Front Tyre/Tire - Avon

Malcolm · 01-08-07, 12:15 PM

I have just been called by Avon to discuss a front tyre to match the 295 and 275 rear tyres that they now make. I beleive the rear tyres have gone down well with users both in the UK and overseas so now is the time to make YOUR contribution to the effort to get a sensible sized front tyre.

Before we progress further please note I am a GTD owner and my main perspective is as such. However I do have some knowledge of other makes but my bias is towards sorting a tyre for my car!

The rear sizes we are trying to get a partner for are 275/55/15 and 295/50/15. The compounds for the front will be matching to these rear tyres and they will be similarly VR rated (at least that is my expectation right now!).

There seem to be two sizes to choose between. These are 225/60/15 and 235/55/15. The rolling diameter is about 640mm or 25.2 inches. This correlates pretty much to the rolling diameter of the current suggested front tyre from Avon namely 215/60/15. Manufacturing tolerances will always tweak these numbers in some direction, just a fact of life!

I beleive both these sizes will fit a GTD front wheel arch without fouling in steering lock and in bump. Do you agree? Do say so if you don't! Will these sizes fit other makes of replica? I would be surprised if they did not but please say what you think.

We are in competition on this! The cobra boys have also been contacted for their input and understandibly, they have their own agenda. It is up to us to come up with a generic size that suits us that will actually also suit them. Avon will not make tyres for each camp.

If you run 16 inch rims, this still can benefit you as Avon have said they are thinking about using the same moulds to make the same rolling diamter but with 16 inch holes in the centre. This affects MDA and RF customers I think.

Overall timescale on this is minimum 6 months.

Please post your thoughts here.

Many thanks

Martin · 01-08-07, 02:56 PM

Hi Malcolm,
I am a new member to the forum and quite close to you geographically I think.
I am in a dilema regarding tyres!
I will be taking delivery of a new MDA rolling chassis within the next few months and I wish to procure my wheels and tyres and have them fitted before delivery so I can wheel the car around.
One of the biggest decisions is 15" or 17" wheels. I really want 15" wheels for originality but am put off by tyre availability.
My car will be a Mk1 with Gulf arches, therefore 12" wide rear wheels.
Looking on the Avon website, I notice that the 295/50 R15 tyres are recommended for Max 10.5" rims although they have a section of 12.2". I really want to fill the arches and started to look at the Pirelli Pzero 345/35 ZR15 and the Michelin TB 335/35 R15. My concern is that the diameter is around 620mm for these as opposed to 683mm for the Avons and they may look too skinny on the side walls ? If anyone has them fitted, I'd be very interested to see some pics.
Also, apart from pirelli, who do a 225/50 ZR15 tyre, neither Avon or Michelin seem to do a corresponding front for a GT40 with 15" rims (I think 215's are too small ?) so I would be very interested in the upcoming Avon tyre, either 225's or 235's. I will need to check for clearance on an MDA but my preferance would be for the 235's.
If the new Avon tyre becomes the front of choice, could I mix and match michelin/pirelli rears ? Does anyone know how close the compound/tread patterns are on these to the Avons ?

I have asked Mark at MDA for his recommendations, but if anyone else has any thoughts on the suitability of Avons/Pirelli's or michelins for the rear of a Gulf arched Mk1, then I would be very glad to hear from you.

Many thanks,

Malcolm · 01-09-07, 08:28 AM

Don't mix and match these tyres you mention above. They have quite different grip levels/compounds/water dispersement properties. I do not beleive anyone makes the rear tyre you are looking for ie bloody wide and road legal in the UK and that looks right. The Michelins I have seen and to me look like a road legal racing wet! But diameter is tiny and would look really daft. IMHO of course!!!! I considerd them prior to working on Avon but rejected them. Sized all wrong.

If you really want the 12 inch tread width then I think you will have to go to 17 inch rims for road legal rubber in UK. However I think that a 15 inch rim is the right size for our cars and to then have the wheel off set correct to fill the arch. Visually I think that is a better compromise than to have 17 inch rims.

If you want to come and have a look at my car with the 295 Avons, feel free to contact me.

Canuk40 · 01-09-07, 12:09 PM

Hi Malcolm,

Tires are very important to our beloved GT40s and a reliable source of proper sized high speed rated road tires should be on the top of the adgenda for any enthusiast and all manufacturers.

Avon is certainly doing us a tremendous favour by supplying rear tires that fit both Cobra and GT40 applications. The fronts on the Cobras I understand are meant to be the same diameter as the rears, however the GT40 fronts should be as close to 25.0" diameter as possible.

A 225/50/15 is an available size (Dunlop, Pirelli Pzero) that is smaller than ideal although quite wide. A 235/50/15 would be perfect and allow for the continued trend towards putting the widest rubber possible on the car.

A 215 wide tire of any aspect ratio is narrower and therefore less appealing. Also maintaining a low ride height on increased front tire diameters (26.0 +)has an adverse effect on camber rates, roll center height, sway bar rate and weight transfer in cornering.

So if Avon is offering 215/60 vs 235/55 cast my vote for the 235. You can only corner or brake as the capability of the smallest tire permits.

By the end of the sixties JWA cars were running 10" wide front wheels, rears from 12>14". Most new GT40 replicas built from now on will have 8" front and 10" rear rim widths minimum, so lets make it easy for Avon to get on with it. My hats off to them. Where do I order?

With regards to fittment issues on some cars for 235 fronts, isn't it worth messing around with offsets or new wheels to be able to put a complete set of high speed, matching compound/tread DOT approved tires on the car than the current situation of mismatched all of the above.

Thanks for your efforts in this matter.

Cheers

Canuk40 · 01-09-07, 12:26 PM

Hi Martin,

About the Pirelli PZero 345/50/15s. They are smaller yes, but fit well and are seriously wide. Here's a pic of one in our shop. The fronts will be 225/50/15 PZero to keep it all in the family.

The black CAV GT with the 345s has a 347 Ford Racing crate engine, Webers and RBT 6speed. Mathmatical top speed over 230mph at 6000rpm so comfortable highway cruising will be no problem

.

This car will also be Right Hand Drive, Right Hand Shift and is being fitted with our latest RHD shift mechanism. Nothing to do with tires, but it's going to be a very cool car.

Cheers

Martin · 01-09-07, 01:13 PM

Many Thanks for the replies,

The Cav with the 345 pirellis looks a beast. I really wanted to see what the 345's would look like on a GT40 so thank you for that.
I will leave Malcolms thread alone now and let others answer him regarding the Avon tyre sizes.
235's would be my choice also for the fronts.

Last thing if you don't mind,
How does the reduced height of the tyre (Pirelli 345's) affect geometry, steering, anything else I haven't thought of ?
Are there any issues at all with running a tyre with a diameter of 625mm rather than 670mm ? I am refering to the matching front pirelli 225/50's as well.

Sounds like Malcolm is doing a great job for all GT40 owners negotiating with Avon. Many thanks.

Fran Hall RCR · 01-09-07, 01:32 PM

I agree the tyres are the toughest part of the equation and thanks to Malcolms hard work we should be good to go...

Nice rear wheels Ian....

Malcolm · 01-09-07, 02:13 PM

Fran, does RCR have a preference on size? Manufacturer input is the best we can give Avon = more potential sales! Wonder if Ron's Lola can run these tyres?

Fran Hall RCR · 01-09-07, 02:34 PM

Malcolm ,
does Avon already offer the 215 size and is the other size a sister to the 215 or instead of the 215???

Pantera1889 · 01-09-07, 04:30 PM

Quote:

Originally Posted by Canuk40

Hi Martin,

The black CAV GT with the 345s has a 347 Ford Racing crate engine, Webers and RBT 6speed. Mathmatical top speed over 230mph at 6000rpm so comfortable highway cruising will be no problem

.

This car will also be Right Hand Drive, Right Hand Shift and is being fitted with our latest RHD shift mechanism. Nothing to do with tires, but it's going to be a very cool car.

Cheers

MORE PICTURES!!!!

Malcolm · 01-10-07, 04:25 AM

Quote:

Originally Posted by gt40fran

Malcolm ,
does Avon already offer the 215 size and is the other size a sister to the 215 or instead of the 215???

The 215 60 15 is an existing tyre from Avon and they will carry on producing it as far as I am aware. These new sizes should be coming from a new mould.

Mike Drew · 01-10-07, 11:05 AM

Quote:

Originally Posted by Canuk40

Hi Martin,

About the Pirelli PZero 345/50/15s. They are smaller yes, but fit well and are seriously wide. Here's a pic of one in our shop. The fronts will be 225/50/15 PZero to keep it all in the family.

Just a point of clarification--the rear tire size is actually 345/35-15, not 345/50-15. They are a good match size-wise with a 225 or 245/50-15 for the front.

Last time I checked only Dunlop was making the 245/50-15 in their SP8000 line.

Tim Kay · 01-10-07, 11:38 AM

Just curious why not many of you in the U.S. are using or considering the Hoosiers?
245/50zr-15 and 275/50zr-15 (stamped DOT)

I've run Hoosiers for about 8,000 mi and love 'em

Malcolm · 01-10-07, 03:40 PM

Certainly the hoosier is an option in US as it is road legal I beleive. I know they are used here in UK on track only cars and they give good grip in the dry. The 245 50 15 is very tight on fitment for a front tyre and on a GTD is likely to damage the inner wheel arch bodywork. Goodrich used to make a ZR1 in this size. Ran 52 laps on the Brands Hatch GP circuit in one day on these and that was a hoot, sharing my car with Robin Batt. First time either of us had killed a new set of road tyres in one day!

At least in the US you have more options to consider.

Canuk40 · 02-06-07, 12:57 AM

Hi Ron, Martin,

Here's a couple more pics of the 345 PZero on our customer Gulf body CAV GT. We were checking fit with revised lower control arms incorporating new geometry to suit the rubber.

The front suspension will be done shortly, does not change the wheelbase or track, just everything else, it will be a "must have mod" for anyone looking to track a pre 100 CAV. Stay tuned

Cheers

CliffBeer · 02-06-07, 02:33 AM

Us yankees on this side of the pond probably have it more difficult than those on the other side - when I checked with Avon about two months ago to see if they were going to distribute the 295 and the 275 rear tires in the US they said they had no plans to do so and these tires would not be available through any dealer in the US. Bummer. Does anyone know if this has changed?

Sorry in advance for the thread wander above....now, getting to the original question... Many CAVs came stock with a 225/60/15 BF Goodrich TA with no clearance issues, although, it is close as a couple of times there has been just a touch of rubbing on the wheel well. I suspect a 235/55 would probably fit fine - as good as the 225/60 anyway - and provide a little better lateral traction up front. The stock 60 series tire is nice on a bumpy road, but, not a great peforming tire for track work or really spirited driving. So, yes, please, Avon bring it on, and, in the US!