Birty Dastards Jeep Club

Tech Forum => Workshop => Topic started by: Mike2909 on June 22, 2014, 05:33:45 PM

Title: Reducing Tyre Pressure
Post by: Mike2909 on June 22, 2014, 05:33:45 PM
I am using the 35x10.5x16 tyres off road. I have standard 30psi in them. To what pressure can I drop without the danger of a tyre coming off the rim?
I have struggled  a couple of times on rocky surfaces with the mud tyres and want to try a lower pressure. I dropped them down to 25psi but that did not seem to make that much difference.
Title: Re: Reducing Tyre Pressure
Post by: wildwood on June 22, 2014, 05:45:35 PM
Used to drop mine to 12 front and 8 at back.any lower at the front and you'll lose a bead on a hard turn. That was with 8.5" rims. Wider rims and more danger of losing bead.
Title: Re: Reducing Tyre Pressure
Post by: georgen on June 22, 2014, 05:48:07 PM
30 psi seems a little high, I run 28 all round on the tj on and off road with my 33/12.5/15 muds. My tyres are C rated and at 28 can see them bellying out at the bottom so flexing as Muds seem quite Hard as in carcase stiff. Off road I think you should be safe down to 20 psi, I dont know what you do off road but at 20 psi would very much doubt you would pop a tyre off on anything but of coarse there's always one exception.
Title: Re: Reducing Tyre Pressure
Post by: JamesH on June 22, 2014, 06:15:03 PM
Mine are bias ply so 8-10 psi off-road works well, even at 1psi they don't go completely flat. My previous tyres I used to use 28psi on road and about 15 offroad, never popped a tyre off the rim except when I ripped a valve out so it was 0psi at the time!
Title: Re: Reducing Tyre Pressure
Post by: Mike2909 on June 22, 2014, 06:23:31 PM
Thanks for the input  :13: I will try at 15 next time I am out. 
Title: Re: Reducing Tyre Pressure
Post by: Dtimot8 on June 22, 2014, 07:11:26 PM
Hmm looking of exactly that tyre size
are they the simmex or "nearly" simmexs
details would be grans
ta ever so
Title: Re: Reducing Tyre Pressure
Post by: IrishCJ6 on June 22, 2014, 07:30:45 PM
I run my MT Baja Claws (33x12.5) at 10 psi and habe never had an issue, much better grip especially on rocks.
Title: Re: Reducing Tyre Pressure
Post by: isle of man on June 22, 2014, 07:37:14 PM
Yep. try 10 and work up from that.
Title: Re: Reducing Tyre Pressure
Post by: Mike2909 on June 22, 2014, 08:13:01 PM
Hmm looking of exactly that tyre size
are they the simmex or "nearly" simmexs
details would be grans
ta ever so

Silverstone Extreme M/T your highness.
Title: Re: Reducing Tyre Pressure
Post by: Mike2909 on June 22, 2014, 08:14:13 PM
Yep. try 10 and work up from that.

Hint of sarcasm in your words methinks, tis better to work doon than up
Title: Re: Reducing Tyre Pressure
Post by: Ezz on June 23, 2014, 12:08:17 AM
I always drop my Simex's to 8-10 psi
Title: Re: Reducing Tyre Pressure
Post by: gazjeep on June 23, 2014, 07:10:57 AM
Running BFG 31's on standard Sahara rims.

30 on the road no problem. a couple of years back reduced to 12 off roading, great to get you out & accross ruts but did have a tyre off the rim at that pressure, I personnaly wouldnt go below 20 on our set up but it depends on what combination of tyre & rim you got I supppose.
Title: Re: Reducing Tyre Pressure
Post by: Dtimot8 on June 23, 2014, 05:53:17 PM
Hmm looking of exactly that tyre size
are they the simmex or "nearly" simmexs
details would be grans
ta ever so

Silverstone Extreme M/T your highness.

Thank you
could i be a PITA and ask two favours
could you measure the actual height of the tyre
and a picture of the flex of the sidewall at 30psi and what you decide to run them at
On my 255/85/16 - 33 inches at 32 psi lose an inch and half at 20
but they do a good job of wrapping round rocks at that pressure
Title: Re: Reducing Tyre Pressure
Post by: JamesH on June 23, 2014, 06:06:27 PM
Tim, I was thinking about your want for tall and narrow tyres (or at least not too wide) and remembered that TSL do Swampers in 34x9.5 16" and LTB in 34x10.50 16" plus Boggers in 35x10.50 for 15" and 38.5x11 for 15" & 16". Not exactly good on the road I'd guess, probably Simex behaviour or worse  :icon_eek:
Title: Re: Reducing Tyre Pressure
Post by: isle of man on June 23, 2014, 07:12:14 PM

On my 255/85/16 - 33 inches at 32 psi lose an inch and half at 20
but they do a good job of wrapping round rocks at that pressure


I have this size on the 75 in KM's, do you per-chance need 6 more? 2 are as new the other 4 have done 6k road use? I would take £600gbp for the 6  :icon_eek: