Need tire size advice !
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Joined: Jan 2012
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From: Boston
Need tire size advice !
Having just repaired flat spots in all 4 rims for my C4S, and also needing new ties, what opinion is there on running slightly wider/taller tires ? I understand Porsche did extensive tire size testing on the RS and concluded that 235/40 and 295/30 were the optimal sizes for that car…
Currently running 225/40-18 and 285/30-18 (stock) and thinking about 235/45-18 and 295/35-18 on 8x18 & 10x18 rims (see photo) I think the OD on the bigger set are within spec (to each other) relative to the anti-lock brake system, so I wouldn’t expect any issues there.
I live around Boston, and the roads here are sometimes terrible. Wondering if a little ‘cush’ at the wheel is in order or if the added size will seriously upset the handling.
Any opinions on sizing ?
Currently running 225/40-18 and 285/30-18 (stock) and thinking about 235/45-18 and 295/35-18 on 8x18 & 10x18 rims (see photo) I think the OD on the bigger set are within spec (to each other) relative to the anti-lock brake system, so I wouldn’t expect any issues there.
I live around Boston, and the roads here are sometimes terrible. Wondering if a little ‘cush’ at the wheel is in order or if the added size will seriously upset the handling.
Any opinions on sizing ?
Last edited by holsen12; Mar 11, 2015 at 11:35 PM.
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Having just repaired flat spots in all 4 rims for my C4S, and also needing new ties, what opinion is there on running slightly wider/taller tires ? I understand Porsche did extensive tire size testing on the RS and concluded that 235/40 and 295/30 were the optimal sizes for that car…
Currently running 225/40-18 and 285/30-18 (stock) and thinking about 235/45-18 and 295/35-18 on 8x18 & 10x18 rims (see photo) I think the OD on the bigger set are within spec (to each other) relative to the anti-lock brake system, so I wouldn’t expect any issues there.
I live around Boston, and the roads here are sometimes terrible. Wondering if a little ‘cush’ at the wheel is in order or if the added size will seriously upset the handling.
Any opinions on sizing ?
Currently running 225/40-18 and 285/30-18 (stock) and thinking about 235/45-18 and 295/35-18 on 8x18 & 10x18 rims (see photo) I think the OD on the bigger set are within spec (to each other) relative to the anti-lock brake system, so I wouldn’t expect any issues there.
I live around Boston, and the roads here are sometimes terrible. Wondering if a little ‘cush’ at the wheel is in order or if the added size will seriously upset the handling.
Any opinions on sizing ?
closest street size in 245/35 & 285/30 x18
Drifting
Joined: Sep 2006
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From: San Diego, CA
google "tire size calculator" and have at it. Here's the one I like:
http://www.miata.net/garage/tirecalc.html
245/35-18 rub in the front a little on my C4S. Taller tires will throw off your speedo. You aren't super low, so you shouldn't have rub issues under compression unless you have no camber. I can't fit a 245/40 in the front due to having little camber up front.
http://www.miata.net/garage/tirecalc.html
245/35-18 rub in the front a little on my C4S. Taller tires will throw off your speedo. You aren't super low, so you shouldn't have rub issues under compression unless you have no camber. I can't fit a 245/40 in the front due to having little camber up front.
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google "tire size calculator" and have at it. Here's the one I like:
http://www.miata.net/garage/tirecalc.html
245/35-18 rub in the front a little on my C4S. Taller tires will throw off your speedo. You aren't super low, so you shouldn't have rub issues under compression unless you have no camber. I can't fit a 245/40 in the front due to having little camber up front.
http://www.miata.net/garage/tirecalc.html
245/35-18 rub in the front a little on my C4S. Taller tires will throw off your speedo. You aren't super low, so you shouldn't have rub issues under compression unless you have no camber. I can't fit a 245/40 in the front due to having little camber up front.
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From: Connecticut
I'm just south of you in CT and would stick with stock sizes. Just shop for the best tire characteristics that meet your needs. Tire Rack's reviews / tests are a great research resource. Very happy with the Sumitomos on my car, but probably would have gone with the Conti DW if they were in stock at the time.
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I agree, if road surface is a major concern then 17's w/ a 45 & 40(or more) series tire will be way better than 18's w 40 & 35 series(or less) tires
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Racer
Joined: Feb 2010
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From: Denver, CO
I have to agree with Robert, downsizing to 17s is the way to go.
Provided you lower the car to Euro specs, 17s look gorgeous on the 993. In my opinion, its the perfect size for the car. Also, tires are slightly cheaper and significantly more robust than larger diameters.
Provided you lower the car to Euro specs, 17s look gorgeous on the 993. In my opinion, its the perfect size for the car. Also, tires are slightly cheaper and significantly more robust than larger diameters.
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From: Canada & the Alps
Even a 205/50 x 17 will rub at full lock, and that is with Porsche approved N tire installed. At least the Michelin PS2s do.
I recall a thread from about a year ago with some members stating that 18s don't rub. Cripes, stock 17s rub.
I recall a thread from about a year ago with some members stating that 18s don't rub. Cripes, stock 17s rub.
Racer
Joined: Jun 2008
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From: South of Sweden near Copenhagen
I have to agree with Robert, downsizing to 17s is the way to go.
Provided you lower the car to Euro specs, 17s look gorgeous on the 993. In my opinion, its the perfect size for the car. Also, tires are slightly cheaper and significantly more robust than larger diameters.
Provided you lower the car to Euro specs, 17s look gorgeous on the 993. In my opinion, its the perfect size for the car. Also, tires are slightly cheaper and significantly more robust than larger diameters.
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From: Boston, MA
OP, you don;t really want 235/295 combination for several reasons. A lot will depend on the rest of your suspension and sway bars, but this will give you a fairly significant understeer. As does your current 225/286 combination.
If you chose to stay on 18" wheels, try 225/265. Maybe 235/275. Maybe 235/285, although that's stretching it a bit. In all these sizes stay with 40 ratio on the front, 35 on the rear.My own car is on 225/40 and 265/35 and it's fairly neutral. Anything more on the back and it would start to push.
PS. All of this richly irrelevant on the street. Especially around here.
If you chose to stay on 18" wheels, try 225/265. Maybe 235/275. Maybe 235/285, although that's stretching it a bit. In all these sizes stay with 40 ratio on the front, 35 on the rear.My own car is on 225/40 and 265/35 and it's fairly neutral. Anything more on the back and it would start to push.
PS. All of this richly irrelevant on the street. Especially around here.
Drifting
Joined: Nov 2008
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From: Vancouver BC, Canada
Having just repaired flat spots in all 4 rims for my C4S, and also needing new ties, what opinion is there on running slightly wider/taller tires ? I understand Porsche did extensive tire size testing on the RS and concluded that 235/40 and 295/30 were the optimal sizes for that car…
Currently running 225/40-18 and 285/30-18 (stock) and thinking about 235/45-18 and 295/35-18 on 8x18 & 10x18 rims (see photo) I think the OD on the bigger set are within spec (to each other) relative to the anti-lock brake system, so I wouldn’t expect any issues there.
I live around Boston, and the roads here are sometimes terrible. Wondering if a little ‘cush’ at the wheel is in order or if the added size will seriously upset the handling.
Any opinions on sizing ?
Currently running 225/40-18 and 285/30-18 (stock) and thinking about 235/45-18 and 295/35-18 on 8x18 & 10x18 rims (see photo) I think the OD on the bigger set are within spec (to each other) relative to the anti-lock brake system, so I wouldn’t expect any issues there.
I live around Boston, and the roads here are sometimes terrible. Wondering if a little ‘cush’ at the wheel is in order or if the added size will seriously upset the handling.
Any opinions on sizing ?
Off topic, what kind of wheels are on your car? MY02s I'm guessing, but always thought these wheels were for NB cars, wasn't sure about fitment for WBs.
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Nile13 is correct; the rims are MY'02 with spacers in the rear. 5 flat spots on 4 rims in one year... the downside of a cast rim. The 'Big Dig' here in MA means we neglected the rest of our roads and the rims have taken a beating.
My avatar pic shows Fikse FM-10's; one of the rears was claimed by a granite curb... The MY'02 are allot easier to keep clean, and do show off the drilled rotors a bit better too.
I'm reluctant to go to a 17" rim... I think the car looks awesome with the 18"s, and further mod cash is reserved for suspension changes.
The car has Bilstien HD + H&R lowering springs (lowered to a bit above RS height) and has been completely gone thru and aligned by EPE. It has a bit more camber and toe than stock. I'm considering RS front uprights and ERP links in the rear to get some adjustability back. Bump-steer is something of an issue on some the 'crowned' freeways, crossing lanes at 80mph+ (going over these 'crowns') makes the car want to steer itself. Takes a bit of getting used to. Rt 3 south is the worst offender on this score.
The understeer issue cited by nile13 is worrisome. Oversteer I can deal with, understeer is a bit scary… So wider in front without wider in back is probably a bad idea for me.
However, my thinking is that a wider tire will change the sidewall to rim geometry a bit and add some ride compliance and flat-spot reduction. I intend to do some AX, but no DE or tracking. Well, maybe some DE. But my C4S is intended as a ‘3 season’ daily driver.
I'm considering the Bridgestone S-04 or the Michelin Pilot Sport AS Plus. I have a buddy who has a 993TT with the S-04 and he recommends them, and I have the Michelins on my wife’s MBZ E-500 wagon, and for and all-season tire, they’re pretty danm good. Ideally, the tire has ‘stick’ in wet as well as dry conditions.
Keep the advice coming !
My avatar pic shows Fikse FM-10's; one of the rears was claimed by a granite curb... The MY'02 are allot easier to keep clean, and do show off the drilled rotors a bit better too.
I'm reluctant to go to a 17" rim... I think the car looks awesome with the 18"s, and further mod cash is reserved for suspension changes.
The car has Bilstien HD + H&R lowering springs (lowered to a bit above RS height) and has been completely gone thru and aligned by EPE. It has a bit more camber and toe than stock. I'm considering RS front uprights and ERP links in the rear to get some adjustability back. Bump-steer is something of an issue on some the 'crowned' freeways, crossing lanes at 80mph+ (going over these 'crowns') makes the car want to steer itself. Takes a bit of getting used to. Rt 3 south is the worst offender on this score.
The understeer issue cited by nile13 is worrisome. Oversteer I can deal with, understeer is a bit scary… So wider in front without wider in back is probably a bad idea for me.
However, my thinking is that a wider tire will change the sidewall to rim geometry a bit and add some ride compliance and flat-spot reduction. I intend to do some AX, but no DE or tracking. Well, maybe some DE. But my C4S is intended as a ‘3 season’ daily driver.
I'm considering the Bridgestone S-04 or the Michelin Pilot Sport AS Plus. I have a buddy who has a 993TT with the S-04 and he recommends them, and I have the Michelins on my wife’s MBZ E-500 wagon, and for and all-season tire, they’re pretty danm good. Ideally, the tire has ‘stick’ in wet as well as dry conditions.
Keep the advice coming !
Racer
Joined: Jun 2008
Posts: 313
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From: South of Sweden near Copenhagen
I use 5 mm (front) and 21 mm (back) as recommended here for the rims I use on the picture:
http://www.pcarworkshop.com/images/3...1998_64028.pdf
http://www.pcarworkshop.com/images/3...1998_64028.pdf