Mazdaspeeder

Have a built EFR Miata making 330whp/310wtq with XIDA 700/400 and 15x10 ULs. Not many choices in this size and was ready to buy the Maxxis VR1 but stumbled on these a bit cheaper with a sale.

Car is not track driven but used on the street for occasional 35 mile commutes to work on winding country roads and some spirited leisure driving. I’m on a nearly 10 year old set of RS4 which are so hardened from numerous winters in a cold garage that they have bad understeer and struggle to grip even in a straight line on all but warm days

Anyone have experience with the 660? I really like the price and the look of the tire, and it did pretty well in a 200tw shootout but they tested on a heavier BMW. I’m more concerned with being able to hit tighter turns fast (autocross style) because I’m not ripping down these roads at 100mph and not hitting the sweeping turns at speed like I would on a track, my joy comes fast bursts of acceleration and going through the tighter turns with speed since it keeps me a bit more “responsible” on the street. The tire’s ability to grip without having to warm it up is more important to me than the tire’s ability to handle repeated laps consistently, similar to what you’d want from an autocross tire where you’re basically going out on “cold” rubber for each run

Thank you!

Clifton

I ran them. I have them listed for free locally too on AZsolo. Not a Miata but my car is an occasional weekend, mostly autocross (EM). Easy 400whp/380wtq, 1700 lbs, mid eng. Like you I need cold tire grip. I run a 15x9 rear. I put 9 autoX runs, maybe 200 street miles on the RT660's and went back to Rival-S. I've run Rival-S, CR-S, RT660's. Cold, the Rival-S and RT660 have more grip than CR-S. RT660's are close to Rival-S but they will cycle out sooner and were no better even new so I went back to Rivals. On AutoX starts, the CRS offered no grip. When we do an autoX on a road coarse, the CR-S took one run to get enough heat to even launch. I ran the Nankangs only one event before swapping. I got about 100 autoX runs on the Rivals with 40% still left when replaced due to age and they were still as good as new RT600's, both better than Nankangs cold. FWIW, I also data logged wheel speed (RLTC) in second gear cold roll ons to compare. If you don't need every percent of cold grip, and can use them up before they get hard the RT660's will be ok. If your car sits a lot and takes years to go through tires, the Rivals will be better over time. A052/RE71RS are better cold but the 225/50 height in 15's is a problem for most. Those two dominate in autoX.

Mazdaspeeder

Thanks for the detailed response. This is just an overbuilt street car that will see max 2000 miles a year and sit in an in-insulated garage in winter where the tires will get very cold. I don’t actually autocross but just want a tire that grips without needing to warm it up because I’m not going to do runs to warm up my tires on the street

Any idea how long one could expect the 660s to last before they get hard? I could leave the car on stands in winter and bring the tires into a basement but just don’t feel like doing all that especially since they aren’t THAT expensive

If there is a big difference in “shelf life” with the VR1 from Maxxis I’d consider that too. All my tires will harden up before I wear them out though based on what the car is used for

ehodder

You might consider the Nexen N'Fera Sport R. Grips up quickly from cold and wears better than the Super-200s (A052, RE71RS) while offering grip comparable to the RT660, V730, etc. - I think the GridLife GLTC Miata drivers were favoring them over the RT660 the last couple of years for those reasons (15 minute sprint races, lap one pace is important).

If you haven't come across Andy Hollis' tire guide here's the link: https://grassrootsmotorsports.com/ar...-buyers-guide/

A digital subscription to GRM is worth it for his tire comparisons alone.

Fireindc

iTrader: (13)

I can compare rt660's (225's) to v730's, as far as "super 200's" go.

Rt660's fell off after a few laps noticeably and didn't handle heat as well. The v730's held up to heat much better, only getting faster once they heated up. Times were very close between the two, the main difference being that I'd get my fastest laps towards the end of the session on the v730's, whereas the 660's would peak after 1-2 laps and I'd never match those times again.

The 660 is a great auto-x tire that comes on quick and can handle track abuse. The v730's are much more heat tolerant but would not be a good auto-x tire.

This year I might try the CR1's, as I much prefer a tire that doesn't overheat and still turns the fastest possible lap times.

Icedawg

I have run the Falken Azeni RT615 and the RT660 on an endurance race car, a 1985 Mazda RX7, similar weight to a Miata.
Both tires are great. The RT615 is an older version, that has better race wear and less grip than the RT660 on the race track.

If you were considering the Maxxis VR1 then I am confident you will be happy with the RT660 on a street car.

SimBa

I can't see them holding up for 10 years, but I loved my last set of 660's and have another set showing up this week.

For context, I got my first set in July 2021. 245/40/15 on a 15x9

I ran those for the remainder of that autocross season, including a Prosolo and an evo school, which are pretty hard on tires. Stored them in my parents basement for 2022.
Pulled them back out in 2023, did an open track day and I'd guess I put in over 50 laps on them there. Ran them all of last autocross season including regional events and another Prosolo. Left them on for a couple hundred street miles as well.

They were shot by the end of last season as far as autocross was concerned, but there was still a bit of tread left. I think the photo below was the worst of the 4.

Note that the outside of the tire is worn down to the sidewall. I assume this is due to my bad driving and plowing the front end.

My friends who are a more serious/competitive choose other tires for autocross, but I think the 660's are great bang for the buck.

Z_WAAAAAZ

I can confirm what Fire's said about the 660s vs v730s (ran both in 225 and am now on 660s in 245), but would like to add that the v730s seemed to wear quicker for me than the 660s. I believe the thread depth on the 730s is a little shallower than on the 660s.

I think the 660s have more peak traction, but Fire's right, the v730s just don't overheat easily on our cars. On a street tire, I guess this doesn't matter much though...

I run 660s for street and track/TT use and don't have much of a hankering to try anything else currently.

Fireindc

iTrader: (13)

I 100% agree, no question. To add to that, since the v730's basically turn into "slicks" after the first trackday, they are terrible for road use. Also due to how slick they get, it's super hard to gauge when you are going to cord them. I corded my set in competition last year and had to borrow some wheels to drive home.

Z_WAAAAAZ

That's hilarious you say that, I did the same thing last year haha. Thought I had another couple track days on a set and ended up driving home on belts. I didn't even think to check my tires because they seemed like they had plenty of tread left.

rwyatt365

I came to the 660's two years ago after some of the availability woes with the Rivals at that time. I had earlier versions of the Rivals and loved them for HPDE use (I stopped autocrossing a few years ago). Anyway, the 660's were "adequate" but not stellar and last year I relegated them to summer, street use in favor of a set of AR-1's. The 660's on 15x9's were no match for the AR-1's - at least initially. Where the 660's felt a bit vague, the AR's felt crisp. But I think the AR's faded after about 2-3 laps and started to feel a bit 660-ish. I'm not complaining because the "bang for the buck" quotient of the AR's can't be beat.

Maybe I'll try something else, or go back to the Rivals (if I can find them)...who knows?

OptionXIII

I'll just echo the other comments on the RT660 being quick to warm up but not responding well to continued full tilt lapping. Last year I did a true open track day (no sessions, just go drive) and probably got 4 hours of track time. The RT660s were completely toast after that. They gripped up fast but were clearly not meant for endurance racing.

In contrast, I drove to work today on a fresh set of RS4s for the first time at about 50* and damp roads to test them before hitting the track this weekend. I got wheelspin from a very gentle launch on a slight grade. Hopefully that was more to do with unscrubbed tires and mold release goo rather than an indication of how they will always be. The forecast at VIR is for a cold and rainy Saturday.

I wish I had the space and lack of restraint to have three sets of tires: ECS for the street, RS4 for longer runs and casual track days, and the hottest Super 200 for one lap magic and autocross.

Clifton

You may not autocross but if you are just street and need cold tire grip you want a tire autocrossers use as apposed to roadcoarse. AutoX require tires that work good dead cold. No 200tw tire will beat an A052 cold, then RE71RS then it's a toss up between 3. CR-S, Rival-S, RT660. You can download SCCA Solo National times and it shows the driver/tires/car/placeing. They all run the above or A7's if allowed.

poormxdad

I was at VIR a week ago. The rain came Tuesday late morning, and I swapped out my AR-1s during lunch for a four-year-old set of R-S4s. This happened coming out of 5b after about three slow laps.




I was actually surprised at how little lateral grip I had. It was 61 degrees. Certainly not "cold". The tires have lots of tread left, but were purchased when I was still driving the car to the track. They haven't got much use since I bought the trailer. I blame their age. I probably wasn't even doing 35 mph when she spun. I assumed they'd be better than slicks.

I've been in a number of student's cars, plus my own, and my experience with R-S4s is they're great when it's warm and dry. Pretty good warm and wet. Pretty good cold and dry. They blow donkeys when it's cold and wet, even when they're reasonably new.

Z_WAAAAAZ

MX, that was a good read. I’d give you a cat if I wasn’t on mobile right now. Sorry about your spoiler though.






While we’re on the topic of tires and RT660s and tire heat management… can anyone confirm that these craters are due to the tires blistering from overheating? I just ran two ten lap sessions at full tilt with a hefty amount of oversteer. The inner edge of both my rear tires look like this. Never had this happen before. There’s no contact in the inner fender well where the chunks in the tires are taken out. Any theories aside from extreme heat would be appreciated.

I do realize I probably just answered my own question.

rdb138

iTrader: (1)

@Z_WAAAAAZ Can't answer if those are heat blisters or not. Very odd how they are so evenly spaced and semi the same shape too. Not sure if this helps any, but I've had a couple RT660s delaminate on me due to "heat" from what I can tell. Mine looked a lot different, smoother if you will, mine separated what looks like layers. Yours looks more like chunks that got ripped out to me. Most tires I've seen with blisters (not track tires, actually re-tread truck tires, happened between the layers.) I didn't take very good pictures, but the delamination happened on the center of the tire, and the inside edge also did this odd start at delaminating with multiple lines like something was cutting at it all the way around. I was running these tires around 30lbs hot. I think I need to run a bit more air pressure in them after looking at your tires especially, because I'm wearing both edges more than evenly across on my current set. (I have purchased a pyrometer to use next track day).

I had multiple other people at the track say they had delamination issues with their 660's. Anyway, this is all to say, I don't think the RT660's have the best quality control from the factory. I'll probably try something else next time around, but not a ton of choices at 245 size.

@Mazdaspeeder This wouldn't be my first choice for a tire, but for the cost and with the very limited options that are available...you could do a lot worse.

The pictures below are after the tire had cooled down, and the rubber semi glued itself back. The center actually was more separated than I'm showing.

Mazdaspeeder

How would these compare to the Maxxis VR1 for street?

Z_WAAAAAZ

@rdb138 Thanks for the insight! I spoke to a couple buddies that work for a race shop and confirmed the cause of the damage was excessive heat. Apparently if you drive 10 laps on a very high speed track at full bore with no cooldown laps and are oversteering consistently… tires with a low heat tolerance don’t like it lol.

I’ve had two out of the ~24+ RT660’s I’ve gone through delaminate in the same fashion. Super annoying. Our Snap-On rep at work has a pair of STI’s that he races in TT and once told me they would delaminate on him anytime he ran em under 26psi cold. I’m not so sure tire pressure can be the only factor causing it though…

Anyways, sorry for the thread derailment.

Ryan5405

@rdb138 I had the exact same delamination running at Mid Ohio, 20 minute HPDE sessions. Not what I would call excessive oversteer, but some sliding around was definitely happening. I was running 32psi hot.

Z_WAAAAAZ

Bummer how regaularly they seem to delam. Everybody seems to have a story of at least one giving out.

Side note, my newest RT660s exhibit more tire squeal than any others I’ve had and they seem to be wearing slower than normal. Maybe they hardened the compound on em?