Uk Class 2b - Tyre widths

[catfan]

Hi,

Im looking to compete in my caterham this year in hill climbs/sprints and was wondering whether it is worth changing to a bigger different tyre size.

I currently run list 1a Toyo proxies but was wondering if there was an advantage to changing the size from 195's all round to 205's front and 225 rears.

The car is very well setup with ARB's DA dampers, as light as I can afford (sub 540kg) and runs a 235bhp duratec engine.

Thoughts would be appreciated.

Catfan

[Anuauto]

Whats UK class 2B? Which region are you planning to compete in? (road tyre classes have no uniform national spec, despite what the Blue Book may imply, regions differ). If doing hillclimbs, much heavier cars such as Escorts often use nothing wider than 185/60. If primarily sprints, the tyre size you have may well be fine.

[dtype38]

Some thoughts...

If you've got your tyre pressures, camber angles, etc set up ok and you're a) overheating your tyres (ie working them too hard) or b) they aren't lasting a race, then you would probably benefit from wider tyres as they can take more load. If. however, you're struggling to get your tyres up to temp, particularly on cold/damp days, then putting wider tyres on will probably make matters worse.

I run 225 Yoko 038s all round and my car is 960kg and 230hp. They take a bit of heating up in the cold/damp, but also start to "go off" towards the end of a race on a very hot day, so I think they're about right for the car. In contrast, one of the chaps I race against is down under the 900kg mark with a bit more power and he uses 205s because he can't get 225 up to temperature (I think he has a smoother driving style than me though).

Hope this helps

[catfan]

Thank you for the responses.

The events I'm looking to do include Harewood, Croft & Three Sisters for example. Championship reg's state List 1a tyres of which the Toyo's are legal. List 1b's are banned.

Rear tyre temps will be OK because at Harewood I can warm them before starting but fronts I can't.

I guess the aim of my question is:

Is than advantage to running 205 front and 225 rear instead of the current 195's interms of grip, launch etc.

As the runs will only be so short I doubt the tyre will have issues fading away.

Thanks again,

Catfan.

[Anuauto]

The issues in speed events are usually all about not getting enough heat. Wider tyres will hinder that. I dont know 3 Sisters but its a kart track and probably more like Curborough than Croft so has more in common with a hillclimb? Harewood is the hill that is most like a race circuit but it is still a hill not a circuit. Croft might benefit from wider tyres if its more than one lap. Racing and Trackday experience will not normally be of much relevance to speed events. Stick with smaller size? Not sure about Toyo though (if its a tyre used in a race series, thats usually bad news for speed event use). Ask on somewhere like the Midlandspeed championship forum what other kit car drivers are using? The 4 south east regions have just allowed 1b for road kit cars in 2005 (to sort of align with south west but thus causing major problems for those who compete anywhere to the north or live near borders).

[greenamex2]

Have a look at the new Toyo T1-R's before spending lots of money on new wheels/tyres.

They are a much more European orientated tyre than the T1-S was.

We are being promised measurable improvements when we start using them this year in Toyo Tyres Mod prods.

As regards wider tyres, the general rule of thumb is a improvement in grip equal to the square root of the increase in tyre width. In your case this will probably amount to very little, especially when you factor in the extra weight!

Out of interest, what tyre temps are you running?

[THR]

i know a sucessful westie that runs 205's all round, gave a better 64ft and cornering grip was better, it was just basically faster!!
he used yokohamas tho, which i think are 1a.
i thought these were the normal tyre to buy for hillclimbs and such cos they were the softest ones u can buy.
he had a set for wet and a set for dry, on 6" rims.
they were diff componds and treads. one of them was a 32...summin but not sure wot the other one was!!

dont kid yourself that the tyre warming up to the line does a lot of good, it will help you in the 64ft time but not a huge amount over the timed lap!

[dtype38]

Catfan... I asked a mate with a quick Caterham who is also in the owners club for his comments. This is what he had to offer :

There are two camps. A lot use Yoko 32Rs in SuperSoft compound, but they're being phased out in favour of 48Rs (a softer compound and better in the wet). Many swear by Avon CR500s, as ACB10s are pretty much slicks.
Whatever, either will be much better than his Toyos. I run a 205 rear with a 185 front (60 profile on 13inch rims), but I spose it depends on his rim widths. With 235 brake it'll need all the width it can get )

[catfan]

Originally Posted by Anuauto

The issues in speed events are usually all about not getting enough heat. Wider tyres will hinder that.

Thats an interesting points. Curbourgh times over less than 35 seconds can hardly be seen as warming them up sufficently!

[catfan]

Hi Denis

For the toyos I tend to run 18f 17r, I did try running 1 lower as I did the so2's I used to run but they felt better slightly higher.


The new toyo's sound good. I would be interested to hear your feed back on them...

Originally Posted by Denis Bassom

Have a look at the new Toyo T1-R's before spending lots of money on new wheels/tyres.

They are a much more European orientated tyre than the T1-S was.

We are being promised measurable improvements when we start using them this year in Toyo Tyres Mod prods.

As regards wider tyres, the general rule of thumb is a improvement in grip equal to the square root of the increase in tyre width. In your case this will probably amount to very little, especially when you factor in the extra weight!

Out of interest, what tyre temps are you running?

[catfan]

Originally Posted by dtype38

Catfan... I asked a mate with a quick Caterham who is also in the owners club for his comments. This is what he had to offer :

There are two camps. A lot use Yoko 32Rs in SuperSoft compound, but they're being phased out in favour of 48Rs (a softer compound and better in the wet). Many swear by Avon CR500s, as ACB10s are pretty much slicks.
Whatever, either will be much better than his Toyos. I run a 205 rear with a 185 front (60 profile on 13inch rims), but I spose it depends on his rim widths. With 235 brake it'll need all the width it can get )

Yes cant run acb10's or 32r's for list 1a competition

[Anuauto]

A few points above. Not relevant to regions that run 1a, but 048 comes in 2 compounds and 032 was in 3. Has anyone who used the softest 032s really confirmed the softer of the 2 048 compounds is softer than 032?? As for the wet, 032 had more tread than 048 and 032 was little better than a slick in either damp or standing water in the opinion of many! O48 better in wet?? Hmm...
Heavier cars (eg Escorts- although the best is probably 20bhp short of the 235, under roadgoing saloon regs) in regions that allow the soft tyres have without exception used 185/60 (or gone back to that size after trying something wider) in all hillclimbs and short sprint courses. Even a race circuit sprint, if its a single lap like most, doesnt justify the width of tyres someone with racing experience might assume.

[Chris Y]

As far as I'm aware, the 'soft' 048 is mid way between the 032's supersoft and soft compounds. I think I got this information from Adams and Page.

The reason for the 048's existence was because the 032 had a cross-pattern tread, which left a 'weak spot' in the middle of the tread, causing some bulging at high speed I believe. The 048 tread is essentially the same, just with the tread pattern looped back, as opposed to crossing in the middle.

[Anuauto]

Both points tend to confirm 048 would be worse than 032 in the wet. I guess we're off thread and should return - which was about widths of List 1a.