Tyre Options - SWB 911

[MarkIII]

Pretty soon I will need to make a decision on what tyres are going to go on my 68 T/R inspired build.

I have a set of 6R 15s for the front and 7R 15s for the rear. The car will largely be used on the road with occasional track use.

So I have 3 questions which hopefully the forum can help with:

1 I have seen many threads discussing the pros and cons of different tyre sizes. What is the optimum size for the wheels above?

2 I have experience of Pirelli CN36s on previous cars, what other options would you recommend given that the car will be largely a road car but will be taken on the track?

3 I have read a fair few threads where wheels have had balancing issues, many modern tyre repair centres probably are not best option when having your new rubber fitted to freshly restored wheels. Any recommendations ? I live in Essex, southend area.

Thanks All

[yoda]

Hi Mark

On question 2, I recently switched from “normal” road tyres (Continental Premium Contact) to CN36 and while better, it wasn’t as big a difference as I was hoping. Think 10% better. I’ve had Avon’s before and they were quite a bit better performance wise but not as comfortable for touring use. I think it depends where on the scale you want to be but all are compromised in one way or another.

[Lightweight_911]

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Mark - you'll get as many recommendations/suggestions on this subject as replies !

It's very much a personal decision based on a number of factors including cost, appearance, performance, etc.

My own personal choice would be 185/70 & 215/60 Avon CR6ZZ - a combination I've used on a few different cars over the past 15 yrs or so - although never on a swb model.

You'll need to determine what the optimum size of spacer is required on the rear of your car in order for the tyres to clear the suspension.

The other question you'll have to contend with is that of 'tubes or tubeless' & I can only say that I've run deep sixes & 7R wheels without tubes for many years & never had a problem - I've always used TR415 'stubby' valves though & most of the wheels had not had any modification to the valve stem hole (on the inside of the wheel)>

As far asI'm aware you can't use tubes with tyres that have less than a 70% profile anyway ...

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[jonno1]

I switched from Vredestein Sprint Classics to the Avons and felt a noticeable improvement in overall performance and stability at speed. Shame they are so bloody expensive!

[inaglasshouse]

I've run both CR6ZZs and CN36s on LWB cars, in 185/70 front 215/60 rear. Both v good on the road. No reason to consider anything else, IMHO, unless you understandably baulk at the cost.
Based on wear so far it looks like the Avons are going to be much more expensive per mile, but haven't worn them out yet so can't be sure.

On my SWB car I have the original skinny wheels so not relevant to your interests, with Pirellis (I think - something decent and retro anyway). Lovely delicate feel, in conjunction with with the London bus sized steering wheel. But probably not the fastest way from A to B.

[PhilipB]

Even though you have 7” rears I would caution against putting big rubber on the back. You lose the pointy feel that makes the SWB a different drive to the LWB cars. 185/70 all round is plenty. The 7R will give you a bit more contact patch even with same size tyre. Avon is a better track tyre but the stiff side wall will mean it’s less comfortable on a bumpy B road than the CN36. Both look good to my eye.


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[Lightweight_911]

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Philip's suggestion makes a lot of sense ...

Porsche's recommendation for the 911R - on the rare occasion that it was equipped with road tyres - was to fit 185 tyres all round (albeit with 'full' profile back then - as opposed to 70%).

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[MarkIII]

Thanks for the feedback, so far it looks like Avons vs Pirelli and 185/70 all round vs 215/60s at the rear.

Any advice around my 3rd question around tyre fitting and balancing....

Thanks
Mark

[Lightweight_911]

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I think you need to ask that in a separate thread as that question has got 'buried' here.

It's more a case of finding an experienced 'sympathetic' tyre fitter in your area who takes extra care when fitting tyres to customers' (valuable) wheels.

.

[BILLY BEAN]

I would echo Philip in fitting 185 /70 all round. I ran Vredsteins ( a modestly priced option) on 7" and 6" wheels for a time. A 185 on a 7" can be a bit of a "stretch" but certainly doable. As Philip said you still get an increased contact patch on the 7" wheel.
Andy, has experience with using stubby valves in the earlier wheels, intended for a tubed tire, without issue. There is a long thread on early911sregistry about tubes or no tubes on early wheels. Darren65, I believe, had some early wheel valve holes modified to accept a standard rubber valve stem. My current Michelins 185/ 70, on a LWB 1970 car, are on Deep sixes have tubes in them. Whilst the ST clone runs TB 15s
( not relevant to you) on later rims but I have used bolt in valves which you might consider.
I am a Michelin fan but they are a pricey option.

[IanM]

Thanks for the feedback, so far it looks like Avons vs Pirelli and 185/70 all round vs 215/60s at the rear.

215/60 is too square for the SWB.

(albeit with 'full' profile back then - as opposed to 70%).

I didn't know that. Thanks. I think that would look really good

https://www.longstonetyres.co.uk/tyres/ ... n-xvs.html
https://www.longstonetyres.co.uk/tyres/ ... -ca67.html

[Darren65]

My own personal choice would be 185/70 & 215/60 Avon CR6ZZ - a combination I've used on a few different cars over the past 15 yrs or so - although never on a swb model.

Mark, I'm with Andy and this has been my choice for a few years now and the drive is epic.....although when I build my SWB I plan to try something different.....

....Harvey Weidman once commented that for a SWB running 6 and 7R's he felt the best look and ride was 175/70 fronts with 185/70 rears....this is what I plan to try and more in keeping with an early car imo.

Cheers,

[Darren65]

.....Based on wear so far it looks like the Avons are going to be much more expensive per mile, but haven't worn them out yet so can't be sure......

.....by a country mile but still my preferred choice!

[Darren65]

....found the quote (one of them)....

The largest tire that we put on the 7R SWB combo is 205/60X15. The 215/60X15s are too close (height-fender interference) for my recommendation. If you want more traction, I would suggest 175/70X15 and 185/70X15 in AVON for the SWB 6&7R set up. I have put on many of these and never heard anything but praise for them. Keep in mind a larger tire isn't always better traction if the compound is harder. For track use we usually put on 205/50X15 and 225/50X15 DOT C type. They are very close but can be made to work by clearancing the spring plate bolts....and some minor fender rolling if necessary. With the stiffer race suspension, this set up usually works well. HTH

[MarkIII]

....found the quote (one of them)....

The largest tire that we put on the 7R SWB combo is 205/60X15. The 215/60X15s are too close (height-fender interference) for my recommendation. If you want more traction, I would suggest 175/70X15 and 185/70X15 in AVON for the SWB 6&7R set up. I have put on many of these and never heard anything but praise for them. Keep in mind a larger tire isn't always better traction if the compound is harder. For track use we usually put on 205/50X15 and 225/50X15 DOT C type. They are very close but can be made to work by clearancing the spring plate bolts....and some minor fender rolling if necessary. With the stiffer race suspension, this set up usually works well. HTH

Thanks for passing on Harvey's recommendation, Avons back on the short list.