noob
 

got 97 1.9 td jetta 5 spd. best mileage 44 mpg. what do you all think about swapping 195 60 14 tires for 195 70 14 (1.5ish taller)tires then moderately lowering?

I'd try it. Maybe if you're not really committed to the idea or sure of it's success, you could score a pair or four cheap junkyard tires for a trial run.

Double check with a dealer or tire shop that has a compatibility book that they'll clear the wheel wells first. You should be fine, but some cars really don't leave much room for change.

was thinking about trying, they would increase the radius of tire by 3/4" tops but cover about 7% more ground thanstock. i can start out at idle in 2 nd gear with this thing

I have larger tires on my truck and they give an increase of about 5% + or-.
I am either covering more ground at the same revs or turning fewer revs at any given speed. I guess it depends on how I want to look at it. Either way it is a plus. I will continue to run larger tires. I have been getting about 28 mpg in the truck by the odometer, but the real mileage is about 30!:thumbup:
Go for it!

BTW...you would be getting about 47 mpg.

just wanted to see what you guys thought or experienced... made sense in my mind...simple math & physics :)

markz -

I went here and repeated your calculations. It would be a 6.6% gain with the new tires. If the odometer said 60 MPH, you'd actually be going 64 MPH. The wheels would raise the car up by 0.75". I agree that this is a cool mod.

Just to ask my standard-issue questions. Would the new tires fit on the same wheels and would the new tires fit in the wheel-well? Also, what is the before/after weight difference of the tires?

CarloSW2

Welcome to ecomodder.

44mpg as a best value isn't spectacular in that car with a TD or TDi engine - which one do you have ?

I've driven both engines to around 50mpg in similarly sized cars, and I wasn't really trying hard back then. No mods at all.
There were no dedicated low rolling resistance tyres then, either.

I'd suggest to start with changing your driving style and/or technically checking out the car before you start doing serious modifications to it.

carlos... the tires have same section width so to my understanding should be good for a go, wieght difference maybe a pound per tire?
euro... mpg # calculated with us gallon which is 3.78l, i think imperial is 4.18? also done on my regular 360km route averaging 100km/hr, has a lot of long 6-8% grades. on a different route i took last summer it seemed to do better.
thanks for the welcome guys:)

1 gallon [US, liquid] = 3.785 411 784 liter
1 gallon [UK] = 4.546 09 liter = 1 imperial gallon


44 mpg (US) is 5.35 L/100km
Either engine in a Jetta should really be able to use less than 5L/100km (47 mpg US) with a manual transmission.
In summertime and long distance riding you should really be aiming for 4.5L/100km - or better.

And they can do better, so there's plenty of room for improvement.


Good website for all sorts of conversions, including fuel consumption :
Online Conversion - Fuel Consumption Conversion

The Quick Links on the right take you to all sorts of measurements and conversions.

markz -

When I went 1-size-up from stock, I think it was a 1+ lb increase per tire (for a 2% gain). When I looked at 2-sizes-up-from-stock, it was a 3+ lb increase per tire (for a 4% gain). Because of that I only went 1-size-up-from-stock.

Depending on how you look at it, the extra lbs hurt you in acceleration but act as flywheels during coasting (right folks?!?!?).

CarloSW2

i dont think the extra lbs would hurt me as i do vastly more highway. i want to try this stuff then go on to stuff like blocking lower grill openings as my car is td - no intercooler. Nothing to crazy...yet

markz -

I think you're probably right, but I want other people to keep the detail in mind. In retrospect I think I should have gone two-sizes-up from stock.

CarloSW2