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What we’ve learned so
far….
I believe
the best racing is the closest racing and in that spirit, I try to share all my
knowledge, tips and set ups, with anybody who needs help. If you finished in
the top three last year, you don’t need any help so stop reading. If not, my
only request is that you share your information with others. Let’s make OR
& NWR racers the fastest in the land!
Part one: Suspension,
Wheels and Tires.
Toyo RA1
Tires
Toyo’s last forever. This is widely known. In fact, “back in the day”, we thought they
actually got faster as they aged. We now know that this is a wives tail
propagated by those who race Pro 7 cars. The reality is now that if you want
to go fast a set will last you only 2 weekends. There will still be a lot of
life left in them so you can keep running them but expect to be ½ second off
your fastest times with the old tires. The hot ticket will be to have tires
shaved to 2 or 3/32nd’s from Vilven tire. They are the best. You
will pay shipping and of course wear them out sooner, but they will be faster
I start my
tire pressures at 31psi left side and 32psi right side for Portland. If the car
and driver are OK the tire pressures will be 39 when hot. At Pacific I do the
reverse, 32 left side and 31 right. Take your pressures every time you come
off track. If your tire pressures are not all equal when you pull off,
something is not right with your driving or set up. As much as a 1/2psi can
make a difference. You might decide that you like the pressures at 40 or even
41psi hot. That’s fine. General consensus is that 42 is too high and will not
grip as well. Below 39 means you’re not driving hard enough or it’s a really
cool day. In either case, increase your starting air pressure. Once you
completed your first session of the day, you will no longer be able to use
these starting pressures for the rest of the day. The tires don’t completely
cool for several hours. A better tip is to add or subtract pressure shortly
after your first session to get to your desired hot pressure. Then leave them
and try to keep the tires out of direct sunlight.
When you
get your tires mounted, go to a shop where they will take the time to make them
perfect. Slip the tire buster a $20 and ask them take some extra time with
your tires... If available, pay the difference to have them balanced using a
Road Force Variance Machine. This machine matches the tire to the wheel and
minimizes the need for balancing weights. Less weight is good but I like it
because it also insures the tire is as round as possible. Round tires roll. I
know it’s a ground breaking idea but having round tires is important.
Plus…after you spend all that money on tires, you will think twice about flat
spotting them!
Take good
care of your tires. Don’t use your best set for anything but qualifying.
Don’t drive around the paddock or in the gravel. If you want to be perfect,
you will jack the car up before the tire cools, so it can cool in a round
condition. Don’t store them in a place that might freeze and keep them out of
the sunlight as much as possible.
Wheels
Wheels are
wheels. They are all within a half pound of each other so there is not much of
an advantage from one to another. The Kosei seems to be stronger than the Team
Dynamics Pro 1. Panasports look great but are expensive and I have bent at
least two of them in questionable situations. The Team Dynamics Pro 2 is nice,
no word on strength. Lately I saw an add for Basset steel wheels @ $50 they
very well might be stronger than the cast wheels.
You can
play with the offset of the wheels. Miata’s are stock at 45mm offset. (The
smaller the offset the larger the wheel base.) Kosei are at 38, Team Dynamic
offer 30, 35 or 40. You can space them further out by another 15mm by
purchasing longer studs and wheel spacers. The question is “does it make the
car faster?” A wider track could be better as it increases leverage on the
springs which makes the car more compliant. What I can tell you is that I think
the wider spacing does make the car easier to drive. It gives the car a softer
feel (or seemingly lower spring rate) by the effect of more leverage on the
spring. Wider is probably better in the rain. Spacing the wheels out more
does stick them into the air stream more, and increases drag. You be the judge
of how much.
Suspension
parts
Lower front
control arms. Put two of these on your list of upgrades. Not critical if
yours aren’t bent but a large number of the early ones are. It’s hard to tell
but, there can be a bend on the top, inboard from the shock where the rectangle
plate is welded. You will notice this if you can’t get all the camber you want
or the car has a snap over steer thing going on. Replacement control arms have
an added layer of metal and are much stronger. I haven’t bent one yet.
Steering
Tie Rod ball joints. Call Mazda and get the “R” package steering ball joints
and replace them. Theses joints correct for Bump Steer on the “R” package
cars. Unless your donor car was an “R” then you will want to get these. It’s doubtful
that they correct for all the effect of lowering but they are better than
nothing and bump steer is a factor that you want to minimize.
Bushings…Should
you replace your suspension bushings? I think the answer is yes. Everything
we read suggests that the rubber deteriorates and considering that your car
might be as much as 16 years old, it is probably safe to assume that they
aren’t in tip top shape. We have done all our cars and they do drive a bit
better. The car is more predictable and forgiving. It’s a good winter
project, but not absolutely necessary.
Cheater
bushing…yes they are out there in your run group, and yes they probably make a
difference. I never used them because it’s not worth it to me to cheat but we
believe Mazdacomp has sold many sets and that others have them installed.
There is no way to visually check the difference but a durometer check on the
rubber flange of the front lower control arm bushing should show the difference.
I wish that they would check this or allow the 40% stiffer bushing and even the
playing field.
Shocks…There
is a crowd who believes that having your shocks rebuilt is a necessary maintenance
item. It’s not. I spent plenty of money to have my shocks rebuilt and then
dyno tested them against a set that was two years old. The result…nothing. No
discernable difference at all. I’ll send you the dyno sheet if you want. Save
your money. Don’t rebuild the shocks.
While we
are on shocks, there is a gold washer or seal pressed onto the top of the
shock. Sometimes, after excessive bottoming out on the bump stop, this seal
can become bent and even separated from the shock. It is not a pressure seal
and you can remove it without doing any damage to the inside of the shock.
Pound it back into place and don’t worry about it.
What can be
replaced and should be is the lower rubber in the shocks. After a lot of use
it gets pounded out of shape and gets sloppy. I think you can get this part
from Bilstein, although I haven’t actually done it myself.
Lastly on
shocks... The Bilstein shock is basically a street shock, not a race shock.
It could be possible and may be likely that some competitors have changed the
valveing on the shock and or shortened its length. Either modification would
be a significant advantage. I would expect to see some protests in this area
next year at the national level.
Suspension Cam Bolts…If you haven’t yet, you should change all your stock cam bolts to the upgraded
bolts sold by Mazda. They have double the holding strength and will make your
life much better. The original ones will not hold when you go bouncing over
the curb and trouncing through the grass, necessitating frequent and time
consuming alignments. Always check your cam bolts as part of your pre-race
check list. I can think of two races that I was in the process of winning when
a cam bolt started to slip because it wasn’t tight enough and there goes the
win. It’s frustrating to be beaten by your own poor maintenance.
Sway bar
links. You should definitely purchase a quality adjustable sway bar kit. The
Mazda ones are fine but you have to cut about 1/2“ off the middle section to
get them to be short enough. One trick that I like is to cut and tap a stock end
link and use it for the upper portion of the front links. This gives a little
bit of forgiveness when driving. Again, its personal preference but I found
that the 100% solid connection was a little too harsh for my taste.
You don’t
need scales to set the adjustable links but you do need to get under the car
while it is on the ground. Set the links so that they are not preloading the
sway bar.
Subframe
braces…You can update your car to include the subframe brace that is stock on
the ’96 and ’97 cars. The front is no big deal but probably does add strength
to the subframe. The rear subframe brace connects all four corners of the
subframe with the body itself. It will make the assembly stronger and I
believe it affects the way the car handles as well. With the brace you will
get less grip in the back. Without the brace you get more. My estimation is
that, the sub frame flexes and allows the inside rear tire to grip more.
Personally, I don’t like the idea of the subframe flexing so I run the brace.
Jonny
Davies
Note: This
article was originally written in 2005.
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