Re: [DML] Re: Reproduction tires needed!

[mike.griese@xxxxxxxxxxxxxxxx]

Dan - You're not wrong in your understanding of what new wheels
might do to a DeLorean, but is does sound like your understanding
is incomplete.

Changing wheel/tire combinations can adversely affect handling, but 
it doesn't have to if you do your homework.  The DeLorean wheels are cast 
aluminum and are fairly heavy.  This weight contributes to a quantity known 
as unsprung weight.  Unsprung weight is a Bad Thing in automobile dynamics, 
because you have little control over unsprung weight.  Properly sized forged 
aluminum wheels can improve handling by being lighter than the original wheels, 
reducing unsprung weight.  By properly sized I mean that the wheel offset is the 
same as the original wheels and the rim width is not increased.  The key is 
making sure the offset is correct.  Offset is the placement of the edges of the 
rims relative to the wheel hub.  If the offset is identical to the original wheels, 
the contact patch stays in the same place relative to the suspension pivot points, 
which means you don't need to make any additional suspension changes.

Larger rims and lower profile tires will make the ride noticeably harsher, 
however, as you won't have the extra spring rate of the sidewall to help 
absorb bumps.  If you want to tune this out, you can by changing the
rate of the front and rear springs.  To achieve the same ride, you would 
need to know the current spring rates, the spring rate of the sidewalls 
of NCT tires, and the spring rate of the sidewalls of your new low profile
tires.  There is a bit of math to run through, but it's not rocket science.

Lower profile tires can improve handling by keeping the area of the 
contact patch as large and consistent as possible.  They do this by 
having less deflection in the sidewalls, which keeps the tire from 
"rolling over" during cornering.  A side benefit is that the contact patch 
stays in the same place relative to the hub, which slightly widens the track 
under hard cornering compared to tires with taller sidewalls.

Another advantage of a larger wheel is space for larger brake rotors and
calipers.  The DeLorean is underbraked compared to other performance 
cars, but there isn't much that can be done with the stock wheels as there
isn't much room for more rotor.  If I were headed in the direction of larger
brakes (and those of you looking for significant HP increases really should)
I would upgrade the hubs to a 5-bolt pattern instead of the 4-bolt pattern 
on the car.  

--
Mike


-------------- Original message from "Dan" <djdanwilson@xxxxxxxxx>: -------------- 


> 
> The car was engineered to work with the wheels it came with. I'm not 
> an engineer, but I do know all the components of a car's suspension 
> are designed to work together as a complete system. From what I 
> understand it's not as simple as just bolting on a new set of larger 
> rims without having everything else in that system becoming affected 
> somehow. Larger wheels mean larger rotating mass, and that means more 
> effort to put them in motion, and more effort to stop them, right? So, 
> I'd accelerate slower, just what a DeLorean needs, and put more stress 
> on my brakes trying to stop at an increasing braking distance. Don't 
> we also start getting i




To address comments privately to the moderating team, please address:
moderators@xxxxxxxxxxx

For more info on the list, tech articles, cars for sale see www.dmcnews.com

To search the archives or view files, log in at http://groups.yahoo.com/group/dmcnews 
Yahoo! Groups Links

<*> To visit your group on the web, go to:
    http://groups.yahoo.com/group/dmcnews/

<*> To unsubscribe from this group, send an email to:
    dmcnews-unsubscribe@xxxxxxxxxxxxxxx

<*> Your use of Yahoo! Groups is subject to:
    http://docs.yahoo.com/info/terms/