Date:         Wed, 6 Nov 2002 08:27:26 -0800
Reply-To:     Doktor Tim <doktortim@ROCKISLAND.COM>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         Doktor Tim <doktortim@ROCKISLAND.COM>
Subject:      Re: Drilled Rotors vs. Dr. Tim
Comments: To: Derek Drew <derekdrew@rcn.com>
In-Reply-To:  <4.3.2.7.2.20021106103607.03aee008@pop.rcn.com>
Content-Type: text/plain; charset="us-ascii"; format=flowed

At 07:42 AM 11/06/2002, you wrote:

>As someone who is in the middle of putting on 245/75/16 tires (30.5" tall)
>and also heavier South African big brake kits, I'd like to hear you expand
>on the material at the end of your paragraph quoted below. "Verify those
>wheels/tires weigh no more than stock or you can start pulling the
>suspension mounts apart."
>
>I think I will be up around 67lbs per wheel vs. stock of about 47lbs per
>wheel.
>
>What was your observation that lead you to make this statement, and where
>do you think the weak points that need attention are?

Unsprung weight under inertia puts strain on the suspension arms. Every
time you hit a bump the tire absorbs some of the shock, the shocks absorb
the rest, unless you have increased the stress by enlarging the mass
unsprung with bigger is better assumptions, despite the cost. Then the
excess stress is put to the arm bushings and joints. Flexing at the
attachments of the arms will create stress cracks. Stock
wheels/tires/shocks will not cause this flexing. Add 30% unsprung weight,
drive fast through the bumps, and sooner rather than later the whole arm
tears right out. I saw this on a MB 500 SEC with oversized wheels/tires.
Numerouse cracks up to 6" long in and around the arm mounts running through
the chassis metal from the welds. It was getting ready to come clean off on
the next cross desert cruise at 100 mph or maybe even the next low speed
pot hole.

The same rotating inertia increase puts lots more strain on the steering
joints as well, more strain then was contemplated by the stock setup. If
you run those wheels and tires, make a monthly inspection of all the
suspension and steering. When you wear it out, rlebuild it and put stock
wheels and tires back on, or at least don't exceed stock weight by more
than a small margin.