Nitto NT01 tyres hot tyre pressures

[bm49]

I have been using semi-slick tyres for 20 years and am familiar with the process of adjusting pressures at the track to achieve an optimum hot pressure. After buying a new set of Nitto NT01's for my 2008 135i I am frustrated that the manufacturer does not appear to have released any such advice. Unfortunately this tyre is not sold in Australia through motorsport tyre specialists as is the case for most other brands. Has anyone come across any suggestions from Nitto tyre technicians?

[martymil]

aim for 34 hot, I found that it worked nicely on my 1m

But it has to do a lot with suspension setup too

Its really up to the individual to test what works best on their car

[Norm1M]

I'm running between 34 to 36 psi hot depending of the track.
I'm using a stock suspension setup and running Nitto NT01 275/35R18 square setup.

[bm49]

Thanks for the responses guys. I recently tried my new NT01's at a club track day held at the Sydney Motorsport Park Gardner Circuit. Using 32 psi hot they felt reasonable but the wear patterns, particularly on the most heavily loaded tyre (front right), look like the pressure was a bit low.
My car is a fully log-booked 2008 135i coupe with a National spec roll cage, KW Clubsport coilovers and 245/40x18 tyres on style 261 8.5" rims in a square setup. As it is also a full road car apart from the cage, bigger brakes, competition oil coolers, race radiator and race seat etc, I suspected it would be bit heavy but was shocked to check it on the track scrutineering scales and the reading was 1611kg with a half tank of fuel and no driver. A friend also checked his similar 2008 car on the same scales. His car was fitted with the Nitto tyres but is in a full road spec and came in at 1515 kg also with half a tank of fuel.
I guess all the gear adds up when you do not strip the car but the additional safety is nice and I can now run the car flat out in long sprint races without experiencing the dreaded limp mode associated with excessive oil and water temps.

[ayao]

Curious to know more about your cooling setup.

Do you think the oil coolers vs upgraded radiator contributed more substantively to keeping the car from limp mode?

[bm49]

I fitted the ER dual oil cooler kit at the end of the last Australian summer and the larger (CSF) radiator about one month ago so it was not an ideal situation to judge the contribution of each change. I run the car mainly in races (not time-trial based track days) all year in day temperatures that range between 10-40 degrees celcius and I think the oil coolers have the greatest contribution to eliminating the dreaded limp mode. There is a story on the ER web site (http://www.evolutionracewerks.com/node/133) outlining their development of the dual kit on their time attack 135i. They claim that the total core surface area of their cooler is 288c.i. vs 41 c.i. for the stock BMW unit. The arrangement of running the oil from engine- cooler1-cooler2-engine seems like a good idea. While I had no problems running the car flatout in races up to 15 (x 2.2km) laps in winter, the addition of a larger radiator was simply to give me an additional safety measure for when I tackle mid-summer races at 40 degrees c. It is nice not to have to worry about that problem any more.
I also solved the brake piston failure and dustboot melting problem when used with competition pads at low cost by fitting 335i front brakes (sliding calipers together with larger diameter and thicker rotors) and installing RaceBrakes stainless steel pistons and silicone seal/boots at the rear. While not a technically advanced setup it works well and replacement rotors pads are much cheaper and readily available compared to the various "big brake" kits. It also does not look very sexy in the eyes of those for whom bling is the only thing!

[ayao]

This is great feedback. I wonder how the ER oil cooler setup would integrate with the 1M front fascia since there's an aux radiator on the left and an aux oil cooler on the right.

Back to your prior question re: NT01 pressures, I typically run 36-37 psi hot. Recently the resident track tire guru (who's forgotten more about tires and track setup than I've ever learned) encouraged me to try 29 psi on my 275/35/18 square setup. Yes, you read that right. 29. He felt that the weight of the 1M and sidewall load rating was plenty ... it was gibberish to me but I trust him implicitly. However, it was the last session of the day so I didn't have the chance to give it a try.

[bm49]

Thanks for the tyre pressure advice ayao. By the look at the wear patterns, 32 psi hot was too low and next outing I will try your higher pressures and try to remember to take my laser pyrometer to check temperature distribution across the tread.
You are right about the conflict with the LH side radiator. The 1M setup seems to incorporate the optional BMW Performance kit(can't remember the correct package name) that is available for all non-M models. To cope with the small power increase that came from the Tune component of the package it included a bigger cooling fan and the supplementary radiator that slots in on the usually empty LHS front.
If doing regular or serious track work you would need to get the ER dual oil cooler kit and fit a larger main radiator. I dare say ER have probably done some conversions on 1M's already. Replacement of the hose setup that diverts coolant to the supplementary radiator on the 1M should be pretty easy by using standard 135i parts. Since fitting the larger radiator my regular oil temperature for road use has dropped from 110C to just over 100C.