I rode the Munda Biddi Trail in Sept/Oct 2024, 14 riding days and two rest days, on a rigid 29er mtb, running 2.1 Vittoria Mezcals. Which was perfect for me. Aspects of the ride that I think are better on a mtb:
1.Position on descents. There are many short sharp climbs on the MBT, and equally plenty of descents which mostly aren’t technical, but might be bumpy or overgrown (depending on time of year). For me, I have better control when descending on a mtb over my gravel bike.
Load carrying. I find my rigid 29er “sits down” into the trail when it is loaded up, and in some respects handles even better when loaded. The gravel bike I find isn’t as good with a touring load, which makes the steering a little heavier and more wandery. (Wandery is absolutely a word, what are you talking about).
My rigid 29er is a Specialized Carve from 2012, SLX groupset, with a Trifox carbon fork.
With respect, it sounds like you were doing day rides on the trail with your gravel bike. That’s quite different to riding with a camping load. Yeah, the pea gravel is more in the northern parts, but the southern sections include a couple of days of sandy stuff (in the forests between Walpole and Denmark).
Y’all got me looking back through my photos. That sandy bit down south was SO scenic, and the forest sections are bliss.
In fact my ipad Home Screen is one of my fav photos from that ride.
It’s such an awesome ride.
Done to Nannup on an XC duallie in November so dry. We saw mainly hardtails fully loaded and a Swiss family with Bob trailers and carrying their kids bikes when they got tired . Mates kept going, they had mud and sand and on mtb . As others have said most of the gravel is in the northern sections.
We weren’t loaded up though. I could’ve done it on my gravel bike ( 11 speed 1x GRX with an XT di2 RD to get to 46 at rear ) . There’s sections like out of Wellington Dam you just walk on any bike! I’m changing to 12 speed soon out to 51 but I wouldn’t need it on this trail.
There are some short, steep bits down so might come down to what you’re comfortable descending on.
Mates just done it on gravel bikes loaded with the lightest kit they could get and were happy . SRAM mullet . Both trips we are all > 50 but been riding a long time.
FB page will tell you a lot.
Take a snake bandage, tigers were seen a fair bit beyond Nannup . Prob Browns closer to Perth.
I completed the Mundabiddi from north to south in April this year on a gravel bike with the 2x GRX group set and 43mm gravel king tyres. I am 60 years old and found a couple of the days quite long but found the bike well suited to the terrain. Just note that the extent of the vertical and pea gravel can make the ride harder than it looks on paper and treacherous on some corners. But you will have a great time.
It might be worth checking out Bikingreen chainrings (ebay), available in 46x30 to fit Shimano 110BCD 4 bolt road cranks. These use a few tricks to shrink the inner ring, so the chainline moves in a few mm; I don’t know if this would matter with Di2. If you fit these you might also need a “FD dropper” to move the FD down, Sugino make one, plus there are clones on Aliexpress.
At the other end, at least a 40T rear cog will work with a GRX 2x12 RD; Shifting Big Gears with Shimano GRX Di2 12-Speed: 11-40 Cassette - Gravel Cyclist tested this. 11-39/40/42/45 cassettes are available from ZTTO (Aliexpress). As far as I know nobody has tested >40T with 2x12 GRX, but with 11 speeds 42T was usually okay, sometimes 46T.
If you haven’t seen this it’s worth a look:
Re tyres; You should be okay with 45mm provided you exercise some care, but I definitely wouldn’t go smaller. Wider would be more comfy, but a new bike isn’t going to be cheap.
