I've just bought some poverty Pork…

[Chris Stott]

Escy said:

I don't get the whole balloon tyre thing, it's a sports car, sounds like you want it to ride like a 70's Rolls Royce.

Which is never going to happen on KW’s.

The question is... what would you be trying to achieve by changing the tyre widths?

If it’s a better ride, you’d be better dumping the KWs and fitting stock suspension.

If it’s changing the handling balance then take it to COG and tell them how you want the car to drive... If it’s possible, they’ll probably be able to do it.

[911-32]

I reckon you maybe could fit 16s over 996 brakes. Here is why...

In the 1990s a few crazy kiwis started importing 964 cup cars to NZ in order to race them. At that point, the Club race series only allowed max 16 inch wheels with the RE71R tyre as a control and in max sizes of 225/50 and 245/50. Those same crazy individuals worked out you could get a custom made 3 piece wheel from Simmons in Oz that would fit over the Cupcar brakes. Those would be 330mm discs and big red calipers IIRC. So maybe its possible.

Personally, I would stick to LW 17s as suggested.

[Escy]

I don't really understand where you're coming from. Let's assume you have a set of 18's and 16's, both the same weight with the same rubber and contact patch, I'm expecting the car on 18's to be more stable during cornering as it has stiffer sidewalls so leans less on the tyres. The trade off is the ride is a little harsher.

[ATM]

The way the tyre wall flexes affects the handling massively. Low [super low] profile tyres do not really have any tyre wall flex. A balloon tyre will flex plenty.
We have different grades in between. That's why I remember really enjoying my friend's bog standard mk2 escort on skinny balloon tyres. It was great fun at pedestrian speeds.

I'm going to use a Formula 1 reference here - please dont think I am comparing a 996 to a formula 1 car because I am not - but when you watch the slow mo replays of them going over the curbs you can see the tyre moving around while the car is basically stationary. And they move a lot - in my opinion.

[Rosewood Red]

ATM said:

Good point Chris. The space saver is 16 inch. So maybe there is a 16 inch wheel which will fit.

AFAIK, the space saver is 17".

Or at least the ones in both my 986s (2.7 and 3.2) are! Like so:

DSC_0404 by ash_ashy_mo, on Flickr


Assumed this was because 986 S / 996 front brakes wouldn't fit under a 16", and it didn't make sense to have different sized space savers.

[Escy]

anonymous said:

[redacted]

Those cars have skinny tyres to keep them an entertaining drive as they don't have much power. As I suggested earlier, rather than less tyre you could also get more power.

I'm ruling it out small wheels. I need the most tyre I can fit on my 986, wider wheels tend to be 18's so that's what I'll end up running. I did look for the widest 15's or 16's I could find for drag racing, nothing in a decent width that's OEM that's sensible money.

[Escy]

anonymous said:

[redacted]

I appreciate size and weight typically go hand in hand but it's not always the case. Rather than banging the drum for the smallest wheels possible you should be saying the lightest? Or am I missing something?

Would you rather a set of 18's that weigh less than OEM 17's? (both options have the same width tyres, only the profile is different)

Handling preferences with larger sidewalls is personal, I don't like feeling tyres move under the car as they load up, you might think that's a fun trait, to me, it's disconcerting.

[ferrisbueller]

pete.g said:

ferrisbueller said:

ATM said:

I have flirted with the idea of fitting the 2.7 986 brakes to my 996 so I could use the 16 wheels but its doesn't sound simple.

You read like an accident waiting to happen.

This is one of the very few threads that doesn't stray into a spat every few posts.

If you have a reason to doubt the wisdom of someone's course of action, then you can give your view, rather than post negative assertions framed in provocative language.

As opposed to providing responses/advice to questions on subjects you demonstrably know nothing about interspersed with stories of on-road experimentation and "ideas"? DYOR always applies but some of the input provided on here in the context given is dubious at best. I'm afraid that's going to seem harsh; c'est la vie.

If chucking a set of 205s on front wheels on the back of your 9X6 sounds like a good idea then carry on - your insurer will probably love it. Sure, why not downgrade the brakes at the same time, just for good measure? I'm fairly sure my mechanic would refuse to do it. If flagging things like that as something that probably needs some proper looking at is spat inducing then consider me a spatterer.

edc said:

It might sound crazy but I wouldn't call it dangerous. There are people driving around in 3.4 originally 2.5 Boxsters on 2.5 brakes. People driving TPC turbo'd Boxster/Cayman S with approaching 400bhp and upwards on standard brakes which are the same as a 996 Carrera. People driving turbo engine transplants with standard sized brakes.

There's an important differentiation between "Will it work?" and "Is it fit for purpose?" Personally I would question the wisdom of that, also. Somewhat predictably Porsche's own brake sizes increase up the range. Physics is a bit of a bh in these situations. Based on experience, I wouldn't want less brake on any car I've ever driven. Maybe less servo effect, but not actual braking ability.

In terms of weight, a Boxster is about 70kg lighter than a 996, in %-age terms that's not huge, it's a passenger. However, there's almost 100hp difference between base 986 and base 996 (something like 70 vs 2.7?). I don't have the beard knowledge, nor the time, to go into specific brake sizes by model and MY but the base Boxster set-up is smaller than the base 996, which is smaller than the Turbo etc (and we're not just talking the single dimension of diameters; width varies, as do other components and their material properties).

It may be anecdotal but in my understanding of the brand, based on reading, watching and driving, they've got a pretty solid reputation of having good brakes. There are fundamental reasons why Porsche sized the brakes the way they did (and do) and if that dictates a change in wheel size then so be it (aesthetic is probably the bigger driver in most instances but there's a fundamental set of issues around physical size, and various coefficients of friction). To look at it another way, if the base 986 brakes were fit for purpose across the entire range then why didn't a manufacturer in financial strife just fit those brakes to every car and bank the financial benefit. You'd think a bean counter would challenge the engineering department with that one. One could argue Porsche's engineers made numerous fk-ups on these cars but probably not the brakes.

Whereas I would absolutely agree with the side that says cars could be argued to be fitted with needlessly large wheels and tyres in many instances, I am much less likely to agree with regard to brakes. The "demand" (where the fk does it come from?) for cars fitted with stiff suspension, hooj rimz and huge tyres is a blight on most things enthusiasts actually value and makes most modern cars genuinely unpleasant. However, to come full circle, actions such as retro fitting the brakes off the base model and putting the smallest front wheel and tyre combo on the back of your 911 probably isn't the correct course of action and to blithely suggest someone else do it is IMO inappropriate.

Apologies, somewhat time constrained at present so lacking in detail I'd normally try to add.

[Escy]

anonymous said:

[redacted]

My 986 will be 450+bhp which is why I need the widest tyres I can fit.

When talking to a well known figure in the US Porsche racing scene, his recommendation on tyre size for the front of a fast road car was as much tyre as I could get on the front. He runs race cars with a square setup but rather than go smaller at the rears, he goes bigger at the fronts to stop the understeer.

[ferrisbueller]

Escy said:

anonymous said:

[redacted]

Those cars have skinny tyres to keep them an entertaining drive as they don't have much power. As I suggested earlier, rather than less tyre you could also get more power.

I'm ruling it out small wheels. I need the most tyre I can fit on my 986, wider wheels tend to be 18's so that's what I'll end up running. I did look for the widest 15's or 16's I could find for drag racing, nothing in a decent width that's OEM that's sensible money.

I think yours is an exception with regard to having a greater need for grip/traction.

[Escy]

Regarding brakes, don't forget your stopping performance is limited by tyre grip (another reason wider tyres are preferable). You'll stop from 100mph just as quick with Boxster base brakes as you will with 996 Turbo brakes. The difference is you'll only be able to do that a coupe of times on smaller brakes before they overheat as the 996 could take it all day as they have more thermal mass.

I do agree with your point though, smaller brakes and tyres is daft.

Edited by Escy on Thursday 12th December 14:32

[ferrisbueller]

Escy said:

Regarding brakes, don't forget your stopping performance is limited by tyre grip (another reason wider tyres are preferable). You'll stop from 100mph just as quick with Boxster base brakes as you will with 996 Turbo brakes. The difference is you'll only be able to do that a coupe of times on smaller brakes before they overheat as the 996 could take it all day as they have more thermal mass.

I do agree with your point though, smaller brakes and tyres is daft.

Edited by Escy on Thursday 12th December 14:32

One of the coefficients I was referring to.

[olv]

Oh no... shall we just skip to the end and start talking about racing sims?

[olv]

anonymous said:

[redacted]

An interesting watch, although the skiing was actually the best bit.

[Merp]

I think ill just stick with what ive got then

[BigBen]

olv said:

anonymous said:

[redacted]

An interesting watch, although the skiing was actually the best bit.

Sort of on topic, Tim Schrick bought my first Ariel Atom from me, he specifically wanted a Rover K-series powered car as they are lighter than the later Honda cars and still have enough power for the road.

[Chris Stott]

Have to admit, I have looked at alternative tyre sizes for my 996, but purely for aesthetic reasons. Mine is lowered, but I'd like it lower... or rather I'd like the top of the tyre to sit closer to the arch. I just like way this looks. I also like the look of fatter sidewall tyres... though going to a 17" for me doesn't work as although the sidewall may be higher, it's lost on the smaller diameter wheel (smaller overall RR).

As it's on -30 springs, not coilovers, options are limited... a 265/35/18 has the highest sidewall and RR of any of the Porsche tyre options... a 295/30/18 has a lower sidewall and smaller RR. I've considered fitting a 265/40... which gives an extra 0.5" of sidewall, and may do this when mine need replacing... along with going to a 235 front to get similar (though smaller) effect.

Given the percentage of time I can actually drive mine properly hard is a relatively small percentage, I'm not bothered about chasing finals fractions of 'feel'... it's already more 'feelsome' than virtually anything else I could get for the same money.

Given the amounts of traction these cars have, anyone wanting to (or claiming to be) sliding them around on public roads is either going to end up having a massive accident or in jail. They don't have the power to power oversteer and 'bunging them in' to try and get the back round is just daft on the public roads.

[ATM]

The 9x7 cars switched to bigger rears and I think this was facilitated by them losing the spare wheel and therefore not needing to keep the circumference / diameter the same front to rear. You could try the bigger rear. The 996 and 997 are basically the same car right. The 996 feels quite low geared to me so I think you'd hardly notice a change to 265 40 and this will give you a bit more tyre wall to play with.

[Chris Stott]

I didn't know the 997 was a 265/40... good to know.

It's only a 4% RR difference, so won't make much difference to gearing.

[ATM]

Chris Stott said:

I didn't know the 997 was a 265/40... good to know.

It's only a 4% RR difference, so won't make much difference to gearing.

Yes on 18 inch 265 40 and then on 19 it is 295 30. That's for the c2. I think the c4 is a bit wider but who cares.