Topic: Can I "cut and shut" my front hub?

[Terry in Australia]

Ok, so there I was, daydreaming about what might have been, JFK style. You see, I want to use either my Brembo 2 opposed piston calipers or some Nissin 4 opposed piston GSXR calipers on the Suzy GS1000 forks that I'm fitting to my Honda CB750 racer project. Now they may well fit between spokes and discs, but if they don't, I'm contemplating radical surgery.

I figure that if I cut a 20mm section out of the centre of my hub, I can then space the discs 10mm further out from the spokes giving me mucho clearance. Therefore, I thought I might set the front hub up in my lathe, and machine 20mm out of the centre, then have the 2 halves of the hub tig welded back together again, then I'll just make up 2 x 10mm adapters for the discs, to space them out from the spokes.

My only dilemma is that I'm not sure if this will reduce the rigidity of the wheel, by decreasing the spoke angle? I'm not concerned with the "nuts and bolts" of the engineering task as I'm confidant that it'll work, but not being an expert wheel builder, I'm not sure of the consequences of reducing the spoke angle. Does anyone know? Cheers, Terry.    

[Clyde]

Hi Terry,
I fitted Brembo calipers (08) to my Suzuki T500 which has a GT750 front end. I could not get the calipers to fit between the disc and the spokes, so I machined up a spacer to move the disc further away from the spokes and then milled a 3mm flat on each fork leg.
Just got  the calipers disc to line up OK
Regds
Your northern cousin
Clyde (with the beauuuuutiful F1)

[Raul CB750K1]

Hi Terry,

I'm definitely not a wheel builder expert, but the angle of the spokes definitely affect the strenght of the wheel. You know there is a "twisting" force when the brake is applied. The rim tends to roll, the hub tends to stop. Just imagine perpendicular spokes. In that case the wheel would twist like there is no tomorrow.

Raul


P.S. How do you get those mods road legal? In Spain they are so picky you have trouble just by changing the blinkers or the exhaust.

[Terry in Australia]

Hi Terry,
I fitted Brembo calipers (08) to my Suzuki T500 which has a GT750 front end. I could not get the calipers to fit between the disc and the spokes, so I machined up a spacer to move the disc further away from the spokes and then milled a 3mm flat on each fork leg.
Just got  the calipers disc to line up OK
Regds
Your northern cousin
Clyde (with the beauuuuutiful F1)

Thanks Cuz, I thought about that too, and I've got some pics of a GS1000S at Phillip Island (Greatest Motorcycle race track in the world, for my international friends) with Brembo's that seem to fit ok with just new caliper brackets, but of course it's fitted with mag wheels, not spoked rims. (see pic) I could fit the spare GS1000S mags, but I'd prefer to use spoked wheels, but geez those discs are already running very close to the fork legs now, and I don't know if milling a 3mm flat will make a lot of difference? Cheers, Terry.

[Terry in Australia]

Hi Terry,
I'm definitely not a wheel builder expert, but the angle of the spokes definitely affect the strenght of the wheel. You know there is a "twisting" force when the brake is applied. The rim tends to roll, the hub tends to stop. Just imagine perpendicular spokes. In that case the wheel would twist like there is no tomorrow.
Raul
P.S. How do you get those mods road legal? In Spain they are so picky you have trouble just by changing the blinkers or the exhaust.

Hmmnnn, I dunno Raul, some trail bike hubs are narrower than mine, and yet have larger diameter rims (normally 21 inch, but 23 inch rims were very popular a few years ago) so the spoke angle would be pretty narrow I would imagine? I'm also going to be running a smaller dia than stock front rim, (18 inch, down from 19 inch) so this would have to be ever-so-slightly better than attempting the same mod on a 19 inch rim, if in fact the rim width and spoke angle is that important?

How do we get away with these mods? Well, I haven't gotten away with anything yet, but luckily the "licensed vehicle tester" guy who writes up the "Roadworthy Certificate" that I have to furnish to the RTA (DMV?) is a friend of mine, and he'll probably be doing the tig welding, ha ha! Oh, and the turkeys who work at the RTA are "Public Servants" who usually get these jobs through nepotism (i.e., their father/mother/uncle got them the job) and are mostly too dumb to breathe without prompting, so when someone shows up with an old bike and all the right forms filled in correctly, any "mods" usually go pretty much unnoticed. Cheers, Terry.

[bryanj]

Hi In UK bikes under 10 years old have to comply to "Type Approval" which i think is what Raul is referring to. What we could do Raul is you build something radical that is over 10 years old bring/sell it to me in UK and I register it here and then sell it back to you and you reimoprt it as a another EU member state import which in theory means they have to accept it. A bit long winded but as my future father in law says " there is more than one way of killing a pig, asside for loving it to death"

[Jonesy]

This book applies to bicycle wheels, but I'm sure a lot of the engineering involved would be applicable to motorcycle wheels as well. It shows how to lace wheels as well.

[Raul CB750K1]

Hi In UK bikes under 10 years old have to comply to "Type Approval" which i think is what Raul is referring to. What we could do Raul is you build something radical that is over 10 years old bring/sell it to me in UK and I register it here and then sell it back to you and you reimoprt it as a another EU member state import which in theory means they have to accept it. A bit long winded but as my future father in law says " there is more than one way of killing a pig, asside for loving it to death"

It won't work Bryan. That's what I tried when registering my CB750. The idea: if it was homologated in Germany thirty years ago I should be able to buy it now and bring it over here, shouldn't I? No, I can't. Every single vehicle in Spain, in order to be roadworthy, must undergo a type homologation. If it has been homologated in any other EU country that would be enough -example: Mercedes doesn't have to homologate their models in Spain if they already did it in Germany, because there is an homologation code-. But old vehicles doesn't have homologation code, so no way.

I can always pay an engineer who will write down the paperwork and authorize the homologation: about 600 euros. Or I can go the "simple" way of registering it as Antique Vehicle. They are allowed to circulate with certain restrictions -for example, a 30's car could be forbidden to be ridden at nightime because of the use of carbide headlights-, but the drawback is that the antique vehicle must be in stock condition. You have to pay another certification company to issue a certificate stating that the vehicle is stock. One way or another, you have to pay!!!!!