Motorhome wheels

[Erichele]

Can anybody tell me if I can just buy and swap my 15” wheels on my Autotrail Imala 734 2019 and upgrade them to 16”

 

 

 

 

[Derek Uzzell]

These links advise on 15” and 16” Ducato wheels

 

https://www.tyremen.co.uk/guide/which-chassis-do-i-have-light-or-maxi

 

https://www.tyremen.co.uk/guide/i-have-15%E2%80%9D-wheels-my-motorhome-can-i-upgrade-16%E2%80%9D-wheels-and-tyres

 

The significant thing is that the hubs of a Ducato ‘light’ chassis (that has 15” wheels as standard) are different to the hubs of a Ducato ‘heavy’ chassis (that has 16” wheels as standard).

 

So if you want to change the 15” wheels of your Imala (which - as it has 15” wheels - is built on a Ducato ‘light’ chassis) you will need to obtain 16” wheels suitable for the ‘light chassis’ hubs. Such wheels are available in steel or alloy, but it won’t be a cheap swap and, of course, you’d need different tyres too.

 

 

[2GB Racing]

As Derek states the PCD ( distance between wheel bolt centres ) is different between the 15" /16" I have just gone through the process of obtaining a steel 16" 130 mm pcd wheel with correct Centre bore ( hole ) as a spare for my van which has 16" alloys. Also check that your current wheel bolts are the correct angle cone possible 60 deg for other wheels or you may need to change the full bolt set. Also you will need the correct J which is the offset / inset possible stamped inside your current wheels

[Conrad]

I suspect this would count as a vehicle modification, and be grabbed as an excuse for your insurance company not to pay out.

[Derek Uzzell]

Another “Tyremen” link goes into technical detail regarding Ducato motorhome wheels’ stud pattern (Pitch Circle Diameter), offset, etc.

 

https://www.tyremen.co.uk/guide/fiat-ducato-motorhome-wheels

 

The Ducato Owner Handbook descibes the standard 15” steel wheel as 6Jx 15 - H2 (where H2 equals the number of internal ‘humps’ across the width of the rim. The PCD for wheels to fit the hubs of the ‘light’ Ducato chassis is 5x118.

 

It perhaps needs adding that swapping from 15” to 16” wheels and fitting 225/75 R16 tyres (which is the size that’s usually used when a ‘light chassis’ Ducato is factory-fitted with 16” wheels) will increase the motorhome’s overall gearing significantly - which may not be a good thing if the vehicle has the basic 2.3litre 130 motor. It will also affect the speedometer reading, but that might be less of an issue.

 

(The motorhome’s insurance provider should definitely be told that ‘attractive to thieves’ alloy wheels have been fitted.)

 

[mikefitz]

I have used this Oponeo for wheels to fit the light chassis,

 

https://www.oponeo.ie/steel-wheels-finder.

 

If the 16 inch wheels are fitted with slightly lower profile 215/65 R16 tyres of the correct load rating (109 or higher) the error in displayed speed and increase in gearing is less than 1%.

 

There are light chassis motor homes marketed with 225/75 R16 tyres, as a factory option, I suspect these will be fitted with the optional gearbox ratios ( there are two final drive ratios available on the Fiat gearbox).

 

There is a considerable list of build options available from Fiat for the motor home converters.

 

There are 16 inch alloy wheels available with the correct load rating,

 

https://www.oponeo.ie/alloy-wheels-finder

 

Note with the wider alloys the offset will slightly different to the steel wheels to maintain the same clearance to suspension parts.

 

There is a useful on line calculator that indicates the difference between current and proposed wheel/tyre.

 

Link to Will they fit

 

Mike

 

(Edit - Link shortened to fit page width)

[Derek Uzzell]

mikefitz - 2020-04-03 8:59 PM

 

...There are light chassis motor homes marketed with 225/75 R16 tyres, as a factory option, I suspect these will be fitted with the optional gearbox ratios ( there are two final drive ratios available on the Fiat gearbox)...

 

Mike

 

I asked the technical representative on the Fiat stand at the NEC show about the gearing and was told that, when the optional 16”-diameter wheels with 225/75 R16 tyres were fitted to a Ducato ‘light’ chassis, the gear ratios were not altered. In fact, I asked him at two different NEC shows - the first time he said that he wasn’t sure but thought the ratios were not altered and the 2nd time he confirmed that, when he had checked, this was indeed the case.

 

The Tyreman website advises that, if the 15” wheels and 215/70 R15CP 'camping-car 'tyres normally fitted as standard to Ducato-based coachbuilt motorhomes are replaced with 16” wheels and CP-marked tyres, the 225/65 R16CP specification increases the overall gearing by 2.4%.

 

This subject was discussed here when Ducato X290 models were first introduced and subsequently. The eventual (forum) conclusion was that that, when the 16”-diameter wheels option were chosen as a factory option for a ‘light’ chassis, the vehicle’s speedometer accuracy was software-adjusted to match but there was nothing to suggest that the gearing was altered. As I’ve said previously, the overall gearing of my 2015 Rapido (‘light’ Ducato chassis, 15” wheels, 150 motor) is on the low side - which I quite like - and a 7th gear to provide more relaxed motorway cruising would not come amiss. The 150 motor seems powerful enough to cope with a 8%-9% overall gearing increase, but I’m not sure that would be true for the 130 powerplant. Me, I’d rather have the flexibility that the present gearing offers.

 

If Eric chooses to replace his 2019 Auto-Trail Imala 724’s 15” wheels with 16” ones, this will be a ‘user retro-fit’ decision and won’t change his motorhome’s original gear ratios, motor, or reset the speedometer’s software link to tyre-size. As you’ve said, fitting 215/65 R16C tyres would hardly alter the Imala’s overall gearing and speedometer readout (though I think CP-marked tyres are not marketed in that size).

 

A set of four suitable new alloy wheels and tyres would (with fitting) likely cost around £1000. Some of that expenditure could be offset by flogging the current wheels/tyres, but it’s still expensive for what’s really just a cosmetic exercise.

 

(I’ve scraped two of my Rapido’s silver plastic wheel trims manoeuvring the motorhome at home. This doesn’t much concern me and (even if it did) I could obtain a couple of new trims for about £50. If the Rapido had alloy wheels, scraping them would really grieve me.)

[Steve928]

mikefitz - 2020-04-03 8:59 PM

 

There is a useful on line calculator that indicates the difference between current and proposed wheel/tyre.

 

Link to Will they fit

 

Mike

 

That's a great tool, thanks. Although the other calculations such as rolling circumference or ride height gain are easily done I spent a good deal of time with pen and paper trying to work out differences to what they refer to as 'poke' when changing offset and rim width. This tool does that for you in a flash.

 

16" aftermarket alloys in the original ET68 offset and 6" width are rare and there's a far greater choice in 6.5" width. ET68 isn't that common either and many online retailers will bring up the much more common ET50/6.5"in their list of compatible wheels. Although they may well fit under the arches the tool shows that track will widen by almost 2" which personally is the last thing I'd want on an already extra-wide-track motorhome's rear axle.