I recommend 36 psi front and 34 rear:

My 55's front stock tires and track tires have been wearing slightly more on the inside edge than on the rest of the tire, so I wanted to make sure that the alignment was OK and that I was running the best tire pressure. I had the alignment checked and it was OK at essentially zero degrees. I have previously checked tire temperatures on the track which led me to select pressures of 40 psi front, 36 rear (see the post at http://www.benzworld.org/forums/r171...t-40-rear.html ) But I had not done this for normal freeway driving with the stock wheel/tire setup.

In the past when racing, I have used a contact pyromete, but now I have a handy key-fob-sized Microtemp infrared thermometer made by Atomik R/C Equipment. (These are normally used by radio control airplane enthusiasts to adjust the mixture by reading exhaust port temperatures.) The unit costs about $35 and can be purchased at most hobby shops -- it works great.

So I made some runs on the local Interstate starting with cold tire pressures of 34 psi front and 32 psi rear. After about 6 miles at 75-80 mph, I measured temperatures across the tire treads as follows:

Air Temp 90 deg. F, Sunny, 75mph.

Tire Tread Temps (deg. F)

------LF---34psi-------------RF 34psi
OUT----MID----IN------IN----MID----OUT
131----129---136----134---125----131

------LR---32psi-------------RR 32psi
OUT----MID----IN------IN----MID----OUT
128----131---140----138---128---122

The low temperatures in the center of the front tires are an indication that they need more air. The hot inside edges of the rear tires indicate that with some more air, the load can be shared by the center of the tire more. The outside edges will likely heat up when cornering, so it's OK if they are a bit cooler. So I increased pressures by 2 psi to 36 psi front, 34 psi rear and obtained the following on another 75mph run:

------LF---36psi-----------RF---36psi
OUT----MID----IN-------IN----MID----OUT
139----137---143------142---136---137


------LR---34psi-----------RR----34psi
OUT----MID----IN--------IN----MID----OUT
129----135----135-----136----136----124

This looks pretty good to me -- perhaps even another psi in the front. I have concluded that the front suspension geometry is designed with a lot of negative camber and that the inside edges of the front tires will always run hot. For normal street use, I'll run 36 psi front, 34 psi rear and bump the rear pressure up by 2 psi when carrying any significant load.

I realize that this frontward bias is contrary to the recommendations in the owner's manual, but this should yield better tire wear. However, this will make the car "looser" (increase oversteer), so before you pump up the front tires and go blasting into a freeway on ramp, be sure to check the car's handling first in a safe setting.

If anyone else has similar data or other suggestions, please share your conclusions and recommendations.

 

Great results thanks mate. I do tend to run my tires a little lower on the street. As the streets are so bad where I live I'm thinking more of comfort than performance. I'd love to see similar results from the Track if your planning to do that would be awesome. I'm running 28 allround on the track and find with the current ES100's I have this gives me nearlly a complete session with good grip and the tyres don't get too greasy.

 

Nice job, slk55er - thanks for that.

 

Hi, Easty. I have posted similar results from a couple of track sessions. That has led me to run with 40 psi front and 36 psi rear, significantly higher that you have used. You can find my post at:

http://www.benzworld.org/forums/r171...t-40-rear.html

If you have a chance to check temperatures, I'd sure be interested. Have you experienced higher wear on the inside edges of the front tires, particularly your track tires?

BTW -- I have purchased Bridgestone RE-01Rs for the track, but have not yet used them. Also, if you can make it to Salt Lake City area at the end of Sept. (23-24) there is a great opportunity to run with LappingDays (http://www.lappingdays.com) at the new Miller Motorsport Park.

 

MMP looks real good - have you run there yet?

 

SLK55er,

Thanks for the informative post. I just bought some Falken Azenis that will come in shortly. I cheated on the rears and ordered 245/40. They have limited sizes and that was as close as I could get. Hopefully there is sufficient room for the tire to travel and there wont be any rubbing. *fingers crossed*

If they work well, it will be a nice fix. I have been trying to locate tires that offer great performance at the track, reasonably priced, yet not all out track tires which would not allow me to drive to the event on the highway.

If they work, I plan to get some tire temps this weekend at Thunderhill.
I'll keep you all posted on my results.

Keep up the good work!

Dan

 

Hi, ClayJ. Yes, I've run both the East and West track, but not in the configuration with both combined and the 3500 ft. front straight. Actually, I've been through the MMP Instructor Certification program and will be there in that capacity.

Turns out that the Sept weekend with Lapping Days is only on Sunday the 24th on the East Track, I believe. Saturday is a track day for Porsche owners who have bought a Porsche from the Salt Lake City dealer. But Sunday is open to all -- see the Lapping Days site at http://www.lappingdays.com

 

I've watched that track being developed since Day One. Looks like a great track -

But yeah, getting to use the whole track seems tougher and tougher with what seems like many of the new tracks going with the 'multiple configurations' theme -- in actuality translating into, "you only get to use part of the track, which part do you want?"....

I have a residence located not too far from MMP...definately want to check it out someday and consider using it as one of my 'local' tracks.... I would most likely be renting the track for use on my schedule - and not using it in attendance with a club, etc.

Do you know what their private garage situation is like?

And of course, I still dream of buying and converting an old airfield, or of building my own track from scratch...one of these days.... And of buying Paul Ricard from Ecclestone when he is finally ready to let it go(!) LOL

Anyways - glad to hear that you like it. I'll see you there someday....

 

The paddock area of MMP is 27 acres! It has several hundred garages for both day use and long-term rental. There are a bunch of car-related businesses that have already moved in.

The garages along pit lane have garage doors on both front and back and are fully equipped with flat panel displays, air, etc.

The clubhouse is a $5 Million building and rumor has it that the whole place cost Larry Miller $60-90 Million.

 

Thanks.

I still haven't heard anything bad, or undesirable, about MMP....

I will be scoping the situation out there....

 

This post provides more viable, factual information in a 3 minute read than most crap that can be found in owners manuals or other data printed by so called experts written over the last fifty years !!!!! I bow to you sir...great job.

 

Thanks mate for the feedback. I'll see what I can do for the Temps on the next track weekend. It's a bit of a holiday for track events here at the moment due to the heat. I'd love to come up there. Not sure about Sept. As I'm in Australia until 27th and It going to take a little planning to drive up as it's like 1300miles.. I hate america.. So many great people and cool things but it's too bloody big. Haha.

My tyres certainly do overheat very quickly. My last track event the ground was a little damp so I left the Tyres with about 36 all round and even then after 2-3 laps they change dramatically. I found having the as low as 28 I think I even dropped them a little lower. I drive the long way round on the warm up lap and there great for the first hot session. Hopefully soon I'll be living in seattle and I'll be able to get down there and join you a little easier. Thanks again for the great info.

 

easty,

So you will be out of the Oven and into the Frezer

That will be a big change, hope you have the AirScarf

And as you can see I do spend time other than slkworld, mostly here and in the W203 section, Alot of drag racers in that section. I kind of miss my C55