Wheel size and speed question

Hum can't help much here but my general understanding is that the bigger the wheels the more energy that is required to turn the wheels, the wider the wheels the more drag that is caused with the ground hence poorer fuel economy (i know you americans don't care about this, well bush doesn't). I'm unsure on how the odometer works but i'm pretty positive the wheel size won't affect the amount of miles you clock up.

Try

i can't be bothered to readit all.

The larger the outside circumference the fewer miles will be recorded for the same real miles. Note: any serious difference may result in reduced mileage, reduced engine life and reduced performance. If you measure the outside circumference of both the original and your planed replacement, the ratio of the difference will be the same as the ratio of the differenced in recorded miles.

Note2: rims and tires are not universal and may not physically fit. If going to a larger tyre, remember to check for clearance when the springs are totally compressed and in addition be sure to check for full left to right movement a full compression of the springs to full extension for the front tyres.

For each rotation of the wheel, you will go farther with a larger wheel.

You can test this, put a mark on a pencil and roll one complete turn. Measure the distance. Now drink a can of beer, mark a point on the can, roll one turn, measure the distance. Repeat with various circumference beer cans until you are smashed and no longer care about your odometer...

Find some one with a hand held GPS to check your speedometer!

There are a bunch of things to consider...

1. Rim size doesn't enter into it... it's the overall diameter of the rim/tire combo that counts regarding impact on speedo/odo. Any circumference difference greated than about 5% can bugger things up.
2. Generally (and you should NEVER generalize!!!) increased rim size will require reduced aspect ratio e.g. go from 70-series to 60-series etc. to maintain the same overall diameter. This will result in quicker steering response and increased harshness.
3. Rim size and bolt hole spacing are not the only things to consider. The actual mounting bolts/nuts may need to be changed -- flat, tapered, spherical. For example, if the rim expects a tapered bolt/nut for correct centering, a flat bolt/nut won't work correctly.
4. Center opening also affects the fitting -- some vehicles require the opening to be tapered to correctly center the wheel, some don't. You may need to purchase "concentric centering rings" to offset this.
5. Finally, offset is important. Incorrect choice here can have the rim/tire touching the brake caliper or inside/outside of fenderwell .

Been there, got the scars. Talk to your local high perf tire store; they should be able to give advice on what would work.

:o)

Joe, I am so glad you know all 300 million of us Americans personally, including our President, so you know exactly what is in our hearts and know exactly how we feel. You are truely a wonder.

#6 offset may be different. ;-)

Here:

Larger total diameter = turns less to cover same distance = odo is incremented less. However, your speedo will also read too low and you will be speeding when your speedo indicates you're going the limit.

Put 16s on if you want, but choose a tire with a low enough profile that the overall diameter is about the same. If you were keeping the car, that's what I'd do. But since you're ready to get rid of it, I'd say instead get some cheap 13" steelies instead for the Jetta.

And

too.

I think what Joe means is that as the US has artificially low fuel costs (compared to the rest of us on the globe) you can 'generally' don't care as much as the rest of us about milage..

Bush? he'd not dare upsets the voting US public with fuel costs in line with everywhere else ..just like all presidents before him...ditto tobacco prices!

I'm not anti US before you set on me!

Jim B.

Your biggest problem is if it will fit and I can tell you it won't. Never tried a Jetta and a Civic, but every brand has their bolt numbers, spacing and everything. Did it for a 2 toyota's and few american cars, that was a big pain and pretty much only the same model (and sometimes even year) would work. Of course you could be lucky, but don't count on it.

jim wrote: : Hello,

: Im ready to throw away my Jetta but want to keep the teardrop rims for : my Civic. My question is, if you put a bigger tire/wheel size than the : original, will that be increasing or decreasing the speed? ( for : instance, you put 16 inch rims on a car that had 13s)

: I just dont want to be adding more mileage on the odometer!

You can go to lower profile tires and keep the same overall size, but depending on your cars design, safety issues can some up.

Porsche has TSB's advising that going to 18 inch wheels on Porsches with

16 inch wheels can transfer too much lateral force to the suspension (they expect a certain amount of sidewall flex to absorb some force) and cause the suspension to fail. High speed turns are not where you'd typically like to lose a wheel if you have a choice so do make sure you can put 16's on that car without endangering yourself and those around you.

taller wheels will effect the gearing. you will lose some acceleration and drop a few revs at speed. fuel economy will improve on the highway and degrade in the city.