Bridgestone V front YCX Tire test
To order this tire online, go to: http://viets-performance.com
June 7th, 2012 at Thunderhill Race way Park, CA
Ambient temp: 90F
Track temp 125F
Bike: 2009 Yamaha R1
Nitron Race Shock
Spring rate: 631nm
Installed preload unknown
Current preload setting at 21 clicks in from full soft
High speed compression 8 clicks out
Low speed compression 10 clicks out
Ride height +2.5mm
Shock length 295mm
Shock builder: S. Maskell
Factory service internal recommendation at 12 – 18,000 miles
Fork settings:
Fork height at +2mm
Fork preload 4 turns in (1.0kg springs)
Fork rebound 14 clicks out
Fork compression 5 clicks out
Gearing: one tooth down on the countershaft sprocket, stock chain
Thanks to:
- Jeff Viets of Viets Performance for the tires
- Matt Montero open track day
- Thunderhill Race way Park
TIRES:
REAR: YCX Bridgestone (white band) 190/645 x 17
Cold pressure 24psi on a calibrated gauge
Set at 28psi after 30 minutes at 180F on warmers
Hot pressure after 4 laps set at 30psi
FRONT: V profile YCX Bridgestone (white band) 120/600 x 17
Cold pressure 26psi on a calibrated gauge
Set at 21psi after 30 minutes at 180F on warmers
Hot pressure after 4 laps set at 32psi
Session 1:
- scrub in over 4 laps and come in to set hot pressure
- get a feel for the different profile in transitions
- asses sidewall stability under heavy braking load
The tire immediately gave notice about it’s profile. I spent most of the session feeling out turn in points and counter steering bar pressure amounts. It took a little while to adjust to the subtle but required changes for turn in markers and bar pressure before I could increase the pace with certainty.
Changes:
- add 2 turns of fork preload
Session 2:
- work on high speed turns
- assess throttle on points for earlier throttle input due to profile
Adjustment to turn in points on high speed turns was very slight. The area that required the most concentration was bar pressure. I found that while subtle input was needed to initiate the turn, once the bike was on the side of the tire there was not need for further bar pressure management. I did psychologically go for the throttle earlier in the turn to even the load on the chassis and started to steer the bike that way after the turn was initiated. This isn’t required but felt intuitive to me while on the bike.
Changes:
- none
Session 3:
- assess carcass stability under straight line braking
- check sidewall stability under trail braking
With the forks raised prior to the test to +2mm to compensate for the smaller tire circumference with this profile, braking stability was good in a straight line, even when the brakes very aggressively applied rather than smoothly. Weight transfer was predictable and the carcass held up under severe loads. At no time did I feel the tire flatten out to the point that the bars would row side to side.
With trail braking, I took my time creeping up on edge grip limits. I could feel the sidewall flatten out as the pressure was applied but I could also feel the shape of the carcass return as brake pressure was released to allow me to provide slight corrections towards the end of trail braking.
NOTE the trail braking wear lines in the tire circumference on each side.
The most noticeable part of this session was the subjective “feel” of how much front tire was on the ground. It didn’t feel flat as in a literal V, but the amount of grip and tire actually on the ground was significant over the Bridgestone round race slick I compete on. You can really feel how much tire is on the ground and it seemed to me that it was double the amount of my race slick.
Changes:
- none
Session 4:
- assess quick transitions
You would think with a V profile tire that it would require quite a bit of effort to flick the bike from side to side. At this track between turn 3 and 4 the transition is quick, using the throttle to suddenly load the front moving from right to left. The same is true of turn 5 with an uphill/downhill transition thrown in to the mix. Quite the opposite was true which honestly surprised me. The bike readily flicked from side to side either from brakes or throttle closing and I had to be wary of not flicking the bike over. Thank good geometry and rebound balance for the assist, but still – it was a real surprise how quickly the bike transitioned.
Changes
- none
SUMMARY:
Make sure you correct your geometry before trying any new tire(s)!
This is a great front tire especially for those riders that point and shoot a bike. It is remarkable how quickly the tire will roll onto its side and then let you know it is planted. The feel of how much tire is on the ground takes a little getting used to and you have to fight yourself not to immediately go for the throttle to unweight the front slightly. You can trust the tire and there’s a ton of side grip no matter the camber of the track and the braking skill that you need.
I’m too used to my small bike and maximum lean and corner speed to want this tire on my bike right away. However for technical tracks that require a lot of transitions and very quick turn in, this would be an amazing tire for me to use under those circumstances.
Looking for the on track video? It is here: