wheel offset question

ianbell · Post by **ianbell** » Fri Sep 23, 2005 8:12 pm

Hi wheel experts
If I change the standard 14 x 5.5 (45 offset) wheels on my NA MX5 for wheels
with a different offset, do I just need a new wheel alignment done, or are
there any other modifications that are required??
Regards
Ian Bell
CHN433

poison · Post by **poison** » Fri Sep 23, 2005 11:17 pm

Hi Ian

The only issues that I'm aware of are a) the purists would say 'it effects the
handling' but that may be all BS who knows. But for most people the issue is
b)if you lower your car later then the wheels may hit the guards on bumps.
Some people have mentioned minor panel beating of the inner guard to solve
this but this would not work on my car.

Some people swear by this 45mm offset, but purely on a physics basis I would
have thought that if you increase the width of a wheel (say by 20mm), you
should increase the offset by half of that additional wheel width (10mm=55mm
offset), thus keeping the 'centre line' of the wheel in the same place, thus
maintaining the handling etc etc.

See you at the world record thing,

Gazza

"PO1SON"

poison · Post by **poison** » Fri Sep 23, 2005 11:17 pm

Hi Ian

The only issues that I'm aware of are a) the purists would say 'it effects the
handling' but that may be all BS who knows. But for most people the issue is
b)if you lower your car later then the wheels may hit the guards on bumps.
Some people have mentioned minor panel beating of the inner guard to solve
this but this would not work on my car.

Some people swear by this 45mm offset, but purely on a physics basis I would
have thought that if you increase the width of a wheel (say by 20mm), you
should increase the offset by half of that additional wheel width (10mm=55mm
offset), thus keeping the 'centre line' of the wheel in the same place, thus
maintaining the handling etc etc.

See you at the world record thing,

Gazza

"PO1SON"

ianbell · Post by **ianbell** » Sun Sep 25, 2005 2:05 pm

Hi Gazza
I took the wheels (factory mags) off my son's Corolla today and tried them on
the MX5 because his offset is 39mm. MX5 is 45mm. All alternative mags I have
seen have been 39 offset.The Corolla tyres were 175 x 65 x 14. The MX5 is the
factory 185 x 60 x14. The wheels filled the guards up better and there was
plenty of clearance in the guards. The wheels ended up 10mm wider, each side,
when on the MX5. ( I dropped a plumbline from the guards to the ground and
then measured back to the tyres to get this measurement.) The Corolla mags are
a lot heavier than the MX5s but the car felt really good and solid on the road
- possibly even better than with the MX5 wheels. Maybe this was because they
are wider or maybe because they are heavier.
See you soon
Regards
Ian Bell
CHN433

poison · Post by **poison** » Sun Sep 25, 2005 8:08 pm

Hi Ian

Actually regarding handling and suspension performance, you definitely want
your wheels/hubs etc as light as possible. I think this is called the unsprung
weight. Weight will give you a nice feel but poor performance. ~Jeff~ is
possibly the expert on this topic as I know he has gone to lengths to get the
best wheels around.

Gazza

poison · Post by **poison** » Sun Sep 25, 2005 8:08 pm

Hi Ian

Actually regarding handling and suspension performance, you definitely want
your wheels/hubs etc as light as possible. I think this is called the unsprung
weight. Weight will give you a nice feel but poor performance. ~Jeff~ is
possibly the expert on this topic as I know he has gone to lengths to get the
best wheels around.

Gazza

ianbell · Post by **ianbell** » Sun Sep 25, 2005 10:34 pm

Thanks Jeff
It does look better with the wider 39 offset wheels but do you think that
the loading on the bearings is an issue or not.
Do you have any comments on wheel weights. As I said to Gazza the heavier
Corolla mags felt really solid on the road but he felt that performance
would suffer - I presume acceleration etc. but it felt ok to me on the test
run. The steering felt a little heavier but not really a problem - the car
just felt more solid and less twitchy (on the country roads around my
way.)Weight has to be considered if I change mags
Regards
Ian

Mike Jolley · Post by **Mike Jolley** » Mon Sep 26, 2005 6:37 am

Its like the motorbikes i race lighter =less sprrung weight=better handling
MIKE
WEZTY

From chris.tankard@aderant.com Fri Apr 27 17:31:13 2007
Content-class: urn:content-classes:message
MIME-Version: 1.0
Content-Type: text/plain; charset="us-ascii"
Subject: RE: wheel offset question
Date: Mon, 26 Sep 2005 09:15:49 +1200
Thread-Topic: wheel offset question
Thread-Index: AcXCAOszS/GJ4QBjSVKkgIl2/Y5ExQAFDv3g
From: "Chris Tankard" <chris.tankard@aderant.com>
To: "MX5List" <mx5list@mx5club.org.nz>
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Message-ID: <VeRdWC.A.o6D.DxYMGB@L733>

I did some research on this as the car that I purchased had some 16"s
that I would like to swap for 15"s (Still looking if anyone is
interested)

The main problem is that the increased weight is rotating (and
un-sprung) mass. It takes a lot more energy to rotate, stop, and change
direction. So say and additional 8lbs of weight per corner impacts the
car iro 2.2 x this amount (from memory)

From Miata.net "HP tv did a dyno test on a car that had an additional

13lbs added to the wheels (6.5 lbs per side) and the car showed a loss
of 12 whp"

Obviously it is harder to qualify the difference in handling - but the
consensus seems to be that this makes the ride harder, and less
responsive.

But the most important thing is get what's right for you - not everyone
wants a track car (some for some reason some people just want to
cruise), and lets face it - the larger wheels look cool!

Chris

From supasparky@yahoo.co.uk Fri Apr 27 17:31:13 2007
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Date: Mon, 26 Sep 2005 05:18:54 +0100 (BST)
From: glenn roberts <supasparky@yahoo.co.uk>
Subject: RE: wheel offset question
To: MX5List <mx5list@mx5club.org.nz>
In-Reply-To: <FB1D5769F12AF54EB58B29B12517B265FA765A@svmxc301.ap.aderant.com>
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The lightest wheels commonly available in NZ for a
reasonable price is the RACING HART -CP 035.(available
in 15x6 and 17x7 only from memory)
its available from most of the big tyre shops such as
mag and turbo and hyper tyres. mate those with some
sticky T1-r's or GSD3 and youre on to a
winner.Speedfactor in Tauranga also have a small
selection of "work" wheels in 15" size which are also
very very light.
Wheels any lighter than that will have to come from
the likes of VOLK or ADVAN but they are 3x the price.
Iweighed my 16" ADVANs with 205/45 Bridgstone
grid 2's and it came out at 13.6 kg per corner. im
sure that fitting a lighter tyre would be better than
the bidgy's

Glenn "SLYDIT"
http://miata.cardomain.com/id/supasparky
Currently building a DIY Turbo..Subaru VF10 Turbo, Weld el manifold, 2.5"exhaust,subaru BOV, Isuzu intercooler, 330cc GTX injectors, dual feed fuel rail,RX7 air flow meter, Greddy Emanage piggy back computor.Custom full length cold air box...YEEEEEHHHAAA
Hopefully finished by summer:)

___________________________________________________________
How much free photo storage do you get? Store your holiday
snaps for FREE with Yahoo! Photos http://uk.photos.yahoo.com

From jifjif@gmail.com Fri Apr 27 17:31:12 2007
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Date: Mon, 26 Sep 2005 16:52:40 +1200
From: ~Jeff~ <jifjif@gmail.com>
To: MX5List <mx5list@mx5club.org.nz>
Subject: Re: wheel offset question
In-Reply-To: <FB1D5769F12AF54EB58B29B12517B265FA765A@svmxc301.ap.aderant.com>
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There a set of nice-ish 15" RAYS wheels on trademe - probably not
forged but not that pricey either

Actually there's a set of MINI s-lite wheels (looks like the original
minilites / MX5 OEMs) but in 17" - would really pretty cool, but heavy

Back to offset ... the effect on bearings should be negligible really,
as long as the change is less than maybe 10-15mm.

Weight - the suspension junkies on miataforum.com reckon a combined
wheel+tyre weight of <30lbs is an acceptable threshold. Mazda
managed this fairly easily with the OEM wheels and tyres! Even though
many criticised those original bridgestones with a lack of grip, they
were light and less grip makes for easier throttle-steering

Less rotating mass means less rotating inertia (?) to overcome when
accelerating /braking and better damping on uneven surfaces. Inboard
brakes anyone?

To be honest, a lot of this stuff is purist and not the sort of thing
mere mortals will notice (myself included!) unless you regularly go
9/10ths with a stopwatch in hand...

On 9/26/05, Chris Tankard <chris.tankard@aderant.com> wrote:
[...]

Mike Jolley · Post by **Mike Jolley** » Mon Sep 26, 2005 6:37 am

Its like the motorbikes i race lighter =less sprrung weight=better handling
MIKE
WEZTY

From chris.tankard@aderant.com Fri Apr 27 17:31:13 2007
Content-class: urn:content-classes:message
MIME-Version: 1.0
Content-Type: text/plain; charset="us-ascii"
Subject: RE: wheel offset question
Date: Mon, 26 Sep 2005 09:15:49 +1200
Thread-Topic: wheel offset question
Thread-Index: AcXCAOszS/GJ4QBjSVKkgIl2/Y5ExQAFDv3g
From: "Chris Tankard" <chris.tankard@aderant.com>
To: "MX5List" <mx5list@mx5club.org.nz>
Content-Transfer-Encoding: 7bit
Precedence: list
Message-ID: <VeRdWC.A.o6D.DxYMGB@L733>

I did some research on this as the car that I purchased had some 16"s
that I would like to swap for 15"s (Still looking if anyone is
interested)

The main problem is that the increased weight is rotating (and
un-sprung) mass. It takes a lot more energy to rotate, stop, and change
direction. So say and additional 8lbs of weight per corner impacts the
car iro 2.2 x this amount (from memory)

From Miata.net "HP tv did a dyno test on a car that had an additional

13lbs added to the wheels (6.5 lbs per side) and the car showed a loss
of 12 whp"

Obviously it is harder to qualify the difference in handling - but the
consensus seems to be that this makes the ride harder, and less
responsive.

But the most important thing is get what's right for you - not everyone
wants a track car (some for some reason some people just want to
cruise), and lets face it - the larger wheels look cool!

Chris

From supasparky@yahoo.co.uk Fri Apr 27 17:31:13 2007
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;
Date: Mon, 26 Sep 2005 05:18:54 +0100 (BST)
From: glenn roberts <supasparky@yahoo.co.uk>
Subject: RE: wheel offset question
To: MX5List <mx5list@mx5club.org.nz>
In-Reply-To: <FB1D5769F12AF54EB58B29B12517B265FA765A@svmxc301.ap.aderant.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=iso-8859-1
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Precedence: list
Message-ID: <rlYXHC.A.p6D.DxYMGB@L733>

The lightest wheels commonly available in NZ for a
reasonable price is the RACING HART -CP 035.(available
in 15x6 and 17x7 only from memory)
its available from most of the big tyre shops such as
mag and turbo and hyper tyres. mate those with some
sticky T1-r's or GSD3 and youre on to a
winner.Speedfactor in Tauranga also have a small
selection of "work" wheels in 15" size which are also
very very light.
Wheels any lighter than that will have to come from
the likes of VOLK or ADVAN but they are 3x the price.
Iweighed my 16" ADVANs with 205/45 Bridgstone
grid 2's and it came out at 13.6 kg per corner. im
sure that fitting a lighter tyre would be better than
the bidgy's

Glenn "SLYDIT"
http://miata.cardomain.com/id/supasparky
Currently building a DIY Turbo..Subaru VF10 Turbo, Weld el manifold, 2.5"exhaust,subaru BOV, Isuzu intercooler, 330cc GTX injectors, dual feed fuel rail,RX7 air flow meter, Greddy Emanage piggy back computor.Custom full length cold air box...YEEEEEHHHAAA
Hopefully finished by summer:)

___________________________________________________________
How much free photo storage do you get? Store your holiday
snaps for FREE with Yahoo! Photos http://uk.photos.yahoo.com

From jifjif@gmail.com Fri Apr 27 17:31:12 2007
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Date: Mon, 26 Sep 2005 16:52:40 +1200
From: ~Jeff~ <jifjif@gmail.com>
To: MX5List <mx5list@mx5club.org.nz>
Subject: Re: wheel offset question
In-Reply-To: <FB1D5769F12AF54EB58B29B12517B265FA765A@svmxc301.ap.aderant.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=ISO-8859-1
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Content-Transfer-Encoding: 7bit
Precedence: list
Message-ID: <ix-DNC.A.q6D.DxYMGB@L733>

There a set of nice-ish 15" RAYS wheels on trademe - probably not
forged but not that pricey either

Actually there's a set of MINI s-lite wheels (looks like the original
minilites / MX5 OEMs) but in 17" - would really pretty cool, but heavy

Back to offset ... the effect on bearings should be negligible really,
as long as the change is less than maybe 10-15mm.

Weight - the suspension junkies on miataforum.com reckon a combined
wheel+tyre weight of <30lbs is an acceptable threshold. Mazda
managed this fairly easily with the OEM wheels and tyres! Even though
many criticised those original bridgestones with a lack of grip, they
were light and less grip makes for easier throttle-steering

Less rotating mass means less rotating inertia (?) to overcome when
accelerating /braking and better damping on uneven surfaces. Inboard
brakes anyone?

To be honest, a lot of this stuff is purist and not the sort of thing
mere mortals will notice (myself included!) unless you regularly go
9/10ths with a stopwatch in hand...

On 9/26/05, Chris Tankard <chris.tankard@aderant.com> wrote:
[...]

ianbell · Post by **ianbell** » Mon Sep 26, 2005 4:53 pm

Thanks for your excellent comments, Chris
Ian

Janet & Jeff Curtin · Post by **Janet & Jeff Curtin** » Mon Sep 26, 2005 11:23 pm

Keep looking for some Ray Engineering or Volk rims on Trademe or in local
papers, I picked up some in 45mil offset in 15x7" for 250$ they were two
peice and so light that when put on our "90 the difference was almost
scary compared to original rims.

J&J

Janet & Jeff Curtin · Post by **Janet & Jeff Curtin** » Mon Sep 26, 2005 11:23 pm

Keep looking for some Ray Engineering or Volk rims on Trademe or in local
papers, I picked up some in 45mil offset in 15x7" for 250$ they were two
peice and so light that when put on our "90 the difference was almost
scary compared to original rims.

J&J

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