CZ never fitted a disk front brake to their 350s, so the recognised fix is to use a disk front wheel, handlebars, caliper and right-hand lower fork leg from a slightly later Jawa - same forks, same wheel size. The problem is that the Jawa rims were and are always steel, the CZ 350 rims always alloy, so using a Jawa front wheel gives a bike with one wheel chromed steel, the other alloy. Sadly it's not just a matter of swapping over the rims, because although both rims are 2.15x18 36-hole, the drum-brake CZ has a cross-over-one spoke pattern using "thicker" spokes whilst the disk-brake Jawa has a cross-over-two pattern with "thinner" spokes. Clearly, therefore, the disk-brake Jawa hub cannot simply be laced into the drum-brake CZ rim.
It is well known in Jawa-CZ circles that the alloy rims used on 1980s CZs are the same as those used by MZ in that period. It also looks from photos as though the ETZ 250 used exactly the same forks as Jawa-CZ, with the hub and disk on at least some disk-braked ETZ 250s seem identical to those used on the Jawa 350s. The one difference is that the ETZ 250 has a narrower 1.60 front rim than the CZ, which is 2.15, but all the photos I have found suggest that the ETZ 250 front wheel has thicker spokes laced in a cross-over-one pattern exactly like the drum-brake CZ! If my deductions from the photos are correct, this suggests that the disk-brake hub from an ETZ 250 could be laced into the rim from a CZ 350: special spokes might or might not be needed, but that wouldn't be a big problem. Maybe this states the obvious, but the material difference between an MZ-origin hub and a Jawa-origin hub that are essentially the same item looks to be that the MZ hub will have been drilled for a cross-over-one spoke pattern and thicker spokes like the drum-braked CZ.
So now four questions.
One. The first photo attached shows a Jawa 350 front wheel with the type of hub and disk I will be using: does this look to you like the hub and disk from an ETZ 250?
Two. The second photo attached shows a CZ 350 front wheel with standard spokes and lacing: apart from the hub, does this look to you like the spokes and lacing from a disk-braked ETZ 250?
Three. Where can I get either a disk and hub for an ETZ 250, or an entire disk-braked ETZ 250 front wheel, second hand?
Four. Can you see any reason why what I am proposing would not work?
Thank you.
Bob Clark
