750SF (1971) spoke length

J

jockula

Junior member
Location
Scotland
Hello, replaced my rear wheel spokes for a new set from Laverda paradies recently. They fitted up without any problem,however, the
previous rear set were short 100mm long where new set is approx 150mm long. Bike has Laverda 230mm drums/ 18" rims. I,ve had the bike
many years and would just like to know what the correct length should be. Pic 1, rear wheel with new 145/150mm spokes. Pic 2
front wheel with 100mm spokes. Are there different dimensions between grimeca and laverda hubs ? Unsure if I,ve ordered wrong set ?IMG_0585.JPGIMG_0583.JPG
Pic 1 Rear wheel with longer 150mm spokes
pic 2 Front wheel with shorter 100mm spokes
 
Lace pattern with Super Freni drums differs front/rear.

Rear pattern with its longer spokes is far stronger... in theory. Practice has shown the "normal" pattern (as used in the front wheel) is also up to the job, I had a 3.00" rim spoked in this manner in the rear of my 3C for many years without issues, until I got ambitious in regard to extracting extra power from the triple.

piet
 
There are lots of pages here about that subject, rear wheel respoking. Search to your heart's content. One helpful suggestion is to look for witness marks on the hub from spokes.
 
In the world of spoke wheel building it's 2-cross (rear) and 1-cross (front). It relates to how many other spokes (on one side of the hub) each spoke crosses over (or under). A lower cross gives greater lateral strength and a higher cross gives greater torsional strength - which is why the 2-cross is used on the rear wheel. The strongest wheel laterally will have 0-cross (ie radial spoking) but cannot provide more than marginal torsional strength (ie braking and power transmission). Bicycle wheels can have radial spoking on front wheels if they use rim brakes, but never if they use disc (hub) brakes.
 
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