Club Touareg Forum banner
21 - 33 of 33 Posts

·
Registered
Joined
·
169 Posts
We have a 3380kg ATM van and generally within 100 kg so around 3200 to3300 with ball weight around 260-270kg on our 180kw 2015.
I use 34 front and 46 rear on the Touareg AND 45 on front axle and 50 on rear axle of van.
It was noticeable the difference with different axle pressure on the van. Theoretically the van pressures were calculated using the weight and pressure of actual versus max of tyre
This is a result of a guy called Collyn Rivers on another forum suggesting working out theoretical and dropping front axle by a few psi and increasing rear by same amount. This is for both van and towing vehicle. Theory correct ??? Placebo effect ??? Who knows but it does seem to work for me.
It's a real effect. A twin-axle trailer (caravan) is a statically indeterminate system.

When a fixed structure is supported at just two points (front and back), it is statically determinate. This is the case for a single-axle trailer. You can calculate the loads on it with simple high school physics. The weight borne by each support point (tongue and axle) is proportional to their distance from the trailer's center of mass. So you can shift the loading towards the front or the back only by moving the trailer's center of mass forward or backward. (As an engineer, you can also modify weight distribution by moving the support points forward or back, but that's not an option in an already-manufactured trailer.) Raising or lowering the front/back doesn't matter, at least not until you get to extreme angles.

A statically indeterminate system doesn't work like this. Moving the center of mass forward or back (or moving the support points forward or back) isn't the sole determining factor in how much weight gets put on each support point. The height of each support point also makes a huge difference. Higher supports end up bearing more weight. You can think of this in the extreme case where the tires on the front axle are so deflated that they no longer touch the ground. That axle is now supporting zero weight, while the rear axle supports all the weight (minus the tongue weight). Now reverse the pressures so the rear axle is underinflated, and the front axle supports all the weight while the rear axle supports none.

So yes, varying the front/rear axle tire pressure has a real effect on the trailer's weight distribution. So does the hitch height, which is why they say to always run twin-axle trailers with the proper hitch height so that it's level. That's vital for assuring load is distributed between the hitch and front/rear axles as intended. There was a post a few months back by a guy whose trailer dealer rigged it up wrong. The hitch height was way too low, causing the twin-axle trailer's rear axle to lift and support less weight. The trailer's front axle was bearing nearly all of the load, meaning the trailer's center of mass was further back relative to the wheels on the ground, causing it to sway.

This is less true for the tow vehicle (which only has two support axles), assuming you're using a simple tow ball (pivot joint) with downward tongue weight. In the U.S., it's popular to use a weight distribution hitch, which does not let the connection between trailer and tow vehicle pivot freely. That couples the trailer with the tow vehicle in pitch, creating a more complex statically indeterminate system (effectively a fixed structure with 4 support axles), allowing you to transfer the trailer's tongue weight to the front or back of the tow vehicle as desired (basically adjusting the pitch angle at which the tow vehicle and trailer meet).

The wiki article on this is a bit too technical. But you can read through it if you want to learn more and can follow the math.
 

·
Registered
Joined
·
106 Posts
I take it you're not proposing to do any extended towing with the 295/35's?
Just asking seeing you posted this in a towing related tread.....

TonyB
You would be wrong Tony, I tow a 3.2t van regularly and have absolutely no problem with tyres, I don’t drive off road and have no interest in doing so in the Touareg so the highway only tyres I use suit my needs perfectly.
 

·
Registered
Joined
·
2,023 Posts
F'nuff, your call obviously.

I was not referring to type of tyre fitted but rather to the profile size fitted. Whilst 104mm of sidewall height may be ideal for spirited performance driving and roadholding applications I do not believe 104mm is a good sidewall height when towing a heavy caravan when the tyres are expected to deal with increase pressures and temperatures due to speed and the extra load carried, even on the best and smoothest highway we have in our country.
Whilst I have no doubt you have had no trouble so far I did say "extended" towing and to my way of thinking there are many far better tyre sizes/profiles for towing applications, that is possibly why I have yet to see a low profile tyre fitted to a caravan by the manufacturer.

TonyB
 

·
Registered
2017 R Line V8
Joined
·
158 Posts
Discussion Starter · #24 · (Edited)
Have done two runs now with the revised tyre pressures of 36psi front, 44 rear on the Touareg and 37 front, 40 rear on the caravan. 440Km from Bowen to Kurramine Beach and 150Km from Kurramine Beach to Cairns.
Like Fred said it may be placebo but it does feel like it has made a positive difference.
Strong gusts of side wind still have an effect but passing a truck in either direction there is no movement in the van.
With the van previously set at 40 front and rear I occasionally felt a slight wag of the tail when initially backing off from 100Km/H or more, this has gone with the new pressures.
Next run I will drop the Touareg fronts down to 35 and the van fronts to 36 as both of these only rose 3psi on the runs while the rears on both rose 4 psi.
It does take a quite a long run to get the 4psi rise in the rears of the van so they may still be slightly too high.

I'm with you Tony not keen on low profile tyres for towing hence I replaced the original 21s with 19s to get the extra side wall. The rear tyres on a tow vehicle heat up much quicker than fronts or the van tyres as they are working the hardest.
Preferable to have as much side wall as possible to take some of the shock on the wonderful roads we have !

I seem to remember reading that the Touareg lowers itself above a certain speed is this correct ?
The R Line ride height is the same for both Sport and Normal but raises when set to Comfort.

Kym
 

·
Registered
2017 (MY2018) V6 TDI - Deep Black Pearlescent
Joined
·
350 Posts
I think the Touareg lowers itself at 120kph
 

·
Registered
2017 R Line V8
Joined
·
158 Posts
Discussion Starter · #26 ·
I think the Touareg lowers itself at 120kph
Van is sitting level so was interested if the Touareg lowered itself as it would upset the balance.
Don't plan on hitting 120 with the van on the back.
 

·
Super Moderator
2015 R Line V8
Joined
·
2,472 Posts
Whilst I have no doubt you have had no trouble so far I did say "extended" towing and to my way of thinking there are many far better tyre sizes/profiles for towing applications, that is possibly why I have yet to see a low profile tyre fitted to a caravan by the manufacturer.

TonyB
Not sure that there is a low profile tyre available from China (where most caravan manufacturers get there hoops from) that are of Light Truck construction/specification and fall within the manufacturers business model of "cheap as they can get".

There are plenty of people who use OEM rubber (spec/dimensions) on their tow cars, and whilst not ideal (endurance, cost of replacement, availability etc) it does come down to personal choice.
 

·
Registered
Joined
·
557 Posts
I take it you're not proposing to do any extended towing with the 295/35's?
Just asking seeing you posted this in a towing related tread.....

TonyB
Hi Tony, I am curious why you say about not proposing to do any extended towing with 295/35's. I have an R50 which has the 295/35 21" wheels from the factory and just got back from an uneventful (for the R50 at least) 2200km trip to North West Aus which we did same time last year as well. Whilst they're low profile, what is the reason you indicate potentially not suitable for extended towing? There have been no problems and nor do I expect problems with the 295/35's. I keep within the load rating of the tyre and car.

Regards

Pete.
 

Attachments

·
Registered
Joined
·
2,023 Posts
Hi Pete, nice big rig you got there!

I firmly believe low profile tyres are not a good option if you plan to do extended towing primarily due to the lack of sidewall height and the sidewall construction (read less sidewall ply/strength) of these so called "performance" tyres.

I have had low profile tyres fitted to some of my vehicles over the years and I have damaged tyres and rims just driving on sealed roads with these tyres but as yet I have not damaged any "normal" 60+ profile, I believe that is due to the fact that larger profile tyres have the ability to absorb more punishment without damage due to the higher amount of sidewall rubber/strength available to absord impacts and shocks.

Tyre manufacturers design tyres for particular applications and I would really like to see anyone argue that a 35 XY or Z rated low profile tyre is as good in an extended towing application as a 55/60/65+ profile tyre.

I'm not and have not been involved in the tyre business so my personal opinions are just that, gained over some years of being interested in the subject so that I can make the best tyre purchase choice for my specific needs, that is why in
the past ten years, I have used two sets of tyre and rim combinations for my street and offroad/towing applications.

It's no skin off my nose what tyre size/construction/profile anyone on this forum choose to tow or offroad with but please do not put the argument forward that "I have done "xx" amount of distance towing with my (low profile) tyres with no issue" as a justification that I am running a suitable tyre for "my" towing application............... in my view there are much better choices out there for this application, but don't take my word for, talk to people in the industry and ask for their recommendations on what tyre you should consider to put on your vehicle in your towing application.

Ending my rant on this subject, good luck to those that choose to run low profiles, hope you avoid any potholes in your path....


TonyB
 

·
Registered
2013 V8 R-Line
Joined
·
317 Posts
Just to chime in with my setup while towing.
I have a Jayco road caravan with 14"tyres (dual axle) and tow with the pressures in them at around 48psi. I have a 2013 V8tdi R-Line and I have replaced the 21's with 20"all Nitto Terra Grappler terrain tyres. My van weighs around 2.6T I reckon on average and the tow ball weight is around the 230kg mark from memory. I run 40psi in the fronts and 43psi in the rear when towing and my set up is spot on. The van travels beautifully. I have the suspension setting in normal mode as I was advised of this after asking this question a few years ago now and I have not had once ounce of an issue in the 15,000 kilometres or so of van towing that I have completed in the last 5 years. Alot of this comes down to how well you have your van packed so that the weight that the van forces down on your towball is as close to 10% of the van weight. Well thats what they like it to be so they say. Too light in the front and you get the tail wagging the dog scenario. Everyone's setup will be slightly different. With regards to the pressures increasing due to heat build up. Last time I checked all the van tyre pressures via a gauge and the car tyres pressures via the dash, they were all within the 4psi increase which is all good as far as I am concerned. When I was travelling out western Queensland, I did bump the rear tyre pressures up a couple of psi to 45 as I had a little more weight in it as I was travelling for about 10 weeks and the most I saw the rears get up to was 50psi.
Out of interest, my dad tows a 3.2T Nova Caravan with his 2019 Audi SQ7 with the optional 22" rims with 295/35 hankook tyres on and hasn't had any issues whatsoever. Not sure on the tyre pressures he was running but he is in the throws of selling his van so there won't be any more adventures for him anyhow.
 
  • Like
Reactions: Crispy3

·
Registered
Joined
·
557 Posts
Hi Tony, thanks for that and yes we all have the freedom of tyres we choose and I've no challenge with your rationale. Yes potholes are more hazardous to lower profile tyres whatever the loading (even if you're not towing) so no argument on that score.

Regards

Pete.
 

·
Registered
Joined
·
106 Posts
I don't see any problem with towing on 'so called' low profile tyres, provided the tyres are rated for the weight then it has no further impact over traveling the same roads without the van in tow. As long as we all understand that what is being argued here are opinions not facts then everybody has a right to theirs. In my opinion I find the lower profile performance orientated, highway terrain tyres a lot safer, they are more sure footed on the road and offer far better grip and steering response due in part to the less side wall flex and that is why I choose to fit them. Towing only adds 280k's maximum to the cars weight over the rear wheels so the extra weight is a non issue for me. I run the rears at 48psi and fronts at 40 psi. The trade off is ride comfort and yes they are more prone to damage then tyres with more side wall and that is a risk, but its not bigger risk then traveling the same roads with a boot full of luggage and a couple of people in the back seat.

BTW, the Touareg with air suspension will only lower to the 'normal' ride height at 120kph if the suspension is in comfort mode.
 

·
Registered
Joined
·
557 Posts
I don't see any problem with towing on 'so called' low profile tyres, provided the tyres are rated for the weight then it has no further impact over traveling the same roads without the van in tow. As long as we all understand that what is being argued here are opinions not facts then everybody has a right to theirs. In my opinion I find the lower profile performance orientated, highway terrain tyres a lot safer, they are more sure footed on the road and offer far better grip and steering response due in part to the less side wall flex and that is why I choose to fit them. Towing only adds 280k's maximum to the cars weight over the rear wheels so the extra weight is a non issue for me. I run the rears at 48psi and fronts at 40 psi. The trade off is ride comfort and yes they are more prone to damage then tyres with more side wall and that is a risk, but its not bigger risk then traveling the same roads with a boot full of luggage and a couple of people in the back seat.

BTW, the Touareg with air suspension will only lower to the 'normal' ride height at 120kph if the suspension is in comfort mode.
Thanks Paulie, I couldn't have put it better myself!

Regards Pete.
 
21 - 33 of 33 Posts
Top