Scrubbing in Tyres on a Track

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?

Cheers in advance as always.

 

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.

 

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.


--
Krusty.

http://www.muddystuff.co.uk
http://www.muddystuff.us
Off-road classifieds

'02 MV Senna '03 Tiger (FOYRNB) '96 Tiger '79 Fantic 250

 

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.

 

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
beforehand, that should be enough, as long as they get reasonably hot?

 

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?

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.

 

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.

Yep, but not /too/ hard.

--
Krusty.

http://www.muddystuff.co.uk
http://www.muddystuff.us
Off-road classifieds

'02 MV Senna '03 Tiger (FOYRNB) '96 Tiger '79 Fantic 250

 

We have.

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.

It's not something I'd worry about either though as all that might
happen is the wheel goes out of balance.

--
Krusty.

http://www.muddystuff.co.uk
http://www.muddystuff.us
Off-road classifieds

'02 MV Senna '03 Tiger (FOYRNB) '96 Tiger '79 Fantic 250

 

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.

 

Not totally bollocks; it depends on the type of riding. You find it
takes 5 or 10 miles of lesser hooning, while yer average pootle-to-work
rider would be advised to run the tyre in for say, 30 miles or so to
accomplish the same end.

Whatever, it's horses for courses and I've always let new tyres settle
in for at least 30 miles before treating them great gobbing fistfuls of
raw power from the mighty ShiteOldEngine. I haven't high-sided on a new
tyre yet.

 

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.

 

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.

--
Krusty.

http://www.muddystuff.co.uk
http://www.muddystuff.us
Off-road classifieds

'02 MV Senna '03 Tiger (FOYRNB) '96 Tiger '79 Fantic 250

 

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?

Thanks.

 

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...

 

There should be a thread somewhere from a year or two ago. Basically I
emailed several tyre manufacturers asking why tyres need to be
'scrubbed in' & what it actually does. A couple replied (Bridgestone &
Dunlop iirc). The reasons given were:

1. To make the tyres components/layers fully bond (curing).

2. To fully seat/seal the tyre bead into the rim.

3. To scuff any shininess/crap off the surface.

Reasons 1 & 2 basically just need heat, hence can be achieved with tyre
warmers. Reason 3 needs a bit of riding, but as little as a few hundred
yards would do it. The manufacturers don't use release agents apart
from on a few compounds of race tyre. Any shininess is just because the
moulds are very smooth.

The curing process is the bit that takes the time, & is the reason why
100 miles "scrubbing in" is generally recommended. The actual distance
covered is irrelevant; it's the amount of time that the tyre's heated
for that counts.


--
Krusty.

http://www.muddystuff.co.uk
http://www.muddystuff.us
Off-road classifieds

'02 MV Senna '03 Tiger (FOYRNB) '96 Tiger '79 Fantic 250

 

That's a fucking big bolt. I'm surprised you didn't see it and ride
round it.
--
| ___ Salad Dodger
|/ \
_/_____\_ GL1500SEV/CBR1100XXX/CBX1000Z
|_\_____/_| ..80264../..21661.../..31308.
(>|_|_|<) TPPFATUICG#7 DIAABTCOD#9 WG*
|__|_|__| BOTAFOT #70 BOTAFOF #09 PM#5
\ |^| / IbW#0 & KotIbW# BotTOS#6 GP#4
\|^|/ ANORAK#17 IbB#4 YTC#4 two#11
'^' RBR'06 Points: 75 Miles: 317

 

50mm long, M6 bolt, that is.

I parked the bike on the paddock stand when I came in from
the first session and span the tyre round, just to check it
over. I saw a shiny bit and knew it was pretty much fucked.

I got the screwdriver out and prised the head out, about half
of which had been chamfered off, and then started pulling
with the pliers ... and pulled ... and pulled ... and this bolt
kept on coming.

Wasn't one of mine, so fucknose where it came from.

 

<waves down at the world from snow-capped Quota>

 

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.

Cheers.

 

I'd think the final heat treatment, if done before fitting, would make
the tyre take an undesireable set, perhaps in dimensions or rolling
characteristics. If it's done on the vehicle it's bound to suit the
application. Otoh, I could be guessing and it's just to save time and
money by the makers.