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: TomH - Thursday, Feb 11, 2016 at 18:18
Thursday, Feb 11, 2016 at 18:18
I would pick the WIDEST rim that fits as it would protect the sidewall.
Fitting a narrow rim would expose the sidewall much more as in semi bagged all the time.
Look at this and try some different sizes and it will show you what they look like and tell you if they are good or bad
https://www.rimsntires.com/specspro.jsp
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Follow Up By: pop2jocem - Thursday, Feb 11, 2016 at 21:04
Thursday, Feb 11, 2016 at 21:04
Sorry Tom but I don't follow how a wider rim will give the tyre sidewall more protection.
As for that " tire" chart link, the tyres I have seen mounted on narrower or wider rims don't behave like that.
Just for an example pull the rim width in to a ridiculous figure. The tyre doesn't just sit it's sidewalls vertical as shown. Maybe ok for a graphic simulation but that's about it.
One drawback about going too narrow is that you have to run lower than optimal pressures or you will wear the center of the tread out fast.
Cheers
Pop
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Follow Up By: TomH - Thursday, Feb 11, 2016 at 22:10
Thursday, Feb 11, 2016 at 22:10
Well if you have a wide rim and the sidewall doesnt stick out the rim will bump something before the tyre. Wish my wife had them when she rubbed a gutter and cut the sidewall and never marked the rim.
I agree about the too narrow bit but surely you wouldnt stick a 10 in tyre on a 6 in rim
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Follow Up By: pop2jocem - Thursday, Feb 11, 2016 at 22:38
Thursday, Feb 11, 2016 at 22:38
I agree Tom, you wouldn't put a 10" tyre on a 6" rim. As per the example I cited for a nominal 10" tyre with a 7" to 9" rim width recommendation, you would stick within the tyre makers specs but they give you a 2" "window" if you like.
Cheers
Pop
FollowupID:
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Reply By: Member - Rod N (QLD) - Thursday, Feb 11, 2016 at 19:08
Thursday, Feb 11, 2016 at 19:08
Expanding on this subject a little if I may. With tyre profiles is there any advantage of for example a 75 over a 60 or vise versa?
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Follow Up By: TomH - Thursday, Feb 11, 2016 at 20:14
Thursday, Feb 11, 2016 at 20:14
Depends on the vehicle but I saw a set of 22ins on a Landcruiser once with about 35 profile on them.
Would have ridden like a dray and first big pothole would be the end of it.
In a Cruiser half the cushioning is in the tyres and thats why they have 70 or 75's . Also you can let them down and they dont drag the rims on the ground.
Basically the lower the profile the stiffer the sidewalls need to be to keep the rims off the ground.
Ever ridden in an EVO with 35's on it Like being on solid wheels.
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Follow Up By: pop2jocem - Thursday, Feb 11, 2016 at 20:55
Thursday, Feb 11, 2016 at 20:55
i too have seen a Landcruiser with large diameter rims, no idea what size but probably about the ones Tom has described. The tyres were so low profile the rim wouldn't have been much more than 50 mm from the road surface. IMHO this was only dressed up as a bouvelard cruiser, totally useless for any soft sand or bush track work. Probably went around hard surface corners a treat though. No tyre deformation there.
Cheers
Pop
FollowupID:
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Follow Up By: Sigmund - Friday, Feb 12, 2016 at 08:52
Friday, Feb 12, 2016 at 08:52
Yes, a taller tyre provides more cushioning and more bagging out.
Just as an aside, in tyre specs the width appears to refer to max x-section width, not the tyre tread. Big difference on some models.
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Follow Up By: Stu & "Bob" - Sunday, Feb 14, 2016 at 13:16
Sunday, Feb 14, 2016 at 13:16
Another problem with "painted on" tyres is that spotting flat tyres is difficult.
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Reply By: Crusier 91 - Friday, Feb 12, 2016 at 08:04
Friday, Feb 12, 2016 at 08:04
Narrower tyres = less drag= less fuel to propel the vehicle forward.
Keeping within vehicles manufacturer rim size recommendation = no defect via police inspection & no problems with your insurance provider.
The driver's road manners and off road skill will determine longevity of tyres.
and then there is which tyre brand to go with..........................another thread.
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Reply By: Bob Y. - Qld - Friday, Feb 12, 2016 at 10:02
Friday, Feb 12, 2016 at 10:02
Pop,
Tend to prefer the wider rims........still a hoon?
Taking a 265.75R16 as an example, I think they recommend 7"-8" rim width. We had these tyres fitted on Toyota 8" rims, and I found great difficulty in getting the tyres out onto the beads. After some frustrating events, eventually bought an air cannon, which soon got the tyres onto the beads. Feel it would have been an exhausting experience if doing it on the Madigan, GRR or similar situation.
Think 7" might be a better option, for bush work, in my above example? Or use Mick O's butane method? :-)
Bob
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Follow Up By: pop2jocem - Friday, Feb 12, 2016 at 14:31
Friday, Feb 12, 2016 at 14:31
G'day Bob,
Yeah I watched Mick's video about using the butane method. While I might be tempted to try something like that as last resort, I reckon there are a few other options I might try first....lol.
While my eyebrows are getting quite feral and could do with the odd trim, the hairs on top are getting a little sparse these days. (;-))
I must admit I didn't consider the fitting in remote areas as being an advantage with the narrower rim.
Maybe I have been lucky so far but the worst staking I have had to contend with was repairable with a large patch on the inside of a tyre and I only removed one side of the tyre from the rim and it re-inflated without much hassle.
Cheers
Pop
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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
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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
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Reply By: 9900Eagle - Friday, Feb 12, 2016 at 17:43
Friday, Feb 12, 2016 at 17:43
Pop, I just go in the middle between the min size wheel width and the max size wheel width. I find thats the best size for the selected tyre.
I also agree with you that I would pick the narrower wheel.
Slow Eagle
May all the spilt rims on this earth be reincarnated as safety rims.
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Reply By: swampy - Friday, Feb 12, 2016 at 18:28
Friday, Feb 12, 2016 at 18:28
hi pop2jocem,
not saying u would fit an illegal combo I do understand what u are saying .
an eg is 235/75/15 AT very very common tyre
rim range 6-8 inches most car makers use 6.5 inch and most aftermarket use 7.0inch
In an onroad situation I have used 6 inch rim with 225 /65 /14 tyre. Tyre fitted with a fair amount of side wall bulge but it was a vehicle meant for comfort not speed or off road.
To avoid any issues pick middle of the row. This all depends upon availability.
swampy
AnswerID:
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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.
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