Topic: 17 in. wheels on CB 750

[simon#42]

avon and i think bridgestone still do 16 inch front tyres which are pretty good , they are sold for the early fireblades . i still have a couple of 250 race bikes that have 16 front wheels and the avon am22 tyre works well. modern gp bikes  use 16.5 wheels but before the one tyre rule michelin where trying 16 rears again

[Terry in Australia]

With the extra traction afforded by the 17" choice of rubber that you put on the bikes nowadays,I would suggest bracing an older steel frame in several places first.
When I modified my 750F2 frame I placed a horizontal tube across the frame where the frame tubes bend from the rear tank mount down to the swing-arm pivot.I then brazed in fillets of tube to stop the frame twisting here.
I also inserted a bracing tube across the front down tubes just above the front engine mount points.
Also,where the tubes come down from the rear tank mount into a 'V',below where the oil tank and electrical bits are,I placed a tubular fillet at the bottom of the 'V'.
When I cut out the cross member for the centrestand, I brazed in a piece of 531 tube to replace this.

I fitted replacement wheels in the same sizes as a 1988 GSXR1100J ie.a 110x18" Metzeler CompK Me33 with a 140x18 CompK ME1 on the rear.The standard F2 swingarm was modified using phosphor bronze bushes only.

Excellent info mate, have you got any pics of the braced frame? I'm bracing two frames at the mo', so I'm interested in seeing other frames that have been braced. Cheers, Terry.

[MCRider]

With the extra traction afforded by the 17" choice of rubber that you put on the bikes nowadays,I would suggest bracing an older steel frame in several places first.
When I modified my 750F2 frame I placed a horizontal tube across the frame where the frame tubes bend from the rear tank mount down to the swing-arm pivot.I then brazed in fillets of tube to stop the frame twisting here.
I also inserted a bracing tube across the front down tubes just above the front engine mount points.
Also,where the tubes come down from the rear tank mount into a 'V',below where the oil tank and electrical bits are,I placed a tubular fillet at the bottom of the 'V'.
When I cut out the cross member for the centrestand, I brazed in a piece of 531 tube to replace this.

I fitted replacement wheels in the same sizes as a 1988 GSXR1100J ie.a 110x18" Metzeler CompK Me33 with a 140x18 CompK ME1 on the rear.The standard F2 swingarm was modified using phosphor bronze bushes only.

Excellent info mate, have you got any pics of the braced frame? I'm bracing two frames at the mo', so I'm interested in seeing other frames that have been braced. Cheers, Terry.

Yes I agree. I was wondering how to do some bracing in those areas and I can picture exactly what he's done.

I think the bracing on my project is sufficient for what its intended purposes are. I have another project waiting n the wings that could stand this treatment.  THat is the horizontal by the front motormounts, with fillets to make triangles, and the horizontal below the rear tank area, with fillets. THat would make a serious stiff frame.

Mine has triangles at the rear tank area, front tank area, above the swingarm pivot, and the steering head gussets are welded shut.

[Retro Rocket]

It also has to be said that you can "over brace" a frame as well, there has to some flex in the frame or it becomes too rigid and will expose weaknesses in the frames integrity......Did i say that right.?

Mick

[MCRider]

It also has to be said that you can "over brace" a frame as well, there has to some flex in the frame or it becomes too rigid and will expose weaknesses in the frames integrity......Did i say that right.?

Mick

That's true. Our frames are so bad to begin with lots of work is an improvement. Going overboard is difficult. Note the 1988 Kawa Frame gusseted by Tony Foales in this article.
http://www.tonyfoale.com/  Go to the "articles" button, scroll down to "Frame Stiffening". And scroll down in the article a ways.  That frame is seriously gusseted.

Tony does make the caveat in the last paragraph. A stiffer frame may likely expose weaknesses elsewhere.

For me, and likely for most of us, gusseting a frame is just a "hey look at me" exercize as I doubt that I'll ever ride hard enough again to put it in play. Though I maybe did at one time.     "The older I get, the faster i went".

[Retro Rocket]

Actually MC, i have had some pretty good handling 750's over the years, all were braced and wore steering dampers, I know stock they were a little unstable but honestly, considering the age of the design in these old bikes, i think they can be made to handle really well and yes, i used to ride the wheels off mine, never had rear sets on one and found , apart from the centre stand which i always removed, the foot pegs were the biggest problem i had, they were way too low for hard riding. I picked up the back wheel a few times sliding around a corner on the bloody footpegs......oh to be young and fearless again....

Mick

[MCRider]

SNIP

oh to be young and fearless again....

Mick

Yup...sigh

[754]

I looked at 2 16s today,
 a sportbike looking front wheel of I suspect a mid size bike, was shod with a Dunlop K630F in a 100/8- 16

 and the steel rimmed Honda rear, wore a Dunlop K291S 120/90 -16.

 Got one more somewhere, a mag 16 front that matches an 18 rear I picked up.. I grabbed the 18 cuz it was a 3.00 wide.. HTF
 not sure what it is from, 3 double spokes, 5 bolt sprocket, with lots of offset?