Wheels

Wheel and Tyre Fitting Check List

Before fitting tyres on aftermarket wheels check:

1. that the stud/bolt hole pattern is correct. 2. that the wheel fits freely onto the hub without interference and that there are no screws, rivets or retaining clips which may interfere with a firm, flat location of the hub against the wheel mounting face. 3. that the wheel rotates freely and truly on both front and ear hubs

4. when fastened to the hub, that no part of the wheel can make contact with the brake drums or calipers or any other part of the steering or suspensionCheck nuts and bolts. Correct fitting is vital. Be sure1. that the thread form is correct (fit nuts without wheels).2. that the nut/bolt seating is correct.3. that the stud length is adequate for minimum thread penetration of approximately 1 x stud diameter and not too long as to permit "bottoming" of the stud in the nut.4. that the threads are rust free and not over-lubricated5. when sleeve nuts are used, that the shank diameter is correct and that the bearing washers are always used.When fitting the tyre

1. make sure that the rim size is compatible with tyre size. 2. be wary of scratching the protective lacquer coating (on aluminium wheels and some chrome wheels). Aluminium corrodes very easily once exposed to atmosphere, water or chemicals. 3. where possible always use the adhesive type of balance weight, as these help to avoid scratching of the wheel finish.

Finally Check

1. that the wheel and tyre assembly does not contact any part of the suspension or body work by carrying out full 'bump' and lock to lock tests before driving the vehicle away from the fitting bay.Do not take risks. Wheel security is vital. Check with experts if you have any doubt.

(Editorial supplied courtesy of Wheelwright Ltd)

Torqueing Nuts

If people give little consideration to their tyres, apart from price, then how much less attention do they give to their wheel nuts/bolts? Most people will just be happy if their wheel nuts are tight enough to keep the wheel on the car - and those nuts simple cannot be over-tight, can they?

Well, yes they can.

The issue of a loose wheel nut is pretty self- evident. If one wheel nut on a set is loose, then it puts additional strain on the remaining wheel nuts. Now, for some reason, that additional strain only very rarely causes a wheel nut to tighten itself.

It usually results in a loosening. For most drivers that becomes a very obvious danger as the loose wheel vibrating on the hub transmits that vibration and possibly impacts on handling and steering control, so the driver will usually identify a problem and have it fixed. 

With an over tight nut there is no evidence of a problem until things go wrong, and go wrong they can. 

The first problem with over tightening a wheel nut is that the chances are they will all be over tightened, so on a wet and windy night when you get a puncture you can't get the wheel off and you have to wait for the AA or the RAC or whoever to come and sort a flat tyre. A repair most folks could do in less than the time it takes the fitter to arrive. That though is a minor problem. 

The next issue is that when a nut tightens on a stud it can, if over tightened, stretch the stud. In itself not an issue, but the stretching of the stud weakens it. It is unlikely that it will weaken it below its breaking point, but repeated over tightening can do. The stud in the process work hardens and can shear.

If one goes, so too might a second; that increases the likelihood of a third or fourth coming off. If you think that unlikely, then consider that trucks from time to time lose wheels from trailers when all the studs shear at the same time!

Alloy wheels are not quite as forgiving as steel wheels, and over tightening the wheel nuts can cause damage to the wheel centres, creating stress points that can lead to fracturing at worst, damaged wheel nut facings at best.

If your car uses wheel bolts rather than nuts, then you still have the same issues, plus the over tightening of the hardened bolts in the hub may strip the threads or even crack the hub. 

Every tyre shop should have a reference chart to which they can refer for wheel torque settings. If the fitter runs the wheel nuts/bolts on with an air gun and hands you your car back, ask him to check the torque settings.

However, remember that if the air wrench has set the torque higher than it should be, using a torque wrench will not identify that the nuts are over tight.

Torqueing Nuts - The Trade Side

The issue of the correct torque settings for wheel nuts raises its head from time to time. One popular motoring magazine suggested that a majority of tyre depots did not correctly torque wheel nuts and that this created, at best, a nuisance for drivers, at worst a safety issue.

To be fair torque setting is not just an issue for the tyre trade: it is an issue throughout the motor trade and is exacerbated by the increasing use of air wrenches for every nut and bolt task. The issue is less one of training, but rather one of monitoring. Companies may train their staff all they wish, but at the end of the training many staff go back to their depots and carry on doing it the same old way. We have all been sitting in on training sessions and said, or heard said, "That's all very well in theory, but in practice..." 

Question?

How can the tyre trade improve its performance in this field, monitoring the effectiveness of the training, and ensuring that the lessons taught in the classroom are followed up in reality? That applies equally to jacking up cars, repairs, fitting, balancing as well as torque setting the wheel nuts.

It is worth noting that in the caravan sector many of the specialist service centres will mount wheels on the caravan and manually tighten the wheel nuts, but will not release the caravan to its owner until he/she has personally tightened the wheel nuts. Thus relieving the service centre of liability should the wheels then fall off! 

Is there a need for industry backed performance monitoring?

Mystery shoppers are all well and good, but if the customer doesn't know that the quality of the work being done is inadequate, how can he tell? How can the mystery shopper tell? If a nut is over-torqued by the air wrench in the first place, checking with a torque wrench afterwards will only give a minimum reading. The wheel nut could be 10-15-20 Nm over tight, checking with a torque wrench will not readily show that. 

Dave Smith, Chief Training Officer at Michelin's Stoke Training Centre agreed that it was his job to train to the highest standards in the classroom, but out in the field it becomes an operational management issue. Asked how checks could be run at depots he suggested that following the policy of one particular chain the fitter who mounted the wheels would set the torque and fit the wheels but the job had to be signed off by a senior technician or depot manager. 

James Bailey handled our enquiry at Hi-Q and he agreed that monitoring was difficult but added, " Hi-Q has a national policy of checking torque settings but always recommend that the motorist checks the wheel nut torque setting after a few hundred miles." 

On the truck-side Hi-Q use a Torque Right gauge to ensure that wheel nuts are tightened to the correct setting. It is something that could be looked at for the car market too. 

ATS Euromaster, as one might expect, train staff to the highest standards, but once again when the staff leave the classroom how do the standards get monitored? 

At the depots wheel nuts are run-on with an air wrench and the torque settings, taken from a wall chart guide, are set by torque wrench. It is policy at ATS Euromaster that the senior technician at the depot should check the torque setting of the wheel nuts on every vehicle before it leaves the depot.

However, in reality it may well be that this ideal is not always attained. There is though a further check in place. There are quarterly competency checks run by the depot managers on all staff in all areas of skill application. For truck fitters there is a specialist five day training course designed to ensure that they are fully competent in mounting tyres and wheels to commercial vehicles under all conditions. 

National told Tyres Online, "National Tyres and Autocare has strict procedures in place to ensure that any work carried out, including tyre fitting, is performed to the highest standard. Any branches or individuals identified as not following these procedures could face disciplinary proceedings." 

All the fast fit people we spoke to were adamant that they were doing their best to check settings. However, the one question that no-one could adequately answer was, if the settings are too tight, how can the supervisor be aware of this? Also, if the nuts have already been over-torqued by as much as 50 per cent the threads will already have been damaged and the studs stretched. Will the retailer then replace the studs and nuts free of charge? Will they offer redress for potential damage to alloy wheels? 

In any event, how does the client know what the correct torque setting for the wheel nut should be? It isn't in any owner's Hand Book Tyres Online has seen. One suggestion is that the torque setting for the wheel nuts should be displayed on a sticker on the door pillar alongside the tyre pressures guide. Then again, would that not just be another piece of information for the motorist or the mechanic to ignore?

There is no denying that this is a tricky question. It is also a wider subject than just wheel nuts. If the tyre trade can find a workable monitoring system to ensure that the correct standards are being met then it may well be taking a lead for other automotive servicing sectors to follow.