Billybones
Active Member
Hi can anyone tell me what percentage is a 265/75-16 tyre taller than a 255/70-16 tyre please.
Thank you Bill.
Thank you Bill.
neilly
Well-Known Member
But it is approx 5%.
Bearing in mind that different tyre manufactures can end up with slightly different size tyres even for the same specified size.
Cheers
I've discovered you can't easily type out calculations in a standard post. So, I've set it out in Word with a few text boxes, took a screen shot, saved it, cropped it, saved it again and then posted it it as an image.
Having done all of that, can I ask why you want to know
Having done all of that, can I ask why you want to know
Keith_L
Well-Known Member
That gives the percentage increase in the aspect ratio, but doesn't allow for the tyres being of different widths. The percentage increase in rolling diameter or circumference of the new (n) versus the old (o) tyres is as follows:
Width and wheel size must both be in the same units - inches or mm. In this case:
Width and wheel size must both be in the same units - inches or mm. In this case:
Billybones
Active Member
Thank you for all your reply's and hard work .
The reason for the question is that i am changing tyre size from the 255s to the 265s and i know this will put my speedo and odometer out, another member on this site has said that if i go bigger than a certain % i could have other problems so i wanted to know by what % i was going taller, also it will help by giving me an idea of how far out my speedo will be.
Hope this makes sense ??.
Bill
.The reason for the question is that i am changing tyre size from the 255s to the 265s and i know this will put my speedo and odometer out, another member on this site has said that if i go bigger than a certain % i could have other problems so i wanted to know by what % i was going taller, also it will help by giving me an idea of how far out my speedo will be.
Hope this makes sense ??.
Bill
Ahh, but that's not what you originally askedThank you for all your reply's and hard work
The reason for the question is that i am changing tyre size from the 255s to the 265s and i know this will put my speedo and odometer out, another member on this site has said that if i go bigger than a certain % i could have other problems so i wanted to know by what % i was going taller, also it will help by giving me an idea of how far out my speedo will be.
Hope this makes sense ??.
Bill
I guessed it was something to do with wheel arch clearance. As usual, @neilly was thinking along the right lines
As far as I know your speedo will be affected by the diameter of your wheel and tyre combo as this affects the circumference and so the number of revolutions the wheels do over a certain distance and time.
So, the % increase in overall diameter.
To calculate the circumference we multiply both circumferences by the constant π (Pi) Multiplying everything by the same constant increases everything in the same proportion and so should work out the same.
So, comparing circumferences.
To double check.
However, I wouldn't be bothering with all of that b@ll@cks. I would use a sat nav to check your speedo. They're very accurate.
You might need to adjust your steering lock stop bolts as the bigger tyres may well hit your radius arms as you approach full lock.
Keith_L
Well-Known Member
I see where the discrepancy is now. '70' in 255/70-16 isn't 70mm, it is the aspect ratio i.e. the height of the sidewall as a percentage of the tyre width - 70%. For the original tyre that would be 255 x 70 / 100 = 179mm. For the new tyre it is 265 x 75 / 100 = 199mm. Substitute these figures into your calculations and we get the same results.
Billybones
Active Member
Ah, so only about 2% difference then ,think i can live with that, sat nav not really practical as it was more about working out fuel consumption than speed.
Agree with what you say about lockstops but think i might have to use spacers as already got the shorter of the two bolt lengths that was fitted to a D2 and the 255 tyres already rub on the radius arms but the longer ones give me the turning circle of a small oil tanker.
Thanks for the help, Bill
Agree with what you say about lockstops but think i might have to use spacers as already got the shorter of the two bolt lengths that was fitted to a D2 and the 255 tyres already rub on the radius arms but the longer ones give me the turning circle of a small oil tanker
.Thanks for the help, Bill
neilly
Well-Known Member
Ahh, but that's not what you originally asked
I guessed it was something to do with wheel arch clearance. As usual, @neilly was thinking along the right lines
As far as I know your speedo will be affected by the diameter of your wheel and tyre combo as this affects the circumference and so the number of revolutions the wheels do over a certain distance and time.
So, the % increase in overall diameter.
View attachment 252346
To calculate the circumference we multiply both circumferences by the constant π (Pi) Multiplying everything by the same constant increases everything in the same proportion and so should work out the same.
So, comparing circumferences.
View attachment 252347
To double check.
View attachment 252348
However, I wouldn't be bothering with all of that b@ll@cks. I would use a sat nav to check your speedo. They're very accurate.
You might need to adjust your steering lock stop bolts as the bigger tyres may well hit your radius arms as you approach full lock.
Your maths is a little out there matey.
the 70 is the % of the width. It is still a tad over 5 %.
@Billybones
Your speedo will measure 5% under.
Cheers
Ahh, of course! Forgot about that. What a dunderheed
Bantam1
Well-Known Member
So isn't the difference in profiles 199 - 179 = 20mm.
(20 x 100)/179 = 11% more than a 255 x 70 tyre.
At top and bottom of wheel too so thats 22% or 40mm diameter increase.
Keith_L
Well-Known Member
The depth of the sidewall is 11% greater and the difference in the diameter is 40mm as you say, but to calculate the percentage increase in the rolling diameter (or circumference), which is what will impact the speedometer, you need to include the 16" / 406mm wheel. The difference then becomes 804mm vs 763mm. 804 / 763 = 1.053 i.e. 5.3% bigger.
Simplest way, take a piece of chalk, mark the tyre and the floor where both touch it, then roll it forward until the chalkmark on the tyre touches the floor again. continue the mark onto the floor. The distance between the two is the rolling circumference. BUT, if you are going fast enough the tyre may well swell a tiny bit with the heat and the circumference may change as centripetal force throws it out a bit too.
In the end it is a science but not that exact a science. As long as the speedo doesn't under-read......
You haven't been around long enough to know this. I have, so it's all my fault
@neilly is always right. However, we can console ourselves by remembering that 'nobody likes a smart @rse'.
neilly
Well-Known Member
You haven't been around long enough to know this. I have, so it's all my fault
However, we can console ourselves by remembering that 'nobody likes a smart @rse'.
I never said @Keith_L was wrong, in fact I thought his response was quite correct , post #6.
So I was not a smart @rse with his response, just said yours was slightly wrong. Sorry of you thought that was being a smart @arse, However....
Marjon had already supplied a link to the tire calculator. To determine the hight and the circumference. Which the OP and anybody else not capable of working it out correctly could have used and received an approximate reply. Post #2.
Cheers
Interceptorxj
Well-Known Member
Here's a great tool for you tyre calculator.:
https://www.tacomaworld.com/tirecalc?tires=265-75r16-255-70r16
https://www.tacomaworld.com/tirecalc?tires=265-75r16-255-70r16
Keith_L
Well-Known Member
I thought he was calling me a smart @rse, not you, on the basis you are a long serving member of the Forum and have earned the right to correct him, whereas I'm just a newbie.
