Wingnut
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| posted on 17/6/10 at 11:26 AM |
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Tyre temperatures - reading and understanding them!
All,
Am considering purchasing a tyre pyrometer to use at track days and sprints to try & get the best out of my tyres.
However I was wondering if anyone had experience and/or successes based on tyre temperature readings ?
Is it as simple as, say, tyre centre too hot = reduce pressure, outer edge too hot = more camber etc etc....?
Any experiences or advice greatly received!
Regards
Julian
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MikeCapon
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| posted on 17/6/10 at 12:14 PM |
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I have used a pyrometer on F1 sidecars. As part of the set up process it is a valuable tool.
You'll need the tyres to have been properly warmed. I'm not sure that a hill climb or sprint would be enough. What you are interested in
is the real temps the tyres are running at over the "lap" and with a very short timescale the tyre will always be getting warmer so you
will read a max value. It can still be useful though, as "back to back" data and to measure the results of any chassis changes.
You'll need someone else to help measure. Alone you'll be too slow getting out of the car etc to get useful data.
Don't go slow on the slow down lap. This will also fuzz the data.
Measure as soon as the car has stopped, always in the same order. For example FL FR RL RR and record the data. The most useful part of tyre temp
reading is the ability to compare with earlier data.
Measure outer, centre and inner temps. On your set up sheet you should also have a record of ambient temp, track temp and humidity.
As you have already pointed out the two key areas that can be "driven" by tyre temps are camber and tyre pressure. The tyre supplier
should be able to give a safe or recommended range for these.
One thing to watch for is a circuit that loads a certain area due to the last corner(s). Comparison between different circuit data and experience
should help you to avoid being misled.
The best tyre temp info is off a good DA system. One of the last race cars I worked on had Magneti Marelli DA with 12 infra red pick ups. When you
read this data you are seeing the real world info. Nice, but costs around 40 Locosts!!
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Wingnut
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| posted on 17/6/10 at 01:33 PM |
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Mike,
Thank you for a detailed and informative post, very interesting reading! I have enclosed a picture of the pyrometer that I intend to use. It's a
long way off the DA system you describe but I think it will serve my purposes. As you can see, it stores the three separate readings for each tyre. I
will have to make a note of the pressures separately.
I was wondering, when you insert the temperature probe into the tyre, how far should you insert it? presumably the reading needs to be taken below the
surface of the tyre, ie in the tyre carcass? 2-3mm??
Your comment on tyre temperatures at hill climbs & sprints raises an interesting query. As you say, the tyres will not reach their optimum
temperature over such a short distance, but presumably the tyre data is just as valid? Surely it's the *difference* in temperature across the
tyre as opposed to the *actual* temperature ?
I'd be really interested in your opinion!
Regards,
Julian
 
Rescued attachment 50690.jpg
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MikeCapon
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| posted on 17/6/10 at 01:54 PM |
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Hi Julian,
Good question that "How far do you insert it?" The pyrometers I've used in the past have all been infra red types with a laser
"pointer". I'd first off ask Longacre because insufficient penetration (oo-er missus) will result in corrupt data as the probe could
be influenced by ambient temp.
Looking at the Longacre spec the pyrometer is supplied with an adjustable probe to control insertion depth which will presumably eliminate the above
problem. I'd want to tak the temperature as close to the surface as possible without getting wobbly numbers. Your 2-3mm is probably about right
IMO. You could easily test this by taking several temps in the same spot to ensure consistent results.
Yes the comparative data is useful on short runs but you'd want to have a good bit of historic data to make sure the numbers and temperature
profiles are reasonably consistent. With a short run any "event" during the run will have a much greater impact on the numbers. Having
never done this on hills or sprints that's about as much as I would feel qualified to say.
Hope that helps.
Cheers,
Mike
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v8kid
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| posted on 17/6/10 at 02:42 PM |
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I stick the probe in all the way on mine as the surface cools down v quickly. good choice of pyro I don't have a recording one and have to use a
voice recorder which is a pita with the background noise. Don't forget to record hot and cold temps after the race so you can set it up close to
optimum next time you are at that track
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Bluemoon
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| posted on 17/6/10 at 04:37 PM |
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Humm I work with IR sensors.. Wonder if I could make a real time system.........
Dan
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Wingnut
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| posted on 25/6/10 at 01:19 PM |
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All,
OK, I had a very interesting track day & enjoyed using the new pyrometer. throughout the day I experimented with varying tyre pressures & here
are some of the results (deg F)
tyre pressure - 33 (hot)
front left front right
outer middle inner inner middle outer
117 138 158 148 140 109
rear left rear right
137 153 157 157 158 138
tyre pressure - 30 (hot)
front left front right
outer middle inner inner middle outer
124 139 154 157 145 117
rear left rear right
152 156 163 161 155 143
tyre pressure - 25 (hot)
front left front right
outer middle inner inner middle outer
129 151 165 152 148 120
rear left rear right
147 167 169 177 166 148
I was wondering if anyone had any thoughts on these temperatures?
I was suprised the outside edge of the tyre always seemed much cooler, especially as I am running only 1 deg of negative camber both front and
rear...???
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v8kid
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| posted on 25/6/10 at 07:29 PM |
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Check the camber again. Are you running crossplies?
You'd be surprised how quickly the sales people at B&Q try and assist you after ignoring you for the past 15 minutes when you try and start a
chainsaw
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Wingnut
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| posted on 25/6/10 at 08:50 PM |
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OK, am running radials. I have very little body roll, even when cornering very hard.
I was wondering if reducing the pressures would allow the tyres to roll over on the rims slightly??
Regards,
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v8kid
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| posted on 26/6/10 at 08:55 AM |
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I think you need to corner a bit faster. The tyres should be too hot to touch after a fast lap. There may be a setup problem with your car that is
preventing you from going faster round corners and the quickest way to find out is to take the car to the limit and see if it oversteers or
understeers.
Otherwise is there a friendly test driver at your local track who could do a few laps and advise?
You'd be surprised how quickly the sales people at B&Q try and assist you after ignoring you for the past 15 minutes when you try and start a
chainsaw
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