So, I was under the impression that lower PSI = more contact patch = more heat = potential hot tear and more PSI = less contact patch = less evenly distributed heat in the carcass but more stress on the surface of the tire and so = potential cold tear However, on a cold track day at Shenandoah Summit Point (a really slow track if unfamiliar) my tire was wearing into rubber dust, as if someone took sand paper to it. It felt cold, looked cold, so my idea was to reduce PSI and get more heat. Yet, the Pirelli tire guy (I was running Supercorsa Greens btw) and the coaches were telling me to increase PSI. What gives? Now, I'm thinking that I should have just been running street tires for this particular ambient temp/track, but I'd like to know why the Pirelli Tire guy was telling me to increase PSI if my tire was already cold. Perhaps the increased contact patch with lower PSI was just transferring too much heat to the cold asphalt?
There are a lot of variables involved in answering your question. What bike? What were ambient temperatures? What pressures were you running? Were you using warmers? Define "rubber dust". What tire vendor were you dealing with? You can PM me or email me at [email protected] if you'd prefer.
i wanna know what this "rubber dust" tire looks like. got a pic? at a cold/windy trackday, its much more difficult to check tire temp especially if u arent using a probe. u really gotta do it at the hot pit wall after pushing on your in lap. otherwise the tire will lose a lot of surface temp by the time u coast in and put the bike on a stand. one thing ive noticed at cold trackdays is that low pressure can only help so much. once u get really low, the tire doesnt make it up to an acceptable hot pressure and feels squishy out on track. this makes u go slower, which puts less heat into the tire, so u probably still tear it. i also think that having a more flexible tire due to low pressure can cause more tearing when the rubber is under-heated.
all the wheels i have seen in the MGP paddock had TPS on them. anyone knows the brand? or a hint for a set that is light? thanks,
2D makes the Moto2 TPS. prob really expensive. http://2d-datarecording.com/en/produkte/custom-packs-1/moto2-custom-pack/
In my experience, about half the racing paddock is setting their tire pressures with a gauge that has a 10% margin of error in the 20-30 psi range. They don't need a Moto 2 level data acquisition system. They need a good tire gauge.
or a comparison with a calibrated tire gauge so they know the difference and take it into account. if it is consistent,at least.
We offer such a calibrated gauge for racers to check their gauges against on race weekends. The problem is consistency with many gauges. People leave them in the sun, don't vent them or otherwise bash them around in tool boxes. I answer tire pressure questions 100 times a weekend. Then racers set their pressures with a gauge 2 lbs off that's been on warmers gang plugged into 15A outlet with three other sets and then come back and tell me my pressure recommendations are wrong because they're experiencing irregular tire wear.
A gauge is a sensitive tool and treating it as such is a no brainer. It is also a very crucial tool, you could end up destroying your tires,so investing in a good one is also a no brainer, given that you're a regular td rider or racer.
If you don't have regular access to a guy like Mike and his calibration, having two is even better. Then you can compare the two and at least hopefully know when one of them goes off. My two gauges typically read within about 1/2 lb of each other when I check (about once a track day weekend). As a track day rider, that is plenty good enough for me. I get what I feel is excellent life out of my tires.
that's why i went from a $3 autozone, to a $20 cycle gear, to a $85 motion pro... however, being able to see the pressures in an instant / right off track (not after "half a mile" through paddock) would be interesting...
Yes, I ended up buying one of those Intercomp digital ones and it always checked on target. Even comes with a foam case. I checked the kids pressure every time, before he rolled out of the pit. I usually checked it when coming in and if I was really on my game I checked the tire temps with a probe as he came off the track. I've burned my hand multiple times on the front rotors and gradually put in angled stems.
Checking pressures, unlike just about everything else at the race track, is free. I recommend doing it often.
Talk to a knowledgeable trackside vendor. I use the Longacre pyrometers and durometers and an Intercomp pressure gauge.
This is the case my Intercomp tire gauge came in. I also carry a pyrometer and the durometer in the same case. If I were to buy again, I would get the pyrometer that lets you check 3 places on the tire tread and remember the readings for you. It was a pain to try and remember everything before getting the chance to write it down in my notebook when he came off the track. I would try and do it at pit wall before making it back to the pits. Metric, how do you use the durometer, I know you push it into the tire and take a reading? I remember in kart racing, guys would use them to try and hit a certain number when softening their tires, but I never messed with that, since I haven't ever used tire softening stuff.
The durometer, to me, is a very relative tool. I don't use it often. My most reliable instrument of measure are my fast and consistent racers. Some guys take longer to get up and going on race weekends. Fast guys are fast in practice. Before I head into a weekend, I have a forecast of compounds and pressures that will work and I rely on my racers to give me proof of concept.
What organization were you riding with? I've heard some extremely inaccurate information from some coaches that run at the Shenandoah Circuit.
05 cbr600rr, traxxion and ohlins suspension properly setup, 55 degrees ambient temp maybe, overcast so no heat on the track. Started with PSI somewhere around 26-32 (messed around with it later, dropped it all the way down to 20 just to see what would happen. Warmers yes, but I was coming off the track with colder tires than when fresh off warmers. Not sure what better way to define dust. The tire was warm at best off the track, no cold or hot tears, no weird patterns caused by geometry. I'd just wipe my tire off and its almost as if I was wiping off sand, only it was the tire. New tires, not old or stored improperly This has to be an ambient temperature issue plus a mix of the slow speed, as the the next day i was on summit main, hotter day and sunny + faster track, with PSI put back to normal and the tires did what they should with perfect wear. I'm just wondering if street tires would be a better choice on such a slow track mixed with a cool day. My pals on Q3s had no issues and i was losing grip all day.
i see this with newer racers.. don't go wicked fast, and you will come in with a lower psi than you headed out with just off the warmers. Talk to your trackside vendor about what works best, what you are on, or a street/sport tire (MDM if on pirelli) .. I had a guy pitted next to me at Summit point last season on evo michelins, and we simply put him at the 36/25psi on the warmers so he came in at 35/24psi.. before, he was copying me at 32/21psi .. and was having all kinds of issues.
