Tyre Advice

[Kevo_6]

1 hour ago, Keith Warren said:

As I understand the TR6 could have had either Dunlop SP Sports or the XAS tyres my Heritage Certificate from a CP 1972 stated Dunlop.

Keith

+1

[Trumpy]

I hadn’t thought of looking at my heritage certificate and it does specify  . Dunlop sp41 tyres . A quick google and the Dunlop tread pattern matches the tyres in the photo so not cross plys. 
I always wondered why the original owner paid extra for wired wheels but hadn’t had radial tyres fitted ! Now I know he did . 
 

[jimt]

On 1/9/2025 at 11:30 AM, jimt said:

On the USA cars was the suspension set up or spring ratings any different to the U.K. spec cars? 

 

On 1/9/2025 at 2:09 PM, DRD said:

Not as far as I'm aware!

I thought I’d read somewhere that different sized tyres to the U.K. spec cars were fitted to the US cars - is this correct &  if so why?

[DRD]

57 minutes ago, jimt said:

 

I thought I’d read somewhere that different sized tyres to the U.K. spec cars were fitted to the US cars - is this correct &  if so why?

Yes the US cars had 185 80 r15 size tyres and a 3.7:1 diff as opposed to 165 80 r15 tyres and a 3.45 diff for UK cars.

Not sure why there was a difference though?

[Dave McDonald]

1 hour ago, DRD said:

Yes the US cars had 185 80 r15 size tyres and a 3.7:1 diff as opposed to 165 80 r15 tyres and a 3.45 diff for UK cars.

Not sure why there was a difference though?

I’ve always assumed the difference was because the USA had almost universal low speed limits, so top speed was less of a requirement. The lower diff ratio would not over Rev the engine at lower speeds but would give quicker acceleration. 
Dave McD

 

[stuart]

2 hours ago, Dave McDonald said:

I’ve always assumed the difference was because the USA had almost universal low speed limits, so top speed was less of a requirement. The lower diff ratio would not over Rev the engine at lower speeds but would give quicker acceleration. 
Dave McD

 

No more to cope with the lack of power on the smogged carburated engines. 
Stuart. 

[jimt]

Thanks chaps - But those replies don’t explain why the different tyres were specified - or am I missing something? 
 

Lower diff ratio =  better relative acceleration etc makes sense - so did this also require a different rolling circumference from the tyre to enhance this further? (assuming the 185/80 has a greater overall circumference)

- and how would this have affected the accuracy of the Speedo- or were the American speedos calibrated differently to suit?

[John Morrison]

Speedos were different, but I was told the biggest reason was two fold.

The USA liked a more comfy ride, and didn't like overdrives, hence the more cushioned 185 x 15

and few O/D coming back with re-imported cars. You need to remember that 90% plus of

TR's went to N America when new, so they got what they wanted.

John.

[Jonny TR6]

Slightly off topic but on topic..

My XASs are supposed to be tubed, but I’d had them fitted without tubes. A couple are now losing air, so I’ve got some tubes on the way.

Question is, can I fit the tube without having to lever the tyre over the rim ? The wheels have been painted and I’ve already had one wheel finish get damaged by the tyre fitters when having the tyres fitted, necessitating a repaint, so would like to avoid that happening again.

If I can do it in the garage that would be ideal.

[jimt]

13 hours ago, John Morrison said:

Speedos were different, but I was told the biggest reason was two fold.

The USA liked a more comfy ride, and didn't like overdrives, hence the more cushioned 185 x 15

and few O/D coming back with re-imported cars. You need to remember that 90% plus of

TR's went to N America when new, so they got what they wanted.

John.

Anyone fitted the 185/80’s to a U.K. car?- if so what’s the verdict?  Is there any reason not to ? Are they a good compromise between the 165/80 and the 195/65 - especially with our poor road surfaces etc

Jim 
 

Edited January 20 by jimt

[DRD]

1 hour ago, jimt said:

Anyone fitted the 185/80’s to a U.K. car?- if so what’s the verdict?  Is there any reason not to ? Are they a good compromise between the 165/80 and the 195/65 - especially with our poor road surfaces etc

Jim 
 

Unless you get it recalibrated your speedo will under read by 5%.

[stuart]

14 hours ago, Jonny TR6 said:

Slightly off topic but on topic..

My XASs are supposed to be tubed, but I’d had them fitted without tubes. A couple are now losing air, so I’ve got some tubes on the way.

Question is, can I fit the tube without having to lever the tyre over the rim ? The wheels have been painted and I’ve already had one wheel finish get damaged by the tyre fitters when having the tyres fitted, necessitating a repaint, so would like to avoid that happening again.

If I can do it in the garage that would be ideal.

Not really as you need to have enough access to get the inner tube in and the valve in place so one wall of the tyre needs to come out over the rim and the tyre needs to be fully loosened off the other side of the rim, good tyre places have insulated breaker machines that shouldnt damage the paint.

Stuart.

[Hamish]

If you go tubes I’d fit ferrules

To protect the valve stems

[Jonny TR6]

Thanks for the advice chaps

[jimt]

On 1/20/2025 at 8:07 AM, jimt said:

Anyone fitted the 185/80’s to a U.K. car?- if so what’s the verdict?  Is there any reason not to ? Are they a good compromise between the 165/80 and the 195/65 - especially with our poor road surfaces etc

Jim 
 

 

On 1/20/2025 at 9:46 AM, DRD said:

Unless you get it recalibrated your speedo will under read by 5%.

One way to keep the mileage down 

[dougal]

On 1/10/2025 at 9:12 PM, Trumpy said:

Did the Tr6 come with Michelin tyres as standard ?  I ask as a picture taken of my car when it was new appears to show crossplys.  Admittedly it’s a Tr5 so a year or two older ( yeh, i know I’m in the wrong forum  ) but I’m surprised Triumph supplied their new 150hp roadster on poor tyres . 
It had worn but Michelin XAS on when I bought it but being on a tight budget I replaced them with much cheaper Dimax classic 185/70 s . They have period looks and shape  and four years in are performing well . 
pics to show old and new 

 

I'm sorry to hear about your choice of tyre, however i understand the money thing can be obstructive. However there is absolutley nothing about that tyre that looks in any way anything like a classic tyre. tread pattern, shape, have nothing to do with classic tyres. and the side wall is completely riculous. It is just a budget tyre with the word classic written on the side so everyone knows that it definately isn't a classic tyre. I'm afraid the carcass structure, which is the important thing when selecting a tyre to suit a car is nothing like what you want either.

this tyre test will show you what the performance is like

https://www.longstone.com/images/tire-test/auto-bild-klassik-e-type-jaguar-tyre-test-english-final.pdf

 

The SP 41 tyre was an early Dunlopp stab at radial tyres, and they pretty much just recycled the current crossply tread pattern. They weren't however very good. Jaguar at the time were considering fitting radials the the MK2 saloon and E-Type, but they stuck with crossply because they were sort of tied in with Dunlop and couldn't move onto the Cinturato. There were in house Jaguar bulletins discussing tyre pressures determined by crossply or radial or crossply and they say if you are fitting the Dunlop SP41 then you need to restrict the speed of the car which you didnt need to do with the Pirelli.

 

s-l1600.webp

 

[dougal]

On 1/20/2025 at 12:28 PM, Hamish said:

If you go tubes I’d fit ferrules

To protect the valve stems

Hi

Those ferruls are to make an inner tube OK on an odd phenomina of wheel. At one point the decided they wanted a wider valve stem. This was called a TR15. the current normal valve stem is called a TR13. If you have a modern tube with a TR13 valve stem and you want to fit it into a wheel that has a hole the size of the TR15 valve stem, that is when you fit this ferrul.

we sell them too.

https://www.longstonetyres.co.uk/tyres/165-15.html

 

and by the way Micheolin just make the best tubes. fit and forget.

 

 

[Jonny TR6]

1 hour ago, dougal said:

Hi

Those ferruls are to make an inner tube OK on an odd phenomina of wheel. At one point the decided they wanted a wider valve stem. This was called a TR15. the current normal valve stem is called a TR13. If you have a modern tube with a TR13 valve stem and you want to fit it into a wheel that has a hole the size of the TR15 valve stem, that is when you fit this ferrul.

we sell them too.

https://www.longstonetyres.co.uk/tyres/165-15.html

 

and by the way Micheolin just make the best tubes. fit and forget.

 

 

Thanks Dougal - so a standard TR6 steelie is TR13 and I don't need the ferrules ? My '65 VW Splitscreen has taxi valve stems (tubeless) so I assume they're TR15 ?

I do like a good education piece !

[John Morrison]

Yes and yes.

John

[Trumpy]

On 1/22/2025 at 3:03 PM, dougal said:

I'm sorry to hear about your choice of tyre, however i understand the money thing can be obstructive. However there is absolutley nothing about that tyre that looks in any way anything like a classic tyre. tread pattern, shape, have nothing to do with classic tyres. and the side wall is completely riculous. It is just a budget tyre with the word classic written on the side so everyone knows that it definately isn't a classic tyre. I'm afraid the carcass structure, which is the important thing when selecting a tyre to suit a car is nothing like what you want either.

this tyre test will show you what the performance is like

https://www.longstone.com/images/tire-test/auto-bild-klassik-e-type-jaguar-tyre-test-english-final.pdf

 

The SP 41 tyre was an early Dunlopp stab at radial tyres, and they pretty much just recycled the current crossply tread pattern. They weren't however very good. Jaguar at the time were considering fitting radials the the MK2 saloon and E-Type, but they stuck with crossply because they were sort of tied in with Dunlop and couldn't move onto the Cinturato. There were in house Jaguar bulletins discussing tyre pressures determined by crossply or radial or crossply and they say if you are fitting the Dunlop SP41 then you need to restrict the speed of the car which you didnt need to do with the Pirelli.

 

s-l1600.webp 97.37 kB · 1 download

 

 

i hang my head in shame !

Although in my defence i think they do look period (although maybe not to your trained eyes ) and to be fair the car does ride nicely on them and handles well .   No track days though ! 

 I see test shows serious short comings in the wet which may well have put me off had i seen this before purchasing , dry performance quite reasonable though. I guess you get what you pay for to some extent , the set of 4 cost less than 1 Michelin  .   I'll have to up my budget , like folk say you soon forget the cost (but your wife remembers ! )   

If my next post is regarding pulling a tr5 out of a ditch you will be entitled to say 'i told you so' .       

[Steve-B]

I'm finally getting ready to go buy tyres after months of dithering. I am finding a number of tyres seem to show inner tubes on the same page as the tyres. So do tyres like the Michellin-XAS, Pirelli-Centurato and Vredstein-Classic all require tubes? Or is this just a way to make the overall tyre more robust?

Asking as I have a roadsire tyre repair kit I've only had to use a couple of times, but if a tube is involved, you've gotta rely on a spare, or recovery.

[DRD]

4 minutes ago, Steve-B said:

I'm finally getting ready to go buy tyres after months of dithering. I am finding a number of tyres seem to show inner tubes on the same page as the tyres. So do tyres like the Michellin-XAS, Pirelli-Centurato and Vredstein-Classic all require tubes? Or is this just a way to make the overall tyre more robust?

Asking as I have a roadsire tyre repair kit I've only had to use a couple of times, but if a tube is involved, you've gotta rely on a spare, or recovery.

I think you only need inner tubes if you have wire wheels.

[RobH]

26 minutes ago, DRD said:

I think you only need inner tubes if you have wire wheels.

Unless the tyres are described as tubed type, it is the wheels rather than the tyres which determine whether inner tubes are required.   Wheels for tubeless use have two humps in the rim which are supposed to hold the tyre in place in the event of e.g. nudging a kerb at speed, which otherwise could result in deforming the tyre wall  enough to cause deflation.  The original steel wheels on at least the early TRs do not have this feature so really should be used with tubes.    That goes for wire wheels also since the air exits via the spoke holes.   Modern wires are sold as tubeless since they have a coating over the spoke nipples but even so it is probably safer to use tubes anyway. 

You don't need tubes on alloy wheels made for tubeless tyres. 

 

 

Edited January 24 by RobH

[jimt]

On 1/22/2025 at 3:03 PM, dougal said:

 

this tyre test will show you what the performance is like

https://www.longstone.com/images/tire-test/auto-bild-klassik-e-type-jaguar-tyre-test-english-final.pdf

 

 

 

Looking at that I wouldn’t be happy with the performance  (in the wet & dry handling)  of the Michelin or Dunlop either - both toward the bottom of the list overall . Pirelli for best overall performance  it seems - which I’m happy with as the 6 I acquired last year came with Pirelli’s 

[Jonny TR6]

My local tyre place say they won’t fit the tubes as their tyre machine is too powerful and likely to crush the wheels.

First I’ve heard of that being a thing.

Trying another place on Monday with strict instructions to handle with care. They’re newly painted and handily the painter is 500yds up the road from them in case they screw it ip.