Tyres for an S1 Continental

Terry Unwin · Posted: Fri Mar 11, 2016 9:21 am Post subject: Tyres for an S1 Continental

In my experience there is no doubt that a Continental has far superior directional stability on radials but at the (slight) cost of appearance and a greater cost in ride quality. Various "experts" suggest 205/70, 235/70 or 235/75.

The latter is certainly the right size for a standard steel car which came new on 8.20 cross plies. They also have the tallest sidewalls (if I have properly understood the aspect ratio), so look better.

However Continentals always ran on narrower tyres when new, 7.60 for early cars and 8.00 for later ones.

As I am about to replace the 235/75 Goodyear tyres on my late S1 Continental I'd be interested in the views and experience of owners of similar cars in respect of both size and brand. Thank you.

Stephen Blakey · Posted: Sun Mar 13, 2016 9:59 pm Post subject:

Maybe interrogate Barry?

https://www.bdcl.org/forum/viewtopic.php?t=3175

Barrie Warrener · Posted: Sun Mar 13, 2016 11:10 pm Post subject:

Hello Terry.
I started my ownership of my S1 Continental on cross-plies and it was tiring to drive requiring constant directional correction.
When I changed to Michelin 235/75/15 the difference was positive and palpable but I noticed no drawbacks like excess noise or diminution of ride comfort.
I then changed to Hercules 235/75/15 as the Michelins were getting old/worn.
I chose them simply because they were the cheapest as all my investigations about the difference between available brands was inconclusive.
I have been very satisfied with them to date.
Also I think they look good giving the car a muscular stance and fill the wheel arches well which is not always the case with cross-plies.
I run them at 30lbs psi.

Terry Unwin · Posted: Mon Mar 14, 2016 10:33 am Post subject: Tyres S1 Continental

Thank you! Very helpful. Hercules tyres have been mentioned by another so your experience validates that choice.

Barrie Warrener · Posted: Mon Mar 14, 2016 6:42 pm Post subject:

I've been thinking about this topic and come up with an abstruse point which has little practical implication but nevertheless is exercising my grey matter.
When running on cross-plies my speedo was remarkably accurate when matched to a sat-nav.
Now, with radials, accuracy is maintained up to 70mph whereupon the readings become increasingly optimistic with 110 on the speedo equating to 90 on the sat-nav.
Is it something to do with the relatively soft sidewalls of the radials expanding whereas the stiff cross-plies don't?

John Murch · Posted: Tue Mar 15, 2016 11:41 am Post subject:

How strange, but if it were to do with the tyre diameter expanding, would that not have the reverse effect? For a given rpm your speed would increase and the speedo would under read. Or have I got that wrong.
I assume that the speedo is a mechanical device, perhaps due for specialist attention?
John

edited

Just had a look at tyre diameters, Couldn't find that for the Michelin cross ply, but the Dunlop is 766mm , Couldn't find the dimension for Hercules, but another of the same designation was 734mm so if this is typical, you could have about 5% lower gearing overall.

Stephen Blakey · Posted: Tue Mar 15, 2016 12:28 pm Post subject:

Longstone reckon the Hercules is 734 as well. On a point of pedantry, I make that a 4% reduction in gearing.

I can't think of a mechanism that would cause the tyre to shrink with speed. Indeed, the steel bracing in the tyre would surely prevent diameter change anyway? Maybe the crossply does grow and the speedo calibration takes this into account? Having said that, the error you quote would require a massive change in the tyre diameter which seems most unlikely. Probably best to ignore it and look at the sat-nav. I can't see trying to get your speedo re-curved as a route to lasting satisfaction but that could just be me getting old and grumpy.