2005 SR5 Tyre upgrade to 31/10.5R15

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2005 SR5 Tyre upgrade to 31/10.5R15

Postby sjg93 on Mon, 10 Dec 2018 11:06 +0000

Hi All,

I'm looking to replace the tyres on my late ''05 KUN26 SR5. Running 255/70R15 Cooper A/T at the moment and pretty set on the Hancook Dynapro's in a 31/10.5R15. Running thru the forums i keep getting conflicting opinions on both whether these are 'legal' as per NSW RMS and whether they will rub at full turn. From what i can tell the 31's are under a 7% increase on the placard tyre size diamater which (i think) satisfies RMS requirements. Looking for an up to date opinion on whether the tyres will rub when at full turn? I'm on standard factory 15" rims with only mods being Pedders front sports struts and an ARB deluxe bull bar.

Any guidance/knowledge is much appreciated!!!
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Re: 2005 SR5 Tyre upgrade to 31/10.5R15

Postby HK1837 on Mon, 10 Dec 2018 12:00 +0000

As far as I am aware you can go up 75mm as a combination of suspension and tyres under the new NCOP.

By my calca the 31x10R15 are 787.4mm diameter, and the 255/70R15 are 738mm, so that is a diameter increase of 49.4mm which is half that in vehicle lift of 24.7mm so even if you want to lift it by 50mm then you are still OK.

If you are using the original 15x7 rims you should be OK for scrubbing. I can tell you that on my 2011 SR5 which is identical to a 2005, I fitted 265/65/17 on 17x7.5 120 series rims (Prado) and these are 776.3mm diameter and they did not scrub. You are talking 11mm bigger in diameter though.

What I did have issues with though was the front rotors did not handle the extra load that the bigger tyres put on them and they fried up pretty quickly. I upgraded to 120 Series rotors and calipers (same as TRD Hilux) as a result, but you will need to go to 17” rims to clear the calipers if you do this.
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Re: 2005 SR5 Tyre upgrade to 31/10.5R15

Postby greid on Mon, 10 Dec 2018 10:21 +0000

I'm a 2006 SR running 31"x10.5 BF Goodrich on SR5 rims and can confirm that there is NO scrubbing. Rekon the bigger tyres look a lot better, really fill out the wheel wells
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Re: 2005 SR5 Tyre upgrade to 31/10.5R15

Postby sjg93 on Tue, 11 Dec 2018 5:08 +0000

Great thanks guys - i was confident there wouldn't be any scrubbing but wanted to double check. Ans as you say greid i reckon the bigger tyres definently look a lot better, there is so much empty space on my Sr5 especially on the back wheels they almost look out of place.
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Re: 2005 SR5 Tyre upgrade to 31/10.5R15

Postby HK1837 on Tue, 11 Dec 2018 8:11 +0000

All Toyota did on the 2011 diesel SR5 dual cab to fit 265/65/17 tyres (as already mentioned slightly smaller than 31”) was to increase the rotor diameter from 297mm to I think 319mm and the thickness from 25mm to 28mm otherwise the vehicle’s brakes would not be adequate. The 2008 TRD with 265/65/14 tyres used a 338mm x 28mmrotor.

However I have an old memory that 31” tyres may actually be more like 30.5” which is basically what 265/65/17 are so no wonder they look right, as you have replicated a 2008 TRD or 2011 SR5 diesel!
Last edited by HK1837 on Tue, 11 Dec 2018 12:30 +0000, edited 1 time in total.
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Re: 2005 SR5 Tyre upgrade to 31/10.5R15

Postby Surfermax on Tue, 11 Dec 2018 11:52 +0000

greid wrote:I'm a 2006 SR running 31"x10.5 BF Goodrich on SR5 rims and can confirm that there is NO scrubbing. Rekon the bigger tyres look a lot better, really fill out the wheel wells

x2 for 31x10.5r15 BFG tyres. I have had the KO2's since July and I can say the speedo is now pretty much spot on (maybe 1-2 ks out) and driving feels a lot more natural. Haven't taken the lux off road yet but reckon the ride will be more comfortable from what I have been told when compared to the OEM tyres
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Re: 2005 SR5 Tyre upgrade to 31/10.5R15

Postby outbackjoe on Thu, 13 Dec 2018 2:21 +0000

I think tyre might be illegal due to being lower load rating than original. But won't be a problem, heaps of people running 31s. They light truck construction so plenty strong enough.
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Re: 2005 SR5 Tyre upgrade to 31/10.5R15

Postby Surfermax on Thu, 13 Dec 2018 2:26 +0000

outbackjoe wrote:I think tyre might be illegal due to being lower load rating than original. But won't be a problem, heaps of people running 31s. They light truck construction so plenty strong enough.

depends on what state you are in too? I think most states accept NCOP so no problem with size anymore, but in QLD load rating is based on the tyre placard which on a 05 to 10 KUN26 SR5 Hilux states that the tyres must be rated higher than the axel load rating which is 1600kg. Divide this by 2 and you have 800kg. 31x10.5r15 are 109 load rated or 1030kg per tyre so plenty there. I do know the RMS in NSW however has interpreted this to state the load rating on the tyres has to be greater than the OEM tyres fitted which were 112 load rated. This is a bugger for people in NSW as QLD and the other states appear to go by the tyre placard. I have checked this with Jax tyres, Goodyear Auto and Coopers tyres directly and they have all said the same.
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Re: 2005 SR5 Tyre upgrade to 31/10.5R15

Postby greid on Fri, 14 Dec 2018 6:13 +0000

That's good for you surfermax that your speedo is pretty good now, mine was bang on running bang on with 225's on the SR rims, so now with 31" on the SR5 rims I'm about 5% out. Think the biggest tyres you can run on the SR rims are like 29" arent they? So going up to the 31's gives you another inch in clearance for your diff's , which doesnt sound like much, but actually works out to be like 10-12% from memory
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Re: 2005 SR5 Tyre upgrade to 31/10.5R15

Postby HK1837 on Fri, 14 Dec 2018 7:35 +0000

When you put them on at least fit some decent rotors like PBR T3. With the bigger tyres you will really notice how much worse those 2005-2011 diameter rotors are, you really have to work hard on the pedal to get them to work with the larger diameter tyres. Mine went blue inside 10,000kM with the change from 255/70/15 to 265/65/17. I changed to T3 rotors but took them off within another 10,000kM as they were still not enough, and upgraded to TRD size rotors. Haven’t had a problem since!
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Re: 2005 SR5 Tyre upgrade to 31/10.5R15

Postby Surfermax on Fri, 14 Dec 2018 8:05 +0000

HK1837 wrote:When you put them on at least fit some decent rotors like PBR T3. With the bigger tyres you will really notice how much worse those 2005-2011 diameter rotors are, you really have to work hard on the pedal to get them to work with the larger diameter tyres. Mine went blue inside 10,000kM with the change from 255/70/15 to 265/65/17. I changed to T3 rotors but took them off within another 10,000kM as they were still not enough, and upgraded to TRD size rotors. Haven’t had a problem since!

Yes will look at doing that too – do I need to upgrade the rotors if I stay with the stock 15x7 rims with 31x10.5r15 tyres or only if I go for bigger rims like 17x8 etc?

FYI since running the larger tyres I have noticed the braking distance has increased a fair bit, but speedo is pretty much bang on.
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Re: 2005 SR5 Tyre upgrade to 31/10.5R15

Postby HK1837 on Fri, 14 Dec 2018 8:32 +0000

It isn’t the rim size, it is the tyre diameter that affects brakes. It is force at a distance. As you go up in tyre diameter you really need bigger rotors, this is why the 2012 onwards have 319mm rotors with 265/65/17 tyres (basically the same tyre diameter as you have). The problem you have though is I don’t think your 15” SR5 rims will fit over those 2012 onwards calipers, so you are stuck with the small 2005-2011 rotors. The good T3 style rotor won’t give you any better braking force as they are the same diameter, but they will fade less and handle heat better.

Yes, all 2005/6-ish onwards cars sold new in Australia have an inbuilt speedo error, the ADR’s changed around that time. My 2011 (with 255/70/15) used to read 100 when I was doing about 93-4, I think this is why you get so many idiots on freeways in the fast lane(s) doing 100 in the 110 zones. When I fitted 265/65/17 tyres the speedo is pretty close, 100 indicated is 101 I think or close to it.
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Re: 2005 SR5 Tyre upgrade to 31/10.5R15

Postby Surfermax on Thu, 03 Jan 2019 9:52 +0000

sjg93 wrote:Great thanks guys - i was confident there wouldn't be any scrubbing but wanted to double check. Ans as you say greid i reckon the bigger tyres definently look a lot better, there is so much empty space on my Sr5 especially on the back wheels they almost look out of place.

Hi, did you end up getting the 31's?
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Re: 2005 SR5 Tyre upgrade to 31/10.5R15

Postby sjg93 on Mon, 07 Jan 2019 6:33 +0000

Surfermax wrote:
sjg93 wrote:Great thanks guys - i was confident there wouldn't be any scrubbing but wanted to double check. Ans as you say greid i reckon the bigger tyres definently look a lot better, there is so much empty space on my Sr5 especially on the back wheels they almost look out of place.

Hi, did you end up getting the 31's?
Hi all so yeh ended up getting the 31's put on just after christmas. So far so good with them, ran them 500km on the highway yesterday and no issues at all regarding noise or whatever. There is noticeably more clearance and they handle slightly different to the coopers but to be expected. They certainly fill out the wheel wells much better and there is no scrubbing at all when turning. Regarding loads, the new Hancooks are 109 rated whereas the previous 255/70R15 Coopers are only 108 so i've actually increased the load rating. Braking noticeably is a bit harder on the brakes so may have to look at new rotors in the future, however i don't actually do much offroading or hard braking so it might not be as big an issue for me - most of the usage is around town and general highway driving. I tried to post a picture but not sure if you can on this thread?
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Re: 2005 SR5 Tyre upgrade to 31/10.5R15

Postby sjg93 on Mon, 07 Jan 2019 12:12 +0000

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Re: 2005 SR5 Tyre upgrade to 31/10.5R15

Postby HK1837 on Tue, 08 Jan 2019 4:59 +0000

You won't be able to fit bigger rotors with 15" rims.
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Re: 2005 SR5 Tyre upgrade to 31/10.5R15

Postby hiluxxury on Tue, 08 Jan 2019 6:55 +0000

Also consider new standard sized rotors with WRX pads and properly adjusted rear drums.

This will provide improved brake performance and no need for 17in rims.

I came from this setup to the prado brake upgrade. While the prado setup is slightly better, the WRX pads make a fair difference.
I might be wrong.

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Re: 2005 SR5 Tyre upgrade to 31/10.5R15

Postby sjg93 on Tue, 08 Jan 2019 7:32 +0000

hiluxxury wrote:Also consider new standard sized rotors with WRX pads and properly adjusted rear drums.

This will provide improved brake performance and no need for 17in rims.

I came from this setup to the prado brake upgrade. While the prado setup is slightly better, the WRX pads make a fair difference.


Any rough costing on those pads? And how much is a new set of rotors?
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Re: 2005 SR5 Tyre upgrade to 31/10.5R15

Postby Surfermax on Tue, 08 Jan 2019 7:39 +0000

sjg93 wrote:
hiluxxury wrote:Also consider new standard sized rotors with WRX pads and properly adjusted rear drums.

This will provide improved brake performance and no need for 17in rims.

I came from this setup to the prado brake upgrade. While the prado setup is slightly better, the WRX pads make a fair difference.


Any rough costing on those pads? And how much is a new set of rotors?

Also will the WRX pads fit in the Hilux callipers or will need new callipers too?
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Re: 2005 SR5 Tyre upgrade to 31/10.5R15

Postby HK1837 on Tue, 08 Jan 2019 7:40 +0000

Good T3 Aussie made rotors are about $400 or so for a pair. I think these are right:
https://www.ebay.com.au/itm/DBA-T3-4000 ... Swi7RZHQDi

They won’t give you any more braking torque than what you have now as they are the same diameter, nor will other pads. But they won’t get as hot as fast, will cool quicker and will be less fade resistant. With the road surface further away from the centre of the wheel that the bigger tyres give you, the rotor needs to be a bigger diameter to counter it. So with the T3 rotors and good pads you’ll still have to work harder on the pedal and the brakes will get a lot hotter as they are working harder, but at least you temper that a bit with the T3 rotor design.
I’m an Engineer (Electrical not Automotive) but if I was Engineering any car with bigger tyres I would insist upon bigger rotors. To me it is no different to modifying a 15A tool plug so it works in a 10A outlet, it works but you are overloading the design limits of the cable in the wall, the 10A switch on the outlet and the active and neutral pins on the socket.
Last edited by HK1837 on Tue, 08 Jan 2019 10:03 +0000, edited 1 time in total.
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