Si
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| posted on 5/9/08 at 12:01 PM |
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BEC Tyre presures
Just read the thread on tyres and wondered what everyone had decided was their ideal tyre pressure.
I'm using Toyo T1-R 205/50/15's.
Have you noticed the need to increase presures when travelling two up for instance.
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BenB
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| posted on 5/9/08 at 12:05 PM |
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18PSI all round does the job for me.
I might change them when my tracking is sorted out but for the moment any over/under-steering is solely the tracking being decididly random....
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DRC INDY 7
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| posted on 5/9/08 at 12:10 PM |
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Im running 20 psi all round at the mo but then i hace cec
https://www.facebook.com/groups/462610273778799/
Puddle Dodgers Club
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Johneturbo
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| posted on 5/9/08 at 12:47 PM |
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i'm on 15psi
might try 17 then 20 to compare them........when it stops bloody raining
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Rob Bartley
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| posted on 5/9/08 at 01:12 PM |
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A mate found this thread on a VX220 forum. It is biased towards the little plassy cars but is interesting all the same. Sorry it's a bit long,
i have just copied it in!
"My name is Alan Meaker, I am the Motorsport Manager for Toyo Tyres (UK) Ltd.
I was at Rockingham on the Saturday 1ST March at the LOT trackday and worked with a couple of cars using our R888 tyre regarding pressures and tread
temperatures.
What I would like to do is to offer some advice on tyre temperatures and pressures and how to achieve the best from our tyres when taking part in
either trackdays or racing.
The R888 has a semi race construction (very stiff) and a race tread compound. The optimum tread temperature range is between 85C and 95C measured
using a probe type pyrometer, and ideally a maximum difference across the tread of 9C. The maximum hot pressure we recommend is 40psi. Camber angles
up to 5 degrees are permissible but the final setting will depend on tread temperatures. It is advisable to have as much positive castor as practical
as castor induces a beneficial camber change during cornering. I recommend that the tyres be put through 2 heat cycles before hard use.
The pressures you use will initially depend on the weight of the car, too little pressure on a heavy car can lead to over deflection of the tyre and
subsequent failure.
Below are some basic settings:
VEHICLE WEIGHT COLD PRESSURE HOT PRESSURE
Very Light < 800kg 17 - 22 psi 22 - 29 psi
Light 800kg - 1000kg 20 - 26 psi 24 - 32 psi
Heavy 1000kg - 1400kg 23 - 27 psi 28 - 40 psi
Very Heavy > 1400kg 27 - 35 psi 37 - 40 psi
As a tyre gets hotter the pressure increases, this is due to the moisture in the air. The cold pressure you set to achieve a desired hot pressure will
depend on the conditions on the day i.e. ambient and track temperature, wet or dry. If the day/track is cold you will need to start with a higher cold
pressure as the tyre will not get as hot therefore the pressure increase will not be so great.
Hot pressures must be balanced side to side. Once the tyres have cooled you will find that you will have a difference in pressure side to side, if you
have been racing on a right hand track you will find the offside pressures will usually be higher than the nearside.
Changing hot inflation pressures by small amounts can be used to fine tune handling.
Reduce Oversteer Reduce rear pressures or increase front pressures
Increase Oversteer Increase rear pressures or reduce front pressures
Reduce Understeer Reduce front pressures or increase rear pressures
Increase Understeer Increase front pressures or reduce rear pressures
Achieving the required tread temperatures will depend again on the conditions on the day i.e. ambient and track temperature, wet or dry.
You often here competitors saying “My tyres started to go of towards the end of the race”, this is usually due to the tread getting to hot.
The tread temperatures are constantly changing through out a race, hotter when cornering and cooler when on the straights and cooling even more when
you are slowing to come into the pits. Therefore the temps you record in the pits will be lower than those during the race. So if you record
temperatures within the range given above the probability is the temps will be too high during the race.
Increasing your tyre pressures will cause your tread temperatures to increase, more pressure stiffens the tyre’s casing which results in the tread
having to do more work resulting in the tread getting hotter. Lowering your pressures will cause them to decrease.
Inevitably changing one thing will affect other things, the whole set up of your car is a compromise between anything that is adjustable.
Some of you are also asking about different compounds. Originally we only had one compound ‘GG’ (medium hard), but we have now introduced some sizes
in a ‘SG’ (soft/wet) compound. This was done primarily for sprint/hillclimb (around 60 second runs) where the distances covered are relatively short
and you need the tyres to work/heat up very quickly. This is not a compound I would recommend for race/trackday dry use as the tyres will go off very
quickly.
The sizes that will be available are:
185/60R13, 205/60R13, 195/50R15, 205/50R15, 225/45R16, 225/45R17.
Another subject is the introduction of our Proxes R1R. This tyre was due to be launched at the beginning of 2008, unfortunately this has been delayed
to at least mid 2008 but there is a good chance it will be latter than this. Regarding sizes, initially we will have a rear fit (225/45ZR17) but not
the front (195/50R16)."
Any use to anyone?
Rob
I WILL get out again!!
I have a little bit......need more......
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stuart_g
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| posted on 5/9/08 at 01:17 PM |
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I'm on 20 might try 18 to see what the difference is. I doubt I'll be able to feel a real difference though.
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procomp
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| posted on 5/9/08 at 01:52 PM |
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Hi the Above posting by Rob Bartley is quite interesting.
What it confirms is the testing that Alan Meaker has done with the Toyo's is confirmed by those that have done some meaningful testing with the
tyres also.
IE most if not all people are running them WAY TO LOW on pressure. it's no use tacking the pressures when cold. You need to be checking your
pressures when they are up to temperature.
So if using them on a trackday you can expect them to go up 3-4 PSI from cold to there working pressure. Where if only pottering around on the road.
They may only go up 1-2 PSI. But what is confirmed is that they are better working around the 25-30 PSI range. Far too many people using soft tyre
pressures to try and iron out poor handling problems on cars.
Cheers Matt
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smart51
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| posted on 5/9/08 at 03:34 PM |
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I tried 16 PSI on the track at Mallory Park and found the car quite sloshy round the long corner. 80 was about all it would do. I found that every
1/4 PSI would give me 2 more MPH in the corner.
I set up my car's balance on a 30m diameter circle. More pressure at the rear gave more rear grip. More at the front gave more front grip. I
now run 20 PSI all round because I got bored and never went any higher. Each PSI made a noticeable difference. Incidentally, 33 MPH on a 30m
diameter = 1g cornering force. The car corners nicely at a steady state at that speed. any more power an the back end slip angle increases, any more
steering doesn't much change the direction on the car. Seems fairly neutral to me.
[Edited on 5-9-2008 by smart51]
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Jubal
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| posted on 5/9/08 at 05:18 PM |
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quote:
IE most if not all people are running them WAY TO LOW on pressure. it's no use tacking the pressures when cold. You need to be checking
your pressures when they are up to temperature...Far too many people using soft tyre pressures to try and iron out poor handling problems on
cars.
Interesting. I think it's more to do with everyone relying upon what's gone before as the baseline. I now run 18 all round cold on R888
and the car's pretty neutral on track, a touch understeery but messing with pressures hasn't changed that much (it's either the car
or the poor way I drive). ICBA changing pressures for a run out on a weekend so they stay that way on the road.
The Toyo comments above also lump all sub 800kg cars together. Not good. There's a big % difference between 500kg and 750kg. I'd be even
more interested in results that had more relevance to the weight of the cars in question.
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hobbsy
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| posted on 5/9/08 at 08:46 PM |
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smart51 - I assume thats 20psi cold you're running?
I've seen other posts where a lot of people recommend quite low pressures for BEC's due to the low weight (as low as 15psi) but people
who've actually played with pressures then timed laps have found adding a good 5psi or so makes them faster...
I was running about 18psi cold but going to try more like 20psi cold next time out.
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Si
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| posted on 6/9/08 at 04:53 PM |
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Thanks for your thought's, I've been using 18psi cold and was trying 20psi but on the road there is little difference. I guess you can
notice the difference on the track where you are near the limit of adhesion far more often than you can on public roads.
I did get the feeling that it was a little soft when two up though when using 18psi
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adithorp
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| posted on 6/9/08 at 05:24 PM |
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I'm running at 18psi but havan't tried experimenting.
I'm not sure this is correct though...
"As a tyre gets hotter the pressure increases, this is due to the moisture in the air."
Pretty sure it to do with Boyles law.
http://en.wikipedia.org/wiki/Boyle%27s_law
adrian
"A witty saying proves nothing" Voltaire
http://jpsc.org.uk/forum/
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dhutch
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| posted on 4/11/08 at 09:13 PM |
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Hope no one minds me reusing this thread.
- But with regaurd to tyre pressure and the current weather (ie its trying to be winter already) do you or can you run lower tyre presures?
The logic being that within a margin softer tyres may have more grip, and will also maintain a warmer temperature.
Although of cause in the cold, the recorded presure will be lower naterally, because its colder and there air filled.
Wouldnt be a problem on a track half the same, but im on A032's on the road, and there just no grip because there stone cold all the time!!
Daniel
[Edited on 17/11/08 by dhutch]
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:{THC}:YosamiteSam
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| posted on 17/11/08 at 10:50 AM |
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iv been running the megabusa at 15psi with no probs - that article is as said not for everyone so there will be some who wont agree - after a really
long and hard run yesterday over the pennines on a cold day running a 495kg car + two people (+150kg?) i found the car very very grippy indeed - the
roads were a bit greasy tho in places so i was a bit careful - but running 888's i found them great! never once thought - 'oops bit slippy
or boy these are hard' just felt great all day long.. well impressed
it will be different on track tho - they will be worked much much harder - so then only trial and error will suit your style - but setting it up and
learning to drive your car quickly on the road - then tweaking something YOU ALREADY FEEL GOOD WITH will help a lot
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