mclarenno9

Hmmmm.....OK

I just received from Tirerack the Kumho V710's in 225/50/16 and 245/45/16. I will be using these for autox on 7 and 8 inch phone dials. Now, I had been waiting a couple months (6!) for Kumho to release the 245 size so I could have a staggered set. Mind you they had a press release back at SEMA in November of 2007 saying they would be released in January of 08.

Well I finally have them in front of me and it seems to me the 225 is wider than the 245? I know they talked about changing the tire compound and design a bit but.....!!??!?

The actual tread widths measure about the same at around 9.25". The sidewall on the older style 225 are more round than the squared shoulder of the 245. I guess maybe once mounted and loaded the contact patch of the 245 will be bigger since it is square and the 225 is more boulbous? This brings up another thing; the width, from bead to bead (outside) is 8.75" on the 225 and 8" on the 245? Basically the 225 is gonna be quite pinched on the 7" wheel while the 245 should fit just dandy.

Stacked two high, the pile of 225's is 1.5" taller than the 245 stack!?!?!? Is there any way this is possibly right? It almost seems like they marked the new 225's as 245's? All the markings on the tires confirm the size however.

You can also notice a difference inside the tire. The mold lines are like this in the 225 (old one): \\\\\\\ Whereas, in the new 245 they look like this: <<<<<<<< So, you can tell they have made changes to the tire construction.

I am not really sure what to think/do about this? Anybody?

Profile of 225 (note how round it is):


Profile of 245 (note the more squared shape):


Profile comparison...


Side by side shot...

Jim Michaels

Steve: I saw your post late last night and figured that someone would have responded before now. The tire widths appear in the photo just as you described. Your bead-to-bead measure does suggest aggressive pinching on a 7" rim. I'd be interested in TR's explanation too.

mclarenno9

I'm hoping damon @ TR can jump in here and enlighten us!

brad@tirerack.com

Uhhhhh, I have no idea.

Mclarenno9, call me or PM me with your order number. I need to run this by Kumho. Thanks.

mclarenno9

PM Sent.

brad@tirerack.com

This time last year (long before any of the new sizes became available) we learned that going forward, all new sizes of Ecsta V710 will have a distinctively more square appearance than the original sizes. This is exactly the case in this combination.

The photos look and thread indicates the tires are still unmounted. Mounted on their respective width wheels will have an impact on “stacked” height. And also important to remember that max. section width (which determines how the tires look when stacked on their sides) has very little bearing on actual tire performance (same, too, for modest differences in tread width). Once mounted they will appear to be a little more what you are used to seeing, but still may be closer to the same width than your last set.

Going forward Kumho's will be the more square sizes. Thanks for the pictures, it's nice to see these examples "in the wild"...

Jim Michaels

Damon: What about the outside bead-to-bead measure (8.75") on the 225 tire that goes on a 7" rim? That's .75" wider than the same measure on the 245 tire that goes on a 8" rim. Any problem with that?

mclarenno9

This is what gets me. I heard that, in general, the DOT slick manufacturers usually try and "circumvent" the rules a bit and make their tires just that little bit wider than the comparable size street tire, however, I find it awkward that Kumho felt the need to change the size and shape of their tire so drastically.

They list the section width of the 245 as 9.6" on 8" wheel vs 9.2" on a 7" wheel for the 225. I would believe the 225 measurement, however there is NO WAY it can be 9.6" for the 245 once mounted because the absolute maximum width I measured (before the 90 degree turn to sidewall) is, at best, 9.25". So, unless the tire stretches once mounted and inflated, it ain't gonna happen! So, I gotta pull the BS flag on that one.

I am still wondering what Kumho will say as to what their motivation was to making this change. I feel kind of stupid arguing over a couple inches anyway. The main concern for me is that I waited to buy these tires specifically because they had round shoulders and were supposed to give cars without a lot of camber good grip whilst not cording the outside edge like a Hoosier might do.

Now that they have redesigned the shoulders I am wondering if this tire's original claim is somewhat misrepresented now?

brad@tirerack.com

Don't be....this is a new design.

Have they been mounted yet? We'd really like to get a set of mounted and aired-up numbers to be able to compare. Remember, we are just starting to get the redesigned tires in, too. So this information helps us to "re-learn" the tires. Please keep me posted or call me. Thanks.

mclarenno9

I have not had them mounted yet. I wanted to make sure what I was seeing here was normal before I did that in case I needed to return them.

I do not really see anything changing here unless Kumho comes back and says something to the effect of: "Oops, we accidently marked the new 225 mold with the 245 numbers"

brad@tirerack.com

2008/09 new sizes

215/45R16
245/45R16
215/40R17
225/45R17
225/40R18
305/30R18
345/35R18
335/30R19

All new sizes feature a revised profile shape. The revised profile features a more squared-off tread and shoulder area, whereas the original sizes feature a very rounded shape. Construction and tread compound is identical to the original sizes. No “update” to the compound or construction is in the near future, from what we can tell.

The revised tire provile will be more narrow size for size than the original. This does not mean it has “less” performance, although many may think that the tire has to be larger to provide more grip. According to Kumho Motorsports, the revised profile should provide higher ultimate cornering power. It will require slightly more negative camber than the original, while target operating pressures and pressure adjustments should react similarly to the original version. It’s my belief that the new profile will have a slightly narrower sweet spot to work in, while the original was well-known for its broad tuning window. 2009 will be the first full season of availability for most of the new sizes, so time and first-hand experience will provide additional information as the season progresses.

Kumho feels that both tire profiles are mixable front and rear, but will require some tuning to achieve optimum results. This combination won the SCCA Super Stock national autocross championship on a Porsche GT3 last year, so obviously it can be used with good results.

There are no sizes where both versions are available. And as mentioned above, it’s important to remember that the sizes with the new profile do not have any sort of technical update to compound or construction.

Also of note, like many street tire products have experienced in the past, the 225/50R16 (original profile) and 245/45R16 (revised profile) will have virtually identical max. section widths when mounted on the same width wheel.

mclarenno9

Thanks for pursuing this Damon.

I will update once I get them mounted.

jorgeez

Those are really nice set of rubbers. I'm sure it's really good on the track.

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