# Tire Pressure - BIG DUDE



## INACA (Dec 28, 2018)

I am new to the sport and I just recently purchased a 2018 Surly Krampus that came with Surly Dirt Wizard 29x3 tires. At the moment I am getting used to the bike and riding, finding my comfort zone on paved bike paths. Any recommendations on what a 6'2 340lb dude should be inflating plus tires to would be greatly appreciated.


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## ELECTRIC_YETI (Dec 6, 2013)

I am 6' 280 and I run my Chronicles at 17 +/- on the trails. If I am doing a bigger road ride, then I run 22+/-

Sent from my Pixel 2 XL using Tapatalk


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## amadkins (Jun 19, 2008)

At 280; I run 16 front and 18 rear with Chupacabras on 35 internal rims. No issues on Midwest single track with a fair bit of rocks and roots. I’d start at 18/20 for you on trails and work down from there. Probably a couple psi higher on pavement. 

Get a good gage too. I was surprised how much my pump gage deviated. Actual pressure was much lower.


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## Fuse6F (Jul 5, 2017)

Im 255 and ride aggressively (imo). Run 27.5” x 3.0” tires on 45mm internal w rims. The width makes a big difference in stability of the tire. Allows Running of lower pressures. I run 16 front and 18 rear for general trails. Tubeless. 

if you feel tractor tire bounce while pedalling. Then you need to add air. Lower till you feel it. Then back up 1 or 2 psi. Assuming your comfortable w rim widths. 

If your new to the sport then cool. Its fun. Fyi. If riding technical stuff. Take a small break before the harder parts. This makes them much easier to do, safer and more fun!


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## INACA (Dec 28, 2018)

ELECTRIC_YETI said:


> I am 6' 280 and I run my Chronicles at 17 +/- on the trails. If I am doing a bigger road ride, then I run 22+/-
> 
> Sent from my Pixel 2 XL using Tapatalk


Thanks for the info! I ran around 22 on the paved bike path yesterday and it felt great. My son took off on a trail that ran off the bike path, so I chased and slid all over the place. HA


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## INACA (Dec 28, 2018)

amadkins said:


> At 280; I run 16 front and 18 rear with Chupacabras on 35 internal rims. No issues on Midwest single track with a fair bit of rocks and roots. I'd start at 18/20 for you on trails and work down from there. Probably a couple psi higher on pavement.
> 
> Get a good gage too. I was surprised how much my pump gage deviated. Actual pressure was much lower.


That for the advice! I definitely need a good gauge. This is how green I am....I took my valve caps off and set my eyes on the strange little Presta valve.ha Luckily I had a dual valve pump.


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## big_stoke (Jun 5, 2018)

6'4 320 here with a 2018 krampus. I Running i45's with minon dhf/dhr 29x3 at 14 front 16 rear for rockyish St Louis singlerrack. Gravel/road rides anywhere from 25 front and rear.


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## Fuse6F (Jul 5, 2017)

Big-stoke. Any tractor tire bounce when spinning the flats at that low pressure


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## big_stoke (Jun 5, 2018)

Fuse6F said:


> Big-stoke. Any tractor tire bounce when spinning the flats at that low pressure


I've never heard that term. What's tractor tire bounce?


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## Fuse6F (Jul 5, 2017)

Run the flat section of trail. Eg down a gravel back alley and spin up a high cadence while seated. If you find your hardtail stats bouncing in the rear tire then add a bit of pressure. Till its gone or manageable. Same thing you see when a heavy implement is running down the highway. There is no way to balance those heavy implement tires so when they are in a hurry they bounce at travelling speeds. Imo tuning this our will increase the handling of your bike. Prevent flats etc


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## bingemtbr (Apr 1, 2004)

255lbs, my stats: 
-Specialized Fatboy, 4.0 FastTracks. On singletrack: F: 15psi, r: 11psi. On pavement: both at 18psi

-5" travel trail bike, 26'r, Maxxis Ardent Race, both 38psi. Any lower tire pressure results in side wall tears. I am sure this is due to the type of trails I ride (rocky, sharp limestone) and the type of tire. 

-road bike: 120psi.


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## Big_Mike (May 28, 2018)

6'6" started at 442, now down to 368 riding a 2018 Surly Krampus with the Dirt Wizard 29x3. Ride a mix of surfaces: paved roads, gravel walking / biking paths, sandy trails, dirt trails with some bumps and roots. I found that mid 20 psi has worked good as an all around pressure with going a little higher on the pavement and gravel and a little lower on the sand. Try to keep between having some bounce for cushion and not bottom out my rim.


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## big_stoke (Jun 5, 2018)

Fuse6F said:


> Run the flat section of trail. Eg down a gravel back alley and spin up a high cadence while seated. If you find your hardtail stats bouncing in the rear tire then add a bit of pressure. Till its gone or manageable. Same thing you see when a heavy implement is running down the highway. There is no way to balance those heavy implement tires so when they are in a hurry they bounce at travelling speeds. Imo tuning this our will increase the handling of your bike. Prevent flats etc


I've never noticed this. I'll look for it on my next ride.


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## Len Baird (Aug 1, 2017)

In a nutshell you want the lowest pressure you can get away with without pinching the tire and slamming the rims on stuff. I'd personally start at 25-30 at your weight but I guess I am old school.
It will depend on your style, what tires you use, so I'd say start conservative, and if all goes well lower the pressure little by little until you start to get rim strikes, then you have your limit.


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## metalskool (Feb 6, 2019)

Len Baird said:


> In a nutshell you want the lowest pressure you can get away with without pinching the tire and slamming the rims on stuff. I'd personally start at 25-30 at your weight but I guess I am old school.
> It will depend on your style, what tires you use, so I'd say start conservative, and if all goes well lower the pressure little by little until you start to get rim strikes, then you have your limit.


I agree with your ideas. I'm 6'-1" 250 lbs and I find when I get too low in pressure it just feels like I'm pedaling in deep sand. Isn't it that the more you weigh, the higher the pressure you need to have the same amount of tire contact with the ground and the same sidewall bulge as a lighter rider? I run around 18- 20 psi on a 29er 2.25 and that seems to be my sweet spot. (I get away with a few pounds lower on the front) Every time I try lower pressures it feels like I gain a lot of rolling resistance and gain minimal traction. The only traction difference I feel is on rooty damp sections and to me, is minimal. I guess it's where and how you ride as well?


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## jeffj (Jan 13, 2004)

Len Baird said:


> In a nutshell you want the lowest pressure you can get away with without pinching the tire and slamming the rims on stuff. I'd personally start at 25-30 at your weight but I guess I am old school.
> It will depend on your style, what tires you use, so I'd say start conservative, and if all goes well lower the pressure little by little until you start to get rim strikes, then you have your limit.


IMHO, that's way too much pressure in a 29 x 3 tire. Maybe 20 psi at most, and work down from there until you're too squishy, and then bump up a pound or two. Plus tires are VERY sensitive to pressure in some tires can make a world of difference.


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## JACKL (Sep 18, 2011)

jeffj said:


> IMHO, that's way too much pressure in a 29 x 3 tire. Maybe 20 psi at most, and work down from there until you're too squishy, and then bump up a pound or two. Plus tires are VERY sensitive to pressure in some tires can make a world of difference.


Well the OP weighs 340, so IMO 20 is a bit low as a starting point. Anyway I think that the hand-held pumps are often not accurate. I use the same pump, so regardless of the numbers, they should be consistent. I run just enough to avoid rim strikes.

I'm currently on 2.6s, but when running 3.0s I found that they were more bouncy at speed when running higher pressures, which is different than what Fuse6F experienced.

As far as lower pressures being draggy, going with a lighter / thinner carcass helps quite a bit with rolling resistance. In that case, you'll need to avoid strikes at all costs, and your terrain may not allow the lighter tire regardless.


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## Fuse6F (Jul 5, 2017)

FWIW. 3.0 purgatory is rated like 25 psi max. At those pressures i didnt like the tire as it would roll over a small obstacle and ping skip over it. Running as low as 16 up front would let it just absorb the obstacle. But in the rear lower than 18 at a high cadence in my hardtail gave a tractor tire bounce. So i felt that is an indication that tire will also move around alot when loaded on the trail. Im 260 and that was on i45mm rims.


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## CDSV900Rider98 (Jun 14, 2009)

Hmm, I always lose my air pressure gauges, so I must rely on my senses, knowing my bicycle, the surface and type of rides; I usually read the PSI rating on the sidewall of the tires, look at the tires while my bicycle is in freestanding mode, followed by touching and feeling the tire, then sitting on the bicycle while holding on to a bench, fence, pole or wall; I want the tires to have a little forgiveness from the forces while riding my trusty and reliable 1997 Cannondale Super V900: I just installed Rhinodillos Brown label in between my tube (?), Panaracer 26.0 x 2.10 FireXCPro Tires sitting on Sun RhynoLite rims.


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## metalskool (Feb 6, 2019)

CDSV900Rider98 said:


> Hmm, I always lose my air pressure gauges, so I must rely on my senses, knowing my bicycle, the surface and type of rides; I usually read the PSI rating on the sidewall of the tires, look at the tires while my bicycle is in freestanding mode, followed by touching and feeling the tire, then sitting on the bicycle while holding on to a bench, fence, pole or wall; I want the tires to have a little forgiveness from the forces while riding my trusty and reliable 1997 Cannondale Super V900: I just installed Rhinodillos Brown label in between my tube (?), Panaracer 26.0 x 2.10 FireXCPro Tires sitting on Sun RhynoLite rims.


I relied on my pump gauge both for my tires (floor stand) and my suspension (hand pump). I've recently bought a Topeak D2 presure gauge and found out that both were very off compared to the D2. The floor pump for my tires was somewhat close to being right- reading 18 on the pump but was actually 21psi by the D2. But my suspension pump dial gauge was off by nearly 80 psi too low. I was reading about 250 on the pump and 170 on the D2. I think if you are wanting to fine tune anything, (tires, suspension) you need a reliable pressure gauge.


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## Sasquatch1413 (Nov 6, 2008)

Been a while since I've run 29x3 tires but I think was 12 ish front, 18 rear at about 330 lbs. Dirt wizards are pretty beefy so you could run less than that. Its all about the feel you want. Run enough pressure that you don't get rock strikes on the rim. Also need more pressure the faster you ride for support in corners. Doing drops and jumps, might need even more. Get enough to eliminate rim strikes and experiment from there. Big tires with too much air suck, bouncy and harsh.


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