Tyres - What influences 'grip' the most?

[graham bahr]

i dont think its common any more, as nearly everone knows how weak they are, and therfore use something else wherever poss.

[retro_msport]

So getting back on topic................

1, tyres.. run the widest you can on a rim at least 1/2" wider

2,Run soft if you can make them last without destroying them due to heat

3, run harder if your hard on tyres or your limited on what geometry you can run, ie; wrecking the outer edge due to lack of camber,

4,Set the car up to the best of your ability/rules to make the most of the tyres, trying to keep the tyre flat when its working hardest.

5,Dont join a championship that limits you to 7" rims and a control tyre if your racing a 2 tonne Yank Tank.. (sorry Al )

[Al Weyman]

8" Grahame, 8". And it only weighs around 1450 kgs as decreed by the regs.

Retro check out the rules here http://www.barc.net/PDFdocs2005/modprodregs2005ver1.pdf in particular 5.8.2 which specifically forbides this modification. Whether of course anyone takes any notice of it is another matter of course :-)

[graham bahr]

AL only 1450kg !!! hmm i thought my car was too heavy @950 kg can see why you have a bit of an issue with 8 inch rims and road tyres, i'm on slicks and am looking to go to 9inch (currently 8), although probably on the rear only

[Al Weyman]

They are Dunlop Formula R's' not a road tyre, maybe I should have buffed them first. I may do that actually.

[graham bahr]

from what i've heard buffing them will make them last longer as the rubber wont move around so much and over heat

[retro_msport]

Al... gotta agree they have pretty well stuffed the camber/toe liveaxle , and its not something that can be hidden...

[greenamex2]

Originally Posted by retro_msport

2,Run soft if you can make them last without destroying them due to heat

3, run harder if your hard on tyres or your limited on what geometry you can run, ie; wrecking the outer edge due to lack of camber,

Are you talking about spring rates or tyre compound?

[retro_msport]

Tyre compounds... just what i've collected from all posts in the thread ie;

run softer as if you go harder you may well be sliding and loosing the life of the tyre due to abrassion

And run harder if the tyres are going off due to overheating down to driving style, type of car, limitations on tyre size and geometry mods

[Al Weyman]

Originally Posted by retro_msport

Al... gotta agree they have pretty well stuffed the camber/toe liveaxle , and its not something that can be hidden...

Sorry you can blame me for that! However I think with the BARC's annocement of a new Production series and also mentioning the new class E (economy?) in Toyos where the Prods can also run when out of date is good so maybe we were right to bring in those constrains in the first place.

[retro_msport]

Originally Posted by Al Weyman

Sorry you can blame me for that!

Ita allright.. i'll let you off, as within those regs you can still 4 link an escort using the original pick-ups....

[dtype38]

Ok, so it seems I might not be going down the right route using 225s (8.85inch) wide tyres on 7" wide rims ...

But would anybody like to hazzard a guess at what's happened to the second tread ring on my front right tyre. It goes all the way round the tyre in a regular pattern and appears to be burst blisters from below the tread rubber. I did this sometime during a two day meeting at Croft on a warm dry day, but didn't notice it till I took them off the other day.

[greenamex2]

No idea, somebody in the paddock doesn't like you?

It looks a bit like a piece of metal has gouged it out but unless this happened at pretty low speed the 'gouge' is usually straighter.

Does it look like a crack at all and is the surrounding rubber VERY blue?

[retro_msport]

Maybe caused by the tyre tucking under, and folding the middle in.. but that would normall happen at a groove... and then being pulled apart while cornering on the next turn that goes the opposite way to the one that cooked that side

[graham bahr]

Originally Posted by dtype38

Ok, so it seems I might not be going down the right route using 225s (8.85inch) wide tyres on 7" wide rims ...

.

well not unless you want boat like handling

[dtype38]

Denis, if someone in the paddock didn't like me, then they'd have had to be lying under the car as I drove along cos there's no gap in the damage around the tyre. My first thougth was that it had rubbed on a bit of the bodywork or chassis, but I did a thorough check and nothing is even remotely close to that part of the tread. Oh, and the blue colour is just from the camera flash, the grooves are just new black rubber and the tread faces slightly worn rubber (I've only used the tyres at three meetings).

If it was over-inflated and had been running on the mid two tread rings, could I have overheated just that block? The trenches run in a dash pattern all the way round and are 3-4mm deep, but the blisters you can see are only in one area.

Graham... you mean old Jags don't all handle like boats

Retro, I do get quite a bit of tuck-under, but my tyre walls move around a lot anyway. I thought it was normal for 60 profile tyres....

Here are what they look like under turn-in, braking and unloaded. The only mid heavy corner turning pic I have is very difficult to see the tyres because of the light, but look like the first
one below, but more so...

[Al Weyman]

Off To[ic Dtype but can you now use the picture post facility as those pictures do not seem to link to yours or anyone elses website.

[retro_msport]

Compare pic 1 to pic 3 and i would say that tyre is floating across a good inch.

i always like tyres to look like this \_____/ not this (______) always seem to have better turn in even if it means using a smaller width tyre, with little to no scrub on the outside edge.

What would be good for your car is one of those magnetic camcorder mounts, pointed at your tyres on the front, think it may scare you with what it shows though... oh by the way.. hope your not coming out in TRC next year, if your are disregard all of the above and go at least 2" wider than the rim

[dtype38]

Al, yes they're uploaded rather than linked images. It's a newish system which they use over in the Art/Photograhy forum, but it can be used in other places by registered users. It has stricter size limits than linking an image, but is useful for multiple pics cos of the thumbnail system.

retro... I don't doubt my tyres move around a great deal. It's just that no one has ever said that I should worry about it... so I haven't been I simply thougth that it was normal for deep profile tyres, even F1 style! You're quite correct that I get plenty scrub on my outer edges, but I was just going to add a bit more static camber to deal with that. Talking of which, you can just about see that under breaking my front rims take a noticable amount of negative camber, but the tyres just squash flat anyway so it doesn't really matter.

So... if you'd recommend tyres that go \___/, then how do I choose between wider rims or narrower tyres. And wouldn't this sort of thing be better solved by going to low profiles on a bigger rim?

Anyway, currently my intermediates (yoko 032s) go off after about 8-10 mins in the dry. Last time out though, the dries (yoko 008s) did start to feel a bit odd (slippery) after about 16-18 mins... could be when I did the damage. I would expect them to last longer than that. Could I be generating too much heat in the carcass because of the amount of distortion I'm getting in the walls?

[retro_msport]

If you can go wider on the rims then do it... Harry at Image wheels does some nice D type wheels....

What I think may be happening is the cars heavy and under tyred so putting too much work on them, so your cooking them, Have you ever taken tyre temps to see whats happening?

[TEAM78]

Originally Posted by dtype38

So... if you'd recommend tyres that go \___/, then how do I choose between wider rims or narrower tyres. And wouldn't this sort of thing be better solved by going to low profiles on a bigger rim?

Anyway, currently my intermediates (yoko 032s) go off after about 8-10 mins in the dry. Last time out though, the dries (yoko 008s) did start to feel a bit odd (slippery) after about 16-18 mins... could be when I did the damage. I would expect them to last longer than that. Could I be generating too much heat in the carcass because of the amount of distortion I'm getting in the walls?

Oh boy big subject.
your tyres overheating could be a number of reasons. the dampers could be to blame or the the suspension is too stiff etc... Oh and yes your tyres should definitely last longer than if they were slicks 8mins, the cause of this requires knowledge of the set up and other things..as for inters dunno, no experience and im a novice
Wider tyres also have higher cornering stiffness hence less deflection for the same given slip angle, ooo a little knowledge could be dangerous

As for \__/ and /__\, you will find the stories in Paul Haneys tyre book interesting in how they discovered that wider was better, You can also over tyre a car apparently, yet to find this out myself.

[dtype38]

I've now discovered that there is a blister under the surface of that tread ring going nearly the full way round the tyre. Definitely overheating I'd say, and judging by what's been said so far, I'd say its probably because I'm tucking the tyre under so far in the corners, that I'm not really running on the tread properly. I've been told I'm over-tyred a couple of times, so maybe I need narrower tyres rather than wider rims.. bit less expensive too



Ooops... err... thanks for the help guys. I'll better keep shtum now before there are any unkind comments about my car.

[graham bahr]

over tyred could be taken in two ways, either over tyred for the rim width, which D type i'd definately say you are or over tyred full stop.

assuming that the tyres arnt too wide for the rims, which they are in d types case, the way to check as to if the whole combination is too be is to check the tyre temps, quite simply if you dont get the tyres well and truely hot racing in the dry then they must be too big, either that or your driving like ya granny, i am assuming here that the geometry is correct

[greenamex2]

I'd be very surprised if your car was 'over tyred', particularly if you have managed to bilster a tyre.

I agree with Graham that you need to know your tyre temperatures but the obvious solutions are -

- A softer tyre to stop the tyre sliding and over heating
- A harder tyre so it can just live with the sliding
- A wider tyre to reduce tyre temp (ie same 'friction' across more rubber)
- A wider rim which will reduce tyre temp (as above plus less heat through 'flex')
- Softer suspension to reduce sliding
- Reduce tyre pressure if the blister is caused by excess pressure causing uneven tread to ground contact

I am sure Retro will be able to supplement/contradict the above.

[retro_msport]

Nope Dennis, no contadictions from me... totally agree with using the temp gun, as i have a feeling that the tyres running on the outside edge due to the tyre tucking under because its too wide for the rim,

Dennis would you agree to this.. 9" rim with Dtypes tyres fitted, check temps to get pressure and camber setting right for the particular conditions, and then fine tune spring rates with temps and stopwatch