Tire Upsize
#1
Rennlist Member
Thread Starter
Tire Upsize
I found this thread:
https://rennlist.com/forums/997-turb...-question.html
and this quote:
I agree with @cstyles and I’d like to know if anyone has successfully run a
FRONT: 255/35/19
REAR: 325/30/19
combination tire. My new 19x9 & 19x12 wheels are arriving and I’d like to try get the tire sizes right the first time. I like the idea of the 255/325 combo being as close to the factory tire specs as possible to protect the front diff.
The sidewall height between the front and rear are also a nice balance with this combo, as I prefer the meaty tire look and the factory 235/305 just looks too low profile for me.
235/305 Ratios
245/325 Ratios
255/325 Ratios
https://rennlist.com/forums/997-turb...-question.html
and this quote:
Also been running 245/325 19" combo on 8.5"/12" BBS wheels for a couple seasons now. Not a single issue with fitment, clearance or front diff. Changed the front differential oil earlier this season (original 10 year old fill) and the oil came out golden and clear - almost like new.
Be sure that the offset on the wheels are low enough that the wheel and tire are pushed out to be flush with with fender - see my avatar. This will ensure you have lots of clearance on the inside.
And FYI considering it's related to this topic - technically the 245/325 combo is not the same front/rear rolling diameter as the stock 235/305 setup. It's close, and the general consensus is that it's within whatever tolerance Porsche may or may not have allowed from the factory to account for winter tires, worn tires, etc... The technical match to the OEM F/R ratio is 255/325 but 255 doesn't fit nicely under the front of a 997.1TT. However, those of you with a 997.2TT, they fit just fine as the fender liner is slightly different in the .2 allowing for some extra space.
Someone should be the guinea pig and buy new or used front .2 liners and see if they fit in the .1 wheel well. Then .1's could run the proper 255 front tire. I don't recall anyone trying this out yet.
Cheers
Be sure that the offset on the wheels are low enough that the wheel and tire are pushed out to be flush with with fender - see my avatar. This will ensure you have lots of clearance on the inside.
And FYI considering it's related to this topic - technically the 245/325 combo is not the same front/rear rolling diameter as the stock 235/305 setup. It's close, and the general consensus is that it's within whatever tolerance Porsche may or may not have allowed from the factory to account for winter tires, worn tires, etc... The technical match to the OEM F/R ratio is 255/325 but 255 doesn't fit nicely under the front of a 997.1TT. However, those of you with a 997.2TT, they fit just fine as the fender liner is slightly different in the .2 allowing for some extra space.
Someone should be the guinea pig and buy new or used front .2 liners and see if they fit in the .1 wheel well. Then .1's could run the proper 255 front tire. I don't recall anyone trying this out yet.
Cheers
FRONT: 255/35/19
REAR: 325/30/19
combination tire. My new 19x9 & 19x12 wheels are arriving and I’d like to try get the tire sizes right the first time. I like the idea of the 255/325 combo being as close to the factory tire specs as possible to protect the front diff.
The sidewall height between the front and rear are also a nice balance with this combo, as I prefer the meaty tire look and the factory 235/305 just looks too low profile for me.
235/305 Ratios
245/325 Ratios
255/325 Ratios
Last edited by NSXavier; 11-03-2021 at 08:56 AM.
#2
I solved this issue by custom ordering wheels with lower offsets, yet OEM width.
The OEM tire sizing looks proper. I took zero drivetrain risks and I kept the wheel and tire weight (rotational mass) down.
Doesn’t help you, I know.
The OEM tire sizing looks proper. I took zero drivetrain risks and I kept the wheel and tire weight (rotational mass) down.
Doesn’t help you, I know.
The following 4 users liked this post by JF22:
#5
Rennlist Member
Thread Starter
I dunno… I feel like the sidewall could be fatter. And utilizing a 9” and 12” wheel on stock tire sizes would also stretch them out a bit further giving it the “stretched tire” look.
#6
Rennlist Member
Have to agree that the taller sidewall looks much better. I have oem tire sizes on custom offset wheels, and if doing it again would go with a 9” and 12” wheel. Looks much more aggressive.
#7
Just to clarify, I am suggesting OEM or even less, physical wheel width yet utilizing OEM tires specs.
Compensate with offset for flush look, leverage offset for meaty tire stance. Retain OEM tire specs to preserve the drivetrain.
That’s my point.
Compensate with offset for flush look, leverage offset for meaty tire stance. Retain OEM tire specs to preserve the drivetrain.
That’s my point.
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The following 6 users liked this post by arscottp:
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#12
Rennlist Member
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#14
Rennlist Member
Also, shameless plug, this setup will be for sale in a month or so. Got a set of LMs coming.
Shoot me a PM for more info
Shoot me a PM for more info
Last edited by arscottp; 11-03-2021 at 02:28 PM.
The following users liked this post:
NSXavier (11-03-2021)
#15
Rennlist Member
Actual sizes of tires that are the same size will vary by manufacturer and model of tire. To determine the actual sizes of a tire, I suggest utilizing a site like www.tiresize.com to see what the actual measurements of the specific brand and model tires you are interested in are.
If you are the type that is concerned about how the tires will look on the wheels (for example, same amount of stretch front and rear) or are very concerned about keeping the rolling diameter differences as close to stock as possible, this site is really helpful.
For example, here are all manufacturers that current make a 255/35/19:
https://tiresize.com/tiresizes/255-35R19.htm
And here's a chart with all the sizes that Pilot Super Sports are available in:
https://tiresize.com/tires/Michelin/...uper-Sport.htm
If you are the type that is concerned about how the tires will look on the wheels (for example, same amount of stretch front and rear) or are very concerned about keeping the rolling diameter differences as close to stock as possible, this site is really helpful.
For example, here are all manufacturers that current make a 255/35/19:
https://tiresize.com/tiresizes/255-35R19.htm
And here's a chart with all the sizes that Pilot Super Sports are available in:
https://tiresize.com/tires/Michelin/...uper-Sport.htm