16" Rim to 17/18" Rim

[Spaceman]

Thinking of upgrading to bigger rims when i pick up my E90. But i'm really concern over the trade-off between bigger rims for slower speed and fuel consumption...how slow can it be if the E90 is fitted with 18" rims ? slower by 10-20kmh? slower response?any input very much welcome...thanks a million!

 

[Lionel_Koh]

Originally posted by Spaceman@May 5 2005, 08:44 AM
Thinking of upgrading to bigger rims when i pick up my E90. But i'm really concern over the trade-off between bigger rims for slower speed and fuel consumption...how slow can it be if the E90 is fitted with 18" rims ? slower by 10-20kmh? slower response?
any input very much welcome...thanks a million!

Of couse bigger rim will increase the FC n reduce the top end.......but it hv better look... E90......Yummmy...... :yes:

 

[bimmerman]

My underpowered E34 M50B20 was on 225/55/16 and for some reason felt more sluggish than it should be. After going for 225/45/17 the car became lighter and more responsive to throttle input. Really strange and defies conventional wisdom. Maybe the new rims are lighter? But the lesson i've learnt is that upsizing your rims may not always have a negative impact on performance.

 

[WAFS328]

Off course the 225/45 R17 felt more powerful because the overall diameter is smaller than your 225/55R16.

225/55 R16 - OD 653.9mm
225/45 R17 - OD 634.3mm

By changing to bigger rim, it doesn't mean bigger. you must take consideration of the tyre size as well.

Therefore if you want to change tyres, make sure the OD is 3% within your original size tyre.

Here's another comparison,
205/55 R16 - OD 631.9 mm (STD tyre size for E90 320 & E46 318)
225/35 R18 - OD 614.70 mm
235/35 R18 - OD 621.7 mm
245/35 R18 - OD 628.7 mm

Just make your choice...

 

[bimmerman]

So with 225/45/17 i'm back to the manufacturer intended 195/65/15 original diameter again. Which means i'm on 0% OD right?

 

[WAFS328]

That's right.

 

[Lionel_Koh]

Originally posted by bimmerman@May 5 2005, 07:32 PM
My underpowered E34 M50B20 was on 225/55/16 and for some reason felt more sluggish than it should be. After going for 225/45/17 the car became lighter and more responsive to throttle input. Really strange and defies conventional wisdom. Maybe the new rims are lighter? But the lesson i've learnt is that upsizing your rims may not always have a negative impact on performance.

I'm doubt wit the statement cos i change my original 15' rim to 17' wit 225/45 but the FC increase n the steering felt heavy as welllll. Yaaap i do agreed that tyres size will make a diff but i do beliave bigger rim wit bigger tyres sure will increace the FC instead of reduce it.........Just my opiniion

 

[bimmerman]

Many factors come into play my friend. I did not upgrade from 15" to 17" like you did. Mine was 16" to 17" so:

1. Your 15" rims are definately lighter than your replica 17" therefore this could be a factor for your case.

2. As for rolling circumfrance, it's probably not a factor in your case.

As for my case:

1. My 16" on 225/55/16 had a greater rolling circumfrance than my 225/45/17. Therefore after upgrading, I realised better fuel economy.

2. If I went back to 15" I could realise even better fuel economy since my 15 and 17 are of the same circumfrance and the 15" is lighter.

So, your case is weight related and mine is circumfrance related.

 

[wang]

hi all si fu,

since my car is 15" and i had changed to 17".And i felt underpower and lose my top end.Caused mine is 318i.Do any si fu know actually for 318i is suitable for 16" or 17".

 

[Juan Powerblow]

I have heard that performance dips with bigger rims but my personal experiences feel that it's really marginal. Even when I upgraded my ex-E36 318's stock 15" to 17" with 235 in the rear, the difference wasn't all that apparent. But E46F always gibe excuse that he got 18" so he kenot drag with me! I think the benefit of having better handling (and looks) outweigh the marginal dip in speed.

 

[AnGeLiCdEmOn108]

sometimes if you change rims and tyres, you may loose but sometimes you may gain. it all depends on the size, the weight of the rims, what type of tyres you are using.

basic advice, you want looks, go for it. if loose power because it, mod the engine. if increase petrol consumption, cari one sugar mummy...

win-win situation