|New Be Question tire pressure||Steve A|
Sep 3, 2002 4:45 AM
|What is a rule of thumb tire pressure for say hard pack, for mud, for grass ? Will be using Ritchy or Mich. tires
|No such thing||Eager Beagle|
Sep 3, 2002 7:32 AM
Any holes/jumps/etc in the course
The tyres you are riding
How fast you ride; and
When you run rather than ride.
The crucial factors are sufficient pressure to avoid pinch flats (where the tyre compresses completely against the rim, thus nipping the tube (assuming clinchers) and causing a flat). This will very much depend on the course conditions - it only takes one root/rock on an otherwise flat course to cause a problem - if in doubt, err on the hard side.
The other factor is grip/comfort - the softer the pressure, the bigger the contact patch, and the better the grip. Similarly, if you have them rock hard, a long training ride can get very hard on the tooth fillings. If you try to ride everything, grip will be more important than if you are going to get on your feet up the muddy/greasy slopes.
You will get a feel for it over time. As a very rough guide, I (at 210ibs) tend to run my much Muds at around 75psi as a good all-round pressure that keeps me pretty safe from pinches. If I have my big fat Schwalbes on, I may go a little higher to cut the roll resistance as I have more grip to play with in the first place.
I suspect that eveyone has their own approach to this one.
|I Go Low||triangleforge|
Sep 3, 2002 11:43 AM
|Good advice there, Eager; I tend toward the other end of the scale on tire pressures, trying to go as low as I can get away with...
In a race (typical 'cross course -- grass, pavement, some pinch-flatty curbs, lips or other transitions between the two), I'll run tubulars (Tufo Rhinos or Clement Grifos) at 35-40 psi, or clinchers (Ritchey Trail Mix 700x33, I think). If I think I can get away with it, I'll go as low as 30 with tubulars, and trust in the amazing powers of Tufo sealant. I'm about 165 lbs. and try to ride "light," with mixed success.
An experience about three weeks ago really reinforced my affection for low pressures. I was out at a local mountain bike park (Wakefield/Accotink, for those of you in the DC area) with a friend on his MTB. I had a slow leak in my rear tubular tire, which meant that I was down around 15-20 psi. after about 20-30 minutes of riding, at which point I'd stop and pump the thing back up. When the tire was at its lowest, it was simply astounding how much traction I got in the back -- stuff that normally gives me fits on a mountain bike found me dancing right up, with nary a care for wheel spin. Of course, I could feel the rim bottom out over every rock or root, but the tire (Tufo Rhino, with old, dried-out Tufo sealant -- hence the slow leak) held up just fine.
Of course, to go that low in a race wouldn't make much sense, as you'd pay too big a penalty on all the fast sections of the course, but for me, 30-40 psi in tubulars seems just about right.
|One more caveat --||triangleforge|
Sep 3, 2002 11:49 AM
|Also, if you're interested in exploring the low-pressure end of things with tubulars, be sure you've done the best job you can with the gluing of them. Pressures that low (especially if you're getting down into the high twenties, as claimed for the new Tufo Elite LPS & super-supple, super-expensive Dugast tires) carry an increased risk of rolling a tire. Take your time, do it right with multiple, thin layers of cemet over a couple of days, and check them frequently, and you'll be fine -- and riding your bike over some truly amazing stuff!|
Sep 3, 2002 11:51 AM
|I really ought to proof-read better...
When I'm on clinchers, I'll run 50-65 psi.
|Triangleforge, I live in Vienna/Reston area.||peter in NVA|
Sep 3, 2002 1:09 PM
|Any suggestions on good off-road rides for a cross bike. I've got a nice loop through Lake Fairfax but am looking for something new. My mtb is out on the west coast since I travel there a lot on business to my home office.|
Sep 3, 2002 1:28 PM
|First off, if you're close to Lake Fairfax, are you planning to race All Hallow's Cross, and the other race that Potomac Velo puts on there? If not, let me urge you strongly -- they put on a great race, on a really fun course.
Other fun spots for a cyclocross bike around here: I really like the Wakefield/Lake Accotink MTB trails -- nothing crazy technical like Gambrils or Snowshoe, West VA, but challenging enough for a few hours' fun. I'll also sometimes do training rides on the C & O Canal towpath (the gravel one), but you really want to go early in the morning, since it gets so crowded on the weekends. While not challenging riding, it's very pretty along there with lots of ducks, herons & other wildlife, and good scenic views when you get up around Great Falls.
Also, the 'cross-threaded types on my racing team (Squadra Coppi, the boys & girls in blue) have started up group cyclocross drills on Wednesday mornings before work (6:30 to around 7:30 or a bit later) near Seven Corners; drop me a note at triangleforge @ yahoo.com (of course, drop the spaces around the "@") for more info.
|Rode some practice laps around All Hallow's Cross last year.||peter in NVA|
Sep 3, 2002 3:21 PM
|Couldn't stay for the race but will try this year (guessing you were probably there- it was unusually warm).
Thanks for the info, in my ten years here I never rode the C&O, didn't know it would be fun on the cross.
|DC-Area 'crossing||Eric Marshall|
Sep 3, 2002 6:38 PM
|For an evening 'cross training series, Potomac Velo will soon be starting their Wakefield Park rides. Last year they were held on Wednesday nights, but I've heard we might switch them to Tuesdays. We'll post an announcement to the Mid-Atlantic Cyclo-cross mailing list when the details are ironed out. Sorry about the cross (no pun intended) advertising :-)|
|DC-Area 'crossing||Eric Marshall|
Sep 5, 2002 4:18 AM
|It looks like we're shooting for Tuesday, Oct 8th to start the rides. We'd like to start sooner, but as Wakefield is a multi-use park, there are too many conflicts with the already scheduled activities.|| |