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 |
Hi
Can I change my BMW 745i 245/55R17 W102 to 245/45R17′s ?? as there is a huge price difference.
Many Thanks
Rich Wood
Hi. I have a 2009 vw polo 1.4tdi with 195/55 r15. I want to put 195/65 r15 on but the advice on this and other sites suggests this would be a bad idea. Would changing to 65 r15s have a dramatic affect on acceleration and subsequently the mpg? would I be better off with manufacturers recommended size?
cheers bruce.
hi ihave ml350 4matic and have same stock size 19in wheels and iam planing to put wald 20x9front and 20x10rear what tire should i put in honor to read my tpms and esp thanks
Hi, what a useful tool. Only nit picking! you mean rolling circumference, not radius as illustrated don’t you? 3.14159 x dia, so for each revolution of the wheel the vehicle will travel that circumferential length / distance and hence the effect on the speedo reading.
All the best
MG
the caculator tells the diff. in the speed at 30 and 60, but how do u know how it effects the odometer and the fuel mileage readout on the dash?
Hi there,i am in doubt-on my SUV oem tires are 265/60R18,could i put winter 245/65 R18 on it.Rims are 8×18 ET53,vehicle Mercedes GL320cdi
Thank’s in advance
I have a 2004 Jeep Grand Cherokee and currently have 225/75/16 tires installed. I was giving a a complete set of Blizzak but their size are
235/60/16 it wider and about 1″ shorter can I use these tires on my truck or will is throw everything off?
Thanks for your help.
By the way the tires giving to me are brand new haven’t even seen snow yet
what size of tyre do i put on a 2002 Audi A6 1.9 TDi saloon
One of the opening statements about wheel sizes and speedometer readings seems to be incorrect. Take the Rover 800, these can be fitted with 14″, 15″, 16″ or 17″ wheels and tyres. As the wheel size increases the tyres height decreases, simple!
Surely there is an error with the coding for your tyre size calculator app. Plug in different tyre widths for a wheel with the same rim radius and profile (size) and according to your widget the rolling radius changes – and by considerable amounts. Eh?!
Of course it does. The profile indicates the tyre wall height as a % of the width, so increasing the width but leaving the profile increases the diameter and therefore the circumference, and vice versa.
Yup, that’s because the tyre profile (35, 45, 50 and so on) is a certain proportion of the tyre width (235, 245, 255 etc). So the same 19″ rim could have different width tyres on it.
20% (a purely hypothetical figure) of 255 is more than 20% of 235. That means that the tyre wall on a 255/35 is higher than on a 255/35. Same profile but the height of the wall, and therefore the diameter of the tyre and the rolling radius is therefore greater.
Hi can i change my 245/50 R18 tyres to, 245/45 R18′s on my BMW 730D??
pretty close, very slightly undersized, but not too bad, 255/45 R18 would be a slight improvement, most importantly you’ll have a lot more choice and scope to save a bit of money
hi, is 7″ (width of wheel) the same as 7J
yes, the metal wheel rim width is 7 inches on a ’7J’ tyre – the letter designates the design on bead on the inside of the rim that grips the sidewall of the tyre, your tyre width ought to be slightly fatter – they ought to bulge out a bit, 225mm, 235mm etc rather than fit perfectly (215mm)
I HAVE AN 03 NISSAN 350Z THE WHEEL WIDTH IS 8 IN. CAN I PUT A 215 45 17 ON THE FRONT AND RUN 245 45 17 ON THE REAR ITS JUST FOR THE SNOW SEASON I FOUND SOME REALLY CHEAP TIRES LET ME KNOW THANKS.
AND THE CAR IS SUPPOSE TO HAVE A STAGGERED FIT THANKS AGAIN.
I have a grand cherokee 2008 with 245 60 18s and am thinking of buying 285 75 16 – will this fit? will it destroy handling?
HI I have a 2011 Santa Fe its original wheel size is 235/65 R17 can I put winter tires and rims at 215/70 R16?
Can I use 195/60/R15 tires with 15″ rim instad of 205/55/R16 installed on 16″ and what is effect on vehicle height.
I have a Citroen Berlingo XTR with 215/55/16 rims. Can I put my old Michelin Alpin 205/55/16 tyres on?
Thanks,
Brian
NO PROBLEM CHIEF
Hi there, I have a VW Touareg with stock 20inch rims and currently have hankook ventus all seasons 275/40R20 106V. I want to get new tires with more side profile eg 275/60R20 instead of 275/40R20. Would this cause any adverse affect to the handling of the car?
your tuareg it’s aready a very slow car : with those tyres you want to put on it will be embarassing for you when an honda fit 1.4 will leave you on dust.dont go more than 275 45 20 your car will piss you of.
YOU CANNOT DO THAT CAUSE OF ABS AND TRACTION CONTROL SYSTEM IF U WANT TO CHANGE THE TIRE PROFILE YOU GOT TO CHANGE THE RIM SIZE EXEMPLE YOU HAVE 275/40R20 YOU COULD PUT 245/55R18 AND HE DOESNT AFFECT YOUR ABS AND TRACTION CONTROL SYSTEM YOU COULD NOT IF U STAY WITH THE SAME RIM SORRY BODY
My SAAB is fitted with 225/55 R17 tyres. Is it safe to fit 225/45 R17 winter tyres?
AT 120 KPH YOU GONNA ROLL AT ENV 117 KPH ITS GOOD BUT NOT PERFECT
Your rolling radius calculation is incorrect and it also has incorrect units. It should be in mm, cm is too big. Somehow your speed delta comes out correctly… Maybe it is actually rolling circumference you have listed instead of rolling radius?? Just trying to help…
rolling circumference is exactly what is meant dude, just bad terminology
I have my stock tire and wheel in my Toyota VIOS: 205/45/R17 and planning to replace it with R18 or R19. Please give me some advice. Thanks!
franklin
Hi, I have a Mazda 2 1.3 active. The tyres that i have on the car now is 175/65/14 but would like to chage to 17″ rims and tyres. any sugestions?
thank you…
205/40R17 WITH 7.5 INCH WHEEL
hi i have 1996 chevy beretta can i put 245 45 16 rear wheels ?
Great post! This is important when you are buying rims for your car as well. Making sure that you have the right size can save you a lot of time and money.
hi, I have the following on my car, 225/40/18 front and 255/35/18 on rears, both runflats. Can I put 225/45/18 on front and 255/40/18 on the rears in runflats?
I SUGGEST TO U TO STAY WITH THE SAME SIZE BECAUSE YOUR RIM AS SPECIFIED WITH THIS KIND OF TIRE IF U DONT WANT PROBLEM BUY THE SAME SIZE
Hi – I’ve got 275/55/17 summer tyres on 8.5″ rims and want to change to 245/70/17 winter tyres. Speedo reading 10% low at moment, so using these ‘taller’ tyres should help? Can anyone see any problems? Will tese tyres fit on the rims?
hi ihave a peugeot 206 the tyre size at the moment is 175/60/14 i want to change them to alloys (ford alloys) size 195/60/15 does any one know if these will fit an what effects they might have thanks
As far as a suggestion for the v2, I would love to see a side by side comparison with a end view to compare tread widths.
The tyres on my car are 225/50/ZR/17′s I would like to change to winter tires size 225/40/R18 will they fit and what will the outcome be in terms of acceltation/braking etc/
2007 VANDEN PLAS WITH 255/40 HR 19. BECAUSE OF SPEED BUMPS IN AREA I NEED MORE GROUND CLEARANCE. CAN I CHANGE WHEELS AND/OR TYRES?
I currently have 165/70-13 on my ford fiesta mk4 i would like to increase to 195/45-15 is this recommended or can someone give me a better idea in order to have a 15inch alloys as im uncertain? thanks
it’s a pretty close match for maintaining speedo accuracy (the only better would be 200/45/15 – just try finding tyres for that size!) and a 15″ rich with 8cm sidewall should still give a reasonable ride
i have a land rover freelander with standard wheels (2005 model) and looking to buy 20 inch rims. what size tyres do i need, and would they fit? what measurements do i need to consider?
thnaks for your time.
kody.
there’s a sticker – usually inside the drivers side door shut – that tells you what wheel / tyre sizes are approved by manufacturers, and it tells you what pressure to use with weight loads etc… briefly if you are buying bigger rims you will need a tyre with a smaller profile (the second number) to maintain the same circumference, and therefore accuracy of your speedo
Hi, i drove a SsyangYong Kyron and the factory fitted tyre size is 255/60/18. Can i change to a smaller width and lower tyre but maintaining the rim of 18″? Say 245/50/18. What will be the difference?
you will e going slower than your speedometer reads, greater acceleration however a loss of fuel economy on motorway journeys
Hi can i put 235/45 ZR17 tyres onto alloy wheels that currently have 215/40 ZR17 tyres on them? If so is there much difference in handling?
Thanks
Yes, the 235/45 have both a greater width and profile, your speed reading will be more than indicated on the speedo. If your wheel width is less than 7.5” they will be a bit of a squeze. You should also check that the new tyres will clear your arches & suspension as they are larger overall. The change will make little difference to handeling, if they are low quality tyres you are fitting it could even be worse!
hi i have hyundai i20 185/65/r15 can i upgrade to 205/17/45 help me please
i presume you’re intending to buy a complete new set of wheels? you do realise the old rims won’t fit the proposed tyres… yes, you can change them, but the speedo will be inaccurate
better choice would be 225 / 45 / 17
I current have Dunlup AT22 Grandtrekkers 272/65R17 on a Nissan Patrol. I have been given a 2nd spare f9or a long trip, it’s a Coupers Sport HP 265/70R16. Are they campatible?
No, one is designed for a 16 inch dia rim , one for a 17 inch rim… you will not be able to fit your freebie tyre onto the rims you have, even if it comes with it’s own wheel there is a 5cm difference in the rolling radius, that would make the car awkward to drive if just fitted to one wheel
An indication of the tyre suspension comfort level help my decision making re changing tyre and rim sizes.
try honestjohn.co.uk he seems to pay quite a lot of attention to road noise when offering advice about tyre choice
Hello.
I have a car named TOYOTA vitz. i want to change the tyres. Please guide me which size of Tyre will be suitable for my car. eg.175R13 or 185R13 (GT Radial).
Thanks.
Shahzad
I have a vw golf one of the rear tyre is 195/65 R15 91T, the other rear tyre is 195/65 R15 91H, the front tyre is 195/65 R15 91H and the other front tyre is 195/65 R15 95T. Would this be fine for an MOT pass?
Hi there i have an 2001 astra ts with factory tires of 195/60/15 and i wanted to upgrade to 215/45/18 would they fit on my car? and would they have a massive effect on driving quality ??
Hello Im now using tyre 205/40/17 with lowerspring on my vios 2008.. so i would like to change to original rim size 185/60/15… so my car will remain the same height..???
pretty close to no change, but those original wheels will look tiny…
I have a Lexus LS400 running on 4×225/60/16 tyres at 30 psi,I wish to fit 265/35/18 to the rear and 245/45/18 to the front what will be the correct prssures for the new larger tyres?
Thanks
I’m using 185/55/R16 to my car honda jazz 09 model. Can somebody give me an idea if possible to put the tyre size 195/45/R16?
Hi, looking for some help i have an x type jag wheels are 16inch. ive bought some 17″ rims that come with 3 new tyres, 2 205/50 zr17′s and 1 225/45 r17. would it be safe and legal to put the 2 205′s on the front and buy another tyre same as the 225 and put on the rear, so 205/50 17′s on front and 225/45 17′s on the rear, would this be safe to do and legal, some people have said it would effect the abs and drive shaft and might not be safe, can anyone tell me for sure if this combination is ok, Thanks
Why can I not get the tyre calculator on my iPad 2 all I have is a big White space. If any one can help please let me know. I want to put 19 inch rims on merc clk cabrio and need to find tyre size. If any one can advise 8.5 j fronts and 9.5 j rears
Regards
Pushkin
the ipad doesnt support flash, and this is a flash based plugin
Hi, sorry if i’m being thick but why does swapping the width of tyres, 195 to 205 on wheels all the same(6j,14″ 60 profile), alter the speed. why is the rolling radius different for the same profile and wheel size?
confused(not com)
Because the 60 profile means that the sidewall height is 60% of the tread width. So a 205 tyre has a higher sidewall than a 195 tyre whatever the profile.
I was wondering the same. Is it an error???? I ope so becasuse I found some cheap wheels for my truck, but the 205 to 235 make it not possible. Please reply my MOT is next week. J
The profile (60) is a percentage of the Width.
Depending on the width what 60% is will change.
For example:
195/50 = The profile is half the width of the tire (50%)
195/45 = The profile is less than half the width (45%)
The numbers you get with this tool will not represent that exactly
because here the whole sidewall is being calculated, not the profile.
The profile is the bit you can see when the tire is on the rim.
Because the profile is a percentage of the width, it’s not a set size.
This tire calculator really helpfull for me (all of us I think), what a great idea. Two thumbs up
thanks for this tool. i love it!!!i am from Africa Kenya and appreciate this ..Good job!!!
what alternative tyres sizes can i fit to 225/80/15 as this size is quite hard to get in various tread types.
Thank you
civic 1.8sl year 2010 with VSA tyre size 205/50/16 can i change to tyre size 215/45/17 without change VSA setting?
Hi i have an Audi S3 2OT quattro and i have 19″ wheel what is the ideal tire size?
Thanks
i have a chevy beretta 3.1 z26 stock wheels 205 55 16 i wanna put in 245 45 17 is there a way to do it or can i do it with spacers ?