I always ran sidewall max - 5 psi until my friend steered me to the calculator on SRAM's web site. There's so much data you enter into it first, I run the calc for both wet and dry, average the two and round to the nearest whole number. There's always about a 2 psi difference between front and rear, at least with my inputs. The difference was night and day to how hard I was running my tires before and I love it! I've fiddled around a bit on my own but always come back to their recommendation, it just works so well. Also, as I've lost about 70 lbs from mountain biking, I've recalculated every 5 lbs along the way and it's been gratifying to see my pressures drop while maintaining that same riding feel.
i didn't know there was a calculator, according to it im like 10 psi under, im gonna try it and see how it feels because ive felt its been too mushy. the website was very usefull
In addition to the rear wheel taking more of the brunt of the trail, the rear wheel has more weight on it. The weight bias is something like 55/45 or even 60/40 depending on the bike. You should always run a couple of PSI more in the rear for proper support. It's no different than sag on a full suspension bike. You do not want to run a large delta of sag between the fork and the shock. The key to bike setup is balance front to rear, this helps with load transfer and overall stability. (Assuming a rider utilizes proper body position)
Tyre pressure is part of a system, including suspension setup and the wheels. Softer suspension or more compliant rims/less spokes/lower spoke tension can also inprove grip, without the risk of pinch flats or smashing a rim. I personally prefer slightly firmer tyres and try to maximize grip with wheel setup. Also keep in mind a heavier casing like DD or DH on Maxxis tyres can also allow a lower pressure without risking punctures or feeling wallowy.
I'm 160 kitted up on a 35 lb Stumpy Evo with 2.5 EXO+ Assegai/ DHRii with Cushcore inserts riding my limits on gnarly trails at Rocky Peak in Simi Valley. I ran 20/20 psi yesterday and it felt great.. plenty of grip and no issue otherwise. Last time I rode 24/25 psi and felt squirly and slidey on the rocks and loose stuff. 20/20 is my happy place.
I’ve been playing around with different tire pressures for XC riding after converting my rims to tubeless, I thought harder tires like 30 psi would result in fast rolling speeds and less pedaling, which is slightly true but doesn’t make enough of a difference. I’ve found a lower pressure as low as 20psi is so much better for grip and you still have plenty of rolling speed.
Running the Assegai/Dissector combo(2.5/2.4 exo+), tubeless, no inserts... running 28psi front and rear on 27.5" x 30mm rims with approx 100kg rider weight.
Me and my mate spent a whole day playing with tyre pressures at aston hill once, letting out 1 psi out every run. We could feel the grip getting better and better, until on one run I could feel the rear rolling off and wallowing around, which was horrible. It felt like the wheel was loose. 1 psi more, and sorted.
I'm glad you used those techy terms like "smooshy". Now I know what your talking about.......I run 2.6 Vittoria eAgarro tires and they are both 27.5". I run 18 PSI Front and 20 PSI Rear....my eBike weighs 54lbs. This pressure seems to be the best balance of Traction and Handling.
Pressure have a huge impact on how the bike feels…for sure. I’m running a trailhardtail with 2.4 Onza Porcupine trail tires, cushcore trail in the rear only. In such conditions like in Finale, my go to pressure is 21psi front and around 24-26psi in the rear. On my much smother home trails i prefer 21psi on both…
I usually ride19-20psi front and rear on my maxxis minions here in Colorado. Feels like it works well for me. I'm on a trail almost Enduro. A trailduro if you will.
PSI on a hardtail? At 190 lbs (86kg) I run low psi on 2.6 Exo Maxxis with Rimpact inserts. Because the only rear suspension you get on the rear is the tire, I play around with the psi. I typically run 19psi. During the long pre-fun climbs, I test the "dampening" of the rear by rolling over sharp rocks or roots at slow speed. If it bounces too much, I go down to 19, if it feels like there was very little rebound, I go up to 21. You'll find that these small changes are very noticeable. I love the Topeak digital gauge. PS. Great video!
Good comparison for mostly downhill rides, but what if you prioritize climbing? My usual rides are a balance of both, and I find on most terrain, riding with a bit less tire pressure in the rear helps considerably with traction.
Mi combo for my XC bike is Maxxis Ardent 2.25(front), Ardent Race 2.20(rear) at 30 psi both. I would like to run them at 25 but since I ride my bike in the streets a lot, and they're not tubeless, 30 is best for me.
A few points: a low pressure tyre flexes and sheds clogged mud easier. It makes a hardtail comfy. It makes riding wet limestone possible! You run high pressure at the back to get same compliance because that’s carrying 60% of you mass (you CoG is at the BB ie nearer the rear contact patch)
I couldn't believe the difference going from 30/32psi to 24/26psi made on my hardtail at the downhill lifts. It was like I felt like I had rear suspension in comparison.
I've always ridden at 3BAR/45PSI, until I met a guy and we exchanged bikes for a trail, and he commented on how awful mine felt; he laughed at my pressures and we reduced them to 2BAR/30PSI, and ooooh boy how much better it feels now! I was already feeling good on my bike despite the high pressure, but now I can't go back! I won't go lower because I ride lots of flat compact roads and I don't want too much drag, but it was one of those variables I never questioned!
The drag or what you're referring to is the coefficient of friction is not highly effective by tire pressure, it's a false premise. And it's mostly inaccurate because of the significant surface changes and hysteresis losses. This goes for any surface. The more your tires stay in contact with the surface the more efficient the energy output is. The more you bounce results in inefficient and more power loss. Proven fact. Physics. 🙄
@@rider65 definitely not; the more a tyre deforms, the more energy gets dissipated in that action, which you don't get back. If you ever get a puncture, you notice right away that the rolling resistance increases noticeably. Physics 🙄
Well, the way to look at it, is tire pressure controls a few things - the contact patch, and side wall stiffness (which you covered). Obviously the softer the side wall, the more sloppy turning characteristics. However, think about the parameters at play with pressure, esp side wall stiffness - regardless of the type of bike (full rigid, hard tail, full suspension) it is the first and most direct contact point of ones suspension (yes, even full rigid bikes actually do have a really tiny amount of suspension).
Sidewall suppleness is more down to materials and construction rather than pressure. Pressure will affect overall compression of the carcass and the sidewall but has nothing to do with sidewall stiffness
I'm riding a full sus and I went out one day with 27psi in my rear tire and 25psi in the front. I'm running an Assegi in front and a Minion DH in the rear, both 27.5" on Spank rims. It was brutal. I skipped on the super lose rocky sections and lost a bit of traction on the roots and really steep stuff. So I went back out and had 25psi in the back and 23psi in front and that was perfect. I had absolutely beautiful traction in all terrains and it was quiet, I could feel everything and had lots of control. It was wild that barely 2 psi could completely change the ride like that. So yeah, it's really worth finding your sweet spot in my opinion. I'm anal about my tire pressures now. Oh, and I ride tubeless but so far no flats even though I'm riding some really horrible rock.
Riding on snow this is so important. I'm still getting a feel for some conditions. I run 4.8" tires on 26 x 105 rims on my bike and go down to around 3-5 psi depending on the snow (@ 165lbs). I may run up to 8-10 psi on hardpack trails but for climbing and descending in loose dry snow it is as low as possible without rolling a rim. Interesting the obvious low pressure cutoff that he felt is what you want in loose snow. Its not just faster rolling but overall control, if you have too high pressure then everything gets squirrelly and takes more effort, 1/2 psi less and you're good.
I’m on a Transition Repeater (53.5 lbs bike), I run Maxxis Assegai DH tires with Tubolite inserts and I’m 185 lbs. I run 24 psi in the rear and 21 psi in the front. I’ll up it 1-2 psi each if it’s a really fast rocky run.
since riding 26' HT's off-road from the late eighties I found running 55/60 psi F/R is an ideal balance but I enjoy a 'loose feel' to the qualities said pressures give... can't imagine running pressures under 50 psi
I ran lower pressures back then 32psi front and 40 rear, but there was the threat of flatting. Of course I weighed 135-40lbs race weight and ran 1.9 tires most of the time. Definitely a different approach, crazy how it changed. I now run 29 x 3" at 18 front 20 back, so much better and not slower even on the flat smooth trails. You just rode with the tire feel that the higher pressure gave you, we rode different then I believe.
I run really high pressures too. I mostly ride urban freeride and DH trails. 50 front 80 rear on maxxis minions. In the 10 years or so I have been running these pressures I can honestly count on ONE hand how many punctures I have sustained.
Tubeless 29" full suspension Commencal = 24psi front magic mary & back hans dampf. Our rides are combination of gravel mountain logging roads and single track, dry or muddy, depending on Oregon weather. My buddies says that's too hard or that look/feels great or that's too soft.😂 Rear needs to dig into the muddy uphills, so I don't mind if it's a little less. Don't want the front tire too hard, but it needs to take the hits and not fold when screaming downhill switchbacks. I am 200lbs and shock pressure is important as well. I don't fly and I do love the climbs (hate slipping tires) and the downhills are luxurious. My everyday hardtail running around our city streets, over curbs, and across park lawns runs at 35psi. Sometimes I ride my FS to work (locked in my office) and I don't mess with the psi, but it really should be higher psi if I ride it everyday on the streets. P.S. CF Neuron 29" in Thailand is the same. Lots of rain and mud, much is cross country - more highway riding because I don't drive Thailand!!!!
I go off my rim getting dinged…. I start higher and take away until I get a run hit then go up a little bit. I am at 33 front 37 rear. I am also 240 with a 40 pound bike and ride very hard and fast. I have the DH34 front and rear. I had 32 in the front and blew up the carbon rim so now I run 33 same trail and haven’t had a problem since.
Recently upgraded from a 2014 bronson 27.5 to a new 21 stumpy evo pro 29. My happy place in the bronson was 19 and 21 psi. Ran that in the stumpy, and it was slidy and chattery. Dropped it down to 16 and 19 and now it feels great. Haven't dinged it in the rock gardens. It's so weird because the specialized tires say 25 psi minimum. That said. I'm going to do a few runs today at different pressures, starting with the sram calculated pressures at 23 and 25. We'll see if more is better
My philosophy is, the right tire pressure equals the best compromise between traction, breaking forces, efficiency, and safety. Run too low of a pressure, risk role off, damaged rims, and less safe ride. Also much lower efficiency, the lower the pressure, the more work it takes to ride the bike. The higher the pressure, the harder it is to control speed. Think of a solid train wheel, less of the tire is on the surface, limiting the breaking ability (and thus the safety). Also, too high of the pressure can damage the rims as well, had a rim crack in half due to repetitive stresses on my road bike (which can withstand over 120LB as rated) on a ride resulting in an sudden stop of the wheel and hard crash. Finding the right pressure takes time, but we’ll worth the effort, if anything run slightly higher to compensate for the bread down. 1-2PSI is all it takes.
I know how my experimentation went on exactly that last rockgarden of the video... destroyed rim despite cushcore... i'll never run pressures below 1.8 bar in the back tire again. I'm 80 kg
Carbon wheels, no inserts. Maxxis tires, Exo+ front, DD rear. Both 2.5”. 21psi. Gaps, rocks, roots, hucks into rock gardens, only single track and it works great for me
literally the only contact you have with the terrain. Steering geometry, seat tube angle, fork offset, braking forces, acceleration, etc…etc…etc… all depend on proper tire pressure for optimal performance. yet there are people who freak out about a half a degree seat tube or head tube angle, but they’re running five psi more than they should be…
Nice review once again, thanks Rich. How much does body weight effect this? I’m a lighter rider (163cm & 65kg -68kg depending on hydration pack etc) I’m running Butcher GRID trail casing tires front and rear 17psi 19psi and it feels great on the loose rocky terrain over here in the Middle East, it even make the bike feel quieter. Q: How much do you weigh? Is my pressure too low? Ps I do run harder tires if risk of hitting square edges or fast deep G outs
I stupidly pumped my tires way up before doing a speed test on my ebike...well...guess i gotta go straigten my wheels now...something I never have to do when I run "just right" tire pressure. I am only 120lbs, i like soft tire pressure. Essentially, as soft as possible without smashing rim off the trail when bottoming out. Usually 20ish psi for me.
As an amateur biker I really didn't think I'd notice much difference when changing tire pressures. Wow did I ever! I can now tell if a tire is 1 psi low or high now. Lol
I run a different pressure almost every week or so. 28psi to 36psi (now it's winter here), all my bikes are tubeless I play often with tire pressure on the spot. I don't think there's a golden rule or formula, it's about feel.
Well few days ago I bought new tire pump, it’s Topeak JosBlow Mountain Ex. It has big 3,5” pressure gauge which goes up to 60psi only and it has thick barrel which has 50% more volume than majority of the floor pumps. I just lome my new pump! As perverse as it sounds. 😂
What pressure would you recommend for front maxxis assegai 29 / 2.5 maxxgrip DH casing that's on a trail/all mountain bike? it's mostly pebbles, fist sized rocks, cliffs, loose sand. In the rear i have minion dhr 29 / 2.4 dual exo. currently i run assegai at 23 psi and dhr at 26 psi and i weigh 100 kgs. I don't do jumps or drops, only riding.
I don’t ride these very well manicured type of trails. My tyres need to cope with bushveld rock, pendorings, the odd ystervark pin and the like. So, for me that means 2,5 bar at the back and 2 bar up front. Providing I have really good quality tyres that can take the punishment. In my case, that means Continental Cross King Two’s.
Heavy rider here (about 132kg on a 160mm Enduro). Running a DHR2 DD on the Front (2.0 bar) an a Dissector DH at the back (2.4 bar). Both wheels with a Tannus Armour tubeless. Rims are good so far this season, doing 8m jumps und enduro lines without any puncture or other problems 🎉
I run around 30 psi In my rear tire for xc bc I have dented and had to replace the rim several times even with cushcore so idk what to do bc I am out several 100
This is great in theory. But if you like to ride technical stuff fast and don’t have a wheel sponsor or inserts, I recommend 30psi+ front and 40+ in the rear.
@Chops00 ya you're probably right. But I'm 220lbs and ride a hardtail. I could see it blowing out on a sharp rock. I run 20 front and 22 rear when riding downhill stuff.
@Channel-io1di The stuff I’m talking about riding you wouldn’t want to be on a hardtail for. I tried running 35psi in the rear and got dents two rides in a row. I weigh 170#.
The same applies for climbing, a lower pressure will help with grip at the addition of rolling resistance. The aim is to find a happy medium. You could try a slightly higher PSI if you are climbing more but your bike may feel a little skittish when descending! Suspension lock out would be the best option if you're looking for maximum climbing efficiency without the sacrifice for going back down the hill! 🔒
#AskGMBNtech Hi guys I have hardtail Liv Tempt from Giant bikes the rear axle keep breaking could have to do with tyre pressure, my weight I'm over 90kgs I use the bike mostly for commuting to work and some simple group rides no extreme offroading I have changed the axles more frequent and it's denting my wallet. It has a block 7speed freewheel by changing the hub to that of a cassette 9 or 10 speed solve this issue
I see what you did there 👀 In the UK we spell it 'Tyre' it's the same in a few places but there are other places in the world who spell it 'Tire' like the US for example! 🤘
🤣🙄🤦♂️ a lack of the basics of physics...😂 I suggest Jan Heine articles regarding Tire construction Tire width compound and tire pressures. By running stiff tires and a soft suspension, you're not accomplishing anything that would be accomplished by the right tire pressures. The first initial and continuous contact and absorption of vibrations in oscillations is your tires. Those vibrations and oscillations ie energy then get transferred through the wheel through the suspension and frame and through your body. The correct tire pressure also optimizes braking effectiveness.
Tires should not feel hard and you are probably at 50+ psi if they are. Might as well get rid the tires air altogether and just ride rubber to rim lol. Id break my teeth lol
