Ducato wheel size change - 15" to 16"

[sludgesurfer]

Posting this as some help to others wanting to make this change. Thanks to Colinm, Wildebus, exwindsurfer and others for the advice across various other threads.

I wanted more ground clearance. I spend a fair amount if time on rough ground and I was fed up knocking the daft grey and fresh water drain pipes off the underside.

I have a 2018 Autotrail on the light chassis. This can be specced from new with 15 or 16" wheels. Mine was an ex demo on 15"

I changed from 7 year old superdry Hammer 15" alloys with 215/70 R15 Michelin cross climate CP to MSW Van 48 16" with with 225/75 R16 Michelin cross climate with high pressure valves.
I got a new full size spare on a steel spare (also 225/75 R16)

My experience so far after 200 miles:

- I gained just under an inch of ground clearance
- Speedo was over-reading vs actual before. Its now spot on.
- Slight change in gearing. Cruises at lower revs on motorway. Spend a bit more time in lower gears on an incline but barely noticeable.
- No noticeable change in road noise
- No noticeable change in braking
- I called the insurers Devitt to notify them of the change. Initially they said it would be £50 + £30 "admin" because i'd iincrease the vehicle value and said they required locking nuts on the alloys. After I changed the wheels I called them back and they said they didn't need notified after all. I fitted locking nuts anyway.
- CHECK YOUR WHEEL STUD TORQUE after a wheel change. I checked the torque after 50 miles and one wheel had a couple of loose studs. Barely hand tight. After removing the wheel I found there was crap in the stud holes which prevented the studs seating properly. The shop should have picked this up imo. Cleaned and retorqued the studs and I've done another 150 miles with no issues. I marked the studs with tipex to check for rotation.
- The underslung carrier accepted the new spare fine. The winch locked off without issue. The carrier on the light chassis is clearly designed to take either.

All in all very happy.

Photos of old, new and the new spare in the carrier:

 

[wildebus]

Totally off-topic reply ... can't remember the last time I saw a Windsurfer! everyone seems to have switched to stand-up paddleboards now (used to like windsurfing never any good at it, but still enjoyed it )

Suggestion for your spare ... make sure the nuts are protected from dirt thrown up on the road and slacken anf retighten periodically. Only had one vehicle with an underslung wheel like that - a VW T5 - and it took an afternoon with some pretty energetic activity to loosen the securing nuts as they were stuck on so hard after probably a few years on being left on and untouched.

 

[trevskoda]

Put the nuts on the spare wheel with copper greese, im not a fan of wheels under cars/vans, better on ones bum.

 

[marchie]

Put the nuts on the spare wheel with copper greese, im not a fan of wheels under cars/vans, better on ones bum.View attachment 146460

Whose idea was it to leave the spare wheel in the doorway, just inviting some unsuspecting person to trip over it? ....

I don't describe the spare as 'underslung', because it would be mounted with care and attention, if I *had* a spare, that is; undrslung sounds so untidy ...

Steve

 

[davep10000]

Posting this as some help to others wanting to make this change. Thanks to Colinm, Wildebus, exwindsurfer and others for the advice across various other threads.

I wanted more ground clearance. I spend a fair amount if time on rough ground and I was fed up knocking the daft grey and fresh water drain pipes off the underside.

I have a 2018 Autotrail on the light chassis. This can be specced from new with 15 or 16" wheels. Mine was an ex demo on 15"

I changed from 7 year old superdry Hammer 15" alloys with 215/70 R15 Michelin cross climate CP to MSW Van 48 16" with with 225/75 R16 Michelin cross climate with high pressure valves.
I got a new full size spare on a steel spare (also 225/75 R16)

My experience so far after 200 miles:

- I gained just under an inch of ground clearance
- Speedo was over-reading vs actual before. Its now spot on.
- Slight change in gearing. Cruises at lower revs on motorway. Spend a bit more time in lower gears on an incline but barely noticeable.
- No noticeable change in road noise
- No noticeable change in braking
- I called the insurers Devitt to notify them of the change. Initially they said it would be £50 + £30 "admin" because i'd iincrease the vehicle value and said they required locking nuts on the alloys. After I changed the wheels I called them back and they said they didn't need notified after all. I fitted locking nuts anyway.
- CHECK YOUR WHEEL STUD TORQUE after a wheel change. I checked the torque after 50 miles and one wheel had a couple of loose studs. Barely hand tight. After removing the wheel I found there was crap in the stud holes which prevented the studs seating properly. The shop should have picked this up imo. Cleaned and retorqued the studs and I've done another 150 miles with no issues. I marked the studs with tipex to check for rotation.
- The underslung carrier accepted the new spare fine. The winch locked off without issue. The carrier on the light chassis is clearly designed to take either.

All in all very happy.

Photos of old, new and the new spare in the carrier:

View attachment 146454

View attachment 146458View attachment 146459
View attachment 146456

When I did exactly the same change, as you say the speedo is now exactly correct, however, the odometer is now around 7% under reading, so any mpg readings off the trip computer are also out... Is yours the same?

 

[sludgesurfer]

.

 

[sludgesurfer]

Totally off-topic reply ... can't remember the last time I saw a Windsurfer! everyone seems to have switched to stand-up paddleboards now (used to like windsurfing never any good at it, but still enjoyed it )

Yes, we seem to be a dying breed. With foiling, winging and kite surfing now popular, there's fewer windsurfing.

Suggestion for your spare ... make sure the nuts are protected from dirt thrown up on the road and slacken anf retighten periodically.

Noted. The winch is secured with an end plate passed through the wheel and secured with a plastic coated retaining bolt so you dont need wheel studs. Its very exposed to the elements. I thought about wrapping it in shrink wrap or using a spare protector but give you need a hole in the top for the winch wire I figured it'd fill with water/salt and do more harm than good. Whilst the spare steel wasn't in great nick after 7 years, the winch mechanism looked ok after a tidy up and re grease

Put the nuts on the spare wheel with copper greese, im not a fan of wheels under cars/vans, better on ones bum.View attachment 146460

My bum has a bike rack and ladder for the roof. Plus i dont want another 15 odd kg hanging off the door hinges. Underneath is the best of a bad bunch for me.

 

[sludgesurfer]

When I did exactly the same change, as you say the speedo is now exactly correct, however, the odometer is now around 7% under reading, so any mpg readings off the trip computer are also out... Is yours the same?

Good point. I should have mentioned this. I was getting around 29mpg on the trip computer on the 15". I now show around 27 mpg on the 16". Ive not done enough miles to really know whether the odometer is now incorrect.

I'd assumed that the odometer would also be correct post-change and the mpg would now also be correct but if you're saying the odometer is wrong and the mpg is based on the odometer, then the mpg would appear to be under reading by around 7%.

In short, yes, im seeing the same as you.

 

[davep10000]

Good point. I should have mentioned this. I was getting around 29mpg on the trip computer on the 15". I now show around 27 mpg on the 16". Ive not done enough miles to really know whether the odometer is now incorrect.

I'd assumed that the odometer would also be correct post-change and the mpg would now also be correct but if you're saying the odometer is wrong and the mpg is based on the odometer, then the mpg would appear to be under reading by around 7%.

In short, yes, im seeing the same as you.

I am not sure how to sort it out, presumably the BCM (body control module)? may need re-programming to enter the new rolling diameter...

 

[r4dent]

Totally off-topic reply ... can't remember the last time I saw a Windsurfer!

Happy memories of my only attempt at windsurfing.

Back in the 80s I hired one for a day in the South of France.

I managed to stay upright on the thing but couldn't manage to change direction.
To change direction I adopted a technique
1) Fall off
2) Manhandle the stupid thing to point in the right direction
3) Climb back on
4) Sail in the new direction.

I had just completed stage 1 of a turn when I noticed another windsurfer headed straight at me.
She was a beautiful vision. Long blonde hair; slim tanned body; and topless.
As she maintained her high speed approach I was impressed by her obvious skill and fully anticipated that she would pull a tight turn at the last minute.
Alas, she was no better at turning than I was and hit my board amidships.
She flew through the air and landed directly on top of me.
We struggled to the surface together and she delivered the memorable words that remain in my head over 40 years later..
"Aw £$%^, I don't know how to work these bloody things" in a thick Brummie accent.

The magic of the moment was lost forever.

 

[wildebus]

I went Windsurfing in a big lake in Wakefield where my friends sister was an instructor.
Like your situation, couldn't turn the bugger and I ended up ramming the shore on the opposite side and getting towed back

 

[colinm]

Funny enough just been sorting out some old Tee shirts and came across my UKBSA and Brogbough race team shirts.

 

[exwindsurfer]

I change for 15in to 16in about 10 years ago I also found out the offset on my alloys have giving me a 3in wider track.I am running 225 x 75 x 16in tyres .

 

[Drover]

Has anyone got put numbers for 16inch rims that give the same track as 15inch.
I.will need new tyres shortly and am tempted to go 16