I've lost an inch and the Missus says it feels much better

T

Talksthetorque

Senior member
 Notts
No, not one for the light side...

To get the 19" CSLs nice and clean inside and out (and just out of curiosity) I swapped back to the original wheels at the weekend.
What a difference.
Soooo much less clunky and bangy ride, seems more stable over the definitely un-snooker-table-like roads near us. Less skipping about, quieter I think too.

Will anyone who's driven an MC on 18s and 19s (and the tyres/sizes quoted below) and let me know whether it's just more sidewall that's helping the situation, or something else, maybe a make of tyre that's known for being hard/crap

Was on
19" CSL REPS (definitely not original, even stamped NOT ORIGINAL EQUIPMENT on the inside of the wheel)
front 235/35/19 Michelin Sport
rear 265/30/19 Hankook Ventus V12 EVO

Now On 18" 224s OEM

front 235/40/18 Michelin Sport
rear 265/35/18 Falken 452

Cheers
ttt
 
Srhutch has just gone the other way, he's probably best qualified to comment.

I had 19s on the Alpina, and I have the standard wheels on IMmie. I always thought the Alpina tramlined a bit on the 19s unless the tyre pressures were spot on (also on Hankooks on the back)

IMmie feels much more planted but as the suspension is very different I'm not doing an apples to apples comparison, Steve would be.

Interested to hear his views after he's run the car a few days.
 
18" ride much smoother than 19" that's for sure, put mine back on at the weekend, although I'll be back on 19's soon :driving:
 
I had 19" CSLs with Michelin PS2s on mine when I bought it, but two trips (within 3 days) on my favourite Welsh roads just after I bought it made my mind up that 18's were the way forward.

Not regretted that decision since - and probably saved my life, as the 19's would throw me onto the other side of the road when hitting a bump while pressing on.

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Although the wheels and tyres are considered to be "unsprung weight", the side wall of the tyres forms part of the suspension system. Therefore, a smaller tyre sidewall on a 19" wheel effectively increases the spring rate and the Z4M already has rear suspension which is way too stiff with 18" wheels, so unless you address the suspension (springs/dampers) at the same time as fitting 19" wheels, then IMO you are only making a bad suspension system worse.
 
mmm-five said:
I had 19" CSLs with Michelin PS2s on mine when I bought it, but two trips (within 3 days) on my favourite Welsh roads just after I bought it made my mind up that 18's were the way forward.

Not regretted that decision since - and probably saved my life, as the 19's would throw me onto the other side of the road when hitting a bump while pressing on.

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Loving the pictures there mmm

Picture two would be a monthly gallery winner


Sent from my iPhone using Tapatalk - now Free
 
exdos said:
Although the wheels and tyres are considered to be "unsprung weight", the side wall of the tyres forms part of the suspension system. Therefore, a smaller tyre sidewall on a 19" wheel effectively increases the spring rate and the Z4M already has rear suspension which is way too stiff with 18" wheels, so unless you address the suspension (springs/dampers) at the same time as fitting 19" wheels, then IMO you are only making a bad suspension system worse.
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agreed. it probably didnt help that your 19" wheels were replicas and weighed more than your factory 18's.
 
I had 19' CSLs for a while and for the record I didn't notice any difference on the way up in fact I thought it may have been better but I realised my error on the way down, it was obvious the 18s were far more compliant.
 
Thanks guys for all the input. I was fairly sure it would be the wheel/tyre ratio, but just wanted to check it wasn't the wheel or tyre make that was the problem. Going to weigh wheel and tyre combos to see if the reps are sooo much heavier it would make a difference.
Permission has not been granted to buy the new CSLs on here :(
bit of an expensive punt without a bit of science experience behind it.
Expect a "which 18s" post in the wheels and tyres section soon.
 
I am on Eibachs currently and regularly swap between my road wheels which are 19" CSLs on Vreds and my track wheels which are 18" OEM wheels on PS2s. The ride is more compliant with the latter and turn in much sharper. The Vreds are also much noisier than the PS2s. However, the ride on the CSLs is absolutely fine for road use except on the worst of roads and they look much better than the stock wheels.
 
I don't have an //M but found exactly the same with my coupe - the 19" CSL reps it came with were loud, clunky, tramlined like f**k and were a really harsh ride. Since putting on 18" MV2s all of the above are solved.
 
I think the H&R suspension makes a big difference, came as a pleasant surprise as this sort of mod usually makes the ride worse. I have gone with wider 18" wheels, so can't comment on running with 19" wheels.
Cheers
 
I'm definitely sticking with my 18's for looks and ride. But I am considering moving to 265/35 & 235/40. My biggest concern was the ride would become harsh with this setup due to the drop in sidewall profile, similar to the 19" setup. But it still sounds and improvement which is good news.
 
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