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Aug 27th 2016, 10:43 AM   #1
 TOPDECK's Avatar
 
  Jul 2016
  Mill Creek, WA

  2016 ZX-6R 636, 2017 Husqvarna 701 Supermoto
Interesting Tire wear and suspension

Hello everyone,

I am looking to get some insight on my strange tire wear after a track day. I had my first track day at PRW with 2-Fast and I am HOOKED! But...all that fun highlighted a bit of a suspension issue I think.

First a history lesson:

Bike: 2016 Ninja ZX6R 636 ABS
Tires: Bridgestone Battlaxe Hypersport s20 @ 32lbs front and rear (cold)
Track: Pacific Raceways 90-95 degrees ambient air temp
Rider: 190lbs +/- 5lbs

This is my first bike in a long time and my first supersport. However, some light spirited riding in the cascades a week or so after I bought the bike clued me into the fact that the suspension was all wrong.

The front end dived really deep upon corner setup braking then promptly rocketed back up once the throttle was cracked causing some interesting stomach in the throat moments.

I took the bike down to KFG (from Mill Creek! LOL) and they basically said that the suspension was all over the place and made no sense at all for any rider. Guy at the factory must have been hung over...whatever. But they did say that I was pretty much at the upper limit for my rear spring, and couldn't get a really good static sag on the rear and said I could probably do with a new spring in the back.

But, the bike INSTANTLY felt better. Even making a simple left hand turn at a stop light felt better. The bike tracked better, felt more planted and didn't want to stand up and "say hi" mid corner. Took a nice ride with some PNWMoto people out on hwy 20. Same thing. Felt great.

Then came the track day. Bike still felt great. Had a little bit of front end shake / wobble on exit of the Bus Stop and going over the hump before the downhill to turn three, but I am attributing this to the front end getting light on heavy acceleration. The back end also felt fine. It felt planted and I was getting plenty of grip. On the front straight I felt no issues at all.

But my rear tire is telling a different story...

Pay no attention to my chicken strips!


There is a very noticeable (debris field?) area of melted rubber all the way around the left side in a scallop pattern. But does not look to continue up over the top of the tire:










The right side seems to be a lot more even albeit less melted. In my mind that would make sense since PRW is I guess more left-hand-centric since the track runs counter-clockwise and the harder accelerations at corner exit are on left-hand turns; turn 2, turn 4, and 7 8 and 9 are all basically one giant left-hand corner as the bike is leaned to the left from turn 7 to the Bus Stop. Or maybe I don't know what the hell I am talking about.

right side






At any rate, it seems to me like either my tire was under-inflated and was buckling upon hard left hand acceleration or I have too much rebound and my tire was skipping along the road surface. I did not notice any ignition cuts or any action on the traction control meter.

Here is my invoice from KFG. I don't remember the tech adjusting the rear rebound, only compression. Perhaps he did, I don't know. But the invoice shows the settings.



Any insight on this issue would be great as I am trying to learn as much as I can!

Thanks!

Edited by TOPDECK on Aug 27th 2016 at 11:15 AM Reason: spelling
Aug 27th 2016, 11:51 AM   #2
 Squidly's Avatar
 
  Jan 2016
  Bothell

What stands out to my untrained eye are the sections with no melting on the left side of the tire. You could probably do with tweaking the rebound a little the next time you're out at the track, but I couldn't tell you which direction to go.

Don't worry too much about the melting itself, that's pretty normal.
Attached Thumbnails
Interesting Tire wear and suspension-tire-wear.jpg  
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Aug 27th 2016, 12:14 PM   #3
 TOPDECK's Avatar
 
  Jul 2016
  Mill Creek, WA

  2016 ZX-6R 636, 2017 Husqvarna 701 Supermoto
Thanks for the reply! It's strange, the rubber in those areas in indeed melted but is smoother than the rest. It looks like the rubber is coming / scraped from those areas and being deposited in the rougher areas.
Aug 27th 2016, 03:38 PM   #4
 Pavement Tested's Avatar
 
  Jan 2016
  Bremerton

  '12 Concours14, '08 GSX1300R, '06 GSX-R 750
The leading edge of the tread is smooth because the carcass flexes and that area essentially "folds" into the recession of the sype and away from the track surface. It's pretty normal.

I believe that Pacific is a mostly left hand turn track like the Ridge so I makes sense to me that your tires is worn more on that side.

Also, what you call chicken strip I like to call error margin or insurance. If you're running at the very edge of the tire your contact patch is smaller and you have nothing left in and emergency.
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Aug 27th 2016, 11:06 PM   #5
 
  May 2016
  SW Portland

Do a Google/Youtube search for Dave Moss. He has a ton of helpful content out there.
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Aug 28th 2016, 12:02 AM   #6
 Damon Mon Wai's Avatar
Inspector Gadget
 
  Jan 2016
  Seattle

My opinion and I'm NOT an expert on reading tires, is the tire was getting a little hot because it looks like hot tearing. I'd bump up air by 1-2 lbs. Also you may need to add a click or two of rebound damping. it looks like the trailing edge of the groove is raised slightly. If the trailing edge is raised it usually needs more rebound, if the leading edge is raised usually needs less rebound.

How did the tire feel? Was the grip good? Did it start feeling greasy after a some hot laps?

Getting your tires to "read" perfectly doesn't always mean they will give the best grip at those settings. Getting your tires to read perfectly usually will give you the best tire wear, basically making the tire last the longest. Its totally possible to have a "bad read" on a tire but at the same time getting the best grip from it. The drawback is tire wear, the tire will wear out a lot faster. But most racers will happily trade wear for better grip, as long the tire lasts the whole race. For those of us that just do track days, tire wear is usually more important then absolute grip.
Aug 28th 2016, 01:38 AM   #7
 Smonky's Avatar
 
  Jan 2016
  Vancouver WA

  15 Aprilia Tuono V4R
Did you run 32psi on the track day?
Aug 28th 2016, 06:55 AM   #8
 JIMMYRAY31B's Avatar
 
  Jan 2016
  England

  2014 Ducati Hypermotard SP
Looks to me to be cold tearing. 32psi seems a bit high for track use on those tires. I would try starting with 30psi next time.
Aug 28th 2016, 12:46 PM   #9
 Damon Mon Wai's Avatar
Inspector Gadget
 
  Jan 2016
  Seattle

Quote:
Originally Posted by JIMMYRAY31B
Looks to me to be cold tearing. 32psi seems a bit high for track use on those tires. I would try starting with 30psi next time.
I think if it's cold tear the tears would be deeper. The tears don't look that deep. But it's hard to tell without seeing it in person. I think the S20's are more of a street tire vs a track tire, like the Q3's. A street tire usually needs higher pressures compared to track tires. Also air temp and track temp were very high that day. All that taken into consideration with only the pics we can see makes me think hot tear.
Aug 31st 2016, 09:29 AM   #10
 TOPDECK's Avatar
 
  Jul 2016
  Mill Creek, WA

  2016 ZX-6R 636, 2017 Husqvarna 701 Supermoto
Hey everyone! Thanks for all the info!

After reading through the thread, doing my own research and talking to a few people in person I think it is most likely a little bit of two things.

The tearing / wear is abnormal in width around the tire because my rebound might be a bit to fast. The rear of the tread is also raised a bit with a debris field which my research shows is a sign of too fast of a rebound.

Secondly, I think I had a couple pounds over what I should have for my tire on that hot day. I probably should have started a bit lower and let them run up to 30 31psi hot. 32 cold I think was just too much. But I don't know, because I didn't check them right when I got off the track. Next time I will have my wife just outside the exit with a pressure gauge and a pump to adjust after the first few laps. I am new at this so, just trying to figure out some personal protocols.

I will probably have KFG take a look next I am out there as well and have them make some tweaks.

Thanks again!

Also if anyone else wants to chime in, please do!
Aug 31st 2016, 11:03 AM   #11
 Squidly's Avatar
 
  Jan 2016
  Bothell

Quote:
Originally Posted by TOPDECK
Secondly, I think I had a couple pounds over what I should have for my tire on that hot day. I probably should have started a bit lower and let them run up to 30 31psi hot. 32 cold I think was just too much.
Just so you know, lower tire pressure makes for more heat. If you think the tire is getting too hot bump the pressure up 1 or 2 psi.
Aug 31st 2016, 01:21 PM   #12
 
  Jan 2016
  Beaverton

  '13 636, '14 N1k, DR650
Kinda late to the party, but I'll throw my $1.05 in here, since I have a tiny bit of experience.

I have the same bike, and went through the progression of riding on the street, then track days, and now it's officially a race bike.

From the dealer it was setup for about a 130lb rider. It was about full soft on most settings.

The stock suspension is fairly poo compared to other bikes in its class (at least where the track is concerned). I also took mine to Barry, and he did his best to make it work, but the suspension itself has pretty low limits. You'll get odd wear patterns on it until you replace the shock - or slow down.

As others have said, playing with tire pressure/temps gave better results than fiddling with adding/removing a click or two of rebound/dampening.

Also spring for a steering damper. You're probably right, it's mostly due to heavy acceleration, but that's another part Ninja's don't have that some other 600s do come with from the factory.
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Sep 2nd 2016, 04:04 PM   #13
 TOPDECK's Avatar
 
  Jul 2016
  Mill Creek, WA

  2016 ZX-6R 636, 2017 Husqvarna 701 Supermoto
Thanks Andenthal,

Yes I think a steering dampener is in my future. I get bar shake even getting onto the fwy while shifting from 1st to second gear (pinned of course ), but it is basically the same scenario as jumping out of the buss stop to the straight.

I am going to work on her over the winter so she is more ready for track days next season, and since I don't think replacing suspension components will be on the to-do list, I will be concentrating on dialing the tires and pressures first thing. Not to say I don't want to work on the springy parts, I will have Barry take another look out at the track, or maybe even Dave Moss depending on his schedule next year.

My wife is pushing to have me only ride track, but I don't think she understands the cost of turning my bike into a track only / race bike. I would be interested in knowing the parts you used and sources.

Thanks!
Sep 2nd 2016, 05:24 PM   #14
 DocB's Avatar
 
  Feb 2016
  Poulsbo, WA

  Aprilia RSV Mille, CB77, CB750K, CB750F
Um, it's steering damper. A dampener makes things wet.

Sent via SAMSUNG-SM-G920A
Sep 2nd 2016, 06:59 PM   #15
 TOPDECK's Avatar
 
  Jul 2016
  Mill Creek, WA

  2016 ZX-6R 636, 2017 Husqvarna 701 Supermoto
Quote:
Originally Posted by DocB
Um, it's steering damper. A dampener makes things wet.

Sent via SAMSUNG-SM-G920A
Yeah I said what I meant. What gets me wet is my own business.
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