275 width rear tyre for a 2005 Boxster ?

[multispoke]

Currently have a Conti Sport 3 N1 18 265/40 and Vredestein 18 235/40 95 loading (not N rated) standard sized tyres. Last year i bought a set of Cont Premier Contact 6 for the front with the 91 loading and had expected that equivalent ones would come out for the rear. In hindsight I should have bought N rated N1 Conti for the front but though a newer generation tyre would be better. Only size available for the rear to match the front in the same make is the Continental Premium Contact 6 in 18 275/40 standard loading. I have not put the front tyres on yet but both the rear and the front now both need changing.
I could get a set of Conti Sport 3 for the rear OR a Michelin Super Sport OR got for the bigger 275 width - that's if it will fit the 9J width rim.
Current preference is for the Michelin SS, 275 width or the Conti Sport 3 or I could get some other newer generation to match the new to be fitted front tyres.
Would greatly appreciate your inputs. Did have a good look on here so aware of the understeer bias of the Boxster setup. Original Boxster on the 18s had 225 & 265 so there was probably a good reason for the change to the 30 difference on the 987 models.
The US do stock and Extreme Contact in the right size but it supposedly a totally different tyre compound. Have emailed Continental and got the brief that I should be using N rated tyres that match on both axles.
Front tyres are bought - not too sure what car they would fit if I had to get rid of them.
It's a standard Boxster 2005 model 987 with close to 80K miles. Runs sweet. Have stopped worrying about the IMS finally

[multispoke]

thanks for the reply cmoose.

checking the rim width of 9J it seems the 265 is the max that it can take. The 275 does seem too big for a base 2.7. Initially I thought that the 18s were too much for it and had though about downsizing to 17s. After driving it for a good 3 years now I feel that it needs the 18s.

Contacted Camskill about returning the Conti Premiums but there's only a 14 day window. Thankfully the 235/40s 18 are common enough so that could get a new home.

Understood from them changing to non-rated N tyres could have insurance implications since it could be deemed to be a modification. Unlikely it would get enforced here particularly if I stuck with the standard size as specified in the owners manual.

Ran the idea past him of the Michelin P4 which are available in the 18s - 255/40 and 225/40s which gives the 30 difference and are a new generation tyre but he wasn't keen on them. He felt that that would not be as good as a N rated tyre referring to the side wall flexing compared with a N rated tyre. And they are not in the manual.

Got the impression but could be wrong that with a Conti Sport Contact 3 N rated tyre that they may have improved the compound. Have noticed 2 different tyres listed that were N rated with different with Rolling resistance ratings E & F. The E might be newer but it is not listed on the eirtyres web site.

Of the 2 tyres Conti Sport 3 and the PS2 the Conti had the better wet rating in the fronts. Leaning towards the Conti all round.

Looks like the 18s have been left in the dog house with only the 19s upwards getting the new generation sizes.

If I had a choice I would have liked the P4S.

[DJMC]

You need correct spec sizes for insurance too, or insurer's agreement to alter, in writing.

Conti Sport Contact 3 are excellent. So are 5 but wear out twice as quickly in my experience.

Why not phone Conti and ask them what to put on the back (within spec) if you keep the front Premium Contacts?
They may have a solution e.g. Sport Contact on the rear is fine? They can advise if front/rear tread is compatible.

The issue is safety here. No insurance complications if all tyres are within spec, even if you mis-match tyre make/model.
But... you need to ensure front/rear are a suitable combination. This is difficult with differing brands front/rear as the two manufacturers won't be able to satisfy you (or even suggest) that their tyres go well with another maker's.

[multispoke]

To give Camskill their due - they gave me quite a bit of time on the phone. He was referring to the GT3 / GT3RS in relation to tinkering with tyre specs. I had mentioned that many seemed to have ignored the N rated going with Michelin SS on their 911s. He knew about the Pilot 4S being a refined road version of the SS. The Pilot 4 does not appear to be in the same category. I was impressed with the soft velvety side wall look on the new Pilots and it does seem to be on the Pilot 4. It was a sucker factor.

Back to the 275 width - some guy on One Take with a 2008 Cayman S runs SS on 275 with 245 but his rim width is 10 and 8.5. So with the standard 9J rim on the back this definitely rules out the 275.

On the email to Continental they give the standard response of it must be N rated so they wouldn't entertain what rear tyre could go with the Premium Contact 6 on the front. If I had ordered the Sport Contact 6 maybe that could have been matched up with something like a SS. Camskill stated that the Premier Contact is more of a eco tyre and will have a soft sidewall particularly in the 91 loading that I got.

Reading some of the blurb from Continental they have dropped the Sport contact in the 18s stating that they will only be available in 19s upwards. Yet you can still order the Sport contact in the 235/40 - although its the only size that they do in the 18s.

Camskill's Price is £162 for Conti 3 N1 on the rear and £108 for the same equivalent on the front. I would have placed an order for all 4 corners there and then if they took back the 'old' ones. Eirtyres price for the Conti rears is €246 so Sterling prices look good. So relatively prices seem OK on the 18s from the UK.

If I can get a few bob for the Conti Premium 6 I'll let them go and put it towards a new set of Conti 3 N1 for the front.

Preference to change all corners with new tyres and not do it piecemeal.

Again many thanks again for all your inputs.

Edited by multispoke on Tuesday 14th August 19:28

Edited by multispoke on Tuesday 14th August 19:30

[multispoke]

Apologies on the double post.

I ended up placing an order for 2 Michelin SS for the rear.

I measured the depth on the Conti Sport 3 and I was surprised to get a 4mm depth. So essentially from day 1 they were very average. There's a number of 201498 on the side so it is most likely the year so they are not that old. Front tyres are 3mm but they're terrible in the heavy rain and you feel that you're aqua planning if you're pushing on. Issue is that the CS3 break traction in the dry definitely in 1st and on a roundabout. In the wet I drive like a priest.

I haven't approached the local tyre guy about taking the Cont PC6 off me but I am going to take a chance and put the SS on the back and the PC6 on the front.

Have being a Conti man all along but when I got a taste of a set of Pilots on a Mito QV they were really good. I had the Good Years Excellence on a Mito 155, didn't like them at all so have no inclination to get another set of GY.

After reading about the voodoo magic in the SS with the Dual compound I'm prepared to live without the ECO symbols. The PC6 don't tick the Sport box of the SportContact 6 but I wasn't keen on another 95 XL load rating on the fronts again. If the PC6 are too soft in the side wall to pair properly with the SS I have the option of getting the Conti Sport Contact 6 - they wouldn't break the bank.

So really all that is out there for the 18inch Boxster 987 in the 'new' generation tyres is the MSS and the PC6 for the front & the rears. The MSS are not new generation but they were ahead of their time. Downsizing to a 255 & 225 for the Michelin Pilot 4 on a 2.7 might be an good option but only if I got the insurance guys on board.

I will be committing the mortal sin of mixing 2 different brands. If it was a 911 I wouldn't do it but the amateur is telling me that I'd be OK. It's bound to better than what I have. I'm not keen on another set of Cont 3 N1s particularly on the rear.

[DJMC]

anonymous said:

[redacted]

Yes, it is true.

You have an accident with a tyre 10mm outside manufacturer's spec and your insurer could use it as a reason not to pay out.

If your tyre size become obsolete you need to find an insurer who will agree (in writing) to a slightly different size/spec.


My enquiry a few years back to my insurers (or "gimps" as you wish) as follows: "...The standard Porsche rear tyre fitment is 265 45 18 and the Nokian ones are 255 45 18. It is well known that narrower winter tyres are better in cold conditions, but when I phoned in earlier your underwriter told the call centre staff that they had to match the manufacturer's specification."

And their response after many emails back and forth:

"I can confirm from our telephone conversation this morning, that Acromas Insurance Company Ltd, who currently underwrite your policy have agreed for the winter wheels and tyres to be added to your policy and your policy schedule will reflect this.

You have told me that you will be changing the wheels and tyres back to the original ones come next summer, I have noted this in our system for future reference.

Please be aware that every year the wheels and tyres are changed to a non manufacturers standard specification this will still need to be referred to the underwriters as the terms or underwriters may change."


Go on... carry on arguing as you always do...

Ah but, yer, but...

[shrink1061]

just get some Michelin Pilot sport 4, they come in the right sizes, work well, and are a huge step up on the old N rated pilot sport 2.

Job done.

[anonymous-user]

anonymous said:

[redacted]

Actually some insurers do insist on original manufacturers’ spec size unless you inform them and seek “permission”. Came to light when I was researching winter tyre implications.
This chart from ABI, showing which company does and which doesn’t, happens to relate to winters, but some insurers, like the one mentioned in the post above, have same policy for normal tyres. It is not about the law, but individual terms and conditions. Vast majority don’t seem bothered thankfully.
https://www.abi.org.uk/globalassets/sitecore/files...

[drjdog]

The standard sizes of tyres for the 17, 18, and 19" wheels all have very slightly different diameters, so I doubt insurers could give you too much grief about the diameter, but maybe they would about width.

I'm more interested in why 95 load rating tyres are specced for such a light car. You could go down to 85 (550kg per tyre) and still be well within the limits of the tyre with two heavies in it. Even 91 would be a very high safety margin. I assume higher load rated tyres are heavier.

If you have a 2.9 or 2.7 like me, W speed rated (168mph) tyres should suffice, too. S models would probably require Y. Again, higher speed ratings must equal heavier tyres, no?

There's much more choice in tyre if you are flexible on speed and load rating, and still keep well within limits, never mind ignoring the silly Porsche N rating.

@multispoke "There's a number of 201498 on the side so it is most likely the year so they are not that old"

If that number is a DOT number, the last four digits are the week and year of manufacture - this migh be week 14 of 1998.

[DJMC]

Discombobulate said:

Actually some insurers do insist on original manufacturers’ spec size unless you inform them and seek “permission”. Came to light when I was researching winter tyre implications.
This chart from ABI, showing which company does and which doesn’t, happens to relate to winters, but some insurers, like the one mentioned in the post above, have same policy for normal tyres. It is not about the law, but individual terms and conditions. Vast majority don’t seem bothered thankfully.
https://www.abi.org.uk/globalassets/sitecore/files...

Yes, your link relates only to which insurers need to be advised if fitting winter tyres, of the correct spec, not fitting WRONG spec tyres.

Accordingly Acromas are listed as a "no" but when I wanted to fit winter tyres, 10mm narrower at the rear, they DID need to know, to go away and think about it, to come back and say initially that I can't, and then after some more explanation finally agree to it, in writing.

The "in writing" bit is important as although you may think they are recording your phone conversation this may not be available to you after an accident.

There may be some insurers who don't give a damn what size, width, spec, tyres you fit and are happy to insure you whatever, but I very much doubt it. I would therefore maintain that ALL insurers insist on original manufacturers’ spec and size unless you inform them and are granted “permission”.