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997 Road Noise - Smaller Wheels?


24 Nov 2020

My 997 C2S with 19" rims is really noisy for general road use. It definitely sounds like road noise, not wind or engine; it's rather muting the exhaust and we have to shout to make ourselves heard in the cabin when travelling at 70mph (your honour). I was wondering about switching for a set of 18s to reduce the noise (and the tyre bill!)

Does that sound reasonable or am I way off base and there are other things I should look at first?

Current wheels are 235/35/19 F and 295/30/19 R.

I've got my eye on a set of Carrera 3 18s. Is there anything else I need to be aware of - e.g. spacers?

Obvs I need different tyres for speedo and to absorb the vibration. Maths suggests ~10mm deeper; 225/45/18s for the front are fine but 285/40/18s are rare (the ones I've got my eye on currently wear 285/30/18). What would be a better size to go for?

Sorry for the noob questions, I've never changed wheels before! This bit is all new. Many thanks in advance :)

hjs911 said:
Does that sound reasonable or am I way off base and there are other things I should look at first?

Old tires can cause this too, I had a set of 7-year-old Michelin pilot sport 2 "N rated" tires on mine which were pretty noisy, I replaced them with Michelin PS4's, made a world of difference :thumb:
They are noisy cars. I wouldn't expect a big improvement with 18s.
Wheel size wont alter the tyre noise, you need different tyres or you have a another issue.
They do suffer a lot of tyre roar from the rear arches.

Try sound deadening material inside the rear quarter interior panels. Dynamat or similar.

Cheaper than new wheels, but you may prefer the handling on 18's though.

Rolling diameter between 18's & 19's is unlikely to change as the sidewall profile will be larger on smaller wheels.
I have 18s on my 997 and I still have a lot of road noise, especially from the rear arches. Whether it's a noticeable difference from 19s, I can't say, but it's not quiet
Thanks for the replies, everyone. I was hoping the extra rubber in the tyres would absorb the sound but maybe it's just something we'll have to learn to live with!

Dyanmat sounds interesting - hadn't seen that. Thanks for the pointer James, I'll do some more research :)
I agree that older tyres can be noisier as they tend to harden with age. Might be worth considering a new set of boots!

Or, fit as loud exhaust :)
Have you had your alignment checked recently?

My Cayman was making a real "roar" from the rear (something I had put down to the polybushes and rose joints) and it turned out to be excessive toe in on the rear tyes (the result of an incompetent "tuner" who got nearly every aspect of the geo wrong).

After a trip to CG it not only handles better but it is also far quieter (as in a 90% reduction in the roar)
its the 295s am afraid and coupled with the fact they are sports tyres so they are not designed for economy or low rolling resistance so lower noise.

when you buy tyres you can see the rolling NBA . try running semi slicks like the Cups. they are even worse!!

just put your foot down or get a louder exhaust ;-)
A different tyre can make a difference. Most internet tyre companies offer a dB (decibel) rating and there can be as much as 5-6 dB between brands of the same tyre size.
I've found Pirelli's to be noisy, whereas Michelin's & Bridgestone's on my car are definitely quieter.

A 911 is however a Sports Car and not a well insulated luxobarge so tyre & road noise will always be more prominent.


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