I am trying to find out if a certain SA vendor of Supalite alloy wheels has a set that will fit the Hillman Imp race car we are about to assemble,they have 13" diameter x 6"wide which are suitable for a Mini (old type) we asked will they fit our Imp? such is their power of service,we got no reply,so I set out to find out for myself.
A friend of mine,his name is Charles, is restoring a 1275 Mini,I asked would he bring a wheel so we could see if the wheel studs would line up and fit,we doknow that both the Imp and the Mini use a PCD of 4",which is 101.6mm,Charles came around and checked, and found that while the stud centers line up,the hole sizes on the Mini are smaller,so Mini wheels are not a straight fit,plus the center hole on the wheel may not suit the bearing hub either?
But what about the offset?
More on this just now,its tea time!
Back to the blog stuff, it seems that a 12"Imp wheel will fit a Mini,I assume with a low profile tire,which will not be easy to find,its much better with a 13" wheel though,the selection is far greater. This issue with a wheels offset is all about how far in or out the wheel goes,many modern cars see most of the wheel rims width is on the inside,just check a rim out on say a Ford Bantam,the wheel looks flat sided,as most of the tire sits inside and over the wheel hub,this widens the suspension and makes the track wider too.
The offset of a vehicle's wheel is the distance between the centerline of the wheel and the plane of the hub-mounting surface of the wheel. It can thus be either positive or negative, and is typically measured in millimeters. Offset has a significant effect on many elements of a vehicle's suspension, including suspension geometry, clearance between the tire and suspension elements, the scrub radius of the steering system, and visually, the width of the wheel faces relative to the car's bodywork.
Offset (ET): Distance in mm from center (C) of rim to mounting plane (M) Zero Offset - The plane of the hub mounting surface is even with the centerline of the wheel.
Positive Offset - The plane of the hub mounting surface is shifted from the centerline toward the front or outside of the wheel. Positive offset wheels are generally found on front wheel drive cars and newer rear drive cars.
Negative Offset - The plane of the hub mounting surface is toward the back or brake side of the wheel's centerline.
"Deep dish" wheels typically have negative offset or a very low positive offset.
To maintain handling characteristics and avoid undue loads on bushings and ball joints, the car manufacturer's original offset should be maintained when choosing new wheels unless there are overriding clearance issues.
Wheels are usually stamped with their offset using the German prefix "ET", meaning "Einpresstiefe" or, literally, "press depth". An example would be "ET45" for a 45mm offset.
When considering new wheels, offset can make or break a decision. Using a rim with less offset can cause the tire/rim to rub the outer fender and using a rim with more offset can cause the tire/rim to rub the inner fender or even suspension components. As an example, consider the image to the left.
In the example, the factory rim utilizes a +45mm offset (the hub is +45mm from the center of the wheel) and the rim is centered within the wheel well.
Should new rims with a +30mm offset be utilized (the hub is +30mm from the center of the wheel), the edge of the rim is shifted further outbound by 15mm and closer to the fender lip. In some situations, this could cause the tire to rub the fender lip and in extreme cases can cause damage to the tire or fender itself.When utilizing a lowered suspension, there may be a greater chance of this issue.
Thought for the day,check before you buy!
Roy
No comments:
Post a Comment