Switching from Run-Flats to Non Run-Flats – Bounciness Issue

L

lyosea

Member
Hi everyone,

I wanted to get your input on something I’ve noticed since switching from run-flat tires to non run-flats.

I recently replaced all four tires with Uniroyal Rainsport 5s, based on the garage owner’s recommendation for a good balance of price and performance. One immediate improvement is that potholes feel far less harsh — much more comfortable overall.

However, there’s something that doesn’t feel quite right. When driving on relatively smooth London roads, especially at low speeds (0–20 mph), the car has a noticeable and constant bouncing sensation. I can’t recall if this was an issue with the run-flats, but it definitely feels more pronounced now.

Could this be due to the softer sidewalls of the non run-flats? Would adjusting tire pressure — possibly increasing it — help reduce the bounce?

I’d really appreciate hearing your experiences or any advice on this. Thanks!
 
Increasing pressures could help, what are you running at the moment? But yes could be more bounce of the sidewalls.
 
32-34 34-36 is the max pressures ..28-30 real minimums

Could be that the shagged suspension comes into play..
 
You will probably find you need to reduce the tyre pressures, the garage will have set them to the same recommended pressure for run flats as stated on the car but none run flats need less pressure, a bit like a cheep plastic foot ball, the more pressure the higher it bounces, try the pressures recommended by B21.
 
Brillomaster, B21, and Chippie — thanks for your input. It’s been helpful
I’ll take a look at my pressures and change them.
Will update you on the results. Stay tuned!
 
Once you leave the smooth streets of London tain, and can drive about 10 mph, you will feel the benefits of removing the RF's.
I noticed it immediately, the didn't feel like it was trying to kill me when I changed lanes and went over the white line.
 
I once owned a mk3 Cortina. That was proper bouncy…. 😉😬

A bit of ‘give’ is, IMO, better than paying for new dental work. Embrace the smooooth

And your alloys will thank you! Less risk of expensive, and potential terminal, cracks

Let us know how the RainSports go… was thinking of a set for the CLS when due in place of Pirelli P-Zero
 
lyosea said:
I recently replaced all four tires with Uniroyal Rainsport 5s ...
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On which E89, with how much power and, apart from London streets, where else do you drive it and how 'sportily'?

'Driving Miss Daisy' needs relatively low pressures, 335bhp in Sport+ (with the changes to suspension & power delivery that entails - not least 500Nm of torque for 8 seconds) needs higher.
 
Jennifer, 100% I had to pay some dental work already - cracks in the alloy that could not be repaired and when I had to replace the rear alloy it made sense to just move to non run flats. One alloy alone is spenny, one new alloy can nearly equals 4 new (non runflat) tires.

BusterBoo, its a 28i - 245 horsepower, atm just london streets, sometimes I go out but very rarely ATM unfortunatly.
 
Best keep away from Devon roads, we have long potholes that run down the centre of the road and others in the carriageway :headbang:
 
lyosea said:
BusterBoo, its a 28i - 245 horsepower, atm just london streets, sometimes I go out but very rarely ATM unfortunatly.
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Good to read a realistic reply. (My use of higher pressures than you need is genuine, too. Yesterday, I drove 3+ hours on fast dual carriageways.
(Very sorry to read your previous reply about the alloys. Shameful, really, that this should ever happen.)
 
B21 and Chippie, when I checked mine, it was 35 PSI at the front and 42 PSI at the rear. Just to confirm — based on your advice (and BusterBoo’s input too) — is the general consensus to try running around 32–34 PSI at the front and 34–36 PSI at the rear?

I’ve also been experimenting with the drive modes, and so far, Sport+ feels the best in terms of handling and overall feel.

Side note: I got a lift home last night in a friend’s Porsche 911 Turbo, and wow — that thing was next level in terms of stiffness. You could feel every pothole and bump on London roads! Naturally, I asked if he was on run-flats or not — he had no idea 😅. I guess some people enjoy that punishing ride.

@BusterBoo – I wasn’t too bothered about replacing the alloy, to be honest. Those run-flats are just so harsh. And with the design of the alloys — as stunning as they are — they don’t have very thick or frequent spokes, so damage was probably inevitable (speed bump onslaught).
That said, the car is such a nice standard of car for the price.
 
lyosea said:
B21 and Chippie, when I checked mine, it was 35 PSI at the front and 42 PSI at the rear. Just to confirm — based on your advice (and BusterBoo’s input too) — is the general consensus to try running around 32–34 PSI at the front and 34–36 PSI at the rear?
Click to expand...

Try
32 psi front
34 psi rear
 
Hi, sorry for the delayed reply — a recent update to the website made it difficult to spot notifications.

For anyone curious about the tires: overall, they’ve been great. They definitely smooth out the ride, although the handling feels slightly less poised. Reducing the tire pressure has helped noticeably with the low-speed bouncing sensation, and I’ve driven the car multiple times since making that adjustment without this issue being experienced.

That said, there’s a trade-off. In London, with so many speed bumps, the softer tires may/seem to increase the risk of slightly scraping the underside of the front bumper. If you’re driving mostly in city centres, it might be worth increasing the pressure slightly to avoid that. But if you’re outside of urban areas, the recommended lower pressure works really well.
 
I forgot to add another benefit is the car does make lens creak like sounds (less stress transferred into the cabin)
That said, I did spend some time tracking down the causes of various creaks, and thought I’d share them in case it helps others:
  • Seat rollover head cover: This one was obvious once spotted. If you or a passenger push the seat back and it rests against the cover, it creaks like crazy while driving.
  • Wind deflector: I couldn’t find a solution for this apart from removing it entirely. If anyone has found a better fix, I’d love to hear it.
  • Front speaker dash cover: This one took a bit to diagnose the source but was obvious once found. The internal cushioning on mine had disintegrated — easy to spot once you open it up (which is simple to do). I found that placing some Blu Tack worked well as a fix
 
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