How much stress can a Suzuki GSX-R1000 motorcycle frame take? (Part II)
Posted by
Armand RossettiFebruary 17, 2009 5:14 PM
According to Total Motorcycle Website, the entire 2006 Suzuki GSX-R1000 (gixer) motorcycle weighs only 365 lbs.; that's only twice the weight of the average gixer rider. When Suzuki introduced the GSX-R1000 in 2001 Suzuki engineers had increased the thickness of the frame by 0.5 mm (a dime at 1.40 mm is almost three times the added frame thickness). After adding to the GSX-R1000’s frame thickness, Suzuki reportedly gained a 10% increase in frame rigidity over the GSX-R750.
Suzuki then took about 31 pounds off the engine by replacing the GSX-R1300 high performance engine with a modified GSX-R750 engine. The new engine had a bigger bore, longer stroke, pistons with lower crowns, and a gear driven counter balancer, all weighing 130 lbs. The new GSX engine was about a third of the total weight of the motorcycle.
The replacement engine was capable of delivering a whopping 143 horse power to the motorcycle’s rear wheel with a capability of 80 ft lbs. of torque. Combining all that power with only 365 pounds of bike weight, a rider could reach a top speed of about 180 mph. Likewise from a standing stop, the GSX-R1000 was capable of running a quarter mile in 10.1 seconds and finishing at a speed of about 142 mph. If a rider tromped on the throttle and counted to three the GSX-R1000 would be storming down the road at 62 mph and readying itself to be at 100 mph a few seconds later.
Suzuki seemed to have created a really light and rigid 180 mph thoroughbred racing bike for streets that weren't safe to ride on at 90 mph. For example, Suzuki trimmed four pounds off the exhaust system by using Titanium, a lighter, tougher and stronger metal, and it manufactured the front fork using low weight Titanium. With these engineering changes, Suzuki topped the performance of the closest competitor in the GSX's class, the Yamaha YZF-R1.
To keep the GSX-R1000 feather weight and speedy, Suzuki had to choose light weight metals for different parts of the bike. However, it seems curious that Suzuki did not use a Titanium alloy instead of Aluminum to make the GSX frame, especially when higher tensile strength would be necessary to counterbalance obvious frame stress factors.
Tensile strength is the stress at which a material (like Aluminum or Titanium) breaks or permanently deforms. There are three definitions of tensile strength:
Yield strength, which is stress at which material strain changes from elastic deformation to plastic deformation, causing it to deform permanently;
Ultimate strength , which is the maximum stress a material can withstand when subjected to tension, compression or shearing. It is the maximum stress on the stress-strain curve; and
Breaking strength, which is the stress coordinate on the stress-strain curve at the point of rupture.
For example, a certain Titanium alloy (Titanium + 6% Aluminum, 4% Vanadium) has yield strength of 800 MPa, while Aluminum has yield strength of less than half that number (400 MPa). The 6%Al, 4%V Titanium alloy has a much higher ultimate strength of 900 MPa versus 455 MPa for Aluminum. Why Suzuki chose Aluminum over Titanium alloy for manufacturing the frame while choosing Titanium alloy to manufacture the exhaust system baffles the mind.
To better understand why Aluminum might not have been the best choice for the GSX frame, we turn to the Suzuki Service Bulletin entitled Voluntary Safety Recall Campaign #2A08 2005 and 2006 GSX-R1000 Motorcycles Frame Reinforcement Brace Installation/Frame Replacement. That publication illustrates where the Aluminum K5 and K6 GSX-R1000 frames have been fracturing. The Service Bulletin also outlines reimbursement, and dealership/manufacturer responsibilities. The Bulletin also reveals VIN ranges for recalled GSX-R1000 motorcycles, the parts needed, and it establishes which motorcycles will not qualify for bracing. And it continues by providing frame inspection and reinforcement installation directions.
Suzuki's publication contais lots of graphics and pictures that reveal fractures on the underside of the frame and to the right and left of the steering neck. Accordingly, Suzuki has supplied a brace for the frame that is designed to span between and hold the two fracture sites together. And a mechanic has to either remove or detach several components from the frame, inspect the frame for cracks using a special, manufacturer supplied dye kit, and then use an epoxy adhesive to cement the brace to the frame before re-bolting the components.
In addition, some of the hardware had to be changed, and depending on temperature and conditions, the epoxy that glues the bracket to the frame has to cure anywhere from one to 24 hours before the dealership can return the GSX-R1000 to its owner. The dealership then has to submit a claim for each frame repair (labor taking three hours) or frame replacement (labor taking 11 hours). The dealership then has 10 days to return replaced frames for credit.
Suzuki service centers also received a copy of its January 21, 2009 recall letter, which outlines the reasons for the recall, and explains reimbursement. Lastly, the Service Bulletin contains a request worksheet and Fax form.
After reading all of the above information, it seems reasonable that Suzuki should have engineered the frame to better withstand ordinary forces that occur during daily use. Once again, those ordinary forces might include a 160 lb (average) rider sitting over a 130 lb. engine, and other accoutrements, all located smack dab in the middle of the GSX-R1000’s 55.3 inch wheelbase.
It is also interesting to note that the GSX-R1000 comes equipped with a front suspension that has a fully adjustable piggy-back shock absorber having a linear rate linkage system. The adjustable shock is attached to that rigid, lightweight Aluminum frame, having a combination cast and extruded spar construction for "precisely calculated rigidity."
Lets recapitulate. The GSX-R1000 is light, it's lightening fast, and the rider can adjust its front suspension to make the bike even stiffer while going over bumps in the road. Everything that has any weight; the engine, exhaust and rider...are sitting in the middle of the motorcycle, supplying a massive vector force downward. That downward force multiplies: as the GSX-R1000 takes ordinary bumps in the pavement; as its engine brings the bike to warp speed; and as the bike banks, turns and brakes while riding on uneven pavement. With all of this in mind, the centerpiece that is managing and supporting all of this "normal" activity is a thin, lightweight Aluminum frame. And to make that frame stronger and more rigid, Suzuki has tacked on what amounts to a third of the thickness of a dime's more worth of the metal.
For some reason, however, using high tensile strength Titanium to manufacture the frame was not in the cards, back then, as a Suzuki design option.
Lastly, on September 22, 2006, Suzuki updated the GSX-R1000 for 2007. The new GSX gained 14 lbs. over the 2006 model, and the engine and chassis were updated (http://en.wikipedia.org/wiki/Suzuki_GSX-R1000).