Tyres - What influences 'grip' the most? - Page 2

graham bahr · 2 Dec 2005, 11:15 (Ref:1475541)

Quote:

Originally Posted by retro_msport

I set a sprint car up with the temp probe, the driver went out and did a run and came back complaining the car was undriveable, very loose, horrible etc and asking what i had done to make it so bad, untill his brother came back with the time, 3 seconds better than his best time ever.
Next event he had returned his car to his "cast in stone" settings and the time gain was gone... but the car is nice to drive

As for me wanting to tweek his rear axle to give some camber and toe in....
"you want to bend my axle... are you mad"

.

some people you cannot (or maybe shouldn't) help!

retro_msport · 2 Dec 2005, 11:22 (Ref:1475547)

Quote:

Originally Posted by graham bahr

some people you cannot (or maybe shouldn't) help!

The car, a mk2 escort 2L ohc 4speed and english axle with tarmac arches, is still running 7-8" wheels, i've been trying to get him to goto 9's or 10's for two years, with the soft hillclimb slicks, he wont, so i've told him i'm bringing some Fiesta 135/70/13's with me, Hes got that thing stuck in his head about being "overtyred"

I'll have him on the wider rubber soon, even if i have to hit him over the head and change wheels while his sparko

graham bahr · 2 Dec 2005, 17:21 (Ref:1475832)

its difficult to over tyre a sprint car as they never normally get any heat into the tyres in the first place, so basically the wider the better, circuit racers are another matter they have time to get heat in tyres so it is quite possible to overtyre them.

that said if i set someones car up and it went faster, if they then put the settings back to slow, then i think id give up with them, as they are waisting everyones time

greenamex2 · 2 Dec 2005, 17:31 (Ref:1475837)

Interesting comments about rim widths versus tyre widths. I was unable to get the right width tyre for my wheels and had to get the next best thing for which the rim was slightly too wide for. It was the 'firmest'/best the sidewalls had ever felt, the only disadvantage was the car was slightly over geared.

Funnily enough I have also noticed that the fastest Peugeot 205's in our series ALSO have a discrepancy between tyre size and rim width. I wonder why!

So, do you go for a slighty wider tyre, or a narrower tyre stretched across the rim (given that I am on restricted rim widths)?

graham bahr · 2 Dec 2005, 18:25 (Ref:1475887)

assuming i wasn't restricted on rim size i would rather go for tyre a bit too narrow rather than a bit wide,

what rim sizes and Tyre options are open to you denis?

Al Weyman · 2 Dec 2005, 20:51 (Ref:1475974)

Quote:

Originally Posted by Denis Bassom

Al, when people have gone to bigger diameter wheels have they also increased width and/or outside diameter and/or reduced tyre profile?

I have a similar dilema with my kit car at the moment. I am leaning towards using current 'standard' size tyres just to future proof the expenditure on new wheels.

Yes they did use a wider lower profile tyre but this was on the heavier cars more powerful cars.

I can give you two incidents where it did not work, one guy had a Mk11 Escort and turned up with monster 17" wheels and lower profile 'rubber bands' and the thing went slower than when on 15 inch riubber. Likewise a guy turned up with monster rubber on a Rover GTi to try to get some front end grip and that did not work nor the other guy who turned up with a Turbo Maestro and Carlo Fandangos fitted, looked stupid and did'nt work!

Al Weyman · 2 Dec 2005, 20:56 (Ref:1475980)

I agree with stretching them on a wider rim, it stiffens things up I have found, I think that was why my 275 x 50 x 16 worked well.

retro_msport · 3 Dec 2005, 10:51 (Ref:1476223)

A capri driver in classic touring cars was complaing of understeer, I told him to loose the 215's (think he was on them) and go 205 or even 195, he said he needed more grip not less .. but when i bumped into him at Lydden he patted me on the back and said cheers for the advice.. took a look at his car later .. yep 205's.

Graham... i cant give up on said sprinter... hes got it in him, he just thinks too much, very bad thing for a driver

retro_msport · 3 Dec 2005, 10:58 (Ref:1476227)

Quote:

Originally Posted by Al Weyman

Yes they did use a wider lower profile tyre but this was on the heavier cars more powerful cars.

I can give you two incidents where it did not work, one guy had a Mk11 Escort and turned up with monster 17" wheels and lower profile 'rubber bands' and the thing went slower than when on 15 inch riubber. Likewise a guy turned up with monster rubber on a Rover GTi to try to get some front end grip and that did not work nor the other guy who turned up with a Turbo Maestro and Carlo Fandangos fitted, looked stupid and did'nt work!

Going too small on sidewalls and you can loose the springing medium of the tyre, and get the same effect of being to stiff with the springs/dampers. I've always found that a stretched tyre with a decent profile works best.

graham bahr · 3 Dec 2005, 11:03 (Ref:1476230)

one problem with rubber band tyres is that unless your suspension can keep the tyre perfectly flat against the road (and few production cars dont suffer from camber change with suspesion movement) the lack of sidewall can easily mean you end up with LESS rubber on the road as the suspension moves away from its static position

retro_msport · 3 Dec 2005, 12:40 (Ref:1476264)

Graham, funny how things happen... said sprinter has just walked into the workshop

and has just read this....

Terry Donovan says hi... ( Electric Blue Mk2 in D11)

graham bahr · 3 Dec 2005, 13:10 (Ref:1476272)

yeah i remember the one, flat front with a pinto in it, doesn't he do artwork or somint,

tell him hi.

**Peter Mallett** · 3 Dec 2005, 15:24 (Ref:1476323)

Quote:

Originally Posted by retro_msport

A capri driver in classic touring cars was complaing of understeer, I told him to loose the 215's (think he was on them) and go 205 or even 195, he said he needed more grip not less .. but when i bumped into him at Lydden he patted me on the back and said cheers for the advice.. took a look at his car later .. yep 205's.

The CTCRC run a specific tyre which is Al's complaint) and so the sizes are limited. I run the "Capri" Dunlops (I think they're 205's) and you have to set the suspension up properly for them to be effective. 185s (as we used to run) go off too quickly.

Even with those tyres and a good "legal" set up (in other words no additional linkages etc.) you will get understeer so the secret is to set the car up properly for the corner and unless you race every weekend (something that my job precludes) it takes a good while to get into that groove.

retro_msport · 3 Dec 2005, 15:53 (Ref:1476334)

Quote:

Originally Posted by graham bahr

yeah i remember the one, flat front with a pinto in it, doesn't he do artwork or somint,

tell him hi.

Yep he does the cartoon auto's ... hence the ones on my logo

And Peter... The capri in question was on 215's i'm sure, and it had all the classic signs of tyre tuck, rub off name etc, the 215's are just to wide for the control rim. Think he came 2nd to your Capri at Lydden , may be wrong, as i was under an escort for most of your race. Mark Fowler is his name

**Peter Mallett** · 3 Dec 2005, 16:27 (Ref:1476347)

Yes I know Mark but I wasn't at Lydden. (Not doubting you BTW).

The 205's can roll too if you don't pressure them properly but its really in the set up and he runs adjustable TCA's which adds a weight and geometry problem. I run with standard TCA's but fully adjustable top mounts. Saves weight at the bottom and gives better adjustment. But the camber and castor are very important.

You can see the amount of camber on this pic. http://www.mallettracing.co.uk/IMAGES//spa2003_1.jpg

retro_msport · 3 Dec 2005, 17:04 (Ref:1476359)

Yeah I also told him to ditch the adj TCA's ... i personally think they are a waste of time... adjust camber adjust tracking...

Thought i saw your car at Lydden... well i'm sure there was a red and white car out there... may have been a SD1 though.. eye sights not what it used to be

Al Weyman · 3 Dec 2005, 18:32 (Ref:1476394)

I really do question the virtues of running a control tyre in championships like CTCRC and Toyo ModProds where there is a waste array of cars of different powers and weights, I mean just how can one tyre cover the whole range. I can see some benifits in a control tyre especially if the manufacturer is generous like Toyo but as far as the Dunlops are concerned ahving to run those for no payback ir concessionary prices is quite frankly a little disappointing.

retro_msport · 5 Dec 2005, 01:39 (Ref:1477068)

Quote:

Originally Posted by Peter Mallett

Yes I know Mark but I wasn't at Lydden. (Not doubting you BTW).

The 205's can roll too if you don't pressure them properly but its really in the set up and he runs adjustable TCA's which adds a weight and geometry problem. I run with standard TCA's but fully adjustable top mounts. Saves weight at the bottom and gives better adjustment. But the camber and castor are very important.

You can see the amount of camber on this pic. http://www.mallettracing.co.uk/IMAGES//spa2003_1.jpg

Just out of interest Peter, do you run any toe/camber at the rear... pm me if you want

Al Weyman · 5 Dec 2005, 09:08 (Ref:1477194)

Hey I know some of you guys bend live axles for camber and toe at the back but is it really a good idea, I certainly dont fancy it with the Chevy C Clip half shaft location which at best is marginal especially when pumping a few hundred horses through them, each to there own but is it worth compromising safety and reliability. Also is'nt there something in most of these type of saloon regs (I know there is in ModProds because I wrote them) prohibiting alteration of the axle case. Maybe I am just being a little nieve here and this is why some seem to go a lot faster than others using 'standard' kit.

retro_msport · 5 Dec 2005, 10:23 (Ref:1477236)

Al, just out of interest... could you pm or show the rules from Mod Prod here... just like to see what was said on back axles.
With the Salisbury and Timkens axles (atlas, english) that i've errmmm tweeked we have never had a problem, I take it your saying that your shafts are held in by a 'C' clip... not the 4 M8 bolts like on the common Ford axles

graham bahr · 5 Dec 2005, 10:44 (Ref:1477257)

thats right, the C clip axles have there half shafts held in buy a C clip at the diff end, i couldn't believe just how little held them in when i first took one to bits,

i seem to recall that they are so poor they are banned in certain racing circles, drag racing i think

retro_msport · 5 Dec 2005, 11:03 (Ref:1477286)

Quote:

Originally Posted by graham bahr

thats right, the C clip axles have there half shafts held in buy a C clip at the diff end, i couldn't believe just how little held them in when i first took one to bits,

i seem to recall that they are so poor they are banned in certain racing circles, drag racing i think

A bit like a drive shaft then... thinking of 300 brake RST's

graham bahr · 5 Dec 2005, 14:43 (Ref:1477425)

Quote:

Originally Posted by retro_msport

A bit like a drive shaft then... thinking of 300 brake RST's

no worse, if a chevy c clips fails theres nothing to stop the half shaft from coming all the way out complete with hub, brake drum, wheel etc,

3 wheels on my wagon comes to mind

greenamex2 · 5 Dec 2005, 17:11 (Ref:1477516)

Not to mention whatever ever else get's 'shafted'.

Sorry, it's late.

retro_msport · 5 Dec 2005, 19:29 (Ref:1477626)

Quote:

Originally Posted by graham bahr

no worse, if a chevy c clips fails theres nothing to stop the half shaft from coming all the way out complete with hub, brake drum, wheel etc,

3 wheels on my wagon comes to mind

Which is why i like steel arches... holds things in

I can see your point... do they fail a lot then these C-clips? I'm not all that up on the american axles, picked up and fitted a few 9" in my time, but they have only been 24" wide and still twice the weight of an Atlas and i'm getting far too

to be picking them up.

Ive only seen one Atlas loose a shaft and that was on a rally car

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