"What tire should I run?" is an incredibly common question in the world of autocross and one that can certainly elicit many suggestions and strong opinions.
For this coming SCCA Solo-Autocross season, it is a question that even seasoned veterans might be facing as one of the best-performing tires, the Bridgestone RE71-R is being discontinued with no replacement from Bridgestone being offered. While most people are going to switch over to the Yokohama ADVAN A052, Falken Azenis RT660, BF Goodrich G-Force Rival-S, or the Goodyear F1 Supercar 3, there are a couple of other tires hitting the market for this season.
I have decided to purchase one of these new potential contenders, the Kumho Ecsta V730.
The Kumho V730 courtesy of Tirerack's website
There has been very little information out on these tires yet, so I wanted to put together a comprehensive post with my own first impressions as well as input from some people who have driven them.
EDIT: Here is my second review on this tire now that I actually have spent time driving on and autocrossing it: https://opposite-lock.com/topic/14232/kumho-v730-autocross-review
What is it?
The Kumho V730 is Kumho Tire's latest venture into the 'Extreme Performance' 200-Treadwear-Tire-War. It is replacing the V720, which was more or less hot-garbage due to a rather serious delamination-issue.
An example of the delamination on a Kumho V720
While this would be very concerning and probably shying people away from running another Kumho tire, we also have to remember that Kumho also developed the V720-ACR. The V720-ACR was a tire specially developed for the 2016 Dodge Viper ACR and while only available in two sizes (Which makes it illegal for SCCA competition), it is regarded as one of, if not the best performing 200 treadwear tire of all time.
The Kumho V730 seems to have taken most of its design cues from the V720-ACR rather than the V720 (It appears that it is not the same compound as the V720-ACR, although I have not been able to 100% confirm that yet). The outer half of the tire is effectively a slick as the tread pattern cut into those sections are only roughly 2-3/32nds deep at their deepest (Based on my measurements) while tapering up as they get closer to the center. Towards the inside, there are two large channels to move water with a thick center-rib. Once again, the tread pattern on the rib isn't very deep at all. Finally, the inner-most tread has a trapezoidal design that is a shared trait between all the Kumho Tires mentioned.
The V720-ACR on the left and the new V730 on the right
When I got these tires in a few days ago, my first thoughts were "Wow, I know I'm not going to use these in rain!" This tire has pretty much sacrificed all aquaplaning protection in place of maximum dry grip. Like prviously mentioned, the outer half of this tire is closer to a slick than an actual street tire.
I am also expecting these tires to be louder than the Bridgestone RE-71R's that they are replacing and I expect them to get very loud as they wear. Aside from the two main center-channels, the rest of the tread pattern is going to disappear quickly.
From a feel and fingernail test, these tires seem to play the part of an autocross tire. Once you rub through the initial surface, the compound feels quite grippy. The sidewall feels stiff and the tire bead area is very thick. I am looking forward to actually getting these mounted and on the road. For a 255 tire, it is on the thinner size compared to some of its rivals. While this might sacrifice ultimate grip due to a smaller contact patch, I'm expecting this tire to have a good, precise feel on my class-limited 9" wide wheel.
Since this tire is of an asymmetric design, it can be rotated to all 4 corners rather than just front-to-back. But that also means that the tires can't be flipped on the wheel like the RE-71R or the RT660 if and when the outer edge gets too worn. With that said, I'd probably expect premature tire life on a camber-limited car. I have 3.4* of negative camber in the front of my car and still wear the outer edge of my tires faster than the inner.
Another thing I have yet to touch on is that these tires are relatively cheap. At ~$600 for the set in 255/40-R17, they are cheaper than the Falken RT 660 by ~$40 and the Yokohama A052 by over $275!
My personal set of the V730
As I previously mentioned, there isn't much actual real-world information on V730 yet. I have found two people who have driven these and have provided some fairly in-depth feedback:
From Facebook #GRIDLIFE TRACK BATTLE- Time attack group:
"Kumho v730 feedback: tire size used is 225/40-18 which is stock size for the Corolla hatch xse.
This is my daily that I ran at a local track cross ( event similar to hillclimb)
Conditions were not ideal, it was about 38 degrees in the morning runs and 46 in the afternoon runs.
Sidewall is very stiff, even with factory camber on a heavy FWD car the fronts had no rollover with 33psi air pressure, in fact I probably could have dropped a few pounds ( but I was having oversteer so decided to leave it)
These tires are very temperature dependant, but not to the extent of a Hankook rs3/4 or BF Goodrich Rivals. They become predictable with a tread temp around 80° so that's not bad at all.
I was having some oversteer issues only because it's hard to build heat in the rears on a FWD car, tire blankets helped tremendously in the A.M. ( thanks Danny Kao for lending them!)
I dropped rear pressures to 30psi warm and that made a night and day difference. These tires like lower pressures it seems.
Breakaway characteristics appear smooth, however the Corolla has soft suspension so that might be masking that characteristic...
2 things to be aware of with these tires;
the mold release takes a while to get through and until then you will think these tires are garbage. These tires must be scuffed or it could be dangerous.
The carcass is similar to a Hoosier, it can introduce shockload to the drivetrain. The Corolla doesn't have enough power to break the tires lose but Im sure if it did wheelhop could be a concern. This isn't a drawback, just a note.
Overall grip is amazing, but I'll need to compare this tire on my xA to give an accurate review against other tires in that department.
These tires have great potential, I look forward to see how these stack up."
From Instagram Member "williamyuidk"
"Weather came through and I got to finally try the new kumho v730. It is very fast. Steering response is great, sidewall is pretty firm. More direct feeling than re71r. It does very well in the cold, but I can definitely tell its getting more sticky after couple laps. Did not feel mushy even when it got hot, although today amb. temp was barely over 40. The best part is how it behaves at the limit. Rs4, re71r or even a052 at the limit you can feel the car plowing and u feel that vibration through your steering wheel. This tire doesn’t. You can over drive it and it will have very very subtle gentle push but it will still let u make the turn. I did not hit a single cone whole day, it is so predictable and communicative. The wear is awesome, it barely touched the outer edge tread and I can 100% say this is the best tire for camber challenged cars. I can tell these tires will last 2x longer + than a052 or re71. I think I need more seat time when weather gets warmer, but kumho is definitely onto something. Was fastest rwd today. U can think of them as tires with steering feel of cup2, grip level of rt660, life/wear similar to direzza z3, and overwhelming overdrive capability."
My STX-Prepped Mazda RX-8 that I will be running the Kumho V730 on.
Here is a comparison of the Kumho V730 versus a few of it's direct competitors. Note: These comparisons are all off the same 255/40-R17 size using prices and measurements from Tirerack.com . Obviously different sizes will have different prices and measurements but this information can provide a basic outline of the data. You will see that while these are all the same sized tire, actual measurements are quite different.
Tire: Kumho Ecsta V730
Tread Width: 8.9" on 9" wheel
Starting Tread Depth: 8.5/32"
Tire: Falken Azenis RT660
Tread Width: 9.3" on 9" wheel
Starting Tread Depth: 8/32"
Tire: Yokohama Advan A052
Tread Width: 9.4" on 9" wheel
Starting Tread Depth: 7/32"
Tire: Bridgestone RE-71R
Price: $182.91 (Still in stock at TireRack at the time of this post)
Tread Width: 8.9" on 9" wheel
Starting Tread Depth: 8/32"
Tire: BF Goodrich G-Force Rival S 1.5
Tread Width: 9" on 9" wheel
Starting Tread Depth: 7.2/32"
So in conclusion, the Kuhmo Ecsta V730 seems like it has a chance at becoming a viable choice as an autocross tire. As long as it can at least match the performance of the Falken Azenis RT660, I think it will become a popular tire choice. But there are still a lot of questions out there about it. Will it be a dud and end up having issues like the V720 or will it be a fun, grippy, high performing tire like the V720-ACR? Only time will answer this as well as a tire-comparison test from Grassroots Motorsports which I'm sure will be on the way.
(March 8th Edit)
Here is a video of me doing a bit of an overview of the tire. I hope to get my car back together soon so I can do a follow-up of some actual street-time on it!