Mountain Biking - PSI.....Paths & Pavement

I have read a lot of recommendations that say to run your mountain bike tires at around 30-40 lbs. For where I ride this is just too soft. I ride on pavement and on a bike trail or two made of smooth gravel.

So I cranked my PSI up to 60 this morning. I will ride it later today. What will I notice besides a rougher ride? Will I be more or less flat prone?

Also is it common for MTB tubes to lose a little air over time? I have ridden about 150 miles in the last couple of weeks and both of my tires got soft and spongey over that duration.

Providing your tyres can take the extra pressure, you should be fine and get less flats - I've run 1.75 semi-slicks at 80 psi on road and hardpack, and it's a bit hard on the teeth over rougher bits but apart from that fine ;)

As to losing pressure - all tubes slowly lose pressure, I've found schrader valves lose pressure more quickly than presta.

YOu've done the right thing putting the pressures up.

The 30-40 psi recommendation is for 'mountain biking' i.e. singltrack, tree roots, rocks etc. You should adjust to higher pressures for hardpack. Most MTB tires these days will take 65-85 psi.

If you continue to only ride on these sorts of hardpack trails and roads, you might want to consider changing out your tires for a set of semi-slicks.

And ditto to Richard D - all tubes are porous and will lose air over time. The higher the pressure and/or smaller the air volume, the more noticable this will be. I check MTB tire pressures about once every week or two. I check road bike tire pressures before every ride.

I know the front must have a small leak. I went from 65 to 45 lbs after my ride. I have thorn tubes in both tires. Question: Is it a bad idea to put some slime in a thorn tube? Is it bad to have slime in one tube and not the other? (weight?)

I know everybody cusses X-mart tubes but the LBS thorn proof tubes I presently have, have already produced a leaker in the first 2 weeks. As easy as it is to change a tube why not save the bucks and buy a less expensive slime filled tube from X-Mart?

Also, I spent a good number of years patching tubes and radial tires in a service station. I know if I had the buffer/scraper/rubber cleaner/patches, that I had their I could patch any tube. I just don't know about these patches that are made for bike tubes. Is patching worth mucking with or should I just keep new tubes around?

Ranger

By all means, buy the x-mart tubes. You'll probably justify your reasoning if you do this, because every time you have to replace a tube you'll be glad that you're paying less for each tube. But... you'll replace tubes far more often this way. I can speak from experience here - a friend I ride with used to insist on buying the x-mart standard and slime filled tubes. He easily had replaced ten tubes to my one through stem failures etc, and I don't recall the slime ever actually sealing a thorn puncture.

It sounds like you've had some bad luck with the thornproof tube you've installed, or you've installed it badly. I have used thornproof tubes in the past, and only ever replaced one. This was from a very sharp rock that managed to slice a 1/2 inch cut into the sidewall of the tire and stright through the tube. Never had a puncture in one. These days I mostly use standard, good quality tubes. This year I've had two punctures, both from thorns (and this is riding around in Colorado!). I have patched that tube (both times same tube) and am still using it now (I ride a road bike about 100 or so miles per week, and XC mountain bike about 20-50 miles per weekend).

IMHO, slime in a thornproof tube is overkill. I've never had a punctire from a thorn in a thornproof tube. Find the source of your leak before jumping to conclusions - it could be that the valve needs adjustment.

Patch as much as you like. My general rule is 3 patches per tube, then it gets relegated to the emergency bucket. I carry adhesive patches for use on the trail/road, and have glue patches at home. You can also use pieces of cut-up inner tube for patching, or buy the tube patch kits for automotive use (much the same as the bike patch kits, and far cheaper).