8 stud tubeless rims to suit 1973 Denning

Hi V8Ian
I am using a TPMS which is very accurate. I have spot checked its readings against a digital pressure gauge to confirm this.
Brakes are not dragging and wheel bearings were re-packed before this trip.
Cheers
Ash

Hi Cobbadog
It sure points that way but everything appears fine. I always touch the bearing cap when getting getting out and they were never hot, just warm.
I trust the TPMS. I dropped the pressure each morning, when cold and used a digital gauge to check. The TPMS was nearly identical i.e. within a couple of psi.
I know it seems a ridiculous amount of pressure increase. Even now I start off at 85psi and they get to 110psi.
Very strange indeed.
The drive tyres start at 85psi and never get over 95psi
Cheers
Ash

Thanks jon_d
I'll do the calcs and see.
The issue I have is no matter what pressure I start with they increase by around 30 psi
Cheers
Ash

Hi Everyone and thankyou for your comments and advice

I have done the calculations per jon-d's formula.

Max cold pressure is 120psi / max load of the tyre 3075kg x axle weight 4740kg / 2 = 92.5psi

I spoke with a technical adviser at Bridgestone who confirmed that but he also said they add up to 10% safety margin. He suggested that I run cold pressure around 95psi and that an increase of up to 30psi when running is not an issue.

Still seems like a lot of pressure buildup to me.

I think I'll still chase up new rims (thanks jon-d for hopefully pointing me in the right direction) and tubeless tyres.

Cheers

Ash

Neighbor was running 90 psi in his drive and trailer tyres carting gypsum in 40 degree february heat a few years ago, and over a few days blew several. His lad heard of his troubles and told him to pump them all up to 110 psi. No more tyre trouble since.

Brett.

Quite so......heat buildup in tyres is from rubber and fabric flexing......not from the hot road.............I know tubeless run cooler because the walls are very thin ...like maybe a 1/4" ........heavy tube tyres are over 1" thick walls including tube..........downside is a small cut will blow out a tubeless wall,but do nothing to a tube tyre...................."Never bleed pressure from a hot tyre"

Are you sure there are no worn parts on the front end or a bad toe in?
The other slight area that gains a little bit of heat in tubed type tyres is the tube flexing against the tyre as well. The built in safety factor in tyres and pressures are higher than the 10% stated. Going by what we were taught it was quite a bit higher than that.

Hi Cobba
I had a weird steer tyre wear issue going on a little while ago. King pins have been done since as well as back axle pushed 5mm forward on the passenger side.
Now these issues have been corrected I guess I should return for another wheel alignment.
Perhaps correcting these things may reduce the pressure build up also.
Cheers
Ash

Alloy Rims suck a lot of heat out of Tyres Too.. You pull up after a several hour long Stint, & the Tyres on alloy rims will be Heaps cooler than the Tyre on Steel Wheels..!!

The general theory on the motor home forums is that under inflated tyres will blow out before over inflated.
Mainly because, the wide walls flex and balloon at the bottom which causes the heat to build up.

And of course, motorhomes are loaded to the max all the time, which contributes to issues.