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

[Deleted member 29692]

He was an Inspector with the traffic division, so I assume it to be correct.

Knowing quite a few serving policemen I'd assume the opposite

 

[Minxy]

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

It is the percentage of the width of the tyre, not a 'mm' measurement ...

http://www.bridgestonetyrecentre.co.nz/tyres/how-to-read-your-tyre-size/

Example: 215/60R15

• 215 is the width of the tyre in millimetres.
• 60 is the aspect ratio or tyre profile.
• R means it is radial construction.
• 15 is the diameter of the wheel rim in inches.

What's a tyre's profile?
This relates to the depth of the sidewall (the wall at the side of the tyre). The profile is expressed as a percentage of the tyre's width. Eg. Our 215/60R15 tyre has a profile or sidewall that is 60% of the 215mm (width). A low profile tyre is generally 50% or below, down to as little as 30% with ultra low profile tyres. Higher performance vehicles are usually fitted with tyres that have lower profiles.

While low profile tyres give you greater control and better handling on corners, they can give a slightly harder ride. Also, going to a lower profile on the same size wheels will alter your speedometer reading so you'll need to fix that up before you hit the road. Talk to us and we can help you get the right fitment.​

 

[peterc10]

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.

I am not sure that is right, and if it is several of the cars we have owned over the years were and are illegal, as is my existing motorhome. I always check my speedos against the satnav figures, which are generally accurate to within 1% if you are travelling at a steady speed on a straight level section of road. My motorhome speedo reads about 5% high, my present car is about 3% high and the wife's car is pretty well spot on.

From memory I believe the range of accuracy required is 0% to +10%. That means it cannot read under the true speed but can read up to 10% over. This range is needed because of the inherent inaccuracy of any speedo given that the calculation is based upon knowing the effective outer diameter of the tyre when in contact with the road, which depends upon all sorts of variables for any one model such as wheel size, tyre size and make, tyre wear, tyre pressure and temperature.

Edit - Bugger Dave Newell beat me to it.

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[Lenny HB]

It is the percentage of the width of the tyre, not a 'mm' measurement ...

I may be dumb but I'm not that dumb. Nowhere did I mention mm, you are reading things into my post that I never said.

 

[DL42846]

I'm getting confused here, which is not difficult to do these days. I run a Land Rover Defender which seem to have a range of different wheel and tyre sizes for them. Some people run them on 15" some on 16" and some on 17" wheels. Now tyres range form a load of different sizes, from 235 or 225 or 255 or 285 x 75 or 85 or 55 or 50 x 15 or 16 or 17 and they are all legal and yes the speedo does get effected by the different tyre sizes

 

[Minxy]

I may be dumb but I'm not that dumb. Nowhere did I mention mm, you are reading things into my post that I never said.

I never said you HAD mentioned mm, but its an obvious assumption for those who don't know how tyres are coded, hence my posting the info.

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[Richard n Ann]

Of course they aren't heavier.

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

I've never weighed any but I read it somewhere a few years ago. Racing wheels will be lighter of course, but styled alloys can be significantly heavier than steel depending on the design.

 

[Lenny HB]

On Hymers 15" wheels the Alloys are 4kg lighter but with 16" wheels they are 4kg heavier.

 

[peterc10]

On Hymers 15" wheels the Alloys are 4kg lighter but with 16" wheels they are 4kg heavier.

Yes .... but. The 15" alloys so save 4kg compared with the 15" steel. But, according to Hymer, the 16" steels add 16kg to the 15" steels but the 16" alloys only add 4kg to the 15" steels.

So the 16" alloys are 12kg lighter than the 16"" steels, or so they say!

Must add this was for the 2015 models!

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[Lenny HB]

Yes .... but. The 15" alloys so save 4kg compared with the 15" steel. But, according to Hymer, the 16" steels add 16kg to the 15" steels but the 16" alloys only add 4kg to the 15" steels.

So the 16" alloys are 12kg lighter than the 16"" steels, or so they say!

Must add this was for the 2015 models!

Confusing ain't it.

 

[peterc10]

Confusing ain't it.

Yup ......

 

[two]

On Hymers 15" wheels the Alloys are 4kg lighter but with 16" wheels they are 4kg heavier.

I think that's an error in their printed information (one of many).

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[Lenny HB]

I think that's an error in their printed information (one of many).

I think Peter pointed it out correctly the weights are based on 15" steel wheel so 16 alloy are 4kg heavier than 15" steel but lighter than 16" steel.

 

[Minxy]

Yes .... but. The 15" alloys so save 4kg compared with the 15" steel. But, according to Hymer, the 16" steels add 16kg to the 15" steels but the 16" alloys only add 4kg to the 15" steels.

So the 16" alloys are 12kg lighter than the 16"" steels, or so they say!

Must add this was for the 2015 models!

Is this another IQ question? My head hurts!

 

[Hettie's Crew]

After reading all that I think we'll stick with our 15inch alloys, adding 112 index wider tyres, unless that's illegal too.

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[two]

I think Peter pointed it out correctly the weights are based on 15" steel wheel so 16 alloy are 4kg heavier than 15" steel but lighter than 16" steel.

Yes, maybe I misunderstood that bit of the spec when I read it.

 

[two]

As each of the numbers gets bigger, the size of the wheel does too, and the speed indicated by the speedo (which simply measures wheel revolutions) will be become lower.

For a 215/70R15 wheel I assume the following:

The ‘15’ is the diameter of the wheel from rim to rim in inches.

The ‘215’ is the width of the rim in millimetres (why mix units?).

The ‘70’ is the amount of tyre protruding from the rim, measured as a percentage of the rim width.​

Put these together and you can calculate the (unworn) circumference of the wheel. Things like loading, pressure and temperature may also affect the rolling circumference.

The radius of a 215/70R15 wheel is half the diameter of the rim, plus the amount of tyre around the outside
= 15x25.4/2 + 215x70/100 = 190.5 + 150.5 or 341mm. So its circumference is (2 x pi x radius) = 2x(22/7)x341
= 2143mm (2.14 metres).

Similarly, the circumference of a 225/75R16 wheel becomes 2.34 metres, a difference of about 9% (or 20cm per revolution) and challenging the tolerance of the issued speedo.

It may just be that manufacturers adjust the speedo to suit the size of wheel provided but I doubt they touch the transmission. I’d stick with the smaller wheels for more torque and to be easier to remove. I don’t think the other benefits would be noticeable, other than thinking you’re going faster and so avoiding the chance of a ticket.

 

[138go]

...

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[138go]

It may just be that manufacturers adjust the speedo to suit the size of wheel provided but I doubt they touch the transmission. I’d stick with the smaller wheels for more torque and to be easier to remove. I don’t think the other benefits would be noticeable, other than thinking you’re going faster and so avoiding the chance of a ticket.

Think you might find that the final drive is different on the Maxi Chassis
To the Standard Chassis. Maxi Chassis have the bigger wheels and the unrated load.

 

[Hettie's Crew]

Put these together and you can calculate the (unworn) circumference of the wheel.

Or you could just look at Continentals data sheet, it's in there.

 

[gus-lopez]

Far easier here, Wheel & tyre size is on the technical log book. If another wheel/tyre size is homologated then that will also be on the sheet under "Observations" Anything different is illegal & will fail the mot.

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[wiljoy]

Is everything going to be so illegal we cannot pass wind without being risk assessed.

 

[Richard n Ann]

YESSS!

 

[Richard n Ann]

Is everything going to be so illegal we cannot pass wind without being risk assessed.

YESSS!

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[two]

No wonder we have to pay so much for an MOT

 

[Yorick]

Maybe you should just change the left ones to see if you like it ?

 

[joka250]

Tyre sizes are as follows, 215 is the nominal width of the tyre, 70 is the height of the sidewall expressed as a percentage of the nominal width and 15 is the radius of the wheel. The width of the wheel will be expressed in inches, probably 6inch or 7 inch. The wheel width is imho rarely the same as the tyres nominal width. All tyres are measured off the wheel.

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[duane0001]

I have gone from 16" to 17" on my sprinter, I have slightly increased the diameter of the tyres to fill the arches better and ride pesky pot holes, its around a better vehicle for it

 

[duane0001]

Here it is, with AT tyres because getting stuck in fields is no fun

 

[Phillybarbour]

There are 15” and 16”wheels for the light chassis.

The Maxi Chassis has 16” wheels.

The 16” light and 16” Maxi wheels are NOT the same and do not cross fit as the bolt positions (PCD) are different.

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