 | Home > Wheels & Tyres > Running a spare of a different size from the rest?? |
 
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| Martin Site Admin Member Since: 02 Apr 2007 Location: Hook Norton Posts: 6611   
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First off check both sizes as I don't think 275/75R16 is a common size, BFG or otherwise
Plugging your sizes into the "comparison" tab here: https://tiresize.com/calculator/ Gives a circumference difference of 10%, which really is too much. I'd run it to get me off the hard shoulder but not for any considerable distance. Check the size of the big tyre and do the calc   1988 90 Td5 NAS soft top
2015 D90 XS SW |
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19th Jun 2018 2:12pm |
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| jst Member Since: 14 Jan 2008 Location: Taunton Posts: 8051  
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sizes look a bit out on larger tyre. 285.75?
your 275.75R16 is 818.9mm (32.2") high your 225.75R16 is 743.5mm high. (29.2") Cheers James 110 2012 XS Utility 130 2011 M57 bespoke Camper 90 2010 Hardtop 90 M57 1988 Hardtop |
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19th Jun 2018 2:30pm |
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| m3vert Member Since: 15 Mar 2018 Location: Central Scotland Posts: 162  
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Cheers Martin, I am away from the car for another week or so, so cannot check. My Wife checked and assured me that was the size on though? I did think it was a bit much, we are doing a good few miles on an upcoming holiday and am thinking I should probably bite the bullet and get another steel the same as the existing wheels and a tyre the same
My next issue is I don't know where the modular steels came from!! Are they all the same offset wise? Nah I doubt it 
Thanks for your help |
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19th Jun 2018 2:33pm |
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| Stiff1 Member Since: 09 Dec 2014 Location: Cornwall Posts: 597 
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Due to a recent puncture on the Zafira while in France, I realised the spare was a 16 while the ones on the car were all 17's. Did the job of getting me to a repair centre but was concerned.
I do remember a past post discussing this and the point that we all kept coming back to was that a lot of cars ship with a space saving spare which is of a smaller diameter and width and this seems fine all be it with the caveat of driving under 50ish and for a limited mileage. |
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19th Jun 2018 6:36pm |
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| Martin Site Admin Member Since: 02 Apr 2007 Location: Hook Norton Posts: 6611
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16/17 refer to the wheel size (diameter in inches) not the tyre. Chances are they are fitted with different profile (sidewalk height) tyres and so are overall the same diameter when shod with tyres.
1988 90 Td5 NAS soft top
2015 D90 XS SW |
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19th Jun 2018 6:38pm |
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| Stiff1 Member Since: 09 Dec 2014 Location: Cornwall Posts: 597
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Could well be Martin, its back under the car and hopefully will stay there until I return home.
The point still remains, space savers are very different in all dimensions to the standard wheel. The previous post came about when the OP had some expensive/ wide wheels and wanted to save a bit with a cheaper/ smaller on the back with a cover if I recall. |
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19th Jun 2018 6:43pm |
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| LandRoverAnorak Member Since: 17 Jul 2011 Location: Surrey Posts: 11324
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A constant 4wd is very different to an ordinary car. The centre differential won't tolerate large discrepancies in wheel / tyre diameter . Darren
110 USW BUILD THREAD - EXPEDITION TRAILER - 200tdi 90 BUILD THREAD - SANKEY TRAILER - IG@landroveranorak "You came in that thing? You're braver than I thought!" - Princess Leia |
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19th Jun 2018 6:56pm |
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| L90Andy Member Since: 29 May 2014 Location: Stratford-Upon-Avon Posts: 719 
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Regardless of the size written on the tyre and the numbers the online calculator give, they are only 'Design nominal' dimensions whereas the actual tyre is likely to be different.
Best best is to physically measure the unladen diameter of both to determine the real difference. Ideally your aiming for a similar OD and in an emergency situation wheel offset or tyre tread width won't matter. Instagram: L90andy My 1984 Ninety: http://www.defender2.net/forum/topic56071.html - SOLD! My 2015 Defender: http://www.defender2.net/forum/topic39625.html - SOLD! |
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19th Jun 2018 7:29pm |
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| m3vert Member Since: 15 Mar 2018 Location: Central Scotland Posts: 162
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Thanks folks, appreciate all the feedback. My Wife has just sent me a photo of the tyre and she is clearly dsylexic! The ones on the motor are 285-75-16 indeed and not 275! So I guess this makes the issue even more of a problem.
Since i do not know what steel wheels are fitted (black modulars but no idea who makes them or style) I think I will stick with the steel wheel that I have as a spare, even though it will no doubt be slightly different offset and try and pick up another 285-75-16 before we set off on our holiday down south! |
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19th Jun 2018 7:41pm |
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| LandRoverAnorak Member Since: 17 Jul 2011 Location: Surrey Posts: 11324
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Sorry to add to your woes but if your spare is a standard LR steel wheel then it won't be anywhere near wide enough for a 285 tyre. I'm not sure what might be a suitable diameter alternative, off hand. Darren
110 USW BUILD THREAD - EXPEDITION TRAILER - 200tdi 90 BUILD THREAD - SANKEY TRAILER - IG@landroveranorak "You came in that thing? You're braver than I thought!" - Princess Leia |
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20th Jun 2018 7:33am |
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| Cupboard Member Since: 21 Mar 2014 Location: Suffolk Posts: 2971 
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FWIW, you shouldn't be able to pass an MOT with different sized wheels on the same axle.
https://www.mot-testing.service.gov.uk/doc...class3457/ It's been like that for a while but I do know one car that's been through an MOT with a 13" wheel and three 14" wheels. The tyre profile made the overall rolling diameter pretty similar. |
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20th Jun 2018 8:37am |
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| m3vert Member Since: 15 Mar 2018 Location: Central Scotland Posts: 162
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Hi Landrover Anorak thanks, yeah I had thought that might be the case. I am trying to find the same style modular steel as I have fitted, but no joy so far. I assume the wheel will have a stamp in it somewhere telling me the offset and size???
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20th Jun 2018 8:42am |
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| hank Member Since: 12 Sep 2016 Location: South Wales Posts: 2301  
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Another thing to be aware of, different rolling circumference will cause the ABS and traction control lights to illuminate (if fitted) as the control unit will sense wheels rotating at different rpm.
Lights should go out when matching tyres are refitted |
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20th Jun 2018 9:33am |
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