Uprating GVW and tyre choices

[Karen0858]

Hi

 

We are uprating our Burstner to get a higher rating on the rear axle (2240 from the current 2000kg), by adding air suspension and changing the rear tyres to those with an index rating of 112 instead of the existing rating of 109. SVTech have advised that we only need to change the rear tyres so this will mean running rears with 112 and fronts with 109. We are also having to mix manufacturers because our existing tyres are Continental Vanco 215/70R15 CP 109R . They don't produce a 15 inch rim version at 112 load index (only for the 16 inch rim) so we are looking at Michelin Agilis for the rear.

 

Before anyone tells me to look at reducing our payload, we have genuine reason for wanting to increase the rear axle, though overall we will still be rated at 3850 which is the current rating.

 

Any advice regarding the tyres please?

 

Thanks, Karen

[Keithl]

Hi Karen,

 

What tyres are you looking at with a 112 rating?

I can only find 225/70 R15 with that load index and no 215's but I may not be looking in the right place!

 

My suggestion would be to change all 5 tyres for the correct load rating and sell your existing tyres as 'part worn' on the likes of eBay. When I replaced my 9 year old Conti tyres (not CP) I sold the 5 part worn for the cost of 2 of my new tyres!

 

Keith.

 

PS I was looking at the Michelin website here...

 

http://www.michelin.co.uk/tyres/van-motorhome-tyres#type=type_3&width=215&ratio=70&radial=15&load=109&selectedFilter=summer

[Karen0858]

Hi Keith,

 

I am looking at Michelin Agilis 225/70 R15. My existing Vanco are the 215 tyres. I can't find any Conti tyres for campers with 112 load index on 15" rims. I don't really want to replace all 4 tyres but I hear what you are saying. Might be interesting to see what I could get for them.

 

Karen

[Keithl]

OK But if you have different sizes front to rear you will not be bale to use your spare on one or other axle! If you do then you risk your ABS/ASR system from putting you in LHM!

 

You are far better getting all 5 changed IMO.

 

As I said before selling 5 nine year old Conit's paid for 2 of my new Conti's!

 

Keith.

[Robbo]

I always err on the safe side when choosing the load index. So called tyre experts recommend taking the maximum load on the tyre and adding 10% to determine the load index. I recall, Tyresafe.org also support this view.

 

This would make your required load index = 116. However, you may have difficulty finding that in a 15" tyre. So you'll probably be stuck with 112.

 

I guess the philosophy to use a higher load index is to provide an extra factor of safety against tyre failure from extreme vertical dynamic forces and/or overloading. However, I would assume that tyre manufacturers would take these factors into account when determining the safe load index.

 

But, as we all know, MH's do generally spend more time than other vehicles at maximum load, especially on the rear axle.

 

 

[Karen0858]

Thanks Robby

 

In your opinion then, do you see an issue with having the higher index tyres on the rear, which will have the increased payload, and keeping the lower index tyres on the front?

 

Karen

[Brian Kirby]

If your van has no spare wheel you have nothing to lose by doing as you propose. Then, when the fronts need changing, you can fit Michelins to them and bring all tyres the same specification.

 

However, if you have a spare and if, as Keith says, you get a flat at the rear, you won't be able to fit the spare to that axle and continue your journey as normal - because your increased rear axle load will fall outside its working range. I think your options would be to fit the spare and drive slowly (40MPH max) to the nearest tyre dealer, treating the spare in the same way as a "space saver" spare, or to call a breakdown service to transport your van to the nearest tyre dealer. Not ideal when you get the flat at a time when the tyre dealers are closed!

 

The 225/70 tyre will have a slightly larger rolling radius than the 215/70 which may mean your speedometer mis-reads. I don't know whether the Fiat speedometers can be switched for tyre size to correct this.

 

TBH, I think I'd try talking to either Continental's or Michelin's technical departments (or both) about tyres suitable for a 2,400kg rear axle load and see what the recommend. There should be a 225/70 112 Conti, although it is a plain vanilla C, rather than CP, tyre, but it looks as though it may not be suitable for 2,400kg. I think I'd also talk to Fiat about the speedometer issue with the 225/70 tyres on the front.

 

We can only give our opinions, whereas the manufacturers will give definitive answers based on their detailed knowledge of their own products.

[colin]

Point of order, whilst the Michelin tyres might have a name of 'camping' on them they are unlikely to be CP, as CP's in this size are unlikely to be above 109.

So why not get any tyre you like in 112. But I would change all 5.

Brian, it's 2240 not 2400

[Keithl]

OK I have just studied the Conti Technical brochure from 2013 - 2014 and can see why SV Tech are recommending the 225/70 R15 for use with an axle load of 2,400 kg.

 

That particular tyre size has a multiple load index (if that's the correct term). Its actual load index is 112/110R (115N).

 

This means it has a load rating of 112 (1,120 kg per tyre) at a speed index of R (106 mph) as a single wheel fitment, a load rating of 110 (1,060 kg per tyre) when one of a twin wheel fitment, again at speed index R OR a load index of 115 (1,215 kg per tyre) at a speed index of N (87 mph).

 

So, as long as Karen does not exceed 87 mph in her MH :D , she can safely use the 225/70 R15 C 112/110 (115N) tyres at an axle load of 2,400 kg.

 

I have taken this info for a 'C' tyre so it would be worth double checking that whatever tyres you do decide to purchase carry the 115N rating.

 

Keith.

[Karen0858]

Thanks Keith

 

Obviously not a simple issue, taking everyone's advice, I am going to email Continental and see what they recommend before making any decisions. We currently do have a spare but are intending to do without and go with TyreProtect (I know that's a controversial topic on forums). I will update when I get a response from Conti.

 

Thanks again for all the constructive advice, really helpful for us newbies.

 

Karen

[colin]

Keithl - 2017-07-25 8:33 PM

 

OK I have just studied the Conti Technical brochure from 2013 - 2014 and can see why SV Tech are recommending the 225/70 R15 for use with an axle load of 2,400 kg.

 

Am I going mad? First Brian now you say 2400, but I only see 2240 in OP.

[Keithl]

colin - 2017-07-25 9:14 PM

 

Keithl - 2017-07-25 8:33 PM

 

OK I have just studied the Conti Technical brochure from 2013 - 2014 and can see why SV Tech are recommending the 225/70 R15 for use with an axle load of 2,400 kg.

 

Am I going mad? First Brian now you say 2400, but I only see 2240 in OP.

 

Colin,

 

Sorry, I read 2,400 kg in Brian's post and never went back to the OP.

 

You are correct, Karen only wants to uprate to 2,240 kg according to her OP.

 

Sorry for adding to the confusion.

 

Keith.

[Billggski]

I have the same issue with rear axle load being marginal, I fitted 225 75 15 CP Michelin Agilis camping on the rear, left the 215's on the front and they will be due for replacement next year. The Agilis cp are quite soft and wearing much quicker than my conti camper tyres did. My spare is 215 so I do run the risk of having to use it like a space saver.

The difference in circumference is minimal and well within tolerances.

Air suspension would firm up the ride, but my Dethleffs on the ducato light chassis was rated at 3850kg without it.

[Derek Uzzell]

This has come up before and (as Karen has established) if ‘camping-car’ tyres (ie. “CP”-marked tyres) are wanted for 15”-diameter wheels and the tyres are to have a load-index above 109, the sole choice is to opt for Michelin’s “Agilis Camping” pattern in 225/70 R15CP 112Q specification.

 

On a front-wheel-drive vehicle, fitting the Michelin tyres to the rear wheels will not affect the speedometer. Although a 225/70 R15CP Michilin tyre should be expected to have a greater rolling circumference (RC) than a 215/70 R15CP Continental “VancoCamper”, this may not be so.

 

Continental’s tyre-related technical data are available on-line, but Michelin’s are not. I’m sure Michelin would advise on what the RC is for a 225/70 R15CP “Agilis Camping” tyre, but it’s unlikely to be more than 2% greater than the RC of a 215/70 R15CP “VancoCamper” and (as Billggski says) the difference should not matter in an ‘emergency’ situation where a rear axle has a 215/70 R15CP tyre on one end and a 225/70 R15CP tyre on the other end.

 

There are implications regarding using different-size tyres on the same axle (eg. the vehicle would fail the UK MOT test) but in terms of real-world safety it would be a helluva lot safer to have the 215/70 and 225/70 combination than have a standard-size tyre and a skinny space-saver.

 

As Karen’s Burstner has a spare wheel, it would be wise to retain it. Using a sealant like Tyre Protector is fine, but it won’t cope with major damage to a tyre.

 

If my motorhome had a spare wheel I would be very very reluctant to travel without it. I might choose to have sealant put in all the tyres, but there would need to be an overwhelmingly convincing reason not to carry the spare wheel.

 

A spare wheel + tyre weighs around 30kg and, if having uprated a motorhome’s rear-axle carrying capacity from 2000kg to 2240kg, it proved impracticable to travel legally with a 30kg spare-wheel onboard, I’d wonder about the validity of the uprating exercise. I could understand ditching the spare wheel if the space gained by doing so was absolutely critical, but I’m guessing that’s not the case here.

[Brian Kirby]

colin - 2017-07-25 7:42 PM

 

Point of order, whilst the Michelin tyres might have a name of 'camping' on them they are unlikely to be CP, as CP's in this size are unlikely to be above 109.

So why not get any tyre you like in 112. But I would change all 5.

Brian, it's 2240 not 2400

Apologies. Thanks Colin, you're right. Same applies though. Even at 2040 (the maximum permissible axle load for the proposed 225/70), the enhanced axle load will still be outside the operating range (2060kg max) for the 215/70 spare.

[Brian Kirby]

Derek Uzzell - 2017-07-26 9:15 AM.......................On a front-wheel-drive vehicle, fitting the Michelin tyres to the rear wheels will not affect the speedometer. Although a 225/70 R15CP Michilin tyre should be expected to have a greater rolling circumference (RC) than a 215/70 R15CP Continental “VancoCamper”, this may not be so.

.............................

Yes, wasn't sparklingly clear there, was I! ? :-) I meant (though didn't clarify), that this might be an issue after the 225s have been fitted onto the front wheels.

 

Our Transit based Hobby had a facility within the ECU to re-program the speedometer for a (limited) range of size tyres, presumably because different sized tyres were fitted to different Transit models that shared the same speedo. The tyre size was dealer adjustable via a computer link.

[Derek Uzzell]

‘Non-recreational’ X290 Ducatos wuth 15”-diameter wheels can have (as original equipment) 215/70 R15C 109 or 225/70 R15C 112 tyres, and I assume X290 Boxers/Relays and the earlier X250 vehicles have/had the same two 15”-wheel tyre choices.

 

In earlier discussions Steve928 has mentioned having swapped his X290 Peugeot Boxer-based Bailey motorhome’s original-equipment 215/70 R15CP Michelin “Agilis Camping” tyres for Falken 225/70 R15C tyres.

 

In his posting of 25 October 2016 10:08 AM here

 

http://forums.outandaboutlive.co.uk/forums/Motorhomes/Motorhome-Matters/Most-accurate-speedo-/45678/

 

Steve says that it is possible to produce an accurate speedometer reading with a suitable diagnostics tool.

 

As speedometers commonly over-read by a significant margin (10% is not that rare), if the RC of a 225/70 R15 tyre were around 2% more than that of a 215/70 R15 tyre, there's every chance that this wouid improve the accuracy of the vehicle’s speedometer. If the X290 optional 16”-diameter wheels with 225/75 R16 tyres were fitted instead of the 15”-wheels and 215/70 R15 (or 225/70 R15) tyres, this would increase the RC by about 9%, and speedometer under-reading would very likely result.

 

SVTech’s standard advice regarding weight-uprating a non-AL-KO chassis Ducato ‘light’ has been to move from 215/70 R15 tyres to 225/70 R15 ones and add ‘air assist’ to the rear suspension. I’ve not heard of this causing anybody problems, legal or technical.

[monique.hubrechtsgm]

Your burstner vehicle COC documents in the final state should include all variations of possiblble tyres and wheels with different off-sets. That should be adhered too. They are in the type approval. Increasing axle loads are not allowed if not approved by burstner including suspension mods. Same rules will be done by the belgian MOT. AND for sure you will get a new brake test including weight and exhaust emmision.Also your plates are not valid anymore in the uk. You have the car papers changed and insurance.

[Brian Kirby]

monique.hubrechts@gm - 2017-07-26 3:34 PM

 

Your burstner vehicle COC documents in the final state should include all variations of possiblble tyres and wheels with different off-sets. That should be adhered too. They are in the type approval. Increasing axle loads are not allowed if not approved by burstner including suspension mods. Same rules will be done by the belgian MOT. AND for sure you will get a new brake test including weight and exhaust emmision.Also your plates are not valid anymore in the uk. You have the car papers changed and insurance.

But, it doesn't work quite the same in UK, Monique. Suitably qualified auto engineers, as in this case, can authorise higher axle loads without consulting Fiat in each case. They can (and do) then issue a revised vehicle plate with the new axle loading shown. It is then for the owner to notify DVLA of the altered vehicle and axle loads, and obtain a revised registration document. The CoC is not further revised during this process. It is treated as a document that records only the condition in which the vehicle was Type Approved and first registered. Thereafter, it is the registration document that records notifiable changes.

[Karen0858]

Thanks again for all the constructive comments.

 

This is where I am at:

1. Continental - advise only option is to change brand or upsize tyres. They too refer to issues with speedo/odometer etc but as this is a rear change only, that does not concern me. They suggested I contact Fiat and Ducato for their comments and also pointed out I should advise my Insurer.

2. MIchelin - not really prepared to comment on mixing 225 and 215 width tyres either way, suggest I contact dealer direct.

3. SVTech - not tyre specialists but believe most of their customers stick with Continental Commercial tyres, that means going with a 225 width

4. Checked both Burstner and Fiat handbooks and the only option for tyres given is the 215, no choice.

 

Sent queries to both Fiat and Ducato, awaiting their replies.

 

I can't believe we are the only people in this situation but maybe others haven't queried is as much as I am.

 

I do appreciate at the comments so far, we are leaning toward just going ahead and fitting the wider tyres on the rear with the Michelin unless Fiat, Ducato or insurers issue a big fat NO.

 

If that happens, will have to go down the route of fitting a tow bar and getting a small trailer, all because we want to take our small motorbike in the garage!

[Brian Kirby]

Karen, have you checked that the bike doesn't exceed the load limit for the garage? There will be one, and you haven't yet said either way.

[Karen0858]

Hello Brian

 

The spec allows 200kg for rear garage and rear loading space. If we load the back as we would like to, we would have 2 e-bikes on rack totalling 56k, bike ramp 7.5, bike 78. I assume I should include gas bottles as the storage for them is also at rear so another 30kg. That takes the total to 173kg in round figures. You can see why we don't really want to carry the spare wheel.

 

I do wonder what they mean by "rear storage space" as we have cupboards in the back of the van plus the trauma heater is also fitted in the rear. Mus confess that I have not really considered weight of the boiler in this calculation or included clothes in cupboards.

 

Karen

[Keithl]

Karen,

 

One option might be to only take e-bikes OR motorbike. Then you could carry your spare wheel.

 

Also be aware that most breakdown services will not attend a puncture or tyre failure if you are not carrying a spare wheel unless the vehicle was specifically designed not to carry one. Then you must have a 'pump & Goo' style repair kit instead. I suggest you check your breakdown cover policy wording carefully (assuming you have breakdown cover?).

 

Keith.

[Karen0858]

Thanks Keith

 

Van spec is for get you home kit, spare wheel was an option. When we bought the van we asked the dealer to provide spare wheel. We do have breakdown cover but will check the small print on this subject.

 

As for cycle v motorbike, it's a battle of the sexes I am afraid. I prefer to cycle but hubby loves his bike! At present we decide what to take dependent on where we are going but inevitably, whatever we take, we always find ourselves missing the other.

 

Karen

[Billggski]

Just check the "goo" with your inflation kit. It has a very short "use by" date.