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The mkiv Supra Owners Club

Tyres...Good deal?


Paul
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Right then, after some new tyres for my 18's

Anyone got any contacts for somewhere who'll do a good deal on some 275/40/18's and 235/40/18's ?

Looking at Goodyear F1's as that's what I've had for years on my 17's.

Just getting prices together for the best deal.

 

Paul

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Originally posted by Branners

wouldnt a 275x40x18 really really throw off the rolling radius? I would have thought a 275x35x18 would be better?

 

JB, I'm all ears mate, this is what the guy suggested.

What do you mean 'throw off the rolling radius' ?

Sorry, not up on this, any advice welcome.

 

Paul

 

BTW, got price off Ibrar already, good one but could do with a few to compare.

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paul i have a spreadsheet that has been posted up before (i will try and find the previous post), that lets you input wheel/tyres sizes etc and lets you know if they will hit the outer arches or pssibly the shocks + the change in diameter etc. The larger 275/40/18 i had to calculate myself as the spreadsheet just came up with "tyre too tall" when i put the details in. This suggests to me that the tyre will contact the body under compression or on full lock etc.

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Originally posted by Bobbeh

I think stock speedos are supposed to be spot on up to around 60/70 mph[/url]

Supposed to be? They aren't spot on though are they?

Speedos usually (always?) read waaay over the real speed if you compare them with GPS.

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dropping to a 35 profile will also make the ride harsher, as does the move to 18s, basically removes the sidewall flex which takes a fair bit of the shock when hitting bumps. The profile is a percentage of the width, so a 35 profile on a 255 would be smaller than a 35 profile on a 285. It does take a bit of thinking about, however you can run a 275x40 and just accept the speedo will be out by a bit, but then as others have said the speedo is always out anyway.

 

Best bet is to try the tyres and get somebody with GPS to sit in the car and tell you the speed the GPS thinks you are doing compared to the speedo.

 

JB

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I probably dont spend enough time in my supra now but I certainly noticed the ride become harsher with the 18s on and they arent even running high pressures, about 30psi all round. I used to run the 17s at 36psi. But then my suspension is too hard anyway. I also need to get the alignment done as the handling is a little off at the moment.

 

JB

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I have used my GPS to check the speed in 5 cars, not one was accurate at 70, all were reading low ie at a speedo indicated 70 most were at 65 to 67 mph GPS. At a GPS 70mph speedo readings were 74 to 77 mph. Most were accurate to 1 mph at 30mph~GPS.

 

This probably explains why most people go through 60 and 70 cameras at 55 and 65.

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Originally posted by Branners

dropping to a 35 profile will also make the ride harsher, as does the move to 18s, basically removes the sidewall flex which takes a fair bit of the shock when hitting bumps.

 

As they will go on my potentially 'softer' Mag alloys then maybe this would be a good reason to go with the 40 profile, bit more cushioning for the wheels? I accept that the speedo may be out slightly, but in the right direction as far as gatsos etc go, bearing in mind the type of alloy would this not be a fair trade off?

 

Paul

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