Squared off tyre spinning up - SV650.org

ChrisCurvyS · 27-09-12, 01:24 PM

As my daily commute is all motorways and dual carriageways, my rear tyres get squared off pretty quickly.

I've noticed in the current weather that, despite in theory creating a larger contact patch, straight-line grip seems to have really gone downhill as a result, though the tyre is easily still legal and has plenty of life left in it.

The rear keeps spinning up for fun, even from a rolling start (think people thought I was attempting a burnout at the lights last night) and it's really easy to lock it up on the back brake.

Tyre is a previously excellent Metzeler Z6 but I had the same issue with the Continental I had on before it - that even spun at 80ish on the motorway, which seems absurd for a 70bhp bike.

Just wondering if anyone knows why? Guessing the rubber left in the squared-off section is maybe a harder compound than the stuff which has worn away?

Apologies if this has been asked before but I couldn't find anything via the search facility.

27-09-12, 02:05 PM

Just putting this out there for the experts. Could it be that squaring-off may have an effect on suspension geometry? Or rather, you may need to adjust the suspension to account for the behaviour of the tyre?

ChrisCurvyS · 27-09-12, 02:08 PM

That's a possibility. I also wondered whether the flatter profile leads to less water displacement but it doesn't need standing water to do it - just a bit of damp seems to be enough!

Plus I'm 16 stone so it's not like there's not enough weight pressing down...

27-09-12, 02:26 PM

Doesn't squared off = less tread and therefore a slicker tyre?

ChrisCurvyS · 27-09-12, 02:42 PM

Often does but on there's no tread down the centre of the Metzelers anyway, just on the shoulders.

Wondering whether it's worth buying a new rear or holding off until after the winter so it doesn't go to waste pootling about in crap weather....

Mark_h · 27-09-12, 05:19 PM

Can't answer for Chesire but down South we've had a dry spell then a wet spell so roads are slippy as hell. Even my car with absolutely mahooosive expensive tyres is like Bambi on ice at the moment.

Also it's got colder. Cold tyres on a cold road = less grip. Cold rider with cold brain = more ham-fisted throttle.

NTECUK · 27-09-12, 05:38 PM

Point contact curved new hoop cuts through surface contaminate
Squared flat profile less force per Nmm2.

fizzwheel · 27-09-12, 07:46 PM

Quote:

Originally Posted by ChrisCurvyS

Wondering whether it's worth buying a new rear or holding off until after the winter so it doesn't go to waste pootling about in crap weather....

Replace it if it needs replacing. Winters on its way and personally speaking I'd rather have good tyres for the winter season so I have the maximum grip available to me to deal with the poor weather and corresponding road conditions.

ChrisCurvyS · 27-09-12, 08:40 PM

Some really good points there - know cold hands can be very clumsy, particularly when I'm wearing my slippery waterproof over-trousers which means I have to put more weight on the hands and they go a bit numb.

Also wondered weather a more contact patch isn't necessarily a good thing if it means the downforce is less concentrated and yeah it's been particularly bad up here too Mark with leaves, mud etc on the roads.

Might invest in a new rear - seen reasonable ones for 90 squid on M&P.

chris8886 · 27-09-12, 08:50 PM

what pressures are you running?

27-09-12, 01:24 PM	#1
ChrisCurvyS Member Join Date: Dec 2011 Location: Cheshire Posts: 562	Squared off tyre spinning up As my daily commute is all motorways and dual carriageways, my rear tyres get squared off pretty quickly. I've noticed in the current weather that, despite in theory creating a larger contact patch, straight-line grip seems to have really gone downhill as a result, though the tyre is easily still legal and has plenty of life left in it. The rear keeps spinning up for fun, even from a rolling start (think people thought I was attempting a burnout at the lights last night) and it's really easy to lock it up on the back brake. Tyre is a previously excellent Metzeler Z6 but I had the same issue with the Continental I had on before it - that even spun at 80ish on the motorway, which seems absurd for a 70bhp bike. Just wondering if anyone knows why? Guessing the rubber left in the squared-off section is maybe a harder compound than the stuff which has worn away? Apologies if this has been asked before but I couldn't find anything via the search facility.

27-09-12, 02:05 PM	#2
Runako Guest Posts: n/a	Re: Squared off tyre spinning up Just putting this out there for the experts. Could it be that squaring-off may have an effect on suspension geometry? Or rather, you may need to adjust the suspension to account for the behaviour of the tyre?

27-09-12, 02:08 PM	#3
ChrisCurvyS Member Join Date: Dec 2011 Location: Cheshire Posts: 562	Re: Squared off tyre spinning up That's a possibility. I also wondered whether the flatter profile leads to less water displacement but it doesn't need standing water to do it - just a bit of damp seems to be enough! Plus I'm 16 stone so it's not like there's not enough weight pressing down...

27-09-12, 02:26 PM	#4
Brettus Guest Posts: n/a	Re: Squared off tyre spinning up Doesn't squared off = less tread and therefore a slicker tyre?

27-09-12, 02:42 PM	#5
ChrisCurvyS Member Join Date: Dec 2011 Location: Cheshire Posts: 562	Re: Squared off tyre spinning up Often does but on there's no tread down the centre of the Metzelers anyway, just on the shoulders. Wondering whether it's worth buying a new rear or holding off until after the winter so it doesn't go to waste pootling about in crap weather....

27-09-12, 05:19 PM	#6
Mark_h Member Mega Poster Join Date: Aug 2005 Location: Fleet, Hampshire Posts: 2,448	Re: Squared off tyre spinning up Can't answer for Chesire but down South we've had a dry spell then a wet spell so roads are slippy as hell. Even my car with absolutely mahooosive expensive tyres is like Bambi on ice at the moment. Also it's got colder. Cold tyres on a cold road = less grip. Cold rider with cold brain = more ham-fisted throttle. __________________ Don't want to be the quickest; don't want to be the best; just want to be the one having the most fun. XL125Varadero -> Curvy SV650N-Y -> SV1000N-K3 -> Multistrada 1200s Twin-tastic stuff. Minister for Sustainability *Aliquid prudentissimus delectabiles et intelligentes in adamasset lingua.* Last edited by Mark_h; 27-09-12 at 05:23 PM.

27-09-12, 05:38 PM	#7
NTECUK Member Mega Poster Join Date: Apr 2011 Location: essex Posts: 5,314	Re: Squared off tyre spinning up Point contact curved new hoop cuts through surface contaminate Squared flat profile less force per Nmm2. __________________ Raisin cookies that look like chocolate chip cookies are the reason I have trust issues.

27-09-12, 08:40 PM	#9
ChrisCurvyS Member Join Date: Dec 2011 Location: Cheshire Posts: 562	Re: Squared off tyre spinning up Some really good points there - know cold hands can be very clumsy, particularly when I'm wearing my slippery waterproof over-trousers which means I have to put more weight on the hands and they go a bit numb. Also wondered weather a more contact patch isn't necessarily a good thing if it means the downforce is less concentrated and yeah it's been particularly bad up here too Mark with leaves, mud etc on the roads. Might invest in a new rear - seen reasonable ones for 90 squid on M&P.

27-09-12, 08:50 PM	#10
chris8886 Member Mega Poster Join Date: Oct 2006 Location: Hertfordshire Posts: 2,797	Re: Squared off tyre spinning up what pressures are you running? __________________ AR08 to AR13-QUALITY! 650s: '52 curvy in yellow, was my baby cbr600rr: Mivv exhaust and a bagster tank cover. Now gone to a new home. Daytona 675: Arrow can (with a baffle that's gone missing in action....), quickshifter, shorty levers, custom paintjob

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