14" tyres wanted for Corsa

[Spac]

Bridgestones aren't the crappiest, but they're not the best either.

15s are where the market is, so they've always got the best commercially available tread patterns/compounds/construction. Look at Silverstone or Dunlop - their "best" tyres (S525 and SP86 respectively) are only available as 15s.
If you're running 13s or 14s, then you're stuck with tyres that are at least a generation older.

If you were talking about the usual 205 or 195/65x15s, the 15s provide considerably more contact patch, improving grip. Increasing the contact patch by increasing the rolling diameter will improve grip, noticably more than fitting a wider tyre.
Some of this improvement must relate to the reduced tractive effort (due to greater rolling diameter) and additional weight reducing wheelspin - but even allowing for those factors, there is more drive traction available.

The only reasons I can see for fitting a 185/60x15 rally tyre, would be to clear big brakes, and to get a newer pattern tyres. There may also be some benefit in unsprung weight too, I guess.

[Darren]

15's or 14's....??

As tyres are usually spinning then we must all have more HP than there is traction available on a loose surface. Yes?

Therefore traction is what breaks half shafts not excessive HP - which is still a good thing on a loose surface because it spins the wheel faster (and clears loose stuff enabling max. traction on the then cleaned surface). That increases the traction but there are all sorts other reasons the traction could change resulting in all sorts of weird and wonderful forces. Some have already been mentioned, especially issues of inertia (think of all the tread weight spinning around and being suddenly stopped and started - bad enough without the additional lever-arm offered by the 15's).

So, roughly: the force (available traction) multiplied by the lever arm (tyre radius) is the force exerted on the drive-train. It hard to believe that a change from 14" to 15" would make a huge difference considering all the other variables...and if you look at the number of people using 15's with standard half shafts, it probably doesn't! But there's no argument that it MUST physically increase the forces and hence the chances of failure. So if things are nominal in the first place you could expect a breakage (...sooner).

[afifield]

Originally Posted by Warps

May have a cheap source of Bridgestone tyres available to me, so the question really only applies to the Bridgestones. If Bridgys are the crappiest tyres out there, then maybe I need to rethink my plans.

In relation to RE460 Bridgestones, they haven't been available for a couple of years now, so anything you get will be starting to harden. The replacement RE470 is a left/right pattern which doesn't work as well when you swap them.

On the rear, we used to do a whole event on 460s, but could only get 35km out of the 470s before they wouldn't grip any more. The last couple of events we tried Dunlop SP85s. One pair have now done about 120km competitive and don't look like they've been touched.

The SP85 and RE470 are on a par performance-wise, but the SP85 lasts a lot better, and gives good traction through more tread wear. If you're after value for money, best go the Dunlops.

[Warps]

Hmmm interesting stuff.

The L/R tread patterns are a pain - means I'd have to carry 2 spare tyres.

Spac: I'm trying to keep the rolling diameter small for cleanance issues. It's going on an RX2, and I would have thought that a set of 205/65R15 rally tyres would be hitting guards everywhere. Hence keeping the rolling diameter as small as possible.

Is there a big difference in cost between 14" and 15" tyres?

As I said before, I'm investigating this as I may have access to very cheap Bridgestones (still negotiating a deal). However, sounds like there's much better tyres out there, and I'd rather get 120km use out of a dearer tyre than 35km use out of a cheaper one.

If this doesn't come off, I might just stick to running the 13's I already have, as I have over a dozen rims and about 16 tyres already. I'm having major struggles to get hold of 14" or 15" Mazda rims for any decent sort of price.

All the Ausrotarians think that Mazda stuff is gold plated, and won't sell 2nd hand 14" rims unless I pay them enough to step into a set of new 15" Simmons. Shyeah, right! Do I LOOK like an idiot (I can ask this question because nobidy on this site has met me face to face )

[Spac]

4x110 14s are out there, but are hard work to find.

I've had success in double-drilling Datto 200B SX wheels (they've got a solid back in the hub area, without the usual recesses between the stud holes). Not the lightest alloys, but strong and cheap.

Performance wheels sell 14" Challengers and Superlites new at not outrageous prices.

Buying new, the 14" tyres are a bit cheaper.
Buying second hand, 15s are way cheaper (for a given condition).

Based on the tyres I've had, there's less difference in the rolling diameters of a 185/65x14 and a 195/65x15 than the maths says there should be.

[Kagan]

S525's are available in 14's... at least I think they are... if not, I wonder what I run.

[Darren]

Originally Posted by Spac

Based on the tyres I've had, there's less difference in the rolling diameters of a 185/65x14 and a 195/65x15 than the maths says there should be.

Yeah, but it all changes if you use ones with tread on them

[Kaptainballistik]

Fifield and I have gone through the same 15 vs 14 's drama for a RX2. The correct offset for the front is not easily available in 15's , But is a Piece of Cake in 14's ( About $200 a rim new.) So stick with the 14's if you must .
I would personally only bother if you wanted to fit bigger Brakes. (Then they actually stop.......)

[Spac]

Originally Posted by Kagan

S525's are available in 14's... at least I think they are... if not, I wonder what I run.

S505s.

[Stewy]

Wow look at all the discussion I have missed out on.

So tyres then, ummm yeah, at this stage we are all sorted as Spac has shone through with some almost new rears and some used low profile 15s, then I need to find some rims to put them on.

Yes and no to what everyone has said, come to think of it im late for work so I will finish of why it is I use 14s another day.

Gota go.

[Swill]

You will get better stage times with 15s due them gripping better and they come in a better array of compounds. Not that it matters much with with my car

13s & 14s do look good as a spectator as the spin up easier (a reason why group G cars looked a lot faster than they are in reality) But sliding wheel spin is not the why to fast stage times.

Things that you will start breaking in the back of R180 Dato with standerd type stuff with the good rubber are:

Crown wheel & Pinion ( New ones are good for about 8 state rounds) 4.6 are stronger than 5.1 & 4.8
L.S.Ds unless there billet hats and carriers, your going to break it some time in the season. Pre load should be checked after every rally. Kaaz seem to hold up well, in preload and strength.
Inner shafts into the diff. You want the bigger ones, think there 28mm rather than the standard 26mm (Small ones go pop any time, big ones should be crack tested probably once a season)
Half shafts. Try and get them off a auto granny car thats never been on the dirt. Use the solid uni joints as the greasable one are weaker. (could last 1 stage i.e Fro or 20 rallys i.e Kari) C.V jointed things off a 300zx or something similar apparently are the go here (?)
Outter axles. With any luck they'll last a full season. Probably crack test them ever season as well. Kombi ones are a good replacement.(not bolt in though)

Apart from that there as strong as nails