I’ve done it on a CrossBike.
The only hard bits are the fast ruts down some of the descents where the chalk has rutted from walkers and rain.
I really enjoyed it and will be doing it again on my new CrossBike in Oct.
After the recent rain I’d go for something grippy in the tyre department and be *very* careful on bare chalk or where there’s a fine layer of clay over chalk.
But it’s doable on a cross bike if you’ve got the legs (and back and arms) for it.
I’d be wary of treating it as ‘fire road’ though. It is often fairly wide but a lot of the faster descents have fissures/broken up/slidey sections and you tend to hit them without much warning and traction on he steeper climbs can be a bit of a balancing act.
A friend and I are doing the SDW on saturday, being well prepared I’ve left my MTB back in Suffolk so only have my cross bike here. Would this be suitable? From what I’ve seen it all looks pretty fire-roady, planning on taking plenty of tubes