I'm planning my second Everesting, so thought that as well as climbing lots of hills to prepare my legs, I should do something to prepare my bike. I have one proper road bike which I use for club runs and audaxing. Audax is bikes are partly about comfort as over that kind of distance discomfort eventually becomes pain, which slows you down a lot. Anyway, it is supposed to be enjoyable, mostly. Maybe some type-2 fun, but hopefully not type-3.
I've pretty much decided on The Burway for my next Everesting, even though I won't be the first.
I'm conscious that with Everesting there's a lot more climbing than even the hilliest audax. The Cambrian 200 is one of the hilliest and even that has under 4000m of climbing. Everesting means 8848m in as little as 180km. When climbing, weight makes a huge difference, so some of my modifications are to reduce weight. I've removed the mudguards, the bell and the pedal reflectors and swapped my dynamo hub wheel for a standard one. The weather looks good and I hope not to be riding too much into the dark, so hopefully this will be OK. I've also swapped out my Brooks leather saddle for a simpler and lighter Charge Spoon. If this isn't quite as comfortable I'm hoping it won't matter as I tend to stand up for the descents and maybe parts of the climbs.
I've switched to some 25mm Continental GP4000 tires I have but rarely use. These are fractionally lighter and also roll a bit faster, which is a bigger proportion of energy usage uphill when aerodynamics are negligible.
I haven't spent a huge amount of money to do this, just bought a couple of cheaper bits. No doubt you could save a bit more weight by spending more. The titanium frame is light, but not as light as some carbon ones. Still, I've got the weight down to 8.6kg.
The other significant change I made was in gear ratios. The Burway has a 20-25% section which I can easily get up with 34x29 when I'm fresh. However recent training rides on a 18% climb make me think that will become very hard after a few repetitions. I'd like to have the option of standing or sitting to climb, even when my legs are tired. So I had a look at Spa Cycles and found a cheap triple chainring that would do the job. the smallest ring is 22 teeth, which gives a lowest gain ratio of 0.69 (or 18.1 inches), compared to the 1.07 (or 28 inches) I had previously. At 90 RPM that's 7.8kph, probably a realistic speed for the steepest part of the climb, though I expect my cadence will drop further when tired.
I only have a shifter for a double chainring and didn't want the hassle/expense of buying and setting up a full triple at the moment. So I thought I might as well remove the two larger rings and for that matter the front dérailleur. A little extra weight saved.
I can still shift between 32 and 11 tooth cogs on the back, but this means I can't pedal fast enough much beyond 25kph, so I may be a bit slower on the flatter bits of the descent. I'm not too worried about this as I think the climbs are more important to the overall time. Ideally my front ring would be about 28 teeth, but I don't have one of those without spending more money or pulling apart my hybrid.
I've also replaced the chain as it was getting worn and set the length of the new one for the small chainring. I guess when I switch back to my double I'll need a new, longer one.
I've also noticed recently that the fairly cheap wheels I bought about a year ago have had several nipple breakages, two when the wheel was just sitting in the garage. It looks like the nipples are made of aluminium rather than brass. Brass ones are a bit heavier (1g vs 0.4g by my measuring), but also more reliable. I don't enjoy the prospect of nipples breaking while out on even a short ride, so I've laboriously replaced them all.
EDIT: I made it!
I haven't spent a huge amount of money to do this, just bought a couple of cheaper bits. No doubt you could save a bit more weight by spending more.