If you are thinking of changing your car tyre size or are planning on buying a new wheel/tyre combination then you can use the flash tool below for a visual tyre size comparison of your stock wheel and tyre size versus your new wheel and tyre combination.

Got a comment or question regarding the current version of the tyre size calculator? Click here to leave a comment or ask a question.

Vesion 2 of the tyre size calculator is in development, if there’s anything you’d like to see in version 2 then please feel free to leave a comment here: Tyre Size Calculator V2: Wishlist.

## Why is this important?

Matching the combined wheel and tyre diameter is important as it will ensure your ride height and speedometer readings don’t change drastically. An example of this would be fitting 17″ wheels to a car that has 14″ wheels as standard, there are three main consequences:

- the ride height will change, the car body will be further from the ground.
- the top speed will increase slightly and the speedometer will under read.
- the car will accelerate slower.

Read on to see the reason for this in detail.

# Tyre Size Guide

## Ride Height

Take the default example in the flash tyre size calculator above, here we have a stock tyre size of 165/55R14 and a new tyre size of 215/45R17. There is a total difference of 8.82cm in the two wheel and tyre diameters, if we divide this by two we get a difference in radius of 4.41cm. If we ignore tyre pressures and the effects of adding larger, wider wheels to suspension geometry; then this is roughly how much higher the car will be from the ground.

## Speedometer

Then there’s the speedometer, a cars speed reading is usually taken from the transmission and is set based on a number of predefined constants. When you change your wheel and tyre combination you are taking one of these constants and making it variable. The speedometer does not know the new value and so continues to read based on the original wheel & tyre size. If you look at the above default example again you will see that with a 215/45R17 wheel and tyre combination there is a difference of 16.4% in the speedometer reading over the stock setup. As you can see, at 60mph your speedometer should actually be reading 69.9mph!

## Acceleration

If we fall back to the default example again, the 215/45R17 wheel and tyre combination has a larger overall diameter by 8.82cm. A larger diameter has a greater rotational inertia which requires more energy to accelerate. Or in other words: the bigger the wheel, the slower the acceleration.

It should be noted that putting a bigger wheel and tyre combination on your car *does not* reduce your cars power. Your cars power remains the same; however it takes more force to turn your car’s wheels resulting in slower acceleration.

## Tyre Width Equivalency Table

You may also find the following table of recommended tyre widths for given rim widths useful when changing your tyre width.

Rim width | Min tyre width | Ideal tyre width | Max tyre width |
---|---|---|---|

5 .0 inches | 155 mm | 165 ou 175 mm | 185 mm |

5.5 inches | 165 mm | 175 ou 185 mm | 195 mm |

6.0 inches | 175 mm | 185 ou 195 mm | 205 mm |

6.5 inches | 185 mm | 195 ou 205 mm | 215 mm |

7.0 inches | 195 mm | 205 ou 215 mm | 225 mm |

7.5 inches | 205 mm | 215 ou 225 mm | 235 mm |

8.0 inches | 215 mm | 225 ou 235 mm | 245 mm |

8.5 inches | 225 mm | 235 ou 245 mm | 255 mm |

9,0 inches | 235 mm | 245 ou 255 mm | 265 mm |

9.5 inches | 245 mm | 255 ou 265 mm | 275 mm |

10.0 inches | 255 mm | 265 or 275 mm | 285 mm |

10.5 inches | 265 mm | 275 or 285 mm | 295 mm |

11.0 inches | 275 mm | 285 or 295 mm | 305 mm |

11.5 inches | 285 mm | 295 or 305 mm | 315 mm |

12.0 inches | 295 mm | 305 or 315 mm | 325 mm |

12.5 inches | 305 mm | 315 or 325 mm | 335 mm |

I Have Honda City 2010 Manual. Company Installed tyre size is R15 175/65.. i want to change it coz v small tryes. If anyone can guide me. I want Good size tyre which doesnt make much affect to speed n fuel consumtion.

Hi, I have originally mounted 205/55/R16 tyres on alloy wheels on my Citroen C4 coupe. Wondering if I put 15″ steel wheels with 205/55/R15 winter tyres. Wondering will it affect the speedometer and accelaration readings?

It would put 195/65R15 tires on the 15″ steel wheels, they have about the same diameter as the 205/55R16, plus the narrower 195 tyres cut better through the snow. This way the speedometer and odometer are not affected. I use 195/65R15 winter tyres on my 2006 VW Jetta and 205/55R16 summer tyres.

Hi,

Am just enquiring if there is a tyre tread depth guide, for instance i recently purchased some new Pilot Sport 315/25/zr19 tyres at a staggering price,only to find the tyre tread depth wasnt very good,,

regards,,

Mr G Dodd…

I have currently have 4 x ford focus 205x55x16 wheels and would like to buy some ford alloys but the guy says they used to have 215x55x16 tyres on. Is it on to use my 205x55x16 tyres?

thanks….J

Your ‘rolling radius’ is in fact rolling circumference, quite an error!

Hi,I need your advice as I am intending to change the tyre size of my vw vento 1996 model with a factory fitted tyre size of 185/60-R14 to 185/70-R14 to increase the ground clearance.I hope I would not have a risk of the tyre hittin the wall of the tire well when I am with or without passenger of recoommended 4 person.Is this tyre size within volkswagen recommended specification of such car?

I have a 1998 Vento (Jetta here in Canada). I installed today a set of 185/70-R14 tires and they work and fit ok.

hi,i got vectra b 2.5 with factory fitted tyres 195/65/15 91H and planning to lower profile to 195/55/15 would there be a probs? what do u suggest?

Was searching for what is the widest tyre that would fit on a 9,5″x19 alloy for ages….

At last…. I found it, but i am disappointed. I wanted a 305/30/19 but i will have to compromise at a 285….

hi i have a 09 vw touareg and it currently has 275/45/20 tyres on, its a 9’x20 alloy and wanted to know if it would be ok if i put on a 295/40/20 tyre on, i want the fat rubber look!! 😀 thanks

hi i have chevrolet optra and my front tyre size is diffrent than the rear one that will harm my car or effect on the performance

Will a 215/40ZR17 fit my Peugeot 206 Turbo Diesel 2003 without any modifications or will it foul on full lock thanks WB

can i wear 175/65/15 tyres in 15*7 alloys in new honda city

Yes you can as tyre is flexible & will adjust to the larger wheel

tell me about mini tractor tyre

thanks, easy to calculate my new rim with suitable tyres…

i want to replace tyre and rim inmy car alto VXR suzuki

size is 165/65 R13 is it ok

I have 4 new 205 70R 15 can I use these on me 2009 corolla which has 195 65R 15 on now thanks

will a 275 80 15 fit on a rim that has a 245 60 15 already on it

No. You’ll have to take the old tyre off 1st or you’ll never get the 275 on! 😉

I ordered a new set of alloys and tyres, what is currently on it are 205 55 16 will changing them to 205 40 17 be ok? Thank you for your help.

Lorna

When replacing tyers is it better to choose less or greater speed results

Excellent website. Good work well done. I am thinking of replacing 245/55R19 with 255/55R19

Would this cause a lot of trouble?

Ur help is appericiated

Thanks

Veer

need to know the table of air pressure on tyre in tyre size to psi and kpa

My Honda City 2007 came with 165/80/13 tyres i want to put new tires/rims of 195/65/15

please guide me.

According to the tyre/rim comparison chart 255 is the widest tyre for an 8.5J rim. What is the risk of fitting 265×35? Rim is 18″ on rear of a 2002 E39 540i. Thanks. (Great website, very informative).

Hello, i’ve been searching everywhere on the internet for an answer to this question : What is the maximum acceptable increase in diameter for a tire, without causing problems to AWD the system? I’m thinking of switching from a 25,3 inch diameter (stock tires) to a 27,7 inch diameter (2,4 extra inches). Is that too much? I can live with a change in the speedo readings. Thanks !

im about to change my tyres on a 2006 tiida.original size was 185/65/15. Thinking of getting 205/60/15,or 205/55/15, or 205/50/15. Im also thinking of trying the 195 series. Which one of these tyre sizes will give me a more comfortable quiet ride. could you also recommend a brand

which did u get? and what’s your recommendation?

Hi,

Daft questions maybe but will larger effect the odometer reading.

Cheers

Stevie

Hi,

short answer, Yes.

With a larger radius the Speedo will show slower, and the Odometer will tick up slower, how much slower is governed by the percentage difference from the stock rubber.

Firstly, a radius is half of the diameter – most kids with Math at school will be able to tell you that. What you are refering to in you calculator as the “rolling radius” is actually the circumference of the wheel.

Secondly, Rolling Radius is the actual diameter of the wheel as it would be in a vehicle – in other words, the weight of the vehicle plays a role and it is definitely a lot less than the radius of the wheel as it is lying in your boot.

The calculations in your formula work out the circumference of the wheel, without taking the weight of the vehicle into account. Cute, and it will give you a good indication, but fairly useless if you require accurate results.

need to know ive got a v70 volvo its got 22#45#R17 i was wondering could i fit 205#55#R16 wheels .hopfully u can help

Can I fit 190/65R15 tyre for 185/65R15 rim size

Hi there

Just wondering why when going from a 275/30/R20 to 285/30/R20 does it increase the speedo by 0.9%? The overall circumference isn’t any greater or does it take in account camber?

Of course the circumference is greater. The “30” is an aspect ratio, that is the percentage of the width. A wider tyre therefore, with the same aspect ratio, will be taller giving it a larger diameter. “30” is not a measurement – it means that the side wall height is 30% of the width. Calculator is correct.

Hi, I have 225 40 zr17 and i want to change them to 225 35 zr17, will there be a noticeable difference?

Hi, if my OEM tyres are 215/45/18 and rims are 18 x 7″, can I use 225/40/18 tyres? What about 225/45/18 tyres? Thanks.

have got peugeot 306dt with non standard wheels and tyres need to know what should be on the car

Hi ihave 205 65 r15 tyers on 15″ 6j steel wheels and have bought 15″ 7j alloys will my tyers be ok to fit on new alloys. or do i need widder tyers. Does it matter if new wheels are slightly wider.

Many thanks.

Neil

There is a chart for that right over your comment…

Hi great tyre site ,I wander if you can help us mgb classic car owners ,i have 165,14 tyres fitted which are very skinny and dont provide much grip when cornering.what could you recommend as an up grade ie the widest tyre i could fit to a new 14 inch 5.5 inch wide minilite rim. Ive heard of 195s being fitted but are these to wide for the rim , and what profile would you recommend .

any help would be great.

Hi Andy,

I’ve included the tyre width equivalency table by pneus-online.co.uk that I mentioned a while back to the foot of the tyre size guide. If you refer to the table it suggests a maximum section width of 195mm. So while maybe not dangerously wide, I would agree that 195s are probably a bit too wide. Try some 175 or 185s on there if you want more tread on the road.

Hi

My car (Mazda cx 7 sport)tire is P235/60HR18

can I change it to P235/60HR17 103S?

CHANGES TO P235/65HR17 103S

Unless you’re reducing the size of your rim to 17″ from 18″ then categorically no. You cannot fit a smaller diameter tyre onto your 18″ rim.

I’m thinking of changing the size of my tyre from 185/65 R14 to 185/70 R14. Is this advisable? Will it leave any negative impact? Pls advised.

No major impact, the overall height of your wheel/tyre combination will increase by 18.5mm. Your ride may be a little softer.

I have a BMW 330D Tourer (2003) with 225/45/R17 on the front and 245/40/R17 on the rear. I need winter tyres and can get 225/60/R15 on alloys cheaply from a friend who had a BMW 325.

Rolling circumference is only 2.6% different to original front tyres.

Car only used for low speed, short distance trips in Switzerland without carrying heavy loads during the winter.

Is it safe to fit the 15″ wheels? Many thanks, Peter

So long as the offset and PCD are such that the wheels fit correctly I can’t see a problem. As long as you are aware of the speedo difference I expect it should be ok.

Ok, thanks for the reply , in this situation whch size will be better for this car ( Rover 400) , 195/55/15 or 205/55/15? I am looking at a table at this web site: http://www.tyresave.co.uk/choose.html. Thank you in advance.

BR

Stew

Hi Stew,

The ideal section width for a 7″ wide rim is 205 to 215mm. The 195mm tyre would fit but would be stretched and not give you much tyre on the road. I would suggest 205s tho.

Hi, I am going to change my rims and tyre siza and want to know if it is ok with the sizes. I have a Rover 400 and present size is 185/60/14. I got rims R15 7J and think of adding 195/55/15 tyres. I saw on calculator that difference is 3,1%. I want to know if this combination is ok to follow as I am trying to escape from too low profile tyre as my suspension will broke faster. Also sppedometer is not a problem as now is showing 7km mor then real speed on 100km/h. Thank you in advance.

The new tyre profile will result in a greater overall diameter of wheel & tyre but you’ll have a shorter sidewall. It’ll look better but there will be less sidewall flex, so if you felt the ride was harsh before it is likely to be moreso with the new tyre profile that you are looking at.

Will a change from 205/50/R15 to 195/55/R16 be OK.

I realise that the car will be a little higher off the ground which is fine, but will I have any problems due the the overall diameter being larger?

The obvious things to check would be for clearance in the wheel wells. You’ll have less of a ground contanct patch with those wheels tho so you may find the handling is compromised slightly.

I want to know if i can switch from 245/70R/16 to a 265/70R/16 on my jeep grand cherokee or if this will cause a drastic difference.

Sidewall height will increase, more sidewall flex and the tyres themselves will look a little more rounded on the rim due to the increased width but I don’t imagine it would be a huge problem. Unless you do offroading in which case it could make the tyres more susceptible to popping off the rims? I’m not a jeep/offroader person so as I’ve said before always consult you local tyre specialist before parting with your hard earned cash 😉

Please advise me on the following query.

I have a car with a converted wheel size from 195 65 R14 to 215 45 R17

Should this have any detrimental effect on the car?

Please write back direct on my email address above.

Hi Muhanned, the wheels will not be causing the power loss. While it is true that larger wheels have a greater rotational inertia and this affects acceleration… but it is still slight.

I would suggest the problem is more likely to be the engine, possibly fueling related as you could be running lean. Maybe the fuel pressure regulator, blocked fuel filter, knackered fuel pump or lambda sensor. If its air/fuel related then also check your MAF or MAP sensor.

I have a mitsubishi galant 2.0liter GLS 1999 with alloy wheeels size:195 65 R14.

I have just bought similar car 2001 with a converted alloy wheels size :215 45 R17.

I have checked this and ended up with small difference from the original size, something like 2cm.

Should this be ok or not??. please advise me as matter of urgency, as i am trying this car on the motorway, and seems to loose power after a speed of 70m/hr. Not sure if the wheel conversion has any thing to do with it??

Please reply to my private email listed above

Thanks

Muhanned

Your new tire is 2.7% bigger than the stock, and the limit is 3. For fuel consumption, generally speaking, the % of the new wheel total weight must be divided in 2 to get the effect on the fuel consumption.

So, if your new wheel is 20% heavier, you’ll need 10% more fuel for the same distance than the stock wheel.

I think your rolling radius values are in ‘mm’ when they are apparently shown to be in ‘cm’. Please check.

Hi Neeraj, the rolling radius label should actually read “circumference”. It was an oversight when I built this version of the calculator. I should probably just change it and make an incremental release rather than waiting till I finish the new version…

Can I replace 195/65/15 stock tires on my new honda civic with 205/65/15. What difference will it make on the fuel economy, suspension, height & acceleration??

Kamran & Haider,

You should be fine running 205’s instead of 195’s. The tyre wall will be a little taller giving you a slightly more comfortable ride but you’ll get more sidewall flex meaning handling during cornering is affected.

Although we’re talking 6.5mm difference in the sidewall height here so I doubt you’ll even notice the theoretical differences I have mentioned above.

Q:my corolla 2009 company tire is General Euro tyre 195/65 R15, may i replace that with Yokohama DB silent 205/65 R15?

i have a golf 4 motion with 8j on the fron and 10.5 on the rear.. i have 255/35/19 on the rear but need an a tyre for the front with the same raduis so not to wind my diff up and break it… cant get very big tyre on the front due to catchin…. can you please help

thanks

what happen if new Tyre change less diameter than old one? it is save fuel or what happen if in-contrast.