Originally Posted by
EBikeFL
That should be Marathon Supreme and not Plus.
Normally, the rear spokes are 1-2 mm shorter on one side but if you need to move the rim more over to one side to fit the larger width tire in the forks then that 1-2 mm won't be enough and you'll run out of threads before you get the spokes tight enough.
Sapim spokes are very good. You can use 12 gauge on the rear and 14 gauge on the front. Only the 12 gauge are thicker and if you have eyelets on the rim spoke holes they may need to be drilled out. Spoke washers are also a good idea.
You'll need to calculate your ETRTO; this
page will help. The ETRTO for the 20" inch Big Ben is 55-406.
You obviously know about bikes way more than I do, but I disagree. Here's what I did:
I took the "worst case scenario", in which I get 2.15 tires (Big Ben). My current tires are 1.5". So, 2.15 - 1.5 = 0.65. Divide that by two (both sides of wheel), and convert to mm, that's 8.25 mm. I currently have at least 10mm of space between each side of the fork and the wheel. Same with the back tire.
Regardless of the spokes issue, can I put those Big Ben tires on my rims? If yes, then I'd like to try that first without buying new spokes. I can buy those from the LBS if I find out I need them.
Thanks.