Tyre advice please

[Markvsandford]

Hi all,
I apologise in advance for what is probably a stupid question.
My stag has Bridgestone sf 228s, 185 R14 90T on it. The side walls are showing cracks, so it is time to replace.
I was looking for the same size, but struggling to find some, I checked the handbook, which says 185/70 R14. It has the standard 5 spoke alloys on it.
My local garage recommended Hankook optimal K 715 - but after searching on-line and reading through the forum here, they seem to come in 80, not 90. Is that going to affect the look of the car much? Were the bridge stones the wrong size to begin with?
I am in Denmark, so don't have quite so much choice, are these Hankooks ok? can't get passed the name! Should i be looking for something else?
thanks
Mark

[TR5convalescent]

Hi Mark. There are lots of threads about tyres on the forum. Unless your speedo has been calibrated to suit the tyres you currently have I think it is already inaccurate. Somewhere on the web there used to be a tyre comparison size chart which would tell you how much +/- your speedo would be out, but I can’t seem to locate it.

Other members use Hankook and like them. Some swear by Vredestein. I’m using Dunlop 195/65 on the standard wheel and reckon my speedo reads about +2mph at 30 and about +8-9mph at 70.

[davidf]

Mark - are you confusing the load rating (90 in the first example) with the profile ( /70 in the second example). The original tyres were mostly 185 R14 90H (with some 175 R14 90H on later Stags). There was no given profile but it was /80 by default.
As far as I can research, the only tyres in the original size, load and speed rating, are Vredestein. T rated are lower speed than the original H (118 vs 130 mph). If fitted, you should at least get the approval of your insurer.

[PJB]

I have had a set of 205/70 14 Toyo's fitted today

Tyre comp https://tiresize.com/comparison/

Original 185/80 14 toyo as above
25.7 25.3 diameter
7.3 8.1 width
5.8 5.6 sidewall
80.6 79.4 circumference
787 798 revolutions/mile


as near as dam it given speedo wobbles and inaccuracy.

[DJT]

Somewhere on the web there used to be a tyre comparison size chart which would tell you how much +/- your speedo would be out, but I can’t seem to locate it.

http://www.tyresave.co.uk/tyre-size-calculator/

[Markvsandford]

Hi,

Thanks for the replies. I probably am confusing the load rating with the profile. The lack of the profile number was confusing me. So if i read this correctly, chances are the tyres i have are 80 profile? I will measure to double check.

The car has a Rover V8 in, with a new speedo - and i am pretty sure the tyres pre-date the engine. It has an ECU fitted, and has been on a rolling road, so i assume all was calibrated correctly for the tyres it has.

I want to order these from the UK and get them fitted locally, so want to be sure they are correct!

thanks again for all the help

Mark

[davidf]

Also check local laws concerning using T rated tyres where H were originally specified. In the UK, it 'seems' to be legal (that is, I have never seen any discussion about it not being), although it is said that an insurance company could reject a claim, and therefore declare you uninsured, which is illegal. However, a number of owners have reported informing their insurance company, and being approved.
Personally, I am not comfortable fitting tyres with a lower rating than originally specified (although I have not exceeded 118mph - honestly officer).

[Stag About Town]

Also check local laws concerning using T rated tyres where H were originally specified. In the UK, it 'seems' to be legal (that is, I have never seen any discussion about it not being), although it is said that an insurance company could reject a claim, and therefore declare you uninsured, which is illegal. However, a number of owners have reported informing their insurance company, and being approved.
Personally, I am not comfortable fitting tyres with a lower rating than originally specified (although I have not exceeded 118mph - honestly officer).

The speed rating (always read in conjunction with the load index) refers to the speed the car was declared capable of by the manufacturer, not what you may or may not actually do. At the time of the Stag T rating did not exist so H was the only legal option. Although most insurers seem happy with T , as has been said elsewhere it is still a grey area. For cars originally fitted with 175HR14 the best option is either same again or 19570HR14 (Khumo is a good choice here) For those originally 185HR14 the options are less obvious so a compromise may be needed. The tyre size comparison charts are good but in my opinion much more than 195 section width on standard Stag wheels is too much.

[Andy S]

Surely having changed the engine to a RV8 means the car is already modified and so choosing a different tyre is not that bigger deal to declare.

I have 185 80 14 tyres fitted, but will probably choose 205 70 14 tyres next time. They’re more widely available and fill the arches well.

Andy S

[dasadrew]

...
I am in Denmark, so don't have quite so much choice, are these Hankooks ok? can't get passed the name! Should i be looking for something else?
thanks
Mark

Hi Mark,

it's of course up to you where you buy or have fitted, but if Denmark doesn't have many tyres for sale, have you considered maybe ordering via a company like https://www.reifendirekt.de/cgi-bin/...&homologation= and then choosing one of their associated tyre dealers in Flensburg where you have the tyres delivered there and fitted (about 120km drive from where you are). They'll dispose of the old tyres too.

I must admit to having had poor experience when separating the tyre purchase company from the tyre fitting company if a problem occurs!

Just a thought...

Drew

PS: if you consider your tyres unsafe for road use, then forget this thought!

[davidf]

Back to the original post, Mark says "checked the handbook, which says 185/70 R14"
I don't think I have a copy of an original handbook; can anyone else confirm this? I have noticed that the Haynes manual says this, but do any Triumph documents?

Ok, just checked the ROM (Issue 2, 1973) - In section 4 (General specification) it says Goodyear G800 185/70 HR-14 or Michelin XAS 185 HR-14. In section 74 (Wheels and tyres), it says 185 HR-14 (change to 175 HR-14 if fitting snow chains).
Do I remember reading somewhere that the Goodyear were only fitted if Michelin were un-available? Does this mean that some Stags left the factory with speedometers wrongly calibrated?
Also, at this time, no load rating was indicated (and speed rating was before the 'R'). When did load ratings come into use? Are there later Triumph documents with Load rating?
I have found a document from British Tyre Manufacturers’ Association which makes two statements
1 In most European countries the speed symbol of replacement tyres must by law be equal to or higher than the original fit tyres. (DF comment - That should be checked by continental owners, and could cause problems for UK owners for Continental touring if T are fitted.)
2 UK law does stipulate replacement tyres must have a Load Index equal to or higher than the original fit tyre.

So, it would be important to find if the Load rating was ever specified by Triumph. Many of our threads have talked about a 90 load rating; If this was specified by Triumph, fitting less (such as 88) would be illegal.

[DJT]

Do I remember reading somewhere that the Goodyear were only fitted if Michelin were un-available?

David,

According to James Taylor in The Original Triumph Stag, Restorers Guide, "The original tyres for all markets except the USA up to January 1973 were 185HR14 Michelin XAS tubeless radials; thereafter, Avon tubeless radials of the same size were also fitted. In March 1973 approximately, a batch of 30 UK-market cars was fitted with the Goodyear G800 Grand Prix 185/70HR14 tyres normally fitted only on Federal Stags. This appears to have been an emergency measure to overcome a shortfall in supplies."

It is also documented that during the last year of production 175HR14 tyres were fitted.

[davidf]

OK, Dave, thanks for that update - that makes sense in relation to the information in the ROM.
Do we have any original information about the load rating - we currently seem to think that it should be 90, but there are more options if we go for 88. Taking into account :- "UK law does stipulate replacement tyres must have a Load Index equal to or higher than the original fit tyre" - I don't know when Load ratings started being part of a tyre's specification, or whether Triumph ever gave a rating for the Stag.

[dasadrew]

Thanks to Klaus Schlueter, I have a copy of the original Stag Homologation paper for the German market.

The maximum front axle load is 830kg
The maximum rear axle load is 885kg

At least in Germany (and, as there is no speed limit in some places here, I would think it's good enough for other places!) the tyre load rating may not be less than half the maximum axle load.

So the tyre load rating for the front axle is 415kg (Load Index 78)
and the tyre load rating for the rear axle 443kg (Load Index 80)

Drew

[davidf]

Thanks Drew - that tells us what would be fitted according to today's calculations.

But the Uk law (apparently) says replacement tyres must have a Load Index equal to or higher than the original fit tyre. I am curious to know if there ever was an original fit tyre with a load rating, and if so, what was it.

Further research shows that current Michelin XAS, in either 175 or 185/70 size, have load rating of 88. I wonder if that is the same as when fitted in the 70's?