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Advice on tyre load rating


BruceM

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I’m sourcing my new tyres and would appreciate some advice re load ratings to ensure that my understanding is correct.

 

My rear axel is plated at a maximum of 2120 Kg.

 

So I’m assuming that I halve that to establish the minimum acceptable tyre load rating – ie 1060 Kg.

 

Consequently a tyres rated at 116 – ie 1250Kg would provide a decent margin of error; and even a tyre rated at 113, ie 1150 Kg would be acceptable

 

Is that correct?

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Load index table attached below.

 

In principle a tyre with a 110 load-index (1060kg x 2 = 2120kg) should be acceptable for your rear axle if you never overload it, but a 113 load-index (1150kg x 2 = 2300kg) would be preferable and adequate, and a 116 load-index (1250kg x 2 = 2500kg) better still.

 

(Obviously the tyre size and type will be important, not just the load-index.)

1140317527_Loadindex.png.0372c7e2f201322549a51a15434dba52.png

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I always use the rear axle plated weight and halve it. Then add 10% as a safety margin and select a suitable tyre load index based on that.

 

This method is recommended by some tyre experts. It may be belt & braces but better to err on the side of enhanced safety :-D

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Derek Uzzell - 2020-08-07 8:49 AM

 

Presumably you’ve ordered tyres in 215/75 R16 size - might be interesting to know what make and ‘tyre name’ you chose.

 

Absolutely. I’ve ordered Continental VanContact 4Season tyres. You may recall from previous postings that I was after tyres with the 3PMSF mark. I’d have preferred Nokian but they’re like hens teeth around here and I’m not interested in a 70 mile round trip just to get the tyres replaced.

 

Also; there’s sometimes debate on the forum from time to time about the age to replace tyres so I thought I’d share this photo with you. I spotted it on one of my offside rear tyres on Wednesday. The van was MOT’d in March with no advisories and since then I’ve just taken it for a weekly run up and down the A2 to maintain both the van and my sanity. The rear tyres are about ten years old. There was no noticeable contact with road debris. You’ll note that there are apparently two points of apparent failure visible.

RearTyre.thumb.jpg.3e231f184e912b121cdf931be3bfb784.jpg

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My tyre replacement was rescheduled for yesterday and all went well – however my post installation checks have raised a question. I took the van for a test drive yesterday. I was verifying the tyre pressures this morning and noticed that one front wheel and one rear wheel have a balancing weight each whilst the other two wheels have none. How probable is this on steel wheels? Should I be concerned that balancing weights have fallen off during my test drive?
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Not necessarily. If the wheels were re-balanced during fitting, and you experienced no vibrations while driving (which is what the weights are for) I'd assume all is as it should be. If the wheel balancing was dynamic, you may find balance weights on the inside of the rim where there is none on the outside edge.
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I checked the inside rims and no weights there, and on all the wheels I can see where the old weights used to be. They would have been removed prior to rebalancing. I think I’ll need to take it on a another test run – assuming that I can find a smooth bit of the A2/M2 – it’s rather diabolical around these parts.
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Bruce

 

This 2017 “Overclockers UK” forum thread discussed finding wheels without any balance-weight after tyres had been changed.

 

https://forums.overclockers.co.uk/threads/chance-of-wheels-being-balanced-with-no-weights.18772164/

 

As was advised in that thread, it’s rare that after a replacement tyre has been fitted, the new-tyre/wheel combination will prove to be so well in balnce that no balance-weight whatsover will be required. I would have thought that the chances of this happening with a Ducato steel wheel + new tyre will be pretty small and the chances of it happening on two wheels of a motorhome near enough zero.

 

You’ll need to drive at 60mph or higher to check the balance and, if only a small weight would be needed to bring a wheel into balance, the effect of a small imbalance on a rear wheel may not be easily noticed. A small imbalance on a front wheel may also not be immediately obvious.

 

Before taking your motorhome on another test run, I suggest you speak to the tyre-fitting company and ask if the fitter found that no balnce-weights were needed on two of your motorhome’s wheels. It’s got to be sufficiently unusual for no weights to be required after a tyre replacement that a fitter putting four new tyres on a motorhome should remember this.

 

 

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My inclination is always to have every wheel and tyre rebalanced whenever new tyres are fitted or old tyres refiited - after a puncture for example.

It costs so little and if nothing else reduces wear on the steering and suspension components and if faults exist or develop they will not be masked by wheel balance issues.

I am also inclined to stick with manufacturer or converters original fitted tyre sizes unless significant changes to the GVW / MIRO are undertaken.

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I’ve put an enquiry through to the tyre supplier asking them to raise a query with their (mobile) fitter. I paid for balancing. I’m inclined to think that the weights dropped off although if they have it surprises me, I’d have expected them to be firmly fixed in place.
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BruceM - 2020-08-13 6:49 PM

 

I’ve put an enquiry through to the tyre supplier asking them to raise a query with their (mobile) fitter. I paid for balancing. I’m inclined to think that the weights dropped off although if they have it surprises me, I’d have expected them to be firmly fixed in place.

 

I’m inclined to think that the weights dropped off

 

What - all of 'em? If so there should be marks where they were fitted, you probably won't find marks for all of 'em but some at least should be visible if they were fitted?

And even if they did all fall off it is a pretty poor show by the fitter who should be accountable for his handiwork?

To save (themselves) money some fitters have been known to use secondhand weights which are prone to falling off .

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Bruce has said that, after four replacement tyres had been fitted, he noticed that one front wheel and one rear wheel had balance-weights on them but the remaining two wheels had no balance-weights. Bruce was able to see where the old balance-weights had been on the wheels and (presumably) was able to confirm that the weights that are on the one front and one rear wheel are new. It’s to be expected that traditional ‘knock on’ weights (image attached) will be used with Ducato steel wheels, so there should be no problem distinguishing between a new or an old weight.

 

So either the fitter failed to balance two of Bruce’s motorhome’s wheels, or the fitter put new weights on all four wheels but the weights fell off two of the wheels, or the fitter found that two of the wheels did not require any weights. As the fitter evidently did fit weights to two wheels, it seems reasonably to assume that all four wheels were balanced, leaving the last two possibilities as most likely.

 

weights.jpg.af35d152d77b4c616cb79f088f2f4a82.jpg

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Following Derek’s suggestion I contacted the mobile tyre fitting company (KwikFit) who immediately offered to send out a mobile unit to check the wheel balancing. Instead I requested that they ask the tyre fitter his opinion. He confirmed that (to his own surprise) two of the wheels when being checked for balance did not require weights. So I took the van for a focussed test run up to 70 mph (and maybe a little above) and is drives just fine with no discernable steering wheel judder. So confidence restored and case closed. I guess that the tyre fitting position completely compensating for hub unbalance must happen from time to time.
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It is a pity that the fitter did not communicate this to you at the time!

 

That the tyres are in natural balance speaks volumes for the quality of manufacture of the tyres and I hope they serve you long and well.

 

We always used to shield the tyres facing direct sunlight when the van was not in use but whether that contributed to a longer perish free u/v degradation life I know not - some say it does and some say it does not - but it cost nowt so we did it anyway!

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Some (but not all) new tyres carry markings to indicate the lightest point of the circumference and the point of greatest harmonic imbalance. Many tyre fitters ignore the markings to save time and for ease of fitting, finding it easier to add as much weight as necessary to balance the wheel and tyre, however out of balance it may have ended up after the two parts have been literally thrown together.

 

If a tyre fitter was to spend a little more time determining the imbalance of the wheel and orienting the tyre accordingly when mounting it to the rim, the application of weights necessary to achieve an acceptable balance could be substantially reduced, and it is not inconceivable that the necessity to apply weights could be avoided more often than where the two components are assembled randomly.

 

That's not something I would have associated with a Kwik Fit fitter though, albeit more from perceived reputation than totally non-existent experience, but who knows?

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Deneb - 2020-08-14 2:43 PM

 

Some (but not all) new tyres carry markings to indicate the lightest point of the circumference and the point of greatest harmonic imbalance. Many tyre fitters ignore the markings to save time and for ease of fitting, finding it easier to add as much weight as necessary to balance the wheel and tyre, however out of balance it may have ended up after the two parts have been literally thrown together.

 

If a tyre fitter was to spend a little more time determining the imbalance of the wheel and orienting the tyre accordingly when mounting it to the rim, the application of weights necessary to achieve an acceptable balance could be substantially reduced, and it is not inconceivable that the necessity to apply weights could be avoided more often than where the two components are assembled randomly.

 

That's not something I would have associated with a Kwik Fit fitter though, albeit more from perceived reputation than totally non-existent experience, but who knows?

 

Interesting point and now that you mention it I do recall some tyres used to have a red spot stamped on the sidewall to mark where the tyre should be located in relation to the valve for optimum balance - even though they still usually needed some lead to get them just right..

Not the DOT marking which is I was led to believe is/was the USA Dept Of Transprortation approval symbol?

I have not had to buy tyres for many years now so things may have changed?

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Deneb - 2020-08-14 2:43 PM

 

That's not something I would have associated with a Kwik Fit fitter though, albeit more from perceived reputation than totally non-existent experience, but who knows?

 

Besides the obvious hassle free convenience your point is one of the reasons I went for a mobile fitting. I rationalised that it was likely that only the experienced fitters would be tasked with working on their own out of a mobile van and of course they would be unambiguously accountable for any issues arising. My experience of in-store multi tyre changes has been that the tyre changes might be farmed out to two or three fitters any one of who might be recently qualified or maybe still an apprentice. What impressed me with this latest fitter was that he first wanted to verify the correct vehicle jacking points with me and then proceeded to check that there was no under floor habitation piping that might be fouled by the lifting equipment. I got the impression that he’d changed tyres on a few motorhomes before. It was a painfully hot day and these tyre fitters are not dressed for that sort of weather. He drank a pint and a half of water during the fitting. He did well in tough circumstances.

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Tracker - 2020-08-14 4:28 PM

 

Interesting point and now that you mention it I do recall some tyres used to have a red spot stamped on the sidewall to mark where the tyre should be located in relation to the valve for optimum balance - even though they still usually needed some lead to get them just right..

Not the DOT marking which is I was led to believe is/was the USA Dept Of Transprortation approval symbol?

I have not had to buy tyres for many years now so things may have changed?

 

Some still do. This was a Michelin Energy on my Volvo when new.

 

Yes, the DOT marking is a US requirement.

NDB6855526.jpg.4b9812fe84d8d17c28b8c98c477e3ff6.jpg

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BruceM - 2020-08-14 4:52 PM

 

Deneb - 2020-08-14 2:43 PM

 

That's not something I would have associated with a Kwik Fit fitter though, albeit more from perceived reputation than totally non-existent experience, but who knows?

 

Besides the obvious hassle free convenience your point is one of the reasons I went for a mobile fitting. I rationalised that it was likely that only the experienced fitters would be tasked with working on their own out of a mobile van and of course they would be unambiguously accountable for any issues arising. My experience of in-store multi tyre changes has been that the tyre changes might be farmed out to two or three fitters any one of who might be recently qualified or maybe still an apprentice. What impressed me with this latest fitter was that he first wanted to verify the correct vehicle jacking points with me and then proceeded to check that there was no under floor habitation piping that might be fouled by the lifting equipment. I got the impression that he’d changed tyres on a few motorhomes before. It was a painfully hot day and these tyre fitters are not dressed for that sort of weather. He drank a pint and a half of water during the fitting. He did well in tough circumstances.

 

When working full time and long hours I started using mobile fitters, the last 'mainstream' tyre fitting place I used was not a good experience, but nowadays with more time on my hands I get a price from blackcircles, then ask my local garage if they can get somewhere near the price, I'm happy to pay him a few quid more if necessary as I get good service from them.

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“Dot markings’ on tyres are explained here

 

https://blobs.continental-tires.com/www8/servlet/blob/554548/e3119edf9831c33103e5a771a0fe5717/download-coloured-dot-markings-data.pdf

 

and tyre balancing generally in this Wikipedia entry

 

https://en.wikipedia.org/wiki/Tire_balance

 

I’ve only experienced serious wheel-balancing problems on two of my vehicles after tyre replacement.

 

The first was with a VW Golf GTi in the 1980s and the front wheels were eventually brought into balance with the car raised on jacks and me ‘driving’ it at up to 100mph. Obviously, with hindsight, this should not have been necessary as, when fitted with the original tyres, the wheels were in balance. The equipment used then was designed to allow balance-weights to be fitted after the wheels had been put back on the vehicle and aimed a light beam at the tyre.

 

The 2nd event involved my first motorhome - a 1996-built Ford Transit-based Herald. All four tyres has been replaced and the wheels rebalanced, but it was obvious as soon as I drove the Herald quickly that the balance was badly wrong and a cursory inspection revealed that very heavy balace weights had been used. I immediately took the motorhome back to the tyre-fitting outlet and was told that the ‘hole’ in the centre of Transit wheels was sometimes not central and this complicated balancing. A Heath Robinson piece of kit was attached to the balancing machine so that a wheel could be held by bolts through its wheel-bolt holes (rather than via a ‘cone’ through the wheel’s centre) and balancing - with just small weights - was successfully performed.

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