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Old 08-24-2018, 03:41 PM
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LucT
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Talking Help needed with rear tire choice

Hello all,


I'm new to rennlist and I was hoping if you guys could help me out.


I bought my first Porsche (996 carrera 4 convertible MY2000) like a month ago and immediately decided that I wanted to install 19' rims on the car.

The rims I ultimately chose were the BBS CH-R 8.5x19 with 51 offset at the front and 11x19 56 offset at the rear. I bought the rims second hand with 235/35R19 tires at the front and 265/35R19 tires at the rear.


Currently I'm thinking of buying new rear tires because the 265 tires are stretched and I'm not a real fan of that to be honest. So I'm thinking of installing 295/30, but I am a little afraid that my tires will then scrub. At this point I have to mention the fact that my fenders are rolled already, meaning that there is some additional space. As I don't know anyone wo is willing to lend me their 295/30 tires to test whether they'll scrub, I'm asking you guys if you think its possible to fit such tires (or perhaps even wider tires) on my car. Below you can find some images of the car and the rear tires, any advice on tire choice will be much appreciated!


Kind regards,








Old 08-24-2018, 03:49 PM
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charlieaf92
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I can't speak to widths because my rear is wider. But, with a C4 you need to also pay attention to the circumferences. I believe Porsche say they need to be within 3% to avoid damage to your AWD system. Some have said that if you can't get an exact match, its better to error on the side of having the rear circumference smaller than the front.

Oh, and congrats on the purchase and welcome to the site!!!
Old 08-24-2018, 03:57 PM
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soverystout
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19 inch wheels changes things. The 996 suspension setup was never meant for 19s. Yes,yes, they fit but that doesn't mean it's optimal. With that said, 295/30/18s fit fine on an 11x18 wheel with a 63 offset on a 996.2 (2002 -2005). The 11x18 with a 63 offset wheel on the 996.1 requires a slight roll of the fenders.

You might want to go with 285/30/19 to have a better chance of the setup fitting without rubbing.
Old 08-24-2018, 04:03 PM
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Dharn55
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The rear wheels you bought are the wrong offset for the rea, they are meant for a wide body car.They are out 9mm farther than they should be which leads to some challenges.
Old 08-25-2018, 12:25 AM
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808Bill
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I hope you have tight fillings and good roads...Good luck and congrats on the new toy!
I like/want more sidewall.
Old 08-25-2018, 01:04 AM
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Ratchet1025
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I am not sure where you live, but if it is near Michigan let me know. I have 295's that you can try to fit.
Old 08-25-2018, 08:01 AM
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LucT
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Hi guys,

First of all, thank you for all the replies! I really appreciate it.

@charlieaf92: So you're saying that I have to be within 3% of the circumference of the OE wheels on the front and on the rear, correct?

https://www.wheel-size.com/calc/?whe...cl=30mm&sr=0mm
According to this calculator my circumference on the rear is increased with 2.6% when I install a 295/30, which is just within spec..

On a sidenote, maybe a 305/25 will be a better choice overall because this will allow for a more accurate reading of the speedometer in combination with a 235/35 front tire.
However, I doubt whether I'll have enough fender clearance to install a 305/25 on the rear...

@soverystout: I guess 285/30 tires will fit, I think I'll look around for some stores nearby that do have such wide tires in stock and who are willing to help me out.

@dharn55: I knew the original offset was 65 for the 18' tires, but the configurator on the website of BBS showed that I could fit these rims on my car. However, I'm starting to believe that this rim is more suitable for a C4S than for a C4..

@808Bill: Luckily the roads here are really smooth, so that shouldn't be an issue at all!

@Ratchet1025: Thanks for the offer, but sadly I live in The Netherlands haha.
Old 08-25-2018, 08:21 AM
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strathconaman
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You also need to have the rear tire diameter just slightly smaller than the front.

In your case:

235/35R19 = 792 Revolutions per mile
275/30R19 = 791 Revolutions per mile
Old 08-30-2018, 02:05 PM
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DeanClevername
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Aside from technical reasons as listed above, from a handling standpoint the one thing these cars don't need it a wider than stock rear tire. Understeer is already present at stock widths and will only get worse unless you increase the front tire width as well (not easy to do from what I understand). Also from my own experience, dropping 19in wheels for lightweight 18" immediately and noticeably improved every aspect of driving the car. 19s + the larger tires add a lot of mass that the suspension has to work against. Unsprung mass is always detrimental
Old 08-30-2018, 02:13 PM
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e90steve
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I run 19x11 et50 no problem at all with a 315/25/19 tire. Mine is an 04 so rolled from the factory. I've never once rubbed and I'm lowered 25mm on RUF springs/Bilstein shocks.

295/30 should work OK but 315/25 is a closer match to stock rolling radius. Mine is RWD so not sure how the stagger is dealt with on AWD/C4/C4S models.

Last edited by e90steve; 08-30-2018 at 03:06 PM.
Old 08-31-2018, 08:27 PM
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Debo18D
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I have Hankook Ventus EVOII's on my 2001 C4 Cab in 235/35/R19 front and 295/30/R19 Rear. It has Bilstein B8's and HR Sport Springs. Fenders have not been rolled on it. On the track (COTA) it doesn't rub, on the roads it doesn't rub, but if I load the suspension on the road with myself and another big passenger by hauling *** over a big dip then it will chirp but have seen no tire or car damage and I am not worrying about it too much. It happens about twice a year. I concur with the above posters that having the correct wheel offset is paramount.

Debo sends.



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