Gregs Garage: May 2007

SHO Production Numbers
Model Year Units
1989 15,519
1990 8,302
1991 8,916
1992 7,801
1993 21,550
1994 13,280
1995 9,560
1996 4,730
1997 9,764
1998 3,675
1999 3,368

I personally believe the SHO is a future collectors car and way under-rated. My SHO was one in roughly 15,000 and is quite comfortable and fun to drive with 220 HP at the wheels. I plan on keeping my SHO and driving her daily. She will never be a show car under my ownership but I have been slowing reworking the car. So far I have replaced all 4 tires, one rear motor mount, on rear strut mount, the rear seat and the rear speaker covers. I purchased my 89 Sho with 108,000 original miles for $1100! I believe I got a steal on it! As soon as I make room in my garage the SHO will have a new home then I will start on the bodywork. In short, great car!

Talking About Proper Wheel Fitment
By: Dr Greg Gullion

Have you ever been the victim of annoying vibration via the steering after changing over to aftermarket rims? Most would leave well enough alone except for those inflicted with the inherent need to be different in a sea of modern day standard designed cars. I have never seen an OEM rim that I actually like. I usually quickly replace my stock rims with aftermarket ones which can potentially create vibration problems if proper wheel fitment is not achieved. I can’t even tell you how many different cars I have owned in the past which suffered from vibration while driving down the road right after I switched over to aftermarket rims. If you are the victim of steering vibration one thing you might want to ensure is centering of the wheel. In other words, you want to ensure that the center of the wheel is aligned with the center of the hub so that the car rolls down the road without excessive radial runout. In explaining proper wheel fitment major wheel retailers throw out terminology just as hubcentric, lugcentric, and hubcentric rings so and so forth. The major question is what is this terminology all about and how is it going to help solve the shimmy problems stemming from improper wheel fitment on your car?
All rims are designed to be either lugcentric or hubcentric. The stock 13” rims on my 1991 VW Golf GL are hubcentric. Hubcentricity means that the rim fits snuggly on the small lip coming off the hub. This keeps the wheel radially aligned. Utilizing the hubcentric approach, the true centering of the wheel to the hub/axle centerline is handled by the fit of the wheel’s center hole female rear face over a male shoulder that surrounds the hub center. The nuts/lugs are mostly flat on the mating surfaces, and only clamp the rim to the hub. The holding force of the lugs serves to keep the rim right to the hub, but may not be enough to overcome sideways movement under loads.
When installing a hubcentric wheel you have to fully seat the wheel so that the center female relief engages over the hub’s male locating lip. Be sure you get out your owner’s manual and follow factory tightening sequence on the lug nuts and also follow proper factory torque setting on your wrench as well because vibration problem can also stem from this as well.
My aftermarket 15” Fondmetal rims which I purchased from Discount Tires are lugcentric. A majority of aftermarket rims are lugcentric due to the larger amount of space in the bore region of the wheel compared to my stock VW rims. A majority of wheel manufactures leave a larger space in the bore simply to reduce down the amount of SKUs they have to keep up with and manufacturer in so many different sizes.
So what does lugcentric mean? Lugcentric relies upon the conical mating surface of the lugs to radially align the rims. This conical arrangement keeps the rims from moving sideways under load. Wheel centering is determined by matching the wheel holes relative to the wheel studs. Lugcentric wheels are susceptible to off-centering which leads to the creation of vibration in the steering. If the lug holes or lugs themselves are damaged (elongated) then this can result in radial runout (hence…vibration). Hubcentric wheels tend to be less susceptible to damaged lug holes / lugs since centering relies on hub centered mating. When installing a lugcentric wheel, it’s very important to avoid allowing the wheel to simply rest one of the lugnuts while installing. Allowing the wheel to hang on one of the lug nuts can lead to elongation of the lug holes or to the lug itself which could lead to potential problems on down the road. The lugcentric wheel needs to be flat to the hub face. After the wheel is flat then proper factory installation tightening needs to be followed according to the factory settings in your owner’s manual.
Within one day of purchasing my 15” lugcentric Fondmedal rims I noticed a shimmy vibration in the steering of my 91 VW Golf which never happened with the OEM rims at speeds at or above 65 MPH. I hated the high speed shimmy while driving so I decided to do some research on how to get rid of it. After paying a visit to my local Discount Tires I learned about hubcentric rings. A hubcentric ring is designed to occupy the space between the bore of the wheel and the male hub locating lip. Hubcentric rings come in a variety of fitment sizes dependent on the rim manufacturer and the vehicle you are driving. A majority of retail tire outlets make hubcentric rings available when aftermarket rims are sold. These spacers simply snap into the back of the rim’s center recess, and are held captive to the wheel. Hubcentric rings are usually designed to prevent sticking (via electrolysis) to the wheel or hub. Since the open space is occupied by these rings a majority if not all of the vibration is taken out since centering is achieved. The hubcentric rings which I applied to my 15”Fondmetals worked like a charm and virtually removed all of the vibration which I was experiencing.
There are a variety of hubcentric rings available not only by vehicle make and model and wheel type but also in composition of the ring itself. A majority of tire outlets provide polycarbon rings which work decent for daily drivers but poorly for extreme driving conditions such as autocrossing and drag racing. Poly carbon rings have a tendency to break down over time which opens up space between the wheel recess and the wheel bore thereby producing vibration. Recently, metal hubcentric rings have hit the aftermarket which tend to be more durable in the long run. Even if one cannot find a metal hubcentric ring it is easy enough to buy the plastic version and take it to your local maching shop to in order to get a metal duplication mocked up. Hubcentrics rings make all the difference in stopping wheel vibration when aftermarket rims are put on any car or truck.
Proper wheel fitment makes the driving experience much more enjoyable and is easy to achieve with today’s aftermarket technology. In the meantime if you decide to upgrade from stock rims to aftermarket ones be sure and understand how to achieve proper wheel fitment or you may find yourself getting very frustrated with the driving experience of your car.