Another tire wear thread... D211GPA

erick1670

erick1670

Member
Meat;141231 wrote: I run 23/32 hot off track (after my second full speed session) and about 21/31 off the warmers.
tomseviltwin;141282 wrote: Yes, sorry, I should have specified that earlier. I use the med/hard rear. It seems to work well.
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thanks guys! I will do that on my next rear 209 or 211, b/c those med/soft almost got me yesterdey, they ware mush when I check then off the track:(.

I knew that they ware not going to last the whole day but I was hoping, that`s why I went eazy in the 3 sessions in the morning, anyways thanks!
 
needknees

needknees

New Member
JohnS;141809 wrote: Hoping this might help, Dave Moss discussing tire wear.

http://www.ustream.tv/recorded/6516891
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Haha, that's what I'm basing my guesses off of. It's a great video but it really is tough to tell what's happening to the tire without seeing it in person... which makes this thread all the more hilarious.

I've got another day coming up next weekend, I'll try dropping pressures down a little and see how that affects things. If it doesn't, I'll try messing with other things. I'm still fairly convinced this is a geometry issue, there's a similar front wear pattern in the Dave Moss video but was much much worse. It looked to be a buell front wheel. I might try raising the forks (dropping the triples) by 5mm or so to see if it helps with straightline stability under acceleration (had a nasty tankslapper about a month ago!) and with the tire wear.
 
sobottka

sobottka

New Member
needknees;141986 wrote: Haha, that's what I'm basing my guesses off of. It's a great video but it really is tough to tell what's happening to the tire without seeing it in person... which makes this thread all the more hilarious.

I've got another day coming up next weekend, I'll try dropping pressures down a little and see how that affects things. If it doesn't, I'll try messing with other things. I'm still fairly convinced this is a geometry issue, there's a similar front wear pattern in the Dave Moss video but was much much worse. It looked to be a buell front wheel. I might try raising the forks (dropping the triples) by 5mm or so to see if it helps with straightline stability under acceleration (had a nasty tankslapper about a month ago!) and with the tire wear.
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you probably need to raise the front (drop the forks in the triples) to fix straight line stability. dropping the front will make it worse.
where is your next event?
 
needknees

needknees

New Member
Wouldn't that take weight OFF the front and make straight line stability _worse_? What I am envisioning is lower the steer tube of the bike by raising the fork tubes in the triples, which would bring more weight to the front of the bike. Unless I'm mistaken :confused:

My next trackday will be at MidAmerica on July 31.
 
sobottka

sobottka

New Member
yes it would take weight off the front, too much weight on the front will cause straight line instability. unless you only get headshake -on the gas -at slower speeds -over bumps and have high speed stability, would you want to raise the rear or drop the front.
 
Meat

Meat

Member
Lowering the front/raising the rear will cause less stability. I had swapped out tires of a different geometry (didn't read the sidewalls of the tires) without realizing the tire outer diameters were different than I was running previously. I was at Road Atlanta and normally hit terminal velocity on the back straight, but had to keep it under 120 mph do to head shake (speed wobble). I raised the front and it helped wobble go away.

You actually have 2 things working against your stability at the same time, forward biased weight and geometry.

Instability is a good thing to a point as it allows quick turning, so don't go overboard making your bike stable or you will end up with a bike that rides like a chopper and doesn't want to turn.
 
slowpoke

slowpoke

New Member
I tried the 211 GPAs this year and was impressed at that overall improvements from the 209. That said, I have a question: what compound is the front tire? Is it a soft?

I ran the soft compound, and while the grip was awesome, I had similiar tire wear. One of the contributing factors was my geometry which had too much weight on the front. I lowered the rear a bit and it did clean up but still a little ugly. I'm on a 600 and tend to ride the front pretty hard so I'm shagging the soft front in two days, but that's CRing and some 'A' sessions. I could probably get a 3rd day, but I'm very conservative with replacing front tires.

In the future, I'd prefer a medium front for more durability and better wear- just my .$.02 -
 
needknees

needknees

New Member
Slowpoke -- the D211GPA is available in either a soft or medium front, and soft/med or med/hard rear. I went with a medium front and the med/hard rear.

Regarding stability... I'm more concerned about the wear on the front than stability at this point. I've come to the conclusion that my tankslapper was 95% caused by me. A combination of being too tense and readjusting my weight / moving to shift. The other 5% was the fact the track had developed bumps on the straight from cars (this has sense been smoothed out), the front was light from hard acceleration, and I shifted the exact moment hit one of those bumps. Combine that with the fact I was too tense and you get this:

http://www.youtube.com/watch?v=GvHtChodNk0

An eye opening experience for sure.

The rest of that day and all of my next day (although it was at a different track) I concentrated on staying light on the bars and the only time I got any headshake was a _little_ wiggle when I got an exceptionally good drive out of corners. So not very often :p
 
Macon663

Macon663

New Member
Just to clarify, there is no medium/hard option for the rear tire. That tire only exists in the ntec 211.

Released at mid-ohio (for AMA only at the moment) was a medium/hard front. Its supposed to be much better than the soft or medium.

http://www.dunlopracing.com/DETAIL-D211GPA.html

D211
Fitment specs Rear: 190/55x17 D211GP-A
Recommended Rim range (5.50-6.00), Best Rim (5.50),
Width (199mm/7.83"), Diameter (643mm/25.34")
Available Compounds: Soft and Medium
Suggested Pressures: Hot on the warmers 23psi, or cold 21psi
 
needknees

needknees

New Member
I'll be damned. I was going off what the TDS listed...

http://www.trackdaystore.com/Dunlop-Race-Tires-D211GPA-DOTs-120-190-Set_p_412.html

Trackday Store wrote:
Fitment specs Rear: 190/55x17 D211GP-A
Recommended Rim range (5.50-6.00), Best Rim (5.50),
Width (199mm/7.83"),
Diameter (643mm/25.34")
Available Compounds:Soft/Medium and Medium/Hard

Maybe a typo?

edit - Read through the dunlop link, sounds like it may be a "med/hard" even if they're not listing it as such.

Dunlop Racing wrote:
For the D211 GP-A rear tire, all-new, proprietary compounds are formulated from polymers and resins for the high-stiffness and high grip treads to significantly improve grip, stability and durability, with better resistance to repeated heat cycles. For AMA Pro Racing competition, racers can select from a “soft” front or a “medium” front, and a soft or medium rear (both rear choices are Multi-Tread).
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sobottka

sobottka

New Member
the dunlop info is correct. the tires are labeled medium or soft (or hard for the new front). i recommend the med/med combo (or med/hard)


that headshake in your video was nasty. even with good geometry you could get headshake on bumps like those
 
sobottka

sobottka

New Member
needknees-thought you may be interested in this...


these two pics show my tire after 1 race at blackhawk. my forks were set-up for road america (STIFF) and the wear pattern is very similar to yours. if i had ridden this tire more with these settings im sure it would have looked exactly like yours.
014.jpg

012.jpg


this pic is a new tire (red stripe on rim) that has 2 races at blackhawk on them after softening the spring and compression a little
007-1.jpg
 
pajixxer

pajixxer

Brad Burns
Control Rider
needknees your front looks like a bad rebound tear, looks like you need to add some, and the rear could possibly be a compression issue, ive heard the rear are sensitive to compression... the first set i ran of those this year i did that to the fronts, added rebound and they have been good.
 
A

alphamale

New Member
NeedKnees: I've corrected front tire wear issues that look exactly like yours by adjusting the PSI on my bike. That is a debris field that is not being cleaned off because the front tire is not getting hot enough. Take about .5 to 1 PSI out of the front tire and see if that doesn't clean it up. I've had tires that looked worse than that clean themselves to look good as new.
 
needknees

needknees

New Member
Thanks for the info everyone. It sounds like the 211s like to be run ~21/31 off the warmers instead of 23/33 like dunlop recommends. I didn't make it to the track at the beginning of this month but will be going Aug21 to the same track I ran these at earlier. Weather conditions should be similar, I'll try dropping the pressures down a little more and see if it doesn't clean that odd wear pattern up.
 
M

mpz

Member
Not going to start another "tire thread" but just wondering. Would it pass tech?

IMG_00781.jpg


Complements of 3 days at Putnam :)
 
M

mpz

Member
^ If I flip it, I should be fine for 1 more Putnam weekend :dunno:

It wasn't really a serious question. I was warned during SED tech to watch the rear tire. I got 1 more day out of it after that with another organization but experienced couple slides towards the end of the day. When I went through tech noone even made a comment and there were 3 tech guys around the bike - one was teching while other 2 just looked on. That tells you something...

:congrats: NESBA
 
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