66427-450

I went tire shopping today, I live just a few miles from the Tire Rack (and Corvette Central by the way). Yuck!, the sidewalls on the current tires are so zoomie, I couldn't find a high performance 215/70, or /65, tire (& I looked at them all) that I would feel comfortable mounting on my KO's, although the Pirelli P4000's seemed to provide the the performance I need, at least on paper. THEN I came across the Coker / Michelin XWX repo's on the Net... Wow, they are EXACTLY what I am looking for..... looks correct for a 60's car, and if they are like the originals, are true high performance (and high speed) tires. Some of you may recall I had a front tire come apart at a pretty high speed this spring, that resulted in ~ $6000 of body damage.

Anyway, does anyone have any experience with these XWX repos? or has anyone heard anything about them? I need a tire that will take 145-150MPH, and look period correct.

Thanks - Mike


[Modified by 66427-450, 7:51 PM 9/8/2002]

Bluestripe67

Check with the guys running at Bonneville, I'm sure they could recommend a high speed tire. :D :D :D :D

Jimbo64

Mike, I'm confused. You mention Coker made Michelins. I thought Coker was a tire Mfg in Chattanooga, tn and Mich's
mfg'd by Michelin. Have to go back and read your post. One more cold one first. J
:cheers: :cheers:

BAD-L88

I have them on my Daytona. the car was originally equipped with them. No complaints.

As I understand it Coker bought the pattern, they don't even say Ckoer on them anywhere.

Viet Nam Vett

Just went out and searched the site( Do a "search the site") and they are sold and marked as Michelin XWX. But the bummer is No white walls..... :nonod:

Ih2lose

I have purchased a set of tires not from coocker but somebody else advertized in the useall mags.If nesacary I will fingd the invoice.They are p21565r15 was told at purchase they are a mitchellin no brand clone called daytona.the side wall was ground off and a yellow line was vulcanised on
this is a tire I was scarred to drive at high speed with for the longest time but I now am comfotable with them because its in the back of my mind about the grinding.Looks great but I would definatley be nervous above 120 with them.they had a winter sale on them and I purchased them delivered for less then 400.00 I rember at the time cooker did not have the radial size I wanted in a yellow stripe.I took a set of mitchellins off and they do in fact have the excact tread pattern.

SWCDuke

The XWX is made by an outside contractor to Michelin and they are sold in both the US and Europe. In the US Coker is has exclusive distribution rights for Michelin "vintage tires".

I discussed the XWX at some length with the Coker people at SEMA last year. They assured my that they are made in the original molds with the EXACT same materials and processes as the originals from 30 years ago.

The carry the old unbounded V-rating, which is "over 130 MPH" and should easily handle the Corvettes low weight relative to the tires' load capacity to well over 150 MPH.

The only other tire I recommend in this size is the W-rated Pirelli P4000 Super Touring or the V-rated Michelin Energy MXV4. Both of these are positioned as high speed rated all-season touring tires. I would imagine the the XWX has higher limit handling and better limit handling characteristics than the former two because it was originally designed for very high powered sports cars such as the Ferrari Daytona.

The Coker reps told me that the 215/70VR-15 and 225/70VR-15 are not selling well and may not be reordered when existing stocks are exhausted, so buy a set and support the cause. The 185/70VR-15 is selling well to vintage 911 enthusiasts.

I never cease to be amazed at the number of vintage Corvette owners who install cheap low or non-speed rated tires on their cars, so you would be well advised to spring the thousand bucks or so that the XWXs cost. I don't think you can do better for any price.

The minimum recommended wheel width for 215/70s is 5.5", but I would install them on at least 6" wide wheels such as KOs or the '67 Rally Wheels. They should fit within the body on either of these two wheels except when the steering wheel is well off center and the suspension compresses in jounce, so be careful turning into driveways.

The 215/70R-15 size matches the revs/per mile of the 7.75-15 OEM bias play tires - 775 - so they won't have any impact on speedometer and odometer accuracy.

Duke

396 RAT

Wow! Just checked the "XWX" tire.
$260.00 each!
Glad they make the MXV4, great tire
at about 1/2 the price!
But, they dont look like 60's tires.
So, it probably wont help you too much.

JohnZ

XWX's are outstanding performance tires - I had them on my 330GTC, 275GTB/4, and 365GTS/4 (OEM tires); they will wear a bit more than typical touring tires, but that's really not an issue with the usage our classics get. Yes, they're expensive, but you can't buy a better 15" limit-handling tire these days.

stngry63

I'm running 215/70 MXV4 on a 7.5" rim. In low speed autocross, I have to run 44 lbs./in2 air pressure front and 42 lbs. rear to keep the tires from rolling off of the tread. I usually run 35/32 lbs of pressure for daily driving and fun and the tires do well. In a recent issue of Road&Track, they quoted Pirelli as saying that you can't go wrong with 32lbs. Does anyone know the maximum pressure that is safe for 70 series tires for occaisional spirited backroad driving? Also, I can't believe that there aren't more performance tires being bought in 15" 70 series. There are still a lot of Sharks and muscle cars out there. A campaign needs to be started.

SWCDuke

The maximum cold pressure is placarded on the sidewall and it's usually 35 psi for P-metric tires, but usually 44 psi for P-metrics that are rated "V" and above. Operating pressures can increase as much as 10 -12 psi over the cold inflation pressure in severe service such as race track hot lapping or sustained triple digit speeds. When I drove a Saleen Mustang in the Silver State Classic Challenge back in '89 I started with 42 psi and the hot pressure after 25 minutes at 150-160 MPH was 55. In this case I ran higher than optimal pressure for grip in order to keep the tires from overheating and disintegrating from sustained high speed, which is the biggest hazard in open road racing.

Running mid forties psi for autocross is not a problem. Back in the mid-sixties when I was running 6.70-15 Michelin X radials on the SWC I ran cold pressures as high as 45 front and 50 rear to keep the sidewalls from rolling over too much in spirited driving. Back then there were no maximum pressure ratings placarded on the tire sidewall.

For normal driving on 70 series radials, 32 psi is probably the best pressure to give a good blend of ride and handling with a bit of bias toward handling. For the best ride, pressures as low as 24 psi are probably okay for low and medium speed driving.

Autocross typically requires high cold pressure because the courses aren't long enough to heat up the tire and increase the pressure. For spirited back road driving 36 psi would be a good starting point and when you measure hot pressure after a hard run in warm weather it will probably be in the range of 40-42.

For race track hot lapping I try to determine the best hot pressure and then measure it when the tires cool to ambient, so I know where to set my cold pressures prior to an event. It's typical for summer high performance or DOT legal racing radials to work best with hot pressure in the mid-forties and then they lose about 8-12 psi when they cool to room temperature. Optimal pressures usually change with track temperature conditions, so you're chasing a moving target, but it's possible to understand the trends.

The sad fact is that most vintage car owners think that a "performance tire" is one that is wide and has white letters. Nothing could be further from the truth! The performance potential of a tire has nothing to do with how wide it is or other visual charactersitics except for the tread pattern design. The performance potential of a tire is hidden in its casing construction and rubber compounds, but speed ratings and UTQG ratings give a strong indicator of how a tire will perform. The performance of a tire is indicated by it's speed rating (at least H for a high performance tire), it's wear rating (the lower the better), it's UTQG ratings (at least A A), and it's tread design (preferably very large blocks with a low void ratio and no siping).

For the Shark crowd in addition to the 225/70VR-15 XWX there are three available "police pursuit tires" in this size that are positioned as "all-season performance" tires, one each from Goodyear, Firestone, and General, and they are all V-rated.

Unfortunately there are no longer any summer high performance or DOT legal racing tires in 15 inch sizes. The best you can do is high speed-rated all season performance or touring tires.

Duke

66427-450

Duke, et all;

have you ever heard of/seen, anyone sucessfully running a 225/60-15 on a 6" KO (on a stock mid year)?

looks like there are several HP tires in this size, and the makers show 6" as the min. wheel width


[Modified by 66427-450, 7:49 PM 9/8/2002]

SWCDuke

You can mount 225/60s on six inch wheels and the assemblies should fit the car without interference, but a six inch wheel is really too narrow for a 225/60. A seven would be about minimum for this size to work properly. They will look very pinched, and the narrow wheel will cause uneven load distribution across the tread - too much in the center and not enough at the shoulders - which will degrade handling characteristics. As profiles are reduced, proper wheel width becomes more critical. A 215/70 will probably perform better, especailly an XWX. They are still damed near racing tires.

You need to understand that 90 percent of a car's handling potential is determined by available tire grip and other tire operating characteristics such as slip angle versus lateral force generation, and tires must be mounted on suitably wide wheels for them to perform properly. Springs, anti-roll bars, and shocks, in and off themselves won't improve handling. They are just there to isolate the occupants from the worst road input frequencies and exploit the tire's operating chacteristics within the limitation of the car's suspension kinematics. I really comes down to whether you define "performance" by your car's actual handling characteristics, or how wide the tires look while the car is parked.

I learned the importance of having sufficient wheel width when I mounted a set of 205HR-15 Pirelli Cinturato CN 72s on my SWC in '68 when the 6.70-15 Michelin Xs worn out. The Pirelli was a new "low profile" tire of the era and Pirelli literature admonished that they need to be mounted on sufficiently wide wheels.

I was disappointed with their performance (and the way they looked) on the OEM 5.5" steel wheels, so I bit the bullet and bought a set of the new 7" Rally wheels over the counter and remounted the tires. The additional width and negative offset of the 7" Rally wheels forced me to trim the fender lips and bonding strip at the front, but it was like I installed a set of racing tires. The steering was suddenly back to being very linear up to near the limit as with the steel belted Michelins, but the fabric belted Cinturatos had more grip with much more predictable breakaway characteristics at the limit. I was extremely pleased and impressed with what they did for my Corvette's handling.

I once came up behind a late sixties 911 circa '71 while southbound on Highway 1 south of Big Sur. I kept pushing him and he picked up the pace, but I finally got by on a short chute and pulled away. Further south toward San Simeon where the road opened up enough for me to use the full might of my Special High Performance engine he disappeared from my rear view mirror field of view. ;)

I now run 225/70VR-15s on the sevens, but don't recommend it because you have to trim the fender lips. I would not do it today, but being as how I did the deed 34 years ago, I'm not restoring them back to original.

Duke





[Modified by SWCDuke, 4:30 PM 9/8/2002]

66427-450

just to update those of you that still may be following this thread;

The next production run for the 215/70 XWX is at the end of the year, so if your interested place your order with Coker and wait (and they will work with you on the price...a bit anyway). BUT, i was doing additional research and found that Goodyear is still making the old/vintage Blue Streaks!!! Remember those, in sizes like 7.00-15, 8.00-15, etc. well, you can still get them (based on what i found on the web, i'll call them tomorrow), AND you can get them in 3 or 4 different compounds. talk about correct....

SWCDuke

The vintage Blue Streaks are for vintage racing. You can check them out at any vintage race. They two-ply bias ply tires - will probably work okay for limited street use, but probably have very short life and will ride rough and follow every groove in the road.

The biggest you can install without fender modifications is 5.50-15; the 6.00-15s need at least a seven inch wheel and won't clearnthe fenders without modification.

Duke

JohnZ

They also have a VERY thin carcass construction under the tread area and are highly susceptible to punctures, even from tiny bits of gravel; I considered them for my Grand Sport, but on the advice of several guys who race on them, I passed on the Blue Streaks and went with a conventional construction current radial (no clearance problems on a Grand Sport).