Tyre Requirements (MC)

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RGV
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Tyre Requirements (MC)

Post by RGV » Wed Jul 30, 2014 12:46 pm

If the MPS 250 record was lifted to 151 MPH next year would the V rated tyre be OK to run for the rest of the event or would the minimum go to ZR?

"Production tires with a speed rating of V, if shaved, can be used up to 200 MPH." Shaved = Worn?

Thanx
Dave

"7.B.8 Tire Requirements:

0 to 50 MPH
Any production tire designed for motorcycle use is permitted.
51 to 130 MPH
Production tire maximum speed rating J=62 MPH, K=68 MPH, L=74 MPH, M=81 MPH, N=87 MPH, P=94 MPH, Q=100 MPH, R=106 MPH, S=112 MPH, T=118 MPH, U=124 MPH, H=130 MPH
131 to 150 MPH
Production tires with a speed rating of V or higher.
151 to 199 MPH
Production tires with a speed rating of ZR or special tires for racing as designated by the manufacturer. Production tires with a speed rating of V, if shaved, can be used up to 200 MPH.
200 MPH+
In excess of 200 MPH special tires for racing as designated by the manufacturer must be used.
265 MPH+
Contestants shall use LSR or other tires as approved by the Motorcycle Technical Committee, Section 9."

Last Minute Racing "its a 2-stroke ya twit - Its supposed to smoke"
DLRA #928
SATA #10

2010 MPS/G 250 118 MPH:)
2011 Washed Out:(
2012 Washed Out:(
2013 MPS/G 250 131 MPH (RECORD):)
2014 MPS/G 250 140 MPH (RECORD):)
2015 MPS/F 250 DNF:(

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RGV
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Re: Tyre Requirements (MC)

Post by RGV » Thu Jul 31, 2014 1:34 pm

"W" rated tyres dont get a mention?

An extract from http://www.bridgestone.co.uk/moto/your- ... d-ratings/

Rating F J L M P R S H V Z W (W)
MPH 50 62 75 81 93 106 112 130 150 150+ 167 167+
KM/H 80 100 120 130 150 170 180 210 240 240+ 270 270+

Thanx Dave

Last Minute Racing "its a 2-stroke ya twit - Its supposed to smoke"
DLRA #928
SATA #10

2010 MPS/G 250 118 MPH:)
2011 Washed Out:(
2012 Washed Out:(
2013 MPS/G 250 131 MPH (RECORD):)
2014 MPS/G 250 140 MPH (RECORD):)
2015 MPS/F 250 DNF:(

rgn

Re: Tyre Requirements (MC)

Post by rgn » Thu Jul 31, 2014 4:38 pm

Dave, my understanding is that (W) rated tyres are by our rules good for up to 265 mph. Generally they are "special tyres for racing". Road race slicks are imo the best option for any LSR bike, unless you are thinking of going over 265. Bill Warners crash has been attributed to tyre failure, and I believe it was a new tyre.

Personally I don't know why anyone would use a treaded tyre, tread grooves are for dispersing water, they serve no other function, and reduce the contact patch of the tyre. Tread mouldings also creates stress points on the tyres (especially if over inflated). Used slicks cost virtually nothing, are shaved (worn-lightened) on the outsides, are virtually new-unworn on the crown, and are well tested for integrity prior to LSR use.

Graham or Ross should be able to answer your question.

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RGV
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Re: Tyre Requirements (MC)

Post by RGV » Fri Aug 01, 2014 1:37 am

My main problem is my bike has an 18 inch rear wheel. Im sure there are tyres out there just need to have a better look.

Dave

Last Minute Racing "its a 2-stroke ya twit - Its supposed to smoke"
DLRA #928
SATA #10

2010 MPS/G 250 118 MPH:)
2011 Washed Out:(
2012 Washed Out:(
2013 MPS/G 250 131 MPH (RECORD):)
2014 MPS/G 250 140 MPH (RECORD):)
2015 MPS/F 250 DNF:(

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ROSS BROWN
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Re: Tyre Requirements (MC)

Post by ROSS BROWN » Fri Aug 01, 2014 9:28 am

RGV wrote:If the MPS 250 record was lifted to 151 MPH next year would the V rated tyre be OK to run for the rest of the event or would the minimum go to ZR?
BASIC ANSWER.. YES.
If this happens , you will have made it to Impound .
Make Graham or myself aware of it as we will want to check the condition of your tires.

Keep the wheels turning..
Ross..
IT IS ALL A RACE AGAINST TIME.
TIME WAITS FOR NO ONE.

HOW FAST CAN YOU GO ?

S/UF 925

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RGV
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Re: Tyre Requirements (MC)

Post by RGV » Fri Aug 01, 2014 11:39 am

OK Thanx Ross.

Dave

Last Minute Racing "its a 2-stroke ya twit - Its supposed to smoke"
DLRA #928
SATA #10

2010 MPS/G 250 118 MPH:)
2011 Washed Out:(
2012 Washed Out:(
2013 MPS/G 250 131 MPH (RECORD):)
2014 MPS/G 250 140 MPH (RECORD):)
2015 MPS/F 250 DNF:(

rgn

Re: Tyre Requirements (MC)

Post by rgn » Fri Aug 01, 2014 12:02 pm

RGV wrote:My main problem is my bike has an 18 inch rear wheel. Im sure there are tyres out there just need to have a better look.Dave
What size are you after (width) Plenty of people still using 18" Avon's on TZ's etc. Have you considered converting to a 17 inch rim? mainly because of massively increased tyre selection you have available to you. Aprilia RS250 rear for instance? the wider the better?

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RGV
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Re: Tyre Requirements (MC)

Post by RGV » Fri Aug 01, 2014 12:23 pm

The Std. size is 140/60 R 18. Im after a 120 - 140. I have a set of Aprilia RS 250 wheels here if I need to go that way. I would like to stick to 18 if I can as I think ill run out of sprockets if I go to 17.

I would have thought that a treaded tyre would give more traction on the salt?

Dave

Last Minute Racing "its a 2-stroke ya twit - Its supposed to smoke"
DLRA #928
SATA #10

2010 MPS/G 250 118 MPH:)
2011 Washed Out:(
2012 Washed Out:(
2013 MPS/G 250 131 MPH (RECORD):)
2014 MPS/G 250 140 MPH (RECORD):)
2015 MPS/F 250 DNF:(

rgn

Re: Tyre Requirements (MC)

Post by rgn » Fri Aug 01, 2014 12:38 pm

RGV wrote:I would have thought that a treaded tyre would give more traction on the salt?
I'm not being a smartass, why? Tread is for dispersing water I have always thought?

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RGV
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Re: Tyre Requirements (MC)

Post by RGV » Fri Aug 01, 2014 2:08 pm

I didnt think ya were being a smart ass, just thought that more sharp edges as in a treaded tyre would give more traction but im open to other ideas. Also decreasing the total contact area might increase the PSI exerted on the salt.
My bike is light and when I go to W speed rated tyres I will be well within the tyre spec. so wont be tearing then to bits. Anyone know weather Brett is running treaded or slick on the rear?

This is the rear tyre ive been using for the last 3 visits to the lake and many runs at Tailem Bend T&T. Still has 50% tread. Tyres tend to last well when you only have 60-70 HP. (depends on what dyno)

Image

Dave

Last Minute Racing "its a 2-stroke ya twit - Its supposed to smoke"
DLRA #928
SATA #10

2010 MPS/G 250 118 MPH:)
2011 Washed Out:(
2012 Washed Out:(
2013 MPS/G 250 131 MPH (RECORD):)
2014 MPS/G 250 140 MPH (RECORD):)
2015 MPS/F 250 DNF:(

rgn

Re: Tyre Requirements (MC)

Post by rgn » Fri Aug 01, 2014 3:35 pm

You know Dave, I wondered about traction as well. When I arrived at the start line of the GPS track for the first time, I was reassured by two 10 inch wide black car tyre marks that went on for about 10 meters. The racing surface in 2013 reminded me of bitumen with a bit of loose stuff on top. The salt, it's hard as hell, as anyone who has tried to knock a tent peg in knows. So there is traction, and there is a bit of slip as a result of the loose stuff.

Next year we will be running nTech slicks at 22-25 psi rear, 31-32 front. I will be monitoring temperatures, after the run. Keeping the tyre in it's temperature range is crucial to traction, the salt tends to be cold, so increasing pressure 1 or 2 psi can put the tyre temp into range for best performance. Soft slicks are prone to cold tearing if the race track temperature is low, so med compounds are probably best. Modern slicks generally are multi compound, with a relatively hardish center compound, so for our purpose this is perfect. Our Pirellis where working like road race tyres, (shedding old rubber for new) but in the direction of rotation, so they were shedding rubber allowing fresh rubber to be in contact with the salt. My starts may have been considered reckless, but spinning the rear offers gyroscopic stability, puts lost heat back into the tyre, as well as shedding the old crust for the new virgin rubber.

Honestly, go for the 17" wheel with the widest rim your sprocket will entertain, (you can buy offset sprockets and upgrade your output shaft bearing) At 160 mph, you are not outside of the scope of readily available sprockets-drive line combinations, or tyres. Tyre contact patch is the thing that drives any vehicle, over inflating reduces this. CD is the other consideration.

Just my two cents.

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gennyshovel
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Re: Tyre Requirements (MC)

Post by gennyshovel » Fri Aug 01, 2014 8:03 pm

I recon installing a mini street sweeper in front of the rear tyre would net bigger gains than a soft compound :shock: , after all,no matter how hard the salt is, there will always be the loose stuff laying on the surface (in a good year, this will reduce, just look at the road to and from the pits on friday)
Methinks treaded tyres might give the salt particles somewhere to hide for a while, while the tyre bites in :?:
RGN,laying rubber at the start , there's a fair chance you would find a canary on your tank,,,,,,,,
Dave, while messing around with midget sidecars, racing on concrete, I had a bit too much traction on the chair wheel while flicking the ass out, I increased the tire pressure, the problem got MUCH worse (rolled the bike when the tyre bit), smaller surface area, same downward force, much more traction, I let the tyre down, & is slipped really well. I dunno how this would relate to the salt though, after all, the 11bhp Mk1 Postie had 7% wheel slip compared to the street.
Tiny
Tiny DLRA# 484
Postiebike Racing , created & funded by TwoBob Engineering

rgn

Re: Tyre Requirements (MC)

Post by rgn » Sun Aug 03, 2014 3:02 pm

gennyshovel wrote:Methinks treaded tyres might give the salt particles somewhere to hide for a while, while the tyre bites in :?:Tiny
I'm doubting that salt is 'displaced' in the same way that water is.
gennyshovel wrote:RGN,laying rubber at the start , there's a fair chance you would find a canary on your tank,,,,,,,,
How unsurprising! Is there anything you don't get a yellow stand down for? How much wheel spin are you allowed at start line or on circuit prior to being stood down?

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RGV
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Re: Tyre Requirements (MC)

Post by RGV » Sun Aug 03, 2014 3:53 pm

rgn wrote: At 160 mph, you are not outside of the scope of readily available sprockets-drive line combinations, or tyres.
At 160 MPH I will be in the realm of custom rear sprockets (38 tooth) and not sure if a 17 tooth front will fit in the available space. If I go to 17 inch rear ill have better choice of tyres but will have to gear up even more.

Primary drive: 2.565 (59/23)
Secondary drive: 3.066 (46/15)
1st gear: 2.454 (27/11)
2nd gear: 1.625 (26/16)
3rd gear: 1.235 (21/17)
4th gear: 1.045 (23/22)
5th gear: 0.916 (22/24)
6th gear: 0.840 (21/25)

My primary and top gear ratios aren't meant for 150 + mph.

Ive only seen slicks used on bitumen or concrete.

Dave

Last Minute Racing "its a 2-stroke ya twit - Its supposed to smoke"
DLRA #928
SATA #10

2010 MPS/G 250 118 MPH:)
2011 Washed Out:(
2012 Washed Out:(
2013 MPS/G 250 131 MPH (RECORD):)
2014 MPS/G 250 140 MPH (RECORD):)
2015 MPS/F 250 DNF:(

rgn

Re: Tyre Requirements (MC)

Post by rgn » Sun Aug 03, 2014 5:46 pm

What is the best rpm-limiter rpm are you doing at wot in top gear? and what is the circumference of the rear tyre? or the radius?

I would certainly be looking to see if you can fit up a 17 tooth front, but looking at the JT catalogue 16 looks like the biggest, if there isn't interference, you will more than likely find a sprocket with the same width and spline off something else, spacing out a few mm, can sometimes make clearance.

Custom rear sprockets are not that hard to source, probably a bit dearer than what you will find on ebay. Chain-gang here in Australia, vortex in the US and others in the UK and elsewhere. google!

Front are cheapest and if you can make the 17 work you will get to use the 39 and 40 rears you probably have in your spares kit. personally i would be using the 17" rear wheel simply because of the increased number of tyre choices you will have, and just sucking up the sprocket costs.

A far a ratings go, Dunlop now have a Y rating on street tyres that takes them to 300 kph.

Click on thumb:
Image

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