Re: BMW Rims & Tyres

[andrew.j.thomas@xxxxxx]

Raymond (ray818@domain.elided) asks:

>>>>>>>>>
Currently my BMW 3.18 IS (three & half year model) is factory fitted with
205/60/15 Uniroyal tyres. I am thinking of changing to 205/50/16 using 16"
alloy rims but somebody told me that I would have to sacrifice some ride
comfort with a lower profile tyres and the larger rims might create more
noise for my car. Alternatively, I can keep the original 15" rims and
change to 205/55/15 Pirelli tyres. I wonder which is the better option and
its pros & cons? Though lower profile tyres look more sporty but I also
prefer a comfort and quiet ride.
<<<<<<<<<

205/55 R15 are indeed lower profile than your stock Uniroyals but they are
actually too small. Your speedometer will be thrown out of whack, as a
result of the reduction in overall gearing (the speedo 'thinks' you're
doing 70 when actually you're only doing something like 62). Also the car
may look a little silly wearing undersized tyres.

For 16" rims, 205/55 or 225/50 will fit, and are almost exactly the same
diameter as the 205/60 on 15" rims (much less than 1% difference). The
205/55 on a 16" rim will make more use of your tyres' contact patches, the
225/50 more grip still using bigger contact patches. A 205/50 R16 tyre
will, again, be too small and the car will look under-tyred, not sporty
(and the same speedo error problem).

For sure the ride will be slightly harsher on bigger alloys, though not
necessarily any louder. Provided your springs and shocks are up to scratch,
the handling will improve - sharper steering, mainly - to match the
increased roadholding available. Use good, lightweight replacement alloys
and well-regarded tyres such as Michelin Pilots, Dunlop SP9000s, Pirelli
P-Zero/P7000 or various breeds of Yokohama, and the minor decrease in ride
quality - due to the sidewall of the lower-profile tyres - will be
outweighed by the Fun Factor (tm). BBS rims are generally regarded as good
all-rounders, more expensive than some but lighter than most. Keeping
'unsprung' weight as close as possible to stock is important, or your stock
suspension will not cope. Similarly, end up with too much grip for the
current springs and shocks, and the car will be reeling as the grip
available overcomes the car's body control. Finally, if you do buy 16"
alloys, ensure the offset is suitable for an E36 (46 mm or thereabouts).

Hope this helps some.

Regards

Andrew T
'95 318is.

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