Why Tubular Steel?

Wrecked944 · 01-23-2004, 09:58 AM

I hope this isn't a totally dumb question. I noticed that a lot of GT race cars are made of tubular steel. But why don't they use tubular carbon fiber like high performance bicycles?

Leland Pate · 01-23-2004, 10:08 AM

I always thought it was because CF tubing is only strong under certain types of loads. It seems like CF is weak when it comes to torsion... or was it compression. But is strong in other areas.

I dunno.

jluetjen · jluetjen's Garage

Steel is a lot tougher then carbon fiber, and also cheaper to engineer and fabricate. Carbon fiber works great if you can spread the loads out over a wide area, like a monocoque. Steel can be used the same way -- check out a stock 911's tub. While Carbon Fiber is very strong, there is a significant difference in the strength depending on the grain of the fabric. This is managed in carbon fiber tubs by careful design of the weave pattern, material choice and assembly processes.

Steel on the other hand is pretty strong no matter what direction it's orientated. It is also much tougher then carbon fiber. If you overstress carbon fiber, it shatters. If you overstress steel, it bends before it breaks. It can also be fabricated by any number of competant welders, and will often even work reasonably well if fabricated by a bad welder.

Keep in mind that the stresses imposed on a bicycle frame are a significant order of magnitude less then those imposed on a competition car.

jpnovak · 01-23-2004, 10:11 AM

Probably due to safety. steel will absorb an impact as it bends. CF will just explode and shatter. Not so much of an issue on a motorcycle where you don't have a cage of protection around you.

Leland Pate · 01-23-2004, 10:13 AM

... yeah, I was going to say that too.

Tim Walsh · Tim Walsh's Garage

I don't know CF that well at all but I would think that the steel would make for quicker repairs trackside compared to CF.

Emission · Emission's Garage

I'd say cost, then safety.

Randy Webb · 01-23-2004, 10:38 AM

One other note -- there are some really killer steel alloys out there now -- PAG has insisted on using these high strength steels in all their cars -- even in parts of the C-GT.

I think the next step up would be to use a Ti unit body -- we just need to melt down a few more Russian submarines.

anh911 · 01-23-2004, 10:39 AM

Cost - if you have an F1 budget it's CF, otherwise for the most part steel is much cheaper and easier to work.

Kevin Stewart · 01-23-2004, 11:18 AM

I just cant imagine a cost effective way to join the tubes of a cage or a webbing structure to support the chassis, Kevin

Fritz · 01-23-2004, 01:14 PM

Cost and maintenance!!!

If you want to make a CF chassis strong enough for a 2,500 lbs race car to handle the stresses of 150+ mph and the various impacts get your wallets out. Hence the cost of a F1, CART or LeMans Chassis.

Repairs......don't even think about it with CF. Ask someone who works on F-18's!!

Tubular Steel....not too tough to find someone who can weld a crack or cut and weld in a new section when you get a bent tube.