Changing from 15" to 16" wheels (1 Viewer)

[TheTwoOfUs]

Having seen a couple of motorhomes which have upped their wheels from 15" to 16" I thought about doing the same to give a better ride, better fuel economy, increased ground clearance for the tow bar and improved accuracy with the speedo. So I contacted Dethleffs technical dept and asked the question if this was possible? No was the reply as they had not homologated the bigger wheels. Which then begs the question, are there motorhomes out there which have the wrong size wheels on them (according to the letter of the law) and therefore have invalidated insurance? Or is there a loophole?

 

[chaser]

As far as I know the studs are different so won't fit.

 

[Lenny HB]

As far as I know the studs are different so won't fit.

Also I think different hub, discs, calipers etc., would be a very expensive exersise.

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[Flatlander]

@Lenny HB and @chaser Sorry guys, you are wrong. Fiats 15" wheels have a pcd of 5x118. Although early 16" Fiat wheels do have a 5x130 pcd, most after 2013 have the same 5x118 as the 15-inchers do. Therefore, its a straight swap.

Havng said that, its also a pointless swap, as there are no tangible benefits. Depending on the tyres used it could (stressing the word could) also be illegal. Therefore, insurance could be invalidated. There is a loophole, but its expensive.

 

[Howard H]

I have done it recently not for any really technical reasons other than in my opinion the 15 inch wheels looked to small for the van and as the 6 month newer models of the same van where coming out with 16 inch alloys I thought why not . The wheels I got where a a straight swop and not only look a lot better the ride is nicer and speedo now reads correctly .

 

[TheTwoOfUs]

Two of the reasons I wanted to swap.

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[Howard H]

That's what they look like now

Two of the reasons I wanted to swap.

 

[TheTwoOfUs]

I think I might have to contact Comfort for their view on this.

 

[gus-lopez]

The speedo is not meant to be accurate. By law it has to 'overread' by a minimum 7% . This prevents the defence, when caught speeding, that the speedo is 'incorrect' & blamed on the manufacturer.

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[Richard n Ann]

I wouldn't have alloy wheels, they are heavier, weaker and after a few years they corrode, look terrible, and the tyres go down. Been there done it got the badge

I will now put my tin hat on.

 

[Derbyshire wanderer]

The changing to a bigger wheel is a modification and your insurer would expect to be informed.
As above if not homologated, they also may say no.

 

[tonyidle]

The speedo is not meant to be accurate. By law it has to 'overread' by a minimum 7% . This prevents the defence, when caught speeding, that the speedo is 'incorrect' & blamed on the manufacturer.

Not in the UK as far as I'm aware. It must not under read but can be up to 10% fast. GPS speedos are legal too.

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[dave newell]

The speedo is not meant to be accurate. By law it has to 'overread' by a minimum 7% . This prevents the defence, when caught speeding, that the speedo is 'incorrect' & blamed on the manufacturer.

Sorry but this is incorrect. The speed o can read over by up to 10% but must not read lower than true speed.

D.

 

[tonyidle]

The changing to a bigger wheel is a modification and your insurer would expect to be informed.
As above if not homologated, they also may say no.

No wheel different to that supplied by the manufacturer is homologated. This has not and does not prevent a massive industry in aftermarket wheels offering any size you want for any vehicle on the road. Inform your insurers - they won't be even slightly interested.

 

[Lenny HB]

Just to be pedantic speedo can read over by up to 10% + 2mph but must not read lower than true speed, for the life of the vehicle.

Interestingly Fiat speedos are always near the top tolerance with mph dials but only a few% over with kmh dials.

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[Derbyshire wanderer]

No wheel different to that supplied by the manufacturer is homologated. This has not and does not prevent a massive industry in aftermarket wheels offering any size you want for any vehicle on the road. Inform your insurers - they won't be even slightly interested.

I agree that the wheel is not homolagated but the standard wheel/s would have been part of the Type Approval process so anything not to the same specifications would be classed as a modification.
In my experience insurance companies are quite quick to add a surcharge to most modifications and would have no hesitation in the event of a claim in using non disclosure as a reason to reduce or refuse a claim.
Oversized or undersized wheels would make differences to the steering geometry and braking efficiency and possibly the suspension (depending on the unsprung weight difference).
Plenty of people do it and will never have a problem but you never know what may happen down the road.

 

[Ex-caravantugger]

@Lenny HB and @chaser Sorry guys, you are wrong. Fiats 15" wheels have a pcd of 5x118. Although early 16" Fiat wheels do have a 5x130 pcd, most after 2013 have the same 5x118 as the 15-inchers do. Therefore, its a straight swap.

Havng said that, its also a pointless swap, as there are no tangible benefits. Depending on the tyres used it could (stressing the word could) also be illegal. Therefore, insurance could be invalidated. There is a loophole, but its expensive.

Agree too. My new Fiat has 16" wheels and tyres though the centre bore is 71.1cm instead of a standard 16" wheel which is 78.1cm. My pcd is also 5x118.

 

[Nirvanauk]

I wouldn't have alloy wheels, they are heavier, weaker and after a few years they corrode, look terrible, and the tyres go down. Been there done it got the badge

I will now put my tin hat on.

No need for a tin hat I agree with you 100%

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[Minxy]

Why not fit air assisted suspension instead on the rear, this will make a LOT of difference to the ride, comfort and importantly allow you to raise and lower the rear when you need to 'lift' the tow bar higher (eg for going on/off ferries), it will also be cheaper.

 

[DL42846]

I have air assisted rear suspension which keeps the back end up and gives me a good ground clearance. I run on 15" wheels which work out fine. My MH is 2.99 mt high. A 16 inch wheel I think would take my van to just over 3 mt's high and would put me into a class 3 on the toll roads here.

 

[Richard n Ann]

I have air assisted rear suspension which keeps the back end up and gives me a good ground clearance. I run on 15" wheels which work out fine. My MH is 2.99 mt high. A 16 inch wheel I think would take my van to just over 3 mt's high and would put me into a class 3 on the toll roads here.
View attachment 192624

Surely if you put bigger wheels on they have a lower profile tyre to keep the gearbox ratios the same? Otherwise acceleration would be slower, rpm/speed ratio lower and speedo wrong. Would also effect MPG if you're having to change down into 5th up every hill.

I once put big Town & Country tyres on a Vauxhall Viva and it was even slower (I know almost unimaginable! )

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[Flatlander]

I checked up about this earlier.

Lets assume the original tyres are 215/75x15. The owner then fits 16" wheels, and fits them with 225/75x16 tyres. That, under current legislation, is illegal unless the vehicle in question is type approved for that size of tyre.

 

[tonyidle]

I checked up about this earlier.

Lets assume the original tyres are 215/75x15. The owner then fits 16" wheels, and fits them with 225/75x16 tyres. That, under current legislation, is illegal unless the vehicle in question is type approved for that size of tyre.

Can you provide a link to that legislation? There's an entire industry devoted to encouraging vehicle owners to break such a law.

 

[Flatlander]

Can you provide a link to that legislation? There's an entire industry devoted to encouraging vehicle owners to break such a law.

Sorry, no. I got the information from an old friend that has just retired from the Police force. He was an Inspector with the traffic division, so I assume it to be correct.

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[Lenny HB]

On 15" wheels Camping tyres are 70 profile on 16" wheels they are 75, work that one out.

 

[Flatlander]

On 15" wheels Camping tyres are 70 profile on 16" wheels they are 75, work that one out.

Easy. Illegal!

 

[Howard H]

Easy. Illegal!

Not wanting a argument or anything but just wondering why you say that , the new Benimar 294 are coming out with 16inch alloy wheels 225/75 marquis told me there is no difference to the running gear and safeguard insurance did not seem that bothered when I told them ,so resepectfully why would they be illegal ?

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[MikeD]

You can check them out here. But as said earlier the 16" wheel has a bigger centre hole so would not fit.

https://www.wheel-size.com/size/fiat/ducato/2018/

ps: you can click on the year and the details change to suit.

 

[Howard H]

I bought 16inch wheels with the correct bolt holes and centres and new bolts to fit my van .

 

[Deleted member 29692]

I wouldn't have alloy wheels, they are heavier, weaker and after a few years they corrode, look terrible, and the tyres go down. Been there done it got the badge

I will now put my tin hat on.

Of course they aren't heavier.

The whole point of alloy wheels is that they are lighter.

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