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Tyre Width Vs Available Grip - Are Wider Wheels Beneficial On A 205?


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36 replies to this topic

#1
SweetBadger

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Hi, after a fairly quiet one last year (not to mention unreliable) we're getting ready for the new race season in the 205.

 

We've always run standard 1.9 wheels with 195 50 r15 yoko A048 tyres, but we have to change to Toyo R888R or R888 this year due to the regs for the championship we're entering so we're also considering some new wider wheels.

 

I know there are benefits to reducing un-sprung weight and getting lighter wheels would help out with the handling, but I'm less sure about the benefit of going wider especially on a light car like the 205.

 

On a very basic level increasing the tyre contact patch doesn't necessarily increase grip as the pressure on the contact patch decreases correspondingly, but I know it's nowhere near as simple as that (slip angles, tyre deflection, temperature, wear rate all change) !

 

So to give a specific example would there be much benefit from moving from the standard 6J wheels with 195 width tyres to:

 

- 7J wheel 195 50r15  tyre

- 7J wheel 205 50r15  tyre

 

Anyone have any experience?

 

It's a challenge to fit a wider wheel / tyre on our car at the mo as we run the wide body Gaz coilovers with -3 degree camber up front, so have to use a 10mm spacer just so the tyre clears the damper body.

 

I think fitting a 7J wheel with a 205 width tyre would mean we'd also have to fit wider arches too as the tyre would stick out beyond the standard arches, so I'm tempted to go for a set of C5 steelies and continue with the 195 50 r15 tyres unless there's proven benefit to running the wider tyre.



#2
Anthony

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I can't answer the wheel width question, but regarding the C5 "steelies" I would look into how brake cooling might be impacted compared to a more conventional alloy wheel. Certainly I know that some people have complained about fade issues on track cars when running C5 wheels.

#3
dcc

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Wheels and 205 tyre width depend on offset, the extra width will ofcohrse improve your traction. I think Wardy touched on wheel width when he wrote his build thread. Also Matt180 has a ver good build thread regarding widening the wheels on a 205, whole new arches and inner arches

#4
steve@cornwall

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Would tyre profile also be worth considering? Higher profile being less rigid and maintaining more grip?

#5
petert

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7J wheel 205 50r15  tyre

I use to run this setup. It works with a +5mm offset wheel. I've since moved on to 8J with 205 50r15  tyre and it's better again, due to less side wall flex. Most recently, we went back to a C5 wheel on the rear with a 195 50r15 in soft, in an attempt to get the rear heated up more quickly. If I could get a 215 under the front, I would.



#6
welshpug

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wheels are measured in inches not J...

 

typically a 195 road biased tyre works very well on a wheel up to 7" wide, beyond that they get a bit stretched.

 

a competition tyre is a bit different and we have run 180 and 200 wide on a 7" rim.



#7
blandy

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alot of the motorsport boys are running 205/50/15 Ad08 r888 and dz03's on 8" and 8.25" widths - purely down to cost and availability.

#8
Batfink

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The contact patch changes. Wider tyres will give more lateral grip, thinner longitudinal. But overall on track the wider tyre has a greater cornering benefit to a point.


Edited by Batfink, 03 February 2017 - 12:36 PM.


#9
Miles

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You want at least a 7" wide rim, you can get 8's on with bringing the front wings out if aloud, rear's are tight but does fit, These C5 rims are to narrow and in real terms gain nothing in my book



#10
SweetBadger

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Cheers for the info guys will start looking out for some suitable 7 inch wide rims.

 

Currently run standard wheels (et19) with a 10mm spacer; effectively ET 9. The 205 width tyre will add approx 5mm per side, so as per petert's earlier post I'll need an ET5 wheel. 

 

Team dynamics pro race 1.2s look like a good option but have a min offset of 10, so if we go for them it'll be best to get the et14 version and then continue running the 10mm spacers.

 

I'll also need some wider arches as even with the 195 50r15 tyres the outside of the tyre is flush with the standard arch at the front, and won't go in any further due to the -ve camber and large body coilovers.

 

I spoke to Miles about it yesterday when picking up the car after having some gearbox work done. The Euro Rallye style arches might work as they are wider than standard, or there's the option of pulling the wing out, or a combination of the two!

 

Would rather do the Euro Rallye style arch as it was a standard 205 arch, think wider aftermarket arches are not allowed in the regs for our race series, and pulling the wing out might be pushing it with the regs too. Anyone given these a go? :http://www.ebay.co.u...sd=140721765588

 

Thanks, Alex.



#11
dynacord

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If your car has enough power, then go for 205/50 - more rubber, more traction, but the tyre is heavier. R888 in 195/50/15 is 8.8kgs,  

I've been running 195/50/15 R888 for years without rubbing, on 7 inch, ET18 with standard arches (with 309 bones and xsara arms at the rear, apprx. 9mm wider per side) The wheel sits just flush with the arch. 

Some tyres are more square than others, too. 



#12
SweetBadger

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What about 14 inch wheels with 205 55 r14 tyres.

 

The wheels would be lighter, but the tyre would have a higher wall - not sure if that would be beneficial or not.

 

We run 266mm brakes so the wheel would fit, and the diameter would be the same as the the 195 50r15 (205 50r 15 would increase the diameter and effectively lowering the gearing which is not ideal).

 

Edit - not an option anyway R888Rs are not available in that size.


Edited by SweetBadger, 08 February 2017 - 09:23 AM.


#13
welshpug

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what kind of times are you doing round brands hatch?

#14
SweetBadger

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Don't have any times for the new car round brands. Only times from last year are as follows:

 

Cadwell Park: 1:43.854

Snetterton 300: 2:16.64

Silverstone international: 1:20.78

 

All dry on yoko A048s (195 50 r15), standard 1.9 alloys.

 

Both Snetterton & Silverstone times were from qualifying; the clutch died early in both races so was probably a quicker time to be had!

 

Have since installed Bridgecraft -ve camber trailing arms (-3 degrees), and a chunkier arb so would expect some improvements this season.



#15
petert

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If you have to buy new wheels don't muck around with 7". Go straight to 8", et -4.

#16
welshpug

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Im not sure tyres will make that much difference yet, youre only a few seconds ahead of stock hatch lap records, i.e 90 bhp saxo vtr's etc.

#17
SweetBadger

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So we're faster than stock cars... well that's a relief! No doubt the driving can improve, but a few seconds is a lot round a circuit!

 

We're always quite competitive, the qualifying times were 3/4 in class against some much more exotic machinery, so if we can find half a second or more by fitting better wheels/tyres it can't hurt.

 

Don't think there's much more that can be done with the suspension / chassis now without spending a lot more.



#18
SweetBadger

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Peter, the approved width for the tyres we have to run (toyo R888R) is a max of 7.5 inches (ideal shown as 6.5); not sure if it'd be a good idea to go to 8 inch wide wheels.

 

Is that the same for the 205 width tyres you run on the 8 inch rims? 


Edited by SweetBadger, 08 February 2017 - 07:41 PM.


#19
welshpug

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sounds like some 6.75" sl434's would be ideal, lots of brake space then.
how restricted are you with suspension within the regs?

#20
petert

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Yes, we run 205x50/15 A050 or 200x580 slicks on 8". The tighter sidewall is a vast improvement over 7".