Tyre Pressures.

Yuglamron · Guru

Tyre Pressures.

Mike Harding · Guru

I foresee all sorts of unforeseen problems with such a plan.

Peter_n_Margaret · Guru

Yes, this is done, but I am unsure what the system pressure is.

Cheers,

Peter

Mike Harding · Guru

Peter_n_Margaret wrote:
Yes, this is done

And how do insurance companies feel about such a modification after you inform them?

Peter_n_Margaret · Guru

I am aware of one vehicle so equipped that I believe is original equipment.
Many modifications can be easily and appropriately approved even if not original.

Cheers,
Peter

Dr Ric · Newbie

You will need to find out the maximum design pressure for you air receiver and what the pressure relief valve is set at.

Most trucks would run between 8 & 12 Bar (115 - 174 psi) What you might have problem with is the volume of air required.

Cheers

Yuglamron · Guru

I'll have to check with MAN service for the relief valve pressures.

I agree the sheer volume of air is the problem. Using my compressor it's the major issue, sheer volume. I do normally use truck stop airlines but have to let the tyres cool before I use them and they are notorious for being inaccurate.

Glad I only have 17.5" tyres not 22" like a semi.

It was a passing thought after reading a post about tyre filling at servos with only 60psi being the norm.

Thanks for all the replies I'll have to do some more research.

Bass · Senior Member

I did this with my truck. Fantastic and quick and safe. If i had a motorhome would do the same. A lot of trucks have done it.

Hylife · Guru

Poor handling is usually because most people either run too much or too little pressure in their tyres

Step 1. For a motorhome know your axel weights. Go over a weighbridge and record the weights over each axel separately.
step 2. Use the international industry formula that has been used for 30 plus years, it is embossed onto every tyre sidewall.
As every tyre model is designed differently they all have different weights and pressure requirements, even if it is an identical size to a previous tyre model.
You cannot use the tyre placard or handbook unless you are using the exact identical make and model tyre that was fitted by the vehicles' OEM when it was new.
Look on the side wall of your tyres and note down the maximum pressure.
That maximum pressure is only used when you are loading the tyres with the maximum weight that those tyres are allowed to carry.
step 3. Find the load rating of your particular tyres, not what you find in some handbook or tyre placard. If they are not stamped on the side wall then ask a tyre retailer to look it up.
step 4. Divide the axel weight by the number of tyres on that axel. This gives you the weight per tyre for that axel.
Divide the weight per tyre by the maximum weight rating for your tyres to get the percentage of maximum weight you are placing on each tyre.
step 5. Pump up your tyres (cold) to the same percentage as the weight. eg, if carrying 70% of maximum weight on each tyre this means pump up to 70% of maximum pressure.

Aus-Kiwi · Guru

I have a little compressor for ours . Our old Fuso run brake line presure over 150 Lb . I fitted a regulator valve . To seperate tank which actually operated the door when it was a BUS . In the case the piston, door operated at 40lb . I just changed to reg to 90lb . Which I now use for airsuspension , tyres when required .

Jaahn · Guru

Mike Harding wrote:
Peter_n_Margaret wrote:
Yes, this is done
And how do insurance companies feel about such a modification after you inform them?

Hi smile

What a silly statement that is. All large trucks use the onboard air system to pump their tires if required. If you fit an outlet then you must fit it to the usual standard for the air system. Nothing unique there ! It has a low air alarm, a drain tap, which should be opened every day, and there is a procedure for checking the pump up time when starting from empty, which is checked in every inspection, and the driver would know what it should do anyway because of the buzzer, and check an irregularity if noticed, just like you do for any problem. Where is the perceived problem confuse

Jaahn

Mike Harding · Guru

Jaahn wrote:
Mike Harding wrote:
And how do insurance companies feel about such a modification after you inform them?
What a silly statement that is. All large trucks use the onboard air system to pump their tires if required

You think it's silly to suggest that if one modifies the braking system of a vehicle one's insurance company will have no interest in that modification do you?

It may well be done by trucks but that is part of the design and is approved under national regulations and is understood and accepted by the insurance company at the time they issue a policy.

If the insurance company refuses to pay up after you went into the back of a Rolls Royce because you modified the brakes and didn't tell them what's your contrary position going to be? "A bloke on the internet said it was OK because trucks do it!", perhaps?

As Peter mentioned you *may* be able to get a consulting engineer acceptable to your insurance company to approve the modification but, I suggest, by the time you have paid for that and, no doubt, an increased premium it would have been cheaper and easier to buy a decent electric compressor.

Aus-Kiwi · Guru

No one is suggesting using a garden hose etc . An outlet fitted in an approved manner . Sheesh . Here we go again . This isnât an electrical thread ??

aussie_paul · Guru

Aus-Kiwi wrote:
No one is suggesting using a garden hose etc . An outlet fitted in an approved manner . Sheesh . Here we go again . This isnât an electrical thread ??

Ha ha.... biggrin

Aussie Paul. smile

Jaahn · Guru

Hi smile

I can only say, if you know so little about trucks or general mechanics that you do not know the difference between "modifing" the braking system and tapping into the air pressure tanks then get someone else to do it for you. Get a truck qualified mechanic as working on the air system is normal practice.

Also If you know nothing about truck air brakes then do not comment on it either !!! hmm

For illustration, to compare it to another 'dangerous' practice, I would say do not attempt to fit an extra filter or 'modify' the fuel lines on your vehicle until you get written permission from your insurance company. You might cause a FIRE and burn down a Rolls Royce close by too. Jeese I read about doing that on the internet !!

Cheers Jaahn

-- Edited by Jaahn on Friday 13th of July 2018 02:17:14 PM

Peter_n_Margaret · Guru

An engineering approval for a modification like this would likely cost less than buying an alternative compressor.
Of course, if the particular vehicle type was ever fitted with this as an OEM option, then no approval would be required and a dealer could simply fit it.
There is no need to be paranoid about doing modifications to vehicles provided appropriate approvals are obtained and that is often easy to do and for moderate cost.

Modifications that I have done to our MH and which have been fully approved include:
Building and mounting a new body.
Building and fitting a home made tow bar rated to 3.5T.
Fitting seat belts to sideways facing seats with a fixed table between them in the rear of the camper section.
Fitting mounts for a child seat on the engine hatch in the front cab.
Increasing the GVM from 5.5T to 6.6T.
Increasing the GVM from 7T to 9T.

My advise is to talk to an approved engineer about what you wish to do and get his thoughts (and a quote) before you proceed with the work.

Cheers,
Peter

Mike Harding · Guru

I think some of you miss the point:
It's not me you have to convince or win an internet argument against
in order to preserve your ego because I don't care a jot what you do
to your vehicles - I have a sock drawer to rearrange! :)

What you do *have* to do is convince your insurance company that the
modification you have made does not invalidate the policy both you
and they agreed to and I strongly suggest you do this *before* you
make that modification because, as I said before, the argument that
"a bloke on the internet said it was OK" won't wash.

Frankly guys, if you're arguing against the above then you are
arguing that one may make any modification at all with impunity and
that is clearly absurd.

Your car, your insurance policy, your liability....

Peter_n_Margaret · Guru

No, you don't have to convince your insurance company that any modification will not invalidate your policy, you have to convince an approving engineer and his job is to approve anything that is OK and it is his neck that is on the line.
The insurance company on the other hand, can not refuse a claim unless the unapproved modification actually contributed to the accident.
In the case raised by the OP, the air brake system has fail safe arrangements that come into effect in the event of a loss of air pressure, so even a messed up modification is unlikely to cause a safety problem, not that that is a reason not to do it properly and have it inspected and approved.

Cheers,
Peter