WHEEL OFFSET

Bob K · Post by **Bob K** » Mon Sep 26, 2005 5:20 pm

Wheel offset, what is it and how can I measure it on the 195/60/15's fitted to
our NA?

Bob Kingston

ianbell · Post by **ianbell** » Mon Sep 26, 2005 6:54 pm

Hi Bob

From what I'm learning, if you are running the original Mazda wheels, then

the offset will be unchanged if you change the tyre size, but if you have
changed the wheels for aftermarket wheels, then you will have to check the
offset that is stamped onto the rim (ie 39, 45 etc) and compare them to the
original Mazda specs which were 45 for the NA. I will email you a good
description on offset.
Ian

poison · Post by **poison** » Mon Sep 26, 2005 7:57 pm

HI Bob

About 2 sections down there are some examples of how to measure offset, plus
other nice information.
http://www.rsracing.com/tech-wheel.html

Gazza
"PO1SON"

Post by **zorruno** » Mon Sep 26, 2005 11:10 pm

on 26/09/2005 7:57 p.m. Gazza wrote:

About 2 sections down there are some examples of how to measure offset,

plus other nice information.

http://www.rsracing.com/tech-wheel.html

and a heap of stuff here:
http://www.tirerack.com/about/techcenter.jsp

including offset explanation + diagram:
http://www.tirerack.com/wheels/tech/tec ... techid=101

cheers
zorruno

Ian · Post by **Ian** » Tue Sep 27, 2005 11:28 am

Hi Bob...
I assume you are aware that the more common tyre profile is 195/50 x 15...to
preserve gearing/speedo accuracy etc??
Cheers, Ian

Bob K · Post by **Bob K** » Tue Sep 27, 2005 12:12 pm

Yes I am aware of that thanks Ian. When the tyres need replacing I will
probably go to 50 series but I wonder whether the ride comfort will suffer
noticeably with the reduction in profile.
Do you know?
Regards,
Bob

Ian · Post by **Ian** » Tue Sep 27, 2005 8:34 pm

Yes, I run 195/50 x 15...it is the Mazda factory option on some models, so
obviously the ride compromise was minimal and acceptable for Mazda...and I
agree. This size also offers a choice of performance tyres, probably the
single best modification you can do to any MX5.. a fact lost on many owners,
unfortunately.
Good luck.

Bob K · Post by **Bob K** » Tue Sep 27, 2005 9:04 pm

Thanks again Ian. Most helpful, I will switch to 50 profile tyres when the
time comes.
One more question if you don't mind, can you confirm that the offset with
factory standard wheels is P45? I asked the local Mazda agent and they
couldn't easily help, suggested I contact a tyre retailer, no joy there
either.
Bob

Ian · Post by **Ian** » Tue Sep 27, 2005 9:59 pm

Yes...you are right Bob...45mm is factory. The idea with aftermarket wheels is
to get a. as close to factory offset as you can (bloody difficult...mine are
40mm) and b. light weight...a set of bathroom scales will help here.
The reasons for doing this are technical, but demonstrable and centre around
unsprung weight etc
I personably can't see the point in buying an MX5 then 'undoing' what the
factory spent a fortune on achieving!
In saying that, there are a number of sensible and subtle modifications which
are well proven...
Norman Garretts book Mazda Miata - Performance Handbook makes interesting
reading, if you are not familiar with it...

Cheers

[...]

Ian · Post by **Ian** » Tue Sep 27, 2005 10:31 pm

Thanks Jeff...I stand corrected on the offset for the later wheels.
I apologise if my advise to Bob offends your understandings on such matters.

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