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Author: Subject: 13" wheels why!
zxrlocost

posted on 12/3/07 at 01:26 PM Reply With Quote
13" wheels why!

ok I understand most prefer 13" wheels on 7 cars and have some valid points.

but Im reading a racer website had they reckon they run 13"x 7 as you can only get 80% of the power down? so it makes it more skilled races etc

would someone like to enlighten me


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scottc

posted on 12/3/07 at 01:40 PM Reply With Quote
but is that 13 x 7 instead of 18 x 9 ?
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Jasper

posted on 12/3/07 at 01:41 PM Reply With Quote
Ohhhh - now you've open a can of worms
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zxrlocost

posted on 12/3/07 at 01:46 PM Reply With Quote
no the biggest they would fit is 15" max and they opt for 13"

infact there probably in the same boat were in with wheel sizes

they use 13"x 7 so they can only get 80% of the power down and make it more competitive.

Im confused forget the can of worms

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Mr Whippy

posted on 12/3/07 at 02:07 PM Reply With Quote
try a set of JCB rear wheels then you'll get all the power down





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scottc

posted on 12/3/07 at 02:18 PM Reply With Quote
okay, so they could run 15 x 9's
which would be 20% wider ???

Don't think I've ever seen any 13 x 9's


[Edited on 12/3/07 by scottc]

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G.Man

posted on 12/3/07 at 02:34 PM Reply With Quote
the difference is in how the tyres/wheels behave on the limits of cornering..

A low profile tyre breaks away less progressively, and also the 13 inch wheel and tyre has much lower unsprung weight..

I went somewhere in the middle with 15's







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Phil.J

posted on 12/3/07 at 02:38 PM Reply With Quote
I think that 13 inch wheels are prefered by most as they visually look so much better balanced on the car, and if you track-day the car there is a load of used racing slicks available in that size for no money.
There are plenty of 13 x 9 wheels around if you look at modular wheels or racing wheels suppliers

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greggors84

posted on 12/3/07 at 02:41 PM Reply With Quote
Whats confusing you?

Is it their choice, is it the control tyre/wheel combo for the championship?

If the latter then I would imagine they do it to keep the cornering speeds down and make the mechanical grip less. This gives more overtaking opportunities and therefore better racing.

If the racer has chosen 13s out of other possible sizes and they are saying they chose them to limit the power they can get down, then im not sure! Maybe they are so quick they want to give everyone else a chance!

[Edited on 12/3/2007 by greggors84]

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Confused but excited.

posted on 12/3/07 at 02:55 PM Reply With Quote
I went for 13" wheels because they are CHEAP!





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zxrlocost

posted on 12/3/07 at 02:59 PM Reply With Quote
they all have to use 13"

its to do with the not getting the power down part

its a bit conflicting

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iank

posted on 12/3/07 at 03:18 PM Reply With Quote
I seem to remember that TVR tuscans raced using tyres that were considered not capable of putting down all the power.

I think they (the championship) did that to make the racing more exciting for spectators - careful throttle control was required else they just smoked the tyres and fishtailed every corner.

Great fun to watch, but caused lots more accidents than otherwise I'd imagine.





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Keith Weiland

posted on 12/3/07 at 03:24 PM Reply With Quote
I would hazard a guess that it would make the racing more even as those who could afford better engines would gain little in acceleration as only a certain amount of power could be used and those who had poorer engines could use more of the available power.
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alister667

posted on 12/3/07 at 05:29 PM Reply With Quote
Well, I recently have become a convert to 13" wheels!
I run quite tall (6.5" wide) 15" on the road, great for cruising, and low profile 15" soft rally intermediates on tracks.
I switched to 13" slicks and took about 4-5 seconds a lap off my times.

If you have a look at my last post on
THIS PAGE you'll see the answer is that the car is much lower to the ground. This along with the lower gearing (helping keep the blade in the right rev range) and the much less unsprung weight made a huge difference to the car round corners.

I suspect the 80% question would apply to the width more so than the radius, as the width of the tyre would have more influence on straight line grip and power delivery.





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cossiebri

posted on 12/3/07 at 06:32 PM Reply With Quote
quote:
Originally posted by scottc
okay, so they could run 15 x 9's
which would be 20% wider ???

Don't think I've ever seen any 13 x 9's


[Edited on 12/3/07 by scottc]



I had 8x13 on the front of my mk2 escort and 10x13 on the rear they were fitted with....205/70x13 they did look a tiny bit stretched though
the car was fitted with a zakspeed bodykit, looked the mutts nuts
If you go to weller they do almost every size/option you could think of and a few you couldn't









If it doesn't fit MODIFY it!!
Cheers BriF

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cossiebri

posted on 12/3/07 at 06:42 PM Reply With Quote
This..........................









If it doesn't fit MODIFY it!!
Cheers BriF

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alister667

posted on 12/3/07 at 08:44 PM Reply With Quote
Wow! That is a nice Mk2! Those are fetching silly money (in Ireland anyhow).
Assuming it had all the right bits, you'd be looking at £50-60k.

If I won the lottery......





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wacomuk

posted on 12/3/07 at 10:44 PM Reply With Quote
wheel size affects your acceleration and top speeds. bigger wheel higher top speed

13" wheels will give you lower un sprung weight so better handling

a mate of mine who races in the speed series says there is no point using tyres over 195 wide as type7`s aren't heavy enough. He has tried wider and they don't improve his sprint times





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G.Man

posted on 12/3/07 at 11:16 PM Reply With Quote
quote:
Originally posted by wacomuk
wheel size affects your acceleration and top speeds. bigger wheel higher top speed

13" wheels will give you lower un sprung weight so better handling

a mate of mine who races in the speed series says there is no point using tyres over 195 wide as type7`s aren't heavy enough. He has tried wider and they don't improve his sprint times


Indeed, merely slows tyre wear and increases unsprung weight..







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Everyone has one, nobody wants to hear it and only other peoples stink!

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viatron

posted on 24/5/07 at 01:22 PM Reply With Quote
We ran 14" wheels last year in the Tiger series and found the gearing was long in 3 and 4th.
Switching to 13" this season to try and bring the gearing down a bit, would rather have better acceleration than top speed.
Also, as already stated, it drops the car a bit lowering the CofG which should help the handling and reduces the unsprung weight on each corner.
The wheel change from 14" Sierra 4X4 alloys to 13" minilights along with dropping the sierra front calipsers and sierra rears and replacing both with hi spec has shed loads of weight, will be taking the scales upto to the workshop to work out how much but am hoping for between 10 and 15 kilos, will be even less when we fit the westfield alloy uprights to the front after Lydden.
Mac

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madman280

posted on 25/5/07 at 10:20 PM Reply With Quote
It all has to do with tires and loading. Reasonably priced racing tires for the weight of a seven happen to be 13". Many, but all larger sizes have difficulty staying keeping at the proper temperature for maximum grip. The size of the tire on the ground is only part of the equation. How sticky it it matters a great deal also.
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Wadders

posted on 25/5/07 at 11:14 PM Reply With Quote
I saved 25kg by changing to 13" wheels, and run 9" rims on the rear, with toyo 888's you can pull bits off with your finger nails after a good run, so i reckon they get plenty warm enough. Also steers far nicer than 15's
[img][/img]






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RK

posted on 26/5/07 at 03:13 AM Reply With Quote
How on earth did you stretch the Toyo's to fit a 9" rim? I was strongly advised not to fit anything less than 225 on an 8" width rim. I am extremely limited for roadgoing tyres (I give in to the majority spelling, even though I know how it's really spelt)

http://www.toyo.co.uk/page.php?identity=r888 check the max recommended allowed rim width

[Edited on 26/5/07 by RK]

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locostv8

posted on 26/5/07 at 06:21 AM Reply With Quote
I'm using 17x9 with 255 40 17 and 17x10.5 with 315 35 17 to get a larger footprint on a highly overpowered street (mostly) car. for Solo runs I will probably rethink the wheel tire but will probably still stay at around 26" diameter.

A friend years ago explained that a stiff suspension and the largest tires that didn't slow down track times will overcome a suspension that is geometry challenged. It worked for him.





http://wrangler.rutgers.edu/gallery2/v/7slotgrille/hssss/

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MikeRJ

posted on 26/5/07 at 09:57 AM Reply With Quote
quote:
Originally posted by locostv8
A friend years ago explained that a stiff suspension and the largest tires that didn't slow down track times will overcome a suspension that is geometry challenged. It worked for him.


Largest as in sidewall height I guess. Large diameter, ultra low profile tyres will enhance any flaws in the suspension rather than hide them.

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