So here is the story: the other day, I found in a garage sale a vintage moto-lita (probably genuine, but not sure), that was mounted on a Triumph Vitesse in the late 60's. it came with a Triumph center cap. I'm not an expert in Triumph so, I don't know if it was an option at the time, my bet is that it's an after market of some sort.
the wheel was in terrible condition, but I thought it could be a good idea to learn and practice how to remake a steering wheel. here is how it looked like when I bought it: 
the leather is completely coocked, and falls appart just by looking at it with a mean face. but the rest seem to be in good shape. so I scrapped the leather, and peeled off the rubber/foam that covers it. here is how it looked like:
after a few hours of polishing and gentle sanding of the most corroded parts, I ended up with somethink like that:
it's shinny again and I could remove most of the scratch using 1000 sanding paper.
the foam was in decent condition, so I cleaned it and glued it again. it's more tricky than it sounds: indeed if the ends of the rubber do not exactly match, it will be visible with through the leather. any irregularities will do. so be careful if you do it. wrap it good so it stays in place.
Another tricky part is the width of leather you have to cut:
if it's too long, the wheel will feel squishy.
if it's too tight, the leather will loose its grain and look and feel terribly flat. plus leather is not that stretchy. So I made a test case using a little piece of leather. turns out that edge to edge, if it is 86mm in total, it will wrap nicely around the wheel with the tension cross stitch.
Now comes the real deal: I have to cut large pieces of leather to fit the entire wheel. you can do it with one piece that you will stitch together at one end. but it's over a meter long and I did not have a skin that was large enough here. especially since I chose automotive grade leather, UV resistant. It does not come exactly cheap, so I decided to cut it in 3 pieces, with one junction at the top, and 2 junctions at the bottom, nicely symetric over the vertical axes but not equidistant, on purpose.
for that purpose, you want a rather thin skin (about 1.2 / 1.5mm max). because if it's too thick it won't feel right. and if it's too thin, it will be too stretchy.
Now before you put that on the wheel, you have to stitch your pieces as a leather band, that will be later put around the wheel. Here again, you don't want too tight or too lose. but if you cut your segments large enough, you have some room for tests.
on the long axis, I folded the leather and saddle stitched by hand. to join the sections of the band together, I use a french seam stitch. it's basically a very strong stitch where you join both pieces together on the nice skin surface, and fold the flesh face on the back and then only saddle stich those folded elements in place. you can use a thin foil of polyesther in the back for additionnal stretch, but to be aware: the more pieces you stack, the less stretchy it becomes. so it will become harder to fold around the wheel. the 2 bottom junctions are black stitches:
and I chose red for the top stitch, so it acts as well as top mark. it's still discrete and I thought it was a nice touch 
then the leather is put on the wheel, and folded around it. to keep it together, the traditional method seems to to a cross stitch using the loop of the stitch and not through leather. it adds some elasticity to the method and puts a bit less stress on the leather.
Here you can see a detail of it.
and here is the final wheel ! 
I'm quite happy because the leather kept enough grain. it's not too tense.
and all the metal to leather junctions are quite flat.
All in all, the end result is pleasing, I think. It could be improved of course. for instance, I could (should) have carved out the foam to accomodate the thicker seam stitching. but it's not too bad. Hope this helps someone if you decide to go for it.
what do you think ? 
cheers guys!
