Tyres- advice please

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Nick
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Tyres- advice please

Post by Nick » Mon Feb 14, 2011 4:17 pm

My 1A Toyo Proxes T1R tyres are now 3 seasons old and I am thinking of changing to 1B tyres. I would appreciate other competitors advice /experience. :w

What make(s) perform best? I currently use 205/50/15's I would probably stay with these, Chris goes faster than me on 195's, but I do not want to lower the gearing.

What is the difference in driving on 1B's? Presumably more grip, but more or less feel? How are they in the wet compared to 1A's?

Will the car set up need changing? Currently set up fairly stiff, but generally well balanced.


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Re: Tyres- advice please

Post by shrewsbury_streetracer » Mon Feb 14, 2011 8:06 pm

Hi Nick,

I use the R888 soft's. They grip far better. Watch out first time out though as I hadn't scrubbed them in enough prior to my first event last year at Loton and shot off on the first corner!! You don't have any tyre squeal which I used to use as an 'on the limit' pointer so be aware. All in all I found them very good. I felt I gained more time than I lost in the penalty formula and the car realises it's full potential. I made no changes to the set up (maybe I should have) and felt it maintained it's previous balance.
I took mine off at the end of the season (to put them into hibernation) and I'm sure they have at least another full season left in them.

205's are greatly more expensive than 195's....this is why I run 195's :D

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Re: Tyres- advice please

Post by CNHSS1 » Mon Feb 14, 2011 8:11 pm

1Bs are a pure competition tyre, much much stiffer sidewalls and generally less tread area, along with stickier rubber compounds.
In an ideal world, purely for sprints/hills look for tyres with high silica content, this makes the rubber work better at low temps i.e. from cold, although for a trackday or circuit racing, high silica is best only for wet racing.

knowing your car Nick, i suspect the springings about right, although you may need to up the damping rate due to the much stiffer sidewalls.
Interms of 195 or 205, generally this will be lead by your choice of preffered tyre, as its most likely the manufacturer wont do all the compounds in both sizes, so the tyre choice will dictate the size.
As an aside, if you check the motorsport spec sheets of 1B tyres, they usually show the tread width and the rolling radius, rolling cicumferenace or revolutions per mile. Often the main difference between 195/50-15 and 205/50-15 is the rolling circumferance which as you say affects the gearing, whereas if you check the 'tread' width they will be 2-3mm difference. Often the narrower tyre will have slightly rounded shoulders to the carcass which may aid arch clearance if you are on the limit.

Ive always used a tyre which is on the limit of the max for the tyre as this stretches the sidewalls and gives a bit of mechanical stiffness to the tyre (not as important with 1Bs to be fair), but i ran my 205/50-15 Kumhos on the front of my racer on 8.5" rims, but probably should have run 9" actually.
Too wide a tyre or too narrow a rim, and you can feel a little 'transition' as the sidewalls move as a parallelogram, which makes the car slightly wooly on turn in.

Tyre pressures are differnt too. On 1A's generally you run extra pressure than the road to keep the carcass stiff under heavy cornering. We all seen pics of tyres almost coming off the rims on road cars (and all American cars :roll: ), but the super stiff sidewalls makes that unnecessary. I used between 18 & 20 psi on the Kumhos, dependant on track length and ambient temp.

With regards to the gearing, i suspect you are using a 3.9 diff ratio same as me? Chris and some of the other guys use 3.62 which means they can easily use the 195/50 diameter tyres and still use 1st!
when i ran Avon ACB10 List 1Bs which were imeprial sized (7.0/22-15 iirc) they worked out to 195/45, so with a 3.9 diff i only used 1st for tyre warming and started in 2nd gear. Needs a few more revs on the clock, and sidestep the clutch and be ready to dip it if it starts to bog (shouldnt if you keep enough revs on to keep them slipping slightly). Its basically the equivalent of a Quaife or BGH Type 9 Ford 'box with long 1st, which is std practice in most LoCaterFields and Escorts etc. It also means that places like Loton, Curborough and Prescott you pretty well half the amount of gear changes per run! Thats worth a 1/10th at least per change and reduces the chance of a mis shift too. I suspect your cars power spread is good enough to pull it too :wink:


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Re: Tyres- advice please

Post by nickkeyser » Mon Feb 14, 2011 11:08 pm

I too took the plunge from Toyo T1R's to R888 softs this season.

The differance is amazing, allowing for what feels like un-natural cornering g-force compared to anything ive experianced on the road.

I too run 195/50/15s but with a cvh, so its all a bit different.

I would say to choose the tyres, get them on the car and give it a go - I havent touched the suspension either and get on fine with a very soft setup. All i did was up the damping. I do intend on stiffening it up, but felt that doing it all at once would be changing too much in one go. No matter what springing its going to feel like a giant change.

As has been said, they dont complain, and then suddenly let go.... not to the same extent as slicks but they certainly can take you by surprise... :roll:



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Re: Tyres- advice please

Post by Nick » Wed Feb 16, 2011 6:51 pm

Guys,

Thanks for the detail feedback-most helpful :D

I will make some enquiries on prices. Any ideas? Also who will fit cheaply? ( Local to Redditch). I presume we go for the softest version?

Any feedback on wet performance :?

Criag's comments on using second to start are interesting.... I have to use only 2000revs off the line and "pop" the clutch in first, any significant wheelspin is timewasting.


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Re: Tyres- advice please

Post by CNHSS1 » Wed Feb 16, 2011 9:27 pm

imho its all about the compound for sprints/hills, as for the first few corners there will be no heat in them and they will only really be warm towards the end of the run. The softest of the soft are the way to go for pure performance but they are no good for road miles of course.

i defo think a back to back test with regards revs and starting gear at a test day would be interesting. Maybe someone stood at 64ft line off curbs start with a stop watch and back to back runs?

another thing with 1Bs is that they benefit from some wheelspin off the start and slip angle in the corners to sort of 'activate' the compound. Although its a bit of a leap of faith after 1As, you do need to lean on them in corners and they will grip! Again a morning at a test day will see the confindence build, or it will take a few events.


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Re: Tyres- advice please

Post by Coupe Racing » Thu Feb 17, 2011 12:15 am

Camskill good for prices and fast delivery .

I managed a trade discount too

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Re: Tyres- advice please

Post by nickkeyser » Fri Feb 18, 2011 1:48 pm

Nick wrote:Guys,

Thanks for the detail feedback-most helpful :D

I will make some enquiries on prices. Any ideas? Also who will fit cheaply? ( Local to Redditch). I presume we go for the softest version?

Any feedback on wet performance :?

Criag's comments on using second to start are interesting.... I have to use only 2000revs off the line and "pop" the clutch in first, any significant wheelspin is timewasting.
In the wet they were 'interesting' much worse that any road tyre. I usually lug along my T1R's if the weather looks bad, as although they arn't great in the wet, they are a lot better than R888's. but I expect wet performance veries from one make of 1B to another.

As for compound, the R888 is available in 'SG' which is specifically for hill climbing and sprinting, so they are super sticky and soft.

As Steve says, camskill worked out best for me, even compared to demon tweeks with 10% off through their sponsorship scheme. Talk to them nicely, and you can usually wangle a deal.



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Re: Tyres- advice please

Post by Nick » Fri Feb 18, 2011 2:56 pm

Yes, I had a look at Camskill.

195's look like £108 ea
205's £ 120 ea,

I get the vibes they might do a deal

All plus delivery and fitting. I looked at 195/55's but not available in the soft compound. Presumably no wider overall than the equivalent T1R :?:


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Re: Tyres- advice please

Post by Raz987 » Fri Feb 18, 2011 4:13 pm

Nick wrote:Yes, I had a look at Camskill.

195's look like £108 ea
205's £ 120 ea,
Holy crap they've gone up a lot! The last time I bought R888's they were £65 a corner...


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Re: Tyres- advice please

Post by nickkeyser » Sat Feb 19, 2011 1:45 pm

Its worth noting that an R888 is a lot squarer than the same size T1-R so the contact patch is a lot larger.

I fitted 195-50-15 R888's on identical wheels (15x7 ET25 BBS) in place of the identical size 195-50-15 T1-R's before curborough, which required a bit more arch pulling to get them in the rear, and the fronts fouled the inner arch at the back against the tub where the T1R used to be fine. The fix was to remove the 10mm wheel spacer that enabled the original 14" wheels to clear the metro vented calipers as supplied with the GW vented setup. They cleared fine after that, with the added bonus that removing the spacer also improved turn in noticably.

My set of 4 came in (just) at less than £400 delivered, I think that was around about July 2010.



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Re: Tyres- advice please

Post by CNHSS1 » Sat Feb 19, 2011 2:33 pm

nickkeyser wrote:Its worth noting that an R888 is a lot squarer than the same size T1-R so the contact patch is a lot larger.
yep, hence my comments re getting the spec sheets that mots motorsport tyres have. i think they just use the road car sizing to give you a rough idea of what size the tyre is, but the spec sheet will give the rolling radius and tread width in mm

http://www.toyo.co.uk/tire/pattern/id/4651

http://www.avonracing.com/road_legal_page.aspx

http://www2.yokohama-online.com/gb/tech ... page=23084

http://www.kumhotyre.co.uk/circuit_racing.php#v70a


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