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Old 09-26-03, 08:51 AM   #1
Portis
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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.
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Old 09-26-03, 09:10 AM   #2
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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.
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Old 09-26-03, 09:23 AM   #3
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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.
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Old 09-26-03, 11:11 AM   #4
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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?
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Old 09-26-03, 12:33 PM   #5
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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).
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