by David M. Young for webBikeWorld
The decision to upgrade to aftermarket wheels for your
motorcycle is usually made for one of two reasons: appearance or performance
enhancement.
In this case, I was searching for both but with an emphasis
on performance. My motorcycle is a 1996 Ducati 916SPA.
This model was a limited production run of homologation bikes built by the
factory specifically to race in the AMA Superbike Series for Fast By
Ferracci when Freddie Spencer was their hired gun.
Despite a host of engine and running gear upgrades added to
make these same alterations legal for the race bikes, the rims were the same
cast aluminum hoops used on the standard Strada. I was interested in
upgrading the capabilities of the bike, but my intent was to keep this track
day bike street legal.
The traditional approach for wheels has seen the use of
various metals for the composition of the wheels themselves. The
material of choice for original equipment is usually aluminum, while most
upgrades go with magnesium. However, I was looking for something a bit
more unique without sacrificing durability. This led me towards a
composite material and in this case, carbon fiber.
The two major players in carbon fiber motorcycle wheels in
the U.S. are
BlackStone Tech and
Dymag. Dymag has been making aftermarket motorcycle wheels for the
past 30 years but is best known for their magnesium rims. BlackStone
Tech is a relative newcomer to this market and sells carbon fiber wheels
exclusively.
There is some controversy surrounding the use of carbon
fiber wheels for motorcycles. See
this discussion thread on the Speedzilla site for photos, comments
and thoughts on the pros and cons of carbon fiber vs. forged aluminum vs.
cast magnesium wheels.
When I originally began my search, I had not made a decision
as to which brand to purchase nor even what material. I conducted my
research by first finding out what my options were then what was available
in the market. After much deliberation, I eventually ruled out the
BlackStone Tech wheels based on their lack of time in this market.
In my opinion, they actually made the best looking wheels
with their 5 spokes and what appeared to be about an inch thick layer of
clearcoat over the visible carbon fiber surfaces. However, I could
find no one with any experience with the wheels and their cost per set was
nearly $3,500. This left the Dymag wheels as my first choice.
While roughly the same cost, they have been on the market in
many countries since 1994 with no reports of problems or issues involving
their construction or design in regular use. Dymag also makes a wheel
made of magnesium spokes with a carbon fiber rim; however I made the final
decision to go with the full carbon fiber, 3 spoke wheels with magnesium
hubs.
At the time of my purchase, the newest entry to this market
was forged magnesium wheels. Previously, most high-performance
motorcycle wheels were cast from magnesium. While manufacturing
processes are beyond the scope of this article, the forged wheels are
slightly lighter than their cast counterparts without sacrificing strength,
but again, this was a new technology to the market and I was not prepared to
do their R & D for them.
The 3 spoke wheels I chose are of a one piece design meaning
the entire rim and spokes are made from one laying of material in a single
mould. The hub carrier and hubs are then bolted to the spokes.
Another advantage in fitment is that both front and rear wheels are supplied
from the factory with bearings and spacers and are engineered to accept
stock rotors, axles, sprockets and cush drives. They are essentially a
bolt-on application and available in 17” diameters of various widths.
For this application, I chose the stock 3.5” wide front and
6” wide rear. This allows for either a 180mm or 190mm section rear
tire depending on preferences. I generally stick with the 180 to
lighten up the handling with no noticeable reduction in the legendary Ducati
stability in corners.
They also meet BS, JWL and DOT-E test standards
for road use. However most race sanctioning bodies do not allow carbon
fiber wheels although they do pass technical inspection by all of the track
day promoters that I am aware of.
The main benefit of switching to aftermarket wheels is to
reduce weight. It has been shown that a reduction of 2 lbs. of
unsprung weight is the equivalent of as much as a 10 lb reduction of sprung
weight.
Add to this the reduction in gyroscopic effect, which improves
handling in cornering making it easier to turn into the corner along with
improved acceleration, as there is less mass to accelerate.
The approximate weight of the stock Brembo made wheels on a
916 are 9.76 lbs for the 3” front wheel and 13.3 lbs. for the 5” rear
without wheel bearings, sprockets, tires or rotors for a total weight of
just over 23 lbs. The Dymag carbon fiber wheels are 4.88 lbs for a
3.5” front and 7.1 lbs for a 5.5” rear for a total of about 12 lbs.
Almost half the weight for ½” larger wheels!
When shopping for the wheels, like any other product, it is
best to look at multiple sources in order to obtain the best price and
service. I have seen prices for these wheels range new for $3,300 to
as much as $3,720.
Significant discounts can be obtained by monitoring sites
for sales over certain slow periods during the year and watching for
overstocks, etc. Purchasing used wheels is another possibility,
especially with high-end wheels as they tend to be well taken care of or
used on show bikes that have had little actual use. After considerable
searching bargain hunting, I was able to obtain my wheels for less than
$3,000 and even received an extra set of stock stainless brake rotors for
the front wheel along with a new set of Metzler Sportecs already mounted!
After receiving the wheels came the chore of switching them
for the stock units. After being assured that no modifications would
be necessary and this was a direct bolt on affair, I decided to do it
myself. This chore is made much easier with the use of front and rear
stands.
I started with the rear wheel because with the single-sided
swingarm, the fitment of the new wheel should be quite easy. As it
turned out, the hardest part at the rear was holding the rear brake to keep
the wheel from turning while I removed the single large 46 mm (1-13-16") nut
holding the Ducati's rear wheel in place.
The easiest way to do this is to have a helper step on the
brake pedal while turning the nut. After removing the nut, washer and
spacer, the wheel pulls right off. This led to the discovery that 4
studs protrude from the hub into the 4 equivalent holes in the wheel.
The stock wheel has machined slots
between each of these holes, probably designed to save weight. As a friend of
mine discovered at the track one day on his 996, if you are not careful, it
is very easy to place the studs in the slots instead of the holes.
This can cause some severe damage to both the wheel and hub if not caught
soon enough. However, Dymag avoids this problem all together by
machining holes all the way around the wheel where it slides on to the
studs.
Essentially idiot proof, even from me, as any of the holes
can be used when sliding the wheel on. Once on, replace the spacer, washer,
nut and retaining ring and you are done. Make sure to tighten the
wheel nut to the correct specification with a torque wrench. At this
stage, I always used safety wire on the retaining ring in order to prevent
any possibility of the nut backing off.
The only problem I had during this stage was when I was
tightening the nut. The wrench slipped as I was removing from the nut
causing the socket to hit my brand new magnesium hub which abruptly chipped
the black paint. No serious damage but now they no longer looked new.
Moving on to the front, the procedure is almost as simple.
Remove the brake calipers from the fork leg mounts being careful not to
stress the brake lines. Then loosen the pinch bolts, slide the axle
and pull the wheel. I was going to use the stock cast iron rotors on
the new wheels instead of the stainless rotors that came with my wheels.
You must be very careful after removing the wheel as the
rotors extend out beyond the sidewall of the tires and could easily be
damaged by laying them on the ground or dropping them. I used two
pieces of lumber, each laid parallel on the ground, wider than the diameter
of the rotor but close enough to support the tire laying on top of them.
This kept the rotor off the ground while removing the opposite side rotor.
Remove the rotors from the stock wheel and using the same
bolts, attach the rotors to the carbon fiber wheel making sure to use the
same rotor on the same side of the wheel as it came off the bike.
Torque the rotor carrier bolts after using Loctite and anti-seize compound
on the threads.
This process is very important as I found when taking off my
original wheels. This was the first time the rotors had been removed
from the stock wheels and I stripped 2 hex head bolts trying to remove them
after the steel bolt seized in the aluminum wheel. It was neither
pretty nor cheap to have these removed by a professional.
I then put everything back together, while praying that all
parts would line up. Much to my amazement, as advertised, the spacer
and speedometer sprocket lined up perfect, the axle went right in after a
new coating of grease and the brake calipers slid on to the rotors and lined
up right with the holes in the lower fork legs and on the rotors.
The next big area of concern relates to tire mounting,
removal and balancing. A friend of mine in our club, Mid-Atlantic
Ducati, had his own equipment to do tire changes and since he could take his
time and I could watch the procedure, I figured this was the safest way to
assure there would be no damage to the wheels.
The tires I chose as replacements after several track days
on the Sportecs were Dunlop 208GP’s. Dunlop tires have a reputation of
being difficult to mount due to their extremely rigid sidewalls. In
order to make it as easy as possible, we left the tires out in direct
sunlight prior to the change in order to soften up the tires for easier
mounting.
The old tires came right off with standard removal
procedures. Once the new tires were sufficiently warmed up, the
mounted up quite easily with no undue stress or leveraging on the carbon
fiber rims. After a full season of track days, the Dunlop tires began
to slide around so I decided to replace them with Pirelli Supercorsa’s, a
DOT legal racing tire. These were purchased at a track day sponsored
by Mid-Atlantic Ducati in concert with Cornerspeed at VIR with mounting
included in the purchase price.
The tire change was done by the Pirelli supplier at the
track. While I was a bit nervous when he said he had never even seen carbon
fiber wheels let alone mounted tires on them, they went right on without a
hitch and like the prior set of Dunlops, took a minimum of weight to
balance.
The next concern I had was in caring for the wheels.
While Dymag suggests no special maintenance or cleaning regimens, I make it
a point to use very mild detergents and chemicals near the wheels. They do
have a protective clearcoat over the carbon fiber however I make sure to get
the corrosive brake dust and debris completely off the rims before they get
a chance to do any damage. After 2 years, I have noticed no visible
damage, discoloration, fading, chips or cracking.
But now to the real question – How do the wheels perform?
I must admit, I am neither the fastest guy on the track nor the most
aggressive but I did notice a significant difference and since switching
wheels, I moved from the Intermediate group to Advanced in NESBA (a national
track day promoter.)
The bike felt significantly lighter in motion with much less
effort in turning and no apparent change in mid-corner stability.
While I don't know if it was the wheels or just getting more comfortable on
the track, I began experiencing wheel spin on turn exits from the rear
tires. While this was a bit unsettling the first few times it
occurred, it was very controllable and provided little actual drama.
My lap times have dropped noticeably since the wheels were installed no
doubt assisted by the move to softer compound tires.
In conclusion, I am very happy with the results of the wheel
swap. While the performance gains were enough to justify the change
alone, the positive comments I get from people who see the wheels makes the
efforts all the more enjoyable. I wholeheartedly recommend the update
to lightweight aftermarket wheels whether your preference is to improve
performance, appearance or a combination of both.
