Considering these for trackday use.

They will see many heat cycles, thus I tend toward the r888, but the more forgiving handling of the Yokohama is tempting. But forgiving handling won't do me any good if the tire is rock hard after a day's use.

Mainly 5-15minute stints with 30-60 minute breaks per day. And as many days as I can get throguhout the season, usually 6-10.

How much use can I expect to get from a set?

I don't have any personal experience with each of these tyres, so I won't offer an opinion. Something that would probably help other people, though, is details about what kind of car you're going to use them on. Obviously make/model but other things like modifications, driving style etc.

How heavy is the car you plan to drive?

it's a Mazda 323GTR, about 1100kg, AWD with LSD center and rear. Mostly tight slow tracks, but some higher speed. Running around 250whp in the real world.

Quote from atledreier :

it's a Mazda 323GTR, about 1100kg, AWD with LSD center and rear. Mostly tight slow tracks, but some higher speed. Running around 250whp in the real world.

A friend has one of those, such a beautiful car to drive He was driving on Yokohama's during the last track day and he didn't complain about them, but he never had R888's on that car

Just got a great deal on the r888, so I just couldn't say no.

Going to track 27th, and weather permitting I'll give an impression on semi-slick versus road tyre performance then.

Quote from atledreier :

I'll give an impression on semi-slick versus road tyre performance then.

huh...
don't bother, the difference is already well known

Not to me!

Ok, I'll keep my experiences away from this forum, for your benefit.
I'll be datalogging as well, so both g-forces and laptimes can be compared, as well as any changes in choice of lines.

i would say go for yokas i have always run on them and find them to be exelent

Quote from atledreier :

Going to track 27th, and weather permitting I'll give an impression on semi-slick versus road tyre performance then.

Have fun, don't brake anything

aren't semislicks clearly better than roadtyres?

Yes, I'd think they would be better. I was more curious about characteristics on the limit and over. How much more grip, and how they let go and regain traction.

The R888s are useable as a road tyre (though I wouldn't recommend it). The A048s produce a lot of road noise and wear out much faster than the R888s. In terms of out right grip the A048s are probably better than the R888s and suprisingly good in the wet (haven't driven the R888s in the wet). Overall the harder compound R888s are probably the best tyres for general track use where out right pace isn't important.

well, grippier tyres *do* tend to wear out faster.

you know how it goes, a better tyre lasts less and costs more

Theres not that much difference between, like said the R888's last a little longer but aren't as grippy as AO48's, ive heard the R888's are a little better in the rain too but the A048's are good in the wet also So whatever you chose theres not much difference at all, if your using it for the road aswell id choose the R888's.

They won't see any road use, except maybe the drive to and from the track (25km). I ordered the Toyos, we'll see how it goes.

The A048 to me is a better tire than the r888 or even Potenza RE55s tires.

Dont get me wrong they are all great tires and they all have their own characteristics, from experience the r888 are a soft semi slick tire, ao48 takes slightly a bit more to warm up but lateral grip is phenomenal and better than r888's tires. Re55s tires are an "easy" track tire, my favorite tire of them all. You just need to experiment with all tires to understand what I mean. All 3 tires are great and if this is your first time I would use the cheapest of the 3. Make sure tire psi is 31(hot)

Yeah, I have the Toyo on order and will hopefully get to test them next weekend.