Looking for a little direction re choosing the best rim width for my fat bike. I’ve currently running a Marge lite paired with a 4.8 Bud on the front (with a 29+ rear) and to be honest I think it’s great.

However, I’m about to go full fat (with another Bud on the rear) and order some new carbon rims but after much reading and listening to various podcasts I’m beginning to think I’m missing out on something really special with wider rims. My head is full of ‘correct’ rim / tyre combos, optimum ratios etc etc

What’s the real world experience behind wider rims given that I currently think the 65mm front rim with a Bud is great. It has loads of float, turns in nice & quickly for the techy trails I ride, at 5psi it hasn’t yet folded over in corners nor does it have any decernable self steer. My thinking is based on a slightly narrower rim gives the tyre a more rounded profile which aids a quicker turn in. To be clear I’ve not really ridden anything else properly to be able to compare.

I’m leaning towards staying with the 65mm setup as it’ll shave a good 150-200g of each end and I like the quick handling I’m currently enjoying. Or….should I go for the 80mm+ rim?

Help!

You only really benefit from wide rims when riding in really soft conditions e.g. Snow! Been running 65 mm carbon rims with both 4″ and 5″ tyres and never really encountered a situation yet where a wider rim would have helped and never noticed sidewall collapse even at 3psi. Maybe my view will change when I go to Rovaniemi next month? Another benefit of narrow rim is reducing rim strike.

I’d say much wider than 65mm and you’re out of plus territory and into proper fat.

I’d be inclined to revisit Sheldon Brown on rim/tyre widths, consider what a lot of extra metal will do to weight and have a good think about what you actually want from this bike. Check what to can actually buy/accommodate width wise too, and possibly try to ride/revisit some real Fatties including the current 650b Farley if you’re worried about 26er wheels.

My gut feeling is that if you’re never going bigger than 3″ and want speed over all-terrain hulksmash, 65mm is probably enough…

My gut feeling is that if you’re never going bigger than 3″

Sorry but your gut is very wrong, I’m going full fat!

My frame has full fat spacing so no issues with any of the fat options.

I’ve not ridden 65mm rims, but I’m running 80mm rims now and am happy with 4″ Floaters. I’m not sure how much difference you would notice really, is there any way you could borrow to demo some 80mm rimmed wheels?