I'm thinking about replacing my 88 Formula steering wheel with Momo. My question is whether I should get a 320mm, or a 350mm. Would a 320mm make it harder to steer without power steering? Thanks for any thoughts.

w/o PS...
Smaller SW then OE will make harder to steer, more so at low speeds, backing up or parking.
Can be easier to get ripped out of your hand(s) hitting a pothole etc too.

Smaller you get the bigger problems.

350 is ~13.8
320 is ~12.6
Difference is ~1.2" diameter so could be noticeable for extra effort needed to many but others won't care.
I had 11" SW many years ago and very hard to park but Not nearly as bad as 10" or 8" SW. (Those are illegal in some places.)

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Dr. Ian Malcolm: Yeah, but your scientists were so preoccupied with whether or not they could, they didn't stop to think if they should.
(Jurassic Park)

The Ogre's Fiero Cave

[This message has been edited by theogre (edited 06-18-2018).]

320mm = 12.59 inches
350mm = 13.77 inches

Both will add considerably tougher steering effort in comparison to the stock wheel (15" I believe?)

The driving feels sportier, but you will soon tire of parking the car.

I ditched the smaller grant wheel my 87 GT came with, in favor of a freshly recovered GT factory wheel. I'll never bother with aftermarket wheels again.

Just my .02

On the opposite side of the spectrum from above......
I put a Firebird steering wheel in my Fiero. It is about 1.5" larger in diameter. When I took it for the first drive, and was backing out of the driveway it felt as if I had power steering I May be exaggerating a little bit.... but it made a BIG difference in how easy it is to turn the wheel while stopped or at very low speeds.

[This message has been edited by JohnWPB (edited 06-18-2018).]

Don't forget that a smaller steering wheel may obstruct your view of the gauges.

You can simulate this easily; perhaps tape some paper strips to the inside of your stock steering wheel.

I have a 13' Grant in mine now and the one thing I like the most is that I don't have to put that much circumference distance when crossing my hands while turning. With the stock steering wheel my shoulders were involved more, now is more of my elbows and wrists. Granted, I have to put a bit of more effort at lower speeds but at higher speeds for fast corrections and sports car feel the smaller wheel is desirable.

Thanks for all the feedback. I ended up going with Momo 350mm. I haven't installed it yet, but I'm sure I'll be happy with it.