motorcycle tyres front & rear

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ChrisACT
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motorcycle tyres front & rear

Post by ChrisACT » Mon Mar 04, 2013 2:10 am

Hi there,

I'm looking at tyre options for me M/F 100cc bike.

My rear rim is a 1.85 x 18 so I wanted to run a 90/90-18 tyre on it. There's not a lot of choice in rear tyres of that size.

I read in some other threads that we're not allowed to run front tyres on the rear. But I can't find anything in the 2013 rule book about that.

I know the tyre has to have a speed rating of at least H for my class. I'll be lucky if I'm putting 30HP through it at anything even remotely close to 100mph.

What's the real rule on this?

Thanks,
Chris

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JonB
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Re: motorcycle tyres front & rear

Post by JonB » Mon Mar 04, 2013 6:52 am

Hi
The rules that your bike will be scrutineered against are in the rule book.
Don't go looking for other "rules" to make your life harder.

Cheers
jon
DLRA#1115
Underhouse Engineering

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ChrisACT
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Re: motorcycle tyres front & rear

Post by ChrisACT » Mon Mar 04, 2013 6:45 pm

JonB wrote:Hi
The rules that your bike will be scrutineered against are in the rule book.
Don't go looking for other "rules" to make your life harder.

Cheers
jon
Fair enough. If it weren't for the fact that the "no front tyres on the rear" thing had been posted by the former chief bike scrutineer only a few months ago, I may not have paid it much attention.
hawkwind wrote:During my tenure there were 2 motorcycle accidents in which the riders where injured and needed hospitalisation . One stemmed from a bad speed wobble and the other from a rubber valve stem breaking away from the rear tyre ... both these incidents were investigated by the race director ,my self and others from our findings several rule changes were made being the mandatory use of metal valve stems , the banning of allowing front tyres to be used as rear tyres and the mandatory use of steering dampeners..
I can see that at the moment, there's no rule to prevent me from doing it. I am interested to hear opinions on whether or not it's a "good idea". If it is likely to be dangerous then I'd love to hear from those who know, why that is so.

Also keep in mind that this is not Ack Attack we're talking about here. My bike will not weigh more than 200kgs wet (including the rider) and will be lucky to have 30HP.

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internetscooter
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Re: motorcycle tyres front & rear

Post by internetscooter » Mon Mar 04, 2013 7:40 pm

Chris - tyres are my main limiting factor so I have done a bit of research. The following is what I have found as a good resource....

http://www.tyresafe.org/images/tyre-saf ... eaflet.pdf
Paul
---
DLRA #647
89.664 mph (aiming for 100mph+)
Vespa Labs [url]http://www.vespalabs.org[/url]

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ChrisACT
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Re: motorcycle tyres front & rear

Post by ChrisACT » Tue Mar 05, 2013 8:34 am

Thanks, Paul.

Incidently, can I get the details for the people who made your leathers? Looking at mine, they're full of perforated panels. Too many to bother having them altered. I'll have to have some made to meet the DLRA spec.

Thanks,
Chris

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zork
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Re: motorcycle tyres front & rear

Post by zork » Tue Mar 05, 2013 8:54 am

I got from the same guy Chris but needed to specify no perforations and no stretch panels which was an extra $40 I think. They are spot on.
http://www.ebay.com.au/sch/jazebnazar/m ... 1543.l2654
He operates out of surburban Vic and imports from Pakistan. All up $315 I think.

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internetscooter
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Re: motorcycle tyres front & rear

Post by internetscooter » Tue Mar 05, 2013 9:57 am

yes mine are the same guy but make sure that you stress the spec requirements very strongly and also hold off until the 2014 rules come out as I think there will be some changes.
Paul
---
DLRA #647
89.664 mph (aiming for 100mph+)
Vespa Labs [url]http://www.vespalabs.org[/url]

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ChrisACT
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Re: motorcycle tyres front & rear

Post by ChrisACT » Tue Mar 05, 2013 5:52 pm

Thank you gentlemen. Gives me time to sell my current suit. Never worn (except to try them on). Spewing.

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internetscooter
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Re: motorcycle tyres front & rear

Post by internetscooter » Tue Mar 05, 2013 6:51 pm

I would wait till the latest regulations come out before selling anything - I think my suit took 4 weeks, so you can leave it till the last minute

see http://www.dlra.org.au/forum/viewtopic.php?f=6&t=2100
Paul
---
DLRA #647
89.664 mph (aiming for 100mph+)
Vespa Labs [url]http://www.vespalabs.org[/url]

grumm441
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Re: motorcycle tyres front & rear

Post by grumm441 » Tue Mar 05, 2013 8:56 pm

ChrisACT wrote:
Fair enough. If it weren't for the fact that the "no front tyres on the rear" thing had been posted by the former chief bike scrutineer only a few months ago, I may not have paid it much attention.
hawkwind wrote:During my tenure there were 2 motorcycle accidents in which the riders where injured and needed hospitalisation . One stemmed from a bad speed wobble and the other from a rubber valve stem breaking away from the rear tyre ... both these incidents were investigated by the race director ,my self and others from our findings several rule changes were made being the mandatory use of metal valve stems , the banning of allowing front tyres to be used as rear tyres and the mandatory use of steering dampeners..
Also keep in mind that this is not Ack Attack we're talking about here. My bike will not weigh more than 200kgs wet (including the rider) and will be lucky to have 30HP.

Chris
Formally speaking or speaking as a former chief bike scrutineer, if it's not in the "new" rule book , you don't have to do it, however the front tyre on the rear was a well considered rule change after a fairly serious indecent. However if you can't find a 90/90 rear tyre you probably haven't looked at the Avon AM26 which is v rated and for front or rear fitment http://www.avontyres.com/motorcycle/roadrider
you should also note that we had a moratorium on leathers because of the amount of rule change applications that were received just prior to the 2013 meeting somewhat after the rule book had closed. So before you sell your leathers or buy new leathers have a look at the why all cow is flawed thread http://www.dlra.org.au/forum/viewtopic.php?f=6&t=2100
G
They make it
I make it work

hawkwind
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Re: motorcycle tyres front & rear

Post by hawkwind » Tue Mar 05, 2013 9:11 pm

[quote
Chris
Formally speaking or speaking as a former chief bike scrutineer][/quote] so grumm who is the new chief scrut now???
Vehicle......................A new creation.
Designed by................Troglodyte.
Engineered/ built by......Rustic.
Financed by.................Nickles & Dimes.
Rider......................... Tardus Vetus Inflatio

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ChrisACT
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Re: motorcycle tyres front & rear

Post by ChrisACT » Tue Mar 05, 2013 9:18 pm

Grumm, thanks for the Avon link. Looks like that's the answer.

As for leathers ...

My leathers have extensive perforations. It's not just a few little bits here and there. Most of the front of them is perforated to maximize comfort and (in my opinion) safety. Given that we're racing in the desert, I'd have thought keeping our brains from frying might be pretty close to THE top priority. After all, they won't let us run if we're drunk or stoned will they? How is suffering from heat stroke and dehydration any better?

Besides, if my bike catches fire, I'm outta there. That's what the lanyard kill switch is for after all. I'd rather take my chances sliding on the salt in my very high quality perforated leathers than trying to ride the bike until it stops (with only a rear brake) while methanol rapidly cooks me. There is nothing that we could ever wear on a motorcycle (within reason) which would withstand a serious fuel fire for 30 seconds without sustaining serious burns. The only answer is to let go and slide your arse on the salt.

I see this is a bit of a hot topic at the moment. Just thought I'd add my 2c.

grumm441
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Re: motorcycle tyres front & rear

Post by grumm441 » Tue Mar 05, 2013 10:13 pm

Chris
for the last three years while we weren't racing I have been going to Bonneville and working at Speed week, and from what I have seen there, when your bike is on fire, it doesn't matter how fast you are going, it's time to get off. However, the thing they consider is that if you have a fire, it will head to the low pressure area on the bike, which is between your chest and the fairing. The heat stroke thing is also a big concern, and I agree that February is the wrong time of the year for the meeting. On the Monday it was 54°. As for leathers, I was working on something to allow more flexibility regarding leathers, and fire resistant undergarments. and basing the amount of leather verses perforations on being linked to the current record in that class, much like the car suits.
I have about ten rule change applications, so far.
The plan was that a person running a 100cc bike could wear a different set of leathers to a person running on a 1000 cc two stroke.
This should probably still happen as Ross is a sidecar racer and understands this stuff

Seeing Brett De Stoops helmet after a 240+mph get off. A helmet that I can but for $66.00 wholesale...... I was pleasantly surprised.

Gary
I couldn't make it to the AGM. due to no one being able to tell me when or where it was being held. Organization??? Don't get me started!
I had to leave the lake to ring the most important person in my life on her birthday and by the time I got back it was over and Ross Brown was the head of Motorcycle tech.
Goggles even wrote a song about it
and I think I even have a picture of him singing it to Ross
That's about 1000 less phone calls I have to answer
G
They make it
I make it work

hawkwind
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Re: motorcycle tyres front & rear

Post by hawkwind » Wed Mar 06, 2013 10:53 am

Gary
I couldn't make it to the AGM. due to no one being able to tell me when or where it was being held. Organization??? Don't get me started!
I had to leave the lake to ring the most important person in my life on her birthday and by the time I got back it was over and Ross Brown was the head of Motorcycle tech.
Goggles even wrote a song about it
and I think I even have a picture of him singing it to Ross
That's about 1000 less phone calls I have to answer
G

Well fancy that miss an AGM and find yourself out of a position ,who would of thought :P :D yes but I still get calls hahaha ... for what its worth you did a great job :) ...Ill pass on my rule change submissions and thoughts to Ross.
Vehicle......................A new creation.
Designed by................Troglodyte.
Engineered/ built by......Rustic.
Financed by.................Nickles & Dimes.
Rider......................... Tardus Vetus Inflatio

Johno Senior
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Re: motorcycle tyres front & rear

Post by Johno Senior » Mon Mar 18, 2013 11:39 pm

Hi guys,

Yes I'm another bike person wanting to run a front on the rear. :D I want to run 21 inch front and back in a MG or MF 750 class

Unfortunately only front V rated tyres are available in 21 inch. I have read the rules and interpret them to say I can run a rear on the back. I have spoken to some US dudes who say at the SCTA events the front on rear presents no issues getting through tech !
I have also done some testing in the last month or so and am comfortable they ( avon) are safe. I have tested with a tyre temps at 27 psi and 50 psi, the temps front and back were almost the same at 135mph on the bituman, at lower pressure temps slight difference only. The bike feels good and is responsive on the tar.

So my dilema is at this stage I am happy with the front rear thing but being partially sensible I would like to know more about the incident where the view that an accident was caused by the front rear thing ? If it was a case of the wobbles there could be a million reasons , if the tyre delaminated was it a bias or radial ? what pressure and what was the load or bike weight ? If that information is available it would help me make a more confident decision.
Help ! :D cheers Johno

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