Apologies in advance for the ultimate in dull threads.
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Took car into garage to get 2 new front tyres. The existing 4 tyres were 225/40 ZR 18 92Y and they put 235/40 ZR 18 95Y on the front. So wider by 10mm and a different rating to the back ones.
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So Is this OK and also will it have any effect on driving, road noise, mpg etc.
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I know next to nothing about cars so any input useful. It’s a company car so didn’t get consulted about the change.
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Cheers

10mm would make no notable difference and seeing as most 40 series tyres don’t last two minutes it won’t be long before they’ll be getting changed again 😆

I would assume its a bit like some bike tyre manufacturers 2.35’s coming up like others 2.1’s etc. If they are different brands this may be an option tyre size for your vehicle and is not much differenr from the rears so I personally would not worry about it unless they start rubbing inner wheel arces on full lock as with some Volvo T5’s and Maxda MPS’s (and thats with the correct tyres on!)

you should also inform your insurance about the non standard tyre fitment , if you have an accident it would probably invalidate your insurance. they will use anything to wriggle out of a claim and a change in tyre size would be all the excuse they need.

What carslog said.

I would also check what the standard size is for your car as per handbook, it may be that they have fitted what is standard for the car.

It’s a company car so I’ll drop the leasing company an email when I’m back at work. They authorised them in the first place via their computer link system with Kwik-fit.

Will it have any effect on MPG?

Edit: standard size are the 225s, sticker inside car door with pressure settings says so. No idea what the 235s should be at.

235 will probably be an alternative listed in the owners handbook. Have a shoofti in it.

Probably the wrong tyres. Also note that the cirmumference of the tyres will be different to the old ones (not because of wear). The middle number (40 in your case) is not a measurement. Its a ratio of wall height as a %age of width. So a 235/40 will have a larger diameter than a 225/40. I suggest you check your handbook, if the tyres fitted are not listed then ask the garage to change them.

Your speedo will read roughly 1.3% slower than it would on 225 tyres.
I’m not exactly sure by how much, but the larger wheel diameter given by 235/40 will adversely affect mpg & acceleration. I doubt it’ll be noticeable though.

won’t effect mpg at all. ever so slightly higher geared so will run at a lower revs per ‘actual’ speed .

I run ‘much ‘bigger wheel/tyre combo on my truck, and fuel consumption actually improved on actual mileage and hardly changed at all on the (now slightly lower) dashboard mileage.

Much, much better off road grip, clearance and handling, and much smoother on road too..

Your ABS won’t be too happy, it relies on comparing wheel speeds and you don’t have wheels turning at the same speed to start with. And if you have a 4wd with a locking or semi-locking diff you could be putting strain on that.

Take it back, get them changed, or change the backs to match.

They have probably made a mistake in fitting 235’s.
Wider front tyres will give more grip,but,the most grip needs to be on the rear of any car.
Less grip on rear can lead to oversteer when approaching limits of adhesion.
Not as easy to control as understeer(less grip in front)
Also correct about insurance problems.
Take the vehicle back,and ask them to fit the correct size.

Normally if you go up 10 on the width you’d go down 5 on the profile.

I suspect it’s a Kwik-Fit mistake
Theve also fitted an extra load tyre rather a standard load but that is better than the over way around.

Out of interest which lease company does the vehicle belong to?

http://www.etyres.co.uk/tyre-size-calculator.htm

Cheers for all the responses folks, think I’ll give the lease company a ring on Wednesday and see what they say.

Not particularly happy with the idea of something non-standard and just wanted some ammunition in case they don’t care.

Car is through Leaseplan by the way. If it was my own car I would have knocked them back when they were fitted.

Insurance is our company’s own cover so it may affect that as well.

UPDATE (for anyone remotely interested)
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Went back to Kwik-fit today and told them the problem. They apologised and changed over to the right size without any questions.
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Thanks again for the advice. Singletrackworld truly is the first place to go for advice on any subject.

I think that is very wise, obviously a mistake on their part!

I had something similar with new rear tyres a couple of years ago – I only realised as my traction control kicked in much more frequently so I inspected the tyres more closely and noticed they were the wrong width.