How much slower????

[DanJones]

I have currently got 15s on mine and and thinkin of goin to 17s or preferably 18s......how much slower will the acceleration be????

cheers
DAN

[E30BeemerLad]

Don't know dan so sorry i'm not really helping, but I thought if you got the profile correct on the bigger rims, the rolling circumfrence of the tyre should be the same, so not really affecting speedo reading or acceleration. But there again, I may be talking complete bollocks

[StuBeeDoo]

I've just done a quick calculation and if you go for 215/40x17 tyres the difference in rolling radius will be negligable.
HTH
Stuart.

[dazleeds]

i think beemerlad is right exactly what he said

think you have to measure the original wheels and tyres and go from theyre Daz

[E30BeemerLad]

i think beemerlad is right exactly what he said

think you have to measure the original wheels and tyres and go from theyre Daz

Phew! - mine runs on 205/40/17 and I think the speedo is pretty accurate

[DanJones]

cheers guys.....well im on 195/50/15 at the moment....seen some 18s (225-40-18) but i think thats a fair bit bigger. They would look amazing tho....My 15s just dont fill the arches enough!!!

[dazleeds]

mines on 205x45x16s
feels ok maybe a touch harsh on some bumps but trackin and balancin are a mile out so ill leave judgement till thats sorted Daz

[E30BeemerLad]

Dan - you will need rear arches rolling for proper clearance on 17's and above

[DanJones]

Aint really gonna bother with 16s cos not a great deal of difference to the 15s....The only good things with 15s is the cheap tyres...

[dazleeds]

i got the 16s cos i knew theyd go on without rolling the lips etc also got 15s bbs as spares Daz

[Davenotouring]

I don't think it will be much slower, it's to do with the weight of the wheel also though.

17's went on my touring no problems.

[Zayyan]

I thought this was a thread complaining "how much slower can my 3-speed 316 be?"

[320Touring]

I thought this was a thread complaining "how much slower can my 3-speed 316 be?"

answer: nearly as slow a zayyan's Citroen

[Zayyan]

It's not slow you know!

Except when it's broken down of course

[320Touring]

It's not slow you know!

Except when it's broken down of course

has sommat happened?! msn?!

[Zayyan]

It's not broken down yet, but it is French, I'm expecting it!

Used to have to make sure I had my wallet and mobile when I left, now it's wallet, mobile and AA card

[320Touring]

It's not broken down yet, but it is French, I'm expecting it!

Used to have to make sure I had my wallet and mobile when I left, now it's wallet, mobile and AA card

AA?have you not just turned 18?

[Zayyan]

Should've known that was coming!

[TOURINGDADDY]

I got 17's on mine with 225/45/17 on and no rollin required althogh is vvvvclose

[DanJones]

id probably get them rolled anyway just to save any hassle...i do like a blast along some bumpy country lanes every now and again and there are quite a few bridges and jumps on the way so would be sensible i think in my case to roll them.

zayyan- any slower and ill be going everywhere at snails pace...at the moment a 1.2 nova is the same speed as me on the flat and i can just about ease past one going up hills so dont really want to lose any more speed...lol

DAN

[Moofles]

dave's right (well done big d ) - 215/40/17 is the correct size to keep the overall size right. but the extra unsprung weight may make a difference....

p.s. for 18s you want 215/35/18. oh and clearance: 215/40/17 and 215/35/18 will have no probs with a 7.5J (maybe 8J) wheel, on standard lowering (40mm odd)

p.p.s 225/45/17 is quite a bit bigger than standard, acceleration would almost certainly be slower on those than standard sized tyres (and same with 225/40/18). both of those are e36 tyre sizes i believe.

[tomstickland]

For an a/b/c (eg 195/55/15) tyre the rolling diameter is:
d = 2*a*b/100 + 25.4*c

If you increase the rolling diameter by 1% then you will suffer a 1% drop in acceleration.
Larger wheels also move more metal outwards so will increase the wheel inertia which also reduces acceleration. The weight equivalent of the inertia of a typical wheel can be up to half the weight of the wheel.

Anyway, if you choose the right size then it wont make much different to acceleration.

[Adammcf]

As Tom says the rolling diameter isnt really the killer, its the extra weight of the wheel. Ive never put anything bigger than 16s on my last 3 cars (the Sport has 15s) as I didnt like the way the it killed response and the handling wasnt as good.

[E30BeemerLad]

real irony with alloys is that they weigh more than steelies (unless you have megabucks for mag alloys) and also aren't as strong.

[DanJones]

Theres some good information from you there guys..much appreciated...looks like 17s are the way forward for me then....bit cheaper on the old tyres than 18s anyway so cant complain really...and theyll look much better than the 15s anyway

Thanks again

DAN

[orangecurry]

are you selling your 15s then?

[DanJones]

I would do but my brother was given them for his 18th and they were put on my car when he had it....(hand me down lol) so not really up to me but i think he wants to keep them...they are scuffed like hell anyway....but theyre a nice design

[tomstickland]

real irony with alloys is that they weigh more than steelies

Not always though. I had a fetish for putting Steel wheels onto my Astra for anti chav reasons and also for the rally slag look. Then I spoke to someone who had weighed various wheels and found that the Vauxhall Alloy wheels were lighter than the Steel ones. Not always the case though.