Guys, guys, guys… Using capitals can be read as bold or shouty, it all depends. To avoid confusion please note that the software allows for bold characters (B on the menu line). Let’s not get all upset about text formatting, ok?
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Never thought of that. But one could always swap a good tire to the rear and place the spare up front if that would keep same size tires on the rear. On the other hand, if you make sure the diameter of the spare is very close to the rest, it shouldn’t cause the posi any more issue than driving on a twisty road IMO.
I had composed a long response to this thread dealing with (a) “netiquette” and the use of capitals and (b) the law that I can find pertaining to tyres. The (a) section was, however, mildly (and deliberately) insulting to some listers so I deleted it. As for the tyre thing, I tried to find some, any, UK legal rules relating to tyres and their speed ratings, but apart from Type Approval (which applies only to manufacturers) and MOT test rules I can’t find anything that regulates the speed rating of any tyre that might be fitted to a car like my E-Type. One of the issues is that all E-types were manufactured before many of these rules came into effect. For example, in February 1967, when my E-Type was made, there were no type approval laws and there was no MOT test. And the tyre specified for my E-Type was a Dunlop RS5 - a cross ply no longer available. Its speed rating In 1967 is unknown but its most recently available equivalent was H rated or safe to sustained speeds of up to 130mph. There was also no speed limit on non-urban roads in Blighty in Feb 1967.
My tyres are safe for sustained to 130mph. My E is not capable of reaching, let alone sustaining, 130mph. And, of course, 130mph wouldn’t be legal on British roads, nor possible on a track such as Goodwood anyway. As far as I can tell, having looked, is no law telling me that it is illegal to use those tyres on my car on British roads, no matter what one might find repeated on this or any other forum.
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UK legislation on tyres:
Quote:
6. Each wheel on each axle shall be equipped with a tyre which has a load capacity such that when the axle is loaded to its maximum permitted axle weight, the weight transmitted to the road surface by that tyre does not exceed that load capacity.
7. The speed capability of all tyres fitted shall be not less than the maximum design speed of the vehicle.
Explanation of the UK rules:
Quote:
As previously discussed, indexes inform you of the maximum speed and load, respectively, that your tyres can take. For load indexes, you must use the minimum values given in the vehicle’s manual - as decided by the manufacturer. You cannot use a lower value.
As for the speed index, this must match the maximum speed of the vehicle, not the national speed limit of 70 mph. This means looking through the vehicle’s manual to find the official top speed and ensuring you have the subsequent matching tyres. For example, while any tyre with a tyre speed index over L (75 mph) is suitable for the purposes of driving under the national speed limit, if your vehicle has a top speed of 150 mph, than you would need tyres with a W (168 mph) rating or higher.
Having the wrong tyres, or just tyres under the accepted level of roadworthiness, can have a number of implications. First of all, if the police inspect your car, you could be fined or have the car towed. An officer can issue you a fixed penalty notice on the spot, or even make a case for prosecution. At the most, a defective tyre can cost you as much as £2,500 in fines and 3 points on your license.
However, these charges apply per tyre, so the penalties will stack if more than one tyre is against UK regulations. It is also worth noting that both the driver and the vehicle’s owner, if they are different people, can be summoned under this process.
Secondly, you will also have difficulty with your insurance company. Your insurance provider may argue that your car was not in the required standards to be on the road and, as such, is void from their policy.
The story in the US is the same but different. In historical times, there were no uniform speed or load ratings on tires, most were unrated. Federal law applies to new cars. But without even looking, I doubt that any federal law empowers a cop to ticket you for the wrong tires. but with 50 states, I’m not even going to attempt to figure out if local laws apply.
The question worth pondering is, what is the physical difference between V and W tires? I can’t find any reliable source on tire engineering, but some things seem obvious to me. The primary characteristic needed for high speed isn’t handling. It’s resistance to heat. I would expect that the higher speed tire would be made of harder compounds, not softer. And that construction would be lighter, not heavier. That the sidewalls would be designed to be less flexible, not more. And before you cite some source that says otherwise, please filter out handwavers, tire salesmen, and pompous speculators.
I suspect that picking a higher speed tire than required is like picking a racing brake pad…it will work wonderfully at high track speeds, but that isn’t necessarily the case in normal driving, where it can’t heat up proper;ly. Not everything that works on the track makes sense for the street. These speed ratings became an issue after the Ford Explorer scandal, where overloaded tires tended to come apart in very hot climates.
Yes, tyres with low speed ratings flex and squirm under pressure, causing heat build-up. Tyres with higher speed ratings are better equipped to get rid of heat, in part because they generally have higher quality construction and ply - hence the cost. Excess heat risks tyre degradation, reduced traction and blowouts.
Tests have shown a V rated tyre came to a stop in 115 feet from 50mph whilst an S rated tyre stopped in 128 feet. Similarly cornering and steering feel are affected due to the flex in sidewalls.
Mike
This is one of the best sources of information on tyre design.
It does run to about 600 pages but covers everything. ‘Tire Technology’ by F J Kovac, Goodyear Tire & Rubber Company 1978 is much more concise but only available in hardcopy (if you can find one).
David
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That’s what I do. I have 6" rims on my E-Type(s), but only 5" for the spare so that I can still fit comfortably under the floor board. As a result, I use a narrower tyre on the spare, and compensate by using a slightly higher aspect ratio so that the diameter is well matched to the other 4.
I’ve decided to go with the V rated Vreds once they are back in stock. Even at a treadwear of 220, I’ll never wear them out. Would rather have the grip
Sorry Larry- I think I got some of the last ones in the US…
4 new 6"x15" wheels and one original 5" wheel for the spare.
February is soon enough for me. After all these are summer tires and we are in winter where I am. 
Hi David Sorry to be so long in answering. I’ve spent the last few days looking at performance tires for 15’ wheels. There just isn’t anything I could find other than the Avons. More than 10 years ago I had found the supply had pretty much dried up, and it hasn’t changed. I moved up to both 16 and 17" Daytons to resolve the problem. The issue is primarily one of rolling diameter. Stock is 26.5" and in order to get a modern low profile 15 inch tire that is close to this the tire (not tread) width is too much for an E Type.
I highly recommend the Avon 205/70 - 15 CR6ZZ - it’s very high performance, will fit and look a normal size. and while probably not faster than a Hoosier it will be very close. I’ve got several friends that installed them on their E Types and picked up 2 - 3 seconds in JCNA slaloms. One now has them on his Mk 10, of all things and finds them fine in wet weather, (He lives in Vancouver B.C.) as they do have tread. They are not commonly available. In the US the supplier is: http://rogerkrausracing.com/pdfpricing/Avon%20CR6ZZ%202021.pdf
They are also available in a greater range of sizes at Longstone’s in England https://www.longstonetyres.co.uk/vintage-tyres/avon-cr6zz.html
The 205/70 -15 is a natural fit. The 225/60 - 15 would probably fit if you remove the bump stop brackets, but is 1" smaller in diameter than stock - probably not too noticable.
As I assume you’ve noticed you can’t get a tire that is wider than a 185 /80 -15 to fit under the board in the boot of an e Type.
My 205/70-15 Dunlop spare on a 5" wheel fits with no problem. That’s on a FHC, I don’t know about in the boot of an OTS. I’ve got the same tires on 6" Dayton wheels on the car but I’ve not tried to to see how they fit in the boot.
Hmm That’s interesting - they don’t fit in mine - it’s not by much, but enough that the board won’t quite fit.
Thank you for the detective work Terry. I didn’t find much in my hunting.
As far as spares - yes I am aware of the difficulty fitting over size tires in the boot.
Both a 1970 vintage 205x70 x15 Michelin on 5" nor a 205x65x15 modern Bridestone on 6" rim fit.
Well I thought the Vredesteins were expensive. The Avons have given me perspective on that notion! Thanks again for digging into this.
Dave A
I’ve run 225-60 15’s. They just barely clear the rear if you cut away the bump stops. On the front, you get a slight touch on the mudguard at extreme lock, in compression. They run well, but the big issue is steering effort. I’m currently running 215-60’s which fit the wells, but lower the car almost 3/4 inch. It seemed like a good idea at the time is all I’ll say.
I just finished swapping speedometer gears for 185R15 Vredestein’s, but now they’re out of stock until September. Avon is available from Coker, but at $331 per, plus shipping and installation, far too expensive. And if that’s not enough, they have Dunlops for $355. I’m liking the look of redline Cokers, but I suspect it’s not a good tire.
All the sticky tires at Tire Rack have a circumference that will reduce overall gearing. Fun if you’re autocrossing but…been there done that… I like the longer legs a tall tire buys you.
Like you Mike, I like the fuller look of a 205 or bigger. I find the steering effort increased but not awful. I’d buy the Bridestone Pole position Potenza again but they’re no longer made.
Its looking like the Vreds make the most sense to me. The Avons Terry suggested are are kind of pricey. Pirelli 6000’s $300 a piece at T.R.
130 mph Vred’s are about $150 in stock now / 149 mph in March at $172. / 168 mph at $158 available now. I am not sure how to choose between the Vredestein 185 size tires.
The “130” and “168” are 70 series. the “149” is the stock 82 profile.
Good info Mike. Thanks. Do you have a suggestion as to which Vred to buy?
With 3.07 gear the 168 mph@ $158 tire looks good to me.
I’ll have to find a long and very wide runway
What TPM is noted on the face of your speedometer? Your speedometer is going to be reading high, and the car will sit low.