17 s. Performance affected

[172Cup]

Guys et Gals,

Ive just put some 17" Turinis on my CUP and over the past couple of weeks, I seem to have convinced myself that they have adversely affected performance to the point of it feeling slower but especially concerning in-gear flexibility. Now the rolling radius is correct a la 16"s so there should be no discernable differences. When I went to 18"s on the WRX, there was no change, or no change was felt.

Has anyone any comments or experience on putting 17"s on a 172 and feeling the performance alter, for better or for worse???

Cheers,

172CUP

 

[KDF]

There was posts about this already, someone had put 17s on their 172 and noticed a difference in performace when racing other cars, think he went back to 15s or 16s..

try doing a search.

 

[Adams_16v]

without a doubt mate. i have had 17s and 15s on over the past couple of months and the 17s definately slow it down. To the point im going to put 15s on again for most of the time...

 

[Tom]

if the rr is the same then there shouldnt be a problem

maybe its the weight (but then it wouldnt be because the 17s are lighter)

arrrrrrrrrrrrrrgggh i dunno!!

 

[Adams_16v]

well i compared one 17 against a standard 15 and the 17 was loads heavier. But that just mine, the turinis should be ok on that front

 

[Steveold]

Its the extra rubber on the road you get from 17s and the weight is more than 15s

 

[Tom]

but the cup starts with 16s that are heavier

explain that?

 

[mick_cup]

With 205/40 x17 surely rr is not the same as 195/45 x16.....a 205/35 x17 would be closer.

 

[RobFenn]

Tom are you going to be selling your Turinis at some point?

-Rob

 

[Steveold]

Quote: Originally posted by tomclio1.2 on 13 May 2003


but the cup starts with 16s that are heavier

explain that?

Yeah the cup has 16s and if I owned one I would stay with 16s...... If you put 15s on a cup it would go faster but not corner so well.

 

[Dansta]

Recently put 17s on my cup, got 205/40/17s, I knew there would be a diff in performance but had to make the sacrifice to fill the arches properly. altho i havent really noticed a bog diff really to be honest, still goes like sh*t of a shovel, and feels more grippy around roundabouts!

 

[Steveold]

Yeah but it will slow u..... more grip means more friction on the road which means the engine has to work harder which means it slows u down....

 

[geordiepaul]

My area of speciality!!!

I presume you have 205/40R17 tyres? These do fall within the 3% tolerance that everyone talks about but they are 14mm bigger in diameter which is the killer. You say you fitter 18s to your scooby and noticed no differene? Post the old tyre sizes and new tyres size and Ill work out the diamter. I bet they are the same. The MINI Cooper S is a prime example the standard 16s and the option 17s have exaclty the same diamter so no performance loss.

My speedlines are currently having 195/40R17s fitted I will post my opinion once I have them fitted. The best match would be a 215/35R17 but these are v. expensive and would IMO be a very harsh ride.

When I raced Cuppy 172 in his Cup I was about 10 car lengths back at about 110mph then with the 16s back on it was neck and neck so there is the proof you need they slow you down big time!!!

 

[Cord-172]

Havent noticed hardly any difference with 17s instead of the original 15s

 

[Cuppy 172]

geordiepaul,

I agree with your statement about the 17s they did slow you down, But!!!!!!!!

When you had your 16s back on I actually caught you and passed you by the time we had reached 100mph

Short memory mate! (I forgive you )

 

[geordiepaul]

Hmmm got you! See the other thread about Cuppys misguided comments

LOL

 

[geoff_clio182]

I never noticed any difference when I had 17s on my 172 MK2

 

[Gav76]

Cant really comment on any difference, Ive only had 17s on mine. Ill let you know when I put the winter wheels on!!

Dont know if its the wheels but the 172 feels like it should be going faster. Looking at the speedo you are going fast, it just feels like it should be pulling harder.

 

[viceroy]

I think I read somewhere that the percentage difference between the diameter of the new and original wheels is the same as the percentage lost or gained in acceleration, so....

if your new diameter is 3% larger than the original you theoretically lose 3% of your acceleration performance

How this would equate to real life number is a little bit of a guess but Id wager it would be the same as losing 3% power at the wheels

And I dont think this takes into account the weight difference either which probably works in a similar manner

 

[telford_mike]

Quote: Originally posted by geoff_clio172 on 13 May 2003


I never noticed any difference when I had 17s on my 172 MK2

I remember following Geoff around the circuit at Bedford when he had those 17"s. There was no discernable difference in performance between his car and mine with 16"s.

 

[paddymph]

god knows? i would have thought it would be slower?

 

[jonnyboy]

Bigger wheels = Engine does more work to make one revalution of the wheel = less power to distance covered.

Answer is a straight yes. Bigger wheels will definately have some degree of adverse performance on your car.

 

[geoff_clio182]

Thanks Mike! That was before I had the Induction and Chip on the car too.

 

[TimO172]

Simple calculation gives the differences from 195 45 16 to 204 40 17

195 45 16= 22.9 inch diamter

205 40 17 = 23.5 inch diamter

Therefore the speed reads 2.4% too slow. When you are doing 60 you are actually travelling at 61.4 mph. Couple this with the increase in unsprung weight, maybe 17 inch flow form is lighter but tyre wont be, and the fact that a wheel is rotational mass you will suffer.

Standard size wheels rule.

 

[Sandro]

Hi there
Much has been said already; the point is, besides the scientific approach, some drivers will notice a difference and some wont. It all comes down to your driving style (3 wheeling around the corner anyone?), the roads you are driving etc.
I surely believe that it will affect the performance of the car (as long as speed is concerend). Of course you might get a bit better performance in corners, though.
Fact is, 17" look better. But, overall performance (driving dynamics) was more important to me, so I stick to the 16" my Clio came with (changed the rims to some more beautiful ones, though).
Cheers
Sandro