Are 18s really needed?
 

Getting my WRX PPP'd this Saturday, they recommend 18" wheels to get the most out of it! Is this fact?

I am new to all this, and to be honest, I don't think I can afford to buy new wheels!

What do you guys think on this?

Mark.

Just put 18"s on mine and to be honest it will need lowering now so unless you are planning on more mods im not sure why "they" would recommend this. Never heared of this before mate?! When you say "they" are you talking of Subaru? I see your from Wales too, are you going to this months meet? There will be plenty of advise and friendly faces there to answer your questions.

no need to get 18's

still new to subaru's ,spent all my spare cash on optimax for the first few months. better to spend a few hundred quid you "can" afford on track days learning your cars characteristics,than a grand you can't afford on wheels.
all the best tony

18s are a cosmetic mod.

handling is much sweeter on 17s

the money is better spent elsewhere imho

The contact area will be slightly increased with 18" wheels/tyres and also the amount of lateral flex in the tyre will be reduced as it will be a lower profile. Putting these two factors together should mean greater traction through cornering plus better feel.

The downside will be a harsher ride and more expensive tyres! There's a lot more than just cosmesis to the right wheel/tyre combination ;)

Thanks all for the good advice, much appreciated! Yes mate will do my upmost to be there at the meet - look forward to seeing you!

Thanks all!

Mark.


BTW, got the 18" info from here:

http://www.prowicz.co.uk/ppp.pdf

Just put a search in mate, i'm sure this has been discussed before with Mike Wood from Prodrive having an input.

Much depends on the tyres though. Those god awful Bridgestone RE070's are utter sh1te, whether on 17" or not.

Prodrive recommend 18" and funnily enough, no mention of Bridgestone tyres anywhere.

Same as Ferrari. Remember Top Gear testing the F430 round the Top Gear track? Clarkson said that the Ferrari Test driver reckoned "it would be faster if it wasn't on those Bridgestones".

Personally, I have Michelin Pilot Sport 2's on 18" wheels, and it handles and grips way better than it was on Bridgestone rubber on 17" alloys.

18" on tracks are one thing, but using them on cross country pot holed roads are another - so i've gone back to std 17" wheels and don't regret it.

Nick

The old Subaru brochure used to recommend 18's if having an STi ppp'd to deal with the extra torque! Not sure if current brochures recommend the same.

Agree -17s with good tyres (F1 Toyo) are considered the best compromise for all road situations.

Although I come across people who find 18s fine.

Personaly I would spend the money elsewhere

according to the prodrive website itself, there is no mention of 18"'s on the WRX PPP, they recommend them only on the STi and to be honest, considering they made the mods... I'd take their word for it ;)

As someone else has said, there's been threads in the past on this to which Mike Wood has contributed. I recall one in particular where whilst he gave clear arguments for running 18s on a PPPd STi, there were none forthcoming for a PPPd WRX.

I run 17s on my PPPd WRX and they seem a good compromise.

I'd spend the money on Prodrive springs -- that's a mod that will make a difference!!

17" mate and decent tyres are the way to go

The same thing applies to a WRX really. It's about managing the torque by having enough traction. Whilst the WRX doesn't have quite as much as an STi, it also doesn't have a front LSD either and when pushed (particularly in the wet) it can suffer with a spinning front wheel. Fitting 18" wheels and tyres goes a long way towards making sure it's got enough traction and grip to cope if you've chosen a decent tyre. It's now even more appropriate on the 06MY cars as the WRX PPP is well over 300 lbft. Springs also help as bodyroll is reduced and traction improves.

Mike

I have read with interest in a lot of places that 18`s are recommended after PPP and I am contemplating it myself also. But if the car comes from the factory/dealer on 17`s surely the speedo is calibrated as such and then the change to 18`s will knock the speedo out somewhat ?. So do you need to have the speedo re-calibrated ?. Or does it not make any difference ?.

The 18" tyre is a lower profile than the 17" and is basically the same diameter. Depends on the individual tyre manufacturer as they all vary slightly but it'll be within less than 1% of the original tyre rolling radius.

Mike

Couldn't agree more. :thumb:

In the soaking wet at Bedford, a WRX02 295bhp AP Brakes and my STi02 PPP & PHP, both on 18"s. Striaght line speed not much difference but mine was lapping him on the 5th lap.

I took him out in mine, He commented how the Sti had far more frontend grip than his. His next mod he vowed was a Front LSD ;)

I reckon Prodrive springs were excellent on my 02 Sti far better than the WRX Eibachs (fitted from new by mistake by dealer :(

IMHO

Tony

18" wheels
 

When thinking about changing wheels / suspension please remember that Impreza's will all react differently to each other: WRX vrs STI, STI vrs STI with DCCD etc etc. Secondly you need to try and make sure that the rolling radius stays as closely matched as possible.
My car for example (Impreza STi 2005 type UK with DCCD) was fitted with Bridgestone RE070 tyres that in my opinion are superb. Before you start slayting them please remember that the tyres from UK are different to the Bridgestone RE070's that come on the Imported models!!!!
I changed my wheels to 18" because I owns a business that sell wheels and my car is our company demo! I firstly made sure that the choice of 18" tyre matched the rolling radius perfectly (637mm for the record). I chose Toyo's T1R tyre. These tyres worked very well and I have lapped consistantly in 1.22 seconds around Castle Combe. I have now changed them to TOYO PROXY R888. These are also very good in the dry or wet but not with standing water!
We as a business that specialize in Race and Rally test lots of different cars and tyres and as I'm sure Mike Wood will agree will tell you guys and girls that different suspension set ups on cars will make a difference. The point I'm trying to make is whilst these forums are very good for sharing information, they can sometimes misslead people. If in doubt try and speak to an expert or at least someone who can give some information based on using the product at competition level.
Hope this sort of helps people understand. Can open-worms everywhere I expect.
Carl

Mike - can you explain why fitting 18 inch rims (with a reduced profile tyre to maintain the same rolling radius) will give any more traction than a 17 inch rim fitted with the original profile tyre, all other things being equal? If the rolling radius is the same, then surely the geometry at the ground will be the same? In fact you might wonder if the higher profile tyre as fitted to 17s would give better grip as it would be slightly more compliant under less than perfect road surfaces (witness some of the tyres used by the 1/4 mile boys).

I have recently fitted ultra-lightweight 17s with exactly the correct width and offset(6.95kg per rim) and the handling is sublime over the OEM (heavy) wheels. I could understand an 18 inch rim spinning less under acceleration because of the greater rotating mass, but surely that's a heavy penalty to pay if it is the reason :confused:

Would be interested to hear your thoughts
Cheers, Andrew

Lets take the STi to start with. The std 17" wheel is heavy and the OE tyre has a very stiff sidewall as well as being less than optimal in the wet with a very abrupt loss of grip at the limit. Can't comment about other 18" wheels but ours are up to 3kg lighter than some of the OE wheels, the tyres we recommend have better grip in the wet than the std tyre as well as more progressive feel at the edge of the grip envelope, probably due to having a more forgiving construction. From 06MY they are also a little wider as well.

The OE WRX tyre has similar features to the STi although not as extreme but fitting 18" wheels and tyres allows you to use a slightly wider tyre with characteristics better suited to UK use. They also fill the arches out a bit better on the WRX which I think looks a bit 'weedy' on the std 17" wheels!!

What you need to remember is that whilst there are generalisations such as a lower profile tyre will give a worse ride, it's rather more complicated than that. A 45 profile tyre with a very stiff sidewall will still give a worse ride than a 40 profile tyre that has some compliance in the sidewall. Every tyre has different characteristics, we've had 3 visually identical tyres giving different feels in our testing but that's why it's important to test the specific tyre in the specific conditions on the spec of car it's going to be used on. Look at the effort F1 teams have had to put into tyre testing in the past to find the optimum tyre for each circuit and weather conditions.

Mike

Mike, can you remind me which tyre you recommend for your 18" rims please?

XRS

Am I right in thinking you have a Type 25? If so, what model year is it?

Mike

I found the Bridgestone 17" re040's way too hard on the sti.
By Fitting Michelin ps2's I have increased overall grip in all conditions, and ride quality is better while allowing more control on the limit.
So in my view, everyone should change to Michelin ps2's on the 17" rims before jumping on the 18" styling bandwagon.

Dipster

Yes, I do. :) MY05

In that case, 235/40ZR18 95Y Corsa Asymmetrico although the Michelin PS2 is pretty good too if its the 95Y version.

Mike

Thanks Mike, all I need to do now is get some P-FF7s :)

Mike, what would you recommend as a replacement tyre (235/45-17 RE070) for a JDM 06 STi?