After I corded the inside of hand-me-down GForce R1s, I had my car aligned and procured new track tires. My usual favorite, the NT-01, was out of stock across Canada. I was aching to try the Maxxis RC-1 but there are no dealers in my part of the world and importing from the U.S. is too expensive. My local race-oriented tire store was able to express in a set of Toyo RRs at approximately the same cost as NT-01s, so I thought I'd give them a shot. My only reservation is the treadwear rating of 40, so we'll see how they last. Size is 225/45-R15 on 9" 6ULs/

We had an HPDE yesterday in overcast and fairly cool conditions (10-15C), with scattered drizzle. First impressions are favourable - they heat up very quickly (even more quickly than the NT-01 and head-and-shoulders above the R1), showing good stick on the first lap. Turn-in is decent, communication r.e. grip is good and they feel stable under braking and trail-braking. They also sing to you in hard, steady-state corners, which provides another clue about how much you have in reserve. I don't run datalogging equipment, so I can't give you empirical numbers. I can say that I believe I was quicker, was able to corner harder and get on the power earlier (before, I tended to smoke the inside rear when accelerating out of tight corners). How much is due to the tires and how much is due to the new alignment, I can't say for sure. Suffice to say that I was staying ahead of some pretty high-end machinery - Corvettes, a 458 and a brand-new GT3). Overall, I was pleased.

I started out at 30 psi cold and got the following readings from a probe-type pyrometer (all readings in F):
120 115 122----FRONT----117 109 109
(37 psi) (36.5 psi)
117 118 129-----REAR-----124 112 98
(35.5 psi) (35 psi)

I then dropped 3 psi across the board (27 psi cold):
122 113 114----FRONT----107 105 126
(34 psi) (33 psi)
117 120 127-----REAR-----99 105 116
(32.5 psi) (32.3 psi)

Finally, I tried raising pressures 6 psi across the board (33 psi cold):
107 110 109----FRONT----95 89 102
(37.5 psi) (37 psi)
106 111 113-----REAR-----104 91 90
(35 psi) (38 psi)

Our track is fairly short, tight and mostly right-hand turns, so the left-hand tires bear the brunt of the abuse. Readings were done without a cool-down lap (my brakes loved that) and were in the order of LF, RF, RR, LR, outside to inside. Cooler temps and drizzle came during the later sessions, so that probably cooled things down for the later readings. Any input regarding pressures will be greatly appreciated.

 

Yes it looks like the cooler temps/drizzle later in the day skewed your data a bit - you're way under optimal temps across the board so adding pressures to try to get some of the tire to heat up more would be the right approach, which you did later in the day but the effects were masked by the changing weather.

I haven't used RRs, but with an NT01, RC-1 or Hoosier I'd want to be up above 150 F at least. At the last event (hot summer day) we were over 200 F on the hoosiers.

-Ryan

 

I've seen 1.4 to 1.5 gees with 225 RRs on 15x9 6ULs. Great tires.

--Ian

 

Thanks Ryan. I'm thinking of starting out at 35 cold for the next track day and seeing how that work. I can always bleed air to keep them under 40 psi hot and see how the tread temps read.

Yes, they are sticky. What type of life are you seeing? Do they stay sticky until they cord or do they heat cycle out? Thanks Ian.

 

I'm told that they get old and hard before they cord, but mine haven't done so yet. I have 4 track days on them so far (they're a year old, I intended to have more, but the car was broken for six months...), and they're still sticky.

--Ian

 

I am surprised about up-to temp thing. NT-01s are nasty sticky right out of the gate. I can easily put down a lap within 2-3s of a hot lap, not counting the slow pit exit. Never been on hoosiers though, so I don't know how that compares.

good to know though that RRs are like that.

 

Cooler temps across the middle of the tire, is usually an indication of not enough air in the tire. Also, going by your data it looks like you may have too much negative camber in the rear (Read: For optimal tire wear and contact patch). With the way the conditions for the day changed, you may not want to use much of this data. I have also found it really handy to book end your data. Whatever you start with, you finish with to check and make sure the initial data points are true and valid.

 

RA1's like about 40-42 psi hot. Not sure if the RR uses the same compound or not.

 

Thanks all. I have another track day coming up on Tuesday and it's supposed to be warm and sunny (it's an afternoon/evening session, but our hottest temps usually occur around dinnertime). I'll do another set of measurements and try to optimize things.

My alignment specs are based on the recommendations on 949 Racing's page. I couldn't get to 2 degrees negative camber on the front (one side maxed out at 1.5 degrees) and I'm at 1.7 negative on the rear. Toe is zero in front and 1/8" total toe out in the rear. The car does feel more planted, even driving on the street, so I think it was an improvement over my previous alignment (Lanny's specs, more or less, IIRC).

 

You need offset bushings.

RA1s are definitely not the same compound as RRs. RA1s give me 1.1 lateral gees, RRs are 30-40% more than that.

--Ian

 

Toe out on the rear is bad. You should have 0 toe or 1/16 toe in on the rear.

 

As long as you have any senses left and can read a laptimer there is noting wrong with a little toe-out, if it help to reach your goals. Equal compliant rear bushings get rid of the load-added toe out as well.

After a visit in the barrier know that a degree or so toe-out on LR works wonders for right-turn turn-in (think and you are pointing at the apex), but I lost 2 sec on a one minute course

 

As long as you have any senses left and can read a laptimer there is noting wrong with a little toe-out, if it help to reach your goals. Equal compliant rear bushings get rid of the load-added toe out as well.

After a visit in the barrier know that a degree or so toe-out on LR works wonders for right-turn turn-in (think and you're pointing at the apex), but I lost 2 sec on a one minute course

 

My RR's were sticky all the way down to the cords. I had a FTD at an autocross when they were starting to cord.

Don't overlook that they are directional. Toyo has a PDF about how to mount and rotate them for fwd / awd / rwd cases.

You *really* need more front camber. Offset bushings or V8R LCA's in the front. So much more grip at -3 than at -1.5.

 

Here is the rear toe note on the 949 page:
I may have misread it, noting "+1/8" total toe at the rear", missing the "in". That being said, maybe my tech got it right. Can any one interpret the toe reading for the rear? Does -1/16" per side mean toe in or out? Note: ignore the before readings, as I had all the long suspension bolts replaced before the car was hooked up to the rack, so everything moved before measuring.

If I'm indeed toe out, but the car feels stable powering out of turns, should I get it realigned for some toe-in anyway? Niklasfalk, are you saying that I'm destined to meet a wall/barrier with my current setup?

Thanks all.

 

No, what I'm trying to say is that you will be able to feel the balance and react accordingly, it will not snap oversteer and kill you.
If you are concerned, set it a tiny amount in (or 2*tiny if a lot of power).

Are flawed setups a way to success? Of course not, but sometimes bad experiences can be a learning exercise making a lot of the guides and templates make sense.
But it helps if you are able to adjust the setup yourself (rear toe is a bitch).

 

Negative toe is in and positive toe is out.(This is wrong, it's actually the opposite).

 

This is confusing me. I've been doing some Googling on the the subject and this seems to be the consensus:
I think I have toe-out set in the rear.

 

Zero front and any toe out would make your car really twitchy. If your alignment guy is any good at all he would have made sure twice you wanted toe out in the rear before setting it that way.

 

http://yospeed.com/wheel-alignment-e...er-caster-toe/

Sorry, I had it backward.

Still, toe out on the rear will cause tire wear and twitchiness.