Cyclocross - Pressures for CX sew-ups?

I'm new to CX. I weigh 175 lbs.

I have a pair of 35mm Ritchey CX clinchers that I've been practicing with on soft dirt trails at 40psi. They seem dandy, no pinchflats, plenty of cush.

But I just acquired a pair of lightly used CX sewups: a 28mm Tufo Rhino and a 26mm Barum. I've heard that a cool thing about sew-ups (tubulars) is that you can run them at 35psi.

I also understand that you change the pressure depending on conditions.

Any idea of what range I should expect to use my new (old) sew-ups at?

Should I run the 26 tire harder than the 28? Or is that being too picky? I have the 26 on the rear and used it on a rooty trail today. Both were at 45psi and it seemed like I might put flat spots in my rear rim. It felt bad fairly often. The front felt fine. I put the 28 on the front coz it has fresher tread and I thought it might be good for cornering but maybe I should've put the wider tire on the rear to protect it from my harsh weight.

What about a firm dry trail plus some pavement?

Is it a real bad idea to ride these much on pavement? I want them to last as long as possible so I plan on avoiding pavement. I have a 10 mile loop I like that has a couple miles of pavement...but maybe that's even too much for such soft rubber knobs?

Any tips?

I'm new to CX. I weigh 175 lbs.

I have a pair of 35mm Ritchey CX clinchers that I've been practicing with on soft dirt trails at 40psi. They seem dandy, no pinchflats, plenty of cush.

But I just acquired a pair of lightly used CX sewups: a 28mm Tufo Rhino and a 26mm Barum. I've heard that a cool thing about sew-ups (tubulars) is that you can run them at 35psi.

I also understand that you change the pressure depending on conditions.

Any idea of what range I should expect to use my new (old) sew-ups at?

Should I run the 26 tire harder than the 28? Or is that being too picky? I have the 26 on the rear and used it on a rooty trail today. Both were at 45psi and it seemed like I might put flat spots in my rear rim. It felt bad fairly often. The front felt fine. I put the 28 on the front coz it has fresher tread and I thought it might be good for cornering but maybe I should've put the wider tire on the rear to protect it from my harsh weight.

What about a firm dry trail plus some pavement?

Is it a real bad idea to ride these much on pavement? I want them to last as long as possible so I plan on avoiding pavement. I have a 10 mile loop I like that has a couple miles of pavement...but maybe that's even too much for such soft rubber knobs?

Any tips?

what are the conditions you are riding in? Tubulars that are that narrow are great for extreme mud, but are going to be terrible for some (I would say the majority of cross races throughout the country.) races. It sounds like you were feeling your rims at 45psi, which means that you are not getting the low pressure benefit that you were getting out of clinchers.

If I were you I would ditch those tires and get a good all around tubular like a 32 cubus.

+1 on the narrow tubs probably being mud tires. I wouldn't race on those unless there was some deep mud to slice through. Most of the time I ride tubs in 32 width. I weigh ~180 lbs and run them ~29psi, sometimes a little lower if the conditions are slippy.

Typical tire is 32. Those super narrow tires probably will ride worse than the clinchers you have now unless you are riding through thick peanut butter mud.

I ride 32 Challenge Fangos and start at 24/26

I found this link last night - looks VERY good to me - tubulars vs tubeless vs clinchers, brands and models, getting pressure right - everything: http://themichiganscene.blogspot.com/2008/11/tms.html The comment someone added about using a separate high quality pressure gauge was interesting; I had no idea the gauges in pumps are so poor.

It depends on a lot of things including the tires. Tires with really supple side walls will need more pressure for the same 'feel'. A good rule of thumb is to pressure up your tires and hit the course. If you bottom out once on a nice bump like a root or something then you are probably real close to ideal pressure. If you are bottoming out a lot then increase pressure.