[DeTomaso] Tires

[pantdino at aol.com]

I don't think there's a simple answer to this question.   I did an 
analysis of other high performance cars as to their front to rear 
weight ratios, tire width ratios, car weight, and horsepower, and 
concluded that something like 285 rear and 215 front were probably what 
would be fitted if the car were being made today.  So I'm running those 
sizes on 10 and 8 inch wheels with the same offsets as Campies of those 
widths.

Most people get 335/35-17 rear and 245/40-17 front (although it seemed 
that the cars i saw at PI had 225 fronts), mainly because they like the 
look of the rear 335's.  There are problems with that:

335 is too wide for an 11" rim. Yes, it will fit, but it makes the tire 
wear in the center very fast unless you run it at very low pressure 
(mid-20's).

The extra 1" of rim width of an 11" compared to a 10" is all inboard, 
which moves the tire quite close to the suspension and body metal.  
Since this also narrows the track, the extra tire width is of less 
benefit than it would be if the width were outboard.

The 335-245 tires are WAY more expensive than the 285-215, partly 
because you are very limited as to choice.  Since tires are technically 
only good for 7 years, it can add up after a while.

Wider front tires means heavier steering.

Those wide rear tires mean the car will understeer more.  I believe the 
GTS cars had 285 rear, 225 front tires and were pretty well balanced 
with the 7/8" rear bar.  So obviously if you add another 50mm to the 
rear and only 20 to the front in tire width, you're upsetting the 
balance toward understeer in a big way.

If you use all the cornering power of those wide tires, you'll 
DEFINITELY put way more torsional load on the car than it was designed 
for, and you'll crack the body.  Whether the various body stiffener 
kits will prevent this, it's too early to say.

Some racers like the 335 rears because it keeps the rear planted, which 
I'm sure I'd want to at high speed. But those cars have also been 
dialed in with special springs and shocks, body stiffening up the 
wazoo, etc, etc.  So I'm not sure it means much to those of us with 
otherwise stock suspensions.

I totally respect the viewpoints of those who love the look of the 
335's, but thought I'd post another opinion.

Donning my flame suit,

Jim








-----Original Message-----
From: MikeLDrew at aol.com
To: jmontero at fcmat.org; detomaso at realbig.com
Sent:   Sat, 1 Apr 2006 21:06:03 EST
Subject: Re: [DeTomaso] Tires


In a message dated 4/1/06 17:05:31, jmontero at fcmat.org writes:

<< For a stock, narrow bodied
car with 17" rims front and back, what are the most common tire sizes.
I am assuming that the rears are 335/35/17.  What are the fronts?  >>

>>>You want a 245/40-17.  Not all makers have a 245 tire that short.
Whatever you do, do NOT get a 245/45-17.  It will be substantially 
taller than
your
rear tire and will really look weird.

Cheers!

Mike
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