trial bike Posted July 10, 2016 Report Share Posted July 10, 2016 Someone has just commented that they see people with too much air pressure in their tyres. Is it possible to have too little pressure? I worry about damaged rims if I run too low. I weigh nearer to 70kg than 80kg, ride a 4RT and run about 4psi on the rear. Sometimes I struggle with grip and think I should try lower pressure. But then I run onto rocks and think that would be a bad idea. What is your opinion? Quote Link to comment Share on other sites More sharing options...
heffergm Posted July 10, 2016 Report Share Posted July 10, 2016 Your pressure is fine. Feel free to run 3 psi in the mud, but it's all technique. 1 Quote Link to comment Share on other sites More sharing options...
pschrauber Posted July 10, 2016 Report Share Posted July 10, 2016 (edited) I haven't tried out to ride with too little air pressure in doubt I use a tad more a puncture is something I really don't need as I' am very bad in working with tires take them off and on again... Nevertheless I believe it is possible to ride which less air in a tubeless tire then in a tube tire. There is less risk the rip of the valve. But there is to both type of tires the rust the tire will leave the rim bead more then it's harmless. Edited July 10, 2016 by pschrauber Quote Link to comment Share on other sites More sharing options...
metisse Posted July 10, 2016 Report Share Posted July 10, 2016 Can someone more informed than me tell me how much difference in terms of grip, with a modern tyre does differing amounts of air make. I always ride with slightly harder tyres as the trade off, a puncture and or grip always swings it. I would work on riding technique rather than whether 3psi is too little and 5 too much. 1 Quote Link to comment Share on other sites More sharing options...
metisse Posted July 10, 2016 Report Share Posted July 10, 2016 Can someone more informed than me tell me how much difference in terms of grip, with a modern tyre does differing amounts of air make. I always ride with slightly harder tyres as the trade off, a puncture and or grip always swings it. I would work on riding technique rather than whether 3psi is too little and 5 too much. Quote Link to comment Share on other sites More sharing options...
jonnyc21 Posted July 10, 2016 Report Share Posted July 10, 2016 Can someone more informed than me tell me how much difference in terms of grip, with a modern tyre does differing amounts of air make. I always ride with slightly harder tyres as the trade off, a puncture and or grip always swings it. I would work on riding technique rather than whether 3psi is too little and 5 too much. I have experienced a difference in grip depending on what type of tire pressure, tire brand, and what I am riding on. The Michelin tires I was riding on always seemed to grip better at the same pressure of the Dunlop 803's I am running right now so run them about 0.5 psi less to get a closer feel in grip. For example, when I am riding rocks on the Michelin's I would run 4 to 4.5 psi depending on if they had sharp edges or not and maybe 5 psi if very sharp, where on the Dunlop's I would run 3.5 to 4 and up to about 4.5 on the sharp stuff. Now in the dirt and mud with little to no rocks I would run 3.5 to 4 on the Michelins but down to 3 on the Dunlop's. One note: I am talking the older Dunlop's not the new GP's as I haven't had a chance to try a set of GP's yet. The GP's are the next pair I want to try when my current set where out. Also worth note is that I am 185 lbs and the tire experience is from both a 07 Montesa 4RT and a 08 Gas Gas TXT pro 125. Hope this helps. Quote Link to comment Share on other sites More sharing options...
crazybond700 Posted July 11, 2016 Report Share Posted July 11, 2016 Once I did 1 bar in the tyre in the garage, and forgot to let it off the first 2 sections I did not know what was happening to me. Around the correct pressure small adaptions will make difference, however less noticable and bad teqnique will rune it anyway. Quote Link to comment Share on other sites More sharing options...
smokey125 Posted July 11, 2016 Report Share Posted July 11, 2016 One thing to bear in mind with pressures is that different gauges can read quite differently. Experiment with different pressures until you get what feels best for you with your pressure gauge. 3 Quote Link to comment Share on other sites More sharing options...
zippy Posted July 11, 2016 Report Share Posted July 11, 2016 I run 4psi in the rear and 6psi in the front. I weigh (ahem quite a bit more than 200 lbs we will leave it at that) anyway I have ridden with a completely flat rear tire and it was only a little squirly I have ridden with a completely flat front tire and gained many points and crashes. hope this helps................but probably not 2 Quote Link to comment Share on other sites More sharing options...
axulsuv Posted July 12, 2016 Report Share Posted July 12, 2016 Well I just have to chime in here ...my trusty 240 pro became a different bike when in may 05 I changed the rock hard mich. Dated 10/92 for a fresh one, may have been the OE tire ... But even at 2.5 psi it had NO sidewall flex & about zero traction . A new old stock mich. and it was a different bike . And I can't explain the difference a new x-light made on my old section over the old OE tire ....... Quote Link to comment Share on other sites More sharing options...
smarty156 Posted July 12, 2016 Report Share Posted July 12, 2016 (edited) If it's too low the tread will close up when you ride over something and effectively become a slick (push your thumbs into the middle of the rear tyre when there's hardly any pressure in and you'll see what I mean). On slippery tree roots you'd really notice too low pressure. I tend to run around 4.5psi rear in the dry, 4 in the wet and maybe down to 3.5 if it's really muddy but no lower. Front I tend to run 4.5 to 5 in the dry and 4.5 in the wet. Lower in the wet and the front will tend to wash out on turns. Edited July 12, 2016 by smarty156 Quote Link to comment Share on other sites More sharing options...
dadof2 Posted July 15, 2016 Report Share Posted July 15, 2016 I find under pressure tyres make the bike feel unstable and squirmy and on most terrain going below a certain pressure does not increase grip, or at least the negative effects of instability outweigh any increase in grip. 2 Quote Link to comment Share on other sites More sharing options...
2sticks Posted August 17, 2016 Report Share Posted August 17, 2016 Hi, new to trials and was wondering how do you pump up your tyres. Getting as low as 4 psi do you have a low pressure pump? Quote Link to comment Share on other sites More sharing options...
heffergm Posted August 17, 2016 Report Share Posted August 17, 2016 Any hand/foot pump is fine. You need a low pressure gauge. 1 Quote Link to comment Share on other sites More sharing options...
feetupfun Posted August 17, 2016 Report Share Posted August 17, 2016 Hi, new to trials and was wondering how do you pump up your tyres. Getting as low as 4 psi do you have a low pressure pump? To get the pressure you want, you pump the tyre up above what you want (with whatever source of compressed air you have) and then let air out until it is down to the pressure you want. If you are a novice at setting trials tyre pressure, use a low pressure (trials) gauge to measure the pressure. Once you have done it enough times, the gauge becomes unnecessary because you will be able to judge when the pressure is right by the appearance of the tyre when you put your weight on the bike, or by pushing against the tread with your knee Be aware that the tyre pressure will change with the temperature of the tyre, and with change in altitude 1 Quote Link to comment Share on other sites More sharing options...
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