[DeTomaso] 245/40/17 Front Tires

jderyke at aol.com jderyke at aol.com
Thu Dec 24 14:02:46 EST 2009


The limiting factors on front tires have been described many times but 
perhaps not comprehensively; this is what I've found to be true on a '72-1/2 
L-model with no flair mods:
max. 24" OD at the tread
max.10-3/4" section width (fattest part of the tire carcass)
max. 9-3/4" tread width
On 8-9" wide wheels with 4-7/8" to 5" backspace, regardless of wheel ODs 
from 14-19". 
Notes- does not address clearances for non stock brake rotors nor handling 
improvements.
Unmounted tires have slightly different measurements than mounted, properly 
inflated tires. 
Brand X's 245-40s may be wider or narrower than Brand Y's 245-40s; tire 
OD's and section widths are not tightly standardized by tire mfgrs. 
Repaired crash damage (expert or not) can radically alter all or some of 
the above. 

Max-sized front tires WILL ALWAYS need some mods to stock inner fenders and 
ajacent parts, or modified flairs on the outer fenders, or raised ride 
heights. ALL performance driving will require rolling the fender lips- even with 
stock 185-70x 15" tires, as the factory found in 1973. 

Other factors that affect max. front tire size on U.S-imported cars are: 
whether the stock headlight-height spring spacers are in or out,
whether the car has non-stock road height from changes to shock length, 
shorter springs or non-stock alignment settings, 
whether you routinely make lock-to-lock turns at higher speeds
whether you absolutely do not want any rubbing at all, 
whether you carry passengers and lots of stuff in the front trunk,
whether you drive hard or only want big tires for appearance, and so on.

There's a more extensive write up of all known front end parameters on 
undamaged Panteras in the Jan '10 POCA Newsletter (now in the U.S Mail).   Merry 
Christmas- J Deryke



More information about the DeTomaso mailing list