Date: Sun, 6 Oct 2002 11:23:51 -0700
Reply-To: James <tornadored@HOTPOP.COM>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: James <tornadored@HOTPOP.COM>
Subject: Re: Bigger Wheels, Unsprung mass and Calculations
In-Reply-To: <001a01c26d29$31b7a1c0$0d00a8c0@TIGER>
Content-type: text/plain; charset="US-ASCII"
I'm not really a smart guy, I just play one on the internet. Thanks, Clive,
for better explaining/substantiating what I was speculating.
> d) Don't forget that 15" tyres are heavier generally as well as the wheels,
> making the situation even worse.
Yeah, I wasn't sure about that. I compared a few random tire specs online
and the difference was minimal. But, I was comparing a 205/65-15 and a
205/70-14, which probably have about the same amount of rubber. I suspect
that larger tires, like 215's, would start to make a difference.
> The unsprung mass has to be controlled by springs and dampers.Driving slowly
> over bumps and bad terrain won't hardly be affected, but when driving at any
> speed other than a crawl WILL. The wheel's displacement will be greater, the
> forces put into the chassis via the shock absorbers will be greater and the
> shock absorbers will heat up more, be less effective and more easily lose
> control of the wheel - the outcome is worse bump and rebound control and
> hence less good roadholding, bump tolerance and ride harshness (a well know
> side effect of going to larger wheels, whether wider or taller and why I
> generally have avoided them like the plague, ditto lowered suspension with
> less travel). Its even been known for the shock mountings to eventually
> fatigue crack under these circumstances (but not to my knowledge VW's).
Again, a much better description of the point I was trying to make. Which,
again, makes me wonder if a 215/65-15 or 205/65-15 w/ the added weight
(mass) of big wheels would be outperformed (depending on the definition) by
a smaller/"narrower", but much lighter 205/70-14, or better yet, 195/75-14
set up....? I guess this is where the seat-of-the-pants comes in again?
> My Syncro seems fine with 15" Audi alloys, but then, the Syncro's unsprung
> weight at the front is quite high anyway (driveshafts, outboard CVJ's,
> strong well designed suspension and bearing componentry, reasonably decent
> brake disc and caliper sizes etc) so the OEM shockers will already be quite
> well rated and the % change not so much...
>
> ... not so for the 2WD Transporter though!
Well, so far, feedback I've received suggests people still prefer their new
set-ups, heavy rims and all...So I guess we'll see...
James
90 Carat
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