sirmoog

Hi,
I'm looking to run all-season tires on my base 2015 981. The fronts are 235-40-r19, and the rears are 265-40-r19. I'm looking to go down 10mm each on width. My install said this is doable, just to make sure it won't cause any issues with ABS or other warning lights.
Just looking to get confirmation from this group that we should be good in this regard. Thanks!

andy7777

So long as the ratio diameter between the front and back remains the same, the Porsche brains that actually run your car while you're not looking will be OK with it. If I recall correctly, if you change your diameter ratios something like 5% you might/will get limp mode failure.

10mm variance shouldn't make any difference either in the wheel install or whacking out the system. I went up 10mm in both directions with a 981 with no problems (245/275).

sirmoog

Thank you for that. Yes, just moving from 235 to 225 for the fronts, and from 265 to 255 for the rears. May I ask, why did you decide to go 10mm bigger in the past?

andy7777

Because I had slightly wider rear wheels that needed a 275 tire size, so I did the same calculation as you're thinking about and added 10mm to the front too to avoid getting the ECM messed up.

Those of us who track the cars often go wider too, so long as the ratio's kept in mind it all works out. Where you get a problem is usually by making the rear wheels/tires too wide and forget that they become taller if you keep the same profile. There is a tire size calculator out there that lets you calculate all the diameters, so you can go wider so long as you lower the profile, keeping the ratio of the tires (front/back) the same.

PorscheAddict

^Yep, well summarized. 225/255 for winter would be fine. If you're making this move for winter and sticking to wider summers in summer go for real winter tires though rather than A/S.

sirmoog

Thanks! Is about a 1.1% decrease for front and rear, so hopefully this won't mess up any of the computer magic. Front/rear ratio is 96.7% with original set up, and 96.67% with new (desired) set up. So, much less than a 5% change!
I'm sticking with the all-seasons year-round, mostly because I don't drive hard, and want something that won't be a death sentence if I get a bit of unexpected snow while at work.

Pep!RRRR

sirmoog

No, I'd stick with the same aspect ratio, and just decrease the width by 10mm front and rear. This keeps the diameters as close as possible. If I move to 45 aspect, the change on overall diameter is more significant.

sghokie

FWIW, I found some all seasons to put on mine for the winter and I was able to find 265 40 19 and 235 40 19 in the same brand and model.
Search for Atlas Force UHP tires.
For the price, I am not expecting a miracle.
I got the fronts on so far, I am waiting for the backs to make it in.
I waited on ordering the backs until I got the fronts. So far I think they are decent.
I don't really drive like a badass so I think these will be fine for me.

PorscheAddict

a 1% change won't affect anything F/R. Not driving hard won't help when you can't brake though. Some A/S are pretty kick *** in the snow, Conti DWS06 for one. Not sure if they make 98X sizes.

sghokie

I have had Conti DWS before on other cars, they are excellent tires if you can get them in the size you need.
I haven't seen them in 235 265 40 19

sirmoog

I'm going with the General G-max AS-05. Nice review on Tirerack, reasonable trade off in terms of dry performance, wet performance, and light snow.

sghokie

Did you look for the Atlas Force UHP?

sirmoog

I did, just didn't get enough info on them to make me confident in my purchase.

sirmoog

Tires will go on Friday, I'll report back and let everyone know how they turn out!