[EEZATOY]

I know this was touched on at 968.net , but thought I would throw it out here too.



I will probably be needing new tires this summer, so it would also be the time to up grade from my stock 16's to 17's. The problem is I really like the carrara 10 spokes, but they come in 7" and 9" widths - really to narrow for the front - so my thought is to run the 9" front and back with 255/40/17's.



So what does everybody think - benefits (being able to rotate tires) problems with running the same size tires on all four corners?



Thanks Sam

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[flash]

i just had this conversation at length - here's the deal:



porsche designed the 911 with too much oversteer - they corrected it by increasing the rear width - when the 968 came about, they followed the then adopted aesthetic design by doing the same thing to it - also, they wanted to design in understeer for liability and safety reasons



on a 50/50 car, there is NO reason to have mismatched wheels - both Kinesis and HRE wanted to set the car up with matched wheels until we started talking about weight balance and the changes i've made



you will be fine with matched wheels from a performance standpoint, and may even be better - from an aestheic standpoint, it's really very subjective - most people like the look of the bigger dish on the rear - i like it to be big all the way around - this is only the second car i've had to have mismatched wheels, and it is because of exactly the same thing on both of them - i'm stuck with a bigger wheel in the rear because i've lost so much weight there



you may have a problem with the offsets though - you will probably end up needing spacers in the rear if you want the wheels to be the same width - i am going to be using a 255/35/18 in the front, so this just came up in my homework too - a 255 is right at the limit of the front, depending on the particular tire, ride height, and the alignment specs

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[Harvey]

I have 255 16" tires on 7" wide rims on the front of the 968 I just bought and they just barely rub something in a tight turn. I'm not sure but it could be the rubber air scoop for the brakes. I've heard that others run this combo and don't have problems. Should I be concerned about the slight rubbing? It's pretty minor.



Harvey

=============

[quote name='flash' date='Mar 18 2005, 11:37 AM']i just had this conversation at length - here's the deal:



porsche designed the 911 with too much oversteer - they corrected it by increasing the rear width - when the 968 came about, they followed the then adopted aesthetic design by doing the same thing to it - also, they wanted to design in understeer for liability and safety reasons



on a 50/50 car, there is NO reason to have mismatched wheels - both Kinesis and HRE wanted to set the car up with matched wheels until we started talking about weight balance and the changes i've made



you will be fine with matched wheels from a performance standpoint, and may even be better - from an aestheic standpoint, it's really very subjective - most people like the look of the bigger dish on the rear - i like it to be big all the way around - this is only the second car i've had to have mismatched wheels, and it is because of exactly the same thing on both of them - i'm stuck with a bigger wheel in the rear because i've lost so much weight there



you may have a problem with the offsets though - you will probably end up needing spacers in the rear if you want the wheels to be the same width - i am going to be using a 255/35/18 in the front, so this just came up in my homework too - a 255 is right at the limit of the front, depending on the particular tire, ride height, and the alignment specs

[right][post="2035"]<{POST_SNAPBACK}>[/post][/right][/quote]

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[flash]

what profile? that is a critical factor - the outside diameter may be too big

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[Silver BLT]

Oversizing tires on wheels???

Harvey stated he had 255 x 16 on 7" rims. From the lookup tables on TireRack site the 255s should be mounted on at least 8.5" wheels. ???

Is this a "normal" practice? Will the tire companys refuse to overmount wheel size?

I would like to up (over mount?) my front wheel size by .5" 245/40/17 on a 7.5" wheel, see any problems with this idea? I'd rather not have to buy new wheels just to fit slightly wider tires on the car.

Thanks for you time , I know this has been beat to death but being a newbie...

Sorry

Silver BLT

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[flash]

that's 2 sizes up -



as long as the outside diameter is within the abs tolerance front to rear (and i think you're fine there - i think somebody said 6%, but that seems a bit high)



it really depends on the particular tire you choose, and its sidewall stiffness - if you choose a stiff sidewall, you shouldn't have any problems - if you choose a soft sidewall tire, you could get a bit wallowy in the front



whatever you do, make sure you match models front and rear

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[Silver BLT]

[quote name='flash' date='Mar 28 2005, 01:27 PM']

that's 2 sizes up -



I stand corrected, you are right! Kuhmo MX----I've got a stiffy! (sidewall)

My Racer X chip should be here today or tomorrow! <img src="/forum/images/smilies/968/biggrin.gif" class="smilie" alt="" />



Thanks again Flash,

Silver BLT

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[flash]

i'd call tire rack and see what they say about the relative stiffness of the kumho



i'm not sure what you are after in a tire, but here are some things to think about



while they are cheap, i'm not sure you will like them, since you want to go bigger - here's the problem - they are a soft tire and a big block tread design - consequently they will wear fast and make noise



you can mitigate some of this by installing a strut tower brace and then changing your alignment so as to eliminate the toe and increase the camber a bit from stock, and thereby get better tire wear



a tire that seems to be making a lot of people happy lately that is in the same price range is the yokahama AVS ES 100

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[james taylor]

I have the Yoko's on mine, 235/40x18 front and 265/35x18 rear. Really pleased with them so far. Rougher ride going from the 16's from decrease sidewall of course <img src="/forum/images/smilies/968/sad.gif" class="smilie" alt="" /> - but worth it. <img src="/forum/images/smilies/968/smile.gif" class="smilie" alt="" />

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[Harvey]

Yes, when I recently bought my 968 in Atlanta, it had 255 x 16 tires all around both 7" and 8" rims (I'm going from memory, I hope I'm right) on all four wheels. I drove the long way back to Idaho on these (3,000) miles and only lost two tires due to travel on a rocky road at one point. The tires apparently had always been on the car so they worked for long time and were really worn out. I should not have started the trip with them. But, when the front tire blew, I was in Resume Speed, Missouri and the 255 x 16 was the only tire in town available that would fit my car...so (before reading the manual) I had them put a set on (not that I had much choice). They run fine but there's some very slight rubbing against something in a tight turn....I've yet to try and ID precisely what it's rubbing against but it's minor. I now have to decide if I want to move these larger tires to the rear 8" rims and put the factory recommended smaller tires on the front 7" rims. I'm leaning towards just putting another set of the 255 same width/size tires on the rear and calling it good. I don't race the car on the track and it would be nice to rotate front to rear from time to time. If this is the wrong way to go...I'd like to hear...but the PO used the larger tires on all four wheels for a long with with no apparent problems. They were Pirelli 7000's.



Harvey

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[flash]

harvey



it is one of those things that you would notice in hard cornering - the 7000 is a mileage tire, and not a performance tire, so you're not going to get the cornering you could anyway - the combination of that and the oversize i'm sure makes for a very smooth ride, better tire life, and probably a little better gas mileage but it's nowhere near what the car could do in handling, and your speedometer is reading a bit lower than what youare really doing, and you are racking more miles on the engine that your odometer reads



as an example of the extreme of this, my jeep has 255s on it fromthe previous owner - stock is a 225 - that makes for a 6% difference in outside diamter (speedometer and odometer error) and incredible wallowing - no way would i tow with these tires - one twitch and it would be over - these are 70 profile tires - the lower profile of yours would limit that some, but the idea is the same, especially on a soft sidewall - pirelli typically had soft sidewalls on earlier tires - i don't knwo about the 7000 - call tire rack and see what they say about the construction



all of this may be fine for you - there is no real harm in any of it as long as you aren't pushing the car - it's mostly a preference thing - for safety, and optimum handling, i'd drop the fronts back down as a bare minimum - you are WAY oversize for those rims - what profiles are you running? you may have actually disengaged your abs



by the way - even if you kept the tire size, rotating would still require dismounting and remounting - the wheels aren't the same width

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[Silver BLT]

Thanks for everyones input, This has been driving me crazy (pun intended)

Flash: once again you were right <img src="/forum/images/smilies/968/sad.gif" class="smilie" alt="" /> after some checking into the Kumho MAX do have a relatively soft(er) sidewall. However, they are not in the same class of tire as the Yokos avs es100. Tire rack lists them in the category of Max performance summer and the Yokos in Ultra High performance summer, one grade down. I will probably only put 10,000 miles on the car at the most per year and it may never see a track so for me its street wear. Heck, the tire compound will harden on its own before I wear them out. (If the wifee rides in the car much) <img src="/forum/images/smilies/968/biggrin.gif" class="smilie" alt="" />

We drove on a "tour" with ~32 PCA members and had lunch with them last weekend, I spoke with the DE chairperson about tires and had good things to say about the Kumho. Granted the block design tends to become progressively louder as they wear, but so do the Yokos. My son has a set on his M3 and they aren't quiet either. Has anyone (here) ever owned the Kumho MXs or ridden in a car with them shod? Why the push towards the Yokos? Is it a case of "I like them because I have them?" I was incorrect about the sidewalls and I may live to regret the noise level they MAY produce latter in life, but by then the new stereo will be in and it won't matter. <img src="/forum/images/smilies/968/laugh.gif" class="smilie" alt="" />

Flash I'll call you for the recommended alignment settings after I change out most of the stuff on the front suspension. Brakes, rotors, springs(H&R), Koni sports, strut bar. A fun work in progress. Thanks for the help and insight.

Thanks for your help Harvey, glsd you got "her" home safe and sound.

Silver BLT

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[flash]

not really a push other than i have heard that almost everybody gripes about the eventual feathering and noise of the kumho - i almost went that route - they were my third choice - they run a bit wider in the same size, compared to many other brands, so take a close look at the specs before choosing a tire - you'll be amazed at how much they differ



given that the yoke is a bit harder tire, it should last longer - given that the pattern is less of a big block design, it should be less prone to as much noise - also, big block designs, and tires that wear easily, go out of balance easily too, so you could be spending a bit of time at the tire shop - make sure you get the free balance warranty



the kumho is great tire for the money, as far as stickiness goes - not much on longevity or quietness - the yoke is a little less sticky, but should last longer and have fewer balance issues



if you are driving strictly street, i would go with the yoke - if you are going to track the car - i would not - if it's occasional track use, the kumho is not a bad choice - if you end up tracking it more, at that point i would go to the S0-3



tire choice is very subjective - it's highly dependent on what you plan to do with the car, and what you can tolerate in noise and what wet/dry conditions you will be in - i always recommend people to choose a tire based on the 80/20 rule - what are you going to be doing 80% of the time? then, pick the tire that best suits those conditions

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[rustech]

My car came with Kumhos on the rear. What I did notice is that when they slip, THEY SLIP, and they don't like to regain traction easily. It felt as if I overheated them, melted the surface and they became very slippery.

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[Silver BLT]

Is it any wonder I don't sleep at night? <img src="/forum/images/smilies/968/blink.gif" class="smilie" alt="" /> I have lived long enough to know that it is wiser to listen to those who have more experience and have been "there" before. Yokos it is! Cheaper too <img src="/forum/images/smilies/968/smile.gif" class="smilie" alt="" /> Given the fact that I have 17" wheels but really want 18" so I can go 275/35/18 but can't find a good excuse to buy them at the prices they want.

Other than BBS which companies make quality 18" wheels?

I will have a set of 17" stock size tires for sale soon. Maybe with wheels too.

Michelin Pilot Sport A/S with 95% tread left. I bought the car with brand new tires and drove it from LA to Sactamento CA. My car will not see rain much less snow of any type where I live.

Sorry if I am being a pain in the ass about tires. I don't want to do this twice.

Thanks for help again

Ron

Silver BLT

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[bob blackwell]

Sam, back to your question of experience running the same size wheels and tires all around. I have used 8x16 wheels with 225/50x16 Michelin Pilot Sports all around with no problem other than some "tramlining" when driving on grooved pavement or over trolley lines in the road. Minor inconvenience to me compared with the ability to rotate the wheels and tires to equalize wear. There was no rubbing and no need for spacers anywhere. I am not sure about 9 inch wide wheels in the front, maybe someone else has tried them. Good luck, Bob Blackwell.

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[EEZATOY]

So bringing up a really old tread I started – still looking to move up to 17” the prefect wheels…Now I’m thinking about using one of the Boxster 17x 8.5 wheels – the Boxster III comes with a 40mm offset, with those I could/would use 245/40’s tires – this would give me an increased footprint up front of .7” (Tire Rack HTR III’s) and lose .3” in the rear compared to stock 225 & 255’s. When I use a wheel calculator and compare it to stock 16’s it looks ok to me…thoughts

TIRE / WHEEL Front Rear Front Rear
Diameter (inches) 16 16 17 17
Tire Section Width (mm) 205 225 245 245
Tire Aspect Ratio 55% 50% 40% 40%
Wheel Offset (mm) 55 52 40 40


Calculated Change
Front Rear
Tire Diameter -4.1mm Smaller Dia. -3.6mm Smaller Dia.
Inboard Clearance to Strut 5mm closer to strut -2mm further away from strut
Outboard Clearance to Fender 35mm closer to fender lip 22mm closer to fender lip

Front to Rear diameter difference of replacements 0.00%

Sam

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[bob blackwell]

Sam, go for it! When I was racing more often than I have been lately, one of the wheel combinations I tried was 8x16 all around with 245/45x16 Kuhmo tires. Worked great. Later I found that by going to 18 inch wheels I could do even better, but I didn't use the same size F&R with the 18 inch wheels. With the same size front and rear you get the advantage of rotating the wheels & tires from front to rear and rear to front and it equalizes the tire wear. Have fun and good luck, Bob Blackwell.

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[flash]

yeah - the bigger rear wheel thing is a carryover from the 911 - on a balanced car it really isn't necessary - i have often thought about it, but just can't convince myself to give up any rubber anywhere

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[EEZATOY]

Running with this thought - there are a few 17"x8.5" options - see pic's (all of which come with a coresponding stock 7" up front - so I could still maintain the 1.5" differential front to rear and gain footprint over 16" but not as much as the stock 9 & 7.5's). The 8.5's offsets seem to run from the new boxster III's @ 40mm to 50mm (the sport classics I think) - I am not a fan of the twists so thoughs are out...

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