Tyre pressure on tracks?

I let out 6 psi per tyre on the trackday but the tyres are utterly
fucked, properly melted & bobbled to ****.

Is that normal or have i had them too hard or soft?

They are Michelin power tyres.

 

Possibly not, there was a bloke there doing it. If i had time i would
have him give it the once over.

I may well have to have that looked at then.

 

6 psi down sounds OK.

it's a BFO heavy bike, and you're not exactly lightweight.

I'd say "fucked" is what I'd expect the tyres to be after an
enthusiastic day at Cadwell.

 

My rear (tyre) was fucked on the 12R after my trackday. Big heavy
bikes been ridden at speed on the track over several sessions will do
that.

P.

 

What you're trying to do is to run the tyres at the optimum pressure,
as recommended by the tyre manufacturer for that fitting.

When you use the bike (normally) on the road, you have long periods
of not putting any kind of stress on the tyre, so it stays relatively
cool. The air inside the tyre stays at a pretty constant temperature
so it will stay around the same pressure.

When you use the bike on the track, you are putting it under a
lot more stress and load. Some of this energy is absorbed by the
air in your tyres, which makes it hotter. As the heat increases the
air expands, so the pressure increases. This obviously affects the
running pressure of the tyre, so you need to adjust the initial (cold)
pressure accordingly.

Dropping the pressure by <some> is fine, but the best way is to
take a few PSI off the tyre, do a session and then measure the tyre
pressure when you come back in. You then have a much better pressure
reading under those load conditions, because the tyre will still be
"hot".

If you don't know what pressure you have in your tyre before you
start,
it could well be none, so you really should get into the habit of
checking tyre pressures regularly, not just when on trackdays.

The wear marks on your tyres are more to do with your suspension
settings than your tyre pressures. You should have a nice even wear
pattern across the whole of the tyre, without any tears or rippling;
these are signs of your suspension not working correctly.

Tyres also degrade when they go through heat cycles. Putting loads of
heat into them and getting them up to "track" temperature and then
letting them cool reduces the amount of grip in the tyre because it
"cooks" the rubber and makes it slightly less flexible each time. Some
race tyres will only last a few cycles then need to be binned. Road
tyres
can handle a lot more, but they may not be working in their optimum
temperature range while on the track either!

The use of tyre warmers helps to not only get your tyres up to
operating
temperature quicker and thus saves you doing two warm-up laps on a
trackday (big fucking deal!) but more importantly it will reduce the
heat cycling effect because it keeps the tyres warm between track
sessions. Note that there's not much point in using tyre warmers
then sitting in the paddock holding area for 15 minutes as by that
time
your tyres will be cold again. Draw your own conclusions, but anyone
using tyre warmers on road tyres is (a) a cock and/or (b) has more
money than sense.

Spending the £30/£40 on having an expert check and set your suspension
for you on a trackday is possibly the best investment you will ever
make on your bike and it can really transform the feel and handling
you
get from it. Well worth it IMHO.

Note that most of this goes out the window once the trackday finishes
and you ride it on the road again.

;-)

 

Aaaaaarrrrrrggggggghhhhhh!

 

I had my CBR suspension briefly done by Colin from 100% Suspension last
weekend. It now doesn't try to slide coming out of corners hard on the
gas and doesn't pogo so much coming off the brakes. Flicking from left
to right fast doesn't get it doing Zebedee impressions and trying to
tie itself in knots. He recommended I dump the 10W oil up front and fit
15W when I fit the Maxton rear shock, but it's fine with the fucked
standard rear shock that's in there at the moment.

The biggest result is that my rear tyre isn't ripping up any more,
which it was on the previous settings, it now has a nice even grain
across the whole tread with the usual melted bobbly bits right on the
egdes.

--
Lozzo the velologist
Suzuki SV650S K5
Honda CBR600 FW trackbike
Yamaha SR250 Spazz-Trakka
Suzuki GSXR750 L
Suzuki TS50X
Suzuki TS50X

 

Lol, I take it that you disagree with this view?

 

TBF, I don't have a particular view one way or the other and I bow to
your better knowledge.

Really, it was just an attempt at humour in that we'd gone through heat
cycles and how it *improved* new tyres just the other day, and now
you're saying it *degrades* tyres.

I guess a smiley might have helped, but "smileys are for cunts"

 

Heh. I must have missed the whole debate on the other thread.

I've never heard that heat cycles improve new tyres. Once a new
tyre is scrubbed it's ready to go as far as I'm concerned. I've
scrubbed a tyre in two laps (of eight) of qualifying, which seems
to be ideal as you're running on proper fresh rubber and they do
feel much better than a tyre that has done a couple of race
meetings.

Most of this would be unnoticeable on the road anyway because
you're simply not going from one extreme to the other in such
a short space of time. On the road you may accelerate and corner
hard, but you will certainly also spend some time riding normally
both before and after, so it gives the tyre time to both heat up
and cool down much more gradually than coming out of a race and
straight into the pit garage.

Heat cycles is but one of a number of factors that will degrade a
tyre - oil, water, sunlight, cleaning fluid, road salt, etc, etc.

 

[snip explanation of heat cycles in tyres]

I don't suppose you know anything about whether average speed cameras
can catch you if you change lanes, do you?

 

Well, now that you ask...

 

I use warmers on my Rennsports, but I make a point of leaving them on
until the first in the line start to move onto the track, and then I
tag on at the back of the group. There's no sitting around in the
holding area waiting for them to cool down and I get to go fast right
out of the pitlane, which makes a difference to me because I don't want
to waste 2 laps of every session bimbling round warming my tyres when I
can do that in the pit garage - I paid money to ride fast on track, not
bimble round for 3 out of every 15 minutes. Starting at the back of the
group doesn't bother me, because I'm the one with the ready-warmed
tyres and I can make my way up to the front within a lap or two because
of it, which gives me good practice at clean overtakes.

As soon as I get back into the pit garage I put the warmers back on for
5 minutes and then turn them off to let the tyres cool gradually,
because I've been told by the tech men from Bridgestone and Dunlop that
it's quick cooling at ambient temperature that does the damage, if you
cool them slowly in warmers they don't deteriorate as much or as fast.

My Rennsports have lasted for 7 trackdays so far, 2 of those being
double used by me and my mate Ratty instructing in fast group and some
going out to play with Lawesy and others. They've probably got another
trackday left in them at my pace, and then they are going on my SV
until they are bald.

I am certainly not made of money, and I haven't been called a cock yet
for doing this.

--
Lozzo the velologist
Suzuki SV650S K5
Honda CBR600 FW trackbike
Yamaha SR250 Spazz-Trakka
Suzuki GSXR750 L
Suzuki TS50X
Suzuki TS50X

 

That's because you're doing it right, as I explained in my
post. I'm sure that the Rennsports you're using are more of
a trackday tyre than a road tyre anyway, which was also another
point in the above.

Besides, when we line up on the grid for racing our tyres
are nowhere near up to operating temperature, but I still
give it more into the first corner than I would normally
dare on a trackday, instructing or not. And our rules say
we're not allowed to use tyre warmers either.

 

I have the road compound Renns, which was all that I could find at
reasonable cost when I needed some. Sure, they are better than most
road biased tyres, but nowhere near as sticky as Pilot Races or
Supercorsa Pro SC2s[1]

Oh ****, that sounded wrong. I don't instruct, that's Ratty and Danny's
job - I just ride round getting in peoples' way.

[1] What I am thinking of getting next

--
Lozzo the velologist
Suzuki SV650S K5
Honda CBR600 FW trackbike
Yamaha SR250 Spazz-Trakka
Suzuki GSXR750 L
Suzuki TS50X
Suzuki TS50X

 

I normally just drop a couple of pounds each end, but last time,
seeing as the trackday organizers made a big thing of it, I asked the
tyre guy what I needed.. He said "32 front, 30 rear", and explained
that they woul warm to 36-36, which they did. However, even for road
use, 36-36 is the *cold* temperature (and for the R1, 42 is the "lardy
bastard" rear pressure anyway), so I'm not convinced. The bike handled
OK, I suppose, but I've never had problems at higher pressures either.

 

My CBR runs 33F 36R for road, but on track I run them at 31F 29R. I
haven't taken hot pressures because track bears no resemblance to road
use.

--
Lozzo the velologist
Suzuki SV650S K5
Honda CBR600 FW trackbike
Yamaha SR250 Spazz-Trakka
Suzuki GSXR750 L
Suzuki TS50X
Suzuki TS50X

 

Something I remember from years ago is taking the cold and then the hot
temperatures and comparing the two, aiming for a 10% increase.

 

I wouldn't say *no* resemblance. Also, one organizer advised *against*
dropping pressures. There didn't seem to be excessive problems there:
I know I didn't have any difficulty. My feeling is that it probably
makes a difference but only if you're a fast rider and get close to
the ragged edge - I'm not quick enough for it to matter that much.

 

It would depend on the day as well - a cool day and a cold track
will obviously affect the tyres less than a baking hot day when
the track is warm.

Not doing anything with them at all is fair enough, but knowing
what's in them (and thus getting people to check) is a good thing!