Dunlop 2012 US Made GP211-A DOT race tire test

2012 Dunlop 211 GP-A tire test at Thunderhill Raceway Park

 

Date:5/29/2012

Ambient temps 80F with track temps at 105F

Cold pressures 20psi rear 30psi front

Tires provided by For the Track LLC: (forthetrack.com / sales@forthetrack.com)

 

* Medium plus front 120/170 x 17

* Rear  new for 2012: 190/60 x 17

 

 

Bike: 09 Yamaha R1

 

Bike settings:

Forks: 08 R1 with Ohlns 25mm fork cartridges

Shock: Yacugar race shock

 

Chassis:

Fork height at +4mm

Fork preload 6 turns in (1.0kg springs)

Fork rebound 14 clicks out

Fork compression 5 clicks out

 

Yacugar race shock at 295mm

Preload at 4.5 lines (11kg spring)

High speed compression at 21 clicks out

Low speed compression at 18 clicks out

Rebound at 32 clicks out

 

Gearing: one tooth down on the countershaft sprocket, stock chain

 

 

Session 1:

-       scrub in tires (cold, no tire warmers)

-       assess geometry and chassis

  • lots of feedback immediately from the hard carcass tires
  • front gain of 5psi rear gain of 4psi hot off the track
  • excellent stability under braking with little sidewall deflection
  • excellent drive grip off fast corners
  • suspension constantly working – more compression needed
  • too much rear weight bias forward effecting braking performance from excessive weight transfer.

Given the braking stability and acceleration grip the cold pressure was a good starting point. A chassis and suspension change was required immediately.

 

Changes:

Add 3 turns of rear ride height 1.5 turns of rear ride height to raise the rear of the bike the a little to assess the effect on geometry and the weight transfer between braking and accelerating.

 

Shock:

-       preload unchanged

-       high speed compression to 18

-       low speed compression to 14

 

 

Session 2:

-       brake hard in turns 9 and 14 to assess weight transfer

  • uphill braking in Turn 9 excellent
  • downhill braking in Turn 14 improved but still too much weight transfer from the rear
  • bike transitioned much easier in T3,4 and T11, 12, 13

 

The rear ride height change validated the need to raise the back of the bike but in so doing the weight transfer problem was not fixed.

 

Changes:

-       add 3 turns of rear preload to the shock

-       high speed compression 14

-       low speed compression 12

 

 

Session 3:

-       assess turn in on high speed turns 1 and 8

-       assess braking in Turn 14

  • much more precise turn in at high speed corners with gentle pressure needed on the bar to initiate rather than waiting for the weight transfer to occur and then turning in
  • downhill braking was as hard as I liked rather than manage braking

 

Changes

-       shock rebound to 38

-       high speed compression to 13

-       low speed compression to 10

-       rebound to 38

-       remove 2 turns of preload on the front forks

 

 

Session 4:

-       assess turn in on T3 and T5

  • turn in was not effected by the rebound change in slowing down the weight transfer in the slow technical corners
  • the bike would still flick into the corner with even bar pressure rather than more positive “snap turn” pressure (I prefer to control the bike’s pat not manage it).

We were experiencing poor tire wear on the front tire and raised the hot pressure to 36 psi. Excessive wear was also evident on the rear tire, so we took the rear tire off and ran it in the opposite direction. We increased the hot pressure to 26psi.

 

NOTE: only the 2012 US GP-A is reversible

 

Final settings:

Chassis:

Fork height at +4mm

Fork preload 4 turns in (1.0kg springs)

Fork rebound 14 clicks out

Fork compression 5 clicks out

 

Yacugar race shock at 298mm

Preload at 4.5 lines (11kg spring)

High speed compression at 13 clicks out

Low speed compression at 15 clicks out

Rebound at 38 clicks out

 

As you will see from the photos at the end of the day, the tires cleaned up perfectly in the rear and the front improved slightly suggesting a geometry change of 2mm to take weight off the tire (ie: raise the front end).

You will also notice that the tire is well below the wear marker. I did feel the grip going away at that point but there was no sudden slide or snap out from underneath you on braking or accelerating. Certainly a big step up with the front tire and a much better and more durable rear tire for this years AMA spec tire.

 

 

Summary:

-       tires need to be on the warmers for 45 minutes first thing in the morning

-       great braking stability in the front tire under hard braking

-       lots of feed back from both ends of the bike which I like

-       great acceleration grip off the fast corners at significant lean angles

-       hot pressures set at 34psi front and 24psi rear off the warmers. You should experience a 2psi gain from that point after 4 laps.

 

The tires are very sensitive to chassis geometry and hot pressure so spend all your time on geometry initially before then moving on to suspension changes! Take as long as it takes to get the chassis right! Otherwise you will burn up the rear tire in 20 minutes.

 

 

Tire wear pictures:

 

 

 

 

NOTE: – the slight pressure tear on the tire due to initial under inflation that is healing