Serious discussion - reverting to 18inch for 335i

[Ahbengdriver]

Just dynoed my 335i at Boss Motorsport. Power was a little lower than I expected but still pretty decent. 380bhp and 520nm.

However, altho I am running one of the lightest 19inch rim in town with PS2, I still dont get the handling feel that came with the stock car when it was on 18inch heavy stock rims with RFT. I also dont get the instantaneous 'jerk' and acceleration G-force feel unless I use 1st gear to launch the car, which drives like a farking baboon in heat. Some say because my PS2 are wider than stock tyres by 1cm all round, some say PS2 side walls too soft vs RFT.

Tyres should be due for change in few months. Revert back to 18? Yay or Nay?

 

[kenntona]

Re: Serious discussion - reverting to 18inch for 335i

What's the combined weight of your 19" RS + PS2 vs 18" stock + RFT?

 

[Slater]

Re: Serious discussion - reverting to 18inch for 335i

Just dynoed my 335i at Boss Motorsport. Power was a little lower than I expected but still pretty decent. 380bhp and 520nm.

However, altho I am running one of the lightest 19inch rim in town with PS2, I still dont get the handling feel that came with the stock car when it was on 18inch heavy stock rims with RFT. I also dont get the instantaneous 'jerk' and acceleration G-force feel unless I use 1st gear to launch the car, which drives like a farking baboon in heat. Some say because my PS2 are wider than stock tyres by 1cm all round, some say PS2 side walls too soft vs RFT.

Tyres should be due for change in few months. Revert back to 18? Yay or Nay?

beng, i know exactly what u mean. when i switched from OEM's to 19" non RFT, the razor sharp feel of the car was gone, even when using PS2's. I truly think itsthe hardness of the side walls that gives the car that planted secure feel. Also, alot of ppl focus on the weight of the tyres and rims. though this has a profound impact on acceleration, the fact that the tyres r wider also contrubute to inertia, which is equally important in the accelaration of the car.

nonetheless given the amount of power ur 335 packs, it does not look like u r short of power and shld be able to handle the 19". unless ur dead keen on reviving the feel u had when on 18". also, aesthetically ur 18" will not look good on ur ride (not sure if u mod), given bmw OEM rims conservative offsets

my 0.02

 

[acupunch]

Re: Serious discussion - reverting to 18inch for 335i

its time for you to consider E92///M3.

if PS2 side wall are soft. you can change to NEEZ wheel. it give the non-RFT tires an option to put in a rubber tube to pump air onto the sidewall so you can pump the side wall as hard as you want and not over inflate the tires pressure. that's why NEEZ wheel got two tube inlet.

 

[kenntona]

Re: Serious discussion - reverting to 18inch for 335i

It's a qualitative feel at this point. What about lateral grip feel around corners? Wider tyres felt worse?

 

[totoseow]

Re: Serious discussion - reverting to 18inch for 335i

abd can i ask u what feel are u looking for? u dun say enuf on that. the smaller rim will get u a more comfy ride. if u tell me rft gives u better feel i say u talkcock. pls say a bit more about ur definition of feel.

 

[Slater]

Re: Serious discussion - reverting to 18inch for 335i

wider tyres on a level playing field (non RFT) will definitely feel better and more planted round corners. but in this case adding RFT into the equation will mean that even if its an 18" could still feel sharper in handling.

 

[totoseow]

Re: Serious discussion - reverting to 18inch for 335i

how can RFT give u sharp handling? u want sharp feel u need to feel more road than tyres. a softer compound gives u better feel and better grip at the expense of higher wear. wider tires dun give u more feel. it gives u more lateral grip. but it also retards ur acceleration.

so it depends on what abd is looking at. define ur feel dude.

 

[1.5bar]

Re: Serious discussion - reverting to 18inch for 335i

how can RFT give u sharp handling? u want sharp feel u need to feel more road than tyres. a softer compound gives u better feel and better grip at the expense of higher wear. wider tires dun give u more feel. it gives u more lateral grip. but it also retards ur acceleration.

so it depends on what abd is looking at. define ur feel dude.

2nd the above...

 

[Slater]

Re: Serious discussion - reverting to 18inch for 335i

how can RFT give u sharp handling? u want sharp feel u need to feel more road than tyres. a softer compound gives u better feel and better grip at the expense of higher wear. wider tires dun give u more feel. it gives u more lateral grip. but it also retards ur acceleration.

so it depends on what abd is looking at. define ur feel dude.

agreed that softer compound and wider tyres give u better grip on account of greater surface area. nevertheless the rigidity of RFT tyre walls as compard to regular tyre walls does minimize the amount of flex on the tyre wall, giving it a sharper less wobbly feel.

 

[Deadkookaburra]

Re: Serious discussion - reverting to 18inch for 335i

ah beng downgrading to 18 cos you scare that malaysia TP eye on your mod again?

 

[totoseow]

Re: Serious discussion - reverting to 18inch for 335i

agreed that softer compound and wider tyres give u better grip on account of greater surface area. nevertheless the rigidity of RFT tyre walls as compard to regular tyre walls does minimize the amount of flex on the tyre wall, giving it a sharper less wobbly feel.

thats the first time i hear. the only thing RFT gives u is stiffer walls so that nails cant rip a hole fast. that rigidity of RFT is not sharpness....its harshness. the ness is correct.

 

[acupunch]

Re: Serious discussion - reverting to 18inch for 335i

correct me if I'm wrong.

when inflate the tires on front 33psi rear 35psi, its very comfy but less grip on corners. however, when front is 35psi and rear 37psi, i feel the throttle respond is sharper than more grip during acceleration and high speed corner.

therefore its higher tire pressure = hardness of RFT side-wall?

I'm not saying its equivalent, I mean something close.

 

[totoseow]

Re: Serious discussion - reverting to 18inch for 335i

the harder u pump the lesser the contact patch. of cos u go faster. u also stop longer distance. if u lessn the pressure u hv more contact patch....slower acceleration. but u shud hv more grip.

 

[Shaun]

Re: Serious discussion - reverting to 18inch for 335i

Causes of significant differences between parties here :

1) no testing run to record objective quantities
2) subjective qualities casually described (very possible faulty perception and communication)
3) different cars, setups (esp. alignment and inflation pressure), but most of all different drivers (therefore driving styles)

The driver factor in point 3 alone, can result in one saying X pressure is good, whilst another calls it underinflated.

===

We must acknowledge that tires are the top 2 most complex components on any performance car, owing to the fact that they are a complicated composite of non linear polymers and monomers over a synthetic woven carcass, subject to internal pneumatic as well as internal and external thermal/chemical effects.

So tire designers are able to vary the vertical, lateral and longitudinal stiffness, fairly independently of the other two. It is very possible to have a taller but stiffer sidewall RFT that builds lateral force quicker. It is almost always a compromise though, with weight taking a hit followed by vert. and long. stiffness which affects tire grip. Why there is perception other than expected on these likely tradeoffs is mentioned in point 2 of the list. Another variable is the contact patch area change due to inflation pressure - it can get pretty low depending on construction, especially at crazy low aspect ratios.

 

[Slater]

Re: Serious discussion - reverting to 18inch for 335i

thats the first time i hear. the only thing RFT gives u is stiffer walls so that nails cant rip a hole fast. that rigidity of RFT is not sharpness....its harshness. the ness is correct.

harshness is a given, i experience it 1st hand. but the go cart type handling is sorely missed, this is confirmed not just by myself. placebo effect possibly

 

[TripleM]

Re: Serious discussion - reverting to 18inch for 335i

ABD.....
Keep the 19 wheels, and try Potenza RE11. Heavier than PS2 by 2lbs per corner tho but still lighter than the RFT.
I am sure you wil be greeted wif a pleasant surprise. 235/265 combo is all u need.

Tires are indeed complex things in terms of design and construction.

Flexes in tires ard cornering can sometimes raise your goosebumps. PS2 rubber is the best example. I hv used this rubber in 3 different cars wif proper inflation and good allignment set ups and all gave me that sensational flex and that is simply becoz the sidewall is indeed quite soft. I still like the tires...good overall performance for street and decent tread life. Price is another factor to consider.

IMO, PS2 tires work better if inflated a bit more pressure OR install them on slightly wider rims. The latter stretches the tires sidewall n has the effect of stiffening it without neccesitating the need to increase more pressure than required.
It doesnt look that pretty but it's more of a function over form.

 

[Ahbengdriver]

Re: Serious discussion - reverting to 18inch for 335i

how can RFT give u sharp handling? u want sharp feel u need to feel more road than tyres. a softer compound gives u better feel and better grip at the expense of higher wear. wider tires dun give u more feel. it gives u more lateral grip. but it also retards ur acceleration.

so it depends on what abd is looking at. define ur feel dude.

I think yr are right. I dont drive around a corner like Michael Shoemaker, so actually u could say the wider tyres are not really important to me. Afterall I also dont track. The only times I make full use of the stupid overpriced 335i is when I take it to Genting or further North.

I am also very anal over comfort, to the extent that I lower my tyres pressures on Sg roads. However as you said, the wider tyres and lower pressure >> more contact patch on the road but also retards the acceleration. Last time when I was still on 18 RFTs(225/255), and I had the procede-2 ECU tune(about same power as juicebox), My car can literally fly on DS mode. No $hit, I raced a Carrera 4-S on Mandai Road and overtook the burger at the bend. Even on stock power, before the ECU was chipped the car really had the punch. I was reading the tyre spec on the B-pillar. Their reccommended BMW spec for 19 inch is 225/255, not 235/265 as many of us use. I am no car expert, just that my hands, feet and butt tells me although my car has an additional 80 bhp, it doesnt feel like it has that much when on the road. Its almost like being back to stock, the 19s cancelled the 80 bhp.

Twice on NSH I raced 2 cars on separate occasions (a Nissan 350Z and a Merc CLK 280). both run 17 inch or 18 inch stock rims. I can see from their rear that their tyres are narrower, so less contact patch. I must say with only my wife with me, I had a bit of difficulty keeping pace with them.

Having said these, I agree sidewall stiffness makes a diff. I drove Andre's car running GY Asym with stiff sidewalls, the steering response is better but still I dont get the way the car drives compared to stock tyres/rims. On this note I must say BMW engineers must have dont lotsa testing/research...kudos to them!

 

[kenntona]

Re: Serious discussion - reverting to 18inch for 335i

Its almost like being back to stock, the 19s cancelled the 80 bhp.

Wahahahahaha, all the theory of lighter wheels + tyres go to waste......

One, overall weight wise, your Advan RS + tyres should be lighter than stock wheel + RFT.

Two, rotational inertia should not be worse off. PS2 is lighter than your RFT. Your Advan RS does not have a barrel/lip like your HRE. So there is no increase in outer mass on the circumference.

Three, did rotational diameter increase? Example, rear wheels. Stock was (18"x25.4) + 2[255x0.35] = 635.7 mm. On your 19"s, it is (19"x25.4) + 2[265x0.3] = 641.6 mm. Difference = 5.9 mm. So yes, the diameter increased, but 80 horse negated by this 5.9 mm? Hahahaha.......

Boh li yiu lah, Beng........

 

[TripleM]

Re: Serious discussion - reverting to 18inch for 335i

Twice on NSH I raced 2 cars on separate occasions (a Nissan 350Z and a Merc CLK 280). both run 17 inch or 18 inch stock rims. I can see from their rear that their tyres are narrower, so less contact patch. I must say with only my wife with me, I had a bit of difficulty keeping pace with them.

their stock set ups arent the factor here of why u cudnt keep up..
it's more than just tires and on NSHW, balls dictate more. Those cars hv big displacements too, dont forget.