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dottydogmk1
19-04-09, 22:30
For some reason my car seems to be destroying its front tyres, this is costing approx 100 per meeting which I cannot sustain. I have attached a pic (I hope) of the front right after three ascents of Loton. I run at 26 psi 1.75 neg camber, tracking dead ahead, car weighs 815kg, 7.0 x 20 tyres on 6" rims. Has anyone tried yokohama slicks? I just can't keep funding the avons unless anyone can tell me whats wrong. Any thoughts/ advice greatly appreciated!

Radical
19-04-09, 22:53
Put simply you are running too soft a compound.

My Radical used to be similar with A40 / A91 so I changed to A15 and felt no real reduction in grip, but the tyres now last most of a season.

26psi seams a lot, but your car is much heavier.

No personal experience of Yokos but anecdotal word from people who have changed from them to Avons and imeadiately found seconds improvement.

I would also recommend going wider if you can as 6" wheels are quite narrow for such a car, pehaps 8" tyres on 7 " wheels?

Bunman
19-04-09, 22:55
What compound? They look to be too soft for a saloon, I use A15 2553 (stiff wall) on my mk2 and that is about as soft as I would go.
Do you think you could squeeze 8's in under the arches ?

dottydogmk1
19-04-09, 23:04
Thanks for the quick replies, they are A15 compound and I am on the limit for wheel arch clearance. I ran 7.5's last year (as advised by BMTR) and had worse trouble some of which was due to clearance problems.

Bunman
19-04-09, 23:21
I would go for a slightly harder compound then , I run 9" tyres on 10" rims but I don't run standard arches. It looks like you are getting a lot of movement in the tyre maybe from the rim/tyre size difference, is there any way you could run a wider rim with the same tyre??
Pressure and suspension are fine, I run between 22 and 26 depending on the weather conditions.

CNHSS1
20-04-09, 10:26
my thoughts...

too much pressure, id be looking at 20-22psi hot (16-18psi cold to start)
too wide a tyre or narrow a rim, 7.0 id run on 7.5" wide rims.
too much camber, .5 to .75 deg neg camber, 1 deg max.

i suspect the 6" rim is causing the sidewalls to 'parrallelogram' allowing the tread area to shift side to side on the rim, no amount of sidewall stiffness will stop this. a wider rim (albeit at odds possibly to circuit racing thinking) will give the sidewalls a slight angle compared to the tread giving some mechanical stiffness to the carcass. i suspect your extra pressure is needed to stiffen the carcass but isnt actually helping the tyre do its job.

i run A15s on my car (circa 800kg) and have no problems with the compound although tyres are wider (8.7 fr, 10.5 rear)

Martin.G
20-04-09, 10:55
Much of what you are seeing is pick up. Take a heat gun and scraper to them and you will be back to a good tyre. Loton probably works tyres harder than most hills.

PaulR
20-04-09, 13:00
The camber seems excessive, and the (I presume) outside of the tyre doing no work sort of supports that.

And perhaps a 21" tyre would be more versatile on a narrow wheel on a saloon?

Paul

dottydogmk1
20-04-09, 19:54
Thanks for all the thoughts, I have tried running lower pressures and less camber but this caused lots of understeer - it is the inside of the tyre which is not doing anything so I don't think camber is an issue, Martyn Pike certainly runs a lot more than me on his mk1. I think you are all right about the rim width causing a problem but I simply don't have room to go any wider with the standard arches. Excuse my ignorance but would a heat gun not make the compound go harder?

YingYingVroomVroom
20-04-09, 20:11
Hi Dirty Dog 1,

In your picture which is the outside edge of the tyre? I suspect it is the left hand side of the tyre. Please advise.

YYVV

dottydogmk1
20-04-09, 20:49
The left hand side as you see it is the inside - I always get a build up of rubber here which I suspect has come from the rest of the tread, I am pretty sure its not pickup as it is so consistent.

jedi088
20-04-09, 22:47
That tyre looks like it will clean up with the hot air gun scraper routine and be useable again . If you fit the same size tyre on the wider rim with the correct offset you might find you have more clearance in the wheel arch rather than less available . Can you borrow some wheels of the correct size and give it a try .

dottydogmk1
20-04-09, 23:01
Believe me, there is no room for wider rims - at present my springs are nicely polished and the inside of the arches are black! I am still abit confused about this hot air gun routine, is it not giving the tyre another heat cycle effectively? I presently clean them with a surform which takes up to 3 hours for the set and kills my back!

Radical
20-04-09, 23:16
The 7 inch tyres would surely stick out less in the side wall on 7 inch rims.

Not keen on the hot air gun, tried it once, I have generaly used the sureform, remembering to use plenty of water and a drop of soap (fairy liquid) to cool and lubricate the blade.

The best I have seen though is using a plane, but it has to be extra sharp and will need resharpening regularly.

blackx
21-04-09, 00:53
I know of someone who used an angle grinder to clean his tyres up :eek:

I kid you not.....

rescuedude will confirm this as he heard me talking to the driver just after he had a moment in the Esses at Prescott ;)

SteveSlowboy
21-04-09, 08:36
I use a heat gun with scraper to clean the tyres. yes, it does heat cycle them but no idea what effect this has in the long term. it cleans them up nicely though and is a lot easier than planing / surforming. I haven't seen any ill effects from this method.
Steve

PaulR
21-04-09, 08:48
The hot air doesn't heat the tyre, it heats the blade of the scraper and helps to separate the tyre from the crud.

There's still a contradiction about inside and outside. FWIW.

Paul

mx125
21-04-09, 08:51
I know of someone who used an angle grinder to clean his tyres up :eek:

I kid you not.....

rescuedude will confirm this as he heard me talking to the driver just after he had a moment in the Esses at Prescott ;)

I know someone as well . He used a little grinder with a 4" disc could it be the same person blackx ?

blackx
21-04-09, 09:00
Nah.....This person used a 9" angle grinder :eek:

jo white
21-04-09, 09:06
Nah.....This person used a 9" angle grinder :eek:

Whats wrong with using a petrol one !!!

carl talbot
22-04-09, 22:44
I'm basing these comments on your title picture of an Escort [ rolling quite heavily into a corner ! ] ?

From experience of [relatively] heavy front engined saloons/sports cars :

You should not run tyres wider than the rims !! preferably 1/2" narrower

Looking at the picture of the tyre , you are not running enough camber - the scrubbing , though excessive in your case , is normal , But should come completely to the inside edge of the tread and the rolls of rubber will be hanging off the inside ,
ie you are not using all the tyre - partly because the tyre is too wide for the rim and rolling excessively and also because of lack of camber .

It also looks like the outside edge , beyond the tread is scrubbing .

I have successfully run 2 1/4 - 2 1/2 deg. Camber with Avons on front engined saloon.
Another thing to bear in mind is that if your car is lowered and also rolling into corners , with Mac. strutts you don't get any Camber gain

If you increase the Camber you could probably increase the outside rim width , to give yourself 7 1/2" rims .
This will stretch the tyre , and with the increased camber [ pull in the top strutt mts., rather than increasing length TCA's ] this will give clearance to the arch

Have you felt the tyre temp across the tread width at the end of a run at Loton ?

Try the above mods before going for a harder compound , though this may be necessary if the tyres are still getting too hot

Ideally you would want 8" tyres on 9" rims , [Stretched Mexico wings ?! ]

Are you using 2 1/4" springs and adjustable platforms ?

dottydogmk1
23-04-09, 18:40
Hi Carl, thanks for those wise words - all your assumptions are correct and this wheel width issue seems to be a common theme on most of the replies I have had. Tyre widths were chosen on advice from BMTR and the previous set were slightly wider and hence suffered even more. I am running 2 1/4" springs on adjustable platform bilstein struts and I have pulled in as much camber and castor as I can using eccentric top mounts. Clearance is still tight as they are standard Escort wings (not even Mexico). You are also correct in saying that it is scrubbing the outside of the tyre - to the extent of scuffing the tops of the Avon letters! Looks like the only proper solution is to arch it, something I am reluctant to do. It does however run pretty well on Yokohama A048 185/60 soft tyres (about 1.6 seconds slower at Loton) with no abnormal wear patterns hence my question about the slick version. Also, would a radial construction help? Thanks again, Steve.

carl talbot
23-04-09, 23:20
Ignoring the constraints of your top mounts , is there any clearance between the vertical part of the inner wing/strutt turret and the strutt top/top spring retaining collar so that you can gain some camber by fabricating suitable top mounts [ they don't need to be pretty , just to try it ]
might save you arching it ?
Again , based on your signature photo , you could look at transfering some of the work that the outside front tyre is doing

dottydogmk1
24-04-09, 22:22
I have about 25mm clearance between the spring and inner wing but can gain about 1/2 a degree by lengthening the TCA's I think. I will have to get some tyres soon so wondered if 19.5 profile may help. Carl, I would love to have a chat about the handling issues on my car so would it be possible to PM your number with a convenient time to ring. Thanks, Steve.

John Lloyd
26-04-09, 23:06
I used the Yokhama slicks last season to win my category in the French national championship last year. I changed from Avon A15's and found the Yoko's just as good if not better as they appeared to be more progressive, they also stayed-in better towards the end of the longer 5 km hills where the A15 would start to overheat.

They are a compound intended as a circuit single seater wet and are available un-cut.

Another advantage was the price, they were about 40% cheaper than Avon, amazing really as they are made in Japan and shipped half way round the world!

Despite the width being sized in centimetres they are actually a crossply.

I'm no expert on Escorts but 1.75 sounds like quite allot of camber to me for a crossply to cope with?

carl talbot
28-04-09, 09:36
I used the Yokhama slicks last season to win my category in the French national championship last year. I changed from Avon A15's and found the Yoko's just as good if not better as they appeared to be more progressive, they also stayed-in better towards the end of the longer 5 km hills where the A15 would start to overheat

I'm no expert on Escorts but 1.75 sounds like quite allot of camber to me for a crossply to cope with?


Would the Yoko's get to working temp on British hills ?

Generally yes , but it is relative to what the tyre is actually 'seeing'

carl talbot
28-04-09, 09:37
I have about 25mm clearance between the spring and inner wing but can gain about 1/2 a degree by lengthening the TCA's I think. I will have to get some tyres soon so wondered if 19.5 profile may help. Carl, I would love to have a chat about the handling issues on my car so would it be possible to PM your number with a convenient time to ring. Thanks, Steve.

PM sent
Carl

John Lloyd
28-04-09, 09:54
I found that the Yoko's worked well from cold, I used them also on some of our short 1.5km hills and they were just as impressive.

Results speak for themselves ...out of 11 events last year my Yoko's won 9 times and second twice, the classes were not small, sometimes as many as 16 cars.

I should add that we are not permitted to pre heat or spin the wheels up (only if someone is looking).

Sounds like I am trying to sell Yoko's .... perhaps I've missed a trick there ?

dottydogmk1
28-04-09, 18:46
John, thats very interesting - you are the first person I have heard that speaks in favour of the Yokos. What are the details of your car? i.e type , weight, rim and tyre widths and suspension settings. Thanks, Steve.

John Lloyd
28-04-09, 20:34
Caterham. K-115bhp
515 kg
6" rims. Tyre 160x515x13 code 2264
Presure 21 psi hot.
Rear camber 0.25
Front camber 0.50
Rake rear to front 12mm

maycontainNUTS
29-04-09, 06:03
John, thats very interesting - you are the first person I have heard that speaks in favour of the Yokos. What are the details of your car? i.e type , weight, rim and tyre widths and suspension settings. Thanks, Steve.

He's being too modest - it's not the tyres that do it, it's talent :)

I've seen him manage ridiculous feats rallying when the only tread left was steel showing :p

redturner37
29-04-09, 18:01
He's being too modest - it's not the tyres that do it, it's talent :)

I've seen him manage ridiculous feats rallying when the only tread left was steel showing :p My thought as well Neil, but didnt comment because I didnt want to listen to him making speaches for the next 4 weeks.....

dottydogmk1
29-04-09, 22:25
He's being too modest - it's not the tyres that do it, it's talent :)

I've seen him manage ridiculous feats rallying when the only tread left was steel showing :p

Looks like I will have to stay with Avons then!

John Lloyd
29-04-09, 22:49
Darn it ... there goes any chance of back-hander from Yoko!:p

Neil ... with reference to the tyres worn down to the steel ...I seem to remember you were the one daft enough to be sitting in the co-pilote seat at the time:eek:rolleyes:
Was that the day we ran wide and smacked in to the side of Treve Dunstan's BMW at 120 mph on the 1989 Tour of Cornwall rally?:eek:

maycontainNUTS
30-04-09, 08:01
Don't know - I had my eyes shut at the time LOL :(