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Discussion Starter · #1 ·
Has anyone noticed in the pictures of the new 1098 with Bridgestone tires that the front tire tread is facing the opposite direction of the rear tire? I thought that was interesting....anyone know why? I'll be investigating....
 

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when a tire has an "arrow" shaped tread on it, the front tire is very prone to a phenomenon called "feathering" if mounted in a direction that has the "arrow" pointing forward. Feathering is brought about during heavy braking and especially during trail braking; the tire will build a ridge on the front side of one tread groove and a flat spot on the backside of that same groove. The process continues over the whole tire, each rotation and will eventually make the tire look like a small paddle tire.
Reversing the tread changes the contact pattern and prevents this occurence.

Also, I believe the Dunlop D207's of the late 90's were the first to demonstrate this phenomenon on the track.
 

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Dude, that is what I call laying some knowledge down on us common folk, haha. No really that is actually a very interesting piece of information and makes perfect sense after you described the condition. Definitely sounds like it would be more of an issue during track use when the tires are warmer and under such forces. Brings me to a good question, what tires does everyone equip their Ducs with? I personally use the Michelin Pilot Sports and have been very satisfied with them, great grip in all situations and they have like a wavy tread pattern... maybe that prevents the feathering van-man refers to... anyways, do tell.
 

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Discussion Starter · #5 ·
Bridgestone's

van-man --> I am talking about new tires, never used. See attached picture.
 

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Discussion Starter · #6 ·
addicted2spd said:
Dude, that is what I call laying some knowledge down on us common folk, haha. No really that is actually a very interesting piece of information and makes perfect sense after you described the condition. Definitely sounds like it would be more of an issue during track use when the tires are warmer and under such forces. Brings me to a good question, what tires does everyone equip their Ducs with? I personally use the Michelin Pilot Sports and have been very satisfied with them, great grip in all situations and they have like a wavy tread pattern... maybe that prevents the feathering van-man refers to... anyways, do tell.
I generally use Pilot Power 120/70 and 190/55 for the street and Power Race PR1 and Medium Soft for track. Although I tried Pirelli Dragon Slicks recently and dropped 2 seconds with NO other changes except the appropriate tire pressure. Same size tires 120/70 and 190/55.
 

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No need for the picture duc1098, I know what you are talking about, and my answer was in regard to your question. Tire makers reverse the tread pattern on front tires like that to prevent "feathering". Simple as that.

Now as far as tire preference, I LOVE michelin pilots! I have run them since first introduced back in '99. I flirted with dunlop and pirelli, who both offered better support for us endurance racers, but nothing works as well as that fat white lumpy guy. They are more consistent throughout the tread life of the tire, less prone to heat damage, and yes, feathering is much less of a problem with the concentric tread. Although, a tire groover is a must for wet races which do not permit full on rain tires.

Also, if you were able to drop 2 whole seconds by simply changing the tire on your bike then you should look at the dimensional differences between the two tires. You may have inadverdently stumbled on to a more favorable geometry setting for your bike. Slicks are usually much more triangulated, making the tire taller in the overall, allowing a faster turn-in, and providing a wider contact patch for drives out of corners.

The first pilots were very rounded, and low; which screwed up the geometry on alot of bikes that were switched. Cancelling any traction advantage that was gained through the switch. But, Michelin corrected that problem soon after, and while still tame, is a very solid tire all the way around.
 

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Here is an idea for the board. Start a section called "ask the expert". You, sir, are the tire expert.

Damn, that's some knowledge.

CAG
 

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Discussion Starter · #9 ·
van-man said:
No need for the picture duc1098, I know what you are talking about, and my answer was in regard to your question. Tire makers reverse the tread pattern on front tires like that to prevent "feathering". Simple as that.

Now as far as tire preference, I LOVE michelin pilots! I have run them since first introduced back in '99. I flirted with dunlop and pirelli, who both offered better support for us endurance racers, but nothing works as well as that fat white lumpy guy. They are more consistent throughout the tread life of the tire, less prone to heat damage, and yes, feathering is much less of a problem with the concentric tread. Although, a tire groover is a must for wet races which do not permit full on rain tires.

Also, if you were able to drop 2 whole seconds by simply changing the tire on your bike then you should look at the dimensional differences between the two tires. You may have inadverdently stumbled on to a more favorable geometry setting for your bike. Slicks are usually much more triangulated, making the tire taller in the overall, allowing a faster turn-in, and providing a wider contact patch for drives out of corners.

The first pilots were very rounded, and low; which screwed up the geometry on alot of bikes that were switched. Cancelling any traction advantage that was gained through the switch. But, Michelin corrected that problem soon after, and while still tame, is a very solid tire all the way around.
I might have dropped the time because I felt more confident? Not sure. I usually run Michelin Power Race PR1 (120/70-17) front and Medium Soft rear (190/55-17). I switched to Pirelli Dragon Slicks of the same sizes with a SC1 front and SC2 rear. The bike really didn't feel any different. In fact I was surprised at how little change there was between these same-sized tires made by different manufacturers. The real headache was early in last season setting the bike up to run a 190/55 rear tire! The Michelin is 1.1" taller than the 190/50! Consequently I had to buy another new chain, another sprocket (went down 2 in the rear from where I was, which was 4 over stock so the net is two over stock now), and I ended up reducing the rear shock length by 8 mm and went with a slightly softer rear spring - this made the bike feel right again and my cold tearing problem went away as well.

Btw, thanks for the answer about 'feathering' - I did not know that. So I presume the that's why Michelin distributors at the track are telling me I can reverse the tire if I wear one side too much, for example, at a track like Barber where it's mostly biased to the right and I'll wear my Power Race tires to the wear indicator on the right and the left will have plenty of life left on it?
 

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duc1098 said:
I might have dropped the time because I felt more confident? Not sure. I usually run Michelin Power Race PR1 (120/70-17) front and Medium Soft rear (190/55-17). I switched to Pirelli Dragon Slicks of the same sizes with a SC1 front and SC2 rear. The bike really didn't feel any different. In fact I was surprised at how little change there was between these same-sized tires made by different manufacturers. The real headache was early in last season setting the bike up to run a 190/55 rear tire! The Michelin is 1.1" taller than the 190/50! Consequently I had to buy another new chain, another sprocket (went down 2 in the rear from where I was, which was 4 over stock so the net is two over stock now), and I ended up reducing the rear shock length by 8 mm and went with a slightly softer rear spring - this made the bike feel right again and my cold tearing problem went away as well.

Btw, thanks for the answer about 'feathering' - I did not know that. So I presume the that's why Michelin distributors at the track are telling me I can reverse the tire if I wear one side too much, for example, at a track like Barber where it's mostly biased to the right and I'll wear my Power Race tires to the wear indicator on the right and the left will have plenty of life left on it?
Geez, that sounds like it was quite a bit of set-up change you had to do. Still, slicks tend to have a broader contact patch at the 45 degree points on each side to allow for more powerful drives off the corners. If you were having cold tearing problems, no doubt due to the loads of torque you were subjecting your tires to, then I guess a slick would be like putting on some magic winged shoes :naughty: Whatever you did, right it down! Because finding that much time all at once is RARE!!! Usually, the only time I see people make that much progress all at once is when they are first learing to race, and I can tell that isn't the case with you.

I never liked turning a tire around once it was worn, simply because I forget. I will be hammering all the left handers, and then when I hit a right I'll end up dumping it because the right side couldn't handle the same stress since it was worn out.

There are two main wear points to tires that you have to be aware of when racing (you probably know this, but I'll say it so that someone else who doesn't may learn something helpful): Heat cycles and tread life. Everytime you get on the track and run a session, you heat the tires up. Once the session ends you pull back into the pits and the tires cool back down again. This makes one heat cycle. A tire can only handle X number of heat cycles before it is finally baked so much that you just can't get it hot enough to be sticky again. When this happens the tire is junk for the track no matter how much tread is left on it.

The other, tread life, is important too. To a point, thicker tread(rubber) allows a tire to grip the road surface more firmly by creating a bigger, more consistent contact patch on the road. Additionally, the flexibility that the thicker tread offers helps the bike to traverse imperfections in the pavement. So, for obvious reasons, you wouldn't want to go frollicing around the track with a tire that is bald on one side:however, a little uneven wear is nothing to worry about. That said, if it is down to the tread wear indicator, its time to sell those tires to some street goons and go by some new ones. No one wants to lay their bike down because they are trying to milk every last penny from a set of tires :banghead:
 

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Discussion Starter · #11 ·
Van-man, I agree about 'milking' tires - not a good idea. I can only get about 2.5-3 days out of a front tire on track days and 1.5-2 on a rear tire. I don't use tire warmers but I plan on getting a set this Winter for the new upcoming season. I don't know how much additional life they will give me BUT I will get up to speed a lap sooner which can equate to a 10% increase in actual 'at-speed' track time. Over a season of 15+ track days @ $200, on average, each time I go the tire warmers will almost pay for themselves!
 

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The basic reason for directional arrows on tires is the normal construction method whereby the tread starts out as a flat belt whose ends are spliced together into a hoop around the tire carcass. The joint is scarfed or bevelled so the ends overlap to get good bonding strength. If you drive the tire the wrong way, you try to rip open this scarf joint (peel the top layer back) if you drive the tire the correct way, the scarf joint tightens up.
 
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