WHY do bigger alloys mean worse handling?

[Leon.]

I had read the original post but i had not read the 10 pages of dribble associated with it.

All i was saying is i disagree with the comment that a greater tyrewall is better for handling and i was giving him a reason why i thought this through my own personal experience.

Alan , are you stupid?

How do you know there are 10 pages of dribble, you didn't read them. FYI they are very informative. Don't be so ignorant.

If you can't be ar$ed to read the thread, don't post. It doesn't matter whether its a 1 page or 10 page thread. Don't waste people's time who have, and have then been able to contribute, or just to learn something they find interesting.

If you had read the 10 pages, you would have found the answers to your question(s).

From my understanding of actually reading this thread, and others similar, a tall tyre wall itself does not give a car better handling. Its all about how the complete suspension system was designed, and for the MR2 it was designed with a comparitively tall tyre wall compared to the likes of the RX-7, for example. If the MR2 had been designed with a short tyre wall, the other suspension components would have been slightly different to compensate.

Therefore, with a shorter tyre wall than stock on the MR2 you are compromising the suspension setup and so the car's handling won't be as good as it could be. Similarly, if you put taller than stock tyres on the RX-7, handling would also be compromised.

Note I am using the word 'handling' here, not 'road holding'. This has been clearly explained in the previous pages..... I have explained it simply here but there is a more indepth discussion if you can be ar$ed to go backwards and read it.

[RedWitch]

OK, let'e get back on topic.......

Suepension: TRD coilovers, wound pretty low and set at 100% hardness front, 60% hardness rear. No camber adusters fitted or geometry setup done yet.

Previous wheels tyres:

Front 17" x 7" Lenso 5KR with 215/35 Toyo Proxes
Rear 17" x 7" Lenso 5KR with 235/35 Toyo Proxes

The ride was very hard, skittish, oversteer, some tramlining. The rims DO look very good with the low/wide bands!

Current wheels tyres:

Front 16" x 7" Racing Sparco with 205/45 Toyo Proxes
Rear 16" x 8" Racing Sparco with 245/45 Toyo Proxes

I noticed an immediate improvement, handling much more responsive, slight oversteer, less hard (even with same hardness settings), no tramlining, not skittish at all. Although the rims look good they are not as asthetic as the 17's.

She's booked in for a full geometry setup (custom designed from Wheels-InMotion, thanks Tony! ) where I'll also have a set of front & rear camber adjust bolts fitted. I expect the before and after results to be stunning.

In summary, for me, there is simply no comparision between 16's and 17's for handling. 17's look better on the car but if you want to throw your car around the corners get a set of split size 16's

[RedWitch]

OK, let'e get back on topic.......

Suspension: TRD coilovers, wound pretty low and set at 100% hardness front, 60% hardness rear. No camber adusters fitted or geometry setup done yet.

Previous wheels tyres:

Front 17" x 7" Lenso 5KR with 215/35 Toyo Proxes
Rear 17" x 7" Lenso 5KR with 235/35 Toyo Proxes

The ride was very hard, skittish, oversteer, some tramlining. The rims DO look very good with the low/wide bands!

Current wheels tyres:

Front 16" x 7" Racing Sparco with 205/45 Toyo Proxes
Rear 16" x 8" Racing Sparco with 245/45 Toyo Proxes

I noticed an immediate improvement, handling much more responsive, slight oversteer, less hard (even with same hardness settings), no tramlining, not skittish at all. Although the rims look good they are not as asthetic as the 17's.

She's booked in for a full geometry setup (custom designed from Wheels-InMotion, thanks Tony! ) where I'll also have a set of front & rear camber adjust bolts fitted. I expect the before and after results to be stunning.

In summary, for me, there is simply no comparision between 16's and 17's for handling. 17's look better on the car but if you want to throw your car around the corners get a set of split size 16's

[Spacey]

thanks to all who've posted in this thread. Some really interesting and useful stuff!!

But alas I still have a question.

My car is currently on 17" wheels which, other than the increased firm ride, I find fine. That said I've never driven the car hard enough to actually get to the point where handling (in it's correct definition) or slip angels etc have come into play. For the road I much prefer the look of 17"s over 16"s.

Even though at some point down the line I plan to tart up the car with a body kit etc. I still plan to take it on a good few track days. First of all I want to improve my skill (or current lack of) at handling a car at speed and second I want to experience what the car can actually do. Obviously both of these are best done on track.

To avoid some of the issues around tyre wall size/stiffness when used on larger wheels I'm happy to buy a set of 16" wheels for track use. So to the question...When I get the suspension overhauled do I get it setup with the 16s or 17s on or does it even matter given the limited tuning potential? My overhaul will likely be a case of replacing top mounts, bushes etc and then fitting an entry level coilover pack.

thanks guys

Chris

[Leon.]

Chris, I could be wrong but I'll try and help......

It shouldn't make any difference w.r.t. whether you run 16s or 17s, or even 15s with the suspension mods you intend to do. You are only replacing like for like in terms of the way the suspension operates so it doesn't matter. You are only going to be changing the stiffness/flexibility of various parts. Tracking and those things don't come into it either as the hub never changes. It would matter if you were doing more substantial things like changing the actual setup from a macpherson design to a wishbone design for example, although this would involve expensive chassis alterations I'm sure, if you could even fit them....

Seeing as you aren't going to do this it would be fine to run whatever rims you want but obviously the 'handling' will suffer with 17s (and maybe slightly with 16s but I have no experience with them). AFAIK this cannot be avoided, just make sure you have the same rolling radius as stock and that's about all you can do.

Having said that, I believe some people have camber adjusting bolts (or whatever they are) so if your setup allows for these then maybe this is something you can tweek for the road and track setups?

It might be worth trying 15s and 16s when you get to using the car on the track to see which you prefer.....

HTH

[jonb-]

To answer in brief, and I still need time to write up my 15 vs 18 debate after my last trackday where i did 1/2 day on each, you'll not notice anything between the 16 and 17 in terms of enjoyment, especially if you're a trackday newbi.

You're better off spending your money on the best tyres you can afford and making sure your car is well maintained for the extra trackday stress.

Also, as you're local to me feel free to keep in touch as i'll be attending a fair few trackdays over the summer in my track turbo.

[Lauren]

Chris, I could be wrong but I'll try and help......

It shouldn't make any difference w.r.t. whether you run 16s or 17s, or even 15s with the suspension mods you intend to do. You are only replacing like for like in terms of the way the suspension operates so it doesn't matter. You are only going to be changing the stiffness/flexibility of various parts. Tracking and those things don't come into it either as the hub never changes. It would matter if you were doing more substantial things like changing the actual setup from a macpherson design to a wishbone design for example, although this would involve expensive chassis alterations I'm sure, if you could even fit them....

Seeing as you aren't going to do this it would be fine to run whatever rims you want but obviously the 'handling' will suffer with 17s (and maybe slightly with 16s but I have no experience with them). AFAIK this cannot be avoided, just make sure you have the same rolling radius as stock and that's about all you can do.

Having said that, I believe some people have camber adjusting bolts (or whatever they are) so if your setup allows for these then maybe this is something you can tweek for the road and track setups?

It might be worth trying 15s and 16s when you get to using the car on the track to see which you prefer.....

HTH

I disagree, fitting coilovers will change the geo so it will need to be reset. Changing camber doesn't have a mega effect really, Toe angles are what make the difference as a rule.

[Leon.]

Lauren, I meant that when adding coilovers you won't need separate settings for 16s and 17s, because it is irrelevant to the rim size, plus there are no real adjustments to be made except maybe dampness.

Right?

[Spacey]

OK fair enough. I understand the logic as there's nothing that can be adjusted or set differently for a different wheel size.

Essentially I just want the car to look nice on the road and still offer me lots of fun on track!

[RedWitch]

Lauren, I meant that when adding coilovers you won't need separate settings for 16s and 17s, because it is irrelevant to the rim size, plus there are no real adjustments to be made except maybe dampness.

Right?

There are something like 14 angles to consider with a geometry set-up, so therefore ANY change, whether it be wheel or tyre sizes will have an impact on the geometry.

[jonb-]

Red,

How is she now you've been to wheels-inmotion? Can you show prints of what he did to compensate for your various setup quirks?

I'm trying to head down their myself soon for an aggressive track setup now i've all my components install.

Everyone,

I did 1/2 day on stock 15s and 1/2 day on 18s on my last trackday, i'll write up something soon i promise!

[BenF]

I did 1/2 day on stock 15s and 1/2 day on 18s on my last trackday, i'll write up something soon i promise!

Heh - you'll notice a much bigger difference in the wet than the dry with that comparison. The lower grip will exaggerate the differences ..

[jonb-]

I did 1/2 day on stock 15s and 1/2 day on 18s on my last trackday, i'll write up something soon i promise!

Heh - you'll notice a much bigger difference in the wet than the dry with that comparison. The lower grip will exaggerate the differences ..

I was more concentrating on the breakaway (handling) and slide characteristics of the low vs high profile tyres than anything else as the common comment with big wheels is "i'll snap before you realise it".

To sum it up in a few words, even with the tyre differences i found the 18s almost as controllable as the 15s and had a good laugh powersliding both out of the slower corners. Ultimately the 18s did break with slightly less warning but there really wasn't as much in it as i expected from all the comments here.

I'd happily wear 18s on the road again, however for my trackcar i've opted for 16s.

[Tony.]

Lauren, I meant that when adding coilovers you won't need separate settings for 16s and 17s, because it is irrelevant to the rim size, plus there are no real adjustments to be made except maybe dampness.

Right?

There are something like 14 angles to consider with a geometry set-up, so therefore ANY change, whether it be wheel or tyre sizes will have an impact on the geometry.

Wise words indeed....

[Si_Crewe]

Very interesting thread and a subject I've had quite a bit to do with.
I had a dune buggy which was built with adjustable rose joints on the double wishbone suspension so I have been able to play with the settings quite a bit.

The first thing which a lot of people don't understand is the idea of weight transfer in corners.
Equal length double wishbones (as found in several "high performance" kitcars) are *the* most dangerous thing out there.
They're fine in a straight line but your car wants to roll as it goes around a corner. If both wheels are forced to remain perpendicular to the ground then most of the weight is on the outside edge of the outer tyre. If anything goes wrong the most likely outcome is you'll end up with the car on it's roof.

Mcphereson struts were designed as an "economy" suspension design but they actually work pretty well.
Systems using either unequal length wishbones, single wishbones or Mcphereson struts allow the cars body to roll *and* still press the outside wheel into the ground evenly. Sure, the inner wheel isn't doing much but the outside wheel is much more evenly loaded.

That's where you start to get problems with low profile tyres.
A tyre with a high profile will actually roll as the suspension position changes.
When you travel in a straight line the contact patch is the centre of the tyre.
When lateral forces build up (as in hard cornering) the tyre wall flexes and the tyre will actually curl slightly. It does this rather than breaking grip.
A low profile tyre can't curl in the same way so the cornering forces load up until traction breaks.

The other thing which escalates this problem is also to do with the tyre walls.
When you steer suddenly the wheel will actually move about within the tyre. It can do this because the tyre wall is more flexible.
In a low profile tyre the wall is more rigid. This gives you sharper handling (as well as more bump steer and tram-lining) but it also means that the car is now capable of sharper steering manoevres which, in turn, load up the tyres faster and cause slides with less warning.

I found a cracking ebook about suspension setup on the net somewhere. Unfortunately, I can't recall the website. I did print it all out though so I'll post a link to it when I get home.
If any of you want to look for it yourself it was called something like "A guide to suspension tuning in small vehicles", it really is a bible for suspension tuning. And it's free.

Beyond that, the only other point worthy of making is regarding "on the edge" handling...

It's all very well to say low profile tyres lose traction only in extreme conditions and if you're driving hard enough to cause it then you will be concentrating hard enough to catch it.

Erm, no.

If I'm blasting down a country lane on a sunday then fair enough. I probably will be paying attention.
If I'm driving home from work on a rainy winters night when a car pulls out in front of me or a child runs out into the road then I could really do without the added worry of whether the back end is going to let go as I try to manoevre safely.

Each to their own but I'd never dream of putting wheels and tyres on a car which could make it more dangerous to drive, even in the rarest situation.
Aside from that, after spending my time crashing from pothole to pothole in our glorious road network, I think higher profile tyres are preferable.

[Tommo-GTS]

Hi everyone,

this is my first ever post - on IMOC, how about this? Toyota spend 5 million pounds on research and developing the mr2 , optimum handling, (brakes suspension) etc, etc, whats wrong with the original setup????, surely they tried different sized wheel , tyres, suspension in developing the car. I am of the personal opinion - keep it original. - or have toyota(you know - the company that made/developed the car in the first place) got it all wrong?

[jonb-]

Here we go.

Firstly, welcome to imoc.

Secondly, this is from the mr2 owners club by "seen-my-keys". It should be a sticky. Edited slightly for topic.

==

An MR2 is the mid engined sports car, designed for joe bloggs.... So it's full of compromises to make it appeal to a wider as possible audience, inlcuding the factory 'suspension' package.

One aspect of designing the MR2, is to make it appeal to as many people as possible, to increase profit from sales. (obviously!)
As opposed to very niche market cars like supercars, where they make fewer compromises, and focus more on suspension / geometry features etc.

Bear in mind that the total package of the MR2 is not just suspension, there are many other non perfomance factors involved too. Things like price, appealing to a target demographic for buyers, safety, comfort, etc.
These are factors which undoubtably affect the suspension package of the MR2.

==

Toyota designed this car to a budget and to be comfortable. Sure, we mess up a lot of carefully planned out geometries by playing with suspension and tyres but toyota DID NOT GET IT RIGHT from a PERFORMANCE point of view.

[Si_Crewe]

Sure, we mess up a lot of carefully planned out geometries by playing with suspension and tyres but toyota DID NOT GET IT RIGHT from a PERFORMANCE point of view.

That's a bit unfair isn't it?
Kinda like saying that they screwed up from a load-carrying point of view by not making it an estate car with a 15ft wheelbase.

[jonb-]

Maybe I should have said from an ultimate performance point of view.

The mr2 was designed to be a quick car, but there's plenty more to come from it than soft high suspension and silly 15" wheels.

[ENSMR2]

Great info here