Originally Posted by
Wanderer
I don't think you will find 38s on there - more likely 32s or 28s. 32s will be fine,
Yes, I certainly couldn't have put 38s on my Sirrus. 32s will be a LOT better than 28s - but nearly as good as 35s. How wide a tyre is absolutely necessary depends partly on whether there a trail obstacles like stones and hard ruts, and partly on the weight of the rider. Setting your tyre pressure right is just as important as getting tyre choice right. These links should help, especially the second:
http://www.rivbike.com/article/components/tires
www.rivbike.com/article/components/pick_a_tire_
chart
you will probably appreciate the lighness of the Sirrus, over a bike that has suspension parts. It will be more nimble.
Cheap suspension is a bad joke. And suspension on a hybrid is a worse one. When a hybrid's tyres can't handle the conditions you are riding in, that's a sign you need a real MTB with room for wide rubber, a stronger frame and rims, and a geometry that is balanced for riding off road.
Oh - and if the dust really is hard packed then
avoid off road tyres with aggressive triangular teeth on the cornering surfaces. These are great for cornering on mud, where the teeth dig in nicely. But if you corner aggressively on a hard surface then the teeth will bend and so the can tyres slide out from under you. This is not nice!
An online friend just tested out those Duremes on hardpack with amazing results, if you don't like or can't fit them then google "hardpack tire 700c".
Re bike choice - a rigid (ie no suspension) 29er could be a good one. Google the phrase and ask for tips on deals on entry level 29ers on the MTB forum. These are the most versatile flat bikes around, tougher than a normal hybrid (they are just a beefed up hybrid really) but fast enough to hang on to a racing bike if they can get in its slipstream:
http://pfunwithpflug.blogspot.com/20...unon-road.html
Otoh, a standard 26 inch wheel MTB is a very versatile bike too and they are easy to find used.
If you've not bought the Sirrus yet, then I wouldn't. Depending on the model they can be part carbon and part aluminium, and mixed material bikes are more likely to suffer frame failures. Most of all, the Sirrus is just not designed for riding off road. The sharp frame angles and high main tube make it one of the last bikes I'd want to be on if the front tyre hit a rock at speed, or the back tyre slid on gravel. That doesn't mean that it is a death trap - you'd just have to ride a little slower and more carefully - but it is the wrong tool for the job.