Re: Installing larger rims/tires...

[Stewart MacLund <sundie@lunaticfringe.org>]

There's a certain amount of "work around" you can do in the case of
getting larger rims.  If you lower the profile, you can (usually) find a
profile/rim combination that's pretty close to your standard.

For instance, before i went and changed to my winter tires, i checked a
few things out, did a few calculations...

with the winter tires on (195/55/r15), the profile of the tire/rim is
102% of standard (205/50R15), and with the summer tires on (215/45/r15),
the profile of the tire/rim is 98% of standard.  I could have gone with
the standard sizing, but i wanted narrower tires for winter, and wider
for summer...

What this means, in working terms, is that with the winters on, and my
speedo says 100, i'm actually going 102, and with the summers on, 98.

I figured this was pretty safe range.

You can do the same thing, if you go to larger rims.  Just look around
for tires that have a lower profile, do some simple math, and there you
have it.

I WOULD suggest doing all of this BEFORE you buy the tire, though.

Anyone care to take a guess on how much 2%+/- difference from stock will
make your car act?  I'm noticing pretty much nothing...

Sundie....

Chuck Simpson wrote:
> 
> I'm not sure if this pertains to our cars, but I was
> watching "ShadeTree Mechanic" on TNN this weekend
> and they were installing larger rims and tires on a truck.
> The first thing they mentioned was how installing larger
> rims and tires can really screw up the speedo system
> and the transmission.
> They mentioned the speedo will need calibrating, so
> they bought some box that was attached to the chassis
> and sensor and automatically re-calibrated the speedometer.
> Then they bought some device that captured signals
> from the torque-converter and made necessary adjustments
> as needed.  It kind of looked like a 2-foot cable running
> through a small box in the middle.
> 
> Does anyone running 16+ inch rims have problems?
> Or how do you get your speedometers re-calibrated?
> 
> I believe they mentioned the truck was an automatic,
> which may have had a much greater impact on shifting
> and how the gear ratios were changed by +1.10%.
> I just wonder what affect the change would have on
> a manual transmission.
> 
> j/curious,
> 
> -Chuck Simpson
> '98 White Jetta GLX-VR6

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