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Rims and tyres

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In the selection of the rims you should not only take looks into consideration. Here we give an overview of all factors that are important in the selection of rims & tyres and explain the key concepts. At the end of this page is a brief summary.



The rim size is normally given in inches, rim width x rim diameter, eg 7,5 x 17". Usually followed by the offset (ET) in millimeters and the number of holes with the diameter in millimeters, such as 4x98, where 4 means the rim is mounted with 4 bolts, with a PCD (Pitch Circle Diameter) of 98 mm.

Often not mentioned is the central bore for the centering of the rim, this is also given in millimeters. Almost all manufacturers have a significant larger central/spigot bore and reduce this by using spigot rings (center hub rings) to fit the measurements required for the car. The addition of "H2" (type of hump) are almost always omitted as these only play a role for classic cars.

The rim data such as 4/98 and central/spigot bore 58.1 are vehicle specific, the most common connections for Alfa and Fiat are:


Central Bore



58,1 mm

Alfa 145/146, 155, 164 TS, MiTo

Fiat 500, Barchetta, Bravo 182/198 Brava, Cinque, Coupè, Chroma, Idea, Liniea, Multipla, Panda, Punto 176/188, Seicento, Stilo, Tempra, Tipo, Uno


58,1 mm

Alfa 147, 156, 164 V6, GT, Spider/GTV 916

Fiat 500L, Ulysse, some Doblò, some Scudo


56,6 mm

Fiat (Grande) Punto 199


58,1 mm

Alfa 166 and some Fiat Scudo


65,1 mm

Alfa 159, Brera/Spider, Giulietta

Fiat Croma


Wheel sizes

The visual aspect is certainly the first thing that comes into mind when you think about the rim size. However, it should also be noted that the driving comfort plays a really important role. This results from the tyre width, the flank height of the tyre and the overall weight of the wheel, as the wheel plays a part in the unsprung mass of the car. A lower unsprung mass leads to a better handling of the car, lower fuel consumption and better acceleration.

The diameter of the entire wheel must remain within limits to avoid tacho deviations and to actually show how fast you are really going. If a larger wheel is fitted, the edge height of the tyre must be correspondingly smaller, this means there remains less of the tyre over (low profile tyres). The larger the rim and the lower the sidewall, the less the tyre flexes, this makes it more pleasant and directer to drive. If the wheel selected is too large, the tyre does not not provide any cushioning effect, this means that the suspension does all the work. You will feel the effects when going over potholes in the road surface, or manhole covers, add to this effect a firmer sport suspension then the cars handling will feel much too hard.

Another important aspect is the protection of the rim flange, the rims are significantly less protected by the tyre, a small stone on the road or a small rut can quickly lead to scratches, especially if the tyre width is already limited.


Wheels size and width aspect

The rim width must be chosen to match the desired tyre, but not every tyre will fit on any given rim and not every appropriate tyre is of any use. You should take into account that wide rims with narrow tyres leave the rim flange completely unprotected & it's only a matter of time before the rim gets damaged, damage that would have been avoided by the use of a different combination of tyre-rim.
Too wide a rim has no technical advantage, it is just heavier and increases the unsprung mass. For optical reasons to resort to an extra wide rim only makes sense if the rim has a deep deep bed. If the deeper bed is not particularly important, it is advisable to choose rims with a minimal, but still appropriate ET.
Cars with narrower tyres that finish with the edge of the wing, look just as good optically as in the use of extra-wide wheels and tyres (see example image below at "Offset"). This saves weight and gives a lower roll resistance of the tyre and offers significant advantages in handling, comfort, fuel economy & the achievable maximum speed, especially when accelerating.


Offset (ET)

The offset is the distance from the centre of the rim to rim flange (ie the area where the rim meets the disc/ drum).
In simple words: The offset indicates how deep the rim is in the wheel well. The lower the value, the more the rim comes to the outside. A rim with ET25 corresponds to an ET40 rim with a 15 mm spacer. Offsets with high values around 40 mm, are usually used by Alfa Romeo and Fiat, these are very deep into the wheel well.
Optically, the much smaller offset rims with additional spacers, look much better. The following examples shows on left a rim with ET41 and on the right a ET25 rim, both tyre and rim are of the same size.

Alfa Romeo Giuietta spacers/offset comparison - ET25 to ET41


PCD and adapter bolts

Many wheel manufacturers provide rims, due to cost and logistical reasons, with differing bolt patterns. This is especially with Alfa Romeo and Fiat rims, these are mostly 4/100 and 5/100.
These rims can be mounted with special wheel bolts that have a movable cone to compensate a difference of up to 2 mm. This is technically harmless, if proper centering is used. We do not offer these rims at all. All rims in our range have the correct bolt pattern with the proper PCD. For mounting spacers on such rims we carry these special adapter bolts in our product range. However, the adapter bolts are only available in limited sizes, you will maybe have to shorten them.


Problems with large Alfa Romeo brakes

Alfa Romeo has Brembo calipers fitted on some models, these are fitted on the outer edge (as can be seen on the disc with a diameter of 330 mm). This means that you cannot fit all available rims on the market due to the sheer size of the caliper and the possibility of obstruction. Rims are designed to withstand very high loads and usually are tapered inward.
Depending on the design of the rim, it could be for example, a 17" rim will fit over the caliper, but the same model in 18" will not, because it is differently shaped internally.
Basically, the problem can be circumvented with spacers (if outward enough space is available), some rim spacer combination have no certification, so this means you will maybe get trouble if a registration is needed in your country. For many wheels we have appropriate certification for the 5mm spacers, in some cases, the 15mm wheel spacers are easily registrable.



Rims should not be too large and not too heavy, this has catastrophic effects on the drivability and comfort & they can cause more work than they are worth. Rims available in the largest possible size are not usually the ideal rim. Abarth 500 with an 18" or an Alfa Romeo 159 with 20" may look really good, but you should clearly bear in mind that such combinations bring in daily life limitations.

Taking a rim just one number smaller usually gives more comfort and better handling. Disadvantages in handling (flexing of the tyre) are noticeable mainly on smaller rim sizes. Rims and tyres should not be too wide, narrower tyres have distinct advantages and a narrower rim flange can be better protected by the tyre.

Of course we do not want to make larger rims look bad, visually they make the best impression. We would like to draw your attention to things that you might never consider.

Even with rims and wheel spacers we suggest that you get a detailed telephone consultation before buying:
+49 4561 525310