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Some good info here from some high power forum guys. Seems the width might not have to be that high per Paul whiffins comments?

 

http://www.mkivsupra.net/vbb/showthread.php?281898-Help-needed-Big-power-18-quot-wide-tyres-which&highlight=wide+tyres

 

 

btw the search function wasn't working on "search multiple content types" (it was giving only the old history as recently reported by other) but it did give me this link (from 2012) when I searched "Wide Tyres" in "Search single content type"

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I heard people going into the 300+ region, I think you need road legal semi-slicks at the rear at least to put the power down. Trying to think of high HP owners to search for :)

 

I was thinking about 315s on the rear but there simply isn't much available for 18 inch wheels... :(

 

Some good info here from some high power forum guys. Seems the width might not have to be that high per Paul whiffins comments?

 

http://www.mkivsupra.net/vbb/showthread.php?281898-Help-needed-Big-power-18-quot-wide-tyres-which&highlight=wide+tyres

 

 

btw the search function wasn't working on "search multiple content types" (it was giving only the old history as recently reported by other) but it did give me this link (from 2012) when I searched "Wide Tyres" in "Search single content type"

 

Thanks for the link bud. The search function has been playing up so much recently I just ended up giving up on it!

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You have already answered your own question.

 

Physics isn't really an opinion. The bigger the wheel, the smaller the side wall. The smaller the side wall, the less flex you have in the tyre when accelerating. The less flex you have in the tyres, the less grip you have. The less grip you have, the more likely you will find yourself in a ditch.

 

Also, forget about the aquaplaning 315 width and go with a 40 profile rear. A decent LSD too, no use it going for that sort of power if you don't have one.

Edited by Frank Bullitt (see edit history)
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You have already answered your own question.

 

 

 

Also, forget about the aquaplaning 315 width and go with a 40 profile rear. A decent LSD too, no use it going for that sort of power if you don't have one.

 

I was hoping I could get away with 315s with a 40 profile, but I can't find any tyres in that size. :( The widest rear tyres I could find with a 40 profile is a 275 and that's not really going to cut it. However, if I go down to a 35 profile, there is plenty to choose from with a 295 width.

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I was hoping I could get away with 315s with a 40 profile, but I can't find any tyres in that size. :( The widest rear tyres I could find with a 40 profile is a 275 and that's not really going to cut it. However, if I go down to a 35 profile, there is plenty to choose from with a 295 width.

 

That is the main problem when going past a 10" rear. You have probably snookered yourself going that wide and wanting a 40 rear profile unless you want to import your tyres? 285 on an 11.5 will be too stretched and a 315 will balloon. Best sizes for a 11.5 rear are either 295 or 305.

 

Were the wheels special order or could they be returned? Did you have your heart set on those widths?

 

E2A

 

For a 305/40/18 look at the Nitto NT 555 R or the Mickey Thompson ET Street but expect eye watering prices per tyre due to the exchange rate.

Edited by Frank Bullitt (see edit history)
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295/35 will give the same sidewall height/depth as the stock 17's 255/40 at around 10cms? The new 18" wheels will be an inch larger overall courtesy of their extra inch diameter. Going 40 on very wide tyres may give you clearance issues, but saying that there was that £40K single that was being sold at one point that looked like it had huge diameter rears...

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That is the main problem when going past a 10" rear. You have probably snookered yourself going that wide and wanting a 40 rear profile unless you want to import your tyres? 285 on an 11.5 will be too stretched and a 315 will balloon. Best sizes for a 11.5 rear are either 295 or 305.

 

Were the wheels special order or could they be returned? Did you have your heart set on those widths?

 

E2A

 

For a 305/40/18 look at the Nitto NT 555 R or the Mickey Thompson ET Street but expect eye watering prices per tyre due to the exchange rate.

 

The wheels are being custom made to my specification but I'd rather leave the rears at 11.5J for the sake of greater flexibility if I decide to use them in another application in the future. With a 305/40 tyre, any idea what the clearance would be like?

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295/35 will give the same sidewall height/depth as the stock 17's 255/40 at around 10cms? The new 18" wheels will be an inch larger overall courtesy of their extra inch diameter. Going 40 on very wide tyres may give you clearance issues, but saying that there was that £40K single that was being sold at one point that looked like it had huge diameter rears...

 

Is there a way we can accurately calculate clearance or is it a matter of trial and error?

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The wheels are being custom made to my specification but I'd rather leave the rears at 11.5J for the sake of greater flexibility if I decide to use them in another application in the future. With a 305/40 tyre, any idea what the clearance would be like?

 

This one is running Mickey Thompson ET Street 2 tyres - 305/45/18.

 

image

 

Going with a 40 profile the positive rake won't be as pronounced, I would be surprised if you didn't have to remove the lip.

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Going with a 40 profile the positive rake won't be as pronounced, I would be surprised if you didn't have to remove the lip.

 

Why would I need to remove the lip? If I go with a 35 profile on the rear, which I think would be reasonable compromise, I could probably get away with a 265/40 on the fronts? What do you think?

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Not too bad, yeah 265/35/18 at the front. It does follow the camber in the road and does tramline a little. But I guess that’s to be expected with a 265 front tyre.

 

I'm not sure the tramlining is due to the width of the front tyres? I used to have that issue with 235s on the front. Turned out to be a geometry issue...

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Why would I need to remove the lip? If I go with a 35 profile on the rear, which I think would be reasonable compromise, I could probably get away with a 265/40 on the fronts? What do you think?

 

It is a possibility that fettling of the lip maybe required as the wheel tyre combination may fowl the arch. Chris will be able to tell you if anything had to be done to his dad's car to get those wheels to fit. At least the ET's you have gone with are decent. I can't remember what suspension Mark put on the car or how low it was but I do remember it being on 19"s.

 

Going that wide is always going to be a compromise and as the car is an auto you need to bear that in mind. A 40 profile will allow you to put the power down and provide a nice ride, going to a 35 this will decrease slightly and going to a 30...well I'd look at investing in a new spine and things will feel very hard on the rear. This is because high-performance tyres and low profile means that there is reduced tyre flex and the tyre is not able to absorb road shocks like the high profile tyres.

 

You can always have the car mapped to run boost by gear on the Syvecs to help you get the power down. Syvecs has decent traction control too so that will be another plus as will an OS Giken 1.5 way diff if one wasn't fitted.

 

You might get lucky and find it all comes together but I wouldn't be going into this expecting it to all be problem free.

 

I'm not sure the tramlining is due to the width of the front tyres? I used to have that issue with 235s on the front. Turned out to be a geometry issue...

 

Tyres have the most direct influence on tramlining because they are the part of the vehicle that comes into contact with the road. Unfortunately anything that increases a high performance tyre's responsiveness also increases its willingness to tramline. Tyres with short sidewalls that develop lots of cornering power at lower slip angles are more susceptible to tram lining.

 

But as you have said, making sure the geo is spot on is a must.

 

E2A

 

Kaan's car ran a 35 profile on the 18" rears but a lot wider at 345 - http://www.mkivsupra.net/vbb/vbpicgallery.php?do=view&g=5306

Edited by Frank Bullitt
Link added. (see edit history)
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It is a possibility that fettling of the lip maybe required as the wheel tyre combination may fowl the arch. Chris will be able to tell you if anything had to be done to his dad's car to get those wheels to fit. At least the ET's you have gone with are decent. I can't remember what suspension Mark put on the car or how low it was but I do remember it being on 19"s.

 

Going that wide is always going to be a compromise and as the car is an auto you need to bear that in mind. A 40 profile will allow you to put the power down and provide a nice ride, going to a 35 this will decrease slightly and going to a 30...well I'd look at investing in a new spine and things will feel very hard on the rear. This is because high-performance tyres and low profile means that there is reduced tyre flex and the tyre is not able to absorb road shocks like the high profile tyres.

 

You can always have the car mapped to run boost by gear on the Syvecs to help you get the power down. Syvecs has decent traction control too so that will be another plus as will an OS Giken 1.5 way diff if one wasn't fitted.

 

You might get lucky and find it all comes together but I wouldn't be going into this expecting it to all be problem free.

 

 

 

Tyres have the most direct influence on tramlining because they are the part of the vehicle that comes into contact with the road. Unfortunately anything that increases a high performance tyre's responsiveness also increases its willingness to tramline. Tyres with short sidewalls that develop lots of cornering power at lower slip angles are more susceptible to tram lining.

 

But as you have said, making sure the geo is spot on is a must.

 

Very helpful information Frank, thank you for taking the time to share it.

 

I already have the OS Giken 1.5 LSD fitted so I guess that's one less thing I have to worry about! :rolleyes:

 

All things considered, I think I will have to compromise and go with 35 profile tyres on the rear. Reason being; I need at least 295s at the back in order to put the power down and sadly, no mainstream tyre manufacturer produces readily available tyres in that size with a 40 profile. So, in the unfortunate scenario I suffer a blow out or the tyre sustains some sort of irreparable damage, I will effectively be at the mercy of an international company, which will undoubtedly leave me stranded for at least a few days whilst the replacement tyre is shipped, at an extortionate cost no doubt, due to the urgency.

 

In the ideal world, and as I have eluded to in the past, I would prefer a larger side wall at the rear, for the various reasons that you and I have catalogued previously; however, this world is far from ideal and that is why I think a slight hit on the rear profile would be worthwhile. Going to a 35 profile from a 40 profile, is in the grand scheme of things, a relatively small change. This will not only afford me the luxury of having Michelin Super Sports as an option for tyres all round, but also allow me to stagger the front with a 40 profile, a stock feature I would have always wanted to keep proportionate.

Edited by Mo Reviews (see edit history)
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