Tyres size on alpina E30

Post Wed Mar 09, 2005 9:59 am

Lads

On saturday i am bying a set of 17" alpina alloys Replicas
to run on my 325i 2 door E30 and want to no what tyres
size i should go for also i will be wanting to lower the car to
so i will need to no how low i should go. I was thining 40mm

thanks in advance

Post Wed Mar 09, 2005 10:42 am

I have 205/40/17's on mine. I think it would be better to go for 215's, though they are more expensive, but fill the rim a lot better. 205's leave the alloy a little exposed to 'kerbs' and things...

Post Wed Mar 09, 2005 10:48 am

I changed to 215's on mine when I had them, definitely a lot better than the 205's.

Post Wed Mar 09, 2005 3:56 pm

so Its 215/40s then

Post Wed Mar 09, 2005 3:58 pm

Yeah. They ARE more expensive than 205's, but they fit the wheel so much better.

Giles.

Post Wed Mar 09, 2005 5:38 pm

Just ordered my wheels and i pick them up on saturday
4 alpinas
2 215/40 toyo proxes Ãƒ”šÃ‚£606 all in
i have 2 new 215/40s toyo in the shed saved me a few Ãƒ”šÃ‚£Ãƒ”šÃ‚£Ãƒ”šÃ‚£

Post Wed Mar 09, 2005 8:55 pm

dee watch your speedo reading with 215/40 the rolling circumfrance is diffrent i can't remember if it reads faster or slow than you really doing , 205/40x17 are same as 195/65x14. you need to pace yourself with some that has acurate speedo.i got stopped by plod speedo on 30 mph they clocked me at 37.5mph 4points and Ãƒ”šÃ‚£40 fine put it down to bad luck and a arssie plod.

Post Wed Mar 09, 2005 9:30 pm

TINSNIPS

Thanks for your tip i will keep it in mind

Post Wed Mar 09, 2005 11:06 pm

My Speedo is 7mph out with 205 45 16 according to the GPS

Andrew

Post Wed Mar 09, 2005 11:10 pm

7mph out at 30mph...? That's hell of a lot!

G.

Post Wed Mar 09, 2005 11:13 pm

I know!

I think i stick on a stock 205 55 15 BBS to see what that does.

Andrew

Post Wed Mar 09, 2005 11:23 pm

Tinsnips speedo should be reading lower not faster! As the 17 wheel is doing less revolutions at 30mph than say a 14inch wheel.
And E30's speed is clocked from the diff right?

Post Thu Mar 10, 2005 8:24 am

Yeah, so the bigger the wheel/tyre combo, the faster the car will be travelling in reality, at a set indicated speed.

Small wheels will be turning more for the same real speed, so will be actually travelling slower at the same set indicated speed...

...if you see what I mean.

Post Thu Mar 10, 2005 9:45 am

Shouldnt you be including the actual circumfrunce of the tyre though.
As its this that doing the turning and the bigger the rims the smaller the tyre wall so technicaly you should still have the same circumfrunce as with standard wheels.

Post Thu Mar 10, 2005 10:33 am

205 45 16 is almost 4 percent smaller than the stock size.

Andrew

Post Thu Mar 10, 2005 11:12 am

check tyre / speedo calculator - it will answer all your questions both in theory and practice.

paul

Post Thu Mar 10, 2005 6:17 pm

i'd rather check her out in your avitar. Is that Terri Hatcher if my eye sees true?

Post Thu Mar 10, 2005 8:35 pm

she's alicia rickter - phoebe in 'the charmed' - a friend of ours is 'charmed' mad and sat down with my missus and watched the first 4 episodes straight last week. i took a right shine to phoebe (but couldn't last the 4 - i got bored with it) and looked her up - imagine my glee when it turns out she was a playboy pet in 1995!! check her out in google - she's lush.

she kinda suits my red paint don't you think?

paul

Post Thu Mar 10, 2005 8:49 pm

how far out should my speedo read with 205/40x17, i might have to get the stealership to calibrate mine if pos. plod sed that i was over 30 and that's what the speedo was reading. but that might explain the funny obc readings i get. because they come from dash readings don't they?

Post Thu Mar 10, 2005 10:12 pm

Giles how can this be the cars are noticibly slower with bigger wheels fitted, i can tell this going from 15 to 16 and vice versa.

Post Thu Mar 10, 2005 11:32 pm

How can that be...?

With a bigger wheel/tyre combo (meaning you're rolling circumferance is a little larger) the amount of distance round the tyre is longer than a smaller wheel/tyre combo, so for the same revs of the engine, the wheel/tyre will move the car futher, which means the car will travel faster at the same revs...

Slower acceleration, but higher top speed...

Is that not right?

Post Thu Mar 10, 2005 11:35 pm

Geeman wrote:How can that be...?

With a bigger wheel/tyre combo (meaning you're rolling circumferance is a little larger) the amount of distance round the tyre is longer than a smaller wheel/tyre combo, so for the same revs of the engine, the wheel/tyre will move the car futher, which means the car will travel faster at the same revs...

Slower acceleration, but higher top speed...

Is that not right?

Sort of

but as you increase in wheel size you decrease in tyre profile. that y you shouldnt realy go more than 2inches over stock as you wont be able to get the correct rolling radius.

Post Thu Mar 10, 2005 11:55 pm

Geeman wrote:How can that be...?

Slower acceleration, but higher top speed...

Is that not right?

Slower because it takes more effort to move the bigger wheel

I think we are thinking the same thing in different words and confusing ourselves, well me

Post Fri Mar 11, 2005 1:11 am

i wouldn't think a bigger wheel would give you a higher top speed, at 130+ drag is the main factor. however, 215/40/17 is the correct tyre size. because:

195/65/14: 609mm diameter
205/40/17: 597mm diameter
215/40/17: 606mm diameter

it's the diameter you want to cocen trate on if you care about accurate speedo's. if you care about acceleration, reduce your unsprung weight (i.e. weight of the wheels and tyres).