The frame rails slope, so it's always a little hard to derive a correct
ride height. It's also hard to make good measurements to enter into
suspension calculations. It's an ongoing project of mine. It may never
end.
I made a first set of measurements with the car on jack stands, leveled
(using a laser level) to the centerline of each axle. I measured every
suspension point X,Y,Z coordinate. Then I did all the tire and wheel
measurements and put it all into SusProg. It calculated a ride height that
I couldn't understand since there was no measurement that related any
suspension element to the bottom of the frame rails. Then I repeated all
the measurements with the car resting on the wheels and got different
numbers for almost everything. Not hugely different, but different. There
are a lot of limitations to how accurately you can measure stuff with a
plumb bob, levels, laser level and rulers. Small errors make big changes.
Since I also own Front Suspension Pro I used the method described in the
help files to make a third set of measurements. Generally their approach
doesn't work well because there are obstructions between the measurement
points and the floor. You can't just drop a plumb line. So I used the
"plane" above the car that I set up for Susprog, leveling an aluminum bar
above the car and dropping plumb lines to the points I couldn't drop to
the floor using a square attached to a level with a measuring tape refill
glued to the edge. That's a direct measurement for X and a relative
measurement that's easy to convert for Y and Z. I got all the data in--and
have a third set of results that differ substantially from the first two.
Clearly this is going to take some time.
The good news is that eventually I may have an accurate set of numbers for
Peyote, and many of them will be transferable to TR3/4. I'm willing to
share the data file and list the places that will have to be modified for
them to work with standard Triumphs.
Of course Jack Brooks is saying "How the heck is he going to do that when
he can't even get my damned SU float bowl cover to me." This time I'm
innocent Jack--I gave it to my wife to mail, and I just found the package
yesterday in the JUNK DRAWER! I guess I'm not the only flake in this
family.
-----Original Message-----
From: Larry Young [mailto:cartravel@pobox.com]
Sent: Thursday, January 23, 2003 12:01 PM
To: fot@autox.team.net
Subject: Re: Suspension/Handling Questions
In front, I'm measuring to the bottom of the frame rail near the front
cross member. In the rear, I'm measuring to the bottom of the frame rail
just before it starts to kick up. I'm running 5.50x15 Hoosiers, which
appear to be just shy of 24" diameter. From drawings in the manual, it
appears that the car has been lowered about 1/2" or so. I've been using
using Front Suspension Geometry Pro to help figure this out, but I'm
finding that the results are extremely sensitive to the measurements, so
I've been using direct measurements too.
"Michael D. Porter" wrote:
>
> I can't give you a definitive answer on rear height, but others will
> tell you what there's is, if you'll ask for a specific point on the
> frame rails to measure. Also, the height of the rear rails is greatly
> dependent upon the tire size you're running at the rear, so you should
> take that into consideration.
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