Tyres – Part three: Keeping a low profile
Gareth is back with his ongoing look at the challenges and opportunities represented by tyres. This month; tread
Published: 12 March, 2020
By Gareth Banks
In this third tyres instalment, I’m going to write about J sizes and fitting the correct tyre to the compatible wheel, as this caused a little headache for a friend of mine.
Recently he was complaining that his tyres kept losing pressure over the space of a few weeks. A few days passed and when he arrived I took one look at the stretched look tyres on his car, then rolled my eyes. I felt every small stone as I drove over it along the car park and into the workshop. He said all of the tyres were losing pressure, but the two on the nearside were the worst. After taking the nearside front wheel off and examining it a little closer, I could see that this one was leaking between the wheel and tyre, but why?
I took the rear one off the car too for a better inspection, as you can’t check for a rim leak correctly while the wheel is in an upright position. I found that this one too was leaking from around the wheel rim area but also from the inner sidewall. I explained that these tyres were s-t-r-e-t-c-h-e-d, and they were indeed! The tyre size was a 235/30/20 and the wheels had a 20x9J marking on the inside. The 20 tells you the wheel overall size in inches and the 9J essentially means J- passenger car type bead profile, and 9 meaning 9 inches from inner bead to outer bead -how wide the wheel is on the inside if you like. Yes, the tyres fit on the bead, but once inflated the tyre bead and sidewall of the tyre popped out into their rightful place to withstand the pressure. Obviously, the tread area cannot move in any way therefore giving the stretched look.
To cut a long story short I’d found that it was the front tyre bead that was leaking. It had been damaged when it was fitted and didn’t form a good enough seal when inflated. The tyre that was leaking from the sidewall had actually been driven ever so slightly low on pressure. This tyre had been taking the full brunt of any sort of impacts. As a result, my mate had unknowingly been slowly killing his tyres because of the aftermarket wheel/tyre combination he had chosen or indeed been sold. Even to the trained eye you wouldn’t tell that one of these tyres were low on pressure. After discovering that the tyres and wheels were all damaged due to the nice looking but terrible combination. Standard wheel and tyres have now been re-fitted.
Profile
The car may not have the same look as it did before, however it drives a heck of a lot better. The wheels aren’t getting battered on the tiniest of potholes and the tyres aren’t taking a hammering now. The moral of this story is that yes bigger wheels and smaller profile tyres do look good but aren’t very practical in our country with the state of our roads. Bigger isn’t always better. It is a given that these types of wheel and tyre combinations must be properly inspected if they seem to be losing pressure, as the alloy wheel could possibly even be cracked as this is the reason that the two other tyres kept deflating. It is not uncommon to see these types of wheels with a hairline crack on the inner side so please do be careful and inspect the wheel thoroughly before tyres are taken off as you don’t want any nasty surprises, or headaches for that matter.
- Ring backs TyreSafe
Ring has become a supporter of TyreSafe, the UK’s charity dedicated to raising awareness of the importance of correct tyre maintenance and the dangers of defective and illegal tyres. As a supporter, Ring will help spread the key messages of TyreSafe’s campaigns and support the charity in its ongoing awareness raising.
- Hunter Revolution WalkAway
Hunter’s fully-automatic Revolution WalkAway tyre changer offers 80 seconds of unattended bead breaking and demounting, meaning that technicians can perform other tasks such as wheel balancing while other tyres within a set are being demounted. Indeed, with the new WalkAway tyre changer, Hunter estimates that the process of changing and balancing a complete set of four identical wheels and tyres is 25% faster than traditional methods.The new Revolution WalkAway is ideal for workshops who are changing a large number of end-of-life tyres in sets of four or two of same size tyre and wheel assemblies.
- The shoe’s on the other foot
After my recent articles on tyres and TPMS systems, this month’s topic is wheel alignment, and the massive impact excessive toe-in or toe-out could have come MOT time.
A lot of us can spot alignment issues a mile off. I would worry if after 17 years in the trade, that a technician such as myself couldn’t tell the difference between a tyre that had been toeing-in and a tyre that had been toeing-out most of its life. If you look at a front tyre on a car and only the outer edge is bald (and the tyre has plenty of pressure in) then you walk around to the other side and discover the same issue with that tyre, it would be plain enough to see that the wheel geometry isn’t correct.
Compensate
A car with tyres like this and wheel alignment so far out must handle like it has a mind of its own - like Herbie the Beetle. However, people get used to a car in this state and will compensate to a surprising extent. When we take the car for a test drive, we may come back to the customer and say things like; “there maybe an issue with the tracking” or “the car is pulling rather a lot to one side.”
The customer then looks at us in amazement as if we are saying things just get their hard-earned money from them. We then offer a FREE wheel alignment check, and show them the virtual view on the screen. By Jove, the customer can then see with their own eyes exactly why their tyres have worn the way they have.
I first mentioned toe in and toe out. This is the way the wheels ‘point’ in relation to the forward motion of the car. Look down at your feet. Now keep your heels in position, and point your toes inwards so they point towards each other. If you try walking like this you will wear off the outside of your shoes first.
Do the same again with your heels, but point your toes outwards. This is toe-out and walking with excessive toe-out will wear the inner part of your nice new shoes and that’s the last thing you want. I’m sure you’d like it if your shoes wear evenly. The majority of track cars/race cars will be running with toe-out and negative camber. This will be topic of conversation next time as wheel geometry is a large subject.
Minutes and degrees
I also mentioned minutes and degrees earlier too. A while ago I tried explaining this to another tech and he struggled to grasp the concept of the theory behind alignment/ geometry, but he knew how to set the wheel alignment up on 99% of cars.
Getting your head around the actual maths is a different story. Think of it as a clock; there are 60 seconds in one minute; there are 60 minutes in one degree; and there are 360 degrees in a full turn. Our alignment set-up only works in minutes and degrees as it is really sensitive so no need for seconds-it would be worthless. The wind could blow and move the car slightly and that’s enough to make you panic and pick up your spanners again.
Once the alignment is set-up correctly and you’re happy with the end result, your customer will in turn be very happy. Remember, in the end they are the ones paying our wages, not just your boss. It does help if you have a happy boss too of course.
- MOT decision leaves 1 in 10 at ‘dangerous defects’ risk
The government is being accused of taking “a serious safety risk” by allowing millions of motorists to keep their cars on the road until January 2021 without a current MOT.
- Computer says “oh no” -Online car maintenance queries up 87% as lockdown eases
Garages may be able to pinpoint the kind of post-lockdown work coming through the door, with new research showing that online searches for how to tackle issues with car brakes, batteries and tyres have grown substantially over the last few months
