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Bouncing Burstner
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userweldted
Posted: 13 August 2020 4:44 PM
Subject: Bouncing Burstner
 
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Hi all, we have a 2019 Burstner Iexo 736 A class. Currently in France but am finding it very tiring When driving as anything other than smooth tarmac is literally shaking the van to pieces. We have Michelin Agilis 225/75/R16 running at 5.0 bar. Michelin recommend 5.5 bar but have dropped it to try and ease the shaking.Van is on Fiat Maxi chassis rated at 4000kg. We are running at around 3850kg. We have had the overcab bed release one side twice, two cupboard doors hinges come loose, the flap over the control panel fell off. One rear curtain blind come away and the sun visors are now kept up with tape and the habitation door is catching on the bottom when opening it.
userSteve928
Posted: 13 August 2020 5:18 PM
Subject: RE: Bouncing Burstner
 


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Similar to my experience of 225/75R16 Agilis at those pressures. Plenty of discussion on this recent thread:
https://forums.outandaboutlive.co.uk/forums/Motorhomes/Motorhome-Matters/Tyre-pressures-Leap-of-faith-/55501/
userSydney1
Posted: 13 August 2020 5:24 PM
Subject: RE: Bouncing Burstner
 


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Location: Surrey - 2017 2.3 150hp Fiat Burstner IT734


Worth checking the wheels are balanced as well and you haven't lost a weight
userTracker
Posted: 13 August 2020 5:52 PM
Subject: RE: Bouncing Burstner
 


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Location: Vanless in Evesham.


I am unable to reccomend dropping tyre pressures to around 60 ps rear and 50 psi front (sorry too old to convert to metric!) or to a level where the tyres just start to deflect as it stands (fully laden) due to legal and insurance consideration, and doubtless the purists will react badly to this hypothetical remedy..


But it worked for us on a similar weight Autotrail Cheyenne that had similaly unpleasant ride and handling charecteristics and for us the result justified the risk.

On your own head be it!!
userEJB
Posted: 13 August 2020 7:41 PM
Subject: RE: Bouncing Burstner
 
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If you Google 'Motorhome tyre pressures' I'm sure you will find one of the tables for your specific tyres.
Nowadays commercial transport guides taken up by the manufacturers seem to blanket motorhomes with maximum pressures.
Fortunately I still have the tyre manufacturers sensible recommended pressures for my tyres....which are still current.....55/65PSI.
Not all manufacturers go down the 80PSI route...but no doubt they soon will.




Edited by EJB 2020-08-13 7:43 PM
userKeithl
Posted: 13 August 2020 8:13 PM
Subject: RE: Bouncing Burstner
 


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Here is a link to a recent Continental tyres technical databook

https://blobs.continental-tires.com/www8/servlet/blob/85806/e0854f2c7866c64da551474b998ef8b3/download-technical-databook-data.pdf

Van tyres start at page 80 then look for your tyre size. As long as the Load Index figure is the same then the pressure versus load figures should be valid.

Ted, are your tyres 'C' or 'CP' marked?

Keith.
userBS20
Posted: 13 August 2020 8:48 PM
Subject: RE: Bouncing Burstner
 
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When I needed a tyre change I emailed Michelin ref- Agilis Camping tyres with weight's of front and rear axle with 75% loading of van and they recommended 65.27 psi 4.5 bar front. and 80 psi 5.5 bar rear, and we have a good ride on most conditions.
.
Mike
userthebishbus
Posted: 13 August 2020 8:52 PM
Subject: RE: Bouncing Burstner
 


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I found that I had a choice, run at the recommended 80 psi and put up with all the banging around , or lower the fronts by 10 to 15 psi and the rears by up 10 psi and have a more comfortable ride, but run the risk of premature ageing the tyres, ie, cracked walls . When I replaced my tyres this year the treads were fine but the walls were cracking, I suspect because of running at the lower pressures.
Brian B.
userBrian Kirby
Posted: 14 August 2020 9:38 AM
Subject: RE: Bouncing Burstner
 


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Location: East Sussex. Motorhome: Knaus Boxstar 600 Street


Keithl - 2020-08-13 8:13 PM
Here is a link to a recent Continental tyres technical databook
https://blobs.continental-tires.com/www8/servlet/blob/85806/e0854f2c7866c64da551474b998ef8b3/download-technical-databook-data.pdf
Van tyres start at page 80 then look for your tyre size. As long as the Load Index figure is the same then the pressure versus load figures should be valid.
Ted, are your tyres 'C' or 'CP' marked?
Keith.

But, before you begin trying lower pressures Ted, you would be wise to check both front and rear axle loads at a weighbridge (pont bascule).

Over inflation, which may be the cause of your present problem, isn't actually dangerous, but underinflation, where the tyres have insufficient pressure to sustain their actual load, leads to overheating of the tyres and possible blowout, which definitely is dangerous.

Which pressures are appropriate on which axle depends so much on the layout of your van, the length of its rear overhang, and where the loads are placed, that no one else's experiences can offer a reliable guide to what would be appropriate in your case.
userron.
Posted: 14 August 2020 10:24 AM
Subject: RE: Bouncing Burstner
 
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Years ago a Michelin technician told me that the recommended 80psi figure wasn’t the optimum pressure for their camping tyres but a compromise to prevent the unknowing from overloading their tyres. He suggested contacting Michelin for the correct tyre pressures but giving the rear axle loading as if it were the front axle (also adjusting the rear figure to suit if things look a bit odd) If you think about it the pressure then given for the ‘front’ tyre with all the strain of breaking, steering, etc, must be good enough for the rear. Then get a friend to do the same but quoting the correct axle loadings. You then have the optimum and correct pressures for both axle loadings. It’s served me well over four vans now and the ride difference is markedly better without any problems.

Ron.

Edited by ron. 2020-08-14 10:26 AM
usercolin
Posted: 14 August 2020 10:28 AM
Subject: RE: Bouncing Burstner
 


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Brian Kirby - 2020-08-14 9:38 AM

Over inflation, which may be the cause of your present problem, isn't actually dangerous, but underinflation, where the tyres have insufficient pressure to sustain their actual load, leads to overheating of the tyres and possible blowout, which definitely is dangerous.



I would argue that driver fatigue, distraction with rattles and bumps, esp. if it's soo bad the visors need taping up, plus possible reduced grip, all make running at too high a pressure more dangerous than running at the correct pressures.
userDeneb
Posted: 14 August 2020 1:07 PM
Subject: RE: Bouncing Burstner
 
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Brian Kirby - 2020-08-14 9:38 AM
Over inflation, which may be the cause of your present problem, isn't actually dangerous, but underinflation, where the tyres have insufficient pressure to sustain their actual load, leads to overheating of the tyres and possible blowout, which definitely is dangerous.



And underinflation of rear tyres particularly can also affect the design handling characteristics of the vehicle, promoting a tendency towards oversteer which, whilst maybe not apparent during normal driving conditions, can be potentially extremely serious if sudden or coarse braking or steering corrections are necessary (such as in an emergency situation which is the very time that you want your tyres to perform to the best of their ability). Don't underestimate the handling issues that underinflated rear tyres can cause in certain situations. They can be sudden in onset and extremely vicious, with little or no advance warning and no opportunity to correct them.

Tyre manufacturers or technicians, whilst they may be perfectly qualified to advise on the load capabilities vs. pressures of their tyres, have no experience of the extensive tyre testing undertaken by the vehicle manufacturer to achieve a safe handling characteristic (normally neutral to slight understeer) for their vehicle, which in my personal experience has in itself led to at least one fatality during such testing.

Proceed with caution, and be aware that the tyre manufacturer's guidance relates solely to the capabilities of their tyre, not its interaction with the vehicle.
userweldted
Posted: 14 August 2020 1:50 PM
Subject: RE: Bouncing Burstner
 
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Location: Burstner Ixeo 736


2110 kg rear, 1730 kg front. Rear tyre pressure 5.5 bar, front tyre pressure 5.0 bar. Have tyre pal monitor pressures rise by around .5 bar when driving current weather 29c.
userTracker
Posted: 14 August 2020 2:33 PM
Subject: RE: Bouncing Burstner
 


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Location: Vanless in Evesham.


Deneb - 2020-08-14 1:07 PM
Underinflation of rear tyres particularly can also affect the design handling characteristics of the vehicle, promoting a tendency towards oversteer which, whilst maybe not apparent during normal driving conditions, can be potentially extremely serious if sudden or coarse braking or steering corrections are necessary (such as in an emergency situation which is the very time that you want your tyres to perform to the best of their ability). Don't underestimate the handling issues that underinflated rear tyres can cause in certain situations. They can be sudden in onset and extremely vicious, with little or no advance warning and no opportunity to correct them.

Proceed with caution, and be aware that the tyre manufacturer's guidance relates solely to the capabilities of their tyre, not its interaction with the vehicle
.


This is absolutely true as my experimentation with tyre pressures for a quieter ride determined many years ago long before such information was available online.
Rear understeer is very frightening and is almost impossible to stop once it starts unless you are able to correct it instantly due to the inertial impetus caused by of the height, width and weight of the motorhome conversion.
I also found that getting the back tyres right was the basis of a good compromise with front tyres less crucial but generally ending up around 5 psi less that the rears to help with handling on both front and rear wheel drive vans.
Much has moved on since those free and easy days so great care is needed not to make an unpleasant van lethal.
When I did most of my experimentation I had a good friend who ran an old fashioned tyre supply and fitting company and his help based on his years of experience was invaluable - and off the record.

Edited by Tracker 2020-08-14 2:37 PM
userBrian Kirby
Posted: 14 August 2020 3:15 PM
Subject: RE: Bouncing Burstner
 


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Location: East Sussex. Motorhome: Knaus Boxstar 600 Street


colin - 2020-08-14 10:28 AM
Brian Kirby - 2020-08-14 9:38 AM
Over inflation, which may be the cause of your present problem, isn't actually dangerous, but underinflation, where the tyres have insufficient pressure to sustain their actual load, leads to overheating of the tyres and possible blowout, which definitely is dangerous.

I would argue that driver fatigue, distraction with rattles and bumps, esp. if it's soo bad the visors need taping up, plus possible reduced grip, all make running at too high a pressure more dangerous than running at the correct pressures.

Absolutely Colin, the correct "pressure for load" is the holy grail. But, for all the disadvantages of overinflation on the scale we're talking about, (including your fillings falling out! ), at least it shouldn't lead to catastrophic tyre failure.
user747
Posted: 14 August 2020 3:27 PM
Subject: RE: Bouncing Burstner
 


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Tyresafe give pressures of 49 psi Front and 80 psi Rear for your vehicle.

Out of curiosity (because Tyresafe ALWAYS quote 5.5 Bar for rears, apart from Tag axles) I also inputted your Rear axle loading as your front and inputted 2400 Kg as your Rear loading. What it computed was 63 psi Front (at 2110) and 80 psi Rear (yawn).

What you want to do (if anything) is up to you ... but there is no way whatsoever that I would run a similar van at those pressures. I am not qualified to give safety advice on Tyres.
userEJB
Posted: 14 August 2020 4:21 PM
Subject: RE: Bouncing Burstner
 
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Keithl - 2020-08-13 8:13 PM

Here is a link to a recent Continental tyres technical databook

https://blobs.continental-tires.com/www8/servlet/blob/85806/e0854f2c7866c64da551474b998ef8b3/download-technical-databook-data.pdf

Van tyres start at page 80 then look for your tyre size. As long as the Load Index figure is the same then the pressure versus load figures should be valid.

Ted, are your tyres 'C' or 'CP' marked?

Keith.


Always used campers...Agilis Campers and VancoCamper C
I used to lecture on the technicalities of understeer and oversteer so I submit to the experts!

Edited by EJB 2020-08-14 4:30 PM
usercolin
Posted: 14 August 2020 5:04 PM
Subject: RE: Bouncing Burstner
 


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747 - 2020-08-14 3:27 PM

Tyresafe give pressures of 49 psi Front and 80 psi Rear for your vehicle.

Out of curiosity (because Tyresafe ALWAYS quote 5.5 Bar for rears, apart from Tag axles) I also inputted your Rear axle loading as your front and inputted 2400 Kg as your Rear loading. What it computed was 63 psi Front (at 2110) and 80 psi Rear (yawn).

What you want to do (if anything) is up to you ... but there is no way whatsoever that I would run a similar van at those pressures. I am not qualified to give safety advice on Tyres.


That's assuming a CP tyre, my van on the Maxi chassis if had same axle loads would be much less as it uses C tyres as standard, and the comical thing is they are ,according to Conti, built as 'Camping' tyres.
Here is the Tyresafe comment on CP tyres.
CP-type tyre construction enables the use of higher inflation pressures to provide resistance to the difficult conditions of use encountered on motorhomes. Therefore, when CP-type tyres are fitted on the rear axle in a single formation set the inflation pressures to 5.5 bar (80 psi) for all loads
userBrian Kirby
Posted: 14 August 2020 5:07 PM
Subject: RE: Bouncing Burstner
 


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Location: East Sussex. Motorhome: Knaus Boxstar 600 Street


weldted - 2020-08-14 1:50 PM

2110 kg rear, 1730 kg front. Rear tyre pressure 5.5 bar, front tyre pressure 5.0 bar. Have tyre pal monitor pressures rise by around .5 bar when driving current weather 29c.

With those tyres (225/75/R16 Agilis Camping), at those loads, the Tyresafe publication tables suggest 3.5 bar front (the minimum pressure recommended!), and 4.5 bar rear. However, Tyresafe add the following footnote regarding pressures for rear axles with CP type tyres fitted: "for CP-type tyres when fitted in a single formation on a motorhome rear axle, set the inflation pressure to 5.5 bar (80 psi) for all loads." Michelin themselves will not currently recommend any lower pressure than 5.5 at the rear.

Fully laden, ours (on the same tyres) is 1,940kg front and 1,880kg rear, and I've been using the Tyresafe pressure recommendations for the front axle, also giving 3.5 bar front. Ours is a 6.0M Ducato PVC on the maxi chassis, so a good bit smaller, and the ride is inevitably firm, but reasonably compliant. Directional stability and general handling are fine at those pressures.

The problem with reducing the front as low as 3.5 in one hit might be that it begins to feel as though it is wandering at the front and or is running a bit wide on bends, but it should reduce at least some of the harshness you're experiencing. You could perhaps experiment by reducing 5 psi at a step, and then see how it drives, and so on. After all, you've 22psi to play with!!

Ideally, try to get a recommendation for at least the front from Michelin by e-mail, then you will have confirmation should you need it.
usercolin
Posted: 14 August 2020 5:10 PM
Subject: RE: Bouncing Burstner
 


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Brian Kirby - 2020-08-14 3:15 PM

colin - 2020-08-14 10:28 AM
Brian Kirby - 2020-08-14 9:38 AM
Over inflation, which may be the cause of your present problem, isn't actually dangerous, but underinflation, where the tyres have insufficient pressure to sustain their actual load, leads to overheating of the tyres and possible blowout, which definitely is dangerous.

I would argue that driver fatigue, distraction with rattles and bumps, esp. if it's soo bad the visors need taping up, plus possible reduced grip, all make running at too high a pressure more dangerous than running at the correct pressures.

Absolutely Colin, the correct "pressure for load" is the holy grail. But, for all the disadvantages of overinflation on the scale we're talking about, (including your fillings falling out! ), at least it shouldn't lead to catastrophic tyre failure.


Just noticed the comment "and the overcab bed release one side twice" if this is the result of too harsh a ride due to overly hard tyres (I'm a mite surprised at that) then it is exceedingly dangerous if the whole thing comes down.
userweldted
Posted: 14 August 2020 11:20 PM
Subject: RE: Bouncing Burstner
 
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Bed is now secured with fixed blocks as there are only two of us it is not in use. It has always rattled from new. I have had quite a few motorhomes over the years the last four all bought from new. This is the most uncomfortable ride and poor build quality and typically the most expensive one yet.
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