Distance travelled?

[Tugmaster]

A new Yeti Elegance comes with the 17" Origami rims. The other standard Yetis [in the petrol division] come with 16" rims.  Does anybody know that's reading this if the speedometer is altered to compensate for the larger rim.

If a 16" rims turns for 100 times, the distance travelled is approx. 5035 ins [ 419.6 ft].  If a 17" rim turns for 100 times, the distance moved is 5350 ins [ 445.8 ft].  the distance difference therefore is approx. 26.25 ft.  [3.147 x 16 x100 / 3.147 x 17 x 100]

I'm asking this question because I seem to be doing more mileage than I thought, and I can't understand why.  The car is new and runs on factory fitted Pirelli Cinturatos 225/50 R17.

I got to thinking about this as I bought a matching rim and tyre, through the dealer, as a spare in case of trouble, but I see that the yeti comes with a 16" wheel well, so a 17" rim setup doesn't exactly sit in correctly.

Any help out there pls?  

[Ootohere]

Forget the rim it does not touch the road, and consider the tyres.

Total Diameter / Rolling Radius.

 

http://kouki.co.uk/utilities/visual-tyre-size-calculator

 

Check your cars Speedo & Mileometer Readings using GPS / Sat Nav.

 

PS 

Your Cars Speedo Under reads, and it has to. Maybe only a little, tyre dependent.

There is allowance for Tyres, Winter, Summer, Off Road.

Chains Fitted will make a Difference.  as will tyre pressures and wear a little bit.

The Spare with a Smaller Rim might be near the Same Total Diameter,

But Narrower, Different Compound, and not directional, so you slow down until you have matching tyres on a axle.

 

PPS

When you put a Spare on, even as a temp for a very short distance,

or change Tyres, or even adjust pressures, Reset your TPMS.

Edited 3 July, 2015 by goneoffSKi

[langers2k]

As goneoffski mentioned, you appear to have forgotten to put tyres on your rims.

 

Assuming what I believe are standard sizes for a yeti, the circumference of a 16 (running 215 60 r16) is 2063.4mm (6.76ft) and a 17 (running 225 50 r17) is 2087.3mm (6.84ft) which over the 100 revolutions is a difference of 2.3m (about 7.84ft)

 

This is a 1.14% difference so given that speedometers and odometers are not 100% accurate then it's probably not noticeable unless you're doing 1000's of miles. It's certainly within the 10% that is required by law.

[Tugmaster]

Thanks for prompt response, have viewed the size calculator.  Having said this how do Skoda compensate for the difference between a 16" + tyre an a 17" + tyre on the overall distance travelled? Do the two setups measure the same?

[Gobmax]

Hi have 4 year old Diesel. 2.0 ltr, have 48,000 km on original tyres & Rims still havent touched indicators

on the inside of the treads. Have done 2 sets of tyre balances @ 1 allignment since new.

+ originally did 580 km to 50 litres, now do close to 690 km to similiar usage.

LOVE MY "SNOWMAN" Have had @ owned 5 vehicles + done 1.95 million km over the last 45 years.

Hope this helps to allay your fears.+++++ Enjoy.

[AlanReed]

The problem is that we assume the speedo and odometer is correct, but the speedo in all cars "under-reads" the speed (so you can't blame the manufacturer if you get caught for speeding). My speedo is about 5-6mph "under" when compared to my (windscreen mount) satnav. Also, it's dangerous to assume the display in the MFD is absolutely correct (as who knows what sensors and systems it uses to exactly measure both distance and fuel used) - though it is a good guide.

[muddyjim]

Thanks for prompt response, have viewed the size calculator.  Having said this how do Skoda compensate for the difference between a 16" + tyre an a 17" + tyre on the overall distance travelled? Do the two setups measure the same?

 

As langers2k said there is a difference in circumference between the 2 sizes of 1.14% so that will cause a difference in mileage reading of 1.14%.Therefore it would give a difference over 10,000 of about 114 miles.

 

Of course that would cause a difference in MPG calculations too - so if for example you were getting 45 mpg with the larger wheels, it would read about 45.5 with the smaller wheels. (because it would think you have travelled further with the smaller wheel.)

 

Jim

[Ryeman]

The problem is that we assume the speedo and odometer is correct, but the speedo in all cars "under-reads" the speed (so you can't blame the manufacturer if you get caught for speeding). My speedo is about 5-6mph "under" when compared to my (windscreen mount) satnav. Also, it's dangerous to assume the display in the MFD is absolutely correct (as who knows what sensors and systems it uses to exactly measure both distance and fuel used) - though it is a good guide.

Over-reads?

[langers2k]

Thanks for prompt response, have viewed the size calculator.  Having said this how do Skoda compensate for the difference between a 16" + tyre an a 17" + tyre on the overall distance travelled? Do the two setups measure the same?

I believe they will read the same per revolution. There is a guide here about changing the speedometer reading: http://www.myturbodiesel.com/wiki/speedometer-fast-error-adjustment-and-correction-mk5-mk6/

 

If you look at the options, it does appear to be one per model so I expect all the stock rim/tyre combinations for that model will be within a couple of percent of each other which will be close enough to be lawful. Another interesting point is that many people claim that although the speedometer can over read up to 10%, that the odometer is completely accurate.

 

Out of curiosity, when you say the car appears to be doing more miles than you expect, how much do you believe it's out over what distance?

 

edit:

Another thing to point out, different brand and even models of tyre within a single brand will not all be the same size. I'm not sure how much variation is allowed for a set tyre size but this will also have an effect on odometer readings. As will over/under inflation.

[AlanReed]

Over-reads?

Oops, yes reading it back, yes, but anyway, you get my drift.....

[Ryeman]

Oops, yes reading it back, yes, but anyway, you get my drift.....

.......and funny how those nabbed speeding, blame the speedo!?

[langers2k]

A bit more information on tyre sizing.

 

Avon state up to 5% is acceptable between measured and marked up sizes for motorbike tyres so I'd expect a similar number for car tyres: http://www.avonmoto.com/download/Tires_101.pdf

 

This means that a 225mm tyre could be anywhere between 212mm and 238mm wide. Assuming the sidewall depth is linked to this measured value then thats a range of 2023mm to 2103mm for the circumference. This is already a bigger range than the difference between the two stock rim/tyre sizes! Also remember that over the life of a tyre it's radius can decrease by 6mm (assuming 8mm new and replaced when just over the legal limit at 2mm) which will also change the circumference.

 

This is probably why there is a single setting regardless of which size tyre is actually fitted to a vehicle. It's not worth the time and effort when there are so many uncontrollable factors involved.

[Ootohere]

On my Skoda i Sometime have 205/40 R 17 tyres (oem fitment)  But Dunlop Sportmaxx 205 are physically side by side small than 205 

Pirelli Zero Nero when both are new.

 

Anyway i also use 215 / 40 R 17 which i have on currently,

Side by side with the 205 /40 R Pirelli, the 215/40 R 17 are not as tall, not as wide, but do have a different amount of tread on the road.

 

With some tyres on, 

i can Zero the Miles, Zero the Maxidot Trip,  1 & 2, and its about 100 miles before the 3 might not be all matching.

The Mile on the Dash Turning over on a Mile, while the Trip is behind by 1 or 2 tenths.

Some tyre sizes fitted and all 3 ways of seeing the miles tally.

All are very near by GPS anyway.

 

& sorry on my Bad.

I should have said also 'Over reads' as in says that the car is doing 70 mph when it is only 68 or 69 mph.

Actually just now, my speedo and Maxidot with the tyres now on shows 72 mph when doing 70 MPH, Sat Nav / GPS. 

and car set on Cruise Control at 72 MPH for the 70 MPH Average Speed Cameras Stirling to Perth/

Edited 3 July, 2015 by goneoffSKi

[Llanigraham]

As langers2k said there is a difference in circumference between the 2 sizes of 1.14% so that will cause a difference in mileage reading of 1.14%.Therefore it would give a difference over 10,000 of about 114 miles.

 

Of course that would cause a difference in MPG calculations too - so if for example you were getting 45 mpg with the larger wheels, it would read about 45.5 with the smaller wheels. (because it would think you have travelled further with the smaller wheel.)

 

Jim

 

And it doesn't into account that as the tyre wears down the rolling circumference reduces as well, plus the difference in the sizes between manufacturers.

 

OP, stop worrying about it and just enjoy your Yeti.

[Gobmax]

Yes agree with,

Llanigraham

 

/or + Sat Nav +SatNav phone App can vary, Recentltly Qld/Aus police tried to charge me doing 110/in a100/km zone .

Magistrate said there was enough evidenence,  that I didn't have a case to answer to unless they could prove otherwise , My Barrister suggested Officer

might have interperated 101/as 110 KM/per hour on his hand held unit. "Love my Cruise Control" and it has 1 setting. 101 Km per hour.

Geoff

Edited 3 July, 2015 by Gobmax

[DonjSZ5]

Many years ago I carried out a technical visit to an offshore oil/gas installation being built in Newcastle. We were putting an ROV system onboard and I had to ensure the moon pool would accept it. The ROV was deployed in a steel cube frame measuring 1 metre per side, the moon pool was just over 1 metre in diameter...took me a while to convince the customers technical rep that it would not go through. 

Edited 3 July, 2015 by DonjSZ5

[Tugmaster]

Thanks everyone for all your comments and help.  Having spoken to my local tyre depot, the manager says they [the factory] just put on a tyre that has a slightly lower profile so that the diameter of the 17" rim and tyre would match the diameter of the normally fitted 16" rim and tyre.  Simples I guess!

Thanks all, enjoy your motoring!