flak monkey
|
| posted on 7/5/06 at 10:33 AM |
|
|
Its not only the footprint that affects how well your car sticks to the road. Its also the amount of flex in the sidewall.... (all other things being
equal)
Sera
http://www.motosera.com
|
|
|
|
|
MikeR
|
| posted on 7/5/06 at 01:00 PM |
|
|
The other point about larger tire walls is that they are more progressive in the give, as they can flex they will, as you reach the limit they will
start flexing giving you warning of whats about to happen. Low profile tyres don't have this.
(this is all been read from books, i've never experienced it in real life, so if its wrong some one please jump in and stop me perpetuating this
myth)
|
|
|
David Jenkins
|
| posted on 7/5/06 at 01:49 PM |
|
|
Myths should always be perpetuated... 
A thought just went through my mind (just the one?) - I wonder how many RWD cars the bloke had driven prior to this one? It is a different technique
from FWD, especially near the limit.
But when it comes down to it, it was probably inexperience and over-exuberance that did it, rather than tyres, RWD or FWD, etc.
Still, I wasn't there, so what do I know... I just hope that he was OK, and that the car can be fixed without too much expense and hassle.
David
|
|
|
Syd Bridge
|
| posted on 7/5/06 at 05:54 PM |
|
|
Why doesn't somebody contact a tyre company, give them the weight of the car, and ask for a recommended tyre??
The result will raise more than a few eyebrows.
Cheers,
Syd. 
Edit: Ask for diameter, width and profile.
[Edited on 8/5/06 by Syd Bridge]
|
|
|
MikeR
|
| posted on 7/5/06 at 11:25 PM |
|
|
go on then
|
|
|
Syd Bridge
|
| posted on 8/5/06 at 08:23 AM |
|
|
AHH,
Now, if I put up what I got back I'd be poo-poo'd till the end of man. I may be old, but I'm not stupid or senile, yet.
No, this is for one of the 'experts' on here to go after. I just wonder if the truth will be posted.
I've been through this exercise numerous times for customer projects and insurances. The tyre companies know their stuff.
Cheers,
Syd.
[Edited on 8/5/06 by Syd Bridge]
|
|
|
NS Dev
|
| posted on 8/5/06 at 08:37 AM |
|
|
Avon ACB 10?
Not called round but would guess that there aren't many tyres designed for cars that only weigh 500kg
Retro RWD is the way forward...........automotive fabrication, car restoration, sheetmetal work, engine conversion
retro car restoration and tuning
|
|
|
iank
|
| posted on 8/5/06 at 09:36 AM |
|
|
quote:
Originally posted by NS Dev
Avon ACB 10?
Not called round but would guess that there aren't many tyres designed for cars that only weigh 500kg
YOKOHAMA A048-R 165/55X12
YOKOHAMA A32-R 165/70X10
All the best mini's wear them
|
|
|
cossey
|
| posted on 8/5/06 at 10:01 AM |
|
|
avon cr500s designed for caterham.
[Edited on 8/5/06 by cossey]
|
|
|
DarrenW
|
| posted on 8/5/06 at 10:28 AM |
|
|
quote:
Originally posted by Syd Bridge
Why doesn't somebody contact a tyre company, give them the weight of the car, and ask for a recommended tyre??
The result will raise more than a few eyebrows.
Cheers,
Syd.
Edit: Ask for diameter, width and profile.
[Edited on 8/5/06 by Syd Bridge]
Ive just emailed Toyo as im using Proxes right now. Ive asked for recommended tyre for my 15"'s and also what wheel/ tyre combo is
recommended if i were to change the wheels.
|
|
|
irvined
|
| posted on 8/5/06 at 12:54 PM |
|
|
quote:
Originally posted by zilspeed
People just don't realise how quick a seven type car is.
Yeah i know what yuo mean there, i was sauntering down the a7 at what i thought was a steady 60 and 50 on the sharper bends, after calibrating my
speedo i realised that i was going a lot faster than I realised, didnt feel like i was going quick at all.
I think the combination of little body roll, being strapped in rigid, and being so low to the ground helped there.
At least he didnt hit anything solid, hopefully it can be rebuilt fairly easily.
Cheers
David
http://irvined.blogspot.com
|
|
|
ned
|
| posted on 8/5/06 at 01:23 PM |
|
|
quote:
Originally posted by iank
YOKOHAMA A048-R 165/55X12
YOKOHAMA A32-R 165/70X10
All the best mini's wear them
would like to see you get those size wheels over your brakes on a locost 
[Edited on 8/5/06 by ned]
beware, I've got yellow skin
|
|
|
iank
|
| posted on 8/5/06 at 01:34 PM |
|
|
quote:
Originally posted by ned
quote:
Originally posted by iank
YOKOHAMA A048-R 165/55X12
YOKOHAMA A32-R 165/70X10
All the best mini's wear them
would like to see you get those size wheels over your brakes on a locost
[Edited on 8/5/06 by ned]
True enough (though 7.5 inch cooper S 2 pot brakes are fine for stopping a >500kg Mini 7 racers, a discussion for another day )
My point was those tyres are actually designed for ~500kg cars unlike 99% of the rubber on the market.
|
|
|
Syd Bridge
|
| posted on 8/5/06 at 03:59 PM |
|
|
quote:
Originally posted by chris mason
well i followed Syd's advise and contacted 2 tyre manufacurers who shall remain unnamed,
of the reply's i got, i shall be sticking with my 195/50/15
Chris
Mr. Mason,
Would you care to name the manufacturers and post their recommendations. You should be able to get them to email you their recommendations, then you
could put them up here for all to see.
Until then, the proverbial goes on the garden to fertilise the vegetables.
Cheers,
Syd.
|
|
|
Wadders
|
| posted on 8/5/06 at 08:09 PM |
|
|
I honestly don't want to get involved in any tea or sugar mixing, and know absolutley feck all about tyres, other than theyr'e round,
black expensive, and don't last long (is it just me) but after following all this erm... interesting debate. i got round to wondering why it
is, when you go to a hillclimb event, most of the serious competitors including the featherweight cars seem to run extra wide tyres? Personally
iv'e switched to 13's, more for weight saving and cheaper sticky tyres than anything, 20 odd kilos saved, means i can drink more
Al.
|
|
|
cossey
|
| posted on 8/5/06 at 08:38 PM |
|
|
the tyres designed for lightweight sports cars are:
avon acb10
avon cr500
toyo r888
yoko a021r
yoko a032r
yoko a048r
of those the acb10s are very light but are crossplies so need different geometry and are appaling in the wet.
cr500 designed for caterham to be better in the wet than acb10s, used by the graduate race series so lots of barely worn ones aobut soon as many
racers replace them early (well the caterham ones do)
toyos arent that widely used and are fairly new quite similar to the yoko 48s
the yokos are all fairly similar but have slightly different compounds and tread patterns of those the 48rs are becoming the most popular due to
better wet grip. the 48rs are the rgb control tyre, the 750mc kitcar championship uses either 32rs or 48rs.
the yoko a359s are used as the locost championship control tyre but that is more due to cost it seems as they are much harder and dont have as much
grip.
the rgb standard seems to be 185/60/r13 at the front and 205/60/r13 at the rear, which from what ive seen seems to be a good compromise.
|
|
|
DarrenW
|
| posted on 11/5/06 at 11:08 AM |
|
|
Ive just spoken to Toyo as planned. Without going into too much waffle iam now very happy that my choice (T1-S 195/50 x 15) is correct for my use and
should i start to participate in more track days will consider another set of wheels with 195/50x15 or even 205 R888's.
i have to say the guy at Toyo was extremely helpful and happy to spend 15mins chatting. Top man - great service.
|
|
|
Fozzie
|
| posted on 11/5/06 at 03:40 PM |
|
|
quote:
Originally posted by Syd Bridge
From the pics...
This is yet another one with too wide tyres on too big a diameter rim and too low on the profiles......and probably with too high
pressures,...........and all probably running hooked up to too hard springs and too hard adjusted dampers.
When will people ever learn??
Syd.
Edit: You will all be aware by now that I am an avid exponent of 13" wheels (lighter than bigger types)
tyres no bigger than 185's(gives better road pressure),
and no less than 60% profile(for a more forgiving ride and handling.)
That all amounts to 185/60's on 13" rims.
You youngsters can all use what you want, just keep posting the pics of your prangs so us old folks can keep saying'I told you so'.
[Edited on 6/5/06 by Syd Bridge]
Oh Syd you are sooooo right! The times I/we have said all that you have said above so many times  almost word for every word!
Fozzie
sorry for the late reply, just got back from hols today
'Racing is Life!...anything before or after is just waiting'....Steve McQueen
|
|
|
Jasper
|
| posted on 11/5/06 at 03:55 PM |
|
|
Ok - another person here who knows bugger all about the science.
If wide tyres are crap on a lightweight car - then why do Caterham fit 245 width Avon CR500s to the new CSR?
This is not a dig - I'm really interested - as I'm gonna have around the same power to weight ratio in my car and am thinking of fitting
the same tyres.
I followed Francy Clarkson around the Alps in this car with these tyres, on dry, damp, greasy, snowy, stony roads and she was driving like a nutter
and they never missed a beat, I never saw the car step out in anything but a controlled manner (and that not very often) - all of which lead me to
believe that Caterham has chosen right.
I was particualrly impressed with their wet capabilities, seemed to grip the road exceptionally well.
I understand the theory of what has been said here - just the pratical application surely has to be just as important?
As surely it also depends on the compound, as standard road tyre will heat up and become more grippy far slower than a nice sticky cut slick like an
888 or CR500?
I've also spent a great deal of time on a cossie locost (Hicosts) which runs 245 Goodyears. And whilst heavier than a standard locost is still a
lightweight car. I've NEVER known it to step out at all, again in rather crap conditions as well as dry.
I'm sure the reason both of these cars run large 245 tyres is that they don't want the rears lighting up everytime they step on the
gas...
[Edited on 11/5/06 by Jasper]
|
|
|
David Jenkins
|
| posted on 11/5/06 at 06:56 PM |
|
|
I think that there are many factors that make drivers stuff their cars into the scenery - here's my little list of possibilities:
1. Inappropriate wheels and/or tyres.
2. Wrong tyre pressures / suspension settings.
3. Inexperience with:
3a. RWD cars.
3b. Very high power-to-weight ratios.
3c. Seven-style handling (i.e. their tendency to bite if abused)
4. Over-exuberance.
5. Recklessness/Stupidity.
6. Bad decisions made in poor driving conditions.
7. Sheer bad luck.
In most accidents I've seen reported here, a selection of these factors played some part in the accident.
Just my 2p's worth.
David
[Edited on 11/5/06 by David Jenkins]
|
|
|
Fozzie
|
| posted on 11/5/06 at 08:18 PM |
|
|
David, you have hit the nail on the head with your observations.....
IMO.... Every car is different, that is weight engine size, indeed a bec verses cec is a world of difference.
IMO you have to think very hard about how the car is set up with its weight. For example, a very light bike engine is going to handle very differently
to a car engine. It has never been a case of use bigger wheels with nice low profiles, it may, in the owners eyes look the 'biz', but it
doesn't mean that the car will handle well. The design of the locost assumes a basic suspension set up given the original locost concept of the
mk2 Escort, which of course used 13" wheels. Today, there is little choice when looking for tyres to fit a 13" wheel, and far more choice
with the bigger wheel and low profile tyre. Thats where a danger will lurk, because by changing the wheel/tyre/profile, a consideration as to shocks,
springs and tyre pressures has to be worked out.
No doubt Caterham have, like any good car builder, spent a lot of time and money on research to alter the suspension/shocks springs and tyre
pressures.
There are indeed a lot of light race cars using bigger, but again, I know a lot of time and effort would have gone into testing and changing the set
up to suit them. Remember also that when talking race cars, they are usually that, set up for the track, not always dual purpose (road and
track), in that case, a compromise is usually needed. It can be done, but a lot of time, effort and patience is required to make the bigger
wheels/tyres on a locost handle satisfactory.
I have not spoken to Hicost about his tyres, pressures, suspension etc. I do know the car, and although as you say Jasper, it is light, it is still
bigger and heavier than the usual locost that lends itself to the original 13" wheel design. I do seem to recall a conversation with him in the
past when he said that over time he has played with tyre pressures, and knowing James (Hicost), I feel sure he has/is always tweaking until the car
feels 'right' to his exacting standards!
All the above in my most humble opinion as always........
Just my 4 pence worth of course!
Fozzie
'Racing is Life!...anything before or after is just waiting'....Steve McQueen
|
|
|
Deckman001
|
| posted on 11/5/06 at 09:49 PM |
|
|
Wow a triple post, things have slowed up on here ??
Jason
|
|
|
MikeR
|
| posted on 11/5/06 at 10:47 PM |
|
|
Just to take this off on a tangent.
Someone I know used to work for a VERY large tyre manufacture that occasionally has a bad year.
Anyway, tyres aren't designed by engineers. Sad as it may seem they are designed by marketing. If a tread pattern doesn't look
'sexy' it won't get made.
So when you phone up someone what they are telling you is probably 50% theory and 50% marketing. Let me put it this way, could you imagine your
company putting someone on the end of a phone line to talk to joe public who'll say "naah, mate our product is complete crap, worst in the
market place!"
Now if a car manufacture approaches someone to make a tyre what are they going to ask for? Make me the best tyre you can or make me the best tyre you
can that I'll be able to sell? If the trend for tyres is to have low profile and large alloys are caterham really going to start sticking
10" alloys with 100 profile rubber on? Caterham now targets rich people, not racers to buy there product so the product they'll commission
will be a compromise.
|
|
|
David Jenkins
|
| posted on 12/5/06 at 06:47 AM |
|
|
I missed one possible cause off my list:
Mechanical failure (always a higher risk on a home-built car)
David
MikeR - if you click on 'edit' you could delete 2 of your posts...
|
|
|
DarrenW
|
| posted on 12/5/06 at 08:40 AM |
|
|
Jasper - when i spoke to my tyre supplier they said my car and power (140ish) / car combo should be fine with 195/50 x 15's. If i up the power a
bit and fancy trying a set of R888's then he would recommend trying 205's.
On cars with much more power they have seen success with 225 rears. I suspect the Caterham is a jump up from that hence 245's.
As said there is no exact science. Joe Public can rarely try different types back to back any way.
Ref marketing etc - yeah very true but thats just business. It was interesting that the guy i was talking to (an engineer not a commercial bod) has
actually been known to not recommend one / any of his tyres for a particular application based on his extensive experience. Maybe some of the hotline
operators simply dont have the experience so can only go off the marketing blurb that the computer throws up????
Anyway im happy with mine and have an option to improve should i require for not a lot of money.
|
|
|
