Kumho V730: Autocross Review
AkursedX last edited by AkursedX
Now that I have completed my first autocross weekend of the season, I am ready to expand upon my thoughts on the Kumho V730 200-treadwear tire. If you have not read it previously, I did a full overview about this tire in my initial post:
I am not going to review all that info here but rather I am going to discuss my thoughts on what its like to actually drive on and autocross this tire.
** The TL:DR of this is if you have driven on BFG Rivals for autocross, these are quite similar to them as far as grip, wear, and temperature range while providing better steering feel at a much better price. **
Disclaimer: I am not in any way affiliated with any organization or business related to tires. These opinions are my own and are the opinions of a rather enthusiastic, but incredibly average autocrosser. The numbers I will share in this post were pulled from my smartphone which runs Race Chrono Pro. It uses a Garmin Glo GPS and the internal accelerometer of my phone to measure G-forces. I drive a Mazda RX-8 which is a pretty heavily-prepped STX-classed car. I have 3.25 degrees of camber in the front and 2.25 in the rear
This is what I do my testing in.
I put about 150 miles on the V730 before my first event. No way around it, they are LOUD. I would say they are louder than the worn Bridgestone RE-71R's that they replaced. On smooth asphalt, they are tolerable, but when you get onto grooved concrete or rough, patchy asphalt, the noise gets pretty bad. I'd attribute it to the very stiff sidewall and aggressive tread design, but I don't know enough about tire construction and harmonics to be sure of the exact reason. I don't know if this would be something that I would recommend to someone who planned on using the tire for heavy street/daily driving use.
I also had the opportunity to drive through some heavy rain. While their grip on wet surfaces was better than I expected, their aquaplaning resistance wasn't impressive. I put them through some heavy puddles and even though they were brand-new, they got incredibly 'floaty'.
The suicide doors of the RX-8 makes it much easier to load my autocross wheels.
This weekend I was fortunate enough to participate in the Finger Lakes Region SCCA Test and Tune on Saturday and their first event of the season on Sunday. The event was held at the Seneca Army Depot in Romulus NY and is a massive WW2-era airfield. Our weather on Saturday was brilliantly sunny and 60-65* temps. Sunday took a turn for the worse with weather that varied from the high 40's to low 50's with bouts of rain. This varience was good in that it taught me a lot about the tire.
This image shows how far off I was from using all the available tread area. I really needed to push harder and needed better temps.
First topic I will touch upon is tire pressure. I got the best performance out of these tires at lower pressures. My last two runs of the test and tune were done back-to-back with the first at 30psi and then 24psi. At this point in time, the tires had good heat in them. Nearly every input had a higher g-force reading at the lower pressure and I was was able to attain lateral grip readings that I would get on fresh RE71's. But even at the low pressure, I wasn't able to load the edge of the tread (To the little triangle on the sidewall). In retrospect, I think these tires would enjoy being 'overdriven' more than what I did with them.
Next topic is tire temperature. On Saturday when it was 60*+ and sunny, the tires were grippy and up to a good operating temperature by the end of the first run. That grip got better as the tire temp went up and I never felt like they were nearing overheating even after a back-to back 4th and 5th run at the end of the day.
On Sunday, the day started off around 50* and a bit damp from morning rain. My first run of the day on cold tires was manageable but with noticably less grip. And with long breaks between runs I was not able to keep any heat in the tires. My peak g-force levels were all lower than where they were on Saturday and my times relative to a number of the other cars that were at the test and tune suffered as well.
My best raw-time of Sunday was a re-run after what I thought was my last run. The run prior, rain had started to fall and I was losing grip on the surface resulting in a run that was about 2.5 seconds off my best. Fortunately they called me for a re-run do to a late red-flag. While I didn't think I'd improve my time, I figured I'd take the extra seat time. Now that I actually had some heat in the tires, they woke right up and I had my best raw-time of the day (hit a cone unfortunately) by almost half a second even though the surface was damp from rain. I achieved my best lateral-g numbers of the day on that run as well.
Post-event shows nothing unusual wear-wise. The outside is on the left here and you can see how shallow the treads are compared to the water channels.
Not much to say here. After 16 runs, I have seen no odd wear patterns nor did they take any significant amount of tread out of them from this weekend. I feel they will certainly last longer than a Yokohama A052 and don't appear like they will suffer from the delamination issues that the Kumho V720 did.
After this first weekend, I don't have a definitive answer as to whether these are a legitimate tire for autocross. If you also HPDE and do Time-trials, I think these are worth a serious look as they are quite grippy when warm and appear to handle heat well. But until they get a bit of heat in them, grip suffers relative to other autocross tires.
In a lot of ways, this tire is incredibly similar to the BF-Goodrich Rival in that it takes some temperature to get grip, wears well, and can be overdriven. I think heavier cars and FWD/AWD camber-limited cars would like this tire as those types of cars are better at really pushing the outer edge of the tire and getting heat into it. But in honesty, I don't think these are optimal tires for my RX-8 and my driving style. The Yokohama A052 is the tire to have in my class and the Falken RT660 and Bridgestone RE71 are close behind. When it gets warmer, I think the V730 can be there but only time will tell.
This photo shows the tire loaded. While it looks like a lot of sidewall flex, it actually is a lot less compared to the RE71's. (I'll have to find a comparison photo.)
As the season goes on, I will update and report on any additional findings/information that I have on the Kumho V730.
Chariotoflove last edited by
Man, seeing your baby makes me nostalgic for mine.
I've had Kumhos on my Kias, obviously not autocross, but rather the Optimo. They're okay for OEM, but it's funny how you say yours are loud and have some trouble gripping in water. I've noticed similar traits in my obviously not performance driving. Once I switched the Sedona to Generals, it got quieter, and my K900 doesn't like to corner in rain on the Optimos. Maybe there are some traits that track across an entire brand!
t0ast last edited by
@akursedx Always interesting to hear about the new 200TW offerings, so thanks for sharing. I can't say I'm too surprised at something with such a chonky outer edge behaving similarly to BFG Rivals, but better communication is always a plus. Seems like they'd be worth considering if I ever get around to throwing some 200TW tires on the STI.
@t0ast An STI would probably be a car that would do well with this tire. I've autocrossed a stock suspension '16 STI and understand the handling dynamics of it fairly well. The limited camber and classic Subaru understeer would be good at getting heat into it and manage to get more use out of the outer half of the tire than what I did.
Kumho is supposed to be coming out in larger, wider sizes. I wish I had some kind of connection with them because I just bought a set of Falken RT660's and wheels for my '21 Veloster N that I am setting up for D-Street autocross. That is another car that probably could have used this tire well. That said, I'm excited to see how the Falkens work too! I'm way too much of a tire nerd.
way2blu last edited by
@akursedx if they can make some 19” or 20” sizes (D-street compatible sizes for a 1LE Camaro) these will probably be my next competition set. My Camaro maxes our around -1.8° of camber and the V730s sound like an ideal solution.
Thank you so much for this writeup btw, I’ve bookmarked this for when I have time to tire-shop this summer.
@way2blu I could have sworn that I saw an announcement months ago showing that they were going tooffer it in a number of sizes including 19and 20" but I can't seem to find it anymore (In my defense, I could have been looking at another tire as I constantly pore through tire offerings). Biggest right now on Kumho'swebsite is a 245/40-18. Meh. But for your car, the Goodyear Eagle Supercar 3 seems to provide great performance and gives good wear.
davesaddiction last edited by
@akursedx Looks like I don't have right to view the first four images.
@davesaddiction Thanks for the heads up. I think I added them to the post a 'different' way as the code for them seemed a lot longer. I think I know how to fix it now.
davesaddiction last edited by
No problem - I can see them now.