I bought and installed some third party wheels that were advertised as having the correct offset for the Mk3 MX-5. They are 16R-7j ET40 as opposed to the original 17R-7j ET55 Mazda wheels.
The first thing I noticed was how far they stick out compared to the originals (see picture). I’ve also observed a change in the cars handling. The steering feels a little more ‘darty’ wanting to turn in quickly, plus there is an increase in tramlining and the wheels wanting to follow bumps etc in the road.
Will these wheels cause any problems (such as premature wearing of bearings/suspension joints? etc)
Does anyone here run ET40 offset wheels with any problems? Did you notice any changes in handling/steering? I’m running the recommened Mazda tyre size of 205x50R16.
The supplier said they’ve sold plenty of sets without any issues.
I just want peace of mind that they won’t damage my P&J, and not knowing much about wheels I went with what they said were correct for the car.
In the late 60’s and early 70’s I was one of those who fitted “wide wheels” - in my case to Heralds/Spitfires. In those cases the back end stuck to the road better, but the front wheels caught the white lines, ridges etc. a lot more then the standard wheels giving the symptoms you describe. In the case of the sptifire the cure was to replace the 13" steering wheel with the 15" item from the Herald!
Maybe there’s something that can be done to the alignment on your MX5 to compensate for the extra width?
It’s not so much the extra width (1/2 inch more than the Mazda standard 16"), but the different offset. ( the 7J +40mm wheels will be spaced out an extra 15mm + 1/4 inch (6.35mm), which gives an overall spacing of 21.35mm on each side).
It’s this extra 21mm spacing that I’m most concerend about. As above I’m concerned about over stressing the suspension joints/wheel bearings. The change in handling is also not welcomed. I did a test run today and the car starts to ‘wander’ slightly at high speeds (70mph+), so that can be added to the list of changes I’ve noticed in handling. It’s also worth noting I’m running Winter tyres on these wheels (I hope to have my original wheels back up and running by the summer, and thus use these as a spare or Winter set). So perhaps some of these handling traits are from the tyres rather than the wheels?
I also have two further smaller concerns about running this offset. As the wheels push out slightly past the wheel arches I believe they are technically illegal? I’ve also noticed I now spray up crap along the sides of the car, not so bothered about dirt but I don’t want to stone chip the hell out of the side panels!
The wheels were advertised as being 6.5J and having the correct offset for the MX-5. Both of which are incorrect. I expected them to list wheels that were the correct specification for the car, so I’m a little disapointed that they weren’t as advertised.
Anyway I’m told they’ve sold several sets without issue. So…
Does anyone here run ET40 offset wheels? and do any of the 4 issues I’ve outlined above cause any problems in the long term? I just want someone to say… yes I’ve run ET40 wheels for 20K miles and my suspension hasn’t fallen apart yet…etc
as far as i can remember they would be illegal. when i built a kit car i had to trim the mudguards to cover the WHEEL not the tyre. so if your actual wheel is outside the footprint of the car when looking from above its illegal. they sort of allow the tyre to be exposed. but sure looks close to me. and as you say the handling must be cr*p.
they tramline on ordinary tyres if not set up, ask tony at WIM for guidance.
Hi I run ET40 wheels on my MK3’5 with a Toyo T1R’s on 17" wheels…never had a problem with the handling etc and the car has had a full geo set up…Went through its 1st MOT with no problems…
I am not exactly sure what the offset of these wheels is, but it is much less that the standard Mazda one. They are also greater width.
There have been no issues with suspension issues. The race cars run wider wheels and tyres and considerably more stress, drive shafts, gearboxes, dampers all break, but other than impact, suspension does fine. Pushing your wheels further out will naturally change the feel of the car, however there is no reason this should have to be a concern to drive. I don’t know about the MK3.5’s but if it is at the agricultural standard height of MK3’s personally I would look to lower the car and have it realigned. If you are anywhere near Sheffield Mr Roddison can help you out with that.
Now that I’ve been running these wheels for a while I thought I would add some feedback.
I’ve since had the car precision aligned on a hunter wheel alignment machine. Some of the figures were a little off, and post alignment the high speed ‘wandering’ has pretty much gone. The heavier feel to the steering remains, but I’ve pretty much got used to it.
The biggest drawback to these wheels has turned out to be stone chips. Sticking out slightly from the arches means I’ve started getting stone chips along the side sills and lower doors. Maybe half a dozen or so on each side in a couple of months. Probably wouldn’t have been so bothered if it was an older car or a different paint scheme. Anyway something I didn’t consider.
I’ve since discovered that these wheels are also sold in an ET48 size, which would have been perfect and kept the tyres inside the arches. MX5parts in their infinte wisdom sell the ET40 version No idea why? So something to watch out for when buying third party wheels. I posted a similar thread on an American Miata forum. The feedback was that ET45 is about the limit before you start ‘coming out the fenders’, though some of them apply heavy camber and roll the wheel arches to fit even bigger and wider wheels.
On the plus side the Winter tyres have been a dream over the last couple weeks. Winter tyres make such a massive difference in snow/ice conditions, even more so than I expected.
No idea why? So something to watch out for when buying third party wheels. I posted a similar thread on an American Miata forum. The feedback was that ET45 is about the limit before you start ‘coming out the fenders’, though some of them apply heavy camber and roll the wheel arches to fit even bigger and wider wheels.