# Tyre pressures



## lotusdriver (Sep 15, 2013)

l am 145lbs which is around 65kgs

My new FS Ebike has 27.5 x 2.8 tyres

Can someone give me a ball park figure for tyre pressures that l can start at?

l've never had 2.8" tyres before, currently they are at 30psi (which is how the bike was delivered) but feel rock hard and seem to bounce off rocks.


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## schilled64 (Apr 4, 2021)

I would start at an arbitrary slightly too high pressure, say 20psi, test. Then drop 2 or 3 psi, enough you should be able to notice a difference and test. Continue until ride, control, or wheel safety is in danger and go back up to previous pressure. Then go up and down from there in 1 psi increments to find your #. If that sounds too fussy, it's only because a 1psi difference in that size tire at the pressure it does well off road at, it makes a rather large difference. For one example, I ride an ebike with 2.8's, am about 50 pounds more, and usually run 18 rear, 16 front. They don't squirm or roll at all on pretty wide rims, but I do not have sharp edged rocks to worry about (but if I did, I would not run more pressure unless I was definitely getting rim damage). I also ride a dirt bike, so an extra 200 pounds and much more speed and bigger impacts on about a 4 inch rear and 3 in. front at about 10-12 psi both. But those tires are heavier and thicker.


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## reamer41 (Mar 26, 2007)

It depends how aggressively you ride. My wife is about 155 lbs, and she likes 8psi rear and 7 front. I have test ridden the bike a fair about with these pressures, and some light trail riding - I weigh 220. It is not enough pressure for me, but rideable. I could easily foresee you riding in the low teens, or if you’re an aggressive rider, in the mid to upper teens. 
This is on a 48 pound ebike, by the way, 27.5 x 2.8 Rekons, tubeless.


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## careyj1 (May 12, 2017)

I weigh 185 to 190. 17F/18R if loose and dry. 22F/24R is hero dirt. 29F with 2.6 tire and 27.5R with 2.6 tire.


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## lotusdriver (Sep 15, 2013)

Wow 8psi !!

l am currently at 25psi front and rear, down from 30psi and it's already a fair bit better to ride.

l will reduce it to 20psi and see how that goes, then l will try 15psi

l've never had 2.8" tyres before, my regular bike has 2.4" tyres and l run those at 25-30psi, l tried 20psi but kept getting snakebite punctures.

This is an ebike by the way, so weighs around 23kg


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## reamer41 (Mar 26, 2007)

lotusdriver said:


> Wow 8psi !!
> 
> l am currently at 25psi front and rear, down from 30psi and it's already a fair bit better to ride.
> 
> ...


Those really low pressures I mentioned above is with the tires set up tubeless, it you're running tubes you may need a little more pressure to prevent pinch flats.

Also, she is not an aggressive rider.


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## natrat (Mar 20, 2008)

lotusdriver said:


> l am 145lbs which is around 65kgs
> 
> My new FS Ebike has 27.5 x 2.8 tyres
> 
> ...


29x2.8 front 17 psi/ 29x2.6r 18psi 180 lbs rider
i won't go any lower because i once had a front blowout at speed in the wet and it was scary


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## lotusdriver (Sep 15, 2013)

Yes l have tubes.

I will try 20psi but won't go any lower. lt's already a lot better at 24psi F/R

l thought these larger tyres would be harder work on the road but in fact they seem to roll better?


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## UPSed (Dec 26, 2010)

I was running my plus tires at 15psi front and 17psi rear. I'm 195 pounds and ride rather aggressively. With plus tires, 1psi makes a difference.


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## natrat (Mar 20, 2008)

lotusdriver said:


> Wow 8psi !!
> 
> l am currently at 25psi front and rear, down from 30psi and it's already a fair bit better to ride.
> 
> ...


careful with tubes and lower pressure, with lower pressure the tire can move on the rim and cause the valve on the tube to rip out


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## TNC (Jan 21, 2004)

lotusdriver said:


> Yes l have tubes.
> 
> I will try 20psi but won't go any lower. lt's already a lot better at 24psi F/R
> 
> l thought these larger tyres would be harder work on the road but in fact they seem to roll better?


Wasn't there a fairly comprehensive test...and maybe more than one...that showed these bigger, fatter tires on MTB's for off road work aren't the big rolling resistance negative that most of us assumed would be the case? I don't have access to it now and am not trying to make an argumentative point about it, but I believe that it was a surprising result that most didn't expect. That said, on an ebike it's probably not much of an issue anyway.


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