Date: Tue, 8 Jan 2013 16:31:41 -0800
Reply-To: Scott Daniel - Turbovans <scottdaniel@TURBOVANS.COM>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: Scott Daniel - Turbovans <scottdaniel@TURBOVANS.COM>
Subject: Re: Thanks for input on 14" alloy wheels and 195R14 size tires
In-Reply-To: <CAKa0Qs5PPCno9YG2C3KTom=X39xOB=wwxfQG-5_jG29hUtXfSQ@mail.gmail.com>
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re the posters text :
" I have done some preliminary testing with an 8psi difference front to
rear, and so far I find it improves wind stability, and also reduces the
tire scrubbing when making a tight turn on pavement, such as when parking."
In all cases of 4 wheel vehicles .cars and vans ....with 2WD rear wheel
drive and AWD ...
there is distinct benefit to have 'more stability' in the rear than the
front.
You will notice that ALL modern cars such as Porsches, Corvettes, and
Ferraris always run 'more' in the way of a rear tire compared to the front.
the lowest tech way, and easist way to get this is more pressure in the
rear tires.
That has 'some useful affect' ..
Going up from there ....
stiffer rear tires make a nice difference. As I've written many times,
on vanagons with 14 inch wheels, I love to run a D Load Rating tire in
the rear and C's in front.
This is worth about a good 10- % imporovment in 3 things ..
straight line tracking,
turn-in crispness,
and cornering stability ..
over same tires front and rear.
You can do the same with wider or larger rear tires,
or large or wider rear wheels.
many modern performance cars might run a say 18 inch front tire, and
19's in the rear.
If the front tires are say 215/60 R 17 ...the rears will be lower
profile, but bigger cross section, such as, in this case ...235/50 R17's
in the rear with those fronts.
If people think Vanagons are 'trucks' ....they are quite wrong.
Vanagons are true 'sports vans' and have excellent and sporty suspension
for the era.
that's coil springs front and rear,
A-arm front suspenction ( A-arm front suspension is *still* to this day,
a very good suspension arranemgent. There are cars that cost way north
of a hundred grand that use A-arm suspension front and rear.
Rear trailing arsm ..those have been surpased in mondern times ...but
for the era..same thing that BMW and Mercedes Benz use.
Front anti-sway bar. All decent cars have at least a front anti-sway bar.
Better ones have a rear anti-sway bar too ...though vanagons do not.
But ..
they also have Rack & Pinion Steering ..
Before cars had rack and pinion steering..they had old fashioned
steering boxes ....
rack and pinion steering is always more direct feeling ..and generally a
much sporting type of steering.
SO ...on things like tire pressure ..
*tune for handling* as the Samba poster is talking about.
That means get the front-to-rear ration of tire pressures where you want
it ..
generally on vanagons that's about 4 psi more in the rear ..
he's gone up to 8psi in the rear which on the 'too much side.'
As overall weight in the van goes up , like for trips ....add some
pressure to all tires, keeping the ratio the same front-rear.
And....I have started out many very loaded trips with say 48 to 50 psi
on the rear..
I get into the trip about an hour and a half ....and they are just too
harsh.
I let some pressure out ..'ah' ...good smooth ride again.
the tires are most deffenitley a part of the suspension..
and the pneumatic tire has not been significantly improved up in well
over 100 years ..
adjust tire pressures wisely ..
and your Vanagon Sprot-Van can ride and handle quite nicely.
my own personal good van ...
I run an LT 205/65 R15 on the front ( micheline aggiless..just a demon
summer and rain tire, expensive too...and well worth )
and 215/65 R15's on the rear...just one size larger in back.
And I fiddled with tire pressures until it felt just right.
This van only needs to be guided gently going down the road, I don't
need to 'streer' it really.
( in contrast, if I drive a vanagon with D load tires front and rear in
14 inch ..
I have to constantly correct as it changces direction slightly on every
bump ..vanagons can be much better than that )
My van will go a qtr mile in a straight line hands-off the steering
wheel on a level freeway.
Turn-in is nice and repsonsive as well.
( to give you and idea how bad D laod 14's front and rear can be..
besides deviating from tracking nicely ....they are horribly harsh for
the front ..
if I lower tire pressures to get rid of that harsheness....then turn-in
crispness goes away ) .
And corning stability is just fine on my good van I'm talking about here..
it just geos where you point it.
really really good cars track down the road with no consicous effort of
keeping them in a lane ..
they just 'go where you point them' ..
Vanagon can be tuned in their wheels and tires to do that quite nicely.
They don't even have to be understeering pigs..
but they tend if running same tires front and rear.
Particularily the common too-high-in-the-front 85 Westy and Weekenders..
now those *really* are understeering pigs !
The more you try to corner ..the more it grinds off the front tires in
terminal oversteer.
if you ever do get to drive a car with very neutral handling ( most cars
are tuned for mild understeer for safety reasons ) ..
they are just a delight ..
a properly setup car has very neutral handling ......doesn't under or
over steer corning ...
and there is one more ideal attribute that more modern cars have
engineered in with more sophisticated rear suspensions..
the ideal is ...if you overdo it going into a corner..
just letting off the power a little makes the car tighten it's line in
the corner ..just what you want.
Vanagons can't do that, unless we get into front-rear load transfer
..outside of this discussion..
but I'll say this....Road & Track tested, in a comparsion ..
the Lotus Exige and the Tesla pure electric sportscar, which is built on
the same platform.
When flying into a corner and intentionally using an abrupt lift-off
of power, to transfer laod to the front wheels, to get more turn-in bite
...the electric Tesla couldn't do that ..since there's no engine braking
at all...
and thus it was not as capable in handling proess as the same platfrom
and suspension with a fossoile fuel engine. Interesting.
This affect is barely, barely there in vanagons ...like you'd need to be
familiar with the affect to notice that it can be there in vanagons
...it's barely there, but it's there..
and vanagons are truly 'sport vans'.
And they have the suspension to make that claim to.
And tire pressures are where you start to tune for handling.
If you want to carry 2,000 lbs in the thing ..
then treat it like a truck and air up accordingly ..otherwise, tune for
handling.
Scott
www.turovans.com
On 1/8/2013 2:31 PM, Roger VanTill wrote:""
> Here's a mathematical way to get correct pressure with new tires.
>
> http://www.thesamba.com/vw/forum/viewtopic.php?t=414400
>
