Topic: original front hub w/ GSX-R front end

[Retro Rocket]

I actually know someone here locally that could easily do these but the costs for anything "engineered" here in Australia is ridiculous, thats why i get most stuff made in the US. Thanks for the offer Frank but I have another member here thats already made me some pretty awesome parts and he's getting the work, he's offered me a great price to do all 3 sets eventually. Thanks again for the offer. I will get another frame kit at some stage though {lets get the email addy right this time} 

[sinister902]

If anyone cares, I actually just sat down and spent a couple hours doing the ACTUAL math comparing the GSXR axle to the CB550 axle. If you leave the match basic, the GSXR hollow aluminum axle in a GSXR wheel(hub) would flex 1.8x less than a solid steel 15mm axle IF the load was concentrated at only the centerpoint of the axles. Since this is split over two equal bearings, that distance between the bearings in a cb550 hub vs. a GSXR hub, the 15mm steel solid axle flexes 1/3 as much as the hollow aluminum at the bearings. That said....less flex may not be better....

EDIT:

The cross-sectional area of the solid steel axle is 0.2739, the cross-sectional area of the hollow GSXR axle (accounting for the ID missing) is 0.274

I was blown away how close those numbers are.

The ultimate shear strength of the steel when cross sectional areas are that close is more than double.

ultimate shear yield point is 22Ksi for the aluminum, and 34.8Ksi for the steel. about 33% in favor on steel.

The modulus of elasticity of Aluminum is 10.2E and the steel is 11.5E this is where the calcs got to what I said above. unless the load is concentrated exactly on the middle of the axles, that is the only way the aluminum axle is "stronger"

[GV1390]

I can finally sleep tight now knowing my hodge-podge build may make it around the block.

[sinister902]

I'm gonna look into more....like bearing ratings and stuff. If I find any of it to be worrysome, I'll be re-designing the couple front end swaps I did on my bikes.

[sinister902]

Stock CB front bearing is a 6302-2RS
Dynamic load rating Cr: 11,400 N
Static load rating Cor: 5,400 N
Limiting Speed:
Grease Lubrication: 13,000 RPM

GSXR bearing is a 6205-2RS
Dynamic Load Rating (Cr)   14,000
Static Load Rating (Cor)   7,850
Max Speed (Grease) (X1000 RPM)   13

the load ratings are a touch higher on the GSXR bearings.....but I doubt a cb550 in just about any form is going to be CAPABLE of exerting forces strong enough to see the numbers that separate the bearings.

The only things I think would be a point of failure in GSXR parts vs. CB550 parts with adapters, is the hardware holding the rotor to the wheel. I used stainless hardware on mine for piece of mind, and the stock GSXR bolts from rotor to adapter....I figure they are designed to shear before something else does as a safety feature and don't want to put stainless hardware there that could possibly make something dangerous.

Edit:
if one were to swap wheel bearings to put a GSXR axle into a CB550 hub, you'd need a 6004-2RS bearing
Dynamic Load Rating (Cr)   9,400
Static Load Rating (Cor)   5,050
Max Speed (Grease) (X1000 RPM)   17

so, this is actually less safe than the steel axle on stock size cb550 bearings, as you decrease the load ratings by quite a bit in order to use the GSXR axle.

[calj737]

A problem I see with using an adapter to mount the rotor to the stock hub is the axis of the rotor occurring beyond the line of the bearing. The bearing dissipates force onto the axle, and if the rotor/adapter are outside of that, then all load ratings are off.

And don't underestimate how much load a moving motorcycle with a rider under breaking pressure can create on an axle. A thru bolt mounting a rotor thru and adapter then thru a hub has a very different shear load than a short, equal strength bolt mounting just a rotor. (Since you're calculating material properties...)

[sinister902]

for sake of discussion, what about offset rotors? some factory sportbikes use offset rotors up to 18mm of offset....I did mine a little different than gennaro, instead of using the 550 wheel with through bolts I used a later 750 wheel that was 5-bolt pattern and was already threaded...so I have 25mm long bolts mounting the adapter to the hub, with a 12mm wide adapter and an 8mm offset rotor from a VZ800. similarly on my XS750 yamaha triple I posted earlier in the thread, it's the same setup....short bolts holding the rotor adapter into the factory wheel just as the stock rotors were bolted on and there I used RC51 rotors which are also offset (basically what I do is use a 6-bolt rotor in correct diameter on the xs cause the stock rotor was 6-bolt, and on the cb I used a 5-bolt 750 wheel to use a 5-bolt rotor in the same fashion)

I still think in the case of a cb550, the frame strength is going to cause an issue before these front end mods ever could. the frame would fail first.

[ttr400]

Just to clarify, if you are talking about the GSXR600 around 2011 or so.  this bike does not use an aluminium front axle (i don't know of any superbikes that use aluminium for a wheel axle).
Material: Steel
Part #: 54711-14J0
Weight: 376 g
Size: OD 22mm
ID: 17mm
One end OD 28mm, other with M20 thread.

Kevin

[sinister902]

for that, the calculations are bunk as soon as you realize the modulus of elasticity is the same and the cross sectional area is essentially only different by .0001

[FunJimmy]

That's fine if the axle is only stressed by forces transfering through the hub and bearings but the primary reason for large diameter hollow axles is to ensure parralel flex free alignment of the lower stantions. That's even more important with USD forks as there is no provision for a fork brace.

[calj737]

That's fine if the axle is only stressed by forces transfering through the hub and bearings but the primary reason for large diameter hollow axles is to ensure parralel flex free alignment of the lower stantions. That's even more important with USD forks as there is no provision for a fork brace.

A perfect example of math and calculations will only get you so far. Understanding the application is the delta between knowledge and experience.

[sinister902]

I understand the design for supersport bikes, that see speeds over 180mph and some serious cornering forces in race situations and trackday situations. But What I'm trying to say here is these cb's with those same suspensions on them are not going to see 180mph and the hard cornering a supersports bike is designed/capable of, at least for 99% of the people doing the swap. Supersports bikes are also not the only bikes that use the inverted forks. In 1994, the first sport bike to use them was the GSXR, which at that time had a solid 20mm axle on 20x42x12 bearings. The 97+ suzuki maurader and boulevard use inverted forks, with a 17mm solid steel axle on 17x40x12 bearings. Are these magically not roadworthy either? I agree that a lesser axle design is dangerous, if all of the variables were the same (I.E. high speeds and hard cornering above and beyond the average rider's capabilities)

I also don't agree with saying there's a lack of provision for a fork brace.... while one wouldn't be small or visually simple, it's not impossible to tie the two caliper mounts and/or fender mounts from the lower stantions together over top of the tire. It would just be large and unattractive and aerodynamically unfavorable.