Tyre Swap question?

[jeegnesh]

1997 2.5, had 18's on them since I bought them, Michellin Pilot Sports 265, the issue is that the tyre does not come over the alloy as shown by this picture:

Everywhere I go I get told by tyre and indy's that this is the wrong size tyre and there room to go bigger, but my sport's are literally new, so was not going to bother.

Now a tyre place round the corner for me, is telling that he has nearly new Pirreli P Zero Rosso XL N5 295/30/18 that came of a 911 who bought new alloys from him. He's going to get the tyres in so I can see them and he's only going to charge a changover fee, he thinks for him my size is more sellable then the 295's and he has a few 295's already, well so he says.

Questions I have is:

1 - Mich N1 Front, Pirreli N5 Rear's: Any issue with doing that kind of mix?
2 - Pirreli Rosso XL N5: good tyre? grip? wear quick/slow?

Lastly I don't track the car, and am not a boy racer in it, not to say I abide by everything I should, but hopefully you get the idea. The reason for me for this change is that the alloy will get some level of protection and look better, I just had them refurbed because they were badly kerbed due to the no protection and the wife not taking enough care.

 

[Mark_Bennett]

Looks to me like the wrong size wheel. What is the rim width?

Putting 295s on you might find that they foul on such as the brake lines. You may be able to tie out of the way, but I can't guarantee.

DO NOT mix makes front and rear.

I think you need to find a set of wheels with appropriate size tyres for your car. These don't look right. (Sorry! [&o])

 

[jeegnesh]

Don't know what they are, but if the measurement is from the back to the lip, excluding the front I think the rears are 9.5 if I measured them how it should be measured.

The car been to 2 different indy's Jaz and Northway, and Porsche Reading who have commented on the alloys but none have said that they are wrong, the previous owner claimed he bought these specially as they would fit without mod's even though this year and model was never released with an 18 option.

So mixing is a big NO NO?

 

[Nick_USA]

I can't tell from the photo if you have the 9J rears or the 10J. Could you look and the numbers either side of the tyre valve and post the size. Having done that we can advise on the correct tyre size.

Never tyre mix.

Edit: Looking at the first photo is that a spacer fitted to the rear?

 

[jeegnesh]

Here all the marking I could find:

 

[Nick_USA]

.... not the tyre markings .... if the rim is a genuine Porsche one it should have the offset and rim size on the rim itself, normally either side of the valve.

 

[jeegnesh]

.... not the tyre markings .... if the rim is a genuine Porsche one it should have the offset and rim size on the rim itself, normally either side of the valve.

Its not genuine Porsche rim, so no marking.

 

[Nick_USA]

ORIGINAL: jeegnesh

.... not the tyre markings .... if the rim is a genuine Porsche one it should have the offset and rim size on the rim itself, normally either side of the valve.

Its not genuine Porsche rim, so no marking.

you could measure across lip to lip but you may not get the accurate width. Easier to drop by a tyre fitter and use the rim size gauge they use before balancing a wheel.

 

[jeegnesh]

you could measure across lip to lip but you may not get the accurate width. Easier to drop by a tyre fitter and use the rim size gauge they use before balancing a wheel.

lip to lip so the biggest possible measurement, Fronts 9" and Rears 11.5" (Prob wrong) will see try and pop out when I can.

 

[944s2]

Reminds me of years ago my 944 was bought with correct tyres on wrong wheels could never understand why my fromts looked under tyred compared to other 944's!

IIRC the fromt wheels were on back with rear tyres and vice versa

 

[jeegnesh]

I'm not overly concerned, I had it a little over 3 years and it drives well (prob not as nice with original 16 or 17's), but it's true enough have done a full geo which made a big difference. Just would be nice to cover that alloy lip.

 

[oliver]

I don't think 18" wheels were ever recommended for the 2.5 Boxster, and those look like replica Turbo twist wheels - much too wide.

Surely the best option would be to seek out some correct width 18" wheels (ideally genuine Porsche, Boxster specific), have your tyres fitted, then sell the current wheels (here, PH, ebay, etc).

You may not be out of pocket, you'd have the more correct wheels/tyres and it should ride and handle better.

 

[jeegnesh]

ORIGINAL: oliver

I don't think 18" wheels were ever recommended for the 2.5 Boxster, and those look like replica Turbo twist wheels - much too wide.

Surely the best option would be to seek out some correct width 18" wheels (ideally genuine Porsche, Boxster specific), have your tyres fitted, then sell the current wheels (here, PH, ebay, etc).

You may not be out of pocket, you'd have the more correct wheels/tyres and it should ride and handle better.

Confused, as you said 18 were never recommended for the 2.5, so would there by any point going through the hassle of getting genuine 18's when I am happy with the drive?

 

[Mark Elder]

ORIGINAL: jeegnesh

....

Confused, as you said 18 were never recommended for the 2.5, so would there by any point going through the hassle of getting genuine 18's when I am happy with the drive?

er...you might have a tyre come off, crash etc?

It really does look like someone has fitted a wrong combination of wheels and tyres and, if they knew what they were doing - which most of them don't, an MOT centre should probably be failing you car.

You might think the drive is fine, but it might be a lot better with a set of boots that fits.

All that said, fixing this is not going to be cheap!

 

[Mark_Bennett]

ORIGINAL: jeegnesh

ORIGINAL: oliver

I don't think 18" wheels were ever recommended for the 2.5 Boxster, and those look like replica Turbo twist wheels - much too wide.

Surely the best option would be to seek out some correct width 18" wheels (ideally genuine Porsche, Boxster specific), have your tyres fitted, then sell the current wheels (here, PH, ebay, etc).

You may not be out of pocket, you'd have the more correct wheels/tyres and it should ride and handle better.

Confused, as you said 18 were never recommended for the 2.5, so would there by any point going through the hassle of getting genuine 18's when I am happy with the drive?

Actually, 18" wheels are not permitted (Porsche's words!) on pre-1998 Model Year Boxsters. (Model Year starting Sept 2007).
The reason is that the bodyshell needed strengthening in order to absorb the greater stresses over bumps etc that are transmitted.

You have done nothing wrong, but sadly someone who owned your car in the past has gone for wheels with inappropriate widths. The standard 18" rear wheels are 9" wide - that is between the rim walls, and should have 265/40 section tyres.

Again sorry [&o], but you did ask []

 

[jeegnesh]

No problems Mark, always nice to know. It's a pretty old beast, drives well, looks good so I guess I just run these tyres down first, not had any issues as such and it's an aging car, so lets see how it goes []

 

[oliver]

Going back to my earlier point; Porsche never recommended 18" wheels for the early 2.5s, but I'm sure lots of people have fitted them - but with the correct width and tyre combinations.

I'm no expert, but you seem to have under-sized tyres on over-sized wheels. Technically that must present some issues. It's amazing when you see photos of the sidewall flex in hard cornering.

You may well continue to get away with it, but there might also be some safety issues and, whilst motor insurers are not like aviation insurers, they could well decline a claim if it caused an accident and their assessor took a closer look and declared them a contributing factor.

 

[Black80XSA]

It looks to me like you have 10.5" rear wheels. These are best suited to 285/30 tyres, but these wont fit on a Boxster whithout fouling the wheelarch. This assumes the offset or ET value is somewhere around 50. The rim width and offset should be stamples on the back of the wheel somewhere.

Are the tyres safe on that width rim - yes, albeit not to Porsche recommendation, and you run a great risk of tyre wall damage if you hit a pothole as the wall is stretched rather than sitting vertically.

The alloys are wider than standard, so heavier, and are also likely to be heavier because they are replicas. The extra weight will create addition load on suspension components than a genuine set of 18" rims, which Porsche do not recommend for your model year anyway. Its down to you and so far you've not had any issues. There are loads of other cars on the road with oversized wheels so you're not an unusual case.

Rear tyres should be 265/35/18 btw

 

[jeegnesh]

Rear tyres should be 265/35/18 btw

Good to know, and that is the size on the rears right now actually for the last 3 years. So I guess I will drop the whole idea of the 295 and just be careful near kerbs and bug the hell out of the missus to start being a little more aware.

As for geniune 18's what should I be looking out for exactly? Not that I definetly will, but no harm keeping an eye on eBay for a bargain (if there is such a thing on there anymore).

 

[Black80XSA]

Official Boxster rims were 7.5J x 18 ET50 for the front (7.5" width, 50mm offset) and 9j x 18 ET52 (9" width, 52mm offset) for the rear.

Tyre sizes 225/40/18 front, 265/35/18 rear


To pick up nicks comment early int he thread it looks like you are using a significant spacer on the rear axle, so i really do wonder what offset/ET those rear rims actually are ?

This thread might be handy too - especially as i listed the official rim and tyres as an attachment - note the comment at the bottom about pre 1998 cars []

http://www.porscheclubgbforum.com/tm.asp?m=195159&mpage=1&key=offset&#195282