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Author Topic: Using a tube in tubless bias ply motorcycle tires  (Read 405 times)
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Bullfrog
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« on: July 22, 2017, 07:52:06 AM »

Hi all, I just wanted to start a discussion on the rule that requires the use of a tube with bias ply tires. I have been using V rated Pirelli Sport Demon tires on my 1980 Suzuki GS750. The rims are the stock Suzuki mag type tubeless rims found on most Suzuki's of that vintage. My top speed so far is a little over 137 and holds the records in a number of the 750 classic classes. It is always a struggle to get the stiff sidewall V rated Pirelli's to seat properly with a tube. Often the heavy duty Perilli tubes will pop before the tire will seat even using talcum powder and warming the tire. The local Honda dealer that mounts and balances them for me says that a tube shouldn't be used with a tubeless tire and that due to heat buildup the V speed rating would have to drop back to an "H" rating. If this is the case at 137 I am over the 130 speed safety rating. I have also been told that the older 1980 rims were not designed for radial tires so that isn't an option for me. The Pirelli Sport Demon tires have felt very stable at the speeds I have been running and I feel that the stiff sidewalls found on the bias ply tires help with the stability. Can anyone explain why the rule for the requirement of a tube with bias ply tires is needed? A "V" rated tire is good to 149+ MPH. This rating was from the manufacturer WITHOUT a tube. Can this rule be changed? huh     
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wobblywalrus
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« Reply #1 on: July 22, 2017, 01:05:40 PM »

The Straightliners in the UK do a lot of runway racing.  The tire/tube issue would be apparent over there if it is significant.  A query to their technical rules expert can help to answer your question.  They have a website.
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Frank06
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« Reply #2 on: July 23, 2017, 05:06:30 AM »

I think the wording is "tubeless, bias ply type tires may be run with tubes" i.e. it permits the use of tubes, not require it.  I'll investigate some more.

Frank
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Bullfrog
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« Reply #3 on: July 23, 2017, 07:52:08 AM »

"(I think the wording is "tubeless, bias ply type tires may be run with tubes" i.e. it permits the use of tubes, not require it.  I'll investigate some more. Frank)"

Thanks, Frank. I just got a PM from Tim verifying that this is the case. I misinterpreted the wording to mean that you can use tubeless bias ply tires as long as they have a tube. Sorry for any confusion or trouble I may have caused with my wrong interpretation of the rule. I guess I should have asked someone sooner if it didn't sound right. I have been running tubes in my race bikes at Loring for 4 seasons needlessly. Now I have to decide if I will remove all the tubes now or wait till I change out the tires! Thanks for the help, I'll be at the "Harvest Event" in September with the "Snowblower Special" see you all then!
Steve       
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