The Triumph Dolomite Club - Discussion Forum

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PostPosted: Tue Nov 19, 2019 10:19 am 
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It is a mistake that is often made. If you are not going to drive your car much, what the heck, just chuck some cheapo tyres on it. However if you are a Dolomite owner because you enjoy the drive of the car fit the good stuff and enjoy the drive more. When i used to drive my Dads car, i have known fewer cars that make you want to thrash it as much. It sounded cool on those webbers, and giving it some beans round a corner did feel cool (though a bit understeery).

If you use better quality parts made to the same design as they were in period then the CN36 will handle better. If you slightly modify the suspension, make it a bit stiffer, a bit lower and add a bit of adverse camber then the CN36 will still handle better. However, yes if you slam it on the deck, make the suspension stiff as a board with loads of advers camber, possibly a bit of caster as well it will be horrible on the road however you will have changed the car so you can gain more grip out of a more modern squarer shouldered tyre. But it will let go more violently when it does brake away. It will be auful to drive on t he road, but on a perfectly smooth race track you will have more ultimate grip.

horses for courses

A CN36 will handle better on a classic car. However a more modern tyre will put more rubber in contact with the road for straightline braking and cut down wheel spin (who wants that, wheel spins are cool). However all this comes at the expense of handling in the corners, because your chassis was not the kind of chassis they developed the modern tyre carcass for. modern tyres are developed to work in an enviroment with much cleverer suspension and steering. as car design has moved forward the tyre design has followed that and offered features that would not have been appropriate on earlier cars. a modern car has a greater ability to present a tyre foot print to the road flat. where a classic car has to deal with the chassis rolling.

what are the advantages of a modern tyre:-
  • flatter wider foot print - This is a disadvantage on a classic car, unless it is modified to suit.
  • better build quality - well no. these CN36 are built by Pirelli. on of the worlds best tyre manufacturers.
  • better rubber compounds - nope. the CN36 is built using modern compounds. so particularly they move water far better than they did
  • tread patterns better designed to move water and stop aquaplaning - wel yep, i guess so, but that advantage is lost by the wider flatter foot print
Well i've seldom heard such inaccurate and biased BS! I'm sorry Dougal, but your comments would sound better from someone who DOESN'T have a vested interest in selling these tyres! I also fully understand that market forces are in play here, these tyres are made in very low volume by normal manufacturing standards, they are never going to be cheap! And from what you've said above, thay are not ACTUALLY a reproduction of the original CN36, they are a modern tyre that looks a bit like the original, made by the original maker.

I don't sell tyres and have no axe to grind, my experience (nearly 50 years of modifying cars) tells me that you CAN make an old car work well on modern rubber.

As to completely different suspension, 95% of moderns are on a Macpherson strut, the same as my 50s MKII Zodiacs. The double wishbone of the Dolomite is a better system still used on F1 cars today! It's only been dropped on production cars for cost reasons! My car has been set up to lose that understeery tendency you mentioned, it handles neutral tending to oversteer at the limit. And still has sufficient power to break the rear end away for power oversteer at will so it's still plenty of fun. However, unless you are on gravel, sideways is NOT the quickest way round a corner, so I like a sharp turn in and point and squirt handling! Though set up with a bias towards track work, it still needs to be used daily as a road car, so it is firm but not rock hard, low but not scraping and has only minimal extra neggy camber with most other geometry stock. I'm not one of those people who put 165 tyres on 8" rims and 10 degrees of neggy on a car that's riding the bump stops and ripping the exhaust off on every speed bump NOSIR!

A wider tyre does have it's disadvantages in the wet and in the snow, you might as well not bother! But honestly, how many classic owners take their car out in the snow? Even I leave the Carledo at home when it's snowing and it's my daily driver normally, but as you say, at this ultimate point, horses for courses!

Steve
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2 door '73 Toledo with Vauxhall Carlton 2.0 8v engine OWF 797M (The Carledo)
'78 Sprint Auto with Vauxhall Omega 2.2 16v engine EGP 247T (The Dolomega)
'91 Cavalier 2ltr 8v auto
'95 Cavalier 2ltr 16v auto
Spectrum Auto Services, Servicing, Repairs, Electrical, Recomissioning, MOT prep, Trackerjack brake fitting service.
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PostPosted: Tue Nov 19, 2019 2:15 pm 
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I have to agree with Steve. What is the point of buying an expensive remake of an old tyre when so many good tyres are available at much lower prices. I have 175/70 x 13 Uniroyal Rain Expert on my Dolly and they seem excellent. Not noisy, good ride and plenty of grip in the wet. They don't look at all out of place on a 42 year old car and they cost £40.68 each including VAT and fitting from my local tyre man.

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 Post subject: Man, man...
PostPosted: Tue Nov 19, 2019 7:56 pm 
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Do I really have to read through all of that Dougal?

Well, well a salesman who talks down to his potential customers?



Ian.

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PostPosted: Mon Dec 02, 2019 10:09 am 
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you all seem to be missing the point.

everything i say will just be read as sales pitch. the determination to buy tyres on price is difficult to overcome. the CN36 is not just an expensive re make of an old tyre. It is tyre built by one of the worlds best tyre manufacturers in a period tread pattern so it looks cool. but more importantly it uses up to date modern compounds, quality control and mostimportantly a cracss design developed to compliment the chassis of '60s and '70s cars.

Anyway you will just read that as a sales pitch so please have a look at these independent views from your old competitor the BMW 2002 https://www.bmw2002faq.com/forums/topic ... nt-1380997


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PostPosted: Mon Dec 02, 2019 8:39 pm 
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An interesting debate. So you appear to be saying that these tyres will make our cars handle better, stop better (in all conditions) and have a better ride than modern tyres? If that can be proven, I'd happily use them in preference over my current Dunlop Street Response2 tyres.
I for one certainly don't buy tyres based on price, I buy them based on whether they are SAFE, regardless of cost. I'm sure that the majority of owners do likewise.

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PostPosted: Wed Dec 04, 2019 10:27 am 
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Quote:
An interesting debate. So you appear to be saying that these tyres will make our cars:
Quote:
handle better,
without doubt. Yes. categorically.

The Pirelli's only competitor would be an Avon CR6ZZ https://www.longstonetyres.co.uk/vintag ... cr6zz.html because that is the only other tyre that has a carcass designed to compliment a chassis like yours, importantly the carcass is designed to compliment a car that rolls more in the corners than modern cars. And is rear wheel drive.

So if you want to make your car benefit from the extra grip that a modern tyre carcass offers in the corners you have to spoil it, as a road car, by stiffening and lowering the suspension and add caster and some adverse camber. and with respect, that sort of adjustment to actually get this balance right takes hours of testing and is beyond the bounds of a mere mortal. that is the sort of thing you need a proper test driver and careful adjustments to get the balance right.

Without doing these adjustments your car will not handle as progressively on a modern tyre carcass, because when it gets close to the edge of grip then it will loose traction more suddenly.

The handling thing to me is the massive advantage with the Pirelli
Quote:
stop better (in all conditions)
well no, you can't have both. straight line braking comes at the expense of handling to some extent

In a straight line, a good quality modern tyre in the same size will present a little bit more rubber to the road. However only if it is a top quality tyre, will the compound be as good as the Pirelli. So a modern tyre of similar quality to the CN36 (So probably only really Pirelli, Michelin or Goodyear, maybe Conti or Bridgestone) will stop slightly better in a straight line than the CN36. but a budget tyre will not.

Fitting fatter foot print tyres will improve your stopping distances in a straight line.

However in unsettled braking, then the handling benefits will help you bring your car to a holt better on the CN36 because you will be able to feel what is happening better, and it will all round be more progressive. so less likely to suddenly totally loose it.

A German magazine did a modern tyre test on the CN36 tyre a few years ago, and this is the real clincher; in the braking test

In dry braking the CN36 scored 1
In wet braking the CN36 scored -1

So although it is fair to say more rubber on the road will stop you better in a straight line the CN36 scored near as damn it the best possible score. that is down to build quality and compounds.
Quote:
and have a better ride than modern tyres?
yep.

comfort wise, a top quality modern tyre of the same size will give similar comfort.

A CN36 will drive in a straight line better on our rutted motorways. the steering will self centre better and the car will track less.

If you go lower profile you will sacrifice comfort.

If you go wider you will increase tracking.
Quote:
If that can be proven, I'd happily use them in preference over my current Dunlop Street Response2 tyres.
I for one certainly don't buy tyres based on price, I buy them based on whether they are SAFE, regardless of cost. I'm sure that the majority of owners do likewise.


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PostPosted: Wed Dec 04, 2019 12:08 pm 
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The 175/70/13 is exactly the same size as fitted to (just as an example) The MkII Astra estate! So by your own words, it would be a lousy choice on THAT car because it's FWD, Macpherson strut suspension and a more modern design of car!

I'm very sorry, but i'm calling BS once again!

I know that Pirelli make good tyres, they've ALWAYS made a premium tyre and at a premium price to match.

I understand that these particular tyres are made in very low volume for a specialized market, so they are ridiculously expensive to make. And Pirelli are in business to make money!

I also know that fitting different size wheels and tyres to ANY car can be a minefield if you don't know what you are doing, I once fitted 7x15s with 205 tyres to a Vauxhall Nova and made it instantly almost undriveably dangerous! The footprint was just TOO big for the weight of the car, it torque steered like crazy and locked up if you looked too hard at the brake pedal. They came back off 2 hours later! Some people who don't know better drive around like this for ages and some inevitably pay the price for the lesson!

But no matter HOW you slice it, they are not the one and only tyre that is suitable for our cars.

ALL tyre design, like so many things on cars, has to be a compromise, you can't have terrific grip AND long life for example.

There is no one tyre that can do it all as you seem to suggest is true of the CN36. When choosing a tyre (irrespective of cost) you have to make a conscious decision about what you want it to do. If you want fuel economy and long life you choose a different tyre to someone who wants ultimate wet peformance or trackday levels of grip in dry weather. If you only want something that looks "original" on a trailer to shows, the choice is different again. This is just a few possibilities with the stock size, outside the myriad possibilities offered by different wheel/tyre combinations.

And by the way, you DON'T have to ruin a car's ride to exploit a few extra mms of tyre width or a 10% change in profile, i've been modding cars for nigh on 50 years and I KNOW how to make a car work well on a track AND behave well on a bumpy B road. You just have to use a bit of common sense (yes, I know sense is NOT common)

In conclusion, i'm not actually running down the CN36. I'm sure it is a well designed and well made tyre. And i'm personally pleased that someone is at least TRYING to do something that will keep our older cars on the road. After all, if you can't get tyres, you can't drive far! Whether it represents good value for money in a still competitive marketplace is another and highly subjective matter, to me, it doesn't, but that is only MY opinion.

To Andy, I would say, I know you've had a nerve wracking experience, almost certainly caused, in part at least, by driving on old, hard tyres. But don't throw away your new Street Response IIs just yet. They are fine till they get down to 3mm or a tad less! When you've worn THOSE out, you can think again!

Steve

_________________
2 door '73 Toledo with Vauxhall Carlton 2.0 8v engine OWF 797M (The Carledo)
'78 Sprint Auto with Vauxhall Omega 2.2 16v engine EGP 247T (The Dolomega)
'91 Cavalier 2ltr 8v auto
'95 Cavalier 2ltr 16v auto
Spectrum Auto Services, Servicing, Repairs, Electrical, Recomissioning, MOT prep, Trackerjack brake fitting service.
Apprentice served Triumph Specialist for 45 years and home of Maverick Triumph.PM for more info or quotes.


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PostPosted: Wed Dec 04, 2019 1:44 pm 
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Hi

I think instead of spending £400 on an old style tyre, I think my Gaz coil-overs, MGF wheels and brand new Avon ZV7 works better, although to be fair, it did cost me £450 in parts did the labour myself, so cost wise, maybe not a direct comparison, but everything about the stopping, handing are far better and I have also no interest in originality.

Regards

Barry

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PostPosted: Thu Dec 05, 2019 6:37 pm 
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Quote:
To Andy, I would say, I know you've had a nerve wracking experience, almost certainly caused, in part at least, by driving on old, hard tyres. But don't throw away your new Street Response IIs just yet. They are fine till they get down to 3mm or a tad less! When you've worn THOSE out, you can think again!

Steve
I'm quite happy with them but as the car won't be covering huge miles or being trashed around a track, I suspect that they'll be replaced long before they get down to 3mm of tread simply because I don't want them "going off". Whether I replace them with these new "wonder tyres" remains to be seen...

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PostPosted: Thu Dec 05, 2019 9:00 pm 
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I just had to replace the two rear tyres on SWMBOs Picasso. They still had a good 4mm of tread left, but were the original fit Michelins from 2006 when I checked thoroughly! Both had severe cracking around the sidewall/tread joint and one was starting to deform into a worn out bulge in one spot.

Even the best of us can be guilty of neglect sometimes! And even a premium grade tyre doesn't last forever!

Steve

_________________
2 door '73 Toledo with Vauxhall Carlton 2.0 8v engine OWF 797M (The Carledo)
'78 Sprint Auto with Vauxhall Omega 2.2 16v engine EGP 247T (The Dolomega)
'91 Cavalier 2ltr 8v auto
'95 Cavalier 2ltr 16v auto
Spectrum Auto Services, Servicing, Repairs, Electrical, Recomissioning, MOT prep, Trackerjack brake fitting service.
Apprentice served Triumph Specialist for 45 years and home of Maverick Triumph.PM for more info or quotes.


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