16 inch wheels fitted on Fiat and Peugeot Van conversions

[Steve928]

Robinhood - 2014-11-10 4:57 PM

 

Steve928 - 2014-11-10 4:48 PM

 

I think that the 15"/light and the 16"heavy/Maxi actually have the same ride height;

 

........Fiat data for the X290 in "standard" format shows both loading and overall height as 15mm higher for the Maxi over and above the "light" chassis (for a similar configuration).

 

Ah OK, thanks for that, clearly I haven't detected that small difference.

 

That 15mm is less than the c. 24mm coming from the increase in tyre radius light->maxi though so the suspension components must compensate in some way.

Plus it's under half the c. 31mm lift that the 16" + 225mm tyres give to a light chassis. In addition to the gearing question already raised, wouldn't a 31mm suspension lift be detrimental to a vehicle's handling?

[Derek Uzzell]

Increasing the ride height by choosing the 16” wheel option should indeed prove detrimental to an X290’s handling, with the higher centre of gravity resulting in a greater tendency to roll. Not sure, though, how much that would actually matter with a commercial X290 vehicle or an X290-based motorhome, except perhaps in extremis.

 

As far as road-holding is concerned the bigger tyre will have a bigger footprint, so might provide improved grip. On the other hand, Fiat’s X290 handbook advises a 5.5bar inflation pressure for 225/75 R16CP front tyres (rather than 5.0bar for 215/70 R15CP fronts) which is likely to be overkill on a ‘light’ X290-based motorhome with 16” wheels.

 

I can see why 16” alloy wheels might be attractive cosmetically for motorhomes based on a ‘light’ X290 chassis, but I don’t see where the gain is as far as 16” steel wheels are concerned.

[Billggski]

I suppose the answer will come when someone drives the 15" and 16" variants. The speedo and gear changes will reveal what has been done. In the old days you just changed the rear diff as I have just done on my Land Rover (front and rear!) but I expect that changing a cog in the gearbox is possible.

The x290's are primarily white vans, so it could be a way of increasing the payload of a light chassis. The specifications indicate that there is now an overlap between maxi and light vans.

[pepe63xnotuse]

From a purely aesthetic viewpoint, I've allows thought that X250 sized vans look better with bigger(16") wheels. The X250 we had, although only a tiddler, looked daft on 15" wheels....and some of the large Merc Sprinter panel/delivery vans you see about look really "over-bodied" for their wheel size.

 

I really don't like this trend for modern (fwd) vans to be all but scraping their under bellies on the carriage way... :-S

[Muswell]

Derek Uzzell - 2014-11-11 12:13 PM

 

As far as road-holding is concerned the bigger tyre will have a bigger footprint, so might provide improved grip.

 

I don't think that's correct. Isn't the tyre footprint just the axle load divided by the tyre pressure?

[Derek Uzzell]

Muswell

 

A 225/75 R16CP tyre is wider and has a greater circumference than a 215/70 R15CP tyre. If both were inflated to a pressure appropriate to the same load, more of the larger tyre’s tread should be in contact with the road surface (ie. it should have a bigger footprint).

 

Plainly this doesn’t take into account the comparative ’stiffness’ of each tyre’s construction, which might cause a larger, heavier-built tyre with a higher load-index to deform less than the smaller one, but there’s no doubt that 225mm is wider than 215mm.

 

If you’d prefer “...the bigger tyre SHOULD have a bigger footprint..” that’s fine by me.

[Derek Uzzell]

Billggski - 2014-11-11 12:57 PM

 

I suppose the answer will come when someone drives the 15" and 16" variants. The speedo and gear changes will reveal what has been done. In the old days you just changed the rear diff as I have just done on my Land Rover (front and rear!) but I expect that changing a cog in the gearbox is possible.

The x290's are primarily white vans, so it could be a way of increasing the payload of a light chassis. The specifications indicate that there is now an overlap between maxi and light vans.

 

Some motorhome manufacturers (eg. Rapido) offer an overall-weight upgrade for ‘light chassis’ X290-based models from the standard 3500kg maximum to 3650kg, but there’s no indication that this is linked to an obligatory increase in wheel/tyre dimensions or that there is any financial penalty for opting for a 3650kg weight maximum.

 

Fiat’s technical and equipment specifications for Goods Transport X290s are available on-line, with ‘light’ versions being 3500kg or less and ‘heavy’ versions being 4005kg or higher. Choosing 3650kg instead of 3500kg does not seem to be an option for ‘white vans’. There’s no overlap weight-wise - ‘lights’ stop at 3500kg, while ‘heavies’ start at 4005kg - though there’s now an overlap regarding wheel and tyre sizes of course.

 

This does not prevent ‘heavy’ X290s being downplated to 3500kg and several PVC builders do this to make their products more attractive to buyers who just have the basic ‘car’ driving-licence entitlement. But these vehicles already have 16” wheels and the appropriate gearing/speedometer-calibration to match.

 

An X290 16” steel wheel + tyre will be heavier than a 15” steel wheel + tyre and, if the bigger wheels/tyres are fitted to a ‘light’ X290, this is bound to impact negatively on that vehicle’s payload. Even if alloy 16” wheels were chosen instead of 15” steel wheels, it’s likely that any potential overall weight-saving resulting from the alloy wheels will be offset by the extra weight of the bigger tyres. However the 16” wheel option is played, I can’t see it improving payload.

 

Studying Fiat’s X290 specifications for 2.3litre motors/transmissions indicates that there 4 possible final-drive ratios, two for manual gearboxes and two for Comfort-Matic gearboxes. But the only final-drive ratio that would reduce the increase in overall gearing caused by going to 16” wheels would be the ratio fitted to the manual transmission used with a Maxi chassis. However, even if a gearbox with a Maxi-chassis final-drive ratio were used with the 16” wheel + 225/75 R16CP tyre option, there would still be a gearing difference between a ‘light’ motorhome model with 16” wheels and an otherwise identical model with 15” wheels.

 

I don’t know what the premium is for opting for 16” steel wheels for a ‘light’ X290 white van, but Rapido’s price for the Fiat 16” alloy wheels option is over £600. The idea of having alloy wheels on a motorhome leaves me cold and I couldn’t care less about the standard 15” wheels looking undersize in the wheel-arches. But, if I were considering opting for 16” wheels, I’d certainly want to know about the gearing.

[Robinhood]

Derek Uzzell - 2014-11-11 3:04 PM

 

Fiat’s technical and equipment specifications for Goods Transport X290s are available on-line, with ‘light’ versions being 3500kg or less and ‘heavy’ versions being 4005kg or higher. Choosing 3650kg instead of 3500kg does not seem to be an option for ‘white vans’. There’s no overlap weight-wise - ‘lights’ stop at 3500kg, while ‘heavies’ start at 4005kg - though there’s now an overlap regarding wheel and tyre sizes of course.

 

 

...it may be a matter of interpretation, but I don't agree with the above.

 

The "light" X290 can be had in 3000kg, 3300kg, and 3500kg versions, depending on load capacity.

 

The "heavy" X290 (which I would equate to "maxi") can be had in 3500kg (factory available option) and 4005kg versions.

 

There is thus a cross-over at 3500kg, and the underpinnings of a 3500kg Maxi are different to those for a 3500kg "light" van.

 

The tare weight of the 4005kg Maxi is different to that of the 3500kg Maxi, (which itself is different to the 3500kg "light"), so the difference is not simply one of downplating.

 

Derek Uzzell - 2014-11-11 3:04 PM

 

I don’t know what the premium is for opting for 16” steel wheels for a ‘light’ X290 white van...

 

 

In Germany €178.50 incl VAT.

 

 

 

[Derek Uzzell]

Oh dear...

 

You are quite right - on a like-for-like basis a 3500kg Maxi’s tare-weight is evidently 40kg more than that of a 3500kg non-Maxi, while a 4005kg Maxi’s tare-weight is 45kg more than that of a 3500kg Maxi. So a 4005kg Maxi’s tare-weight will be 85kg more than that of a 3500kg non-Maxi. It’s likely then that Maxi-based PVCs with a 3500kg overall weight limit are not ‘downplated’ as such but (as you say) technically different from the 4005kg version.

[Steve928]

Derek Uzzell - 2014-11-11 3:04 PM

Some motorhome manufacturers (eg. Rapido) offer an overall-weight upgrade for ‘light chassis’ X290-based models from the standard 3500kg maximum to 3650kg, but there’s no indication that this is linked to an obligatory increase in wheel/tyre dimensions or that there is any financial penalty for opting for a 3650kg weight maximum.

 

The Autotrail vans that I looked over provide confirmation that the X290 light chassis plated at 3650kg can come from Fiat with either wheel size. Both the Apache (16") and Imala (15") were plated originally at 3650kg prior to down-plating (reversible) by AT's second-stage conversion.

[Robinhood]

Steve928 - 2014-11-11 4:15 PM

 

The Autotrail vans that I looked over provide confirmation that the X290 light chassis plated at 3650kg can come from Fiat with either wheel size. Both the Apache (16") and Imala (15") were plated originally at 3650kg prior to down-plating (reversible) by AT's second-stage conversion.

 

...yes, I've noted that on Autotrails.

[Steve928]

Wanting to check that my eyes weren't deceiving me (see posts above) I knew I'd be passing the dealers today so popped in with a tape measure to check those ride heights. New X2/90s sitting on a level showroom floor, checked both sides and 2 vehicles per type.

 

Ride heights at front from floor vertically through hub centre to wheelarch:

 

- Maxi/heavy, 16" wheels = 800mm

- Light, 15 wheels = 808mm

- Light, 16 wheels = 840mm

 

So the light+16" combination really is the high one as it appears to the eye.

Also, while a Maxi may be higher overall than a light+15" (as stated in Fiat's technical data) that extra height isn't generated at the front end - reason perhaps why people consider them to sit nose-down and embark upon fitting Goldschmidt springs to raise the front end.

 

Personally, if I were interested in a van on the light chassis with 16" wheels, I'd want a good test drive to check that the car-like handling for which the X2/50 is praised hasn't been compromised.

[Billggski]

Interesting, as the tyre height difference is only 20cm.

(682cm divided by 3.142 = 217cm, as against 744cm. = 237cm)

 

[Derek Uzzell]

It’s not easy to calculate exactly the increase in ride-height resulting from an increase in wheel and tyre sizes, particularly as the situation in this case seems to be that X290-based motorhomes have Continental tyres on 15” wheels and Michelins on 16” wheels.

 

However, relying on Continental’s data alone, fitting 225/75 R16CP tyres instead of 215/70 R15CP tyres would produce an increase in tyre static radius of 27mm (with a +/-2% variation).

 

Continental defines the static radius as

 

“...the distance between the wheel centre and the ground contact patch under max. load at the recommended tyre pressure."

 

Obviously those conditions won’t obtain for a motorhome in a dealer’s showroom, but the 27mm calculation is pretty close to Steve’s measured 32mm ride-height increase and, if the bigger tyre were inflated higher than the smaller, an extra 5mm could easily result.