# Another f**king PSI post?!



## mark! (Jun 1, 2012)

6'1 and 320, riding a SC Tallboy with Flow EX's. Set up tubeless since forever. I've come down from 384 pounds this year and still going after some yoyo'ing weight wise. I noticed with my rear wheel set at 36 PSI, again tubeless the tire looks a little squishy and I usually have someone tailing me that says my tire looks flat. My question here is this...should I run a tube in that rear wheel and pump up the PSI until I get to my goal weight area (230ish)? I never feel loose on my rear tire, but when I look down I do notice that it rides a bit flat looking when I'm in the saddle.


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## uzurpator (Dec 8, 2005)

I'm 230lbs. I run 30psi front, 40psi back. If you are 50% more, I'd run 50% more pressure.

Pressure recommendations are made for people half your size.


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## cjsb (Mar 4, 2009)

I don't know the basis for psi for tubeless setups, but it used to be a rule of thumb is 30 psi Max. You have exceeded that with your setup with no issues. If you are going to add more psi, I'd do it conservatively, 1-2 psi at a time. 

If your tire can do 45-55 max psi with a tube, then you may give that a try, too. 

Sent from my moto x4 using Tapatalk


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## LyNx (Oct 26, 2004)

There's a formula that's been around for a good while that gives a good starting point, it goes like this 

Rider weight divided by 7, then take away 1 PSI for the front and add 1 PSI to the rear, then adjust from there. For you that would give you 47 PSI rear/45 PSI front, so I'd say yeah, add some more PSI. 

Personally even at my paltry 185-190lbs kitted to ride I still run 25 PSI rear/21 PSI front with 2.3" tyres on i29 rims on my FS. I do have a few heavier friends, still not near your weight, max was about 260lbs before he started loosing and he used to run about 35-40 PSI and the tyre looked like mine at 25 PSI.

All that being said, if you're not feeling squirm and/or rim strikes, then maybe the gauge you're using isn't accurate and you are in fact actually running more PSI than you think, so check that out, but if you ride aggressive, can't see how you could on those pressures.

Hope some of this helps.


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## jeremy3220 (Jul 5, 2017)

If it's not causing issues I wouldn't worry about how it looks. Your other options for added support would be tire inserts or heavier duty casings.


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## Forest Rider (Oct 29, 2018)

Do not exceed the max PSI listed on the sidewall, with a tube or tubeless.

As mentioned above, maybe a heavy casing is better suited for you. Maxxis double down maybe?


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## sturge (Feb 22, 2009)

Lots of variables...terrain, rider weight, tires, suspension, agressiveness, etc. I'm riding New England singletrack with 27.5 X 2.5 Maxxis DHF Exo's. I'm 220 and my happy spot is 22 psi rear / 20psi front. Not a lot of high speed flow trails here, lots of tight techy stuff so I like the added traction of a little lower psi. I tend to ride 'light' over the many rocks and obstacles compared to some of the guys I ride with who like 25psi or so and they are not as heavy as me. I'm on a Kona Process 153.


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## bingemtbr (Apr 1, 2004)

I'm 6', 250lbs, and have not been able to run tubeless on my rear tire(s) for more than 3 rides before having to install a tube. I either get a side wall tear or an un-plug-able puncture in the tread. I've tried Maxxis DHFs, Spec Ground Controls, Spec Fasttracks, and currently running Maxxis Ardents. All the tires I've tried supposedly had thicker side walls; but still no luck. 

Regarding airpressure, depending on the trail / trail conditions, I run 32-38psi. 

Glad to hear you're on a TB. I'm anticipating ordering a TB4 shortly.


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## jonas_24112 (May 16, 2016)

bingemtbr said:


> I'm 6', 250lbs, and have not been able to run tubeless on my rear tire(s) for more than 3 rides before having to install a tube. I either get a side wall tear or an un-plug-able puncture in the tread. I've tried Maxxis DHFs, Spec Ground Controls, Spec Fasttracks, and currently running Maxxis Ardents. All the tires I've tried supposedly had thicker side walls; but still no luck.
> 
> Regarding airpressure, depending on the trail / trail conditions, I run 32-38psi.
> 
> Glad to hear you're on a TB. I'm anticipating ordering a TB4 shortly.


Not sure if you know this, but Maxxis has 2 grades of casing for tires. EXO is the lighter casing, and Double Down is the heavier. If you have a particular Maxxis tire you like, check to see if it is available in the Double Down casing. I'm the same size as you and tore two Continental X-Kings before I switched to a Maxxis Aggressor Double Down and have had no issues with it so far. No rolling in curves etc and usually run 28-30 psi.


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## mark! (Jun 1, 2012)

I did a road ride today on my mtb and bumped the PSI up to 45 based on the "formula". It looked better but still had a wee little bit of bulged out look to it, not as bad as before though. I may still keep that pressure and try it on the trails and see how it goes before throwing a tube in there, and I convinced the wife I needed new tires so I may go with a heavier casing tire next to see if that changes anything. Right now I'm running a Specialized Renegade Control on the front and The Captain S Works on the rear. Definitely leaning towards trying some Maxxis double down Minions though after looking at them. Any idea if the double downs have the highest casing? Weight obviously isn't an issue since I'm shedding weight on my body and will likely never be one of those guys that's cutting weight off the bike to go faster.


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## LyNx (Oct 26, 2004)

If you're going over 40 PSI, unless you're running a 1.9" tyre, do not do that tubeless. If you look on the Stans site it clearly states tyre pressure for given size tyres on the different rims. Highly suggest you stop through a good bike shop and ask them if they have an accurate gauge and double check what they get against what you're getting. If you're still seeing a good bit of deformation/bulge at 45 PSI, then that tells you you were running too low before.



mark! said:


> I did a road ride today on my mtb and bumped the PSI up to 45 based on the "formula". It looked better but still had a wee little bit of bulged out look to it, not as bad as before though. I may still keep that pressure and try it on the trails and see how it goes before throwing a tube in there, and I convinced the wife I needed new tires so I may go with a heavier casing tire next to see if that changes anything. Right now I'm running a Specialized Renegade Control on the front and The Captain S Works on the rear. Definitely leaning towards trying some Maxxis double down Minions though after looking at them. Any idea if the double downs have the highest casing? Weight obviously isn't an issue since I'm shedding weight on my body and will likely never be one of those guys that's cutting weight off the bike to go faster.


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## jeremy3220 (Jul 5, 2017)

mark! said:


> I did a road ride today on my mtb and bumped the PSI up to 45 based on the "formula". It looked better but still had a wee little bit of bulged out look to it, not as bad as before though. I may still keep that pressure and try it on the trails and see how it goes before throwing a tube in there, and I convinced the wife I needed new tires so I may go with a heavier casing tire next to see if that changes anything. Right now I'm running a Specialized Renegade Control on the front and The Captain S Works on the rear. Definitely leaning towards trying some Maxxis double down Minions though after looking at them. Any idea if the double downs have the highest casing? Weight obviously isn't an issue since I'm shedding weight on my body and will likely never be one of those guys that's cutting weight off the bike to go faster.


The tire is going to bulge somewhat regardless (unless you're running 100 psi).

The heaviest duty casings are going to be DH casings. DH tires usually have softer rubber though that I wouldn't recommend for trail riding. You also don't have to get Minions. If you want a fast rolling rear tire you could go with a DD Ikon or Semi-slick (e13 also makes a good semi-slick in a heavy duty casing).


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## JACKL (Sep 18, 2011)

mark! said:


> I did a road ride today on my mtb and bumped the PSI up to 45 based on the "formula". ... I may still keep that pressure and try it on the trails and see how it goes before throwing a tube in there...


45 psi on a Flow EX tubeless? Hopefully the gauge is incorrect as Lynx mentioned. I just want to point out that if the bead blows off the rim while you are working on the bike or tire, it will blast you in the face and / or eyes with sealant. The rims have a max psi rating regardless of the tire. I think with the old flow ex it was 30 or 35psi. Can't remember for certain, but I'm pretty sure you have exceeded it.

Kudos on the weight loss, every pound gets you back toward a more "normal" range for your bike and components.


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## mark! (Jun 1, 2012)

Printed on the rim it says 38 PSI max for the 2.3 tire, that's why I was hesitant to go above that and went up in 2-3 PSI increments. Still learning and figuring things out, so thanks for the heads up. I knew the tire could blow off the bead during a ride etc. I'll back it down and check out some other tires. Thanks for everyone's help and input, greatly appreciated.


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## notso (Jan 22, 2015)

I agree with Jeremy above. If you're not getting rim strikes or feeling excess squirm, don't worry about how the tire looks.
For reference, I'm about 260 now (290 heaviest) and I run anywhere from 30-35 psi in the rear depending on bike/rim. I have a Flow EX on my hardtail and routinely run it at about 32 for trail riding up to about 35 for road/smooth gravel (with a 2.1 width tire).


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## Knight511 (Nov 26, 2010)

Stop looking at the tire for a bulge. If the tire looks the same round with you on and off the bike, the tire is too high!

Like others have said, there are MANY variables to this problem. I am 288 and I run Maxxis Exo Ardent 29x2.3 front and Exo Ikon 29x2.3 rear.... front pressure at 28psi and rear at 30psi.

It does not matter what teh tire looks like, it only matters what it rides like. If the tire is not squirmy and you are not dinging the rims, the pressure is fine.


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## Fuse6F (Jul 5, 2017)

Way to go on the weight loss. Keep it up.


If your not bending rims then carry on as normal. And yes your under pressured for your weight. 

Im 265 and run 18 psi on my rear tire for trail and 21 for street. Course its a 3.0” wide tire on an i38mm rim for more floatation and stability. This equipment is more suited to my weight! You may be at or past the limits for your equipment. 

A tube just gives you a slightly harder work out. Unless you need the sealant for cactus thorns. At our weights. Who cares. Just get out and ride.


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## LyNx (Oct 26, 2004)

I'll chime back in with one more thing, or more honestly just repeat what a few others have said...at your weight, you are a person who would benefit from the stiffer casing of the DD or even DH option from Maxxis, to you it would feel more like the EXO casing feels to lighter riders, well worth a shot if you ask me and then you can run lower pressures relative. For me at 185-190lbs those casing are super stiff, but for you, I bet they'd improve the ride, even though you say you can feel the tyre squirm, it must, which you might not feel as squirm, but maybe as inconsistent handling/steering.


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## Mr Pig (Jun 25, 2008)

Has your tyre exploded? Yes? Too high.

Is your rim touching the ground? Yes? Too low.

Aim for somewhere I between the two.


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## masonmoa (Jul 11, 2011)

Exactly what Knight said. Ride the tire as low as you can without it feeling squirmy and without rim strikes. Tires are supposed to bulge because the bulge helps with traction. I mean, that's the point of tubeless, right? I've ridden tubeless for years with my weight as high as 335 and as low as I am now at 280. My Maxxis DHRII's on my three bikes are all run somewhere between 30-35psi, and my fronts around 28psi. I've tried lower, but it gets squirmy and I hate that feeling.

As for other's comments for different casings, sure, the heavier casings would help, but I've never run them, even at 335lbs, and I've used WTB, Maxxis, Schwable and Continental with no issues, no torn sidewalls and no blowouts, even on really rocky trails. Like many things recommended to clydes, I have found from years of riding that the extra weight from heavier components can't hurt, but aren't always necessary.


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## jaggittens (Oct 25, 2007)

I am 6'6" 250 on a good day and am running 15PSI rear 12PSI front on 29+ with cushcore. I'd never ride without them now...

Something to consider.


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## mark! (Jun 1, 2012)

I found 2 Maxxis Minion DD versions at the LBS and put them on yesterday and aired up to 38 PSI, had to air down half way in to the ride. I'm enjoying these tires so far on the 10 miles I did on them yesterday. The bulge is less than before but after folks talking about it I'm not worried about it anymore. I had it in my mind that it should bulge, but as ya'll said as long as I'm not getting rim strikes or burping the tires, should be good. I do like the fact that I can air down a bit more with these tires than with the Specialized ones I was running before.


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## LyNx (Oct 26, 2004)

Excellent! :thumbsup: Enjoy the ride, continue to work on pressures on these new tyres. The Maxxis DD wil definitely feel loads better than the casing you had before, should be most especially noticeable when you're cornering hard through berms or plowing through really rough stuff at speed. Nice to find someone who listens to advice and doesn't get offended.



mark! said:


> I found 2 Maxxis Minion DD versions at the LBS and put them on yesterday and aired up to 38 PSI, had to air down half way in to the ride. I'm enjoying these tires so far on the 10 miles I did on them yesterday. The bulge is less than before but after folks talking about it I'm not worried about it anymore. I had it in my mind that it should bulge, but as ya'll said as long as I'm not getting rim strikes or burping the tires, should be good. I do like the fact that I can air down a bit more with these tires than with the Specialized ones I was running before.


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## Alias530 (Apr 1, 2013)

uzurpator said:


> I'm 230lbs. I run 30psi front, 40psi back. If you are 50% more, I'd run 50% more pressure.
> 
> Pressure recommendations are made for people half your size.


I'm also 230 and run 19 front, 26 rear on a 29x2.6 front and 29x2.3 rear on i30 rims. You can probably run a lot less.


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## Camstyn (May 15, 2018)

I'm 6'5 and 335lbs, down from 360, goal weight of 250. I mostly ride bike parks on my YT Tues but just picked up an e-bike for trail riding.

I find that with my 2.4 Onza Aquila's and cushcores installed on my DH bike I run about 30psi front and 34-35psi rear. Any less and I get a ton of tire squirm in the berms and pedal strikes. Any more and the forks get overwhelmed by chatter and I start to sacrifice traction.

I've only ridden the Decoy e-bike twice but I aired it up to similar PSI's with tubes installed and so far it seems ok. I might drop the front a couple of PSI's to get better front suspension performance but the rear seems good. I thought I would get tire squirm on the rear at this PSI with the 27x2.8 Maxxis 3C EXO casing, I was planning on upgrading it to a DD or DH casing with cushcore but so far it's not an issue. The rear rim has a 35mm ID so I guess that is making a big difference. The front rim on the Decoy is a 30mm ID with 2.5WT and the Tues has 30mm ID's front and rear.

That being said, it makes me wonder if I don't go to 35mm ID rims all around if I wouldn't be able to run a little lower PSI, or if I'm overthinking it and should leave well enough alone.


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