martymoose
Hero member
- Location
- Sydney, Australia
Does anybody know what is the correct size, I have 4 mm and 3.5mm.
Sf2/3C rear wheel spoke diameter
- Thread starter martymoose
- Start date
Tippie
Hero member
- Location
- Dr?bak, Norway
SF2 wheel here original spokes 4mm.
martymoose
Hero member
- Location
- Sydney, Australia
My 3c 4mm, the sf2 has 3.5, which has broken a spoke. Looks like somebody rebuilt the sf2 wheels with smaller spokes.
Dellortoman
Hero member
- Location
- Tasmania, Australia
I'd go up a size in any case. Original 3C wheels are a bit flexy.
Hey Marty, are we talking about the bike you just took around Oz? Did the wheel suffer some damage during the trip?
Oops, sorry. I shouldn't mention spokes. Somebody got offended when I last made a comment about a spoked wheel.
Major catastrophe, he broke one spoke. After the recent weather, I am amazed it's only one. I think I have some, will drag them along tonight for the club meeting. O beggar, they're not the standard ones, part of the bunch when I found 12 broken. Made by a local I won't recommend.
martymoose
Hero member
- Location
- Sydney, Australia
Yep swapped the sf2 wheels onto the 3c for the trip, ran tubeless. Noticed the broken spoke in Broome. About as far away as you can get. The other spokes held up the rest of the trip. Will, bless his cotton socks, stripped a few spokes out of my spare wheel and posted them to Perth. Luckily didn't need them. I will reassemble my spare wheel, maybe fit a new set of 4 mm to the 750 rim. Just another job to do......
Dellortoman
Hero member
- Location
- Tasmania, Australia
Did the spoke break at the bend where the hooked end goes through the hub, or through the threaded part where it goes into the nipple? Both are areas of stress concentration.
There was a quick chat about respoking at the petrol station before the ride among me and a couple of others who have had issues with broken spokes. That hub interface is such a complicated triple bend, that's 3 spoke bends at the hub, not triple-engine bikes. That's where all mine broke, probably because the builder was relying on tension to complete the bending. The later more experienced builder did mine way better and I have had zero issues in the couple of years since.
Dellortoman
Hero member
- Location
- Tasmania, Australia
The bend at the hub is where I'd expect them to break. If not done right it's just a break waiting to happen. The Laverda factory didn't get it right. They used a single "L" shaped bend rather than the more complex bend you describe Vince. So they were prone to spoke breakages at the hub as many owners will attest. It's a fatigue failure caused by a slight flex in the spoke on every wheel rotation, so tends to happen more frequently on bikes that have done a lot of miles.
With the best of intentions, I upset a fellow forum member a while back commenting on a 3C rear wheel that he'd just had re-spoked the way the factory did it, which (in my opinion) is less than ideal. Although with spokes that are thicker than original, or made from a stronger steel alloy, it would probably be OK. Especially on a bike that doesn't do high mileage.
With the best of intentions, I upset a fellow forum member a while back commenting on a 3C rear wheel that he'd just had re-spoked the way the factory did it, which (in my opinion) is less than ideal. Although with spokes that are thicker than original, or made from a stronger steel alloy, it would probably be OK. Especially on a bike that doesn't do high mileage.
I had my 3.0 rear, std is 2.5 relaced and it was done with the same ordination at the hub. All inners instead of inner and the next an outer. That all inners resulted in 12 broken spokes, found at home after a particularly fast run through the Petes Ridge sweepers and The Old Road, made my blood run cold seeing this at the time. He had made a simple bend on these spokes as well so who knows what really failed. When I picked up the wheel and asked why he had done this he said he had built mega-powerful Harley wheels and Supercross wheels just like that so it would be fine. Mmm. Pretty sure either have massive hubs and short spokes. Its such a specialized build these Laverda rears so take care out there.
Dellortoman
Hero member
- Location
- Tasmania, Australia
I think it's probably the Laverda rear drum brake hubs that are a little unusual. They have disk-like flanges requiring a double bend in the outer spokes - one bend in the hook at the flange hole, then another bend at the edge of the flange to direct the spoke towards the centre of the rim. Perhaps the hub flanges on mega-powerful Harleys are conical with a direct line from the spoke hole toward the centre of the rim, so they don't need an extra bend in the spoke to wrap around the edge of the flange. I admit I'm just speculating here. I haven't made a study of the hubs on other spoked wheels, although I've noticed that there's a trend more recently for spoked wheels to have the holes drilled radially in the hub, so the spokes have no bend at all. Moto Guzzi and BMW are examples that come to mind.
I haven't looked at one of these but I'm guessing that this approach is used with tubeless wheels, it may allow the spoke tension adjustment to be made at the hub instead of the rim, making it easier to seal the rim so the air doesn't leak out.
bazzee
Dellortoman
Hero member
- Location
- Tasmania, Australia
Why? Nobody wants a flexible wheel. Not even on a wheelbarrow. The only flexible part of the bike should be the suspension. Cast alloy wheels were invented to improve rigidity and make them more reliably circular.
It was the late, great, motorcycle racer and engineer Peter Williams who is credited with inventing solid cast alloy wheels for motorcycles. His wheels made their public debut on the race track in 1970, fitted to his Arter Matchless dubbed "Wagonwheels". The reason he did so was to create a stiffer wheel with less run-out than the spoked wheels of the day. He wanted greater wheel rigidity because his wire spoked wheels were flexing when heeled over in the undulating corners of the Isle of Man TT course, sending the bike off-line. With the stiffer mag wheels, he could hold full throttle through corners where he couldn't previously.
It was rigidity rather than weight reduction that he was trying to achieve initially, although I'm sure he was aware of the potential for light weight from the outset. I remember seeing a photo of his first set of prototype solid wheels in a bike magazine many years ago. I have a vague recollection that they were fitted to a Norton in 1968. I can't find that article or picture now, but the wheels were quite chunky with 6 massively thick spokes like flanged beams. I think the article said they were actually heavier than the wire spoked wheels they replaced, but a whole lot stiffer. It was only through design refinement in subsequent years that they became lighter than spoked wheels.
You may be right, but something has to flex. Racers often complain that the cycle parts are too rigid. If the wheel doesn't flex, forces are transmitted elsewhere.
Peter Williams was the modern inventor of solid wheels. Some ancestor contraptions had them, inherited from the wagon wheel, not to mention lenticular wheels as on the Blériot or Louis Clément.
Last edited: