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Tyre sizes and departing from OEM spec

@Sue Pertwee-Tyr

I went from 18s to 19s and the ride was significantly worse on an old BMW.

All I did was switch from 19" Michelin tyres to Uniroyal rainsport 3 as they are renowned for being a soft compound. The ride was as good as the 18s.

Worth a thought have a softer compound
 
Yes, I switched from Michelin to Continental when I changed sizes. The Contis were great, but expensive and when they wore I changed to Avon and the Avons do also seem to ride a little more softly. Haven't noticed any real drop off in performance, wet grip, cornering and braking are still pretty much as they were, and the Avons are also a bit quieter which is a big plus.
 
Interesting as my car runs on 19’s and it’s really comfy. 245/40/19 on the front and 275/35/19 on the rears. BMW E61 535D MSport Touring. Fairly soft compounds I believe - Toyo Proxes Sporr.
 
Is there any country in the world with race track smooth roads where these ultra low profile tyres are actually usable?
 
Most speedos are slightly optimistic. My wife's Suzuki Swift Sport has OEM 195/45R17 tyres, which is quite an uncommon size. Our fitting 205/45R17 improved speedo accuracy and ride comfort. The extra 10mm of width did not make the wheel appear over-tyred either.

It's a bit trickier changing sizes with the staggered 19" wheels on my BMW. Thankfully, since moving away from run-flats, I have little to complaint about the comfort of 225/40 and 255/35 Michelins.
 
davidsrsb said:
Is there any country in the world with race track smooth roads where these ultra low profile tyres are actually usable?
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Yes. Switzerland. the surfaces are generally super smooth and never any potholes.

One one of our cars we have gangster 255/40 R22 wheels and the ride is really good (air suspension though).
 
What was the problem with good old 15"? Was there ever a customer base out on the roads protesting in yellow jackets, 'We want bigger wheels now!!!' ?

Come to think of it, 15" was a bit oddly big when I was young.
 
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RJohan said:
What was the problem with good old 15"? Was there ever a customer base out on the roads protesting in yellow jackets, 'We want bigger wheels now!!!' ?

Come to think of it, 15" was a bit oddly big when I was young.
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My first car (a Mini) has 10" wheels!
 
RJohan said:
What was the problem with good old 15"? Was there ever a customer base out on the roads protesting in yellow jackets, 'We want bigger wheels now!!!' ?

Come to think of it, 15" was a bit oddly big when I was young.
Click to expand...

Purely a fashion thing. I suspect in years to come with the transition to EVs, wheels will start to get smaller again as smaller wheels are more efficient hence longer range.
 
NeilR said:
Purely a fashion thing. I suspect in years to come with the transition to EVs, wheels will start to get smaller again as smaller wheels are more efficient hence longer range.
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Maybe or maybe not. The Tesla Model 3 standard fitments range from 235/45 x 18" to 235/35 x 20".

And lets face it - most EV's are ugly enough even before sticking little tiny wheels on. The do present additional difficulties for tyres though - the extra weight being one.
 
Heavier cars need bigger brake discs and calipers. Thankfully alloy wheels big enough to clear them are cheaper than they were in the 80s.
 
I'm always arguing that any modern road car with properly maintained brakes (new fluid, properly bleeded, pads not worn) can do a full emergency brake from top speed at least once where it is the grip from the tires that is the limiting factor, not the brakes. Do a track day and not all will survive, though, but how many SUV's with 22" and overly large Brembo's does that?

911's always been renowned for excellent all day long brakes, even when they had (good looking (preferably Fuchs)) 15" wheels.
 
RJohan said:
What was the problem with good old 15"? Was there ever a customer base out on the roads protesting in yellow jackets, 'We want bigger wheels now!!!' ?

Come to think of it, 15" was a bit oddly big when I was young.
Click to expand...
The smallest wheels that will accommodate the brake rotors on my car are 18". Puny rotors inside oversized wheels look far more naff.
 
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