Mazda MX5 15" wheels

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Mazda MX5 15" wheels

Postby Grampy » Sat 28.05.2016, 18:00

Talking to a chap at Castle Coombe today with the above fitted to his Elan. Any other wheels fit ? The MX5 ones stick out a little but not so you really notice.
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Re: Mazda MX5 15" wheels

Postby John_W » Tue 21.06.2016, 22:24

Nige and Muley ran BMW mini wheels: viewtopic.php?f=45&t=6774
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Re: Mazda MX5 15" wheels

Postby muley » Tue 21.06.2016, 23:39

John_W wrote:Nige and Muley ran BMW mini wheels: viewtopic.php?f=45&t=6774




In actual fact, I never did.

Note for anyone going down this route, BMW in their infinite wisdom have switched from 4 x 100 to 5 x 100 or something. So only earlier MINI wheels will fit.




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Re: Mazda MX5 15" wheels

Postby rip » Wed 22.06.2016, 09:35

Vauxhall 4 stud wheels are 4x100, but these have a +49 ET offset & the largest I have seen is 15". Bigger than this are usually 5 stud.
I have a photo of my Elan on my VX alloys while its own wheels were away for refurb.
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Re: Mazda MX5 15" wheels

Postby lotusflasherman » Wed 22.06.2016, 15:36

rip wrote:Vauxhall 4 stud wheels are 4x100, but these have a +49 ET offset & the largest I have seen is 15". Bigger than this are usually 5 stud.
I have a photo of my Elan on my VX alloys while its own wheels were away for refurb.


Yup, Vauxhall wheels fit. On my SE I'm now using 17" x 7J +49 ET 4x100 'Acura' wheels that had been used on a black and orange Vauxhall Corsa. Really good 'plastic' non-chip orange paint but colour is a bit 'marmite'...

marmite.jpg


Tyres are 215/45/17 so marginally greater rolling radius than OE tyres but at least speedo is now spot on. There is a bit of polishing the dirt off the wheel arch inner lining going on at full bump position but no actual contact...
In theory the 11mm reduction in offset combined with the 1/2" (call it 12mm) increase in width should see the inside move out by 5mm and the outside by 17mm. The wheels fill the wheel arch much better but do throw dirt up along sills and lower part of the doors - interesting demonstration of the airflow along the side of the car, dirt never goes above the fold just below the side repeater.

Prior to those I was using 17" x 7J +42 ET 4x100 BBS wheels that had been used on a VW Golf GTI but the guy selling said they'd also fit BMW Mini. Those have 205/40/17 Toyo Proxes but ride was a bit harsh till I dropped the tyre pressures a bit... rear view mirror kept falling off the windscreen ! I was looking for different tyres when I saw the Corsa wheels.. :-D

bbs1024.jpg


Be aware when changing the offset a few things need to be considered. On some other threads concern has been expressed about wheel bearing loads but I don't consider that to be 'an issue' considering the weight and performance of the car. Neither do I consider the marginally increased bending moment on the rear stub axle to be a problem - far greater loading when a kerb is clipped. Front uses drive shafts and same issues apply.

Most significant aspect to consider will probably be the change in scrub radius. Lotus designed the M100 to have -3mm and 49ET will change that to +8mm. A small amount of negative is common in modern cars to reduce torque steer and give stability under braking when one circuit has been lost. Positive is reckoned to give better stability under braking with both circuits working and some older cars had up to +44mm !

In practice I've not noticed any increase in torque steer, even with an Everest chip fitted. I'm aware that if I lose one circuit I should expect the car to pull sideways but heavy braking with both seems fine. I have slotted and dimpled front discs and noticed I can feel the slots 'throbbing' through the brake pedal ... anybody else noticed that?
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Re: Mazda MX5 15" wheels

Postby dapinky » Wed 22.06.2016, 18:29

The wheels fitted as 'standard' to Angies' Corsa SE are 4 x 100 PCD - 17" gloss black alloys with an ET of +44 - they come with 215/45/17 tyres - when she's not looking I may see how they go on the Elan :D

One other thing to add to Phils informative post above is that the whole lot *may* change depending on the wheel width - the Elan OZ wheels are 6 1/2", but the S2 BBS are 7" (or I may be wrong on that, waiting to be corrected).....

.... if both have the same +60 offset, then the edges of the wheel will be in different places on the 2 cars (slightly more inboard on the S2)..... so if you fit a +52 offset wheel with a 7" width, the inner edge will be in the same place, but the outer edge will be outboard a bit - hence it *Should" clear the brakes still, but fill the arches up a bit better (purely aestetic!)

I don't know how this will affect the scrub radius, and it all gets confusing when wheel measurements use both inches and millimeters in the designation :roll:

(Ignore the "J" bit of the width designation, that only refers to the profile of the tyre bead on the wheel and nowt to do with the actual width)
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Re: Mazda MX5 15" wheels

Postby lotusflasherman » Wed 22.06.2016, 19:34

dapinky wrote:The wheels fitted as 'standard' to Angies' Corsa SE are 4 x 100 PCD - 17" gloss black alloys with an ET of +44 - they come with 215/45/17 tyres - when she's not looking I may see how they go on the Elan :D

One other thing to add to Phils informative post above is that the whole lot *may* change depending on the wheel width - the Elan OZ wheels are 6 1/2", but the S2 BBS are 7" (or I may be wrong on that, waiting to be corrected).....

.... if both have the same +60 offset, then the edges of the wheel will be in different places on the 2 cars (slightly more inboard on the S2)..... so if you fit a +52 offset wheel with a 7" width, the inner edge will be in the same place, but the outer edge will be outboard a bit - hence it *Should" clear the brakes still, but fill the arches up a bit better (purely aestetic!)

I don't know how this will affect the scrub radius, and it all gets confusing when wheel measurements use both inches and millimeters in the designation :roll:

(Ignore the "J" bit of the width designation, that only refers to the profile of the tyre bead on the wheel and nowt to do with the actual width)


As usual you are correct Dave. SE 15" OZ are 6 1/2" and S2 are 7". Somewhere in Lotus info is a bit that S2 wheels won't fit an SE but didn't say why and I believe lots of SE owners have fitted S2 wheels unaware of this.. :lol:
I wasn't interested in S2 wheels because of their silly prices and I wanted to take advantage of 17" tyres being relatively cheap so went back to first principles to do some sums to see what would fit.

17" gives lots of room for some big brake upgrades and I called in on Hi-Spec on my way to Brands last year when running the BBS wheels. They now offer a kit for 17" wheels - www.hispecbrake.co.uk/335mon.html but unfortunately it won't fit my 'marmite' rims because of wheel balance weights fouling the caliper.. :banghead: so I'll still be needing a bespoke kit.
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Re: Mazda MX5 15" wheels

Postby John_W » Wed 22.06.2016, 20:34

muley wrote:
John_W wrote:Nige and Muley ran BMW mini wheels: viewtopic.php?f=45&t=6774


In actual fact, I never did.

Sorry, Jim; my mistake.

When I swapped the Vauxhall type aftermarket 15" wheels previously on my car for a set of S2 16" wheels, I noticed a definite improvement in steering. Ie no tramlining or twitchiness on straights. The Vauxhall wheels look fairly similar to S2 wheels (they're on the Pacific Blue car in my garden on the banner header of the website home page http://www.lotuselancentral.com/index.htm , between Ben Weston's yellow S2 and Andrew Ennis's Medina S2) but had less -ve offset than Lotus originals. Getting the tracking adjusted might have improved things, but that would have been getting even further away from what Lotus designed.

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Re: Mazda MX5 15" wheels

Postby lotusflasherman » Wed 22.06.2016, 21:08

John_W wrote:
muley wrote:
John_W wrote:Nige and Muley ran BMW mini wheels: viewtopic.php?f=45&t=6774


In actual fact, I never did.

Sorry, Jim; my mistake.

When I swapped the Vauxhall type aftermarket 15" wheels previously on my car for a set of S2 16" wheels, I noticed a definite improvement in steering. Ie no tramlining or twitchiness on straights. The Vauxhall wheels look fairly similar to S2 wheels (they're on the Pacific Blue car in my garden on the banner header of the website home page http://www.lotuselancentral.com/index.htm , between Ben Weston's yellow S2 and Andrew Ennis's Medina S2) but had less -ve offset than Lotus originals. Getting the tracking adjusted might have improved things, but that would have been getting even further away from what Lotus designed.

John


Most tramlining or straight line twitchiness is due to a poor choice of tyre or wrong pressures. Wikipedia sums it up quite succinctly - https://en.wikipedia.org/wiki/Tramlining
See it's also called 'nibbling' - but must admit I'd never heard it called that !
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Re: Mazda MX5 15" wheels

Postby Giniw » Wed 22.06.2016, 22:18

The offset +60 being from the symmetry plane of the wheel to its attachment I don't understand why the wheel width (6.5 or 7") would necessarily change anything if the wheel is different. The BBS S2 wheels are probably just less bumpy than the SE Ruote ones?

As long as the offset is the same the symmetry plane is at the same place relative to the attachment, isn't it? I may be wrong, of course.
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Re: Mazda MX5 15" wheels

Postby dapinky » Wed 22.06.2016, 22:56

The difference in the wheels shouldn't affect the scrub radius (as you say the symetry remains) - the difference will be that it will be half an inch (12.7mm) wider, split between 6.35mm inboard, and 6.35mm outboard. As such, it will fill the outer arch better, but also (potentially) be more capable of scrubbing the arch liner inboard on full lock/full bounce.

I was trying to suggest that if you go up to a 17" wheel, you *may* be better off with less than +60 to reduce any such issues (but that WILL affect the scrub radius).

I can only think that by fitting the S2 wheels on an SE could cause these issues (I know the FED had a 7" wheel, but it also had slightly stiffer suspension) {but as all suspension is physically interchangable, and much of the OE stuff has many miles of wear on them and many have been replaced with something else, no known problems are really concerning owners who have done the swap.
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Re: Mazda MX5 15" wheels

Postby lotusflasherman » Thu 23.06.2016, 01:13

GD1.JPG


Knew I'd seen it somewhere ...
SE had 4 half upper wishbones with same halves for front & rear parts but US had different front & rear parts to give more clearance for 7" rims to achieve full lock.
I was told when the S2 was going into production that it was going to use the US wishbones so assumed if UK SE couldn't use US 16" OZ it couldn't use 16" S2 BBS either...
Looking at Parts Book I think S2 had it's own wishbones designed with bracing struts added.
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