Split rim <span class="highlight">tyre</span> <span class="highlight">pressures</span>

Submitted: Saturday, Nov 25, 2006 at 13:48

ThreadID: 39760 Views:7929 Replies:7 FollowUps:8

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Member - Chris R (NSW)

Just taken the troopy on its first sand run to experiment with tyre pressures and handling. (Standard tyres, on split rims)
Fully laden troopy has 70psi rear 50psi front for sealed road. Don't know what it should be for bush.

Noted that at these pressures it needs to be scrambled up rough steps - otherwise it will lose traction and momentum.
Noted that it felt very susceptible to getting stuck in dry river sand on 20 degree morning.

Reduced tyre pressure to 18psi all round for sand. This got me going - but not comfortable traversing across minor slope. The vehicle wanted to wander down the hill. A low speed it seemed to wallow far more than I was used to in the Prado (which also used skinny tyres - BFG AT). Higher speed felt just 'OK'.

Previously the ARB air pump inflated to 35 psi. With troopy it needed to inflate to 70psi ! At 8psi per minute, that's 5+ minutes per rear tyre.

So what pressures do the seasoned drivers recommend for sand/bush where there may be several inflations in a day's drive?

Oh.. also experiment was interrupted - when inflating the final tyre the air hose separated from the pump. No spares for repair. But fortunately it blew at 35psi.

This is all part of proving the car before adventures in January onwards.

(Shoalhaven near Nerriga NSW barely moving)

Best regards
Chris

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Reply By: Willem - Saturday, Nov 25, 2006 at 14:11

Saturday, Nov 25, 2006 at 14:11

Chris

70psi!!! Cheeeezus mate, what are you carrying in the truck? When running my splits with radials I pump them 35psi. Gives a comfortable ride. On a hot day they will go up to just under 40psi.

When running crossplies on splits I would run at 40psi on bitumen and 30psi on dirt and 15psi in the deserts.

18psi on sand is OK. I went down to 10psi once(radial 7.50x16) on very soft sand south of Robe on the beach and run a front tyre off the rim. 15-20psi for beach or desert travel seems OK.

Cheers

AnswerID: 206838

Follow Up By: Member - Chris R (NSW) - Saturday, Nov 25, 2006 at 14:19

Saturday, Nov 25, 2006 at 14:19

Thanks Willem
I too was amazed at the handbook figures (actually 69psi rear). What's more, troopy came new from the dealer with 70+psi all round.

So back to Prado practices?

Cheers

Chris

FollowupID: 466815

Follow Up By: Hairy - Saturday, Nov 25, 2006 at 14:24

Saturday, Nov 25, 2006 at 14:24

Yeh I agree!
I used to run my splits from 15psi upto 40 psi.
Never as high as 70!!
Cheers
Hairy

FollowupID: 466817

Follow Up By: Member - Shane D (QLD) - Saturday, Nov 25, 2006 at 17:31

Saturday, Nov 25, 2006 at 17:31

how ya goin' Chris
just a quick line with regards to having 70 PSI ex factory is that when the vehicle is in assemble the tyres are also production line spec and they are not checked for pressure when assembled,this should've been done as a pre delivery inspection/service (you know,the $1400 dealer delivery job).I have 235/85 16(splits) on my 100series and run at about 35 all round but it's not carrying any extra weight,And i found my portable arb compressor works heaps faster on these tyres then pumping up the 31.5/10.5 r 15's (tubeless) that I had on my last vehicle,maybe your compressor not up to scratch?

FollowupID: 466834

Reply By: Member - John and Val W (ACT) - Saturday, Nov 25, 2006 at 14:15

Saturday, Nov 25, 2006 at 14:15

Chris,

50/70 psi sounds awfully high to me. My FJ75 troopy on split rims gets 45 all round when unladen, 45/50 loaded on bitumen. On bad corrugations I drop down to about 30/35, on fine sand to about 20/22, and a bit less on coarse sand.

Where did the 70psi figure come from? Not the rating plate on the door pillar surely? The highest shown on my rating plate is 390kpa, about 58psi.

HTH

John

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AnswerID: 206839

Follow Up By: Member - Chris R (NSW) - Saturday, Nov 25, 2006 at 14:29

Saturday, Nov 25, 2006 at 14:29

Hi John

WHOOPS!!

You forced me to go read the manual again.
Quote FRONT unladen or laden 36psi
REAR unladen 40psi laden 69psi.

Think I'll go let down some tyres??? Seems one's about right... but how did the airpump know?

Thanks for the prompt from you and Willem.

Cheers

Chris

FollowupID: 466818

Follow Up By: Crackles - Saturday, Nov 25, 2006 at 15:39

Saturday, Nov 25, 2006 at 15:39

Agree totally with your preasures John. To get a little more stability on a laden Troopy with skinny tyres, preasures do need to be be about 5 to 10 PSI higher than a Prado etc.
Cheers Craig..........

FollowupID: 466831

Reply By: Member - Phil G (SA) - Saturday, Nov 25, 2006 at 15:18

Saturday, Nov 25, 2006 at 15:18

Chris,
You usually need higher pressures than what you are used to with tubeless tyres on the Prado.

When I used to run 8ply tyres on splits, 36F/40R was my common bitumen pressures. The rear would increase to 50+ when laden. On a hot day with a full load, the tyres can get pretty hot, so plenty of pressure helps keep them cool.

On outback dirt roads, Adam Plate from Oodnadatta roadhouse has 30/36 on his tyre pressure chart for your vehicle.

On sand, you go down to whatever you need to, but if you use all the horses under the bonnet of your TD, you can turn the tyre and tube on the split rim, which can tear out the valve. But at least with splits you won't roll a tyre off the rim.

You'll enjoy your truck!

Cheers
Phil

AnswerID: 206845

Follow Up By: Member - Chris R (NSW) - Saturday, Nov 25, 2006 at 15:44

Saturday, Nov 25, 2006 at 15:44

Thanks Phil,

Sounds much better. Just fixed the air hose and now have them at 36/40 all round for bitumen - and looking forward to a bit less buuummppy ride!

Chris

FollowupID: 466832

Reply By: Bob Y. - Qld - Saturday, Nov 25, 2006 at 16:02

Saturday, Nov 25, 2006 at 16:02

Chris,

Limited experience with Troopys, but have used 75/79 series utes over a period.

With a youthful staff here, we keep tyre pressures @ a standard 38-40 psi, using 750x16" on tojo splits. On the occasion that we are carrying a heavy load, such as sand, or gravel, then we up the rears to 50.

The use of 70 psi in the rear as per handbook would be similar to driving with steel tyres, I'd suggest.

Enjoy the troopy,

Hooroo...

Seen it all, Done it all.
Can't remember most of it.

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AnswerID: 206850

Reply By: Sign-man - Saturday, Nov 25, 2006 at 16:17

Saturday, Nov 25, 2006 at 16:17

We run 38 front & rear on splits Troopy 75 series

AnswerID: 206852

Reply By: Member - Michael J (SA) - Saturday, Nov 25, 2006 at 17:49

Saturday, Nov 25, 2006 at 17:49

I'm with Signman,

Used to have "recommended" pressures but found them much too high and shocking ride.

Lowered pressure, comfy ride and no additional wear or problems.

Cheers
Michael

AnswerID: 206864

Follow Up By: Member - Chris R (NSW) - Saturday, Nov 25, 2006 at 23:37

Saturday, Nov 25, 2006 at 23:37

Replies really appreciated.

I'll try the lower pressures on some of the terrain that troubled the troopy last few times.

Michael - hope you're right re the improvement in ride. It truly was a shocker ....

Thanks to all

Chris

FollowupID: 466884

Reply By: Richard Kovac - Sunday, Nov 26, 2006 at 16:38

Sunday, Nov 26, 2006 at 16:38

Hi Chris

We run 55 psi rear and 40 psi front on road max speed 100 km (7.50R16 Road Grippers on splits)
always fully loaded at 3.34 Tonne

We will drop 10 psi front and rear when on dirt road and will not travel over 80 km 4th gear.

we haven't done much beach sand driving, but would drop another 10 psi both front and rear

We have found that 10 psi drop hot is around the same when cold..
e.g. hot 45 psi front drop 10 psi = 30 psi when cold, 60 - 65 psi rear drop 10 psi = 45 psi when cold

We have had one flat on the Troopy in 3 years 85000 km and that was under the car port at home.. Tube when installed creased and rub thought (we run truck tube).

Regards

Richard

AnswerID: 206966

Follow Up By: Member - Chris R (NSW) - Monday, Nov 27, 2006 at 08:59

Monday, Nov 27, 2006 at 08:59

Thanks Richard

YThat's one heavy Troopy! You're very careful or very lucky re the flats. I went through a period of a couple a day a few years back. But of course none with the troopy yet as it hasn't been anywhere exciting. But watch out - 2007 travelling full-time.

Best regards

Chris

FollowupID: 467033