Tire Size Question

Slave2school

Top Post Dawg
Joined
Mar 20, 2004
Location
Angus, Ontario
TDI
99.5 used to at least...
If you have vagdashcom you can. I've had no joy trying to change my vss code to the other one listed on the vag-com webpage.
 

mrGutWrench

Top Post Dawg
Joined
Aug 29, 2002
Location
Carrboro, NC
TDI
'03 Jetta Wagon, 5-speed, 563K Miles (July '23)
Ernie Rogers said:
(snip) Just doing the math, changing to the 205/65R16 tires should make your speedometer right on, BUT (snip)
__. I recently put 205/65R15's (Michelin "Energie") on my '03 Wagon (some A4's have 15" wheels; I'm guessing the OP's A5 has 16's). The speedo now reads *perfectly* -- less than 1 second variation over 5 miles at 60 MPH indicated. Of course, now I have to do the math to get an accurate odo.

__. But I don't really care about the speedo - what's been the sweetest is that it's completely transformed the ride and handling of the car (not to mention the MPG). On the other hand, anything would be better than the cheepo Jap tires on it before.
 

Blackbug1

Veteran Member
Joined
Oct 10, 2006
Location
Clifton Tn
TDI
2012 Jetta
I sent Vag-Com an e-mail to see if there was any way to correct the speedometer and odometer and here is their reply.

Paul,

I am not aware of any way to use VAG-COM or the factory scan tools to
correct those readings.

Regards,
Andy

Paul wrote:

I have a 98 VW NB TDI and the speedometer and odometer are both off
checked by GPS. Is there any way to correct my odometer and
speedometer via Vag-Com?

Thanks
Paul
 

WVU TDI

Veteran Member
Joined
Jul 14, 2007
Location
Beckley, WV
TDI
2013 Passat SE 6m
I've got a similar question; my '01 TDI came with the 15" steelies and 195-65/15s, I've found a set of OEM ALuminum Beetle 16s with 205 Kumho SPTs.

Will I see much of a difference either way here? I figure the wheels are gonna be quite a bit lighter, but the tires are maybe a little heavier (wider, through shorter...) and probably stickier than the Bridgestone G009s that are on it.

Anyway, overall thoughts?
 

HopefulFred

Veteran Member
Joined
Sep 5, 2002
Location
Atlanta, GA
TDI
Golf, 2006, Indigo Blue
Two issues:
First, over the life of a tire, does the 1/2 inch change in diameter amount to a measurable change? I suspect it might. How much?

Second, does anyone know how many revolutions per mile the odometer and/or speedometer are intended to measure? That seems to me to be the way this should be discussed as that is a published feature for most tires.
 

Joe_Meehan

Top Post Dawg
Joined
Sep 3, 2005
Location
Ohio USA
TDI
NB TDI, 2002.5, Silver
First, over the life of a tire, does the 1/2 inch change in diameter amount to a measurable change? I suspect it might. How much?

~ 2-3%

Second, does anyone know how many revolutions per mile the odometer and/or speedometer are intended to measure?

~ 925
 

pearse

Veteran Member
Joined
Nov 5, 2001
Location
pennsylvania
TDI
2006 Golf BEW engine
WVU TDI said:
I've got a similar question; my '01 TDI came with the 15" steelies and 195-65/15s, I've found a set of OEM ALuminum Beetle 16s with 205 Kumho SPTs.

Will I see much of a difference either way here? I figure the wheels are gonna be quite a bit lighter, but the tires are maybe a little heavier (wider, through shorter...) and probably stickier than the Bridgestone G009s that are on it.

Anyway, overall thoughts?
You may be surprised on this one. Stock VW alum wheels are fairly heavy, I would not be surprised if the 16's are heavier. If you want light you may want to go with the 15" alum rims from the TDi GLS (also check mk3 vr-6 which came with 15" 5x100 alum rims).

If I get a chance I'll weigh my sisters rim from her 99 NB when I get home and post it up. I also have my 15" TDi GLS rims laying around, I'll weigh those too.

Although the 15" rims will be lighter (they had better be!) I will soon be searching for a set of 16" rims for my 06 Golf. I accidentally bought a set of vr-6 15" rims with tires and I messed up the calcs and thought that overall they would be very close to stock. They are not, I have lost a little over an inch in diameter with the smaller tires. My rpms have risen accordingly.

I will be looking for a set of lightweight 16" rims (not from a NB) and a set of taller than stock tires to mount on the car. A 215/60 series should give a 5% increase in diameter and drop my rpms a little at the 75-80 mph speeds that I usually commute at.
 

Joe_Meehan

Top Post Dawg
Joined
Sep 3, 2005
Location
Ohio USA
TDI
NB TDI, 2002.5, Silver
pearse said:
You may be surprised on this one. Stock VW alum wheels are fairly heavy, .
Or if they buy some really high end alloy rims which are really big money
 

HopefulFred

Veteran Member
Joined
Sep 5, 2002
Location
Atlanta, GA
TDI
Golf, 2006, Indigo Blue
Thanks Joe

Is VAGdashCOM the only way to edit your speedometer? I've just found out my new tires turn 89.9% of the rate the speedometer is programmed for. 832 rev/mi as opposed to 925 according to the ecu. I think this is farther off than my Goodyears were (I can't find a spec).

The way I am reading this, when my speedometer shows 80mph now, I am actually going 88 mph. (66 when dispayed 60, 44 when displayed 40...)

Can that be right? I bought the same size tire as came with the car (195/65R15 Mich. Pilot Exalto A/S replacing Goodyear Eagle LS)...

There has to be another fudge factor in there.
 
Last edited:

HopefulFred

Veteran Member
Joined
Sep 5, 2002
Location
Atlanta, GA
TDI
Golf, 2006, Indigo Blue
The dealer will not do anything to change the electronics or gauges. The dealer will rely on the guys at VWoA to have recommended only sizes that fit the vehicle and keep the gauges within an acceptable range of accuracy.

Note that the 17" wheels and tires do not have the same aspect as the 16" tires. If they have chosen the right sizes, the wheel will still make approximately the same number of turns (have the same circumference) regaurdless of which option the buyer chooses. See "plus 1" sizing at the Tirerack.com or elsewhere on the internet.
 

nm57

Well-known member
Joined
Apr 16, 2002
Location
Ontario
Well i dont see a problem with increasing tire size.If it is correct that the spedo is about 3mph slower than what it shows with standard size tires,go bigger .My 98 is 195/60/14, so if i go 195/65/14 i gain about 3mph and that would make the speedo correct then.

Nebojsa
 

Uncle

Member
Joined
May 6, 2005
Location
Along the Mason - Dixon Line USA
TDI
2001 Golf
06_Jetta_TDI said:
I own an 06 Jetta TDI. I noticed that my Speedometer is 3 or 4 Miles off what it should be IE: If I'm going down the road 75 I'm really going just a little over 70. This is a fact that I am guessing many of you are familiar with. (VW even admited they knew about it)
06_Jetta_TDI said:
Here is the question....

I have 205/55/16's on the TDI. Can anyone tell me if it would be a good or bad idea to go to a 205/65/16? This makes about a 3.9 mile an hour difference according to this tire size web site which would make me closer to correct on the speedometer and odometer, and would this not also show better fuel economy? (less revolutions per mile)
http://www.miata.net/garage/tirecalc.html

I have called a few places (including VW) and they said the only thing they can think of that would come into play would be the ABS.

Any thoughts?
When I went from 195-65-15 Winter tires to 205-55-16 Summer, I noticed, what seemed to be a dramatic drop in fuel mileage. I had expected it to drop, but not that much. I had checked the difference on a tire size calculator I had located on the web (link below), but it wasn't anything significant. It wasn't until I noticed the mileage difference on my odometer that it got my attention. I checked mileage between two known points with the different size tires, and for 50 miles, the odometer was reading about 3% lower than with the 16" than the 15". I then added 3% to my mileage total and the fuel usage, while still higher than with the 15" tires, was what I had expected. I hope this helps a little bit.

http://neons.org/tire/
 

Gilty_one

Veteran Member
Joined
Jul 2, 2007
Location
Warman, Saskatchewan, Canada
TDI
2016 Touareg Execline 3.0 V6 TDI; 2012 Jetta Highline TDI
Uncle said:
When I went from 195-65-15 Winter tires to 205-55-16 Summer, I noticed, what seemed to be a dramatic drop in fuel mileage. I had expected it to drop, but not that much. I had checked the difference on a tire size calculator I had located on the web (link below), but it wasn't anything significant. It wasn't until I noticed the mileage difference on my odometer that it got my attention. I checked mileage between two known points with the different size tires, and for 50 miles, the odometer was reading about 3% lower than with the 16" than the 15". I then added 3% to my mileage total and the fuel usage, while still higher than with the 15" tires, was what I had expected. I hope this helps a little bit.

http://neons.org/tire/
Your contact patch (tire to road) is now larger and therefore the rolling resistance has increased. That would account for loss of mileage.
 

pearse

Veteran Member
Joined
Nov 5, 2001
Location
pennsylvania
TDI
2006 Golf BEW engine
FYI - I promised some wheels weights, but I can't quite deliver. My sisters wheels are back on her car, but I weighted what I could.

TDi stock GLS 15" alloy wheels with 195-65-15 tires = 33lbs
VW Beetle steel wheels with snow tires = 40lbs

A mk 1 scirocco alloy wheel with 185-70-13 tire weighted 31lbs, for comparison.

I'm pretty happy about the 15" alloy wheel weight. But I want to get a weight for a 16" rim. Anyone got any laying around?
 

vwxyzero

Veteran Member
Joined
Jul 12, 2004
Location
Los Angeles, CA
TDI
'96 Passat Sedan, '96 TDI Passat Wagon, & Jetta Sedan, '83 Turbodiesel (IDI)
Old thread I know, but I need to get a handle on tire size and it's effect on the odometer reading as well.

I have used what others seam to believe is a fairly accurate tire size calculator:
http://www.miata.net/garage/tirecalc.html

and have come up with the following:

Stock tires: 195/60/14 New tires: 195/65/14

Not a whole lot of difference, but I do understand that the:
"Speedometer reading with the non-stock tire is 3.3 % too slow.
When your Spedo reads 60 mph you are actually doing 62 mph"

I get this, no problem, but it is actually 61.98 mph if I use the 3.3% factor.

What I am concerned about is how it affects my odometer reading.

I have read the whole thread and believe from what I have read and have calculated that the odometer is now showing less miles traveled then the actual miles I have traveled. Correct?

Example: say the odometer reads 500 miles traveled and I multiply that by a factor of 3.3% (or .033) I have actually traveled an additional 16.5 miles, making my total miles traveled 516.5 miles. Correct?

An additional way to figure it out would be to use the differential between the Circumference of the two tires. In this case the Stock tires circumference is 72.9 inches, and the new tires circumference is 75.3 inches. And the differential between the two (stock to new) is: 1.0329218.

So another way to look at it would to multiply miles traveled (same scenario as above) by the above factor. I.E. : 500 miles traveled x 1.0329218 = 516.4609 traveled. Almost spot on with the other example.

So am I getting this right or have I missed something here?

:cool:
 

mrGutWrench

Top Post Dawg
Joined
Aug 29, 2002
Location
Carrboro, NC
TDI
'03 Jetta Wagon, 5-speed, 563K Miles (July '23)
__. Sorry, Zero, I'm not quite sure what you're trying to get to here. Typically, on TDI's (I only have experience with A4 models so check out your own particular model) the odometer reads pretty close to right but the speedo reads high (i.e. 62-64 reading while you're actually doing 60). If you change the tire radius, you will effect *both*. Sometimes, you can get both more accurate but generally you'll get one (usually the speedo) more accurate but the other less accurate.

__. What do you have now? On both my TDI's with stock tires, I found that the odo actually read about 99 miles (varied a bit with wear on the tires but about that; for a while, my sedan was doing about 99.4 per 100 true so that's very accurate) with 100 miles actually traveled. When I went to 205/65/15's, the odo now reads a tiny bit less than 97 for 100 miles traveled but the speedo is within .5 mph of being right (hard to tell, it's less than the thickness of the needle off - I'd estimate maybe even correct to within 1/4 mph but that would only be a guess -- but it's very close to being perfect). Now I estimate mileage by adding about 3.2 miles per hundred. So, for a 900 mile tank showing on the odo, I have to add about 29 miles to the shown odo reading to get (about) the true mileage covered.

__. I do a lot of highway travel late at night. I can set the cruise and record mileage on Interstate marker over 100 miles without having to vary speed or change lanes. This doesn't impress me as a particularly accurate way of doing it, but my results have been very repeatable -- if I change tires and get a change in the results, those changed results usually repeat themselves accurately. (Five miles with a set cruise and timing the miles is usually good enought to check your speedo very accurately.)
 
Last edited:

vwxyzero

Veteran Member
Joined
Jul 12, 2004
Location
Los Angeles, CA
TDI
'96 Passat Sedan, '96 TDI Passat Wagon, & Jetta Sedan, '83 Turbodiesel (IDI)
Mr. GW,
I understand everything you said, maybe I wasn't clear enough.
Quick note(s):
_I own and drive two 96' B4's, one is a Sedan the other a Varient.
_I understand that both the spedo and odo are affecteded by up-sizing tires.
_I understand that the B4 spedo reads slightly under the speed I am actually traveling, but the odo is spot on.
_The Stock tires on a B4 are 195/60/14.
_I just up-sized to 195/65/14 which are taller and affect both my spedo and odo.
I'm just trying to figure out if the formula I used (above) is an accurate way of calculating actual miles driven.
 

mrGutWrench

Top Post Dawg
Joined
Aug 29, 2002
Location
Carrboro, NC
TDI
'03 Jetta Wagon, 5-speed, 563K Miles (July '23)
vwxyzero said:
Mr. GW,
I understand everything you said, maybe I wasn't clear enough.
Quick note(s):
_I own and drive two 96' B4's, one is a Sedan the other a Varient.
_I understand that both the spedo and odo are affecteded by up-sizing tires.
_I understand that the B4 spedo reads slightly under the speed I am actually traveling, but the odo is spot on.
_The Stock tires on a B4 are 195/60/14.
_I just up-sized to 195/65/14 which are taller and affect both my spedo and odo.
I'm just trying to figure out if the formula I used (above) is an accurate way of calculating actual miles driven.
__. OK, now I gotcha! Yes, your thinking is correct and so is your math -- except I've never seen any tires match the "theoretical" rolling radius exactly. Those radius numbers are useful as comparison and for relative comparisons but you're going to have to measure your distance (for the odo) and time (for the speedo) as the tires actually work on your car. But you'll probably see numbers that pretty much reflect your calculations - but you can't depend on the calculations alone.
 

vwxyzero

Veteran Member
Joined
Jul 12, 2004
Location
Los Angeles, CA
TDI
'96 Passat Sedan, '96 TDI Passat Wagon, & Jetta Sedan, '83 Turbodiesel (IDI)
Thank you Mr. GW, I thought I was on the right track, I just wanted to double check it.


Now it's time to drive...
 

got diesel?

Member
Joined
Mar 2, 2007
Location
New Lisbon, WI
TDI
'06 Jetta
so how big can the tires go on an A5 without interfering with the car's structure? I have a set of 215/65/16's I'd love to have on for the winter... speedo seems to be about 4mph high based on the roadside radar units I drive past... not concerned about the speedo issue... just the interfering w/ car structure.

Ernie Rogers said:
Hi,

...Just doing the math, changing to the 205/65R16 tires should make your speedometer right on, BUT

I'm a little concerned about making mistakes. If you get the much bigger tires and go too far, you may be uncomfortable with the speedo reading TOO LOW. If the bigger tires interfere with the car structure, you'll have new tires you can't use.

Ernie Rogers
 

NFTDI

Member
Joined
Jun 27, 2006
06_Jetta_TDI said:
Well this kinda answered my question I guess. I'm not hearing anyone concerned with any ABS issues etc. I am a little concerned with the "rolling resistance and gear ratio" backfiring on me.

I know for a fact that in my case...my odometer IS off (I wonder if something happened with the newer Diesels? Why is my odometer off and yours is not?). I've done this several times....watching the mile markers get farther and farther away when I should be right on it....and my last trip to work should be 56.6 miles away and my odometer showed I traveled 57.4 miles.

I'm just having a hard time figuring out if I would make that big of a change from 205/55/16 to 205/65/16 if that would throw my odometer to far off in the other direction. Maybe I will go to a 205/60/16 for starters and see how that goes. I just want my speedometer/odometer to be more accurate than what it currently is. I have an F150 as a second vehicle and the odometer on it is dead on with the highway mile markers...
Did you go with the 205/60R16's , i want to do the same and was worried about these same issues and clearances, any thoughts?
 

thatvwguy

Veteran Member
Joined
May 1, 2006
Location
Seguin, Texas
TDI
2004 Jetta TDI & 2006 New Beetle TDI
Glad to see this question posed to the list and all the responses. I'm right now trying to figure out what tire to purchase for my 04' TDI Jetta. I have the very light 15" GLS rims (about 15 lbs each) and 195/65R15's Michelin MXV4+ is the stock tire and size.

For the sake of better ride and a more accurate spedometer I have been thinking about going to a taller tire. I wanted to get a taller 195 series tire but there are very few out there and they have not gotten a good reviews from those who have purchased them.

Next best up size is a 205/70R15 which is slightly wider which will negatively impact the mpg a little. Question for Ernie (or whomever): Will the gain in RR from the width be offset by the reduction in RR from the height?

Also, any thoughts on the Michelin Hydro Edge? Supposedly it has "EnergySaver Construction™" Not sure what that translate to is RR but it sounds catchy. :)

Is there a site that lists the RR of the different brands and makes? I sure would like to find a tire around $80 each with a decent RR as opposed to the $130+ for the MXV4+, S8's, etc.

The $50 difference in price per tire would buy enough fuel to get me 2,654 miles "freebie" miles at current diesel prices. Figuring it another way if the $80 each tire got me 2.6 mpg less I would have to burn 1000 gallons of fuel to hit the break even point. That would be 45,000 - 50,000 miles which is about the interval I replaced my first set of MXV4+'s.
 

jayb79

Top Post Dawg
Joined
May 20, 2000
Location
Exeter,NH
mrGutWrench said:
__. I recently put 205/65R15's (Michelin "Energie") on my '03 Wagon (some A4's have 15" wheels; I'm guessing the OP's A5 has 16's). The speedo now reads *perfectly* -- less than 1 second variation over 5 miles at 60 MPH indicated. Of course, now I have to do the math to get an accurate odo.
__. But I don't really care about the speedo - what's been the sweetest is that it's completely transformed the ride and handling of the car (not to mention the MPG). On the other hand, anything would be better than the cheepo Jap tires on it before.
It looks like 205/65-15's are the largest diameter that has been tried. Has anyone put on anything taller than 25.49"(205/65-15) on an A4?

  • Stock Beetle,-----------------Width------Thickness----Diameter
    PassatTire-----205/55-16----8.0709-----4.4390------24.8780
    A4 Jetta Tire--195/65-15----7.6772-----4.9902------24.9803
    mrGutWrench-205/65R15----8.0709-----5.2461------25.4921
 

TornadoRed

Top Post Dawg
Joined
Aug 3, 2003
Location
West Des Moines (formerly St Paul)
TDI
2003 Jetta TDI wagon, silver; 2003 Jetta TDI wagon, indigo blue; 2003 Golf GL 5-spd, red (PARTED); 2003 Golf GLS 5-spd, indigo blue (SOLD); 2003 Jetta TDI wagon, Candy White (SOLD)
thatvwguy said:
For the sake of better ride and a more accurate spedometer I have been thinking about going to a taller tire.
Any change you make that makes the speedometer more accurate will have an adverse effect on odometer accuracy.

My speedometer is off by 3 mph. My odometer is accurate to less than 0.1% (one mile per thousand). I will not be changing tire sizes.
 

thatvwguy

Veteran Member
Joined
May 1, 2006
Location
Seguin, Texas
TDI
2004 Jetta TDI & 2006 New Beetle TDI
TornadoRed said:
Any change you make that makes the speedometer more accurate will have an adverse effect on odometer accuracy.

My speedometer is off by 3 mph. My odometer is accurate to less than 0.1% (one mile per thousand). I will not be changing tire sizes.
True, but I have never got a ticket for tracking my mileage wrong. Speeding is another issue. It is much more important to me to have an accurate speedometer
 

mrGutWrench

Top Post Dawg
Joined
Aug 29, 2002
Location
Carrboro, NC
TDI
'03 Jetta Wagon, 5-speed, 563K Miles (July '23)
TornadoRed said:
Any change you make that makes the speedometer more accurate will have an adverse effect on odometer accuracy.

My speedometer is off by 3 mph. My odometer is accurate to less than 0.1% (one mile per thousand). I will not be changing tire sizes.
__. I'm OK with making odometer calculation adjustments. I just don't like how the oversided tires work on my car -- I wish that I had stuck with stock.
 

AVRCGUY

Member
Joined
Nov 28, 2007
Location
West Des Moines, IA
TDI
2006 Jetta
06_Jetta_TDI said:
I own an 06 Jetta TDI. I noticed that my Speedometer is 3 or 4 Miles off what it should be IE: If I'm going down the road 75 I'm really going just a little over 70. This is a fact that I am guessing many of you are familiar with. (VW even admited they knew about it)

Here is the question....

I have 205/55/16's on the TDI. Can anyone tell me if it would be a good or bad idea to go to a 205/65/16? This makes about a 3.9 mile an hour difference according to this tire size web site which would make me closer to correct on the speedometer and odometer, and would this not also show better fuel economy? (less revolutions per mile)
http://www.miata.net/garage/tirecalc.html

I have called a few places (including VW) and they said the only thing they can think of that would come into play would be the ABS.

Any thoughts?
Have you made the jump to a different sized tire yet? Just curious because I seem to have the same issue you do on my '06 Jetta. My speedometer reads 5mph faster than actual speed, and my odometer ticks off the miles too fast as well.

This is really irritating since I now know that all my mileage calculations are based off an inaccurate odometer. Not to mention that technically this kind of an inaccuracy will also put me out of the warranty period quicker than it should. Grrrrrrrr:mad:

Anyway I'm just anxious to talk to someone who has tried the tire size change.

Keep us posted.

Thanks!
 

TornadoRed

Top Post Dawg
Joined
Aug 3, 2003
Location
West Des Moines (formerly St Paul)
TDI
2003 Jetta TDI wagon, silver; 2003 Jetta TDI wagon, indigo blue; 2003 Golf GL 5-spd, red (PARTED); 2003 Golf GLS 5-spd, indigo blue (SOLD); 2003 Jetta TDI wagon, Candy White (SOLD)
thatvwguy said:
True, but I have never got a ticket for tracking my mileage wrong. Speeding is another issue. It is much more important to me to have an accurate speedometer
When my speedometer shows 75 mph, I know that my true speed is 72 mph. If it shows 45 mph, the true speed is 42 mph. I never have to worry about getting a ticket because I don't know my true speed.
 
Top