Trackcar + New Tyres = Understeer

[frog_a_lot]

Alright so, I have a NA MX5 racecar. For those playing mainly in NSW it is the old white hydrawash car.

It has been running Dunlop DZ03s in Hard compound previously. I didn't feel like spending around $350 per tyre, so i thought I would try a set of Federal FZ201's in Medium. Everything I researched on the FZ201s said how great they where, better than the R888s and almost as good as the DZ03s and those tyres.
I kept the same size 205/50/15.

I have now done 3 trackdays on them, 2 at wakefield park and 1 at EC South circuit, and have been much much slower. My old PB at wakefield is 1:13 and the best i could do on new tyres is 1:16. At EC South my PB was 1:06 and the best I could do was 1:09. Both those PBs where done on a set of almost bald DZ03s. The same car on a set of decent DZ03s has done a 1.10 at wakefield with a better driver. Inbetween running the 1:06 at EC and running the 1:09 was about 3 weeks and nothing was changed except for the tyres.

I did the usual tyre pressure adjustments, started high and the gradually worked down and it provided no results, no improvement at all. I then tried changing the stiffness of the shocks via the little adjustment knob on top of coilovers (G4 coilovers), to try and get some more heat into the front tyres, this provided no real results either.

It seems like the tyres are just not getting hot enough to provide any grip at all and so they are understeering horribly and at times oversteering when putting power down.
I would prefer not to change the suspension too much since the previous owner had it set up quite nicely (for the dunlops at least)

Any ideas or hint on what the hell may be going on? Or is it just that the Mx5 really doesnt like these tyres and there is nothing that can be done?

Cheers

[Tony]

A review of temps across the face of the tyres will give some clues as to how the suspension setup and tyres are working together, and may be a good place to start.

[hamx5ter]

New tyres are bound to have less grip than bald ones; they have less surface to grip with.

If you are missing grip, perhaps your tyre pressures are too high to start with. The tyres need both the right temperature (to go sticky) _and_ the right inflation (for the right profile) to work as they were designed, and that will take some playing with (which you are already doing I suppose). Too high and the tyre will be greasy when it heats up and not show the entire surface to the road.

+1 on measuring the temperatures across the face of the tyre. Also, if you've done 3 trackdays with it, you should be able to look at the wear on the tyre to know how it is set up, which should give you a little more info..

When you say it over / understeers, it will help the pundits here if you tell them _when_ it does it; on entry / exit and how much, etc. Also what pressures you're running and what effect the various adjustments had.

If you are not getting heat into the tyres, perhaps start at a lower pressure; the sidewall flex will heat up the tyre quite quickly. Also, you need to drive harder

[bensale]

From what I know about the FZ201s the mediums are quite hard and durable for a medium and need more effort to heat them up and are suited to heavier cars.. You might need to overdrive them, really throw the car into corners on the warm up lap and work the brakes hard to get heat transfer and set them with really low pressures to get something out of them.
The softs are a lot softer than the mediums and should be more suited to an MX-5. I have a set of them to replace some Kumho V700s and will be very interested to see how they go.

[frog_a_lot]

Tyre pressures - I started at around 34-35 hot and went all the way down to around 24 hot, I was not willing to go any lower. The difference between 35-25psi was very minimal in terms of grip.
Temp - Need to sort myself out with a guage, but they seemed to be heating fairly consistant across the tyre at around 28-30psi hot.
Wear - The tyres barely even look like they have weared at all, which points to the fact of lack of heat/grip, but the little wear they do have shows fairly even across the tread with a little more on the inside but not much, will try and upload a pic tonight.

Understeer - Corner entry is a very big problem, coming into the first corner at wakefield(not the kink) i find myself pushing straight through it and on the outer ripple strip or grass with no turn in if i enter the corner with any speed at all. Similarly going up the hill at wakefield into the top section There is no turn in grip on the right hander at the top, i find myself just understeering straight to the outside.

There is also some oversteer present, mainly at EC South, i used to be able to take the first corner basically flat and flow nicely to the right hand of the track (pit exit) and just power out, now if i try that i find myself with the back end breaking loose and having to back right off to not spin/slide. Going through the chicane up the hill it is also quite tail happy.

Not Happy Jan

[project.r.racing]

did it get a wheel alignment after the new tyres?

[ja9]

For mine there are two things you need to do.
1. Check the date of manufacture; found on the side wall. Reason this is important is I once was sold a brand new set that where sitting there for years but looked like new. A big waste of money, I persisted with them eventually righting my car off and 30k down the drain.
Lesson learnt, everytime I buy new tyres I look for the date of manufacture. Won't touch them if they are too old.

2. If everything is ok with the date of manufacture (ie no too old) and you have played around with tyre pressures and shocks as you have stated then the only thing left to do is you must change the front set up. What settings you need is something that you will find out by using the "suck it and see" method. A little costly but the best way. Most people have the best intentions and are happy to help but rarely do you get the correct answer. Too many variables betwen cars etc. By all means talk to as many people as you can for their advise and go from there as to what is right for you, your car and your style of driving.

You say you don't want to deviate too much from the previous settings so why don't you write them down before you make any changes. If you're not happy with your changes you can always go back to your previous settings (once you have bought a new set of Dunlops).

Changing brand of tryes is something most of us do because we have heard about the elusive 1 second but rarely is it that simple.

Regards - John

[Smokinscotty]

I thought the 201s were a fairly new tyre.. Id check with Federal Motorsport Tyres HQ and ask them for advice on getting them working properly.
The Dunlop guys used to set people straight quite often to help them enjoy their purchase, im sure Federal would do the same.

[tank]

I had a set of Toyo R888s and they had no grip for the first 2-3 track days. You need to wear-off the tyre mould release agent first. Depending on the number of heat cycles, semi slicks are quicker in the dry with less tread on them (ie. almost bald).