Tyres and impact on lap times

[YanMa YatTai]

There is an interesting thread on Vmax at Wakefield where Guran posted a graph of his tyres and lap times with speeds at various points at Wakefield.
http://mx5cartalk.com/forum/viewtopic.php?f=68&t=60770

The graph leads me to this question - how much of a difference have tyres made on your lap times? Obviously we have Guran's data, but interested to see others as well.

So please tell me:
Track:
Car:
Old Tyres:
New Tyres:
Time Difference:

Please report differences in times due to tyres only, no other mods between tyre changes. Yes I know there are variables such as the conditions on the day, nonetheless this data would be interesting to know.

[Trackphotos]

Track: Lakeside
Car: Stock NB8A
Old tyres: Yokohama A.Drives
New tyres: Federal 595 RSRs
Difference: 2.3sec, down from 70.0 seconds to 67.7 seconds. That being said, the 70.0 was my first time at the track, and I only ran 3 sessions. The 67.7 was after 8 sessions on my second time at the track. My first flying lap on the new tyres was a 69.3, immediately followed by 4 68.8 second laps in the same session. Basically, immediate change without any 'practice gains' of 1.2 seconds.

Side by side comparison here:

[Magpie]

I also think that you need to consider g force in the corners as this will give an indication of the grip of the tyre. If you do not have a way of recording g force then it can be calculated mathematically. The question should be what tyre has the greatest g force in a corner without loosing grip

Hopefully in a few weeks I will be able to post some data, as long as the car is track ready

[brendanstacey]

There are many other factors when judging tyre performance such as responsiveness and how it reacts past its max force output.

That said max sustained g-force (aka skidpan/roundabout test ) is a pretty good indicator of a tyres performance.

[NitroDann]

The way grip drops off as slip angle moves past its optimum, and how high it's optimum slip angle is will determine how hard it likes to be dríven and how forgiving it is when mistakes are made, these are also very important.

Dann

[mazmad]

Depends what you are after. But if it is faster lap times - then lap times not g forces are the best guide. You might have a tyre which has generates higher g's, but has greater rolling resistance and so is slower at speed. Hence I think gurans approach makes sense, looking corner by corner but also at lap times.

Bear in mind too that one tyre might suit one car but not another due to weight, camber, and even driving style.

[YanMa YatTai]

^ totally agree with you. Agree also on too many variables for any conclusions about "best" tyres - which is why I am interested in people sharing their experiences.

So please keep the feedback coming. We may not be as thorough as Guran on analysing data though! Hey he may be a stats nerd, but look at those lap times!

[Charlie Brown]

Lap times aren't a good comparison unless the test is done on the same car on the same day with the same temperature and atmospheric pressure.

Hot days and low atmospheric pressure can effect Wakefield times by a second or more a lap.

You don’t say if you’re after data for road tyres, S-Spec or R-Spec tyres??

If you’re after R-Spec data, then from experience Kumho V70a’s are a second a lap quicker than Dunlop D01J’s. The Kumho’s are quicker again by 0.3 – 0.5 seconds when there is almost no tread left on them. They wear quickly, around 700 racing kilometres will see them gone.

If you’re after road tyres (not S-Spec’s) then I’ve found Michelin Pilot Sports hard to top, both in the dry and especially the wet. They were two seconds a lap faster than Toyo T1R’s but that wasn’t on the same day.

Why not use Tirerack’s site and look at their comparisons? Though not tested on a MX-5, it still gives you a good idea how the tyres perform.