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Scrubbing in Tyres on a Track
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I bought a new pair of BT014s recently, and for various weather and personal
commitment reasons, they've covered about 2 miles so far (riding round the
block to check I'd got the rear wheel alignment correct). I'm off to a track
evening at Brands this week, and won't get a chance to scrub them in before
then.
I know the general view on scrubbing-in on the road is '100 miles or so',
and that's way over-cautious, but how about on a track? Are we talking a
couple of laps, or do I need to take it easy for a session or two?
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They should be ok for gripiness after a couple of laps, but you run a
higher chance of them delaminating if they haven't been cooked/heat
cycled beforehand. There's also a higher chance of the tyre slipping on
the rim.
I'd recommend you either make time to get them nice & hot before the
trackday, or try to beg/steal/borrow some tyre warmers to give them a
cook. If you can't manage either of those, taking it easy during the
first session would be wise imo.
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Don't take this as gospel, but I like to think I know a little on the
subject.
Firstly, the "100 miles" thing is bollox, imo. The main thing is to
get heat into the tyres. Now, there's a sort of catch 22 in that you
can't heat them without working them, and you can't work them without
using them properly. What I usually [1] do is just moderate
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Yep, I'd go with that. Being smooth and progressive is probably the
best advice, so that you don't push the tyre too hard.
My trick is to wipe them over with brake cleaner first to get anything
off the tyres, such as rim lube [1] or release agent, and then to
go out and take it easy for a couple of laps.
I went to the first race of the season at Cadwell on new tyres that
had only touched the road in the distance between backing out of
the garage and being loaded onto the trailer. I did six laps of Cadwell
as a combined qualifying and practice and the tyres came back to
within 3mm of the edge. Admittedly the Ducati isn't putting any
kind of massive power through the wheel, but I certainly wasn't
pootling!
Unfortunately that tyre lasted for 6 practice laps, two races of
6 laps and then got a 50mm bolt through it first time out at Assen.
[1] Steady...
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everything a bit for about 5~10 miles. I still accelerate hard when
upright, and also brake quite hard when upright too, but on turning in
and accelerating out I do things a little slower. You can lean the
bike over a long way, but do it smoothly, and with no other forces
(braking or accelrating).
I reckon one session will probably be more than enough - probably 10
mins will do it. Just feel for the feedback your getting from the
tyres
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Cheers - as mentioned to Krusty, I hadn't been aware of the heat-cycle
thing. Presumably some chemical reactiony thingy that needs to take place
some time after the initial maunfacturing then? And I'm guessing that
allowing them time to cool between heat cycles is more important than the
actual time they spend at temperature?
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No, not really. In fact, keeping them hot minimise the number of heat
cycles the tyres go through, which is why race bikes *always* sit with
their tyre warmers on. This isn't such an issue with road tyres,
which contain additional stuff to maintain the compounds chemistry
across multiple heat cycles (for obvious reasons). But, you really
don't need to worry about letting them cool down.
I think Krusty and I have argued about this before, but I don't think
I've ever heard of a road tyre spinning on the rim. Not saying it
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Oh right - I thought the scrubbing-in was just to get rid of the release
compounds from the mould. So if I can just go for a hard half-hour blat
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There's no such thing - at least not on road tyres. The main reasons
for "Scrubbing-in" are to finish the curing process that's started at
the factory by heat-cycling, & to seat/glue the bead on the rim. It
will also clean off any muck they may have picked up between factory &
wheel.
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beforehand, that should be enough, as long as they get reasonably hot?
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can't happen, but it's not something I'd worry about.
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I've not heard of it happening to a road tyre either, but it's
definitely happened on race bikes, & was one of the three reasons for
"scrubbing-in" given to me by the tyre manufacturers when I was on my
'find out the truth about tyres' mission.
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Hi and PMFBI.
This aforementioned 'mission'. Is there something published about it?
I'm always interested in anything that'll help me know more about my
bike. Any threads on here I missed sometime back maybe?
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Thanks for that. I do wonder about that though. If a tyre needs a
final heat treatment to make it safe, why do WE do it, not have it
done as a part of the manufacturing process?
Not a question aimed at you, BTW. :)
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It's not something I'd worry about either though as all that might
happen is the wheel goes out of balance.
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I've seen it happen on a bike with tubed tyres. The guy braked hard
and ripped the valve out of his inner tube. I don't know whether it
was a recommended fitment.
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Tyres designed for use with tubes have a different bead design which
doesn't stick to the rim. They're generally only fitted to proper
off-road bikes & held in place with rim-locks. Even then they can still
creep as the tyre pressures will typically be 10-15 psi for
trail/enduro & even less for trials.
Some big trailies also use tubes[1], but in a tubeless tyre with
tubeless rims. These don't have rim-locks, even though they're much
heavier & more powerful, as tubeless tyres are designed to stick to the
rim.
[1]The ones with standard spoked wheels as opposed to the BMW/Aprilia
type of spoked wheel.
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Tubed tyres are a completely different kettle of fish, because the
bead doesn't seal against the rim. In fact, that's why, on larger
bikes, they used to fit so called "security bolts" to clamp the tyre
to the rim. Used to make fitting the tube even harder than normal.
My z650 had them.
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Still standard on off road bikes. Not because they are very
powerful but because tyre pressures below 15 psi are used.
The low pressure makes the tyre sit loosely on the rim.
I only fitted one once and it was a bit "interesting", one more
chance to pinch my lily white office fingers.
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I should be taking it fairly easy on the first session anyway, as this is my
first track session of the year - although I may be a bit screwed if the
current 'orrible weather continues.
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Alternatively, borrow some tyre warmers and cook them for 45 mins
beforehand :-)
[1] yes, yes, usually, but not always, ha ha ha
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I've got a similar situation. Brand new 014s, off to Portugal Weds
morning and Cadwell Park a week after I get back. I'll be interested to
hear how you get on.
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Cheers in advance as always.
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I had brand new super corsas on my ZXR750 when I did Cadwell Park track
day[1] I asked Champ and got the answer 3 laps. Must admit that worked a
treat. Most tracks are quite grippy compared to the road.
[1] Tyres to wheels and put the bike on the trailer.
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