built which takes all of this (and more) into account.

 

[99gst_racer]

Anybody know of someone who has a Robispec subframe that isn't installed yet? I'd love to get my hands on one for a week to take some measurements and whatnot.

 

[snowborder714]

Nope. Only people I know with one are Drew, Kevin, and John.

 

[greengoblin]

Shot me a pm and we can talk Paul. I'd be willing to help out.

Also Brian you you might want to really read the rule sets. You may find that the tube xmember puts you in classes that would be VERY difficult to compete in.

Kevin

 

[snowborder714]

Honestly at this point, I'm not looking to compete. I just don't have the time or money to do so, especially with traveling weekly for work. Right now I'm just in it for the fun and experience. Maybe if/once I stop traveling I might consider it, but who knows.

But I do know that almost every mod I do I check against the rule book. However just having a turbo upgrade and MBC has put me in a fairly high class, so oh well.

 

[talont3t4]

Any idea what the final version will weigh?

 

[99gst_racer]

I'd hate to speculate. I don't even know what this tubing weighs per foot. As soon as I get the first one done, I'll bring it to work and weight it on one of our UPS scales. I'll also weight a stock one to compare.

 

[talont3t4]

I'd hate to speculate. I don't even know what this tubing weighs per foot. As soon as I get the first one done, I'll bring it to work and weight it on one of our UPS scales. I'll also weight a stock one to compare.

I'm just about to start building my subframes so I can get you the stock weight. I no the front is 36lbs I'll have to check the rear.

 

[fjm9898]

So excited, cant wait to see this thing.

 

[jw4free]

The front subframe is 35.5 lbs - Bare.
The rear subframe is 44.4 lbs - Bare. Include cast iron and rubber nose support, bolts, bottom support - 50 lbs. The differential (viscous LSD weighs - 45.2 lbs. (for comparison). Each axle assembly is around 65 lbs. There is room for weight savings, but the weight of the subframe is 18% of the rear subassembly weight (280 lbs). If you were to cut the weight of the subframe (and control arms) in half - say 28lbs saving, that equivalent to running with 4.5 gallons less fuel in the tank. That is something worth noting. On it's own not that big of a deal, but with additional weight savings, it all adds up.

The other issue, I just took apart a '96 GSX with 60,XXX miles on the odometer. It was rusty, especially the lower control arms. Mainly surface rust, but all the bolts look like crap, and many are un-usable. Installing new hardware that's built strong is worth a lot.

 

[talont3t4]

The front subframe is 35.5 lbs - Bare.
The rear subframe is 44.4 lbs - Bare. Include cast iron and rubber nose support, bolts, bottom support - 50 lbs. The differential (viscous LSD weighs - 45.2 lbs. (for comparison). Each axle assembly is around 65 lbs. There is room for weight savings, but the weight of the subframe is 18% of the rear subassembly weight (280 lbs). If you were to cut the weight of the subframe (and control arms) in half - say 28lbs saving, that equivalent to running with 4.5 gallons less fuel in the tank. That is something worth noting. On it's own not that big of a deal, but will additional weight savings, it all adds up.

The other issue, I just took apart a '96 GSX with 60,XXX miles on the odometer. It was rusty, especially the lower control arms. Mainly surface rust, but all the bolts look like crap, and many are un-usable. Installing new hardware that's built strong is worth a lot.

Is the 280 with shocks and brakes?

 

[jw4free]

Is the 280 with shocks and brakes?

Yeah that's right.

 

[UGOT8UP]

I havent read the whole thread but using cromo for the control arms might not be a good idea for a street car, on my old Malibu the chassis shop built my car out of cromo and I had a problem with the control arms breaking while driving down the road, broke one upper and two lowers, reason was because the material is brittle and will break not bend like mild steel, once he figured out the problem and fabbed up some mild arms I never broke or even bent another arm, driving with a broken arm feels like driving with a flat tire, the car didn't try to kill me when they broke just wasn't the best feeling in the world.

As usual AWESOME work brotha!!!!

 

[shane90gsx]

I know your busy with this project. But let me just say I want one for a 1g.

 

[gofer]

Paul is going to anneal it so it will be fine.

 

[DSMnoobsause]

I havent read the whole thread but using cromo for the control arms might not be a good idea for a street car, on my old Malibu the chassis shop built my car out of cromo and I had a problem with the control arms breaking while driving down the road, broke one upper and two lowers, reason was because the material is brittle and will break not bend like mild steel, once he figured out the problem and fabbed up some mild arms I never broke or even bent another arm, driving with a broken arm feels like driving with a flat tire, the car didn't try to kill me when they broke just wasn't the best feeling in the world.

As usual AWESOME work brotha!!!!

Did they break at the welds or close to them? If so they were Probly using the wrong filler or wire if using a mig. We have no issues with the controll arms we make.

 

[arrowhead]

Shot me a pm and we can talk Paul. I'd be willing to help out.

Also Brian you you might want to really read the rule sets. You may find that the tube xmember puts you in classes that would be VERY difficult to compete in.

Kevin

What class or rules do you go by to build your cars?

 

[snowborder714]

NASA CCR/Time Trials rules, SCCA Solo rules, and Global Time Attack rules (which was drafted in accordance with the NASA CCR). I used to also use Redline Time Attack rules, but they are no longer. My guess is Kevin probably just uses the CCR/GTA rules and doesn't look at the SCCA book.

I use all of these so that I could compete in any if I want to. I have yet to find a major discrepancy/differentiation between these 3, but if/when I do, I'll probably go with the NASA rules over the SCCA rules.

 

[arrowhead]

NASA CCR/Time Trials rules, SCCA Solo rules, and Global Time Attack rules (which was drafted in accordance with the NASA CCR). I used to also use Redline Time Attack rules, but they are no longer. My guess is Kevin probably just uses the CCR/GTA rules and doesn't look at the SCCA book.

I use all of these so that I could compete in any if I want to. I have yet to find a major discrepancy/differentiation between these 3, but if/when I do, I'll probably go with the NASA rules over the SCCA rules.

Will look those over in NASA, I know that for road racing, (wheel to wheel), NASA and SCCA in the safety rules are very close, Just that class make up are different,
You guys deserve a lot of credit for keeping these cars within those rules and still drive them on the street.

 

[UGOT8UP]

Did they break at the welds or close to them? If so they were Probly using the wrong filler or wire if using a mig. We have no issues with the controll arms we make.

Upper broke dead center the other where 6" or so from the weld, he builds allot of the chassis for the outlaw 10.5 guys and a bunch of local stuff, he's pretty good at what he does and isn't afraid to charge for it, cost me 9k for my chassis, cage, mini tub and aluminum panel's.

 

[Phil1320]

I'm moving all my stuff to a brand new pole barn in about 3 weeks. So, I'll have more room for more projects again. And I'll be able to work on my dizzum again. I'll see about borrowing a 1G rear subframe from a buddy and building a fixture for it. It might be slow progress on it, but I'm sure I can whip up something pretty nice.

Glad to hear you say that!

On the chromoly vs. mild thing. I know it's beating a dead horse per se', but, I just wanted to hear your reply to this:

I've got a local acquaintance that has been fabricating for the better part of 30 years. He builds some of the sickest roll cages I've ever seen. More recently on some time attack Subarus. He prefers mild steel as well. Not sure he's said that Chromoly is weak, however, a term like "brittle" was used. He says the main reason is the WELDS not neccessarily the tubing or wall thickness. And, this is a guy whose welds look like they were done by a robot. With that, he's also involved in the Rally scene where cage strength is paramount over weight reduction, etc.......

Thoughts?

Second, I know of a local car that within the last year needed to have it's chromoly cage stripped from the car, and have mild steel installed - to pass tech inspection for SCCA competition.

So, everyone has opinions, but with my above examples......there's SOMETHING up with Chromoly use........

Again, a bit off topic, but, thoughts?

 

[greengoblin]

Where are the teaser pics at!!!!!!!

 

[99gst_racer]

Pics coming tomorrow. I'm seriously considering pulling an all-nighter and finishing up the fitting and tacking tomorrow.

 

[pos4g63]

Get some red bull and do it. We are all waiting impatiently. Nice work so far

 

[Yamahaulin]

Do it as I'm ready to figure out how much to set aside for one of these.