Tyre size/profile v rim width?
Submitted: Thursday, Feb 11, 2016 at 17:50
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pop2jocem
We have recently had a thread about tyre selection brand and construction, this is more about the rims we choose to fit our favoured tyre to. I'm talking about the prefered width for a particular tyre not whether a steel is prefered over ally or vice versa.
Now I fully realise that tyre manufacturers recommend a width for whatever the tyre is and usually there is a range that satisfies their criteria.
For example a certain manufacturer recommends a range of rim widths between 7" and 9" as being suitable for a 31x10.5R15 tyre. I'm not picking this tyre for any particular reaon, just as an example. I do acknowledge that this can vary between manufacturers for whatever reason.
So if you had to choose a rim at the same time, which would be your choice and why?
Regardless of the tyre I had picked, personally I would go with the narrower end of the scale.
My reasoning, right or wrong, is that there is less of the sidewall exposed to rocks or sticks or whatever in the rough stuff. Particularly when reducing pressures to attempt to limit the vunerability of the more exposed aforementioned sidewall which is usually the weakest part of the tyre and damage to that area usually procludes any repair from being undertaken for the long term use.
Yeah, I know we let our tyre down to increase footprint length rather than width, as
well as provide a softer ride, but obviously the sides of the tyre do bag out more.
So do you guys agree or disagree with my theory and why???
Cheers
Pop
Reply By: swampy - Friday, Feb 12, 2016 at 13:15
Friday, Feb 12, 2016 at 13:15
hi
A narrow rim to tyre size will let the tyre roll around a bit , can give poor wear on the black top ,
at very low pressures may roll of the bead ,more comfortable on the black stuff
A wider rim will expose the rim lip to damage and opposite to above .
There is recommended tyre rim specs for every tyre .
For the same size of tyre with the same construction the higher the profile 70,75,78 series etc will be more comfortable .
swamp
AnswerID:
596174
Follow Up By: pop2jocem - Friday, Feb 12, 2016 at 14:50
Friday, Feb 12, 2016 at 14:50
You're quite right swampy. I'm not advocating anyone should ignore the tyre manufacturers recommendations re rim width. Actually I'm not recommending anyone do what I do, just asking what others do and why.
What I am saying is that in most cases there is a spread of rim widths that a given tyre can be fitted to and still conform to what the maker has recommended.
Obviously going outside those recommendations is leaving oneself open to all sorts of grief.
Personally I do like to use higher profile tyres where possible for the same reasons, however once again one has to keep tyre pressures a bit higher because as discussed above higher profile tyres tend to squirm or deform more than lower profile when cornering. I guess that's why high performance cars tend to sacrifice comfort for road holding when selecting a tyre construction and profile.
Maybe I should have been a bit more specific, I am talking about vehicles and their tyres that are being used off road and not just by the ubiquitous "soccer mum."
Cheers
Pop
FollowupID:
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Reply By: Blown4by - Sunday, Feb 14, 2016 at 17:19
Sunday, Feb 14, 2016 at 17:19
Regarding the exposure of the tyre walls to damage: The narrower the rim = more wall exposure because the more you pull the tyre beads in closer to each other the more the walls are going to bulge out. Insofar as the rim width goes get a copy of the Tyre & Rim Association Manual. This document gives the legal rim width for all tyre sizes with the maximum and minimum widths allowed as
well as the optimum rim width for each tyre size. It is
well to remember that if you fit a rim narrower than the minimum width for a particular tyre size you will very likely split the rim in half and if this was to result in a MVA you would have no insurance and be liable civilly at law. I will leave it to others to discuss the pro's and con's of aspect ratio, diameter, offset, pressure and wear patterns but it is
well to remember on a 4x4 (equipped with low range) that you are only permitted under VBSB14 to increase the tyre diameter and vehicle track by 50mm max. Any increase in diameter reduces braking efficiency.
AnswerID:
596241