Custardpants
|
| posted on 17/3/14 at 08:57 PM |
|
|
R888 Medium not getting hot enough
Hi Guys -
Last season I found I could barely get my tyres (R888 medium compound) above 60 degrees C, with most of my trackdays giving me a tyre temp of around
50. (measured with a laser pyrometer when pulling into the pits) The optimum temperature of the R888s is reported to be 65 to 85 degrees C - I noticed
a massive increase in grip when I got the tyres above 60 degrees on the silverstone GP circuit with all its higher speed corners and that was on a
really hot summers day.
What is the most effective solution?
Tyre pressure up? Tyre softener? I accept ultimately the solution is to change to a softer compound. If so, which is recommended? thanks.
|
|
|
|
|
adithorp
|
| posted on 17/3/14 at 09:00 PM |
|
|
Drive faster.
"A witty saying proves nothing" Voltaire
http://jpsc.org.uk/forum/
|
|
|
loggyboy
|
| posted on 17/3/14 at 09:01 PM |
|
|
Tyre pressure change would only work if edges were hotter than the centre or vice versa.
Mistral Motorsport
|
|
|
Custardpants
|
| posted on 17/3/14 at 09:40 PM |
|
|
quote:
Originally posted by adithorp
Drive faster.
Unfortunately I had to slide the car to get the tyres hotter, so driving faster isn't in all cases completely true.
|
|
|
Pat_T
|
| posted on 17/3/14 at 09:49 PM |
|
|
front or rear is the issue? what sizes are you running?
try a change to one size narrower all round.
I can get mine all nice and gooey on track. (185/60/r13 front, 205/60/r13 rear)
www.instagram.com/patroclueus
|
|
|
jeffw
|
| posted on 17/3/14 at 10:19 PM |
|
|
Tyre size, pressures, age of tyres, weight and power of car....all of these are bits of info that would be needed to answer your question.
|
|
|
laptoprob
|
| posted on 18/3/14 at 07:51 AM |
|
|
Interesting point youre making there. I run medium 888's generally most of the year and swap to slicks when i can. Ive just been to Blyton and
ran my slicks for a few hours. The car was all over the place, infact i spun it which is a first for me at Blyton(in the dry), so i swapped back to
the 888's and normal service was resumed. The slicks are only ok on a summers day at Cadwell but they are hard compound so i may have to get
some mediums if poss.
However the 888's have always been a 'comfort blanket' for as they work whatever the temp but am interested to know if they actually
are that much better in the temps you mention.
Reading with a big interest......
http://www.youtube.com/watch?v=ajlF4nWJtGA
|
|
|
Custardpants
|
| posted on 18/3/14 at 11:00 AM |
|
|
I agree with the R888s being a comfort blanket, on all my days I had reasonable grip in a variety of temperatures, and I had plenty of other thoughts
about the handling which distracted me from thinking more about the tyre temps. Grip from cold appeared ok on tracks during the summer, and they only
appeared to really go off in grip on winter trackdays.
The thread below shows comments from Toyo tyres stating the optimum R888 tyre temperature is between 85 degrees and 95 degrees C, even hotter than I
thought, too hot to touch by hand that's for sure. Surely I can't be getting anywhere near this considering I'm not doing a cool
down lap prior to my tyre temperature measurement, and despite the tyres being gooey they weren't too hot to touch.
http://www.pistonheads.com/gassing/topic.asp?f=18&t=784968
Current tyres are 195/50/15. I think with the atb diff is deserves staggered tyre sizes as the fronts don't get as hot, even with brake bias
adjusted to work the front tyres harder. I do have plans to upgrade to 13 inch wheels and 185/60/13,205/60/13 as soon as possible but I want to get
the compound spot on when I do so.
I did a mixture of tracks (Cadwell, Bedford, Donington, Blyton and Silverstone) last year, where I periodically pulled into the pits to have the tread
measured with a pyrometer to check the temperatures of the tyres. After all the sessions the tyres appeared to my untrained eye to be nice and
'gooey' and had no trouble picking up any loose peices of gravel in the pits. But the tyre pyrometer told a different story, the tyres
were only around 50 degrees C on most circuits when pulling into the pits.
A number of times I took a 94kg passenger out (taking the car's race weight up to nearly 700kg) to try to get the tyres hotter, which only made
a difference by around 4 degrees C. The biggest change to the rear temperature was adding the quaife ATB differential, which allowed a lot more power
down, making my average rear tyre temp go up by 8 degrees C.
I managed to get the tyres at silverstone up to a measured 60 degrees C, where I noticed a huge increase in grip - that's what I'm after
every time, it was such a noticeable difference with perceived cornering 'G' vastly improved. I'm wondering if there is even more
grip available if I can get them hotter, at no point did I notice the tyres going off, even when out on track for 30 minutes at a time, pushing the
car pretty hard. I'm beginning to think that tyre compound really is more important than I thought with these lighter cars, and I almost wish I
hadn't bought a pyrometer and gone to silverstone as It's going to be a lot of bother getting it finally right, I was having plenty of fun
already anyway 
Car spec is as follows
Mk Indy R
Power Gen 2 Busa (174hp at the wheels)
Quaife ATB Diff
Weight 610kgs with 80kg driver, full fuel tank, and plumbed in fire extinguisher. (dry weight 505kg)
Tyres R888 medium compound, 195/50/15 front and back. Tyres are now coming up to three years old / approx 9000miles of road use and about ten
trackdays, but at glance do not appear old or past it (hence my thoughts on trying some tyre softener)
Pressures 17 PSI Hot
|
|
|
Davey D
|
| posted on 18/3/14 at 12:16 PM |
|
|
On all of my blyton trackdays i have run medium compound R888 for 1/2 of the day, and cross-ply slicks for the other half. I notice a good bit more
grip ( especially on the front end) with the slicks. With the R888 once warmed up after a good few laps i feel that i can still push them a bit too
hard into a corner, and get some controllable understeer, where as when i push into the same corners harder with the crossply slicks i get no
understeer at all, and just grip
|
|
|
onenastyviper
|
| posted on 18/3/14 at 12:33 PM |
|
|
quote:
Originally posted by jeffw
Tyre size, pressures, age of tyres, weight and power of car....all of these are bits of info that would be needed to answer your question.
+1.
"If I knew what I was doing then it wouldn't be called research would it?...duh!"
|
|
|
gixermark
|
| posted on 20/3/14 at 11:44 AM |
|
|
3 years old and 9k miles !!!! are you sure they are medium ??
what cold pressure are you starting at ? 17 psi hot sounds low
|
|
|
gaz_gaz
|
| posted on 20/3/14 at 12:00 PM |
|
|
I had a similar problem albeit on A048rs in a MNR.
Switched from medium to soft compound and there was a little improvement.
In the end I increased the toe in a little and that seen the biggest improvement but did wear tyres out quicker.
|
|
|
adithorp
|
| posted on 20/3/14 at 05:17 PM |
|
|
9000miles and ten track days? How much wear are they showing?
Sounds like you just aren't working them hard enough. I get 3-5000and 4-5 track days out of a set.
"A witty saying proves nothing" Voltaire
http://jpsc.org.uk/forum/
|
|
|
sam919
|
| posted on 20/3/14 at 09:12 PM |
|
|
Set them all at 18psi, do a few laps and they should all be more than 21 psi if not then some things up, if they are over you have it sussed, set them
all to 21 its handy to have someone waiting in the pits to help you out.
If the car has been corner weighted and set-up assuming around 1-2 deg neg front and shimmed or set from 0.5 to 1.5 neg rear, just a small amount of
toe in, and 15-20mm rake, you should be able to get mediums ( GG aren't they?) Up to temp, or 21psi hot. Another assumption is you cars around
500kg?
The car needs to have approx 14deg slip angle to get the performance ftom the tyres, so there needs to be an element of slip/ slide like you mention
to get the best from the tyres if not you won't get near the operating temps needed for the tyre to perform.
If you have a clear track try braking and accelerating in bursts as this will put good even temp into the tyres, weaving is OK but tends to roll the
tyre and put heat into the edges only.
I would just pushing a little more, get the car moving under you a lot more and you should be able to get the desire temps in to them.
|
|
|
yellowcab
|
| posted on 20/3/14 at 09:35 PM |
|
|
I was running full slicks at the rear at Blyton last Saturday, and my rears were 77deg, fronts were 67deg (185/60/13 A048R's)
|
|
|
hobbsy
|
| posted on 20/3/14 at 10:15 PM |
|
|
I agree with what Adi said, sounds like they are lasting a long time. Also whilst I too have an infra read thermometer for the same purpose they are
not dedicated tyre pyrometers so I wonder if they would read higher as they use a metal probe that you do prod in a bit to the tyre?
|
|
|
jeffw
|
| posted on 20/3/14 at 10:34 PM |
|
|
3 year old tyres will be pretty hard....I think high(ish) pressure and age is the issue here.
|
|
|
