How to ruin the handling of an MX5.by Norman H Gar

[hks_kansei]

The contact patch of a 215/45/16 is the same as a 185/60/14 just turned 90 degrees..Tyres float the weight that is on them according to how much pressure is on them..Wider tyres do not give more grip but do add a lot of unsprung weight..According to Norman...

A wider tyre may not give more grip overall, BUT due to the change in shape of the contact patch it may well give more grip in a different situation.


take for example they tyres you've mentioned above.

The 185 has a narrow, but long contact patch. This would likely provide more grip in fore and aft movements (accelerating and braking)
The 215 has a wider, but short, contact patch. THis would likely provide more grip is side to side motions (cornering)

Overall grip may be the same, but it could likely change where that grip is of most use.




Then there's also the difference in how the tyres react during corners, the 185 may have a higher tendancy to tuck under and corner on the sidewall/shoulders. Where the stiffer (smaller) sidewall of the 16s may resist enough to keep the contact patch more constant.
And of course they're both affected by wheel alignment.

etc, etc.





Basically, there's no 100% perfect modification or setup.

The stock MX5 is a very good COMPROMISE of all these settings.

[Dan]

Style bars run across the car from seat belt tower to seat belt tower up high where the car flexes the most, he like the single hoop from racing beat, don't NB8B's have a low down bar across there..Power is covered in the book but that is clear cut, handling is not.Don't we all want to make our cars handle the best for the least amount of money..sell those strut tower braces to people who like the look of them because they will slow you down...

I think it is ridiculous to claim that modifications don't do anything to a car's performance. Guran is a phenomenal driver, and he runs rings around anyone else in a stock mx5, but the simple fact is that he doesn't hold lap records for every circuit he's been on. Compare his time at Philip Island with Lightyear's time in the turbo NA6, for example. Lightyear is about 18 seconds quicker. Ben Sale does ~2:01 with Bilsteins, Koni springs, Whiteline adjustable sway bars, full exhaust system, NA8 brakes, chassis stiffening and wider, grippier tyres.

Again, I don't want to rain on Guran's parade, he's a mentalist in a stock NA. But to claim that mods are detrimental to a car's performance is stupid.


Also, if bigger, wider tyres don't do anything, then why aren't Lambos running 185/60/14? Their tyres are around the 300mm wide mark.

The point is that mods need to be added proportionally not that mods don’t improve performance.

Those 300 tyres on a stock MX-5 will make it into a dog but on a time attack car it might be perfect.

[Patrick Bramston]

We are not talking about power here... A lambo weighs twice as much as an MX5 and can create a much bigger contact patch... Put 225 wide tyres on 9 inch rims on Gurans car and he will be slower because they weigh SO much more.. Unsprung weight is SO important.. Those daisy wheels only weigh 5.5 kilos....

[lee]

We are not talking about power here... A lambo weighs twice as much as an MX5 and can create a much bigger contact patch... Put 225 wide tyres on 9 inch rims on Gurans car and he will be slower because they weigh SO much more.. Unsprung weight is SO important.. Those daisy wheels only weigh 5.5 kilos....

I wasn't suggesting putting 300mm wide tyres on an NA, they'd struggle to fit more than anything

The daisy wheels are light for stock wheels, but there are many lighter and bigger wheels available. I've bought a set which are a full inch wider and a full inch larger diameter, and they weigh 1.2 kilos less than the daises. The wheels I currently have (NB8A stockies) are .2kg heavier, but this is probably offset by the lighter, lower profile tyres I can run. A lot of people run 6ULs, which are an inch bigger in diameter and 2.5" wider, and they weigh about the same as the stock 14"s.

[CheyneX5]

How about we all agree that the MX5 is a brilliant car. It handles well in both standard and modified form.

Some mods might not produce a better result on paper but they can certainly give you the feeling you are going faster. Take MX5 Mania's CAI for example... It sounds like you have trapped hell in the engine bay but you are not really adding much power at all. The most important thing is the smile it delivers and the feeling of going faster because of that noise.

Same with Strut Braces. Sure they probably don't do a whole lot in an Mx5, but it's all the little things you add, that make one big change. I agree that a hinged brace will do little to nothing. But a solid brace (i.e. carbing) does improve the feel, this is what is most important.

Most simple mods do not have to make the car go faster or show better results on some graph, if it feels better to you and it enhances your enjoyment of driving the car, then do it!

Sent from my iPad using Tapatalk HD

[lightyear]

We are not talking about power here... A lambo weighs twice as much as an MX5 and can create a much bigger contact patch... Put 225 wide tyres on 9 inch rims on Gurans car and he will be slower because they weigh SO much more.. Unsprung weight is SO important.. Those daisy wheels only weigh 5.5 kilos....

By what I read, I should be slower too. But I'm not... On a stock motor mx5 (what I have), the best is supposed to be a 195/50 on a 7" rim. Wider tyres take longer to get up to temp, they are heavier, more aero drag, more friction drag, cost more. But yet they seem to be getting the job done. How much faster/slower will my car be with smaller wheels/tyres? Only way is to try it. I have tried in the past, but never been able to due to one thing or another.

[deviant]

Style bars run across the car from seat belt tower to seat belt tower up high where the car flexes the most, he like the single hoop from racing beat, don't NB8B's have a low down bar across there..Power is covered in the book but that is clear cut, handling is not.Don't we all want to make our cars handle the best for the least amount of money..sell those strut tower braces to people who like the look of them because they will slow you down...

Does the car really flex the most there? The seat belt towers and that rear bulkhead they sit on contain a lot of metal. I did a few hundred laps in my stock standard NB8B before I fitted an MX5+ tall boy and I found absolutely zero difference with it fitted.

In the NA I used to have I could always feel the twist coming from further forward in the car....in the big hole we sit in. The NB has a load of under body bracing from factory which seemed to eliminate this feeling of twist in the cockpit.

NB8B has a front strut tower brace, a pressed steel 'panel' that bolts under the cockpit and under the rear end is a 6 point tubular brace...this is just made up of squares, would be interesting to weld some diagonals in to it. There is no rear strut brace and no bracing inside the cockpit.

[project.r.racing]

A lambo weighs twice as much as an MX5 and can create a much bigger contact patch...

Again with the apples and oranges...

[Patrick Bramston]

He is not saying the seat belt towers flex the most but to run a single hoop across can add some stiffness to the inherant problem any convertable has.. He even says the weight penalty of a hardtop is made up for by the added stiffness it creates which I know people here, disagree with.

[NitroDann]

I might finally have a say here.

A car is a SYSTEM.

It isnt one object but a system that has many parts and each have a role.

In stock form, with stock tyres, they have enough grip to cause enough roll on the body that the stock camber curves at stock ride height with stock spring and sway rates, works spot on, the tyre sits flat and evenly deformed across the tread.

Adding just stiffer swaybars means the tyre will not sit flat, it will be riding the inside edge, all else being the same.

However if you add more grip and more spring/bar, we have a new system that works properly all told, and because we now have more grip our lap times are reduced.

This is the point being missed by the author/book.

He forgets to mention that hes talking about individual mods in a complex system.

Dann

[JBT]

I remember back to our NA8. Bought and fitted a "shock tower" brace and I reckon it had no effect. Bought a "racing beat" type style bar that attached to the seat belt towers and I felt that it stiffened the body up significantly.

[Hjt]

Various people have seen improved lap times with the hardtop removed, but again it's a weight and mass issue.

Those daisy wheels only weigh 5.5 kilos....

I'm interested in the weight difference of tyres alone, unsprung, of a 185/60/14 compared to a 205/50/15 in the same compound.

[NitroDann]

Also regarding hardtops/rollbars stiffenning the body, there a big difference between actual stiffness and perceiced vibration damping.

Dann

[Patrick Bramston]

185/60/14 weighs 7.9 kilo's..205/50/15 weghs 9.7 kilo's...All in the BOOK..

[hks_kansei]

Also regarding hardtops/rollbars stiffenning the body, there a big difference between actual stiffness and perceiced vibration damping.

Bang on.

for starters, it's attached with clips and clamps that are designed to have a degree of movement.
the rear catches are simply a slotted plate designed to allow fore/aft and up/down movement.

And even more so, you can easily twist a hardtop by a few mm either way without much force.