It’ll be fine.
The use of the 17" whees and tyres from a 2 litre MK4 will increase the gearing by 2.5% due to the tyre sizes used.
Therefore the speedometer will under state the speed the car is traveling at as the 1.5 litre cars uses a different geared speedometer to the 2 litre.
The fuel consumption may be a touch better but the odometer will under state the mileage.
The accelaration will be a touch slower.
The car may require you to change down sooner on low throttle.
Will it make a difference to every day driving, only you will know that.
Mazda UK have sent a note to all Mazda UK dealers advisng them against doing the change.
It is unlikly that the regional serious crime squad will be after you but you may well be reported on Crimewatch!!!
The difference is 1.6mph. It is not something you are ever going to know.
The main variance is not speed but the wheel and tyre are heavier and so will have a marginal effect if you bother to notice that stuff. Since, if you change these in the show room you won’t have a comparisons, you will be fine.
Listen to what Nick says - he knows, respect his knowledge.
as the speedo is designed to read slow it should be fine
But don’t forget to tell your insurers of the change.
i must inform the insurance company as well? that i didn’t know.
but i was aware that i have to change the car documents mainly because of the emission of pollutants. let’s hope it is aproved.
Isn’t the ND 4 stud fixing and the NC 5 stud fixing.
Ignore me, I miss read the op.
Yes - you must inform the insurance company.
Change the documents? Why?
The DVLA and the insurer will be aware of the documentation issued with the car, and to them. Change of wheel size is not noted, nor do you; or are allowed to change the documents. Both know the emissions rating, so you don’t need to tell them what they already know.
Me - I have a lot of respect for Drumtochty, he seems to have inside knowledge which indicates to me he was a former mechanic, and may still be. Changing wheel size upwards is something I would never do, from a practical point of view - the wheels and tyres are more expensive, and asking a dealer to exchange them from 16" to 17" is not going to be a straight exchange, or they will be out of pocket. Also, in light of what Drumtochty says, the dealer may refuse, if they have been advised not to do this. And - do they have spares in stock? They aren’t going to pull the wheels off a 2L and swop them for the 16"'s, putting both cars out of wack.
My car came with 16" wheels, after some scary moments I changed them (at my cost) for 15"'s, - grip is better and ‘seat of the pants’ driving assured. Large diameter wheels have rubber bands for tyres, and sideways grip deteriorates drastically, so smaller is better, not the other way round. I’m not saying drop to 15"'s, but don’t go up to 17"'s. It depend on how you drive, if sedately then you’ll be safe enough, drive the car as it was intended to be driven and you too will have some scary moments. (You may have some anyway, even with the 16’s!)
As for speedos designed to read slow? Since when? Granted there used to be a 10% variance allowed but that could mean either way, not just slow. Mine seems accurate enough - tested against GPS indicated speed across the range.
Nick says “The difference is 1.6mph” - but at what speed? the actual percentage difference applies across the full speed range of the car, so a percentage difference at 30 is greater at 70, regardless of what the speedo says.
It’s your choice, but it wouldn’t be mine.
The amount of scaremongering that goes on on forums never fails to amaze me.
I was going to write a long answer, but 2.3% theoretical diameter variation is 2.3% across the whole speed range which is 1.6mph at 60mph, or 0.8mph at 30. That is of course assuming that the tyres are perfectly to size, I have never seen two brands that are the same overall diameter yet, and that they run at perfect pressures with no variation for hot or cold weather, speed and load all of which will actually affect the rolling diameter. Tyres wear by over 2% across their life, a 16" tyre is 1% over size and the 17" tyre 1% under size would see a 17" set smaller than the 16" after less than 1mm of tread wear. Let your tyre pressure drop by a couple of PSI and you are already there.
You will be fine.
Don’t worry about getting the wheels from Mazda either, you will be able to get a free set of 17" from all the 2L MK3’s and MK4’s that will be in ditches because their 45 profile tyres don’t grip.
"You will be fine.
Don’t worry about getting the wheels from Mazda either, you will be able to get a free set of 17" from all the 2L MK3’s and MK4’s that will be in ditches because their 45 profile tyres don’t grip."
Sorry Nick - I assume this was intended as sarcasm, but you just shot yourself in the foot! - - - - -
I’m not offering any opinion either way here, but for interest, the NC has (IIRC) a programmable parameter in the PCM that allows the tire size to be input if it is changed. The ND, as far as I am aware does not. This makes me think that although your average Joe will not notice any difference by fitting different size wheels, the car’s ECU may be affected in some way.
it may just be the cars with DSC that have the option to programme the tyre size, I’ll have a check next time I’m around one. Mazda must have felt the need to put that option in on the NC, where bigger wheels were offered.
i fully accept that people do change wheel and tyre sizes, probably with out updating the PCM with no noticeable adverse effects.
I didn’t think anyone was shooting anything Gerry. I thought the OP wanted advice not Daily Mirror headlines. 