light wheels

ndamico

Vendor , w/Business number
Joined
Mar 20, 2008
Location
Sacramento, CA
TDI
2003 Golf 2Dr TDI, 2003 Jetta TDI, 2003 Jetta Wagon TDI, 2002 Duramax, 2003 Duramax
currently I have steel wheels on my mk4, but one is dented pretty bad. looking at switching to alloys vs. buy a new steelie. I found some AVUS 15's and some corrado speedline 15's locally as well. anyone ever ran those on a mk4? AFAIK they are 6.5" wide, not 6" like the avus but still a smidge lighter.
 

Andyinchville1

Veteran Member
Joined
Apr 7, 2016
Location
Virginia
TDI
2003 Jetta TDI wagon, 5 sp, 226K miles
I went from steelies to Avus rims and my fuel mileage went up BUT at the same time I did swap out to larger 205 75 R15 for an RPM drop at cruise so not sure what percentage of the MPG gain was attributed to the lighter rims or simply the reduction in engine RPM due to the larger tires (on the flip side now that I think about it the smaller factory tires on the steelies weighed about the same as the lighter avus rims with the larger tires so I guess it was the larger tores that made for the MPG gains at highway speeds (I mostly drive highway so stop and go increases or decreases are not known to me).
 

Jetta_Pilot

Top Post Dawg
Joined
Apr 14, 2005
Location
West Hill, Ont.
TDI
2015 Passat Highline TDI Candy White (SEL Premium) long gone 2002 Jetta TDI
I went from steelies to Avus rims and my fuel mileage went up BUT at the same time I did swap out to larger 205 75 R15 for an RPM drop at cruise so not sure what percentage of the MPG gain was attributed to the lighter rims or simply the reduction in engine RPM due to the larger tires (on the flip side now that I think about it the smaller factory tires on the steelies weighed about the same as the lighter avus rims with the larger tires so I guess it was the larger tores that made for the MPG gains at highway speeds (I mostly drive highway so stop and go increases or decreases are not known to me).

Changing to larger tires also affected your odometer reading which is now out by some. So comparing to previous Mpg readings it is not the same anymore.
Any difference in rim weight is probably negligible.
 

Andyinchville1

Veteran Member
Joined
Apr 7, 2016
Location
Virginia
TDI
2003 Jetta TDI wagon, 5 sp, 226K miles
Changing to larger tires also affected your odometer reading which is now out by some. So comparing to previous Mpg readings it is not the same anymore.
Any difference in rim weight is probably negligible.
FWIW - I would hand calculate my fuel mileage like normal (odometer readings for miles traveled and then divided by gallons filled .... I then increased my MPG readings by the percentage of increase in wheel diameter .... I am thinking that yields the corrected numbers?

the thinking is my distance traveled would be greater by the percent increase in tire diameter....
 

deepseadynamo

New member
Joined
Sep 29, 2018
Location
Maryland
TDI
2003 Wagon
FWIW - I would hand calculate my fuel mileage like normal (odometer readings for miles traveled and then divided by gallons filled .... I then increased my MPG readings by the percentage of increase in wheel diameter .... I am thinking that yields the corrected numbers?

the thinking is my distance traveled would be greater by the percent increase in tire diameter....
You need to correct the miles, before dividing by gallons.
 

Fixmy59bug

Veteran Member
Joined
Aug 1, 2009
Location
Las Vegas, NV
TDI
2015 Passat TDI SE
FWIW - I would hand calculate my fuel mileage like normal (odometer readings for miles traveled and then divided by gallons filled .... I then increased my MPG readings by the percentage of increase in wheel diameter .... I am thinking that yields the corrected numbers?

the thinking is my distance traveled would be greater by the percent increase in tire diameter....
That's actually pretty inaccurate...

The 195/65-15 is 25" tall and spins at 808 revolutions per mile.

The 205/75-15 is 27.1" tall and spins at 744 revolutions per mile.

With the larger tire, at an indicated 20 mph you are actually doing 21.7 mph.
At an indicated 50 mph, you are doing 54.2. At an indicated 80 mph, you are doing 86.7 mph.

You can see the difference gets larger the faster you go. And since you dont drive at a constant speed, you cant divide (or multiply) by a constant difference.

Why not just find someone with a VCDS (or use yours if you have one) and adjust the impulse multiplier that way your mph, odometer, and fuel mileage calculator are all correct.
 

eddieleephd

Top Post Dawg
Joined
May 27, 2012
Location
Battle Ground, Wa
TDI
2002 jetta Wagon
That's actually pretty inaccurate...
The 195/65-15 is 25" tall and spins at 808 revolutions per mile.
The 205/75-15 is 27.1" tall and spins at 744 revolutions per mile.
With the larger tire, at an indicated 20 mph you are actually doing 21.7 mph.
At an indicated 50 mph, you are doing 54.2. At an indicated 80 mph, you are doing 86.7 mph.
You can see the difference gets larger the faster you go. And since you dont drive at a constant speed, you cant divide (or multiply) by a constant difference.
Why not just find someone with a VCDS (or use yours if you have one) and adjust the impulse multiplier that way your mph, odometer, and fuel mileage calculator are all correct.

The distance can be evaluated by percentage this percentage is the larger rotation number over the smaller. 808/744=1.086 and 100 miles will end up being 108.6 miles traveled no matter how you do the math.
If you used 2 gallons during the distance you're getting 54.4 mpg.

Yet, if you don't use the conversion you will think you're getting 50mpg instead.

1.08*20mph=21.6mph 1.08*50mph=54mph and of course if you double it =108

Absolutely is spot on when comparing by percentage of the correct percentage is used.

You have to multiply the odometer miles by the increase in size percentage and then use that as the mileage in the equation. Not really you think you're getting 50mpg and multiply it by the increase and it's still spot on. Percentages work either way so long as you use the correct one.
 
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[486]

Top Post Dawg
Joined
Mar 1, 2014
Location
MN
TDI
02 golf ALH
I was going to go with some light 14" (toyota?) wheels I had kicking around, they fit on the front, but not the rear
so when you're checking fitment make sure and check the rear first

You've no doubt figured out the direction you're going by this point, though I'd just go out and find another spare, toss the two nice new tires on the front and toss the worst non-dented one in the trunk as the spare.
 
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