Need some help choosing some new wheels, will they fit?

[Okibi]

Wun911 has received a short term ban for a racist comment. I will not tolerate racism thinly masked as humour, if you want to draw stereotypes of people based on their race this isn't the forum.

The forum is about MX-5s and not some klan meeeting.

[meanmx]

Ok now for the only really useful comment in this whole messed up thread.

I just gave Ozzy tyres a call and confirmed that their 17x7 are a 35 offset. I'm a bit hazy on the oem specs but I think they are 17x7 with a 40 offset. If that's right then these will be almost an exact replacement although sitting 5mm towards your guard more. Anyone can feel free to correct me at this point.

Now the 8.25" wide ones are a different story. Here's where things got a little difficult on the phone. I think from what he was saying the 8.25" come in 20 offset. Going on the previous assumed oem 7" 40 offset that would mean these wheels will sit 33mm odd further towards the guard. Again this is not really my speciality so if anyone wants to correct please feel free. I think this offset will be too aggressive for your car but it depends what you want. Personally I think for a DD with no intention of doing guard mods or rolling then a 17x7 with a 20 offset should be fine.

As a side note. If those 8.25" wheels came in a 35 offset then they could be ok as well. About 18mm towards the guard and 8 mm more towards the inside of your wheel arch. Hope this helps.

[Okibi]

... 8.25" come in 20 offset. Going on the previous assumed oem 7" 40 offset that would mean these wheels will sit 33mm odd further towards the guard. ...

I think my Konig Spooled are 15x8 20mm, with Yokohama Advan A050 205/50/15 the tyres just rub on the metal edge of standard NB guards (front and back) under braking and against part of the liner in the front wheel arch. So if Ben's calculations are correct then the your tyres would stick out 3.3mm more so might just fit inside rolled guards with -2" camber.

Have you searched clubroadster, someone these might have already tried?

[Jeo]

He PROVED that some 17's aren't too big/heavy. He didn't have to denigrate and offend followers of the Bible or the Quran to support his argument as Simon did. And that is my issue with Simon.

"Proved" is a strong pretty strong word. As proof of the opposite I submit the following thread again; Unsprung Weight Links. The interesting links talk not only about unsprung weight, but rotational mass. Even if two wheels are identical in weight, the larger wheel will have more of it's weight further away from the hub causing a greater effect on rotational mass.

Obviously you have a problem with me so take it up via PM.

No problems with you FFG, you generally seem like a pretty cool guy.
Where I pointed out a fallacy in your logic was when you attacked Lokiel for comparing 'blind faith' to the bible/koran, yet you commended Wun for something way heavier. That fact that you know Wun AFK might make the humour better in your mind, but that doesn't translate well to a forum.


Back on topic

17x8.25 +0? What size tyres?

Will probably "fit" but unless you're in love with that particular wheel, I'd be looking elsewhere.
Stock wheels on an NB were either 15x6 +40 or 16x6.5 + 40.

8" wide +0 offset will stick out 69mm further than the 6" wide, and 62mm more than the 6.5" wide.
Have a play here to see what your options are.

Meanmx - Your measurements are spot on.

[meanmx]

I'm not wishing to add to an argument or to sling sh*t but I do have a couple of questions after reading that link that Jeo kindly supplied us.

Ok, first I understand that less weight is better. But when you split that up into how much the wheel weighs and where that weight is on the car things get more complicated. So if you are talking an extra 2kg per corner which is probably the difference between equally manufactured wheels of 15" and 17" are you really going to notice that much significant difference on the road where you shouldn't be driving at 10/10th's anyway? How do you measure that difference unless it is completely dependant on how that one person feels. I had for a short period of time 17" chrome wheels on my NA that I borrowed, and this is where I completely understand what you guys are talking about. The handling was completely changed for the worse, however going from the stock 14's to normal 17's I was ecstatic with the extra grip on the road, better turn in, and the feeling of being more connected. To me I felt very little detrimental difference which I guess is why I'm still running 17's (although not chromies). How do you judge that point at which you tell someone it wrecks the car, as I never felt on the road that I was impacted and certainly wasn't left behind on any mountain/ coast runs as other people can testify.

The second part of this question is in regards to where that weight sits. From what I can gather the wider a wheel is and the lower the offset then the more detrimental to a cars performance it is. For example a 15x7 40 offset would be better than a 15x8 20 offset which would in turn be better than a 15x10 20 offset. This is because the weight will be pushed further out from the body which means the suspension can't deal with it and it places more strain on the drivetrain thereby affecting performance. Is this correct? At what point is the extra grip due to wider tyres offset by the extra rotational mass that is now sitting further from the hub?

Why aren't most of you racers running 14's? Is it brake related or tyre choice related? Reviewing the information it would seem that a light weight brake setup that will fit under a 14" lightweight wheel would be the goal. Is it lack of availability and if so then how do the mini guys do it?

Why is it that no modern designed sportscar have these sizes stock. Admittedly not many are as light as an mx5 but there are still several cars almost as light. Think Porsche Boxter, Lotus Elise, Toyota 86, KTM X-Bow. If it is brake related as some people think then surely the manufacturer feels that brake size is more important than wheel size. If it is a marketing strategy then surely it is just as important marketing wise to have the best 0-100, 1/4 mile, lap time as well. All I can think is that the manufacturers of these performance cars must feel the compromise is worth it.

I'm not trying to start something or insult anyone. If anyone feels insulted then I apologise right now to them. I just want to increase my knowledge after reading all those links that Jeo posted. Ultimately I will never be swayed into a wheel choice by anything that anyone says here unless I decide to go racing but for street use I will buy whatever I feel like as long as I feel that it is right for me. I was contemplating going 16's to get that whole JDM thing happening a little more but I'm now pretty sure I will get 17's again as I feel the look is right. Hoping that the information posted will be informative for myself and others providing people can stay away from personal opinion and forum heresay. I'd love some genuine facts rather than you should run this because it's the best.

[Okibi]

...going from the stock 14's to normal 17's I was ecstatic with the extra grip on the road....

Could you attribute this to different and or fresher tyres?

[fastfreddygassit]

Obviously you have a problem with me so take it up via PM.

No problems with you FFG, you generally seem like a pretty cool guy.

I am.

Where I pointed out a fallacy in your logic was when you attacked Lokiel for comparing 'blind faith' to the bible/koran, yet you commended Wun for something way heavier. That fact that you know Wun AFK might make the humour better in your mind, but that doesn't translate well to a forum.

Point taken and understood. His humour is occasionally questionable.

To the question at hand, when my SE was at stock height, I fitted 25mm (1") spacers all around.
The stock '05 Racing Hart is a 17x7 with a 40mm offset.
So, that means with the spacers, these wheels have become a 17x7 with 15mm offset (is that right?)
Anyway...
With stock suspension, the rears would scrub on the guard with big bumps, but the rear guard has a MASSIVE lip, so I rolled them and no problem.
The fronts would scrub the guard and guard liners with big bumps.
I have since lowered the car considerably. The rears still have great clearance but the fronts required rolling and a slight pump. The problem is the guard liner.
It scrapes with large bumps. I don't want to remove it (yet) so it is still a work in progress.

and because I am FFG, I'll just quote the following:

.....I've just bought a set of 16x7 Enkei SC-14 rims since I REALLY hate the harsh ride of the OEM rims.....I think 15" rims look too small and "4 wheel drivey" on an NB without lowering it but 16" rims look about right. Unfortunately 16" tyres tend to be more expensive since there are fewer options available.

Just sayin'.........

[Okibi]

... extra grip due to wider tyres...

Wider tyres don't always mean more grip. Putting it in the most simplistic sense, if you double the amount of tread contacting the road, you half the amount of pressure per square CM the car is pushing down on the rubber to make it grip the road surface. I don't think there's any optimum as this would change depending on the type of tyres, how soft the rubber is, current weight of the vehicle and road surface. etc.

[Jeo]

In the grand scheme of things, it probably doesn't make a great deal of difference, no. A full tank of fuel compared to a mostly empty one would probably have a more noticeable difference on performance than changing between a set of similarly weighted 15's or 17's.

Why don't new cars come with smaller wheels? I'd wager a decent chunk of it is marketing. Why would a new HSV GTS run 20" wheels when the V8 supercars run 17's? People like having big wheels. They see bigger numbers as an upgrade.

As for things like the boxster, elise, etc; breaks, total car weight, total car size, tyres, aero, merketing, etc. I don't profess to know what works for them as I have no experience with them. What I have done however is talk to people significantly faster and better educated than me and the generally accepted consensus is that a standard-ish NA/NB will perform better on a 15" wheel than a 17" wheel, all other things being equal. Ultimately thought if you're happy with what you've got, that's great; if you're not happy, change it. I know I'd be disappointed in the forum if I popped up saying I was thinking about running 17x8.25 +0 wheels and someone didn't question the handling implications.

I was always told that you pick your tyre size first, then your breaks, then get the smallest wheel that fits both.
I moved from 14x7 to 15x8 because it's easier to get tyres for them and 15x8 are pretty easy to come by. In a perfect world I'd love some light 14x8 or even potentially 14x9, but 6UL's are comparatively cheap and tyres are plentiful.

[meanmx]

...going from the stock 14's to normal 17's I was ecstatic with the extra grip on the road....

Could you attribute this to different and or fresher tyres?

Nope, I went from Bridgestone G3's 185(I think that's what stock is?) to Nexan 205. To me the stock setup seemed to have the arse end step out to readily in enthusiastic driving and while easy to control, it wasn't the point. Before anyone questions, yes I did have a good alignment. With the extra grip from the 205's the car felt more planted even when adding a forced air intake . Again this is just seat of MY pants and in no way a confirmed fact

[fastfreddygassit]

Putting it in the most simplistic sense, if you double the amount of tread contacting the road, you half the amount of pressure per square CM the car is pushing down on the rubber to make it grip the road surface.

Yup, but you have doubled the amount of tread contacting the road, so that cancels out the halved pressure.
So you could say that basic grip (friction) is independent of area. It only needs a normal force and a CoF.
But tyres aren't simple with the most obvious point being that tyre rubber is adhesive (especially when at optimum temperature), so if you double the area you double the amount of adhesion. So wide tyres do have more grip than thin tyres. It must be noted that wider tyres will take longer to heat up and will also offer more rolling resistance.
Then you have the shape of the contact patch, which for wider tyres, is supposed to provide more lateral grip.
and it goes on...........

back on topic.

[hks_kansei]

They had it right back in the 40s.

19x3 with a -70 offset.
And crossply tyres.

[meanmx]

Why don't new cars come with smaller wheels? I'd wager a decent chunk of it is marketing. Why would a new HSV GTS run 20" wheels when the V8 supercars run 17's? People like having big wheels. They see bigger numbers as an upgrade.

As for things like the boxster, elise, etc; breaks, total car weight, total car size, tyres, aero, merketing, etc. I don't profess to know what works for them as I have no experience with them.

The HSV runs 20's with a bigger rear tyre because it becomes about straight line speed and brake size. More grip the faster time. However HSV's aren't really in the same category as what we are talking about. Ford also went and put a wider rear tyre on the back of it's GT to help harness it's power and it worked. I guess size of the rim comes down to brake size on these cars though, as you need a lot of brake to pull them down.

I would have thought with the other cars that if wheel size led to a large deficit in it's times then that could be more detrimental marketing wise.

What I have done however is talk to people significantly faster and better educated than me and the generally accepted consensus is that a standard-ish NA/NB will perform better on a 15" wheel than a 17" wheel, all other things being equal.

That is generally the smartest way to do it. I'm just curious if it heresay or proven fact. Also whether the evidence is accurately gathered. Also this is more track related than road obviously. I feel that driving courses/experience would probably help far more than swapping rims

I know I'd be disappointed in the forum if I popped up saying I was thinking about running 17x8.25 +0 wheels and someone didn't question the handling implications.

I couldn't agree more. However when terms like wrecked get thrown around they often do more to alienate those posters or makes others hesitant to post their experience regarding other sizes (whether it be 14,16, or 17)

I was always told that you pick your tyre size first, then your breaks, then get the smallest wheel that fits both.
I moved from 14x7 to 15x8 because it's easier to get tyres for them and 15x8 are pretty easy to come by. In a perfect world I'd love some light 14x8 or even potentially 14x9, but 6UL's are comparatively cheap and tyres are plentiful.

That is excellent advise especially with regards to track cars. With regards to road cars I prefer to stand and gaze lovingly at how well everything is proportioned (again this is for me only but some people may share my opinion). I figured a lot would come down to economics and that is fair and reasonable. Why wouldn't you want lighter 14x7 in a perfect world? Wouldn't running 14x9 be the equivalent of running a narrower 16 as far as the rotational mass being pushed out being bad for handling?

Thanks for a very informative post Jeo. I appreciate the well thought out comments regardless of whether I agree or not.

[meanmx]

They had it right back in the 40s.

19x3 with a -70 offset.
And crossply tyres.

That's awesome Nick

[Okibi]

Interesting question about other makes/models. Here a few where you'd expect grip to be more important than looks. Obviously different weights/power and budget.

Lotus Exige and Exige Roadster Front 205/45 R17 Rear 265/35 R18
Lotus Elise 16" Front 17" Rear
Ariel Atom 195/50R15 Front and rear
Caterham superlight 13" Black Aluminium cast centre, spun aluminium rims, Avon CR500 tyres
Caterham CSR 15" 10 Spoke Caterham Anthracite wheels. Front 6.5", Rear 9.0"
Caterham Roadsport 14" alloy wheels
Caterham SP300R ATS centre-lock Formula 3 wheels 9x13 and 10.5x13
Koenigsegg CCXR and CCR Front: 19" x 9.5" (255/35) Rear: 20" x 12.5 (335/30)
Radical SR4 CS cast aluminium wheels - 7" × 13" dia. front and 9" × 13" dia. rears.
Radical SR3 RS centre lock, cast aluminium wheels - 8" × 15" dia. front and 10½" × 16" dia. rears