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 |
CAN YOU PUT 195/60R 15 TYRES ON A 205/55 r16 RIM?
YOU REALISE THAT THE “R15″ REPRESENTS A 15″ RADIAL, AND “R16″ A 16″ RIGHT?
Of course NOT !
Was a bit confused to start with, then realised that your “rolling radius” should read circumference! Overall though, VERY HANDY. Many thanks for making it available.
Thanks, this is valuable information!
I currently own a 2006 VW Golf TDI and it has 195/65r15 on it and i have to do a drive up in northern canada and need studded tires. I have a set but they are 175/60R14 would you recommend using them?
If so how much would it effect my gas mileage?
Thank You
Even though some of the facts are true theorectically. I defer to some extent based on the type of tires used, the actual grip of the tires, the surface, the change in the weight of the rims compared to the original rims and other factors.
How do you calculate the effect on odometer reading of different tyre sizes?
It’s based on a Ratio of the original Wheel Size vs the New Wheel size. Obviously if your new wheel it larger you will travel further in the same time per rotation (By a small %)
i have a 97 f150, factorty tire is 235 70 16,can i place 265 70 16
using the calculator above I changed some wheels & tyres from 235/45 r17 to 215/55 r16 which should have been approx the same rolling radius , but on measuring the actual wheels & tyres there appears to be a big diffrenece 202cm for the 215 tyres(which is what the calculator says) but 207cm for the 235 tyre , can anyone explain why?
Were you comparing worn 235′s with new 215′s ?. That could make about 10mm or more difference. Also are the new and old tyres of same make/tread pattern, if they are different that could have an effect.
I realy like the fact that the dimensions in the calculator are given in metric (cm and/or mm). The wheel I am looking at for this discussion is a 215/50×17. What does Rolling Radius mean exactly? (I know exactly what the term radius means). I would imagine that Rolling Radius means the effective radius of the wheel when fitted to a vehicle and driving. However, a Rolling Radius of 203.20cm (2032mm or 2.032m) as given in the caculator is out of the question. What probably is meant is a Rolling Radius of 203.20 mm. But then, is the Rolling Radius reduced that dramatically compared to half of the Total Diameter (i.e. 203.20mm compared to 0.5 x 646.8mm = 323.4mm) when installed? Please let me know – thank you.
@siegfried
The “rolling radius” means actually the circumference of the wheel, that is Diameter*PI. Do the math to see the match. What is not mentionned here is the fact that a wheel is compressed by the load and the rolling radius is not the calculated one, but the real radius = ground-axle. This is logic, is as if the wheel is sturdy (no deformation on the ground contact point) but with smaller diameter. This is one of the reasons for wearing the tire tread, compression when rolling, the other is friction. So, when the wheel makes a complete rotation, the distance on the ground is not the theoretical one, but smaller. Make a test: make a sign on the spare tire in the contact point with a marker, roll it on the ground for a complete rotation and measure the distance. Do the same with one of the car’s wheels, push the car and measure. You will see the difference.
I have a Mustang that was purchased new with 235/55 R17 wheels. I am repalacing the wheels and the installer wants to install 235/50 R17 wheels. I calculate this will change the height of the tire by approx. 1/2 inch. Other than the height difference are there any other impacts i should consider before making this change. Should I just stick with the orginally specd tire?
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Hey guys i managed to get my hands on some Avantgarde M310′s which is the same style as VMR V710 but lighter i bought them in Hyper silver staggered Fitment is 5×120 19×8.5 et40/ 19×9.5 et35. Now ive been told they’ll go straight on to my coupe no problem.
Is this fitment correct? for my E46 318ci ZHP 2004. Will this offset rub against my arches i really cont want to do any fender mods which brings me on to my next point can i put on 255/35/19 rear and 235/40/19 front without to much stretch or safety risks? what would you guys recommend. Also if i get a larger sidewall will it make the ride less bumpy? sorry for the questions just new to wheel setups. thanks
Bought a hyundai and it currently has 225/45 16′s but says online the manufacturer would have put 205/40 16′s can i swap them between the 2?
can i fit 17 inch alloys to a citreon c3 2006 with a tyre size of 205/40/17 or 225/45/17 which is best comfort wise
the 205 tyre has a side wall depth of about 80mm, the 225 tyre over 100mm, the 225/45 combination will provide a smoother ride (you may need to read up on road noise / reviews of individual brands etc…) but a ‘smoother ride’ will translate to wallowing / less resposive shen you’re on twisty A roads…
i have palio 1.3 multijet tyre size 165/80/R13 but am not happy with that, what size can i put in 13rim
I have a 2010 challenger and want to know if the stock 20×9 rim would accept a 295 35 20 tire, the stock tire is 255 45 20
Is there any difference to the rolling diameter of the wheel/tyre if you were to fit the same tyres e.g. 245/40 R18 to a 9J rim wheel, rather than the original 8J rim wheel?
Yes, the sidewall would be stretched a on the 9J. As the sidewall stretches it reduces the height of the sidewall. I could add this to the calculator showing the effect at a really basic level, but it would be very inaccurate due to different tyre constructions and rubber compounds acting differently.
would having a spacesaver with a rim size slightly smaller or larger than my R15 wheels on my Honda Jazz be a problem ?
I have a Jazz with 175/R15 wheels would a spacesaver of 14 or 16 instead of 15 Rim make any difference ?
Can I fit tyres with maximum width to rims instead of the ideal width? Will there be any adverse effect / performance decrease / risk? Please help.
Is there any adverse effect / performance decrease / risk in fitting tyres to rims with maximum width instead of the ideal width?
citreon c3 2006 model with standard steel wheels 185/60/15 want to up grade what best option to ,15 alloys or 16 inch alloys and whats the best depth tyre for them the 15 and 16 as dont want to feel the road too much if you could tell me the sizes available to me for the 15 and 16 inch alloys without any arch or turning problems thanks
if we change the tire so that total diameter is changed, the distance between oddometer vs real distance will be different or not?
Yes, the distance on the odometer and the speed on the speedometer will be different.
hi i have ford focus and it 195/65/15tyres on, would like to fit 17 inch rims and tyres
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